WO2012144283A1 - 複合鋼部品及びその製造方法 - Google Patents
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- WO2012144283A1 WO2012144283A1 PCT/JP2012/056967 JP2012056967W WO2012144283A1 WO 2012144283 A1 WO2012144283 A1 WO 2012144283A1 JP 2012056967 W JP2012056967 W JP 2012056967W WO 2012144283 A1 WO2012144283 A1 WO 2012144283A1
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- 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
- C23C8/02—Pretreatment of the material to be coated
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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
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/06—Surface hardening
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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
- 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
- C21D1/25—Hardening, combined with annealing between 300 degrees Celsius and 600 degrees Celsius, i.e. heat refining ("Vergüten")
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- 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
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- 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
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- 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
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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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/002—Bainite
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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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/008—Martensite
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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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/009—Pearlite
Definitions
- the present invention relates to a composite steel part having both a carburized and hardened part and a welded part, and a manufacturing method thereof.
- the steel part includes a first steel part having a cylindrical part having a cylindrical shape, a flange part extending radially outward from one end of the cylindrical part, and a second steel part in the flange part. It is a part that can be said to be a composite steel part produced by welding. Since the outer peripheral surface of the cylindrical portion of the first steel part is a sliding surface, carburizing and quenching is performed to improve wear resistance. On the other hand, the flange portion of the first steel part has a planned welding portion to be welded to the second steel component, and this planned welding portion is required not to be carburized to ensure weldability. .
- the following complicated manufacturing method is adopted. That is, using a steel material having a relatively low carbon content as a raw material, a steel part having a shape close to the final product is obtained through forging and cutting processes. Next, a carbon-proofing process is performed to cover the planned welding part of the steel part with a carbon-proofing agent. Next, oil quenching is performed immediately after carburizing in the gas carburizing furnace, and tempering is performed. Thereafter, shot blasting is performed on the portion subjected to the carbon-proof treatment to remove the carbon-proof agent. Finally, finishing steps such as polishing and washing are performed to obtain a first steel part. Thereafter, the first steel part and the second part are welded to obtain a final composite steel part.
- the conventional manufacturing method of the composite steel part when manufacturing the first steel part, carburizing after applying a carburizing treatment to apply a carburizing agent to the welded portion, Then, it is necessary to perform the process of removing a carburizing agent.
- the process of removing the carbon-proofing treatment and the carbon-proofing agent is very labor-intensive and leads to an increase in cost.
- the carbon-proof treatment is omitted, there is an adverse effect such as an increase in the amount of raw material carbon in the portion to be welded, causing a weld crack during welding. Therefore, it is not possible to simply omit the carbon-proof treatment.
- the present invention has been made on the basis of such a background, and it is possible to obtain a sufficient effect of improving the surface hardness of a portion requiring wear resistance, and to improve the characteristics of the welded portion more than ever. And it aims at providing the manufacturing method of the composite steel component which can abolish the carbon-proof process at the time of manufacture completely.
- a method of manufacturing a composite steel part formed by connecting a plurality of steel parts by welding It has a cylindrical portion having a cylindrical shape and a flange portion extending radially outward from one end of the cylindrical portion, and the cylindrical portion is a carburized and quenched portion subjected to carburizing and quenching hardening treatment, and
- the excess part more than the thickness of the carburized layer formed in the subsequent carburizing step is welded.
