CN112080697B

CN112080697B - Steel for clutch driven disc, preparation method of steel and clutch driven disc

Info

Publication number: CN112080697B
Application number: CN202010931856.6A
Authority: CN
Inventors: 杨业; 于浩淼; 许克好; 尼兴; 李春元; 蒋自武; 周娜; 李玉鹏
Original assignee: Beijing Shougang Co Ltd
Current assignee: Beijing Shougang Co Ltd
Priority date: 2020-09-08
Filing date: 2020-09-08
Publication date: 2021-09-17
Anticipated expiration: 2040-09-08
Also published as: CN112080697A

Abstract

The invention provides steel for a clutch driven plate, a preparation method of the steel and the clutch driven plate, wherein the steel for the clutch driven plate comprises the following chemical components in percentage by mass: c: 0.025-0.1%, Si is less than or equal to 0.05%, Mn: 0.18-0.3%, P is less than or equal to 0.02%, S is less than or equal to 0.015%, Ti: 0.01-0.02%, and the balance of Fe and inevitable impurities. The low-carbon component system is adopted, the cost is low, the surface hardness of the prepared clutch driven disc is 85-95 HRC, and brittle fracture problems occur in drop hammer experiments.

Description

Steel for clutch driven disc, preparation method of steel and clutch driven disc

Technical Field

The invention belongs to the technical field of steel rolling production, and particularly relates to steel for a clutch driven disc, a preparation method of the steel and the clutch driven disc.

Background

The clutch driven disc is a component of the automobile clutch, and transmits the torque of an engine to a transmission through friction conversion, so that the vibration and the impact of a transmission system are reduced, and the 'on' and 'off' tasks are completed. The clutch driven disc is mainly made of medium carbon steel in the earlier stage, in order to reduce cost, the clutch driven disc is made of low carbon steel instead of medium carbon steel, and meanwhile carbonitriding is carried out on a workpiece formed by stamping the low carbon steel in the heat treatment process, wherein methanol is used as heat treatment protective gas, methane is used for carburizing, ammonia is used for nitriding, and a box type multipurpose furnace is used for equipment. Through the N-penetration heat treatment, the surface of the workpiece has high hardness, high wear resistance and high corrosion resistance, and simultaneously has certain compressive stress, so that the fatigue property of the workpiece is improved.

However, the clutch driven disc is prepared by low-carbon steel at present, the brittle failure problem is easy to occur in a drop hammer test, and the use requirement is not met.

Disclosure of Invention

The invention provides steel for a clutch driven plate, a preparation method of the steel and the clutch driven plate, and aims to solve the technical problems that the clutch driven plate is easy to brittle fracture and does not meet the use requirement.

In a first aspect, an embodiment of the present invention provides a steel for a clutch driven plate, where the steel for a clutch driven plate is composed of the following chemical components by mass: c: 0.025-0.1%, Si is less than or equal to 0.05%, Mn: 0.18-0.3%, P is less than or equal to 0.02%, S is less than or equal to 0.015%, Ti: 0.01-0.02%, and the balance of Fe and inevitable impurities.

Further, the metallographic structure of the steel for the clutch driven disc is as follows by volume fraction: 95-99% of ferrite and 1-5% of pearlite.

Further, the thickness of the steel for the clutch driven plate is 3.5-7.0 mm.

In a second aspect, embodiments of the present invention provide a method for preparing a steel for a clutch driven plate, the method including,

obtaining a plate blank; the slab comprises the following chemical components in percentage by mass: c: 0.025-0.1%, Si is less than or equal to 0.05%, Mn: 0.18-0.3%, P is less than or equal to 0.02%, S is less than or equal to 0.015%, Ti: 0.01-0.02% of Fe and inevitable impurities as the rest;

heating, rough rolling, finish rolling and coiling the plate blank to obtain the steel for the clutch driven plate; the heating temperature is 1180-1220 ℃, the rough rolling is R1 single-pass rolling and R25-pass reversible rolling, the R1 inlet temperature of the rough rolling is 1130-1180 ℃, the finish rolling inlet temperature is 950-1100 ℃, the finish rolling outlet temperature is 850-890 ℃, and the coiling temperature is 580-640 ℃.

