US20160145705A1 - Wear-resistant, partially uncoated steel parts and methods of producing same - Google Patents

Wear-resistant, partially uncoated steel parts and methods of producing same Download PDF

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Publication number
US20160145705A1
US20160145705A1 US14/903,022 US201414903022A US2016145705A1 US 20160145705 A1 US20160145705 A1 US 20160145705A1 US 201414903022 A US201414903022 A US 201414903022A US 2016145705 A1 US2016145705 A1 US 2016145705A1
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Prior art keywords
hardening
steel
wear
resistant
semifinished
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US14/903,022
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Sascha Sikora
Janko Banik
Thiemo Wuttke
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ThyssenKrupp Steel Europe AG
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ThyssenKrupp Steel Europe AG
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Assigned to THYSSENKRUPP STEEL EUROPE AG reassignment THYSSENKRUPP STEEL EUROPE AG ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: WUTTKE, THIEMO, BANIK, JANKO, SIKORA, SASCHA
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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/0068—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for particular articles not mentioned below
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/06—Surface hardening
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/62—Quenching devices
    • C21D1/673—Quenching devices for die quenching
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/005—Modifying the physical properties by deformation combined with, or followed by, heat treatment of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/22—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for drills; for milling cutters; for machine cutting tools
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
    • C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
    • C23C8/20—Carburising
    • C23C8/22—Carburising of ferrous surfaces
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
    • C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
    • C23C8/24—Nitriding
    • C23C8/26—Nitriding of ferrous surfaces
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/80—After-treatment
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2221/00—Treating localised areas of an article
    • C21D2221/02—Edge parts
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D7/00—Modifying the physical properties of iron or steel by deformation
    • C21D7/13—Modifying the physical properties of iron or steel by deformation by hot working
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/18—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for knives, scythes, scissors, or like hand cutting tools

Definitions

  • the invention relates to a wear-resistant, at least partly uncoated steel part consisting of a hardenable steel grade which has been produced from a semifinished part by hot forming and/or hardening.
  • the invention relates to a process for producing a wear-resistant, at least partly uncoated processing, conveying and/or crushing means of agricultural machines, conveying machines, mining machines or building machines from a semifinished part, in which the semifinished part is heated to a temperature above the Ac1 transformation temperature and is subsequently hot formed and/or hardened.
  • Wear-resistant, at least partly uncoated steel parts which have to have high strengths and at the same time are subjected to abrasive forces are required, for example, for the production of agricultural machines, in particular plows, and also for buckets of a dredge or conveying screws for abrasive materials, for example the conveying screw of a concrete mixer.
  • the parts are preferably subjected to hot forming in which the semifinished parts from which the steel parts are produced are firstly heated to a temperature above the Ac1 transformation temperature point, so that transformation hardening of the microstructure is effected by hot forming and subsequent hardening, i.e.
  • the martensitic microstructure has a significantly greater hardness but also a significantly greater mechanical strength, for example tensile strength.
  • Corresponding steel parts are known, for example, from the German patent DE 10 2010 050 499 B3.
  • the German patent describes a process for producing dredger buckets, concrete mixer conveying screws, conveying screw blades or other transport blades of conveying plants, in which the components are hot formed and press hardened.
  • the German first publication DE 10 2010 017 354 A1 is concerned with the problem of hot forming of zinc-plated flat steel products to produce high-strength or very high-strength steel components.
  • the melting point of the metal of the protective coating is exceeded, there is a risk of “liquid metal embrittlement” which is caused by penetration of the molten metal of the coating into the notches or cracks arising in forming of the flat steel product.
  • the liquid metal which has penetrated into the steel substrate deposits at grain boundaries and there reduces the maximum tensile or compressive stress which can be withstood.
  • the patent publication offers nitriding of the outer layer regions, so as to produce finely structured outer layer regions.
  • the present invention is, in contrast, concerned with the problem that hot-formed and/or hardened steel parts do not have the desired wear resistance in the uncoated regions and are therefore not optimally suited for use as conveying means, for example on contact with abrasive materials. It is therefore an object of the present invention to propose at least partly uncoated steel parts having improved suitability for use with abrasive materials. In addition an inexpensive production process for corresponding steel parts should be proposed.
  • the object indicated is achieved, for a steel part, the steel part at least partially having a surface region which has been hardened to a depth of not more than 100 ⁇ m, preferably to a depth of up to 40 ⁇ m, by surface hardening before hot forming and/or hardening.
  • the hardened surface region of the steel part is hardened by carburization or nitriding. Both processes offer the opportunity of hardening regions close to the surface of the steel part in a targeted manner before hot forming or hardening.