- a carburizing step in which the intermediate product is heated to a temperature above the austenitizing temperature in a carburizing atmosphere to form a carburized layer on the surface; Subsequent to the carburizing step, the intermediate product is cooled at a cooling rate slower than the cooling rate at which martensite transformation is performed, and the intermediate product is cooled to a temperature equal to or lower than the temperature at which the structural transformation by cooling is completed, A quenching step in which a desired portion of the cylindrical portion of the intermediate product is heated to austenite region by high density energy and then cooled by a cooling rate equal to or higher than a cooling rate at which martensite transformation is performed, and a carburized quenching portion is formed in the desired portion; A cutting step of cutting the surplus portion of the intermediate product, Next, a welding process is performed in which the second steel part is brought into contact with and welded to the welding portion of the flange portion of the obtained first steel part to perform a welding process for connecting the two steel parts. It is
- the second aspect of the present invention is a composite steel part formed by connecting a plurality of steel parts by welding
- the first steel part has a cylindrical portion having a cylindrical shape, and a flange portion extending radially outward from one end of the cylindrical portion
- the cylindrical part is composed of a carburized and quenched part whose surface layer part is composed of a martensite structure and whose interior is composed of a bainite structure
- the flange portion has a welded portion welded to the second steel part
- the weld includes a melt resolidification portion and a heat affected zone adjacent to the melt resolidification portion
- the molten re-solidified part is composed of a martensite / bainite / pearlite structure
- the heat affected zone is composed of a bainite / ferrite / pearlite structure.
- the carburizing step and the cooling step are performed using the intermediate product having the surplus portion. Then, while performing the said quenching process locally with respect to the part which should be used as a carburizing quenching part, the cutting process which removes the said excess part is performed. Note that either the quenching process or the cutting process may be performed first.
- the carburizing and quenching part locally performs the quenching process using high-density energy, thereby suppressing the generation of distortion and having a high hardness surface state with excellent wear resistance and toughness.
- a carburized and quenched part having an excellent interior can be obtained.
- the overall shape of the first steel part can suppress cooling distortion and maintain good dimensional accuracy by carrying out the cooling step in which the cooling rate is limited without quenching after the carburizing step. it can.
- the manufacturing method when the first steel part is obtained, a sufficient surface hardness improvement effect can be obtained at a portion where wear resistance is required, and the weldability of the planned welded portion can be improved. It can be improved as described above, and the carbon-proofing process at the time of manufacture can be completely abolished.
- the composite steel part of the second aspect can be easily manufactured by applying the above manufacturing method, for example.
- the cylindrical part which consists of the carburizing quenching part of the said specific structure exhibits the outstanding wear resistance
- the weld part which consists of a specific structure in the said flange part has the outstanding characteristic.
- FIG. Sectional drawing of the 1st steel component in Example 1 (AA sectional view taken on the line AA in FIG. 1). 2 is a cross-sectional view of an intermediate member in Embodiment 1.
- FIG. 3 is an explanatory diagram showing a structure state immediately after the quenching process in Example 1. Explanatory drawing which shows the structure
- Explanatory drawing which shows the structure
- Explanatory drawing which shows the welding position of the 1st steel component and 2nd steel component in Example 1.
- FIG. Explanatory drawing which shows the structure
- FIG. Explanatory drawing which shows the structure of the assembly part which integrated the composite steel part formed by welding the 1st steel part and the 2nd steel part in Example 1.
- the carburizing step is preferably performed in a low oxygen carburizing atmosphere having an oxygen concentration lower than that of the atmosphere.
- a specific method for example, there is a method performed in a carburized gas under a reduced pressure that is reduced to a pressure lower than the atmospheric pressure. That is, it is effective to employ a reduced pressure carburizing process.
- the carburizing process can be performed with a relatively small amount of carburizing gas while maintaining the inside of the high-temperature carburizing furnace in a reduced pressure state, so that the carburizing process can be performed more efficiently than before.
- the treatment time can be shortened, energy consumption can be reduced, and the carburizing and quenching equipment itself can be downsized.
- the amount of oxygen in the atmosphere can be kept low by reducing the carburizing atmosphere to atmospheric pressure in the carburizing process. Thereby, grain boundary oxidation of the carburized layer can be prevented.
- the carburizing method performed in a carburizing atmosphere having a lower oxygen concentration than the atmosphere is not limited to the above-described reduced-pressure carburizing method, for example, by filling nitrogen gas or inert gas without reducing the atmosphere, A method of preventing grain boundary oxidation of the carburized layer by keeping the oxygen amount low can also be adopted.
- the reduced-pressure carburizing is also called vacuum carburizing, and is a carburizing process in which the atmosphere in the furnace is reduced and a hydrocarbon-based gas (such as methane, propane, ethylene, acetylene, etc.) is directly inserted into the furnace as the carburizing gas. is there.