In a third aspect, the embodiment of the invention also provides a clutch driven plate, which is prepared by pickling, stamping deformation, annealing, quenching and tempering the steel for the clutch driven plate;

in the annealing process, the steel for the clutch driven disc after the stamping deformation is sequentially subjected to primary heating, secondary heating and tertiary heating, wherein the temperature of the primary heating is 700-750 ℃, and the heat preservation time of the primary heating is 10-20 min.

Further, the temperature of the second heating is 820-830 ℃, the heat preservation time of the second heating is 120-130 min, the temperature of the third heating is 840-850 ℃, and the heat preservation time of the third heating is 1-3 min.

Further, in the second heating process and the third heating process, carbonitriding is carried out, wherein the carbonitriding is carried out by adopting methane and ammonia gas, and in the carbonitriding, the temperature is 750-850 ℃, the carbon potential is 0.1-0.12%, the volume concentration of the ammonia gas is 0.25-0.5%, and the time is 120-130 min.

Further, the quenching is oil quenching, the cooling rate of the quenching is 97-105 ℃/s, the quenching starting temperature is 845-855 ℃, and the quenching finishing temperature is 85-95 ℃.

Further, the tempering temperature is 300-350 ℃.

Furthermore, the metallographic structure of the clutch driven disc comprises martensite, bainite, ferrite and pearlite, the volume fraction of the martensite is 80-90%, the volume fraction of the bainite is 5-15%, and the total volume fraction of the ferrite and the pearlite is 2-5%.

One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

the embodiment of the invention provides steel for a clutch driven disc, a preparation method of the steel and the clutch driven disc, wherein the steel for the clutch driven disc comprises the following chemical components in percentage by mass: c: 0.025-0.1%, Si is less than or equal to 0.05%, Mn: 0.18-0.3%, P is less than or equal to 0.02%, S is less than or equal to 0.015%, Ti: 0.01-0.02%, and the balance of Fe and inevitable impurities. Ti element is added in the component design, so that the structure grain boundary of a deformation part is pinned in the annealing process, the structure of the material is prevented from coarsening and growing, and the brittle failure problem is avoided. The low-carbon component system is adopted, the cost is low, the surface hardness of the prepared clutch driven disc is 85-95 HRC, and brittle fracture problems occur in drop hammer experiments.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.

FIG. 1 shows a fracture macro-morphology of a drop hammer test of a clutch driven plate prepared according to an embodiment of the invention;

FIG. 2 is the micro-topography of FIG. 1;

FIG. 3 is a carburized thickness microstructure of a clutch driven plate made in accordance with an embodiment of the present invention;

fig. 4 is a subcutaneous metallographic structure of the clutch driven plate prepared in comparative example 1;

FIG. 5 is an internal metallographic structure of a clutch driven plate prepared in comparative example 1;

FIG. 6 is a fracture macro-morphology of a clutch driven plate drop-hammer test prepared in comparative example 1;

fig. 7 is the micro-topography of fig. 6.

Detailed Description

The present invention will be described in detail below with reference to specific embodiments and examples, and the advantages and various effects of the present invention will be more clearly apparent therefrom. It will be understood by those skilled in the art that these specific embodiments and examples are for the purpose of illustrating the invention and are not to be construed as limiting the invention.

Throughout the specification, unless otherwise specifically noted, terms used herein should be understood as having meanings as commonly used in the art. Accordingly, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. If there is a conflict, the present specification will control.

Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.

In the present invention, "first", "second", and "third" do not represent an order, and may be understood as nouns.

In order to solve the technical problems, the embodiment of the invention provides the following general ideas:

The effect of each element in the embodiment of the invention is as follows:

c: in this embodiment, carbon is used as a reinforcing element to improve the strength of the steel for a clutch disc.

Si: in this embodiment, silicon is a residual element and is removed as much as possible during the steel making process.

Mn: in this embodiment, manganese is a main strengthening element, and the strength of the steel for a clutch disc is improved; and the manganese element can be combined with the S element in the steel to generate MnS, thereby eliminating the adverse effect of S, and Mn is dissolved in ferrite and austenite in a solid way to enlarge an austenite zone.

P and S: both are harmful elements and are removed as much as possible in the steelmaking process.

Ti: the Ti element is added, so that the structure grain boundary can be pinned mainly in the annealing process, the coarsening and growth of the structure of the clutch driven disc are prevented, and the brittle failure problem is avoided; in addition, the method can also play a role in fine grain strengthening and precipitation strengthening. The Ti element should not be excessive, which increases the cost. In the embodiment of the invention, the mass fraction of Ti element is 0.01-0.02%.

