Classifications

• • 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
  • 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
  • C21D1/78—Combined heat-treatments not provided for above
• • 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
  • C21D6/002—Heat treatment of ferrous alloys containing Cr
• • 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
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
• • 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
  • C21D2211/00—Microstructure comprising significant phases
  • C21D2211/003—Cementite

Definitions

• Tempering is performed at a cooling rate of 1 ° CZ second to generate fine carbides and / or nuclei of the carbides on the surface layer of the member, and then the member is heated and soaked to the temperature of the austenite region.
• high-concentration carburizing and low-distortion quenching characterized by consisting of a secondary treatment that precipitates fine carbides in the range of 10 to 30% of effective hardening depth ratio in the outermost layer by rapid quenching A method for manufacturing the insert member.
• the surface layer is a structure mainly composed of martensite including a mixed structure such as troostite and retained austenite, and the order of the fineness of the austenite grain size of the layer.
• a high-concentration carburizing / low-distortion quenching member characterized in that A ⁇ C ⁇ B in the layer inside part A (part B) and the layer inside part B (part C).
• the method of the present invention uses a low-pressure carburizing equipment for the processing of the member, a primary treatment in which the member is quenched at an appropriate high-concentration carburizing and an optimal cooling rate, and a simple and efficient fine carbide that is subsequently performed.
• the heat treatment deformation and distortion of the treated member can be minimized.
• This method greatly reduces the number of complicated grinding and distortion correction processes after processing, such as bending of the shaft and deformation of the tooth profile, which were the biggest concerns of conventional high-concentration carburization. It has the effect of making significant improvements in productivity, quality, and cost of high-concentration carburized components.
• the surface of the member is subjected to additional carburization to increase the hardness of the matrix (base), and the outermost layer of the member.
• the crystal grain size of the part can be made ultrafine, which is extremely effective for increasing the strength and toughness of the member.
• the method of the present invention it is possible to easily achieve high strength, high toughness, high surface pressure, etc. of members such as shafts and gears, which have conventionally been difficult to apply high-concentration carburizing. Therefore, the method of the present invention can be widely applied to fields where such needs are high, and has the effect of being able to make a significant contribution to the improvement of the performance of members and the small and light weight. .
• the effective hardening depth ratio means the carburized effective hardening depth (T) after completion of the secondary treatment of the member (including 180 ° C tempering treatment) and the finest surface layer portion of the member. It means the ratio (t / T) to the carbide precipitation depth (t).
• the carburizing effective hardening depth is the Vickers hardness (HV) from the surface of the hardened layer as it is quenched or tempered at a temperature not exceeding 200 ° C according to the JIS G0557 steel carburized hardened layer depth measurement method. The distance to the limit depth position of 550.
• the precipitation depth of fine carbide is analyzed by an optical microscope or an electron microscope, and the maximum depth at which fine carbide exists from the outermost layer portion of the member is measured.
• the member is analyzed in an etching state using a corrosive solution such as 5% nitrate alcohol.
• the inventors have performed a primary treatment in which high-concentration carburization is performed on the surface layer portion of the material using low-pressure carburizing equipment, and fine particles of carbide are precipitated in the surface layer portion.
• a detailed study was conducted on the secondary treatment to be performed, including temperature rise, soaking, carbon concentration and diffusion during carburization, and various cooling (quenching) conditions.
• the carbon concentration is preferably 0.8% by mass or more, more preferably 1.0 to 2.0% by mass in the range of 10 to 30% in effective curing depth ratio (t / T) at the outermost layer.
• Table 2 summarizes various effects of the cooling rate on the precipitation state of carbide in the surface layer portion of the specimen and the heat treatment deformation of the specimen in the primary treatment of the present invention.
• the test piece was subjected to high-concentration carburization with the target of an effective hardening depth of 0.5 mm after heating and soaking in the heat cycle shown in FIG.
• Table 2 Relationship between primary treatment cooling conditions, carbide precipitation and axial runout
• Cooling rate represents the average cooling rate at the axial center of the specimen from the quenching temperature of 950 ° C after completion of carburizing and diffusion of the specimen to 400 ° C.
• Shaft run-out represents the run-out at the center of the shaft measured with a dial gauge with the test piece attached to a run-out measuring instrument supported at both ends.
• the cooling rate during cooling is as low as 1 ° C / sec.
• Precipitation of continuous network carbides is the main, and the base becomes an incompletely quenched structure of ferrite, pearlite, and bainite.
• axial runout and deformation become large.