- the reduced-pressure carburizing process involves a carburizing period in which active carbon generated by decomposition when carburizing gas comes into contact with the steel surface becomes carbide on the steel surface and is stored in the steel, and the carbide decomposes. , And the diffusion period in which the stored carbon is dissolved in the matrix and diffuses toward the inside.
- the supply route of carbon is not limited to the route via the carbide, but also the route that directly dissolves in the matrix.
- the carburizing step is preferably performed under reduced pressure conditions of 1 to 100 hPa. If the reduced pressure during carburizing in the reduced pressure carburizing process is less than 1 hPa, there is a possibility that an expensive facility is required to maintain the degree of vacuum. On the other hand, when it exceeds 100 hPa, soot may be generated during carburizing, which may cause a problem of uneven carburization concentration.
- hydrocarbon-type gas such as acetylene, propane, butane, methane, ethylene, ethane, can be applied, for example.
- the steel material for the steel part it is preferable to use a low carbon steel or a low carbon alloy steel having a carbon content of about 0.30% by mass or less.
- low carbon steel with few alloying elements from the viewpoint of cost or reduction of consumption of rare elements.
- the first steel part 8 manufactured in this example is a steel part incorporated in an automatic transmission for an automobile, and includes a cylindrical part 81 having a cylindrical shape and one end of the cylindrical part 81. And a flange portion 82 extending radially outward from the part.
- the first steel part 8 is a carburized and quenched part in which the cylindrical part 81 has been subjected to carburizing and quenching hardening treatment, and the welded part scheduled to be welded to the second steel part on the flange part 82. 825.
- the other end of the cylindrical portion 81 is provided with two notches 815 in the circumferential direction.
- an intermediate product 800 prepared by using a low carbon steel having a carbon content of 0.15 mass% as a raw material through a hot forging process and a cutting process is prepared. To do.
- this intermediate product 800 as shown in FIG. 3, the shape of the planned welding portion 825 is added to the final desired shape indicated by the broken line K with an excess portion 826 that is equal to or greater than the thickness of the carburized layer formed in the subsequent carburizing step. It is a shape.
- a carburizing step is performed in which the intermediate product 800 is heated to the austenitizing temperature or higher in a carburizing atmosphere to form a carburized layer on the surface.
- a cooling step is performed in which the intermediate product 800 is cooled at a cooling rate slower than the cooling rate at which martensite transformation is performed, and the intermediate product 800 is cooled to a temperature below the temperature at which the structural transformation by cooling is completed. To do.
- a quenching process is performed in which the entire cylindrical portion 81, which is a portion to be carburized and quenched in the intermediate product 800, is heated to the austenite region by high-density energy and then cooled at a cooling rate equal to or higher than a cooling rate at which martensite transformation is performed. .
- the heat treatment equipment 5 for performing the intermediate product 800 from the carburizing step to the quenching step, specific heat treatment conditions, and the like will be briefly described.
- the heat treatment equipment 5 includes a pre-washing tank 51 for washing steel parts before carburizing and quenching, a heating chamber 521, a reduced pressure carburizing chamber 522, and a reduced pressure carburizing and cooling chamber 523.
- a cooling device 52, an induction hardening machine 53, and a magnetic flaw detector 54 for inspecting defects are provided.
- the carburizing process of this example performed using the heat treatment equipment 5 is a reduced-pressure carburizing process performed in a carburizing gas under reduced pressure that is reduced to a pressure lower than atmospheric pressure.
- the heat pattern A in this process is shown in FIG. In the figure, time is plotted on the horizontal axis and temperature is plotted on the vertical axis.
- the heat pattern A in the carburizing process was heated to the carburizing temperature in the temperature rising region a, and then kept constant in the holding regions b1 and b2.
- the holding temperature was fixed at 950 ° C., which is a temperature higher than the austenitizing temperature.
- the first area b1 of the holding area is a carburizing period area in the carburizing process, and the subsequent area b2 is a diffusion period area in the carburizing process.