In the embodiment of the invention, the steel for the clutch driven disc belongs to low-carbon aluminum killed steel.

As an alternative embodiment, the metallographic structure of the steel for a clutch driven disc is, in terms of volume fraction: 95-99% of ferrite and 1-5% of pearlite.

As an optional implementation mode, the thickness of the steel for the clutch driven plate is 3.5-7.0 mm.

In a second aspect, the embodiment of the invention also provides a preparation method of the steel for the clutch driven disc, which comprises the following steps,

s1, obtaining a plate blank; the slab comprises the following chemical components in percentage by mass: c: 0.025-0.1%, Si is less than or equal to 0.05%, Mn: 0.18-0.3%, P is less than or equal to 0.02%, S is less than or equal to 0.015%, Ti: 0.01-0.02% of Fe and inevitable impurities as the rest;

s2, heating, rough rolling, finish rolling and coiling the plate blank to obtain the steel for the clutch driven plate; the heating temperature is 1180-1220 ℃, the rough rolling is R1 single-pass rolling and R25-pass reversible rolling, the R1 inlet temperature of the rough rolling is 1130-1180 ℃, the finish rolling inlet temperature is 950-1100 ℃, the finish rolling outlet temperature is 850-890 ℃, and the coiling temperature is 580-640 ℃.

In the embodiment, the plate blank is heated by the heating furnace, the heating temperature is 1180-1220 ℃, and the austenitizing of the plate blank structure can be realized. Rolling a plate blank with the thickness of 230mm into an intermediate blank with the thickness of 35-42 mm through rough rolling; rolling the intermediate blank into a target finished product thickness through finish rolling; the temperature of the finish rolling inlet and the finish rolling outlet is controlled to control the rolled structure in the finish rolling area, the finish rolling should be carried out in an austenite area, the temperature of the low-carbon aluminum killed steel entering the two-phase area is 840-850 ℃, so the temperature of the finish rolling outlet must be higher than the temperature of the two-phase area, ferrite is preferentially separated out when the temperature of the finish rolling inlet and the finish rolling outlet is too low, the preferentially separated ferrite is directly elongated and enlarged, the preferentially separated ferrite is thickened, a coarse-grained structure is obtained, and the earing defect occurs in stamping. The finish rolling temperature is too high, so that the finish rolling speed is too high for ensuring the finish rolling outlet temperature, and the finish rolling is unstable.

The coiling temperature is controlled to be 580-640 ℃, and the ferrite structure is controlled to be uniform. The coiling temperature is too high, ferrite grains are large and uniform, which is caused by low alpha transformation supercooling degree and few nucleation points, mainly concentrated at the grain boundary of the original gamma grains and higher growth speed of the ferrite; the coiling temperature is too low, the alpha nucleation number is increased, the growth speed of ferrite is reduced, the ferrite grain size is reduced, the ferrite grain is refined, the quantity of acicular ferrite is gradually increased, meanwhile, pearlite tends to be dispersed and fine, the pearlite content is increased, and the lamellar spacing of the pearlite is also gradually reduced. The structure of the punched product of the steel for the clutch driven plate cannot be too coarse and too fine.

After the steel for the clutch driven disc is subjected to stamping deformation, the deformation part has the problem of work hardening, in annealing, firstly, the material subjected to stamping deformation is heated to a lower temperature of 700-750 ℃ through first heating, and is subjected to heat preservation for 10-20 min, so that energy among tissues at the deformation part can be completely released, and the situation that larger tissues at the deformation part are swallowed and smaller tissues are swallowed due to direct heating to a higher temperature is avoided; meanwhile, Ti element pins the tissue crystal boundary in the annealing process, so that coarsening and growth of the tissue are prevented, and the brittle failure problem is avoided. If the heating temperature is too low and the heating time is too short, the structure at the deformed position is likely to be non-uniform, which may cause brittle failure.

As an optional embodiment, the temperature of the second heating is 820-830 ℃, the heat preservation time of the second heating is 120-130 min, the temperature of the third heating is 840-850 ℃, and the heat preservation time is 1-3 min.