• the comparative example shown in test piece No. 3 was obtained by rapid cooling equivalent to a typical oil quenching (20 ° C / sec), and the amount of carbide precipitation was very small and high carbon with supersaturated carbon. It becomes a quenched structure from the state, and the shaft runout and deformation are large.
• the cooling rate of the examples shown in test pieces 2, 5, and 7 is 4 to 12 ° C / sec (the present invention)
• a large amount of fine carbides are precipitated, and the fine particles that form the core
• the appearance of the structure improved the deformation and strain (shaft runout) of the specimen, which was a major concern for high-concentration carburization.
• the shaft runout amount of the test piece is approximately half that of the other examples, and the shaft runout amount can be significantly reduced. It was. Based on these results, the cooling rate during quenching of the primary treatment is optimally 3 to 15 ° C / sec.
• Table 3 uses a representative test piece of the primary treatment shown in Table 2 and performs a secondary treatment for the purpose of finally precipitating fine carbides on the surface layer portion.
• the results of various investigations such as concentration, carbide precipitation state, microstructure, grain size, and axial runout of the specimen are shown.
• the secondary treatment the soaking temperature is set to three levels of 800 ° C, 850 ° C and 900 ° C above the A transformation in the heat cycle shown in Fig. 2, and the surface layer is obtained by secondary treatment.
• test piece (307 () 25/20 and 300111111
• the secondary treatment temperature (herein referred to as the tempered carburizing temperature)
• the carbide in the surface layer was dissolved and the entire carbide
• the precipitation of particles is small and the axial runout of the test piece is also large.
• the 800 ° C secondary treatment temperature used for test piece No. 2-3 flake carbides precipitated at the grain boundaries of the surface layer, and the inside of the member (unhardened part) was incompletely quenched. Variations in the axial runout of the test piece appear. From these results, the optimum processing temperature for precipitating fine carbides on the surface layer in the secondary treatment is determined by the composition of the member (before carburizing treatment), and a temperature corresponding to the A transformation point temperature + 10 to 70 ° C is preferable. .
• test pieces 5-1 and 7 are identical to test pieces 5-1 and 7
• the austenite grain size of the outermost layer portion of the additional-force carburized member was an ultrafine grain size as shown in FIG.
• the ultra-fine grain size and carburized grain size test method in the austenite grain size test method of IS-G0551 steel the austenite crystal grain size corresponds to No. 10 or more, and further consists of fine grains and fine grains toward the internal direction.
• the austenite grain size of the surface layer in normal carburizing is generally equivalent to No. 7-8, and in the present invention, the conventional carburizing treatment is performed. It has a distinctive three-layered grain structure that does not appear in theory.
• Table 4 shows the effect of the effective hardening depth ratio of the carbide precipitation layer on various characteristics in the high-concentration carburization of the present invention.
• various test pieces were prepared by machining after pre-normalizing the material at 900 ° C using SCM420 of JIS machine structural steel as a material.
• the high-concentration carburization treatment of the test piece was performed in the heat cycle of the primary treatment and the secondary treatment shown in Fig. 3.
• the treated specimens were analyzed for pitting life, impact strength, heat treatment strain, etc.
• the effect of the carbon concentration in the outermost layer of the test piece shown in Table 5 on the strength durability and heat treatment deformation of the test piece was also treated in the heat cycle shown in Fig. 3, as in the case of the various test pieces in Table 4.
• the carbon concentration of the treated specimen was examined.
• pressurized gas cooling in which gases such as He, H, etc. are used alone or in combination.
• the depth ratio of the carbide precipitation layer to the effective hardening depth is optimally in the range of 10-30%.
• the symbols H, J, and K which have a higher carbon concentration in the outermost layer, are superior, and the carbon concentration is higher than that of the former.
• symbols G and I which are as low as 1%, it can be said that the pitching life is partially inferior.
• the carbon content of the outermost layer is less than 0.8% by mass as shown by reference symbol F, the test piece has a significantly poor pitching toughness. That is, the higher the carbon concentration, the better the finer carbides deposited on the outermost layer. Therefore, in the present invention, the carbon concentration of the high-concentration carburization is set to 0.8 mass% or more.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
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• Mechanical Engineering (AREA)
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• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)
• Heat Treatment Of Articles (AREA)

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• 2006
  • 2006-02-08 CA CA2594838A patent/CA2594838C/en not_active Expired - Fee Related
  • 2006-02-08 CN CN2006800041128A patent/CN101115859B/zh not_active Expired - Fee Related
  • 2006-02-08 US US11/883,793 patent/US20080156399A1/en not_active Abandoned
  • 2006-02-08 EP EP06713304.1A patent/EP1847630B1/de not_active Expired - Fee Related
  • 2006-02-08 JP JP2007502622A patent/JP4627776B2/ja not_active Expired - Fee Related
  • 2006-02-08 KR KR1020077018051A patent/KR100898679B1/ko active IP Right Grant
  • 2006-02-08 WO PCT/JP2006/302161 patent/WO2006085549A1/ja active Application Filing

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