- the reduced pressure carburizing treatment was performed under a reduced pressure condition of 1 to 3.5 hPa, and acetylene was used as the carburizing gas in the region b1 in the carburizing period.
- a cooling region c as a cooling process is performed.
- a reduced pressure gradual cooling process was adopted, and the reduced pressure condition was 600 hPa.
- the cooling atmosphere gas was nitrogen (N 2 ).
- the cooling rate in the reduced pressure gradual cooling step is from 0.1 to 3.0 ° C./second until the temperature is higher than the austenitizing temperature immediately after the carburizing process and reaches 150 ° C. lower than the A1 transformation point.
- the condition was within the range. Note that the heat pattern A and other conditions shown here are only examples, and can be changed to conditions optimal for steel parts to be processed by a preliminary test or the like as appropriate.
- the quenching process of this example performed after the cooling process employs high frequency heating as the heating means and water cooling as the rapid cooling means.
- This heat pattern B is shown in FIG. In the figure, time is plotted on the horizontal axis and temperature is plotted on the vertical axis.
- the entire cylindrical portion 81 is heated to a temperature equal to or higher than the austenitizing temperature by high-frequency heating, and then rapidly cooled critical cooling that undergoes martensitic transformation in the carburized layer.
- a quenching region d2 in which water and water containing quenching inhibitors are injected to quench the water.
- the heat pattern B can be changed to an optimum condition for the steel part to be processed by a preliminary test or the like as appropriate.
- the shape of the planned welding portion 825 has a shape in which the surplus portion 826 is added.
- the internal structure before the carburizing process is in a state of being subjected to plastic working in the same manner as a normal steel part after hot forging.
- the entire intermediate product 800 has an austenite structure.
- the surface layer portion of the intermediate product 800 becomes a high carbon concentration carburized layer 88 (see FIG. 4) in which the carbon concentration is higher than that of the base material.
- the intermediate product 800 in the austenite structure state is subjected to a subsequent reduced pressure slow cooling step to become a ferrite pearlite structure FP other than the carburized layer 88, and the surface carburized layer 88 is a pearlite structure P. Become.
- the cylindrical portion 81 of the intermediate product 800 is heated by high-frequency heating to be in an austenite structure state.
- the carburized layer 88 becomes the martensite structure M and the inside thereof becomes the bainite structure B.
- the flange portion 82 not subjected to the quenching process maintains the state in which the carburized layer 88 of the surface layer has the pearlite structure P and the inside remains as the ferrite pearlite structure FP.
- the surplus part 826 including the carburized layer 88 is removed from the planned welding part 825 in the flange part 82 of the intermediate product 800 by performing a cutting process.
- the first steel part 8 having the final shape is obtained.
- the welding planned part 825 of the 1st steel component 8 will be in the state which the ferrite pearlite structure
- it is effective to improve the overall product quality by performing a polishing process or a grinding process before or after the cutting process to further improve the overall dimensional accuracy and finally perform cleaning.
- a comparative component 9 obtained by a conventional manufacturing method was prepared.
- the comparative part 9 is subjected to a carburizing treatment that covers the surface of the flange portion 92 with a carburizing agent, and then a carburizing and quenching process is performed. Thereafter, the carburizing agent is removed by shot blasting, and a finishing process such as polishing is performed. It has been applied.
- the surface layer of the cylindrical portion 91 that has not been subjected to the carburizing treatment is a carburized layer 98 and has a martensite structure M. Is the bainite structure B.
- the hardness of each part of the first steel part 8 and the comparative part 9 was measured in cross section.
- the hardness of the portion of the martensite structure M in the carburized layer 88 (FIG. 6) of the cylindrical portion 81 of the first steel part 8 is in the range of HV 756 to 820 in terms of Vickers hardness, and is found to be very high hardness. It was.
- the portion composed of the bainite structure B inside the cylindrical portion 81 of the first steel part 8 is in the range of HV331 to 459 in terms of Vickers hardness, and has an appropriate hardness and excellent toughness. I understood.
- the portion of the ferrite pearlite structure FP including the planned welding portion 825 in the flange portion 82 of the first steel part 8 is in the range of HV154 to 163 in Vickers hardness, and is relatively low in hardness.