The second heating is to further raise the temperature of the workpiece and ensure that the workpiece is not deformed at the temperature, and the higher the temperature is, the faster the carbonitriding speed is. If the second heating temperature is too high, the second heat preservation time is too long, and the part is softened and deformed; if the second heating temperature is too low, the second heat preservation time is too short, and the carbonitriding time is not enough, so that the hardness of the part is low. If the third heating temperature is too high, the third heat preservation time is too long, and the part is softened and deformed; if the third heating temperature is too low and the third holding time is too short, the strength of the part after quenching is too low.

As an optional embodiment, in the second heating and the third heating, carbonitriding is performed, wherein carbonitriding is performed using methane and ammonia gas, and in the carbonitriding, the temperature is 750 to 850 ℃, the carbon potential is 0.1 to 0.12%, the volume concentration of ammonia gas is 0.25 to 0.5%, and the time is 120 to 130 min.

Carbonitriding is a chemical surface heat treatment process in which carbon and nitrogen are simultaneously infiltrated into the surface of a steel part. Mainly carburization and a small amount of nitrogen is permeated. Compared with the carburizing process, the carbonitriding process has the advantages of higher infiltration speed, higher hardenability and tempering resistance of a carburized layer, good wear resistance and fatigue resistance and the like, has lower treatment temperature, and is usually used for replacing carburizing treatment. It overcomes the defects that the hardness of a nitriding layer is high but the nitriding layer is shallow, and the hardening depth of a carburizing layer is large but the surface hardness is low to a certain extent.

In this embodiment mode, the lower carbonitriding temperature is used, and the carbon potential and ammonia gas volume concentration, and the carbonitriding time are controlled in order to ensure the final carburized layer thickness. If the carbon potential is too low and the volume concentration of ammonia gas is too low, the thickness of a carburized layer is too small, the hardness of a clutch driven disc is low, and brittle fracture is easy to occur; if the carbon potential is too high, the volume concentration of ammonia gas is too high, which results in increased cost. If the temperature of the second heating and the third heating is reduced and the heat preservation time of the second heating and the third heating is shortened, the grain growth size can be effectively reduced, but the carbonitriding effect is weakened at low temperature, and the strength of the surface of the clutch driven disc is reduced.

As an optional embodiment, the quenching is oil quenching, the cooling rate of the quenching is 97-105 ℃/s, the quenching starting temperature is 845-855 ℃, and the quenching finishing temperature is 85-95 ℃.

The starting temperature, the ending temperature and the cooling rate of the oil quenching are controlled, and the effects of 80-90% of martensite structure, 5-20% of bainite and 2-5% of ferrite and pearlite in total can be obtained.

The martensite structure is a harder phase which gives the material good strength.

In actual production, the larger the cooling rate, the better, but the oil quenching cooling does not generally exceed 105 ℃/s; if the cooling rate of the oil quenching is too low and the temperature at the end of the oil quenching is too high, a bainite structure and non-transformed ferrite are obtained, and a high-strength martensite structure cannot be obtained.

As an optional embodiment, the tempering temperature is 300-350 ℃. On one hand, the stability of the structure of the clutch driven disc can be improved, so that the structure transformation of the workpiece is avoided in the using process, and the geometric dimension and the performance of the workpiece are kept stable; internal stresses in the quenched steel part can also be reduced or eliminated, or its hardness and strength reduced, to increase its ductility or toughness, in order to improve the service properties of the workpiece and stabilize the workpiece geometry; and the quenched workpiece should be tempered in time, and the required mechanical property can be obtained through the matching of quenching and tempering so as to meet the use requirement. In this embodiment, the tempering temperature may not be too high, otherwise the workpiece may be softened and the strength too low; the tempering temperature cannot be too low, otherwise the internal stress in the workpiece cannot be taken out, and the ductility or toughness is improved.

In embodiments of the present invention, the annealing may be performed in a box-type multi-purpose furnace.

The steel for a clutch driven plate, the method for producing the same, and the clutch driven plate according to the present invention will be described in detail with reference to examples, comparative examples, and experimental data.