  • nitriding has the advantage that the hardness is not reduced during hot forming. In the case of carburization, the carbon content in the surface regions is increased but decreases again due to hot forming.
  • the hardened surface region of the steel part preferably has at least the hardness of the base material of the steel part located under the surface region.
  • the wear resistance of the steel part can preferably also be improved by the hardness of the surface region of the steel part being greater than the hardness of the base material. It has been found that, in particular, the hardness of the surface regions is responsible for the wear resistance of the steel part on contact with highly abrasive materials, so that a very wear-resistant steel part can be produced even when using a somewhat softer base material.
  • the steel part is, according to a further embodiment of the steel part, configured for use as processing, conveying and/or crushing means in agricultural machines, conveying machines, mining machines or building machines, with at least the regions of the steel part which are subjected to abrasive forces being surface-hardened.
  • manganese-boron steels dual-phase steels or TRIP steels, in which particularly pronounced martensite formation or transformation of residual austenitic components into martensite makes an increase in the hardnesses possible, are also particularly advantageous.
  • the surface region of the steel part which has been hardened before hot forming and/or hardening has, at least in regions, a hardness of from 400 to 700 HV. These values are generally achieved only by very high-strength steel grades after hot forming or hardening in the base material.
  • the surface hardening before hot forming or hardening offers, in particular, the opportunity of providing the starting material for production of the steel components on a coil.
  • the abovementioned object is achieved by a process for producing a wear-resistant, at least partly uncoated steel part for processing, conveying and/or crushing means of agricultural machines, conveying machines, mining machines or building machines from a semifinished part, in which the semifinished part is heated, at least in regions, to a temperature above the Ac1 transformation temperature and is subsequently hot formed and/or hardened, in that the semifinished part at least partially is subjected to surface hardening in which a surface region is hardened to a depth of not more than 100 ⁇ m before hot forming and/or hardening.
  • the depth of the surface region which is to be hardened is controlled by the duration of the hardening treatment. It has been found, in particular, that despite heating to a temperature above the Ac1 transformation temperature point, the surface-hardened regions of the steel part remain stable in respect of the surface hardness, so that high surface hardness can be achieved after hot forming and/or hardening. This leads to the steel parts of processing, conveying and/or crushing means of agricultural machines, conveying machines, mining machines or building machines which are in contact with abrasive materials displaying reduced wear.
  • the hardening of the surface regions before hot forming or before hardening makes it possible to carry out the surface hardening on coilable materials, i.e. on steel strip, so that particularly economical production of wear-resistant, at least partly uncoated steel parts from semifinished parts is made possible.
  • hardening of the surface region is effected by nitriding or by carburization. Both processes make it possible to provide a higher hardness in the surface region, which after hot forming and/or after hardening make a higher wear resistance of the surface of the hot-formed or hardened steel part possible.
  • the surface hardening is, in a further embodiment, particularly preferably carried out by a heat treatment in a heat treatment atmosphere comprising up to 25% by volume of H 2 , 0.1-10% by volume of NH 3 , H 2 O and a balance N 2 and also unavoidable impurities at a holding temperature of from 600° C. to 900° C.
  • the dew point of the heat treatment atmosphere is preferably in the range from ⁇ 50° C. to ⁇ 5° C., so that the effect of atmospheric moisture on the hardening process is reduced.
  • preference is given to a maximum of 10% by volume of H 2 and a maximum of 5% by volume of NH 3 being permitted and the dew point being set to a dew point temperature of from ⁇ 40° C. to ⁇ 15° C. at a temperature of from 680 to 840° C.
  • the latter process parameters gave improved and more uniform surface hardening.
  • the depth of the surface hardening can be set via the time for which the holding temperature is maintained.
  • the time for which the semifinished part has the holding temperature during surface hardening is preferably set to from 5 s to 600 s, preferably from 30 s to 120 s.
  • the surface hardening is preferably carried out in a continuous hardening furnace, so that, for example, a strip-like semifinished part, i.e. a coilable semifinished part, is also surface-hardened and can be fed to the further hot forming and/or press hardening steps.
  • a strip-like semifinished part i.e. a coilable semifinished part
  • surface hardening in a chamber furnace is also conceivable.
  • semifinished parts such as manganese-boron steels, dual-phase steels and TRIP steels firstly display a particularly high strength increase during hot forming or during hardening and secondly provide the opportunity of bringing the regions close to the surface to identical hardness in the range from 400 to 700 HV by nitriding.
  • steel parts which are very wear-resistant and have particularly high strengths can be produced inexpensively.
