CN1702184A - Rolling member and producing method thereof - Google Patents

Abstract

A rolling member excellent in pitting strength, spalling strength and bending strength of dedendum has a first quench hardened layer which is formed on a surface layer of the rolling member and has a parent phase taking the form of martensite phase which forms a solid solution with carbon of 0.35 to 0.8 wt %, and a second quench hardened layer which is formed at a deeper layer under the first quench hardened layer and has a parent phase containing at least either one of martensite phase or bainite phase which forms a solid solution with carbon of 0.07 to 0.3 wt % and contains cementite dispersed therein in a content of 2 to 20% by volume.

Description

Revolving member and manufacture method thereof

Technical field

The present invention relates to employed revolving member and manufacture method thereof such as the gear part that needs wearability, anti-surface pressure intensity, high-fatigue strength, bearing components, camshaft member in building machinery etc.

Background technology

Be applied to the high-frequency quenching method of steel, usually, utilization is responded to the current flow heats postcooling that produces by the electric current of 1～400kHz frequency on the upper layer of applied parts, make the martensitic phase that forms hard on upper layer, is a kind of very widely used hard surfacing technology.This method is used for gear, axle class, bent axle, camshaft etc., needs the manufacturing of the parts of characteristics such as sliding, wearability, high strength.

In Figure 25, the high-frequency quenching mode of representing representative gear is (with reference to non-patent literature 1, p258).Wherein, from the viewpoint of productivity, carry out the primary quenching of the whole teeth shown in (a) mostly.In addition, as Figure 26 (a) shown in (b), as utilizing the high-frequency quenching method that forms laser quenching hardened layer along the heat input of profile of tooth, study and adopted double frequency high-frequency quenching method (with reference to non-patent literature 1, p258) and moment to give the high-power method of heating rapidly.

[non-patent literature 1] Japanese iron steel association compiles, and " Heat Treatment Of Steel ", (strain) ball is kind, clear and distribution on March 15th, 60

In the gear of a high-frequency quenching mode of the whole teeth of implementation shown in (a) of aforementioned Figure 25, because laser quenching hardened layer spreads all over whole tooth portion (through hardening), the stretching residual stress significantly takes place on the flank of tooth, the danger of losing of hardening crack and tooth is very high, exists the more problem of the gear of high loading that can not be used as.

In addition, in existing high-frequency quenching member, utilize with the carbon steel that contains 0.32～0.55 weight % quenching technology as main body.Further containing Ni, Cr, in the low alloy steel of alloying elements such as Mo, the hardening crack during owing to high-frequency quenching is very high, so, in order to utilize the lower steel of carbon concentration, compare its surface hardness deficiency with the gear behind the carburizing and quenching, for example, exist the problem (with reference to non-patent literature 1, p110, table 238, table 239) that can not fully satisfy to the requirement of anti-surface pressure, wearability, anti-burn property, high strength.

And then, in aforementioned formation shown in Figure 26 under the situation of the laser quenching hardened layer of profile of tooth, the deep of laser quenching hardened layer (for example, heat affected zone) becomes the preceding tissue that quenches, this tissue be a kind of soft (ferrite+cementite) tissue that is suitable for mechanical workout (usually, Vickers' hardness (Vickers hardness) is Hv160～260), compare with the hardness (Hv260～500) at the place, deep of the converted steel hardened layer of carburizing and quenching gear member, can not obtain enough hardness.Therefore, exist anti-depression intensity (anti-surface pressure), the insufficient problem of anti-spallation.In addition, owing on the end face of tooth portion, expose soft matrix part, so, exist the problem of undercapacity.

In addition, owing in the interface of high-frequency quenching hardened layer and matrix part, significant stretching residual stress takes place, so, exist the insufficient problem of spalling resistance of the flank of tooth.

Summary of the invention

The present invention considers above-mentioned situation, its objective is, the revolving member and the manufacture method thereof of a kind of anti-depression intensity, spalling resistance, tooth root flexural strength excellence is provided.

In order to solve above-mentioned problem, revolving member of the present invention, it is characterized in that, utilize the steel that contain C:0.4～1.5 weight % at least, described revolving member has following tissue, promptly forming two or more laser quenching hardened layers to inside center, in more than one the laser quenching hardened layer, be dispersed with the above cementite of 2 volume % therein from upper layer.

In addition,, it is characterized in that described member comprises according to revolving member of the present invention:

First laser quenching hardened layer, this first laser quenching hardened layer, with the austenite of the carbon of the concentration that solid solution had 0.35～0.8 weight % mutually sharply the martensitic phase that forms of cooling as parent phase,

Second laser quenching hardened layer, this second laser quenching hardened layer, be formed on than first laser quenching hardened layer darker the layer on, sharply the martensitic phase of cooling (C that for example contains 0.07～0.5 weight %) that form and bainite are dispersed with the cementite of 2～20 volume % mutually at least in the parent phase of one of them mutually with the austenite lower than the carbon concentration of the parent phase solid solution of first laser quenching hardened layer containing.

Manufacture method according to revolving member of the present invention is characterized in that, it comprises following operation:

Prepare the operation of steel as described below, described steel are, in the steel of C that contains 0.4～1.5 weight % and the Cr below the 2 weight %, adjust the alloy composition in the cementite, so that make alloy element concentration in the austenite that the Heating temperature of operation below forms, equate with alloy element concentration in the cementite in the described steel, and with respect to the carbon activity in the carbon concentration on the solid solubility line of this austenitic cementite, the austenitic carbon activity of forming than these steel is low

In the temperature range of the temperature range of Ac1 temperature～1150 ℃ or Ac3 temperature～1150 ℃, with two or more Heating temperatures, rapid refrigerative quenching process behind the aforementioned steel of upper layer induction heating.

In addition, in manufacture method according to revolving member of the present invention, prepare the operation of aforementioned steel, the steel that comprise the Cr of the C that will contain 0.4～1.5 weight % and 0.3～2 weight %, heat-treat the heat treatment step that contains Cr 3.5～12 weight % in the cementite that makes in aforementioned steel

Aforementioned quenching process, can be that the upper layer of the aforementioned steel high-temperature area at 900～1150 ℃ is being heated, and with aforementioned steel than the darker deep of aforementioned surfaces layer in Ac1 temperature～950 ℃ the low-temperature region heating or the low-temperature region in Ac3 temperature～950 ℃ heat, after carrying out above-mentioned two kinds of induction heating, rapid refrigerative operation.

In addition, in manufacture method according to revolving member of the present invention, aforementioned quenching process, also can be to be heated to after 900～1150 ℃ at upper layer with aforementioned steel, be cooled to temperature as the scope of the temperature of the scope of Ac1 temperature～950 of the temperature lower ℃ or Ac3 temperature～950 ℃ than this Heating temperature, remain on aforementioned temperature, aforementioned steel are heated to than after the darker deep of aforementioned surfaces layer, rapid refrigerative operation, perhaps, also can be that aforementioned steel are heated to temperature in the scope of Ac1 temperature～950 ℃, perhaps be heated to after the temperature of Ac3 temperature～950 ℃ scope, remain on aforementioned temperature, aforementioned steel are heated to the darker deep of specific surface layer, after the upper layer with aforementioned steel is heated to 900～1150 ℃ temperature of the temperature higher than Heating temperature, rapid refrigerative operation.

In addition, in manufacture method, prepare the operation of aforementioned steel, comprise heat treatment step according to revolving member of the present invention, so that make the Cr that contains 4～11 weight % in the cementite in the aforementioned steel,

Aforementioned quenching process can be after carrying out 2～1000 seconds of induction heating to aforementioned steel with the temperature in the scope of Ac1 temperature～950 ℃ and carry out 0.1～5 second induction heating in 900～1150 ℃ scope, sharply cooling.

According to the present invention described above, can provide the revolving member and the manufacture method thereof of anti-depression intensity, spalling resistance, tooth root flexural strength excellence.

Description of drawings

The cementite that Fig. 1 is to use the Fe-C-M equilibrium phase diagram and waits the carbon activity line chart is to the solid solution mechanism figure of γ in mutually.

Fig. 2 is the diagram of the homogenizing process of expression alloy element concentration different spherule when being present in the unlimited solid solution parent phase.

Fig. 3 is the diagram of homogenizing of the alloying element in the spheroidite of expression solid solution.

Fig. 4 is carbon activity line charts (in the time of 1000 ℃) such as Fe-C-Cr three component system

Fig. 5 is the diagram of the relation of Cr concentration in the cementite of expression when making Heating temperature be 750～1150 ℃ and the solid solution carbon concentration in the martensitic phase.

Fig. 6 is the diagram of solid solution condition (1) of the cementite in the Cr steel of expression 1 weight %.

Fig. 7 is the diagram of solid solution condition (2) of the cementite in the Cr steel of expression 1 weight %.

Fig. 8 (a) and (b) are synoptic diagram of organizing behind the high-frequency quenching of gear part of first kind of form of implementation, (c) are the synoptic diagram of high-frequency quenching (contour hardening) tissue of the gear part of prior art.

Fig. 9 is the representational high-frequency quenching mode chart in first kind of form of implementation of expression.

Figure 10 (a) and (b) are sectional views of example of the gear part of expression tape spool.

Figure 11 (a) and (b) are diagrams of the application examples of expression except that gear part.

Figure 12 represents the test film of roll extrusion depression test usefulness, (a) is the diagram of expression pony roll test film, (b) is the diagram of expression big roller test film.

Figure 13 (a) is the diagram of the relation of expression high-frequency quenching Heating temperature and quenching hardness, (b) is that (diagram of 6 ℃/sec) relation (c) is the diagram of the relation of expression ratio-frequency heating temperature and θ phase volume % for expression ratio-frequency heating temperature and martensite C concentration.

Figure 14 is the pilot study result's of expression roll-in depression intensity a diagram.

Figure 15 is the photo that the tissue of high-frequency quenching rapidly of No.4 material is handled in the expression balling.

Figure 16 (a) is the diagram of the relation of expression Heating temperature and quenching hardness, (b) is the diagram of the relation of expression Heating temperature and retained austenite amount.

Figure 17 is the photo of the tissue of high-frequency quenching rapidly of the expression No.4 sample that disperses perlite globular cementite and nodular cementite.

Figure 18 is the diagram of the high-frequency quenching Hardness Distribution of expression No.3 steel.

Figure 19 is the diagram of the comparison (300 ℃) of expression measured value of tempered-hardness and calculated value.

Figure 20 is the diagram of relation of the degree of depth of expression DI value and laser quenching hardened layer.

Figure 21 is the diagram of depth of hardening of the gear of expression modulus 3.25.

Figure 22 is the diagram of the necessary Hardness Distribution of spalling resistance of expression gear part.

Figure 23 is the diagram of the Hardness Distribution (m=3.5) of the anti-tooth root stress in bending of expression.

Figure 24 is the diagram of sclerosis pattern of the gear of expression high-frequency quenching.

Figure 25 is the diagram of the high-frequency quenching mode of the representational gear shown in the expression non-patent literature 1.

Figure 26 is the dual frequency heats figure of expression tooth portion.

Among the figure: 1 first laser quenching hardened layer, 2 second laser quenching hardened layers, tissue, 4 pitch circles, 5 centre of pitch circle positions before 3 quenchings, 6,7 axial regions, 8,9 tooth portions, 10 splines, 11 bearing components, 12 shaft components, 13 gear parts, 14,15 cams, 16 camshaft members.

Embodiment

This form of implementation, form with from upper layer to different martensitic phase of the carbon concentration of deep solid solution and bainite phase at least one of them as the two or more laser quenching hardened layer of parent phase.The revolving members such as gear part of anti-depression intensity, spalling resistance, tooth root flexural strength excellence can be provided whereby.

Revolving member according to this form of implementation, employing contains the C of 0.4～1.5 weight % and is respectively the steel of more than one alloying element among 2 weight % following Cr, Mn, V, Mo, the W, by aforementioned steel being carried out two or more quench treatment, form hardened layer with high-frequency quenching.This revolving member, at least on upper layer, form first laser quenching hardened layer, on the layer darker, form second laser quenching hardened layer than this first laser quenching hardened layer, between aforementioned first laser quenching hardened layer and aforementioned second laser quenching hardened layer, form the middle layer, aforementioned second laser quenching hardened layer is the central part tissue, perhaps, on darker than aforementioned second laser quenching hardened layer layer residual have organize before quenching.Aforementioned first laser quenching hardened layer, with the martensite of the concentration solid solution carbon of 0.35～0.8 weight % as parent phase.The parent phase of aforementioned second laser quenching hardened layer, constitute by the carbon concentration lower than the carbon concentration in the parent phase of first laser quenching hardened layer, contain with the martensite of the concentration solid solution carbon of 0.07～0.45 weight % and bainite mutually at least one of them, and then, in this second laser quenching hardened layer, be dispersed with the cementite of the not solid solution of 2～20 volume %, still, preferably, upper limit carbon concentration in this parent phase is 0.3 weight %, with martensitic stucture as main body.Aforementioned middle layer has the middle hardness of first laser quenching hardened layer and second laser quenching hardened layer.Tissue is that cementite is dispersed in the tissue in the ferrite before the aforementioned quenching.

In addition, in the present embodiment, preferably, in aforementioned steel, contain the Cr of 0.3～2 weight %, Cr is concentrated in the cementite of these steel, make the Cr that contains 3～12 weight % in the cementite.In addition, in aforementioned steel, can contain among the following S of (Si+Al), the 0.7 weight % of Mn, 0.05～1.5 weight % of 0.1～2 weight % following Mo, 1.4 weight % following W, 2 weight % following V, 1 weight % following Al, 3 weight % following Ni, 0.01 weight % following B, 1 weight % following (Ti+Nb+Zr), 1.0 weight % more than one.

In addition, for the such rotation member, preferably, adopt the steel of the Cr of the C contain 0.5～1.5 weight % at least and 0.5～2 weight %, in aforementioned first laser quenching hardened layer, be dispersed with the cementite of 2～17 volume %, in aforementioned second laser quenching hardened layer, be dispersed with the cementite of 4～20 volume %, in order further to improve wearability, preferably, utilization contains the steel of the Cr of the C of 0.7～1.5 weight % and 0.7～2 weight %, is dispersed with the cementite of 5～17 volume % in aforementioned first laser quenching hardened layer.

In addition, preferably, in aforementioned first laser quenching hardened layer, be dispersed with the retained austenite of 10～50 volume %.

And then, preferably, in aforementioned first laser quenching hardened layer, be dispersed with V ₄C ₃, among TiC, NbC, the ZrC more than one.

In addition, preferably, in aforementioned steel, contain (Si+Al) of 0.5～1.5 weight % and then contain among (Ti+Nb+Zr) of V, 0.1～0.5 weight of Mo, 0.2～1 weight % of Mn, 0.05～0.7 weight % of 0.1～2 weight % more than one.

Be applied at revolving member under the situation of gear part this form of implementation, preferably, aforementioned first hardening depth in the tooth portion pitch circle position of aforesaid gears member, be in module of gear (m (mm): in 0.15～0.6 times the scope pitch circle diameter ÷ number of teeth), on the layer or the tooth portion central position of aforesaid gears member, form the hardened layer that forms by aforementioned second quench treatment than Vickers' hardness Hv260～500 of organizing the higher hard of hardness before quenching than this first quench hardening layer depth.