TABLE 1

Numbering	C/％	Si/％	Mn/％	P/％	S/％	Ti/％
							Example 1	0.0314	0.0064	0.202	0.0073	0.0054	0.0209
Example 2	0.0322	0.0061	0.198	0.0083	0.0057	0.021
							Example 3	0.0404	0.0067	0.211	0.0132	0.0078	0.0193
Example 4	0.0319	0.0071	0.215	0.0131	0.0107	0.0204
							Comparative example 1	0.0337	0.0068	0.21	0.0104	0.0096	--

Example 1

In example 1, the steel type of the steel for the clutch disc was low carbon steel having a thickness of 3.5mm and a chemical composition shown in table 1, and the balance was Fe and inevitable impurities.

The slabs of the chemical compositions (balance Fe and inevitable impurities) of table 1 were hot-rolled to prepare steels for clutch discs. The hot rolling process is controlled as follows: the heating temperature of the heating furnace is 1200 ℃, in the rough rolling, R1 is single-pass rolling, R2 is 5-pass reversible rolling, the inlet temperature of the rough rolling R1 is 1140 ℃, the inlet temperature of the finish rolling is: 1070 ℃, finish rolling outlet temperature: 870 ℃ and a coiling temperature of 620 ℃.

Pickling and stamping the steel for the clutch driven disc to obtain a clutch driven disc part, and heating the stamped clutch driven disc part to 700 ℃ from a box-type multipurpose furnace for 10 minutes; then heating to 820 ℃, preserving the temperature and simultaneously introducing methane and ammonia gas for carbonitriding, wherein the carbon potential is 0.10%; the volume concentration of ammonia gas is 0.35, and the carbonitriding time is 120 min; continuously heating to 840 ℃, preserving the temperature for 1 minute, and simultaneously continuously carbonitriding, wherein the carbon potential is 0.10%; the volume concentration of ammonia gas is 0.3%, and the time is 1 min; after the quenching is finished, oil quenching is carried out, wherein the starting temperature of the oil quenching is 850 ℃, the cooling rate is 100 ℃/s, and the finishing temperature of the oil quenching is 90 ℃; then, the steel is cleaned and tempered, and the tempering temperature is 330 ℃.

Example 2

In example 2, the steel type of the steel for the clutch disc was low carbon steel having a thickness of 3.5mm and a chemical composition shown in table 1, and the balance was Fe and inevitable impurities.

The slabs of the chemical compositions (balance Fe and inevitable impurities) of table 1 were hot-rolled to prepare steels for clutch discs. Controlling a hot rolling process: heating furnace temperature 1198 ℃, RT1 inlet temperature 1160 ℃, finish rolling inlet temperature: 1080 ℃, finish rolling outlet temperature: 890 ℃ and a coiling temperature of 580 ℃.

Pickling and stamping steel for the clutch driven disc to obtain a clutch driven disc part, heating the stamped clutch driven disc part to 720 ℃ from a box-type multipurpose furnace, preserving heat for 10 minutes, heating to 825 ℃, and introducing methane and ammonia gas for carbonitriding, wherein the carbon potential is 0.12%; the volume concentration of ammonia gas is 0.5 percent, and the carbonitriding time is 120 min; continuously heating to 850 ℃, preserving the heat for 2min, and simultaneously continuously carbonitriding, wherein the carbon potential is 0.12%; the volume concentration of ammonia gas is 0.5%, and the time is 2 min; after the quenching is finished, oil quenching is carried out, wherein the starting temperature of the oil quenching is 850 ℃, the cooling rate is 100 ℃/s, and the finishing temperature of the oil quenching is 90 ℃; then cleaning and tempering, wherein the tempering temperature is 350 ℃.

Example 3

In example 3, the steel type of the steel for the clutch disc was low carbon steel having a thickness of 4mm and a chemical composition shown in table 1, and the balance was Fe and inevitable impurities.

The slabs of the chemical compositions (balance Fe and inevitable impurities) of table 1 were hot-rolled to prepare steels for clutch discs. Controlling a hot rolling process: the temperature of the heating furnace is 1195 ℃, the inlet temperature of RT1 is 1162 ℃, the inlet temperature of finish rolling is: 1080 ℃, finish rolling outlet temperature: 890 ℃ and the coiling temperature of 600 ℃.