- the portion made of the pearlite structure P of the carburized layer 88 of the surface layer of the portion 82 has a slightly high hardness, and the Vickers hardness was in the range of HV298-311.
- the hardness of the martensite structure M portion in the carburized layer 98 (FIG. 10) of the cylindrical portion 91 is in the range of HV765 to 787 in terms of Vickers hardness, which is very high.
- the part of the comparative part 9 made of the bainite structure B inside the cylindrical portion 91 and the entire flange portion 92 was in the range of HV282 to 332 in terms of Vickers hardness.
- the cylindrical part 81 of the first steel part 8 has an equivalent surface hardness of the cylindrical part 81 compared to the comparative part 9, It was found that excellent wear resistance characteristics were maintained.
- the weldability of the first steel part 8 and the comparative part 9 was evaluated. Specifically, as shown in FIG. 11, a second steel part 71 to be welded to the planned welding portion 825 was prepared, and the welded part W was actually subjected to arc welding to obtain a composite steel part 75. And about the welding part 750, the sleeve welding strength confirmation test (A load is applied to a welding location and the intensity
- the welded part 750 of the composite steel part 75 produced from the first steel part 8 and the second steel part 71 includes a molten resolidified part 751 and a heat affected part 752 adjacent thereto.
- the melt resolidified portion 751 has a martensite bainite pearlite structure MBP, that is, a structure in which a martensite structure, a bainite structure, and a pearlite structure are mixed.
- the heat-affected zone 752 has a bainite / ferrite / pearlite structure BFP, that is, a structure in which a bainite structure, a ferrite structure, and a pearlite structure are mixed.
- the periphery of the heat affected zone 752 is composed of the ferrite / pearlite structure FP of the original planned welded portion 825.
- the structure of the other part of the first steel part 8 is the same as before the welding process.
- the structure around the welded portion 750 in the second steel part 71 is made of a ferrite / pearlite structure FP.
- FIG. 13 shows an assembled part 7 in which a composite steel part 75 formed by connecting the second steel part 71 and the first steel part 8 via a welded portion 750 is incorporated.