In addition, be applied at revolving member under the situation of bearing components or camshaft member, preferably, on the upper layer of member, form aforementioned first laser quenching hardened layer at least this form of implementation, on the layer darker, form aforementioned second laser quenching hardened layer than this first laser quenching hardened layer.

And then, in the such rotation member, preferably, first laser quenching hardened layer or first laser quenching hardened layer and second laser quenching hardened layer carried out 100～350 ℃ temper.

And then, in the such rotation member, preferably,, carry out processing treatment such as shot peening at the surface element of first laser quenching hardened layer, on the surface element of aforementioned first laser quenching hardened layer, additional 50kgf/mm ²Above compressive residual stress.

Secondly, describe for manufacture method according to the revolving member of this form of implementation.

At first, prepare a kind of steel, described steel, at the C that contains 0.4～1.5 weight % at least with contain in the steel of more than one alloying element among the Cr, the Mn that are respectively below the 2 weight %, V, Mo, the W, adjust the alloy composition in the cementite, so that the alloy element concentration in the austenite that the Heating temperature of feasible operation below forms, equate with the alloy element concentration in the cementite in the described steel, and with respect to the carbon activity in the carbon concentration on the solid solubility line of this austenitic cementite, the austenitic carbon activity of forming than these steel is low.Secondly, in the temperature range of Ac1 temperature (eutectoid transformation temperature)～1150 ℃, perhaps in the temperature range of Ac3 temperature～1150 ℃, after aforementioned steel induction heating being adjusted from upper layer with two or more Heating temperatures, sharply cooling.Whereby, at least on the upper layer of aforementioned steel, can form first laser quenching hardened layer that the martensite parent phase with the concentration solid solution carbon of 0.35～0.8 weight % constitutes, on the layer darker than this first laser quenching hardened layer, form second laser quenching hardened layer, described second laser quenching hardened layer in one of them the parent phase at least that contains with the martensitic phase of the concentration solid solution carbon of 0.07～0.5 weight % and bainite phase, is dispersed with the cementite of the not solid solution of 2～20 volume %.

In the manufacture method of such rotation member, may further include the operation that the steel of the Cr of the C that will contain 0.4～1.5 weight % at least and 0.3～2 weight % are heat-treated, so that make in the cementite in these steel, contain the Cr of 3.5～12 weight % at least.In addition, also can the upper layer of the revolving member that will utilize aforementioned steel 900～1150 ℃ high-temperature area heating and will than in the darker deep of the upper layer of high-temperature area heating after the low-temperature region heating of the low-temperature region of Ac1 temperature (eutectoid transformation temperature)～950 ℃ or Ac3 temperature～950 ℃, carrying out two or more rapid induction heating, quench.Whereby, can adjust carbon concentration in the parent phase of aforementioned first laser quenching hardened layer and second laser quenching hardened layer.

In addition, aforementioned steel also can contain more than one among the following S of (Si+Al), the 0.7 weight % of Mn, 0.05～1.5 weight % of 0.1～2 weight % following Mo, 1.4 weight % following W, 2 weight % following V, 1 weight % following Al, 3 weight % following Ni, 0.01 weight % following B, 1 weight % following (Ti+Nb+Zr), 1.0 weight %.

Here, describe for induction heating adjustment and rapid refrigerative details to aforementioned two or more Heating temperature.Preferably, adopt following method, described method is, in order to form aforementioned first laser quenching hardened layer, sharply be heated to after 900～1150 ℃ at upper layer aforementioned steel, in order to form aforementioned second laser quenching hardened layer, be cooled to the temperature in the scope of temperature in Ac1 temperature (eutectoid the transformation temperature)～950 ℃ scope as the temperature lower or Ac3～950 ℃ than the temperature in aforementioned rapid when heating, keep aforementioned temperature, aforementioned steel are heated to after the darker position, sharply cool off.Perhaps, preferably, adopt following method, described method is, in order to form aforementioned second laser quenching hardened layer, aforementioned steel are heated to the temperature in the scope of Ac1 temperature～950 ℃, perhaps after the temperature in the scope of Ac3 temperature～950 ℃, keep aforementioned temperature, aforementioned steel are heated to darker position always, then, in order on the upper layer of aforementioned steel, to form aforementioned first laser quenching hardened layer, the upper layer of aforementioned steel is heated to after 900～1150 ℃ the temperature that likens to the high temperature of aforementioned Heating temperature, sharply cools off.

In addition, in this form of implementation, preferably, in aforementioned steel, at least contain the C of 0.5～1.5 weight % and the Cr of 0.5～2 weight %, in aforementioned first laser quenching hardened layer, be dispersed with the cementite of 2～17 volume %, the cementite that in aforementioned second laser quenching hardened layer, disperses 2～17 volume %, but, in order further to improve wearability, more preferably, utilization contains the steel of the Cr of the C of 0.7～1.5 weight % and 0.7～2 weight %, makes the cementite that is dispersed with 5～17 volume % in aforementioned first laser quenching hardened layer.

In addition, in this form of implementation, preferably, when utilizing aforementioned induction heating to quench, to reach from Ac1 temperature or Ac3 temperature quenching temperature T (℃) time time t (sec) adjust, make it to satisfy following formula (1).

t≤(1350/(T+273)) ²⁸…(1)

In this form of implementation, by carrying out Overheating Treatment so that contain the steel of the Cr of 4～11 weight % at least as the alloying element in the aforementioned cementite, temperature 2～1000 seconds of rapid induction heating in the scope of Ac1 temperature～950 ℃ and the rapid induction heating of the temperature in 900～1150 ℃ scope are after 0.1～5 second, quench, also can form aforementioned first laser quenching hardened layer and second laser quenching hardened layer.

And then, preferably, in aforementioned first laser quenching hardened layer and second laser quenching hardened layer, carry out 100～350 ℃ temper.

And then, preferably,, carry out processing treatment such as shot peening at the surface element of aforementioned first laser quenching hardened layer, give compressive residual stress.

According to above-mentioned form of implementation, forming different two or more of carbon concentration from the upper layer of revolving member to the deep is the laser quenching hardened layer of parent phase with the martensitic phase, first laser quenching hardened layer on upper layer, the Vickers' hardness Hv that becomes martensitic phase with the carbon of the concentration of solid solution 0.35～0.8 weight % and be parent phase is the quenched case of the hard more than 550.Thereby, can improve anti-surface pressure intensity (anti-pitting, anti-spallation), counter-bending fatigue strength, wearability etc.

In addition, in the deep darker than first laser quenching hardened layer, form second laser quenching hardened layer very darkly, this second laser quenching hardened layer, the martensitic phase of carbon of concentration of 0.07～0.3 weight % and bainite are arranged mutually at least in the parent phase of one of them comprising solid solution, be dispersed with the cementite of the not solid solution of 2～20 volume %.Thereby, can reduce in the prior art, with the incidental stretching residual stress of the interface of aforementioned first laser quenching hardened layer, improve the intensity of matrix part, can seek with respect to spallation etc. internally destruction and the improvement of transverse strength, simultaneously, can obtain to be used to give full play to the improvement of underlying strength of the function of first laser quenching hardened layer.In addition, by in aforementioned first laser quenching hardened layer, disperseing the hard cementite of 2～17 volume %, can obtain the improvement of more excellent wearability and anti-burn property.

Secondly, with reference to accompanying drawing, the concrete form of implementation according to revolving member of the present invention and manufacture method is described.

In revolving member according to this form of implementation, prepare to contain at least in the cementite in the C of 0.4～1.5 weight %, the tissue before quenching, concentrate the steel that alloying elements such as Cr, Mn, Mo, V are arranged quantitatively, utilization is suitable for the induction heating of heating rapidly, in the temperature range of the temperature range of Ac1 (eutectoid transformation temperature)～1150 ℃ or Ac3 temperature～1150 ℃, in two or more austenitizing Heating temperatures, aforementioned steel after upper layer is heated to the deep, are sharply cooled off.Whereby, form from the rotating surface course deep of revolving member with the laser quenching hardened layer of the different two or more martensitic phase of carbon concentration as parent phase, whereby, on the gear part that the soft steel (Hv160～260 usually) by the machinability excellence constitute, can add excellent anti-surface pressure intensity (anti-pitting, anti-spallation) and wearability, anti-burn property.

In more detail, with first laser quenching hardened layer on the upper layer of aforementioned steel, making with 0.35～0.8 weight % concentration solid solution has the quenched case of the martensite of C as the hard more than the Vickers' hardness Hv550 of parent phase.This first laser quenching hardened layer is being born the task of the improvement that improves aforementioned anti-surface pressure intensity, counter-bending fatigue strength, wearability etc.In addition, in the deep darker than this first laser quenching hardened layer, form second laser quenching hardened layer very darkly, this second laser quenching hardened layer, with the concentration solid solution of 0.07～0.3 weight % have the martensitic phase of carbon and bainite phase at least one of them as parent phase and be dispersed with the cementite of the not solid solution of 2～20 volume %.Whereby, reduce in the prior art and the incidental stretching residual stress of the interface of first laser quenching hardened layer, correspondingly, can improve the intensity of matrix part, consequently, can improve with respect to from the destruction of the inside of spallation etc. and the intensity of torsional bending stress, and then, can seek to give full play to the improvement of underlying strength of the function of aforementioned first laser quenching hardened layer.

In addition, because the hardness of first laser quenching hardened layer, reference decides more than the hardness of the rotation surface layer of the gear part of prior art is adjusted to Vickers' hardness Hv550, so, preferably, be solidly soluted into the concentration of the carbon in the martensite in this first laser quenching hardened layer, more than 0.35 weight %, in addition, more preferably, this solid solution carbon concentration is more than 0.4 weight %.

In addition, be solidly soluted into the upper limit concentration of the carbon in the martensite in first laser quenching hardened layer, consider the hardening crack when quenching, and, be set at 0.9 weight %, still with reference to the carbon concentration of carburizing and quenching gear member, when being 0.8 weight %, owing to be rich in toughness, so be preferred.

In addition, between first laser quenching hardened layer and second laser quenching hardened layer, form the middle layer of these each laser quenching hardened layers.In addition, in the additional few darker deep of second laser quenching hardened layer of specific tenacity, the tissue before the quenching that disperses cementite in ferrite can residually be arranged also.

In addition, as the alloying element that adds in the aforementioned steel, preferably, contain and be easy in cementite significantly to concentrate and reduce among the effect (character of the carbon in austenite and the mutual pulling of alloying element) of the carbon activity in the austenite of austenitizing strong Cr, Mn, Mo, V, the W more than one.In utilizing the steel of effective, the most more economical Cr of this effect as inevitable alloying element, at least contain the C of 0.4～1.5 weight % and the Cr of 0.3～2 weight %, and then, contain among (Si+Al), the 0.7 weight % of Mn, 0.05～1.5 weight % of 0.1～2 weight % following Mo, 2 weight % following V, 1 weight % following Al, 3 weight % following Ni, 0.01 weight % following B, the 1 weight % following (Ti+Nb+Zr) more than one, preferably, in the cementite in this steel, concentrate the Cr of 3～12 weight % at least.By utilizing this steel, the induction heating temperature when adjusting high-frequency quenching can be adjusted the carbon concentration of solid solution in the formed martensite.

And then on the plane of rotation of the revolving member that is accompanied by slip as the gear part, by disperseing the such hard carbide of a spot of cementite, the localized burn in the time of can improving anti-sliding stop is with anti-burn and wearability.So, in this form of implementation, in first laser quenching hardened layer, disperse the cementite of 2～17 volume %, improve wearability and anti-burn on the plane of rotation that is accompanied by slip.In addition,, be converted into the dispersion amount of cementite and the carbon concentration in the martensitic phase, preferably, make it to contain the C of 0.5～1.5 weight %, the Cr of 0.4～2 weight % as steel at this moment.In addition, as the alloy carbide of the hard that demonstrates same purpose with it, V ₄C ₃, TiC, NbC, ZrC etc. also be effective.Therefore, in this form of implementation, the V of less than 2 weight % scopes, (Ti+Nb+Zr) of less than 0.5 weight % scope be can add, preferably, the V of 0.2～1 weight % scope, (Ti+Nb+Zr) of 0.1～0.5 weight % scope added more economically.

In addition, making the residual of aforementioned cementite particle and alloy carbide, is effective for the miniaturization at the austenite crystalline particle of austenitizing state and the martensite plate that forms by quenching that causes by induction heating.In addition, with in the carbon steel, this austenitic crystalline particle more than 875 ℃, is easy to thickization below ASTMNo.7, and is relative therewith at high-frequency quenching, and in this form of implementation, miniaturization is to more than the ASTMNo.9.

And then, at the high-frequency quenching member is under the situation of gear part, owing to be necessary according to the stress distribution that is applied on the flank of tooth and the tooth root, in tooth portion, carry out Hardness Distribution, so, example with reference to the carburizing and quenching gear member, in this form of implementation, make the degree of depth of locational first laser quenching hardened layer of pitch circle of tooth portion, be in 0.15～0.6 times the scope of module of gear, on the tooth portion central position of deep darker or gear part than first laser quenching hardened layer, form second laser quenching hardened layer of Vickers' hardness Hv260～500, the carbon concentration that contains in martensite and the bainite parent phase one of in mutually in second laser quenching hardened layer is adjusted to 0.07～0.5 weight %, but, be more preferably with the parent phase of the aforementioned martensite of carbon concentration being adjusted to 0.07～0.3 weight as main body.

In addition, in the revolving member that under high surface pressure, uses, the hardness of its plane of rotation is hard, demonstrate excellent anti-depression intensity, but, in this case, exist owing to get involved the pollution of plane of rotation and the problem of the bad generation depression that causes of the running-in ability between the revolving member, in order to address this problem, it is effective disperseing retained austenite in right amount.Therefore, in this form of implementation, preferably, in first laser quenching hardened layer, disperse the retained austenite of 10～50 volume %.In addition, the reason of setting the higher limit of retained austenite amount for 50 volume % be because, when surpassing this higher limit, the hardness of plane of rotation descends, wearability can worsen.

In addition, in the gear part that under the situation of high surface pressure, heavily stressedization, uses, from the flexural strength that improves tooth root and anti-surface pressure intensity and then improve the viewpoint of the anti-torsional strength of axial region, preferably, on the surface element of laser quenching hardened layer, carry out processing treatment such as shot peening, on this surface element, additional big compressive residual stress.Thereby, in the revolving member of this form of implementation, preferably, carry out processing treatment such as shot peening.

In addition, owing to, can be inferred as 1/2 of compressive residual stress for the improvement effect of the compressive residual stress of the counter-bending fatigue strength of tooth root, so, in the revolving member of this form of implementation, preferably, additional 50kgf/mm ²Above compressive residual stress.

In addition, this form of implementation as previously described, by the rapid induction heating that utilizes two or more Heating temperatures to carry out, make and the austenite phase occurs, with correctly adjust be distributed in advance quench before solid solution capacity in austenite of cementite in the tissue time, by adjusting residual cementite (not solid solution cementite), form first laser quenching hardened layer and second laser quenching hardened layer.Study the result of this control method, mutually carbon activity of the austenite of the composition that equates with the alloy element concentration of cementite in the steel under the austenitizing Heating temperature of regulation (carbon activity on the solid solubility line of cementite in austenite (example is the K point among Fig. 1 as described later)), the carbon activity of the austenite phase formed than this steel of becoming (example is the H point among Fig. 1 as described later) the low moment rises, the solid solution of cementite is significantly slow, under the condition of the austenitizing of short period of time, be equivalent to comprise the cementite solid solution of amount of the solid solubility of cementite in austenite of alloying element, the carbon suitable with this amount, in the austenite that equals this solid solubility wait the carbon activity line (example as described later by K point among Fig. 1 and L order etc. the carbon activity line) on, in austenite, spread rapidly.Whereby, the alloy element concentration from this austenitizing temperature and cementite correctly determines the carbon concentration in the martensite parent phase in the layer that quenches.