  • FIG. 1 schematically shows an example of the process for producing a wear-resistant, at least partly uncoated steel part
  • FIG. 2 shows the layer structure of the semifinished part or steel part treated as per the example in FIG. 1 in a schematic illustration
  • FIGS. 3, 4 shows examples of a steel part for agricultural machines and conveying machines
  • FIG. 5 shows a graph of the hardness profile as a function of the distance from the surface for two examples and a comparative example.
  • FIG. 1 firstly shows, very schematically, an example of the production of a wear-resistant, at least partly uncoated steel part in a schematic illustration.
  • the semifinished part 1 which consists of a steel, for example a manganese-boron steel, dual-phase steel or TRIP steel, is firstly fed to surface hardening 2 . If a strip-like semifinished part is reeled off a coil 1 a and fed to surface hardening 2 , it is, for example, advantageous to carry out surface hardening, for example in the case of nitriding, in a continuous hardening furnace at the end of which, for example, the strip-like semifinished part 1 , now provided with a hardened surface, can be wound up on a coil (not shown).
  • the surface-hardened strip-like semifinished part is cut to length and fed to hot forming and/or hardening 3 , so that process step 3 can produce a formed, at least partly uncoated steel part 4 which is suitable for processing, conveying and/or crushing means of agricultural machines, conveying machines, mining machines or building machines.
  • the steel part 4 produced in this way characterizes high strength values owing to the hot forming and/or hardening step.
  • the surface region of the steel part also has an increased hardening due to the nitriding of the surface which has taken place before hot forming and/or before hardening.
  • the process of the invention enables the decarburization of the surface regions, which takes place to a depth of 100 ⁇ m, to be countered by the surface region being surface-hardened to a depth of 100 ⁇ m or in a region down to a depth of 40 ⁇ m.
  • the surface hardening is preferably carried out by nitriding.
  • carburization of the surface region is also conceivable.
  • the surface hardening in process step 2 is preferably carried out by means of a heat treatment in a heat treatment atmosphere comprising up to 25% by volume of H 2 , 0.1-10% by volume of NH 3 , H 2 O and balance N 2 and also unavoidable impurities at a holding temperature of from 600° C. to 900° C. Reduction of the hydrogen concentration to a maximum of 10% by volume or limiting of the NH 3 concentration to a maximum of 5% by volume also leads to a further improvement of the nitriding result.
  • the depth of the surface hardening can be set via the duration of the surface hardening, for example at a holding temperature of from 5 s to 600 s.
  • the surface is preferably nitrided at a holding temperature of from 30 s to 120 s, with the temperature being from 680° C. to 840° C.
  • Carrying out the surface hardening before hot forming or hardening has the advantage that a heat treatment process can be carried out significantly more efficiently using a, for example, strip-like semifinished part in a continuous hardening furnace or a plate in a continuous hardening furnace than when using formed steel parts which have different shapes and different geometries.
  • the quality of the surface hardening can likewise be ensured more easily by the use of strip-like semifinished parts or semifinished parts configured as a blank.
  • FIG. 2 then schematically shows a cross section of the semifinished part at three different points in time during the process.
  • the semifinished part 1 has a more or less homogeneous, for example ferritic microstructure 1 a corresponding to the production process, which is determined by the combination of production process and steel composition.
  • the surface region lb is hardened by inward diffusion of nitrogen in the case of nitriding or carbon in the case of carburization, with the microstructure changing there.
  • the thickness of the surface region 1 b depends on the duration of the heat treatment.
  • the surface region is usually up to a maximum of 100 ⁇ m in which the hardness of the semifinished part is altered.
  • a preferred region which is a compromise between sufficient surface hardening and duration of the heat treatment for surface hardening, has a thickness of from 20 to 40 ⁇ m.
  • the duration of surface hardening is then preferably from 30 s to 120 s.
  • the microstructure of the material 1 a remaining underneath the surface region 1 b remains essentially unchanged during the heat treatment.
  • the microstructure of the base material 1 a is then firstly converted into austenite and, by means of hardening, later partially into martensite. In this way, high hardness and good mechanical strengths are achieved in the base material 1 c .
  • the surface region 1 b remains unchanged except for carburization of these layers. As a result of nitriding, the surface region can continue to remain hardened. In the case of targeted carburization of the surface region 1 b instead of nitriding, decarburization can be countered, so that an increase in the hardness is also achievable here.
  • the formed steel part 4 thus has a hardened region 1 b and also a region 1 c which has been hardened by the hot forming and hardening.