Pickling and stamping steel for the clutch driven disc to obtain a clutch driven disc part, heating the stamped clutch driven disc part to 730 ℃ from a box-type multipurpose furnace, preserving heat for 10 minutes, then heating to 830 ℃, and introducing methane and ammonia gas for carbonitriding, wherein the carbon potential is 0.12%; the volume concentration of ammonia gas is 0.5 percent, and the carbonitriding is carried out for 130 min; continuously heating to 850 ℃, preserving the heat for 1min, and simultaneously continuously carbonitriding, wherein the carbon potential is 0.12%; the volume concentration of ammonia gas is 0.5 percent, and then oil quenching is carried out, wherein the starting temperature of oil quenching is 850 ℃, the cooling rate is 100 ℃/s, and the finishing temperature of oil quenching is 90 ℃; then cleaning and tempering, the tempering temperature is 340 ℃.

Example 4

In example 4, the steel type of the steel for the clutch disc was low carbon steel having a thickness of 4mm and a chemical composition shown in table 1, and the balance was Fe and inevitable impurities.

The slabs of the chemical compositions (balance Fe and inevitable impurities) of table 1 were hot-rolled to prepare steels for clutch discs. Controlling a hot rolling process: furnace temperature 1210 ℃, RT1 inlet temperature: 1179 ℃, finish rolling inlet temperature: 1070 ℃, finish rolling outlet temperature: 880 ℃ and a coiling temperature of 600 ℃.

Pickling and stamping the steel for the clutch driven disc to obtain a clutch driven disc part, and heating the stamped clutch driven disc part to 735 ℃ from a box-type multipurpose furnace for 10 minutes; then heating to 830 ℃, preserving the heat for 130min, and simultaneously introducing methane and ammonia gas for carbonitriding for 130min, wherein the carbon potential is 0.12%, the volume concentration of the ammonia gas is 0.5%, and the carbonitriding is carried out; continuously heating to 850 ℃, keeping the temperature for 2min, and simultaneously continuously maintaining carbonitriding for 2min, wherein the carbon potential is 0.12%, the volume concentration of ammonia gas is 0.5%, and carbonitriding is carried out for 2 min; after the quenching is finished, oil quenching is carried out, wherein the starting temperature of the oil quenching is 850 ℃, the cooling rate is 100 ℃/s, and the finishing temperature of the oil quenching is 90 ℃; then cleaning and tempering, wherein the tempering temperature is 350 ℃.

Comparative example 1

Comparative example 1 provides a method for manufacturing a clutch driven plate using low carbon steel, whose chemical composition is shown in table 1, and the balance being iron and inevitable impurities, as follows:

the slabs of the chemical compositions (balance Fe and inevitable impurities) of table 1 were hot-rolled to prepare steels for clutch discs. Controlling a hot rolling process: the temperature of a heating furnace is 1210 ℃, the inlet temperature of RT1 is 1179 ℃, the inlet temperature of finish rolling is: 1070 ℃, finish rolling outlet temperature: 880 ℃ and a coiling temperature of 600 ℃.

Pickling and stamping the steel for the clutch driven disc to obtain a clutch driven disc part, heating the stamped clutch driven disc part to 860 ℃ from a box-type multipurpose furnace, and preserving heat for 120 minutes; then reducing the temperature to 835 ℃, preserving the temperature for 2min, performing oil quenching, then cleaning, and then tempering, wherein the tempering temperature is as follows: at 350 ℃. From the start of heating to 860 ℃ to the start of oil quenching, methane and ammonia gas were introduced to conduct carbonitriding, wherein the carbon potential was 0.105% and the ammonia gas volume concentration was 0.3%.

The clutch driven disc prepared in examples 1 to 4 and comparative example 1 was subjected to a drop weight test, which is an impact test method. The weight falls on the part from different heights, and the relationship between the height of the falling weight and the thickness of the part is shown in the following table 2:

TABLE 2

Thickness of clutch driven disc，mm	Height of drop weight, mm
		3.5≤d＜4.5	1300
4.5≤d＜5.5	1400
		5.5≤d＜6.5	1500
6.5≤d≤7.5	1600

The hardness detector is used for detecting the surface hardness of the clutch, the thickness of the carburized layer in the metallographic structure of the clutch driven disc is measured, and the result is shown in table 3.