Thereby, in this form of implementation, utilize the steel of adjusting cementite alloy composition in the steel in advance, preferably, its plane of rotation is carried out the austenitizing of two or more Heating temperatures, just as under the condition of the austenitizing of the temperature of two kinds of regulations of the scope of the temperature range of Ac1 temperature (the eutectoid transformation temperature of steel)～1150 ℃ or AC3 temperature～1150 ℃, for example, the stem surface layer is heated to after 1000 ℃, one side cooling one side is such in the situation of 800 ℃ of induction heating during to the deep.Whereby, be solidly soluted into the concentration of the carbon in the martensite in first laser quenching hardened layer of stem surface layer, become the concentration higher than the carbon concentration in the martensite that is solidly soluted in second laser quenching hardened layer, obtain more first laser quenching hardened layer of hard, simultaneously, in its deep, form second laser quenching hardened layer of low carbon concentration, high tenacity, consequently, can utilize the high-frequency quenching manufactured to have gear part with the similar Hardness Distribution of carburizing and quenching hardened layer.

Below, go through the solid solution mechanism (speed) of aforementioned cementite in austenite.In addition, as solid solution by the aforementioned cementite of delay, the carbon concentration (adjusting the residual quantity of cementite) that is adjusted at solid solution in the martensite is used alloying element, be necessary to add heating by in one of them individual two phase region of (ferrite+cementite) and (austenite+cementite), significantly be concentrated in the cementite, and Cr with effect of the activity that reduces the carbon of austenite in mutually, Mn, V, Mo, among the W more than one, particularly preferably be to add Cr, so, below, describe in detail by adding Cr or demonstrating the control method that has the alloying element of same purpose with Cr.

For example, 700 ℃ of abundant Cr concentration in the cementite in (ferrite+cementite) two phase region under the situations of heating, be concentrated to 28 times (, concentrating 52 times approximately) of the Cr concentration in the ferrite by 600 ℃ heating.Cementite after concentrating at this Cr or with the similar alloying element M of Cr, be accompanied by rapidly solid solution mechanism (speed) in the quench treatment of heating, the cementite in the austenite in the middle of heat-processed during solid solution, (M: alloying element) three component system cooperates the relation of the isoactivity line figure (waiting the carbon activity line chart) of phasor and carbon shown in this Fig to be illustrated to the Fe-C-M that can utilize in Heating temperature shown in Figure 1.

Fig. 1 schematically represent to add with the strong Cr of the avidity of carbon or with the Fe-C-M ternary alloy of the similar alloying element of Cr (for example, Cr, Mn, Mo, V, W etc.) equilibrium phase diagram at aforementioned induction heating temperature.In addition, the fine rule among Fig. 1 is to wait the carbon activity line.The austenite of forming with the steel shown in the A point of this Fig. 1 is the carbon activity that equates of the carbon activity in (γ phase) mutually, shown in the fine rule of ordering by the A among the figure, because by adding the M element, carbon activity reduces, so, the carbon isoactivity line is passed the top that take on the right side, and is crossing with the solid solubility line of cementite, and its intersection point (B point) connects into straight line with the composition point (C point) that contains the cementite of equilibrated M element.

Other isoactivity line (fine rule) among Fig. 1 calculates according to each carbon activity, and carbon concentration is high more, and carbon activity is big more, and still, the solid solubility of the graphite in Fe-C axle (Fe-C two component system) (D point) is defined as carbon activity Ac=1.

The ferrite in the tissue before quenching that the steel composition A that uses in earlier figures 1 is ordered and the composition of cementite, provide by E, F point, the cementite that F point when being heated to the temperature of quenching temperature is rapidly formed, locate residual alloying element M at this, having only the great carbon of diffustivity to be solidly soluted into cementite interface under the situation in the austenite rapidly and the carbon activity that G order is formed at the austenite interface of partial balancing, the carbon activity of ordering than the A of steel composition is big.Therefore, as can be seen, because the gradient of the partial potential of carbon, diffusion rapidly is on the solid solution position and original ferritic position of cementite, at first, in carbon (←, → number) along after, alloying element homogenizing by the A among the figure, isoactivity line homogenizing that B is ordered.

At first, discuss as previously described in the cementite that contains the alloying element carbon during solid solution, the diffusion process of alloying element rapidly, still, this discussion also can be used as the simple diffusion process of forming different spherules and handles approx.

Fig. 2 is the homogenizing process of the spherule for alloy element concentration cp, radius R 0 when being present in the unlimited solid parent phase that does not contain alloying element, calculate radial direction apart from the alloy element concentration c at r place.When this calculation result is applied to austenite mutually in the homogenizing process of the carbon of cementite of solid solution and alloying element M the time, carbon C, alloying element M be homogenizing desired heat-up time of t fully basically _C, t _M, be in the diffusion coefficient D of austenite in mutually according to the carbon C that causes by this Heating temperature and alloying element M ^γ _C, D ^γ _MThe diffusion length ((D that calculates ^γ _C* t _C) ^1/2, (D ^γ _M* t _M) ^1/2) become (△ among Fig. 2 number) inferring out approx with the mutually isochronous time of particle radii R of spheroidite, for example, at 900 ℃, the cementite of particle radii 0.2 μ m 0.1 second with interior solid solution, its carbon homogenizing basically, correspondingly, for the homogenizing of alloying element, need about 50 minutes (2835 seconds).In addition, diffusion length at aforementioned alloying element is 1/4 o'clock (900 ℃, the heating condition in 177 seconds) of particle radii, in Fig. 2 ◆ shown in number, because its diffustivity is little, alloying element is fully limited the periphery place of the solid solution vestige that is present in original cementite.

And then, similarly, obtain the diffusion that is equivalent to alloying element be limited to original cementite locational heating condition (among Fig. 2 ◆ number) each Heating temperature under heat-up time, its result represents with the thick solid line among Fig. 3, under rapid refrigerative situation behind this thick solid line scope internal heating, even after the quick solid solution of cementite, be concentrated in the alloying element homogenizing apace in the aforementioned cementite, but be confined to the periphery of cementite, so, for example, at the Mn of the hardenability that improves steel, Cr, Mo is confined under the situation at cementite vestige place of solid solution, as can be seen, the steel hardenability from this state greatly reduces.In addition, when the cementite particle radius is little during to 0.1 μ m, as shown in Figure 3, its heating condition scope becomes narrower, is necessary to be heated to rapidly quenching temperature.

In addition, inhomogeneous 1 the solid line of particle radii 0.1 μ m is used mathematical formula t approx _M=(1350/ (273+T)) ²⁸Expression, particle radii are inhomogeneous 2 the thick solid line of 0.2 μ m, the proximate mathematical formula t that uses _M=(1415/ (273+T)) ²⁸Expression, and then, aforementioned inhomogeneous time t _M(sec), with Heating temperature T (℃) and particle radii R (μ m) as variable, represent approx by following formula.

t _M＝((98.794×L _n(R)+1576.6)/(273+T)) ²⁸

In addition, as previously described, the diffustivity of carbon is very high, be about for 0.1 second 900 ℃ of heat-up times, just go up homogenizing basically, so, in the scope of the heating condition of Ac1 or Ac3 temperature～1150 ℃, even in the cementite of particle radii 1 μ m, by the heating in about 2 seconds, carbon can be apace along the A that passes through of earlier figures 1, the carbon activity line that waits that B is ordered spreads, do not make the residual effect in the martensite parent phase of cementite of not solid solution, the concentration that at this moment is solidly soluted into the carbon in the martensitic phase is by the A at the alloy composition of ordering by E, the carbon concentration that waits the carbon activity line that B is ordered provides, as can be seen, in most of the cases, be substantially equal to the carbon concentration of steel.

And then, according to Fig. 1, the solid solution mechanism of cementite is discussed, at alloying element addition in steel more (H points), there is more alloying element to be concentrated under the situation of (J point) in the cementite, because the rate of diffusion controlling mechanism of aforementioned carbon, alloying element remains in this place, cementite one is towards austenite solid solution rapidly mutually, one side arrives the K point in the austenite contain the alloying element that J orders, along the carbon activity line of ordering by K, carbon is diffused into the concentration that L is ordered rapidly, the become carbon activity of the composition of ordering than original H of K point is low, so, surpass the solid solution of its cementite, during the complete solid solution of cementite, do not light the diffusion of the alloying element of ordering to B along the solvus of cementite from K, cementite can not solid solution, and the solid solution of cementite is by the restriction of the velocity of diffusion of alloying element, and is significantly slack-off.

Thereby, the time that the complete solid solution of cementite is required, more than by the M concentration of element shown in the intersection points B, the concentration of the M element in the cementite is big more, become slow more, but, as previously described, because carbon spread along line such as carbon activity such as grade in the extremely short time, so the solid solution carbon concentration after the heating of this short time range in the rapid refrigerative martensitic phase is provided by the carbon concentration that waits the L on the carbon activity line to order of ordering by aforementioned K, the cementite solid solution that equates with this solid solution carbon concentration, the cementite of carbon amount of difference that obtains to equal carbon concentration in the steel and solid solution carbon concentration is with solid solution condition dispersive laser quenching hardened layer not.Thereby, in order to adjust the carbon concentration in the martensite, control quenching temperature (austenitizing temperature) and the Fe-C-M at this temperature place of portion are the M concentration (J point) in the cementite of equilibrium phase diagram, under the heating condition of can spread fully in the carbon one side, the cementite one side is residual, carry out the high-frequency quenching operation.

In addition, with the composition at the cementite solid solution position of the periphery of solid solution condition dispersive cementite not, become the composition that K is ordered among the figure basically, alloy element concentration at this position, significantly than L point, H point place height, carbon concentration also uprises, so, at the martensite start temperature Ms at this position point, further low temperatureization, at solid solution cementite periphery not, form the retained austenite phase of high tenacity, running-in ability excellence easily, this is preferred for the performance obdurability.

And then, M alloy element concentration (E point, I point) for the martensitic phase of Fig. 1, alloy element concentration after (ferrite+cementite) two phase region heat treated, following relational expression is set up, so, when the alloy element concentration [M weight %] obtained in advance in the cementite, the interpolation concentration M weight % by the M element of steel can calculate the alloy element concentration＜M weight % in the ferrite 〉.

M weight %=(1-f) *＜M weight % 〉+f * [M weight %]

F=C weight %/6.67

(here, f is the dispersion amount (volume %) of cementite, is that carbon solid solubility in the ferrite is little to can ignore the time, obtain approx.)

In addition, known, at two-phase structure's state of (cementite+ferrite), carry out the alloy element concentration＜M weight % in the alloy element concentration [M weight %] of each alloying element in cementite and the ferrite under the situation of heat treated of sufficiently long time ratio (partition ratio: α KM), it in alloying element inherent, take to depend on certain value of temperature, so, by using the partition ratio of various alloying elements, from the composition (with the allocation process temperature) of steel, can correctly calculate alloy element concentration in the ferrite by following formula.

α KM=[M weight %]/＜M weight % 〉

Thereby, as can be seen, when when being included in whole alloying elements in the steel and calculating alloying element in the ferrite, carbon concentration in the austenite of the austenitizing temperature of calculating when aforementioned quenching is heated, calculate hardenability (DI value), at least be equivalent to Fig. 1 in steel in the DI value of M alloy concentrations (A point, H point) compare, its DI value reduces.

In addition, under aforementioned cementite is solidly soluted into situation in the austenite rapidly, carbon concentration in the austenite becomes the carbon concentration that is substantially equal to steel, but alloying element is confined to the periphery of cementite solid solution vestige, because the alloy element concentration in the austenite at this moment, be similar to the ferritic alloy element concentration in the tissue before quenching, calculate its DI value, in this case, hardenability significantly reduces.

And then, make in processing under the situation of the residual austenitic hardenability of the cementite of not solid solution, owing to compare with the steel carbon concentration, the carbon concentration in the austenite is a lower concentration, so, be easy to reduce its DI value lower than the DI value of original steel.

And then, shown in this form of implementation, use the steel of adjusting the alloy element concentration in the over carburizing body, by selecting two or more austenitizing temperatures, adjust two or more carbon concentration and aforementioned alloy element concentration in the austenite, can adjust the hardenability of aforementioned first laser quenching hardened layer and second laser quenching hardened layer, in large gear, second laser quenching hardened layer that forms the deep darker than tooth portion is adjusted to the DI value of the regulation of using as parent phase with martensite or bainite in advance, is very important.In addition, as the method for adjusting this DI value, it can be compound interpolation concentrates alloying elements such as tendency more weak Mn, Mo, W in cementite method, but, as will be described, more preferably be, add Si, the Al, Ni, the Co that from cementite, are discharged from, are concentrated in the ferrite, improve hardenability.

For the solid solution mechanism of aforementioned cementite more specifically is discussed, below, use carbon activity line charts (at 1000 ℃) such as Fe-C-Cr three component system shown in Figure 4, the situation when being heated to 1000 ℃ of high-frequency quenchings that carry out quench treatment is rapidly discussed.

(1) the cementite situation of solid solution (the low situation of Cr concentration in the cementite) rapidly

With the point of the A among Fig. 4 (C of 0.8 weight %, 0.4 the steel weight %Cr), when 700 ℃ of abundant heating of (cementite+ferrite) coexisting region, become the composition of B point (cementite, 2.6 weight %Cr) and C point (ferrite, 0.09 weight %Cr), at this composition state, when by ratio-frequency heating, moment rapidly be heated to 1000 ℃ that become austenitic state the time, B point, C point become homogenizing along the direction of arrow to the A point.As previously described, alloying element in the cementite that B is ordered, almost be not diffused in the austenite during in, carbon have austenite (C point) that ferrite forms via the point of the D among the figure as ↑ ↓ number shown in, diffusion rapidly, after the solid solution carburizing, one side is accompanied by the diffusion of the Cr on the carbon activity line of ordering by A, and the Cr element is lentamente to A point homogenizing.In the moment that reaches the solid solution of cementite by ratio-frequency heating more rapidly, the carbon concentration in the martensite parent phase becomes and the identical carbon concentration of A point basically, can obtain the more martensite of high rigidity.In addition, the Cr concentration that is solidly soluted in carbon concentration in the martensitic phase of this form of implementation cementite when becoming 0.8 weight % is roughly 4.5 weight %, at least, by the Cr in the cementite being controlled at below the 4.5 weight %, cementite that can residual not solid solution.In addition, austenitic hardenability at this moment (DI value) by the alloy composition calculating of Fe-0.8 weight %C-0.09 weight %Cr, is compared with the DI value of steel (Fe-0.8 weight %C-0.4 weight %Cr), significantly reduces.