- the assembly part 7 is a torque converter (T / C) incorporated in an automatic transmission for automobiles.
- the first steel part 8 is a part called a pump impeller hub in the assembly part 7.
- the cylindrical part 81 needs to have excellent wear resistance, and the flange part 82 has a pump shell which is the second steel part 71. And excellent weldability.
- the first steel part 8 of the above embodiment and the composite steel part 75 formed by welding this to the second steel part 71 sufficiently have the required quality and exhibit excellent performance. .
- the first steel part 8 is not limited to the pump impeller hub, and may be any part having a cylindrical part and a flange part.
- the first steel part 8 may be a power transmission shaft such as an input shaft and an output shaft in an automobile automatic transmission. Good.
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Abstract
Description
一方、上記第1の鋼部品のフランジ部は第2の鋼部品と溶接される溶接予定部を有しており、この溶接予定部は溶接性確保のために浸炭処理を施さないことが求められる。
円筒形状を呈する円筒部と、該円筒部の一端から径方向外方に延設されたフランジ部とを有し、上記円筒部が浸炭焼き入れ硬化処理を施した浸炭焼入部であると共に、上記フランジ部に第2の鋼部品との溶接が予定されている溶接予定部を有する第1の鋼部品を製造するに当たり、その後の浸炭工程において形成される浸炭層の厚み以上の余剰部を上記溶接予定部に加えた中間品を準備し、
該中間品を浸炭雰囲気中においてオーステナイト化温度以上に加熱して表面に浸炭層を形成する浸炭工程と、
該浸炭工程に引き続き、マルテンサイト変態する冷却速度よりも遅い冷却速度により上記中間品を冷却し、かつ、冷却による組織変態が完了する温度以下まで上記中間品を冷却する冷却工程と、
高密度エネルギーによって上記中間品の上記円筒部の所望部分をオーステナイト領域まで加熱した後にマルテンサイト変態する冷却速度以上の冷却速度により冷却し、上記所望部分に浸炭焼入部を形成する焼き入れ工程と、
上記中間品の上記余剰部を切削する切削工程とを行い、
次いで、得られた上記第1の鋼部品の上記フランジ部における上記溶接予定部に第2の鋼部品を当接させて溶接することにより両者を連結する溶接工程を行うことを特徴とする複合鋼部品の製造方法にある。
第1の鋼部品が、円筒形状を呈する円筒部と、該円筒部の一端から径方向外方に延設されたフランジ部とを有し、
上記円筒部は、その表層部がマルテンサイト組織からなると共に内部がベイナイト組織からなる浸炭焼入部からなり、
上記フランジ部は、第2の鋼部品と溶接された溶接部を有し、
該溶接部は、溶融再凝固部と、該溶融再凝固部に隣接する熱影響部とを備え、
上記溶融再凝固部はマルテンサイト・ベイナイト・パーライト組織からなり、上記熱影響部はベイナイト・フェライト・パーライト組織からなることを特徴とする複合鋼部品にある。
また、上記第1の鋼部品の全体形状は、上記浸炭工程後に急冷することなく冷却速度を制限した上記冷却工程を実施することにより、冷却歪みが抑制され、寸法精度を良好に維持することができる。
また、上記浸炭ガスとしては、例えば、アセチレン、プロパン、ブタン、メタン、エチレン、エタン等の炭化水素系のガスを適用することができる。
上記複合鋼部品及びその製造方法に係る実施例につき、図を用いて説明する。
本例において製造する第1の鋼部品8は、図1及び図2に示すごとく、自動車用自動変速機に組み込まれる鋼部品であって、円筒形状を呈する円筒部81と、円筒部81の一端から径方向外方に延設されたフランジ部82とを有する部品である。そして、第1の鋼部品8は、円筒部81が浸炭焼き入れ硬化処理を施した浸炭焼入部であると共に、フランジ部82に、第2の鋼部品との溶接が予定されている溶接予定部825を有する。また、上記円筒部81における他端には、周方向に2箇所の切り欠き部815が設けられている。
次に、この浸炭工程に引き続き、マルテンサイト変態する冷却速度よりも遅い冷却速度により中間品800を冷却し、かつ、冷却による組織変態が完了する温度以下まで中間品800を冷却する冷却工程を実施する。
以下、さらに詳説する。
図7に示すごとく、熱処理設備5は、浸炭焼入れ処理前に鋼部品を洗浄するための前洗槽51と、加熱室521、減圧浸炭室522、および減圧徐冷室523を備えた減圧浸炭徐冷装置52と、高周波焼き入れ機53と、欠陥を検査するための磁気探傷装置54とを備えたものである。