TABLE 3

Numbering	Surface hardness HRC	Carburized layer thickness/mm	Whether or not it is brittle	Fracture morphology
					Example 1	85	0.3	Is not brittle	Fracture normality
Example 2	90	0.34	Is not brittle	Fracture normality
					Example 3	88	0.35	Is not brittle	Fracture normality
Example 4	95	0.37	Is not brittle	Fracture normality
					Comparative example 1	84	0.31	Brittle fracture	Fracture anomaly

As can be seen from Table 3, the clutch discs of examples 1 to 4 had a surface hardness of 85 to 95HRC, a carburized layer thickness of 0.3 to 0.37mm, no brittle fracture occurred in the drop weight test, and a fracture morphology was normal, as shown in FIG. 1. The microscopic morphology of the fracture is shown in FIG. 2 when the fracture is observed, and as can be seen from FIG. 2, the fracture morphology is not abnormal; the carburized thickness micro-topography of the clutch driven disc is shown in figure 3, and subcutaneous grains are not abnormally grown.

The surface hardness of the clutch driven plate of the comparative example 1 is 84HRC, the thickness of the carburized layer is 0.31mm, FIG. 4 is a microstructure diagram of the carburized thickness of the clutch driven plate of the comparative example 1, and as can be seen from FIG. 4, subcutaneous crystal grains are extremely large; when the structure of the press-deformed part is observed, as shown in fig. 5, the structure grains of the deformed part are obviously abnormal and coarse and can exceed 300 μm, and the brittle fracture problem occurs in the drop-weight test, as shown in fig. 6 and 7.

The invention provides steel for a clutch driven disc, a preparation method of the steel and the clutch driven disc, wherein low-carbon steel is adopted to replace traditional medium-carbon steel to prepare the clutch driven disc, and Ti element is added in the component design, so that the structure grain boundary of a deformation part is pinned in the annealing process, the structure of the material is prevented from coarsening and growing, and the brittle failure problem is avoided. The temperature change curve of the annealing process is controlled, the annealing process is firstly heated to a lower temperature (700-750 ℃) and is kept for 10-20 min, energy generated by deformation can be completely released, and the problem that larger tissues at the deformation position are swallowed and smaller tissues are caused by directly heating to a higher temperature is avoided, so that the problems that the tissues grow up coarsenedly and brittle fracture is easy to occur are solved. The method provided by the invention solves the technical problem of brittle fracture on the basis of ensuring the surface hardness and the carburized thickness of the clutch driven disc.

Finally, it should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.

While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.

It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.

Claims

1. A clutch driven plate is characterized in that the clutch driven plate is made of steel through pickling, stamping deformation, annealing, quenching and tempering;

the steel for the clutch driven disc comprises the following chemical components in percentage by mass: c: 0.025-0.1%, Si is less than or equal to 0.05%, Mn: 0.18-0.3%, P is less than or equal to 0.02%, S is less than or equal to 0.015%, Ti: 0.01-0.02% of Fe and inevitable impurities as the rest; the metallographic structure of the steel for the clutch driven disc comprises the following components in percentage by volume: 95-99% of ferrite and 1-5% of pearlite;

in the annealing, sequentially carrying out first heating, second heating and third heating on the steel for the clutch driven disc after the stamping deformation, wherein the temperature of the first heating is 700-750 ℃, and the heat preservation time of the first heating is 10-20 min; the temperature of the second heating is 820-830 ℃, the heat preservation time of the second heating is 120-130 min, the temperature of the third heating is 840-850 ℃, and the heat preservation time of the third heating is 1-3 min; and in the second heating process and the third heating process, performing carbonitriding, wherein the carbonitriding is performed by using methane and ammonia gas, the quenching is oil quenching, the cooling rate of the quenching is 97-105 ℃/s, the quenching starting temperature is 845-855 ℃, the quenching finishing temperature is 85-95 ℃, and the tempering temperature is 300-350 ℃.

2. The clutch driven plate according to claim 1, wherein in the carbonitriding, the temperature is 750 to 850 ℃, the carbon potential is 0.1 to 0.12%, the volume concentration of ammonia gas is 0.25 to 0.5%, and the time is 120 to 130 min.

3. The clutch disc according to claim 1, wherein the thickness of the steel for the clutch disc is 3.5 to 7.0 mm.

4. The clutch driven plate according to claim 1, wherein the metallographic structure of the clutch driven plate comprises martensite, bainite, ferrite and pearlite, the volume fraction of the martensite is 80-90%, the volume fraction of the bainite is 5-15%, and the total volume fraction of the ferrite and the pearlite is 2-5%.