(2) situation 1 that postponed greatly of the solid solution of cementite

When with the point of the E among Fig. 4 (0.8 weight %C, 1 weight %Cr) steel shown in is when 700 ℃ of abundant heating in the zone of ferrite and cementite coexistence, become G point (ferrite, 0.24 weight %Cr) and F point (cementite, 6.61 composition weight %Cr), as previously described, under the situation by ratio-frequency heating instantaneously heating to 1000 ℃, at first, ferrite becomes austenitic state, simultaneously, as described in the example of front, the Cr concentration that F is ordered is along the identical line such as carbon activity such as grade that H is ordered that passes through, the part one side of cementite is according to the solid solution rapidly of carbon rate of diffusion controlling mechanism, and carbon simultaneously spreads.At this moment carbon along the aforementioned carbon activity line that waits in time that austenite spreads in mutually, in the homogenizing diffusion time of the cementite of aforementioned 900 ℃ particle radii 0.2 μ m, be about 0.1 second, when the uneven homogenize of considering alloying element shown in Figure 3 during the time, at least under the Heating temperature more than 900 ℃, in 1 second, the homogenizing of carbon finishes, because the carbon concentration in the martensite under the refrigerative situation in this state, determine by the Cr concentration in the cementite, so, carbon concentration in the martensitic phase after the quenching becomes about 0.5 weight % (being equivalent to control solid solution with the cementite of 7.5 volume % with the carbon rate of diffusion), in the martensite of unusual hard, approximately with disperse the to have an appointment cementite of 5 volume % of solid solution condition not.In addition, the austenitic hardenability (DI value) that is caused by this high-frequency quenching is calculated according to the composition of Fe-0.5 weight %C-0.24 weight %Cr, compares significantly reduction with the DI value of the steel (Fe-0.8 weight %C-1.0 weight %Cr) of homogenizing.

In addition, be heated to the carbon concentration of the residual austenite of 1000 ℃, refrigerative laser quenching hardened layer in mutually rapidly with 1000 ℃/sec at the SUJ3 that will describe later (the Cr concentration in the cementite is about 6.8 weight %), be 0.97 weight %, because the composition of the H point in 1000 ℃ of this carbon concentration and SUJ3 is consistent well, so, as can be seen, the solid solution mechanism by the cementite of aforementioned carbon rate of diffusion control is correct.And then shown in Figure 16 as described later, owing to the retained austenite phase that forms 10～45 volume % in 900 ℃ to 1100 ℃ quenching scope, also the solid solution mechanism of cementite is correct as can be seen.

Fig. 5 represents to make the Cr concentration in the cementite of Heating temperature in the time of 750～1150 ℃ and is solidly soluted into the relation of the carbon concentration in the martensitic phase.As can be seen from the figure, by adjusting Heating temperature, adjust be solidly soluted in the martensitic phase carbon concentration, as its result, correctly adjust the amount of dispersive cementite.In addition, for example, in case the stem surface layer short period of time of gear part is heated to after 1000 ℃, arrive darker deep 800 ℃ of ratio-frequency heating, quench then, in this case, form with by the martensite of the high carbon concentration of 1000 ℃ of heating decisions as first laser quenching hardened layer of parent phase and by in its deep by the low carbon concentration martensite of 800 ℃ of heating decisions second laser quenching hardened layers as parent phase.

In addition, the Cr concentration X in the cementite of the compositing range of the Cr of the C of 0.1～0.8 weight % of Fig. 5,0.5～15 weight % _CrΘ (weight %Cr) and martensitic solid solution carbon concentration X _C ^M(weight %) roughly described by following formula, with the record of the fine rule among the figure.

X _C ^M＝Aexp(B·X _CrΘ)

A＝0.0041(T+273)-3.3809

B＝0.000188(T+273)-0.426

Here, Heating temperature is T, this X _C ^MThe estimation error of (weight %) is about ± 0.05 weight %C.

In addition, top frame of broken lines shown in Fig. 5, be illustrated in the quench solid solution carbon concentration of the martensitic phase in first laser quenching hardened layer that obtains of short period of time in the Heating temperature scope of Ac1 temperature (725 ℃)～1150 ℃ heating back, the relation of the Cr concentration range in the cementite when becoming 0.35～0.8 weight %, for the Cr concentration range in the cementite of the carbon concentration in the aforementioned martensitic phase being adjusted to 0.35～0.8 weight %, be about 3～12.5 weight %.And then, change Heating temperature, by quenching temperature being adjusted to Ac1 temperature～1125 ℃, the solid solution carbon concentration that obtains martensitic phase is that the Cr concentration in the cementite of second laser quenching hardened layer of 0.07～0.3 weight % and first hardened layer is 3.5～12 weight %.More preferably, be set in 0.07～0.2 weight %, the martensite carbon concentration scope of first laser quenching hardened layer is set under the situation of 0.4～0.8 weight % in martensite carbon concentration scope second laser quenching hardened layer, Cr concentration in the cementite is set at 4～11 weight %.And then, forming under the condition of overhigh temperature of second laser quenching hardened layer, because distortion, the quenching crack susceptibility of gear part increase, so, preferably, the upper limit Heating temperature of this second laser quenching hardened layer is set in 950 ℃.In addition, be set at the ceiling temperature with first laser quenching hardened layer under 1100 ℃ the situation, preferably, making the upper limit Cr concentration in the cementite is 10 weight %.In addition, be under 750 ℃ the situation in the lower limit Heating temperature that makes second laser quenching hardened layer, preferably, the Cr least concentration that makes cementite is 4 weight %, under the situation of considering the quenching operation, preferably, the Cr concentration of cementite is set in 4～10 weight %,, selects 750～950 ℃ Heating temperature for the formation of second laser quenching hardened layer, for the formation of first laser quenching hardened layer, select 900～1100 ℃ Heating temperature.

And then, after the solid solution (cementites of about 7.5 volume %) of the cementite that aforementioned carbon rate of diffusion is controlled finishes, the carbon activity that the carbon activity that (under the situation of cementite solid solution and the cementite austenite interface that the relation of carbon activity such as has) located because H point in Fig. 4 is ordered than original E is low, so, the γ phase composite at cementite/austenite interface (H point) one side is accompanied by the diffusion of the Cr that the I on the solid solubility line of the cementite that concerns along the solid solubility alignment of cementite and activity such as the E point has orders, the cementite solid solution of 5 residual volume %, and martensitic solid solution carbon concentration increases.

(3) situation 2 that postponed widely of the solid solution of cementite

With identical by the solid solution carbon concentration in the carbon rate of diffusion controlling mechanism decision martensite of the cementite of aforementioned (2), still, as the mechanism that the residual cementite in (2) carries out solid solution by the diffusion of alloying element, the H point Cr different with cementite ₇C ₃Carbide is positioned at equilibrium region mutually with γ, still, supposition simply, in the solid solution process, nonequilibrium cementite is set up in the solid solution process of cementite with γ biphase equilibrium mutually.This supposition is based on such consideration, that is, in the solid solution process of this cementite, before cementite disappeared, process was because new Cr ₇C ₃Carbide forms the diffusion process of the complexity that causes, can not cause the reaction that needs free energy.In this case, discussing by there is no need to form new Cr ₇C ₃When the solid solution of the alloy diffusion rate-controlling of the cementite of carbide is machine-processed, owing to add that the γ phase composite of cementite/γ phase interface becomes at least at the Cr that can not separate out ₇C ₃Carbide (γ phase+cementite+Cr ₇C ₃) constraint condition formed of the K point in three-phase coexistence zone, so, can think that the solid solution meeting of cementite further postpones.

In addition, solid solution mechanism according to aforementioned (3), the stagnation point that significant solid solution postpones takes place in cementite, be under 1000 ℃ heating condition, Cr concentration in the cementite is concentrated to the situation of about 3.5 weight % when above, but, when 900 ℃ heating, be about 2.5 weight %, so, for example, in [Cr the concentration]=α KCr * steel in the steel of the Cr of C that will contain 0.4 weight % and the 0.3 weight % cementite during 700 ℃ of heating Cr concentration/(1-(carbon concentration in the steel/6.67) * (1-α KCr)) calculates is 3.2 weight %, so, the lower limit addition of Cr is roughly 0.3 weight %, preferably, and more than 0.5 weight %.

In addition, as in order to utilize the control of aforementioned carbon rate of diffusion to make solid solution cementite not stably disperse Cr concentration in the necessary cementite, 3.5～12 weight % are fit to, and preferably, are 4～10 weight %.And then the addition of the Cr in the steel that contains 1.5 weight %C is about 3 weight %, still, considers its economy, preferably, makes that its upper limit addition is 2 weight %.With reference to figure 5, by containing the steel that cementite, this cementite contain Cr3.5～12 weight % at least, in 750～1150 ℃ temperature range, in two or more austenitizing Heating temperatures, beginning to heat the back rapidly by induction heating from its stem surface layer quenches, can form two or more martensitic phases and become the laser quenching hardened layer of parent phase from upper layer to the deep.In addition, between the laser quenching hardened layer of adjacency, form the middle layer of transition.

Fig. 6 represents the solid solution model according to aforementioned (2), Fig. 7 represents the solid solution model according to aforementioned (3), the addition that makes Cr is 1 weight %Cr, the carbon addition is changed over 0.8 weight %C from 0.4 weight %C, 1.0 weight %C, by calculating, the Cr concentration in the cementite is adjusted to 11 weight % 700 ℃ of fully heating, 7, the steel of 5 weight % is when the heating of each quenching temperature, result that obtain the heat-up time of the complete solid solution of cementite of particle dia 0.4 μ m and SUJ2 (rate of heating: 6 ℃/sec) h and SUJ3 (rate of heating: 150 ℃/sec, 1000 ℃/sec) heating experimental result.Arrow among the figure is represented residual a large amount of cementite, for solid solution, needs the heating of longer time.

At first, the calculation result of comparison diagram 6 and Fig. 7, as can be seen, generally, the solid solution speed of the cementite that is caused by the mechanism of Fig. 6 is fast slightly, and is consistent well with the experimental result of the following rate of heating of 150 ℃/sec.In the calculation result of Fig. 6, with respect to the heating of passing through at 1050 ℃, Cr concentration in cementite does not arrive under the situation more than about 10 weight %, cementite is the result of solid solution hastily, for example, in being heated to 1100 ℃ SUJ3 1 second, cementite is residual significantly, consistent well with the calculation result of Fig. 7, as can be seen, under the condition of 150 ℃/ heating rapidly more than the sec, adopt the solid solution mechanism of Fig. 7 (model (3)) at least, in with this high-frequency quenching method that heats rapidly as prerequisite, cementite is easier to be residual.

Thereby, according to aforementioned result, be solidly soluted into carbon concentration in the martensite, make cementite remain in appropriate heating condition (heat-up time, Heating temperature) in the martensite as adjustment, carry out solid line in Fig. 7 (t (sec)=1400/ (T (℃)+273)) ²⁸) the temperature range of heat treated rapidly (850～1100 ℃) in the described time).When being compared by the speed of the rate of diffusion control diffusion in austenite with aforementioned carbon, as can be seen, the heat-up time of its upper limit is very long, by t heat-up time shown by the broken line in FIG. 7 (sec)=(1360/ (T (℃)+273)) ²⁸To carry out quench treatment under the interior condition, can correctly adjust the solid solution carbon concentration in the martensite and the amount of cementite.

And then, result according to Fig. 7, in order to form aforementioned first laser quenching hardened layer, for example import under the situation of heat along the profile of tooth of gear part, with the heat-up time of upper layer when Ac1 temperature or Ac3 temperature are heated to 900～1100 ℃ the austenitizing temperature of regulation rapidly, preferably in 2 seconds, for second laser quenching hardened layer being formed into the heat-up time that is heated to Ac1 temperature or Ac3 temperature～950 ℃ than the darker deep of first laser quenching hardened layer, preferably in 2～1000 seconds.

In addition, implementing under 150 ℃/ the situation about heating rapidly sec more than, the ferrite of tissue passes through piece type reverse transformation (phase transformation of ferrite → austenite phase) austenitizing hastily before quenching owing to be necessary to make, so, preferably, quenching temperature is set in more than the A3 temperature (about 900 ℃), sets the austenitizing Heating temperature that formation first laser quenching hardened layer is used for 900～1150 ℃.

Heat-up time in the actual heat treatment operation, should control, make distance in heating-up time from Ac1 or Ac3 temperature to quenching temperature and alloying element diffusion in the total time of hold-time of cooling beginning, be in by t (sec)=(1400/ (T (℃)+273)) ²⁸, or t (sec)=(1360/ (T (℃)+273)) ²⁸Within the diffusion length of the alloying element of the heat-up time that provides, but as previously described, can simplify.

In addition, according to the result of uneven diffusion time shown in Figure 3 of the result of Fig. 6 and Fig. 7 and front (situation during the cementite solid solution of particle radii 0.2 μ m), for example, carrying out 950 ℃: 10 seconds, 850 ℃: 100 seconds, 750 ℃: under the situation of 1000 seconds long-time heating, cementite is fully residual, continues significant uneven homogenize.Result with reference to figure 5, for example, can make the steel of the Cr concentration in the cementite of SUI2 being adjusted to 8.5 weight %, be heated to enough dark position after 100 seconds from upper layer at 850 ℃, and then upper layer is heated to after 1100 ℃ in 1 second, when quenching, otherwise and with upper layer in one side cooling one side after 1100 ℃ of heating under the situation of quenching after 800 ℃ of heating, be formed on carbon concentration be about 0.55 weight % martensitic phase in disperse first laser quenching hardened layer of the cementite of 7 volume %, and then, form carbon concentration in its deep and be about second laser quenching hardened layer that the martensitic phase of 0.2 weight % and bainite disperse the cementite of 12 volume % in mutually at least in one of them, and then, the high-frequency quenching member of tissue before there is quenching in the deep of second laser quenching hardened layer.

As by changing the revolving member that obtains from the degree of depth on the surface of quenching member in the heating of two kinds of such austenitizing temperatures, the aforesaid gears member is not only arranged, the gear part and the revolving member such as bearing that have axle in addition, and then, also have revolving members such as cam, camshaft, because to anti-surface pressure, anti-spallation, reverse and the reinforcement of stress in bending, so be preferred.In addition, as aforementioned austenitizing temperature, also can be two or more.

In addition, as the carbon concentration in the martensitic phase of aforementioned second laser quenching hardened layer, with reference to the example of carburized gears member, being preferably 0.1～0.3 weight %, more preferably is 0.1～0.25 weight %.In addition, from the viewpoint of boosting productivity, preferably, the austenitizing temperature that formation second laser quenching hardened layer is used is set at 800～900 ℃, and the Cr concentration in the cementite is set at 6～12 weight %.

The Cr that contains in the steel for mechanical structure more, Mn, Mo, V, W, Ni, Si, Al, it all is the element that improves hardenability, but, the same with aforementioned Cr, Mn, Mo, V, W concentrates in cementite, Ni, Si, Al is the alloying element that is discharged from from cementite, at the partition ratio α of 700 ℃ cementites and ferritic alloying element M KM (the M weight % in the M weight %/ferrite the in=cementite), α KCr:28, α KMn:10.5, α KV:9, α KMo:7.5, α KW:2, α KNi:0.34, α KCo:0.23, α KSi and α KAl: be 0, in addition, be at the partition ratio γ of 850 ℃ cementites and austenitic alloying element KM, γ KCr:7, γ KMn:2.1, γ KV:12, γ KMo:3.8, γ KCo:0.42, γ KNi:0.2, γ KSi and Al:0.Thereby, in at least one two phase region of cementite and austenite two phase region and cementite and austenitic two phase region, adjust under the situation of Cr concentration in the cementite, because Mn, the Mo of coexistence, V, W concentrate in cementite, so, in that the hardenability during in solid solution condition quench treatment not significantly reduces with cementite.And then, make not by what add that this Cr causes that the solid solution cementite disperses, adjust lowlyer with being solid-solubilized in the concentration of the carbon in the austenite and the concentration of alloying element, with the miniaturization of austenitic crystallization crystal grain, can reduce hardenability lower than carbon steel.