  • FIGS. 3 and 4 show typical fields of application for the wear-resistant, at least partially uncoated steel part in the form of a conveying screw 5 in FIG. 3 and a plowshare 6 for agricultural plows in FIG. 4 .
  • Both components are typical representatives of processing, conveying and/or crushing means which are used in agricultural machines, conveying machines, mining machines or building machines, for example concrete mixers, and are exposed to highly abrasive materials.
  • the use of hot formed and/or press hardened steel parts has hitherto not been very advantageous because of the increased susceptibility to wear. Due to the surface hardening of the region which is decarburized during hot forming and/or hardening, the hot forming steels gain an enlarged range of uses.
  • Table 1 shows measurements of the hardness of samples A and B which consist of a steel of grade 22MnB5.
  • the samples A and B were subjected to surface nitriding in a heat treatment atmosphere comprising 1% by volume of NH 3 or 4% by volume of NH 3 at 760° C. and 90 s in each case.
  • the surface nitriding was carried out at inter-critical temperatures (T>Ac1) since austenite can dissolve more nitrogen than ferrite.
  • the samples were subsequently hot formed and hardened. Polished sections were made from the hot formed or hardened steel parts and the hardness HV 0.01 (DIN EN ISO 6507-1) was measured at a distance of 5 ⁇ m from the surface.
  • the microhardness measurement on the samples as a function of the content of NH 3 in the heat treatment atmosphere had a greater hardness at a higher NH 3 content of the heat treatment atmosphere at the same heat treatment parameters, i.e. hold time and hold temperature.
  • sample A firstly decreases from the value of 460 HV measured at the surface to a value of 333 HV at a depth of 20 ⁇ m. The hardness then increases again to a value of about 492 HV, which indicates that the decarburization of the base material ceases here.
  • the uppermost region, in particular, from 5 to 15 ⁇ m was significantly hardened by the surface hardening. It can be seen from sample B that the surface hardening is more pronounced, both in terms of the amplitude and the depth of hardening, at an increased NH 3 content. This can be attributed to greater diffusion of nitrogen into the surface of the steel part taking place due to the higher NH 3 concentration in the heat treatment atmosphere.
  • sample B start at 546 at a depth of 5 ⁇ m and decrease to a value of 394 at a depth of 25 ⁇ m.
  • the values subsequently increase again to about 466 at a depth of 45 ⁇ m. It can clearly be seen that the surface is harder than the base material at a depth of 45 ⁇ m.
  • FIG. 5 A similar picture is shown by the measurements on two further examples shown in FIG. 5 compared to a comparative example.
  • the comparative example illustrated by a dotted line displays a reduced hardness below 400 HV 1 (DIN EN ISO 6507-1) in the region of 5 to 35 ⁇ m.
  • the reduction in the hardness compared to the base material, which is in the range from 450 HV 1 to 500 HV 1, is explained by decarburization during hot forming.
  • the two comparative examples with two different nitriding variants, once again 1% strength NH 3 heat treatment atmosphere or 4% strength NH 3 heat treatment atmosphere, differ especially in this region close to the surface, since hardness of above 500 could be measured here.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Crystallography & Structural Chemistry (AREA)
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  • Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)
US14/903,022 2013-07-05 2014-06-24 Wear-resistant, partially uncoated steel parts and methods of producing same Abandoned US20160145705A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE102013107100.7 2013-07-05
DE102013107100.7A DE102013107100A1 (de) 2013-07-05 2013-07-05 Verschleißfestes, zumindest teilweise unbeschichtetes Stahlteil
PCT/EP2014/063259 WO2015000740A1 (de) 2013-07-05 2014-06-24 Verschleissfestes, zumindest teilweise unbeschichtetes stahlteil

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US (1) US20160145705A1 (de)
EP (1) EP3017074B1 (de)
JP (1) JP2016528381A (de)
KR (1) KR20160029102A (de)
CN (1) CN105358720A (de)
CA (1) CA2916155C (de)
DE (1) DE102013107100A1 (de)
ES (1) ES2704437T3 (de)
WO (1) WO2015000740A1 (de)

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DE102016200912A1 (de) 2016-01-22 2017-07-27 Thyssenkrupp Ag Verschleißschutzelement für eine Zerkleinerungseinrichtung
EP3533886A4 (de) * 2016-10-31 2020-04-01 Nippon Steel Corporation Verfahren zur herstellung eines stahlelements und stahlelement
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WO2015000740A1 (de) 2015-01-08
CN105358720A (zh) 2016-02-24
CA2916155C (en) 2017-11-07
EP3017074A1 (de) 2016-05-11
KR20160029102A (ko) 2016-03-14
JP2016528381A (ja) 2016-09-15
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