まず、中間品800は、図3に示すごとく、溶接予定部825の形状が、余剰部826を加えた形状を呈している。浸炭工程前の内部組織は、熱間鍛造を終えた通常の鋼部品と同様に、塑性加工が施された組織状態となっている。浸炭工程を施すことによって、中間品800の全体がオーステナイト組織となる。なお、このとき、中間品800の表層部は、炭素濃度が母材よりも高くなった高炭素濃度の浸炭層88(図4参照)となる。
比較部品9は、フランジ部92の表面を防炭剤で覆う防炭処理を施した後、浸炭焼き入れ処理を実施し、その後ショットブラストによって防炭剤を除去し、さらに研磨等の仕上げ処理を施したものである。図10に示すごとく、比較部品9は、防炭処理を施していなかった円筒部91の表面層が浸炭層98となっていると共にマルテンサイト組織Mとなっており、その内部及びフランジ部92全体がベイナイト組織Bとなっている。
第1の鋼部品8の円筒部81の浸炭層88(図6)におけるマルテンサイト組織Mの部分の硬度は、ビッカース硬さにおいてHV756~820の範囲にあり、非常に高硬度であることが分かった。また、第1の鋼部品8の円筒部81の内部のベイナイト組織Bよりなる部位は、ビッカース硬さにおいてHV331~459の範囲にあり、適度な硬度を有し、靱性にも優れる範囲にあることがわかった。さらに、第1の鋼部品8のフランジ部82における溶接予定部825を含むフェライト・パーライト組織FPの部分は、ビッカース硬さにおいてHV154~163の範囲にあり、比較的低硬度であり、一方、フランジ部82の表層の浸炭層88のパーライト組織Pよりなる部分は若干硬度が高く、ビッカース硬さにおいてHV298~311の範囲にあった。
試験の結果、スリーブ溶接強度確認試験においては比較部品9と同等以上の溶接部強度が実現できていることが分かった。また、両者ともリークテストにおいても問題は発生しなかった。これらの結果から、第1の鋼部品8の溶接性は比較部品9と同等以上であることが分かった。
Claims (3)
- 複数の鋼部品を溶接により連結してなる複合鋼部品を製造する方法において、
円筒形状を呈する円筒部と、該円筒部の一端から径方向外方に延設されたフランジ部とを有し、上記円筒部が浸炭焼き入れ硬化処理を施した浸炭焼入部であると共に、上記フランジ部に第2の鋼部品との溶接が予定されている溶接予定部を有する第1の鋼部品を製造するに当たり、その後の浸炭工程において形成される浸炭層の厚み以上の余剰部を上記溶接予定部に加えた中間品を準備し、
該中間品を浸炭雰囲気中においてオーステナイト化温度以上に加熱して表面に浸炭層を形成する浸炭工程と、
該浸炭工程に引き続き、マルテンサイト変態する冷却速度よりも遅い冷却速度により上記中間品を冷却し、かつ、冷却による組織変態が完了する温度以下まで上記中間品を冷却する冷却工程と、
高密度エネルギーによって上記中間品の上記円筒部の所望部分をオーステナイト領域まで加熱した後にマルテンサイト変態する冷却速度以上の冷却速度により冷却し、上記所望部分に浸炭焼入部を形成する焼き入れ工程と、
上記中間品の上記余剰部を切削する切削工程とを行い、
次いで、得られた上記第1の鋼部品の上記フランジ部における上記溶接予定部に第2の鋼部品を当接させて溶接することにより両者を連結する溶接工程を行うことを特徴とする複合鋼部品の製造方法。 - 請求項1に記載の複合鋼部品の製造方法において、上記浸炭工程は、大気より酸素濃度が低い低酸素浸炭雰囲気中において行うことを特徴とする複合鋼部品の製造方法。
- 複数の鋼部品を溶接により連結してなる複合鋼部品であって、
第1の鋼部品が、円筒形状を呈する円筒部と、該円筒部の一端から径方向外方に延設されたフランジ部とを有し、
上記円筒部は、その表層部がマルテンサイト組織からなると共に内部がベイナイト組織からなる浸炭焼入部からなり、
上記フランジ部は、第2の鋼部品と溶接された溶接部を有し、
該溶接部は、溶融再凝固部と、該溶融再凝固部に隣接する熱影響部とを備え、
上記溶融再凝固部はマルテンサイト・ベイナイト・パーライト組織からなり、上記熱影響部はベイナイト・フェライト・パーライト組織からなることを特徴とする複合鋼部品。
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JP2000063952A (ja) * | 1998-07-29 | 2000-02-29 | Daimlerchrysler Ag | 中空軸の製造方法 |
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JPH01127661A (ja) * | 1987-11-10 | 1989-05-19 | Mitsubishi Motors Corp | 浸炭焼入部品の浸炭抜き方法 |
JPH0841531A (ja) * | 1994-07-27 | 1996-02-13 | Nippon Seiko Kk | 案内軸受部品の焼き入れ方法 |
JP2000063952A (ja) * | 1998-07-29 | 2000-02-29 | Daimlerchrysler Ag | 中空軸の製造方法 |
JP2002167658A (ja) * | 2000-11-30 | 2002-06-11 | Chugai Ro Co Ltd | 鋼材部品の真空浸炭方法 |
JP2008069422A (ja) * | 2006-09-15 | 2008-03-27 | Sumikin Seiatsuhin Kogyo Kk | 鍛造部品の製造方法 |
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