Secondly, the meaning to the interpolation of each element describes respectively.

Cr：

Cr, be a kind ofly in (ferrite+cementite) two phase region, to be concentrated in the most significantly in the cementite, in (austenite+cementite) two phase region, as previously described, also be concentrated in the cementite, simultaneously, in cementite in a large number solid solution up to the element of about 35 weight %, as previously described, because very strong with the avidity of carbon in the austenite, so, be a kind of element that shows the effect that the cementite of sening as an envoy to postpones to the solid solution of austenite in mutually significantly.In order to be in the martensitic phase of 0.35～0.8 weight % at the solid solution carbon concentration, disperse the above cementite of at least 2 volume %, preferably, for the steel of the C that contains 0.4～1.5 weight %, add the Cr of 0.3～2 weight %, the Cr concentration in the cementite is adjusted to 3.5～12 weight %, but, from by the aforementioned viewpoint that adds thermosetting second laser quenching hardened layer in advance, more preferably, the Cr concentration in the cementite is adjusted to 4～12 weight %.

Mn：

Mn is a kind ofly to play remarkable effect as the sulfide forming element, simultaneously by significantly improve the element of hardenability in the solid solution of austenite in mutually.In addition, Mn and V, Mo compares, it is a kind of element that in (ferrite+cementite) two phase region, significantly is concentrated in the cementite, but, in the interpolation scope of common steel, there is not existence at the alloy carbide of austenitic state, and, reduce the effect of the Mn of the carbon activity in the austenite, about below 1/2 of Cr, being solid-solubilized in about 8 weight % in cementite, do not demonstrate the solid solution delayed action of the cementite as aforementioned Cr, still, by coexisting with Cr, demonstrate the solid solution delayed action of the cementite that further promotion causes by Cr, in addition, owing to can improve the generation and the hardenability of the residual austenite phase that causes by aforementioned mechanism greatly, so, preferably, (0.1～2.0 weight %) according to circumstances adjusting in the interpolation scope of common steel.

In addition, passing through in the tooth portion below 4 with the whole heating of gear part (particularly with ratio-frequency heating with modulus, crown gear) in, by heating sharply cooling (quench treatment) of back, hardening crack takes place, in addition in through hardeningization easily, at laser quenching hardened layer significant stretching residual stress takes place, the intensity to this member gives ill effect mostly.Thereby, from avoiding the viewpoint of this through hardeningization, the steel that are not easy to obtain that are necessary to use the high-frequency quenching that will be included in aforementioned prior art to set lowlyer with the Mn in carbon steel and the low alloy steel.In this form of implementation, by forming in its deep with the martensitic phase of aforementioned low-carbon (LC) concentration second laser quenching hardened layer as parent phase, can avoid aforementioned through hardeningization, in addition, because Mn is concentrated in the cementite, have the aforementioned DI value of reduction, so, the upper limit addition that adds the Mn in the steel to 2.0 weight % can be brought up to, the acquired of steel can be improved.In addition, because Mn is remarkable element with austenite phase stabilization, so, adding under the situation with the alloying element of ferritic phase stabilization such as Si, Al, preferably, add the above Mn of 1 weight %.And then Mn is the element with the further low temperatureization of Al temperature, from reducing the viewpoint of the lower limit temperature that forms aforementioned second laser quenching hardened layer of the present invention, preferably, adds energetically.

Mo、W：

Mo is the same with Cr, is spissated element in cementite, and, be when improving hardenability, improve the element of the obdurability of quenching steel, so, in this form of implementation, be used, particularly, by adding the Mo (0.05 weight %) of trace, significantly postpone pearlitic transformation, be a kind of alloying element that demonstrates the effect of easy acquisition martensite and bainite structure, so, have the heart portion that prevents in the tooth portion of aforesaid gears member and separate out pearlitic effect.In addition, because the maximum solid solution degree of Mo in cementite is 2 weight %, under the situation of adding more Mo, separate out Fe ₃Mo ₃The alloy carbide of C etc., so, for example, in the steel of the C of C that contains 0.55 weight % and 1.5 weight %, can separate out Fe by the Mo of 0.4 weight %, interpolation more than the 0.7 weight %Mo ₃Mo ₃C is so preferably, the upper limit addition of Mo is 0.7 weight %.By the same delayed action of Cr of the solid solution mechanism (3) of the cementite of appearance and front more than the interpolation 0.4 weight %, considering under the situation of its economy like this, preferably, below 0.4 weight %.

In addition, because W shows the effect same basically with Mo, so the upper limit addition that in this form of implementation, makes (Mo+W) is 0.7 weight %.This is owing to consider the difference and the economy of proportion, adopts the upper limit addition of aforementioned Mo.(for example, the proportion of Mo be about W proportion 1/2, when the upper limit addition of aforementioned Mo is converted into W, become about 1.4 weight %, like this, comparing with Mo, under the considerably less situation of W, it is too much that the addition of Mo can become.)

V：

V is a kind of element that significantly is concentrated in the cementite, and is when because the maximum solid solution degree in cementite is 0.6 weight %, very little, so, in the steel of the C of the C that contains 0.55 weight %, 1.5 weight %,, can separate out V by adding 0.12 weight %, V more than the 0.2 weight % ₄C ₃Carbide is handled by aforementioned high-frequency quenching, and V is solidly soluted in the martensitic phase hardly, in addition, makes the solid solution speed of cementite significantly sluggish.In addition, minimum to the influence of hardenability, still,, preferably separate out V for wearability and the anti-burn property that improves the gear plane of rotation ₄C ₃Carbide, the V addition of reference tool steel makes that its higher limit is 2 weight %, but from mechanical Economics of Processing, more preferably is 0.2～1.0 weight %.

And then, by separating out V ₄C ₃Carbide by quench treatment, causes the miniaturization of old austenitic crystallization crystal grain, plays a part to improve obdurability and reduces hardenability, so V is a kind of preferred element that adds energetically.

In addition, when the induction heating high-frequency quenching is used carbon steel, 875 ℃ of Heating temperatures under the situation of the short period of time in several seconds heating, because old thickization of austenite crystallization crystal grain is to ASTM7 number, so, in this form of implementation, add the V of 0.1～2 weight %, arrive its miniaturization more than ASTM9 number, more preferably its miniaturization is arrived more than ASTM10 number, but in gear part, the raising of wearability, anti-burn property, anti-surface pressure intensity, improve the control of hardenability, the enforcement of close-toothed high frequency primary quenching is become to be easy to.

Nb, Ti, Zr etc.:

And then the alloying element as the miniaturization of the crystallization crystal grain that promotes to cause by aforementioned high-frequency quenching preferably, in the scope of 0.01～0.5 weight %, adds more than one of Nb, Ti, Zr.

B：

B, when adding 0.0003～0.01 weight % to, significantly postpone pearlitic transformation, significantly improve hardenability, in addition, for with the formation of the martensitic phase that is formed on the low carbon concentration in deep more from aforementioned upper layer as second laser quenching hardened layer of parent phase, be a kind of very preferred element, and and Mo same, prevent pearlitic separating out, coexist by Mo, play a part the bainite structureization of high tenacity with trace, so, for the steel that the high-frequency quenching of this form of implementation is handled, be a kind of preferred element.

Si、Al、Ni、Co：

Si, Al, Ni, Co are discharged from cementite, are concentrated in the martensite, and be still opposite with Cr, is a kind of alloying element that improves carbon activity.Particularly, Si is the element that significantly improves the carbon activity in the austenite and since have reduce be solid-solubilized in the carbon concentration in the aforementioned martensitic phase effect (for example, Δ C=0.1 weight %C/ weight %Si), so consequently, the effect that improves hardenability is slight.

In addition, because Si, Al is a kind of element that significantly improves in the temper softening resistibility of 100～400 ℃ low temperature side, so, be at revolving members such as various gears and bearings, the preferred alloying element that adds energetically in abrasion resistance member and the wear-resistant sliding component, add 0.05～2 weight %, but, heavy addition is significantly with the ferrite stabilization, the austenitizing treatment temp that second laser quenching hardened layer that forms aforementioned Ac temperature or Ac3 temperature～950 ℃ is used is increasing temperature more, mix ferritic phase easily, so the upper limit addition that makes (Si+Al) is 2.0 weight %.In addition, in the high-frequency quenching gear member of this form of implementation that in cementite, concentrates Mn, Cr, Mo, V etc., because the effect of Cr, the Mo of the temper softening resistibility of the martensitic phase of improvement plane of rotation, V is minimum, so, preferably, add 0.5 weight % above (Si+Al).And then, because Al is the element that more makes the ferrite stabilization than Si, so, set its upper limit addition for 1.0 weight %, but simultaneously, preferably, coexistence ground adds Ni, Mn, the Cu with stabilization of austenite.

In addition, Ni is the element that improves hardenability, also is simultaneously the element that improves obdurability.In the high-frequency quenching gear member of this form of implementation that in cementite, concentrates Mn, Cr, Mo, V etc., more second laser quenching hardened layer is formed into more deep owing to large-scale, be necessary to improve hardenability, so, add Ni more energetically, but preferably, the upper limit addition that makes Ni is 3 weight %.This is to consider that forming the retained austenite and the economy that form by aforementioned high-frequency quenching processing excessively sets.In addition,, further improve the temper softening resistibility, significantly improve toughness simultaneously by making aforementioned Al, Si coexistence.

Co is the alloying element that reduces hardenability, α KM enlarged functional with alloying elements such as making Cr, Mn, Mo, and, be a kind of effective element for the martensitic temper softening resistibility of remarkable improvement, still, because it is that price is high, so, in this form of implementation, preferably, add in the 3 weight %.

Cu is a kind of with stabilization of austenite, improves the element of weathering resistance simultaneously, so, consider the hot short generation easness when blank forging, preferably below 1 weight %.

In addition, N, P, S, O, exist as impurity in the common scope below 0.05 weight % respectively, under the situation of adding alloying elements such as Ti, Nb, Zr, V, Al, consider the nitride of dispersion based on these alloying elements, the concentration of N is adjusted to below the 0.3 weight %, in addition, adding under the situation of S, preferably, the concentration of S is adjusted to below the 0.5 weight % as easy machining steel.

Secondly, utilize the synoptic diagram of tooth portion quenching back tissue shown in Figure 8, first kind of form of implementation of the present invention described.In addition, Fig. 8 (a) is the synoptic diagram of organizing behind the high-frequency quenching according to the gear part of this form of implementation (b), and Fig. 8 (c) is the synoptic diagram of the high-frequency quenching along profile of tooth (contour hardening) tissue of prior art.

The gear part of this form of implementation, the steel of 3.5～12 weight % are adjusted to the Cr concentration in the cementite in utilization, by harden to Vickers' hardness Hv more than 600, constitute as first laser quenching hardened layer 1 of parent phase and second laser quenching hardened layer 2 that hardens to Hv300～500 with the martensitic phase of residual cementite not.Second laser quenching hardened layer 2, with martensitic phase and bainite mutually at least one of them as parent phase, the cementite before the residual quenching in the tissue.In addition, in the deep of second laser quenching hardened layer 2, the residual portion of (ferrite+cementite) two-phase structure that has as tissue 3 before quenching.

In addition, preferably, by for this module of gear (m), according to carbon concentration in the aforementioned martensitic phase and alloy element concentration, and the hardenability (DI value (in.)) of second laser quenching hardened layer 2 that calculates of the relation of old austinite grain size, to satisfy formula

DI≥0.12×m+0.2

Mode, control DI value, 5 places, tooth portion central position in the pitch circle position, form contain martensitic phase and bainite phase at least one of them as second laser quenching hardened layer 2 of parent phase.

In addition, be solidly soluted into the carbon concentration in the martensitic phase in aforementioned first laser quenching hardened layer 1, preferably, adjust to 0.4～0.8 weight %.In addition, be solidly soluted into the martensitic phase of aforementioned second laser quenching hardened layer 2 and bainite mutually at least the carbon concentration in one of them be 0.07～0.5 weight %, be preferably 0.07～0.3 weight %, the cementite of solid solution is not the nodular cementite below the median size 1 μ m.In addition, preferably, after quenching, carry out 100～350 ℃ appropriate temper.

When making the wheelwork of this form of implementation, use by the spheroidizing processing and the Q-tempering of cementite and handle, make spissated steel of Cr (steel hardness: Hv160～260) in the cementite at (ferrite+cementite) two phase region, for the blank of Gear Processing, heat-treat according to representational heat treatment mode shown in Figure 9 or the homophylic heat treatment mode that has on principle.(a) type shown in Figure 9, it is a kind of like this method, promptly, one side along profile of tooth with upper layer be heated on the upper layer of tooth portion form first laser quenching hardened layer 1 austenitizing temperature (1) afterwards, cool off, one side is forming the austenitizing temperature (2) that second laser quenching hardened layer is used in the deep of first laser quenching hardened layer 1, heat more after the deep, sharply cool off.In addition, (b) type is opposite with (a) type, be after a kind of austenitizing temperature of using at formation second laser quenching hardened layer (2) heats darker deep, on the upper layer of tooth portion, along profile of tooth, with upper layer be heated to rapidly form first laser quenching hardened layer, 1 usefulness austenitizing temperature (1) afterwards, rapid refrigerative method.In addition, (c) type is the preparation heating process that is provided with on (a) type.This preparation heating process is set, and is preferred for improving along the hot Introduced cases of profile of tooth, its Heating temperature, the preferably temperature province below the Ac1 temperature.In addition, (C-3) type shows, even after heating, cool off,, carry out heating and rapid cooling process to austenitizing temperature (2) by in other operation to austenitizing temperature (1), the thermal treatment of carrying out according to purport of the present invention also is possible, in addition, the heating unit to austenitizing temperature (2) can not hinder aforementioned induction heating, for example, can use heating units such as salt bath furnace.

In addition, make from the austenitizing temperature (1) of (a) appropriate to the speed of cooling of austenitizing temperature (2), perhaps, as (d) type, for the changes in hardness of the interface that makes first laser quenching hardened layer 1 and second laser quenching hardened layer 2 along cunningization, form the laser quenching hardened layer more than three kinds, owing to can approach the sclerosis pattern of carburizing and quenching gear, so be preferred.

In addition, austenitizing temperature (1) is 900～1150 ℃, austenitizing temperature (2) is preferred in the scope of Ac1 temperature or Ac3 temperature～950 ℃, this is with foregoing the same, but, in this form of implementation, as austenitizing temperature (1), the cementite before the selective quenching in the tissue all be solidly soluted into austenite (the residual carburizing scale of construction: temperature less than 2 volume %) basically.

In addition, as the mode along profile of tooth input heat, can implement aforementioned double frequency high-frequency quenching is the high-frequency quenching method that moment drops into high-power electric.

In addition, in this form of implementation,, preferably, disperse V in right amount from wearability that improves first laser quenching hardened layer and the viewpoint that resists burn property ₄C ₃, alloy carbide such as TiC.

And then, in this form of implementation, for not residual basically cementite in first laser quenching hardened layer 1, preferably, contain 0.4～0.8 weight %C, the Mn of 0.1～2 weight %, 0.3 the Cr of～2 weight %, and then, contain 0.05～1.5 weight % (Si+Al), 0.01 the Al of～1 weight %, 3.0 the Ni that weight % is following, the B that 0.01 weight % is following, the V that 2 weight % are following, more than one in 0.7 (Ti+Nb+Zr) below (Mo+W) that weight % is following, 0.2 weight %.

In addition, gear part in this form of implementation, the hardness of the surface portion of first laser quenching hardened layer 1 on the pitch circle 4 is more than the Hv:600, the degree of depth of its hardened layer 1 (more than the Hv513) is (0.2～0.6) * m (modulus), the hardness of the surface portion of first laser quenching hardened layer 1 of tooth root portion is more than the Hv:600, the degree of depth of its hardened layer 1 (more than the Hv513) is (0.15～0.6) * m (modulus), the hardness of second laser quenching hardened layer 2 is Hv300～500, preferably, centre of pitch circle position 5 forms second laser quenching hardened layer 2.

In addition, from improving counter-bending fatigue strength of tooth root and anti-surface pressure intensity, and then, improve the viewpoint of the anti-torsional strength of axial region and set out, preferably, carry out processing such as shot peening, at the additional 50kgf/mm of its surface element at the surface element of first laser quenching hardened layer 1 ²Above big compressive residual stress.

Secondly, second kind of form of implementation described.

In the gear part of this second kind of form of implementation, cementite before quenching by being dispersed in of residual dispersion 2～17 volume % in first laser quenching hardened layer 1 in aforementioned first kind of form of implementation in the tissue 3 can provide the anti-depression intensity of improving gear and the gear part of wearability.In addition, in second laser quenching hardened layer 2 that the deep of first laser quenching hardened layer 1 forms, also residual, as to disperse 3～20 volume % cementite.This gear part, the same with first kind of form of implementation, after the quenching, carry out 100～350 ℃ appropriate temper, the hardness of the surface portion of first laser quenching hardened layer 1 on the pitch circle 4 is more than the Hv:600, the degree of depth of this hardened layer 1 (more than the Hv513) is (0.2～0.6) * m (modulus), the hardness of the surface portion of first laser quenching hardened layer 1 of tooth root portion is more than the Hv:600, the degree of depth of this hardened layer 1 (more than the Hv513) is (0.15～0.6) * m (modulus), the hardness of second laser quenching hardened layer is Hv300～500, and it is preferred that centre of pitch circle position 5 forms second laser quenching hardened layer.

In addition, as employed steel, contain the C of 0.55～1.5 weight %, 0.1 the Mn of～2 weight %, the Cr of 0.3～2 weight %, and then, preferably, (Si+Al) that contains 0.05～1.5 weight %, the Al of 0.01～1 weight %, the Ni that 3.0 weight % are following, 0.01 the B that weight % is following, the V that 2 weight % are following, more than one in (Ti+Nb+Zr) below (Mo+W) that 0.7 weight % is following, 0.2 weight %.

And then by form the retained austenite of 10～50 volume % in first laser quenching hardened layer 1, additional toughness is preferably improved wearability, anti-burn property simultaneously, anti-surface pressure.In addition, when the residual Ovshinsky scale of construction surpasses 50 volume %, see the remollescent tendency on laser quenching hardened layer, wearability and anti-surface pressure intensity worsen.

In addition, carbon concentration from be solidly soluted into aforementioned martensite and alloy element concentration, and the relation of old austinite grain size hardenability that calculate, second laser quenching hardened layer 2 (DI value (in.)), by controlling in the mode that satisfies following formula

DI≥0.12×m+0.2

Preferably, the central position on the aforementioned pitch circle 5 form with martensitic phase and bainite mutually at least one of them as second laser quenching hardened layer 2 of parent phase.

The gear part of this form of implementation is made by handling with the high frequency heat of the same heat treatment mode of aforementioned first kind of form of implementation, but at the state that is heated to the austenitic temperature (1) that forms first laser quenching hardened layer 1, the cementite that residual 2 volume % are above.In addition, the same with aforementioned first kind of form of implementation, also can disperse V in right amount ₄C ₃, alloy carbide such as TiC.

In addition, in the gear part with axial region 6,7 (pinion(gear) class) of Figure 10 (a) shown in (b), the torsional stress and the stress in bending that are applied when being necessary with respect to torque have enough intensity, but, by the method shown in aforementioned first and second kind form of implementation being applied to the high-frequency quenching of these axial regions 6,7, can form darker quenching strengthening layer.Like this, the high-frequency quenching method of aforementioned first and second kind form of implementation is suitable as these high-frequency quenching methods that have the gear part of axle.In addition, in Figure 10, symbol 8,9 expression tooth portions, symbol 10 expression splines.

In addition, from the counter-bending fatigue strength that improves tooth root and anti-surface pressure intensity and then improve the viewpoint of the anti-torsional strength of axial region, preferably, on the surface element of first laser quenching hardened layer 1, carry out processing treatment such as shot peening, on its surface element, additional 50kgf/mm ²Above big compressive residual stress.

Below, the third form of implementation is described.

This third form of implementation, to be applied to cam 14,15 and the camshaft member 16 shown in shaft components 12 such as the bearing components 11 shown in Figure 11 (a), speed reduction unit trundle and gear part 13 and Figure 11 (b) in the manufacturing technology in the gear part of aforementioned first and second kind form of implementation.

Here, be necessary to have in the high-frequency quenching member of high temper softening resistibility, preferably, in the scope of 0.5～1.5 weight %, contain among Si, the Al more than one at gear, bearing, plumer block, axle etc.In addition, in working conditions, be attended by in the member of slip, preferably, disperse slightly to contain the V of 0.1～2.0 weight %, among the Ti more than one, based on the alloy carbide of V, Ti.

In this form of implementation, as required, preferably, the carbon concentration in the martensitic phase that will be solidly soluted into laser quenching hardened layer is adjusted in the martensitic phase in 0.35～0.8 weight % scope, disperses the cementite of 2～20 volume %.In addition, preferably, by forming the retained austenite of 10～50 volume %, making to improve wearability, to resist burn property, anti-surface pressure is the high-frequency quenching member of purpose.In addition, when the amount of retained austenite surpassed 50 volume %, laser quenching hardened layer had the remollescent tendency, and wearability and anti-surface pressure intensity worsen.

Under the situation of the cam of the hot crackability when being applied to pay attention to sliding etc., preferably, carbon concentration in the martensitic phase in the laser quenching hardened layer that is solidly soluted on the slipping plane is adjusted in the scope of 0.35～0.55 weight %, the cementite that disperses 5～20 volume %, and then, in order to improve wearability and anti-burn property, preferably, add the V of 0.1～2.0 weight %, disperse V in advance ₄C ₃Carbide.

In addition, from anti-surface pressure intensity, the wearability that improves gear part, the viewpoint that resists burn property, preferably, having in the martensite parent phase of carbon of 0.4～0.8 weight % in solid solution on the flank of tooth laser quenching hardened layer, disperseing the V of the scope of the cementite of 5～20 volumes and less than 5 volume % ₄C ₃, hard such as TiC alloy carbide.In addition, under the situation that has the alloy carbide more than the 5 volume %, have the destructiveness that the material that matches is caused and become significant dangerous.

[embodiment]

[embodiment 1; Anti-depression intensity (pilot study)]

In the present embodiment, in order to study the rotation fatigue strength that on the flank of tooth of gear, is accompanied by slip, utilize test film shown in Figure 12 to implement the test of roll extrusion depression, study the depression intensity of the steel that the case hardening of various Q-tempering carbon steels and carburizing and quenching handles.Table 1 expression is used for the various carbon steels of present embodiment, the chemical ingredients of steel that case hardening is handled, various steel are processed into after the shape of the pony roll test film 17 shown in Figure 12 (a), No.1,2,4, after 820 ℃ of heating 30 minutes, carry out shrend, carry out 3 hours temper at 160 ℃, be for experiment.In addition, No.3 and No.4, after blank is carried out modifier treatment, utilize the high frequency electric source of 40kHz, 200kW that plane of rotation is heated to 950 ℃ after quench hardening, carry out and same temper noted earlier.And then, No.5 930 ℃ carry out 5 hours carburizing treatment (carbon potential 0.8) after, be cooled to 850 ℃, 850 ℃ keep 3 hours after, in 60 ℃ quenching oil, quench, then, carry out and same temper noted earlier.

[table 1]

Be applied to the composition (weight %) of the steel of embodiment 1

	??C	??Si	??Mn	??Ni	??Cr	??Mo	Remarks
								??No.1	??0.55	??0.23	??0.71		??0	??0	??S55C
??No.2	??0.77	??0.21	??0.74		??0	??0	Eutectoid carbon steel (1)
								??No.3	??0.85	??0.22	??0.81		??0.43	??0	Eutectoid carbon steel (2)
??No.4	??0.98	??0.27	??0.48		??1.47		??SUJ2
								??No.5	??0.19	??0.22	??0.75	??0	??0.97	??0.15	??SCM420H

In addition, SUJ2 after the No.4 balling handled by ratio-frequency heating in the temperature province more than 800 ℃ with the slow intensification of the speed of 6 ℃/sec, after the predetermined heating temperature keeps about 5 seconds, carry out shrend, with the research hardness of quenched case at this moment and the result of the relation of the amount of carbon concentration in the martensitic phase that obtains of X-ray analysis and undissolved cementite, be shown in Figure 13 (a) and (b), (c).By this result as can be seen, by concentrated (Crs of about 7.8 weight %s) of Cr in cementite, the solid solution of cementite in austenite delays, in order to obtain the martensite (solid solution carbon concentration 0.35 weight %) with the equal enough hardness (more than the Hv650) of carburizing and quenching hardened layer, at least need Heating temperature is set in more than 900 ℃, Heating temperature is being brought up under 1000 ℃ the situation, as can be seen, the cementite of 8 volume % is so that solid solution condition is not residual.In addition, the high-frequency quenching temperature that makes No.3, No.4 be 950～980 ℃ carry out quench treatment after 160 ℃ of tempering 3 hours, residual cementite is 2 volume % in test film No.3, is 10 volume % in test film No.4.

Big roller test film 18 shown in Figure 12 (b) uses the SUJ2 material with No.4 to carry out shrend 820 ℃ of heating after 30 minutes, at 3 hours material of 160 ℃ of tempering.

The test of roll extrusion depression, pony roll test film 17 is fixed on the trier with two parallel turning axles in central shaft 21,22 modes consistent with two rotating shaft center with big roller test film 18, mode with the surface pressure that applies regulation makes 19,20 contacts of test face respectively, the mode of the test face of order 19,20 to advance to identical direction in the part of contact rotated with the rotating speed of regulation respectively with respect to central shaft 21,22.Here, one side is lubricated with 70 ℃ #30 engine oil, and simultaneously making the rotating speed of pony roll is 1050rpm, and the rotating speed of big roller (load roller) is 292rpm, and gives 40% sliding ratio, makes that surface pressure is 375～220kgf/mm ², under these conditions, implement the test of roll extrusion depression.

Figure 14 summary sheet is shown under the various surface pressures, and the multiplicity (revolve turn around as once pony roll) of depression takes place, and transverse axis is represented the multiplicity that caves in, and the longitudinal axis is illustrated in the surface pressure when carrying out this test.Express in the steel of handling as the case hardening of the carburizing of benchmark (NO.5) the life-span line that interrelates with minimum multiplicity under various surface pressures at first, in the drawings.Multiplicity when depression will take place is 10 ¹⁷Surface pressure when inferior is defined as under the situation of plane of rotation fatigue strength (anti-depression intensity), and as can be seen, its depression intensity is about 210kgf/mm ²In addition, when discussing with same adjustment method, No.1:175kgf/mm ², No.:240kgf/mm ², No.3 (high-frequency quenching): 260kgf/mm ², No.4:270kgf/mm ², and No.4 (high-frequency quenching): 290kgf/mm ², as can be seen,, disperse the plane of rotation fatigue strength of No.3, No.4 of the cementite particle of about 2 volume %, about 10 volume % significantly to improve by high-frequency quenching.And then, the steel that the case hardening of carburizing is handled, discreteness is bigger, its reason is because the amount of the existence of the grain boundary oxidation during carburizing and slack quenching layer and retained austenite is many etc. on plane of rotation causes, under situation about comparing with average depression frequency, as can be seen, the depression intensity of No.2 is constant.

In addition, the result of half-width of X ray of martensitic phase that the plane of rotation of depression takes place in research is, No.1:3.6～4.0 °, No.2:4～4.2 °, No.3:4.2～4.4 °, No.4:4.3～4.6 °, No.5:4～4.2 °.

And then, to the test film of carrying out aforementioned heat treated No.1～5 result of study in 3 hours X ray half-width of 250～350 ℃ of each tempering, half-width with the plane of rotation of aforementioned generation depression, with consistent 300 ℃ of tempered half-widths, as can be seen, with known document (for example, " material " the 26th volume, No. 280, p26) tempered-hardness of the carbon steel of the various carbon concentration of middle report and the relation of half-width are consistent basically.

In addition, from aforementioned result, as can be seen, disperse more than the 2 volume % in the martensite parent phase of solid solution carbon concentration more than 0.4 weight %, preferably the laser quenching hardened layer of the cementite particle more than the 6 volume % has excellent anti-surface pressure intensity, makes that cementite particle remains in bearing, spot contact bearing retainer, the shaft component and the high-frequency quenching method in the gear part of rotating mutually with bearing are good.

[embodiment 2: the affirmation of ratio-frequency heating condition]

Figure 13 (a) and (b) of embodiment 1, (c), expression, with the No.1 steel in the table 2 (material of SUJ2 that is equivalent to the No.4 of table 1), implementation was 810 ℃ of heating 2 hours, after Xu is as cold as 600 ℃ cementite spheroidizing and handles (Xu Lengfa), pass through ratio-frequency heating, rate of heating with 6 ℃/sec, be heated to after each temperature of 800～1050 ℃, carry out water quenching, study the hardness of its quenched case and the martensite that obtains by X-ray analysis in carbon concentration and the result of the relation of the amount of the not solid solution cementite that calculates by them.From these figure, as can be seen, for by Cr concentrating in cementite (Cr of about 7.8 weight %), acquisition is as the martensite of the necessary enough hardness of such rotation member and gear part, as previously described, preferably, be set in to major general's Heating temperature in 900～1100 ℃ the scope, at this moment the carbon concentration in the martensite is about 0.35～0.8 weight %, is necessary to disperse the hard cementite particle of 2～10 volume %.Depression intensity for the plane of rotation that improves gear part etc. preferably, is set at 0.4～0.8 weight % with the carbon concentration in the martensite of plane of rotation.As can be seen, when making the gear part of this form of implementation more excellent than the anti-depression intensity of carburized gears member, preferably, the hardness of the plane of rotation after 100～350 ℃ low-temperaturetemperings are handled is adjusted to more than the Hv650.

[table 2]

Be applied to the composition (weight %) of the steel of embodiment 2

	??C	??Si	??Mn	??Ni	??Cr	??Mo
							??No.1	??0.98	??0.27	??0.48		??1.47
??No.2	??0.98	??0.55	??1.11		??10.8
							??No.3	??0.58	??0.78	??0.37	??0.07	??1.00	??0.15

In addition, the dotted line among Figure 13 (b), the carbon concentration of solid solution in the martensitic phase that expression is obtained from aforementioned relation shown in Figure 5, consistent admirably with measured data below 950 ℃.In addition, as can be seen, at this austenitizing temperature more than temperature, the carbon concentration of solid solution is more in the actual martensitic phase of measuring.This is because the rate of heating of present embodiment is slow, solid solution by aforementioned alloy diffusion rate-controlling cementite, in order more correctly to be controlled at more than 950 ℃, preferably more than 900 ℃, carbon concentration in the martensitic phase that austenitizing forms, preferably, make the regulation that is warmed up to Ac1 temperature or Ac3 temperature to 900～1150 ℃ austenitizing temperature heating-up time and up to total time of hold-time of cooling beginning in 5 seconds, and then, in order to form aforementioned first laser quenching hardened layer along profile of tooth, preferably, 2 seconds with interior enforcement.

And then, preparation will reduce No.2 in the table 2 of the Cr addition steel that is for experiment and (be equivalent to the SUJ3 material, Cr in the cementite: about 6.5 weight %), carry out aforementioned balling and handle the material of (Xu Lengfa), and prepare after 820 ℃ keep 1.5 hours, to place cooling, the material that disperses perlite globular cementite and nodular cementite, to compare the 1000 ℃/sec of rate of heating that is exceedingly fast with common ratio-frequency heating speed, be heated to after each temperature of 900～1100 ℃, quench, study the tissue of its slipping plane.

Figure 15 represents the tissue that the austenitizing temperature from 1000 ℃ of the material of aforementioned balling processing (Xu Lengfa) quenches, the nodular cementite dispersion amount is extremely many, as shown in figure 16, hardness in its quenched case (1000 ℃), as can be seen, although contain the retained austenite of 30～45 volume %, significantly harden to maximum Hv880.In addition, when making austenitizing temperature be 1100 ℃, even contain the retained austenite of 50 volume %, harden to Hv830, wear resistance is no problem, can use.

In addition, Figure 17 represents to disperse the material of aforementioned perlite globular cementite (3.9 weight %Cr) and nodular cementite to be heated to 1000 ℃ of tissues of the slipping planes of quenching afterwards.As can be seen from this figure, the tabular cementite that in the martensite parent phase, disperses the pearlitic structure shape, and the hardness of its laser quenching hardened layer, as in the relation of figure Fig. 5 as can be seen, the carbon concentration that is solidly soluted in the martensitic phase significantly improves (C of 0.87 weight %), than the significantly sclerosis (Hv940) of hardness (Hv880) of the laser quenching hardened layer of Figure 15.

In addition, use contains the No.2 steel of the table of organizing before the perlite 2, research disperses the rate of heating of perlite globular cementite and the relation of Heating temperature, the result finds out, at 150 ℃/sec of rate of heating, in the quenching structure of Heating temperature 900, be dispersed with the perlite globular cementite, the hardness of laser quenching hardened layer at this moment, significantly harden to Hv945, in order stably to disperse perlite globular cementite at least about the Cr of 4 weight %, preferably, under with 850 ℃ of situations as the lower limit of Heating temperature, rate of heating 100 ℃/more than the sec, under 900 ℃ of situations as the lower limit of Heating temperature, rate of heating be 150 ℃/more than the sec.

Figure 18 represents, the No.3 steel of table 2 were carried out oil quenching at 950 ℃ * 1 hour after the homogenizing, after 700 ℃ of tempering 2 hours (the Cr concentration 9.8 weight % in the cementite), carry out ratio-frequency heating, quenching with foregoing coexist mutually 1000 ℃ and 1100 ℃ with 1000 ℃/sec, in the Hardness Distribution of 1 hour test film of 160 ℃ of tempering.With reference to earlier figures 5, as can be seen, by from 1000 ℃ quenching, the about less than 0.23 weight % of the carbon concentration of solid solution in martensite, fully sclerosis, at 1100 ℃, the carbon concentration of solid solution is brought up to about 0.35 weight % in the martensitic phase, obtains enough hardness.

In addition, the roll extrusion depression test-results the same with embodiment 1 is about 200kgf/mm in the depression intensity of 1000 ℃ of quenching products ², the anti-depression intensity of 1100 ℃ quenching product is about 240kgf/mm ²(with reference to Figure 14), the solid solution carbon concentration of the martensitic phase of the tissue of dispersion cementite particle is necessary more than 0.35 weight % in the martensitic phase, more preferably, more than 0.4 weight %.

And then, carbon concentration in the martensitic phase of obtaining according to the lattice parameter of the martensitic phase of the No.1 steel of heating quenching (balling treatment S UJ2) rapidly, be about 0.48 weight %, because it is consistent well with the concentration (0.46 weight %) of the carbon of solid solution in the martensitic phase that the Cr concentration (7.8 weight %) from the cementite of Fig. 5 is obtained, so, as can be seen, can adjust the carbon concentration of solid solution in the martensitic phase accurately by aforementioned heating rapidly.Similarly, the SUJ3 (the about 6.5 weight % of the Cr concentration in the cementite) that handles for the balling of No.4, also confirm, and, obtaining the carbon concentration of retained austenite in mutually is 0.97 weight %, can confirm that the carbon concentration of the austenite of the Cr concentration same composition of the cementite among its result and Fig. 4 in mutually about equally.Thus, be solidly soluted into the high-frequency induction heating condition of the carbon concentration in the martensitic phase, be preferably aforementioned Heating temperature as adjustment: 850～1100 ℃, rate of heating: 100 ℃/more than the sec.In addition, more adjust this solid solution carbon concentration in the highland, make that the lower limit Heating temperature is 900 ℃ (being roughly the A3 transformation temperature of Fe), 150 ℃/more than the sec, perhaps more preferably, in 2 seconds of heating between 900 ℃～1150 ℃ quenching temperatures, quench for precision.

In addition, in aforementioned about quenching temperature below 950 ℃, because the velocity of diffusion of alloying elements cr is slow, so, the influence of rate of heating is little, by high-frequency induction heating stably, can be easy to carry out the solid solution carbon concentration of martensitic phase, the not dispersion, the control of hardenability of solid solution cementite, and the miniaturization adjustment of old austenitic crystallization crystal grain.

Thereby, the revolving members such as gear part that form aforementioned first laser quenching hardened layer and second laser quenching hardened layer pass through, after fixed austenitizing heating (1) combination between the austenitizing heating (2) of the regulation between Ac1 temperature or Ac3 temperature～950 ℃ and 900～1150 ℃ implemented, carry out chilling and handle and make.For example

Type A: along profile of tooth with upper layer apace induction heating reduce induced electricity power to austenitizing temperature (1) afterwards, make it to cool to austenitizing temperature (2), sharply cooling is made, perhaps

Type B: by up to tooth portion inside is heated to austenitizing temperature (2) afterwards, along profile of tooth with upper layer promptly induction heating to austenitizing temperature (1) sharply cooling make.

In addition, in aforementioned type A, by adjusting from the cooling rate of austenitizing temperature (1) to austenitizing temperature (2), and then adjust carbon concentration in the martensitic phase from the middle layer of the aforementioned first quench hardening course, second laser quenching hardened layer continuously, and then, by the temperature distribution of austenitizing temperature (2), adjust martensitic phase in second laser quenching hardened layer and the bainite carbon concentration in one of them at least mutually to depth direction.

In addition, in aforementioned type B, be heated on the austenitic temperature (1), the temperature distribution by being formed on the mid-way of austenitizing temperature (2) forms aforementioned martensitic phase in the middle layer.

In addition, in order to form first laser quenching hardened layer along profile of tooth, preferably, to the shallow ferrite implementation induction heating rapidly of induced current depth of penetration, so when the various heat treating method of comparative type A and type B, type A is more preferred.And then, considered be heated to the austenitizing temperature of type B (2) afterwards, once be cooled to below the A1 temperature, after separating out ferrite, along profile of tooth promptly induction heating to the method for austenitic temperature (1), but, in this case, do not form the clear and definite laser quenching hardened layer second time in the deep of first laser quenching hardened layer, interface in first laser quenching hardened layer and matrix hardness, significant residual tensile stress taking place, can cause aforementioned surfaces pressure intensity (spalling resistance) to reduce, is not good quenching method.

And then, as the frequency of aforementioned induction heating, there is employing at the bottom of tooth, to spread all over crown, the situation of the appropriate frequency that can heat simultaneously basically, and the frequency that adopts the 1～10kHz and the 100～1000kHz of aforementioned dual frequency.

In addition, in aforementioned manufacture method,, be not limited to aforementioned induction heating as the type of heating of austenitizing temperature (2), the type of heating that utilizes salt bath furnace also is effective, for example, at rapid induction heating afterwards, promptly carry out the salt bath furnace dipping to austenitizing temperature (1), be heated to austenitizing temperature (2), perhaps, with after the salt bath furnace heating, with upper layer promptly induction heating to austenitizing temperature (1).But, from the viewpoint of productivity, utilize induction heating mode consistently manufacture be most preferred.

[embodiment 3: the affirmation of temper softening resistibility]

The alloy composition that table 3 expression is used in the present embodiment, research thermal treatment is after 950 ℃ of normalizing treatment, heat 30 minutes water-cooleds afterwards at 810～870 ℃, Rockwell (Rockwell) hardness HRC at 3 hours test film of 250,300,350 ℃ of tempering, and then, analyze of the influence of various alloying element additions to these hardness.

[table 3]

Be applied to the composition (weight %) of the steel of embodiment 3

??TPNo.	??C	??Si	??Al	??Mn	??Ni	??Cr	??Mo	??V	??B
										??No.6	??0.45	??1.45		??0.46		??1.49	??0.52	??0.14	??0.0018
??No.7	??0.49	??1.45		??0.46		??1.01	??1.03	??0.15	??0.0019
										??No.8	??0.47	??0.31		??0.46		??2.01	??1.03	??015	??0.0019
??No.9	??0.49	??0.29		??0.45		??1.5	??1.49	??0.23	??0.0019
										??No.10	??0.36	??1.77		??0.6		??0.62	??0.11		??0.0026
??No.11	??0.45	??0.95		??0.66	??0.01	??1.29	??0.5		??0.0029
										??No.12	??0.39	??0.93		??1.02	??0.08	??0.97	??0.95	??0.5
??No.13	??0.43	??0.26		??0.44		??1.01	??0.48		??0.001
										??No.14	??0.47	??0.25		??0.4		??1.01	??1.05		??0.0018
??No.15	??0.46	??1.5		??0.4		??1	??0.51		??0.002
										??No.16	??0.45	??0.24		??0.4		??1.02	??0.48	??0.31	??0.0011
??No.17	??0.45	??1.46		??0.39		??0.96	??0.98		??0.001
										??No.18	??0.41	??0.25		??0.35		??1	??0.49		??0.0017
??No.19	??0.52	??2.3		??0.57		??0.11
										??No.20	??0.98	??0.27		??0.48		??1.47
??No.21	??0.55	??0.23		??0.71
										??No.22	??0.77	??0.21		??0.74
??No.23	??0.45	??0.21	??1.26	??0.53		??1.51	??0.21
										??No.24	??0.6	??0.25	??0.97	??0.93	??0.98	??1.04	??0.35

In addition,, study for the carbon steel of the Mn of carbon that contains 0.1～1.0 weight % and 0.3～0.9 weight % as pilot study, in the analysis of the influence of aforementioned alloying element as master data.As can be seen, its result can represent with following institute approximate expression:

At 250 ℃,

At 300 ℃,

At 350 ℃,

In addition, as the basis, analyze the result of the influence of alloying element with the hardness of these carbon steels, as can be seen, temper softening resistance Δ HRC for example, at 300 ℃, can describe with following formula.

Δ HRC=4.3 * Si (weight %)+7.3 * Al (weight %)+1.2 * Cr (weight %) * (0.45 ÷ C (weight %))+1.5 * Mo (weight %)+3.1 * V (weight %)

Can find that from this result Al has 1.7 times the temper hardening resistibility of Si, be very effective as the improvement element of rotating surface pressure intensity.

Figure 19 represents the consistence of the tempered-hardness of the tempered-hardness obtained from aforementioned analytical results and actual measurement, as can be seen, can in the scope that its discreteness width is HRC ± 1, predict accurately, in addition, 300 ℃ tempered-hardness for the cementation zone (0.8 weight % carbon) of the SCM420 (NO.5) of embodiment 1, ☆ with Figure 19 represents, and is consistent well with calculated value.

[embodiment 4: the affirmation of high frequency quenching]

The alloying constituent of the steel that table 4 expression is used in the present embodiment.After will carrying out 950 ℃ normalizing treatment, be machined into the cylindrical test sheet of diameter 30mm length 100mm, material in 850～900 ℃ of heating water-cooled after 1 hour, and after water-cooled, carry out the material that tempering was handled in 5 hours at 650 ℃, utilize the high-frequency heating apparatus of 3kHz, make it to be in basically with 15 seconds at 870 ℃ and carry out water-cooled after the uniform heating state, obtain its quench hardening degree of depth.And then, the DI value 2 of in Figure 20, expressing the DI value 1 obtained from the chemical ingredients of table 4 and calculating from the martensitic chemical constitution that aforementioned 650 ℃ temper is calculated and the relation of the degree of depth of laser quenching hardened layer, as can be seen, by alloying element is concentrated in the cementite of organizing before the high-frequency quenching, hardenability when significantly reducing high-frequency quenching, and can correctly control.In addition, No.P6 in same figure, the rectilinearity from figure departs from greatly especially, at this moment because the cementite in the tissue is with residual about 10 volume % of solid solution condition not before quenching, in this cementite, contain a large amount of alloying elements, and because the carbon concentration in the martensite tails off, DI value 2 diminishes, and then, as can be seen, because the miniaturization of crystallization crystal grain, hardenability further reduces.

[table 4]

The steel that are applied to embodiment 4 are formed (weight %)

	??C	??Si	??Al	??Mn	??Ni	??Cr	??Mo
								??No.P1	??0.58	??0.21	??0.024	??0.28		??0.16	??0
??No.P2	??0.58	??0.11	??0.024	??0.28		??0.55	??0.12
								??No.P3	??0.55	??0.61	??0.018	??0.2		??0.19	??0
??No.p4	??0.7	??1.18	??0.019	??0.22		??0.31
								??No.P5	??0.61	??0.09	??0.51	??0.26	??0.51	??0.31
??No.P6	??0.98	??0.61	??0.02	??0.49	??0.03	??1.02
								??S55C	??0.54	??0.22	??0.015	??0.81		??0.12

Figure 21 represents, with the gear of modulus m=3.25 after 900 ℃ of all heating, can (4in to be equivalent to the spraying water refrigerative cooling ^-1) when cooling off, at the bottom of tooth (◇ number), the flank of tooth on the pitch circle (slogan), tooth root (△ number), the calculation result of the relation between the DI value (in) of the locational quench hardening degree of depth of crown (No. zero) and steel, as can be seen, (1) flank of tooth place on pitch circle, more than the DI=0.6 (in), through hardeningization, (2) up to through hardeningization, the quench hardening degree of depth of tooth root portion and crown portion, respectively about 30% of the quench hardening degree of depth on pitch circle, about more than 200%, with respect to the quench hardening degree of depth on crown portion and the pitch circle, have the tooth root portion quench hardening degree of depth shallow distinctive laser quenching hardened layer distribute, and, along with the crown hardening depth deepens more than the modulus m, from the flank of tooth near crown, near the flank of tooth the tooth root portion, the stretching residual stress takes place, and at tooth root, on the tooth lower surface, big compressive residual stress takes place.

In addition, the pitch circle position, the hardenability of the steel of through hardeningization (DI value) according to for the gear of modulus m2～15 (mm), to the result that aforementioned calculating is discussed, basically, must satisfy DI 〉=0.121 * m+0.2 condition.

Figure 22 represents, on the position of the pitch circle of the gear of m=3.5, effect has 240kgf/mm ²Hertz during surface pressure, the locational shear-stress of portion and tolerate the Vickers' hardness direction (Hv=10.9 * shear-stress) of the spalling resistance of this stress within it.In addition, Figure 23 represents that as a reference example on the root surface of same gear, effect has 100kgf/mm ²Stress in bending the time, locational stress distribution of portion and the Vickers' hardness that tolerates the fatigue strength of this stress distribute (Hv=6 * stress in bending) within it.In these figure, contrast ground expression, the Hardness Distribution of the gear part (with reference to Figure 24) of the profile of tooth high-frequency quenching of the Hardness Distribution of the carburizing and quenching gear of SCM420 material and the SUJ3 material (Hv=210) handled along balling.

At first, according to Figure 22 spalling resistance is discussed, preceding SUJ3 high-frequency quenching gear, compare with carburizing and quenching gear, because the hardness of its matrix (tissue before quenching) is low, a little less than the spalling resistance, in order to obtain the spalling resistance identical with carburizing and quenching gear, (1) degree of depth of its laser quenching hardened layer is deeply to 3～3.5mm (being equivalent to modulus), and (2) are necessary the hardness of matrix is for example hardened to about Hv350.As previously described, under the darker situation of the degree of depth that makes laser quenching hardened layer, the stretching residual stress can take place on the flank of tooth, making under the harder situation of matrix,, exist uneconomic problem from the angle of Gear Processing cost, so, by in the deep of aforementioned first laser quenching hardened layer, form second laser quenching hardened layer of the hard shown in a dotted line among the figure or the long and short dash line, be unusual ideal for addressing these problems.In addition, second laser quenching hardened layer that one long and short dash line is represented, based on bainite and pearlitic structure, as main body, second laser quenching hardened layer and carburized gears are same with one of them the tissue at least in martensite and the bainite for dotted line, more preferably, with martensitic phase and bainite mutually at least one of them as main body, in addition, in order fully to form this second laser quenching hardened layer, preferably, the DI value is adjusted to the condition that satisfies DI 〉=0.12 * m+0.2.In addition, in more large-scale processing member, more preferably,, be adjusted in cementite concentrated by adding Si, Al, Ni, Co.

In addition, in the high-frequency quenching gear of aforementioned SUJ3,40kgf/mm takes place on the flank of tooth ²Compressive residual stress, and in the interface of laser quenching hardened layer and matrix part, 20～30kgf/mm takes place ²The stretching residual stress, so, compare with carburizing and quenching gear, spalling resistance has the danger of further reduction.In the gear part of the present embodiment that forms first laser quenching hardened layer and second laser quenching hardened layer, owing to can reduce this stretching residual stress, so, can further improve spalling resistance.

In addition, preferably, the hardness of first laser quenching hardened layer and the degree of depth thereof, with the benchmark of the carburizing and quenching hardened layer of prior art (Hv:600～850, the degree of depth of hardened layer: (0.20～0.6) * m) be as the criterion, stipulated.

Secondly, discuss for the flexural strength of the tooth root of gear part according to Figure 23, with the result in the discussion of aforementioned spalling resistance is identical basically, the hardness of first laser quenching hardened layer and the degree of depth thereof, preferably, (Hv:600～850, hardening depth: (0.15～0.6) * m), the hardness of second laser quenching hardened layer becomes 300～500 at the benchmark of the laser quenching hardened layer of aforementioned carburizing and quenching gear.

[embodiment 5: the improvement of wearability]

Usually, because the wearability deficiency of high-frequency quenching revolving member, so, in the present embodiment, utilize the dispersion of cementite that the roll extrusion depression test of its wear-resistant sex previous embodiment is estimated.Roll extrusion depression test method, as previously described, the abrasion loss utilization is at surface pressure 250kgf/mm ²Condition under, 2 * 10 ⁶The wearing depth of the pony roll after the inferior test (μ m) is estimated.The employed steel that is for experiment, as shown in table 5, behind the high-frequency quenching, in table 5, represent the carburizing scale of construction, retained austenite amount and abrasion loss together, as can be seen,, can improve wearability significantly by the dispersion of cementite.In addition, in No.W3, compare with nodular cementite, during the breaker plate globular cementite, wearability is better in the pearlitic structure shape, this be because, by in the formation that is accompanied by the oil sac on the plane of rotation of slip, can improve lubrication state, this organizational form is not limited to gear part, also can be applied to the revolving member of bearing etc.

[table 5]

Be applied to the composition (weight %) of the steel of embodiment 5

	??C	??Si	??Al	??Mn	??Ni	??Cr	??Mo	Cementite volume %	Abrasion loss (μ m)	Retained austenite volume %
											??No.W1	??0.46	??0.22	??0.018	??0.76		??0.8		(1.2 granular)	??4.1	??12
??No.W2	??0.53	??0.21	??0.021	??0.78		??0.98	??0.16	(2.5 granular)	??2.3	??17
											??No.W3	??0.98	??0.55	??0.023	??1.11		??1.08		(5.8 granular)	??0.9	??35
??No.W3								(6.2 perlite)	??0.4	??28
											??No.W4	??0.84	??1.12	??0.019	??0.4		??0.91		(5.8 perlite)	??0.7	??33
??No.W5	??0.5	??0.88	??0.022	??0.75		??0.12		??0	??8.9	??7
											??S55C	??0.55	??0.23	??0.025	??0.71				??0	??12	??5
??S80C	??0.79	??0.22		??0.75		??0.13		??0	??7.3	??12
											SCM 420 carburizing and quenchings		??0.23	??0.024	??0.78		??1.01	??0.17	??0	??3.8	??23

Claims (26)

1, a kind of revolving member, it is characterized in that, utilize the steel that contain C:0.4～1.5 weight % at least, and has following tissue, promptly, form two or more laser quenching hardened layers from upper layer to inside center, be dispersed with the above cementite of 2 volume % therein in more than one the laser quenching hardened layer.

2, a kind of revolving member is characterized in that, comprising:

First laser quenching hardened layer, this first laser quenching hardened layer is formed on the top layer, and the martensitic phase of carbon that 0.35～0.8 weight % concentration is arranged with solid solution is as parent phase,

Second laser quenching hardened layer, this second laser quenching hardened layer be formed on than first laser quenching hardened layer darker the layer on, in the martensitic phase that has contained with 0.07～0.3 weight % concentration solid solution carbon and mutually at least one side's of bainite parent phase, be dispersed with the cementite of 2～20 volume %.

3, revolving member as claimed in claim 2 is characterized in that, further has to remain in than organizing in the darker layer of aforementioned second laser quenching hardened layer, be dispersed with the quenching of cementite in ferrite before.

4, revolving member as claimed in claim 2, it is characterized in that, further comprise the middle layer that is formed between aforementioned first laser quenching hardened layer and second laser quenching hardened layer, aforementioned middle layer has first laser quenching hardened layer and the intermediary hardness of laser quenching hardened layer for the second time.

As any one described revolving member in the claim 2 to 4, it is characterized in that 5, aforementioned first laser quenching hardened layer and aforementioned second laser quenching hardened layer form by high-frequency quenching.

As any one described revolving member in the claim 2 to 5, it is characterized in that 6, the such rotation member is made of the steel of C that contains 0.4～1.5 weight % at least and the Cr below the 2 weight %.

7, revolving member as claimed in claim 6, it is characterized in that aforementioned steel contain more than one among the following S of (Si+Al), the 0.7 weight % of Mn, 0.05～1.5 weight % of 0.1～2 weight % following Mo, 1.4 weight % following W, 2 weight % following V, 1 weight % following Al, 3 weight % following Ni, 0.01 weight % following B, 1 weight % following (Ti+Nb+Zr), 1.0 weight %.

8, as claim 6 or 7 described revolving members, it is characterized in that, in the aforementioned steel, contain the Cr of 0.3～2 weight %, contain the Cr of 3～12 weight % in the cementite in aforementioned steel.

9, as any one described revolving member in the claim 2 to 8, it is characterized in that, in the such rotation member, employing contains the steel of the Cr of the C of 0.5～1.5 weight % and 0.5～2 weight %, in aforementioned first laser quenching hardened layer, be dispersed with the cementite of 2～17 volume %, in aforementioned second laser quenching hardened layer, be dispersed with the cementite of 4～20 volume %.

10, as any one described revolving member in the claim 2 to 9, it is characterized in that, in aforementioned first laser quenching hardened layer, be dispersed with the retained austenite of 10～50 volume %.

11, as any one described revolving member in the claim 2 to 10, it is characterized in that, in aforementioned first laser quenching hardened layer, be dispersed with V ₄C ₃, among TiC, NbC and the ZrC more than one.

12, as any one described revolving member in the claim 6 to 10, it is characterized in that, in aforementioned steel, contain 0.5～1.5 weight % (Si+Al), and then contain among (Ti+Nb+Zr) of V, 0.1～0.5 weight % of Mo, 0.2～1 weight % of Mn, the 3 weight % of 0.1～2 weight % following Ni, 0.05～0.7 weight % more than one.

13, as any one described revolving member in the claim 2 to 12, it is characterized in that, the such rotation member is applicable to gear part, the degree of depth at locational aforementioned first laser quenching hardened layer of tooth portion pitch circle of aforesaid gears member, in 0.15～0.6 times scope of module of gear, on the layer or the tooth portion central position of aforesaid gears member, form aforementioned second laser quenching hardened layer of Vickers' hardness Hv260～500 than the aforementioned first quench hardening layer depth.

As any one described revolving member in the claim 2 to 12, it is characterized in that 14, the such rotation member is applicable to bearing components or camshaft member.

As any one described revolving member in the claim 2 to 14, it is characterized in that 15, aforementioned first laser quenching hardened layer or first laser quenching hardened layer and second laser quenching hardened layer carry out 100～350 ℃ temper.

16, as any one described revolving member in the claim 2 to 15, it is characterized in that, carry out processing treatment, at the additional 50kgf/mm of the surface element of aforementioned first laser quenching hardened layer at the surface element of aforementioned first laser quenching hardened layer ²Above compressive residual stress.

17, a kind of manufacture method of revolving member is characterized in that, comprises following operation:

Prepare the operation of steel as described below; Described steel are; In the steel of the C that contains at least 0.4～1.5 % by weight and the Cr below 2 % by weight; Adjusted the alloy composition in the cementite; So that so that the alloy element concentration in the austenite that forms of the heating-up temperature of operation below; Equate with the alloy element concentration in the cementite in the described steel; And with respect to the carbon activity in the concentration of carbon on the solid solubility line of this austenitic cementite; The austenitic carbon activity that forms than these steel is low

Quenching process, in the temperature range of the temperature range of Ac1 temperature～1150 ℃ or Ac3 temperature～1150 ℃, with two or more temperature, sharply cooling behind the aforementioned steel of upper layer induction heating.

18, revolving member manufacture method as claimed in claim 17, it is characterized in that aforementioned steel contain more than one among the following S of (Si+Al), the 0.7 weight % of Mn, 0.05～1.5 weight % of 0.1～2 weight % following Mo, 1.4 weight % following W, 2 weight % following V, 1 weight % following Al, 3 weight % following Ni, 0.01 weight % following B, 1 weight % following (Ti+Nb+Zr), 1.0 weight %.。

19, as claim 17 or 18 described revolving member manufacture method, it is characterized in that, prepare the operation of aforementioned steel, has the operation that the steel of the Cr of the C that contains 0.4～1.5 weight % and 0.3～2 weight % are heat-treated, make the Cr that contains 3.5～12 weight % in the cementite in the aforementioned steel

Aforementioned quenching process is an operation as described below, promptly, the upper layer of the aforementioned steel high-temperature area at 900～1150 ℃ is being heated, and with aforementioned steel than the darker deep of aforementioned surfaces layer in Ac1 temperature～950 ℃ the low-temperature region heating or the low-temperature region in Ac3 temperature～950 ℃ heat, after carrying out above-mentioned two kinds of induction heating, sharply cooling.

20, as any one described revolving member manufacture method in the claim 17 to 19, it is characterized in that, described quenching process is following operation, promptly, be heated to after 900～1150 ℃ at upper layer aforementioned steel, be cooled to temperature as the scope of the temperature of the scope of Ac1 temperature～950 of the temperature lower ℃ or Ac3 temperature～950 ℃ than this Heating temperature, heating or remain on aforementioned temperature, aforementioned steel are heated to than after the darker deep of aforementioned surfaces layer, rapid refrigerative operation, perhaps also can be that aforementioned steel are heated to after the temperature of temperature in the scope of Ac1 temperature～950 ℃ or Ac3 temperature～950 ℃ scope, remain on aforementioned temperature, aforementioned steel are heated to the darker deep of specific surface layer, after the upper layer with aforementioned steel is heated to 900～1150 ℃ temperature of the temperature higher than Heating temperature, rapid refrigerative operation.

21, as any one described revolving member manufacture method in the claim 17 to 20, it is characterized in that, in aforementioned quenching process from Ac1 temperature or Ac3 temperature arrive quenching temperature T (℃), formula below refrigerative time t (sec) satisfies,

t≤(1350/(T+273)) ²⁸。

22, as claim 17 or 18 described revolving member manufacture method, it is characterized in that, prepare the operation of aforementioned steel, comprise heat treatment step, so that make the Cr that contains 4～11 weight % in the cementite of aforementioned steel,

Aforementioned quenching process after aforementioned steel being carried out 2～1000 seconds of induction heating with the temperature in the scope of Ac1 temperature～950 ℃ and carry out 0.1～5 second induction heating in 900～1150 ℃ scope, is sharply cooled off.

23, as any one described revolving member manufacture method in the claim 17 to 22, it is characterized in that, utilize aforementioned quenching process, on the upper layer of aforementioned steel, formation has first laser quenching hardened layer of the martensitic phase of 0.35～0.8 weight % concentration carbon as parent phase with solid solution, simultaneously, on the darker layer of aforementioned first laser quenching hardened layer of the ratio of aforementioned steel, form martensitic phase that solid solution has 0.07～0.3 weight % concentration carbon and the bainite at least one side in mutually as parent phase, be dispersed with second laser quenching hardened layer of the cementite of 2～20 volume %.

24, the manufacture method of revolving member as claimed in claim 23 is characterized in that, in aforementioned steel, contains the C of 0.5～1.5 weight % and the Cr of 0.5～2 weight %, is dispersed with the cementite of 4～20 volume % in aforementioned second laser quenching hardened layer.

25, as the manufacture method of claim 23 or 24 described revolving members, it is characterized in that, after aforementioned quenching process, further comprise: the operation of aforementioned first laser quenching hardened layer and aforementioned second laser quenching hardened layer being carried out temper with 100～350 ℃ temperature.

26, as the manufacture method of any one described revolving member in the claim 17 to 25, it is characterized in that, after aforementioned quenching process, further comprise: carry out processing treatment, the operation of in aforementioned surfaces portion, giving compressive residual stress by surface element at aforementioned first laser quenching hardened layer.

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