CN114908242A - Film-like retained austenite control method suitable for heavy-load carburized gear - Google Patents
Film-like retained austenite control method suitable for heavy-load carburized gear Download PDFInfo
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- 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
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- 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
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- C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
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- C21D2211/00—Microstructure comprising significant phases
- C21D2211/001—Austenite
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- C21D2211/002—Bainite
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- C21D2211/00—Microstructure comprising significant phases
- C21D2211/008—Martensite
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Abstract
A film-shaped retained austenite control method suitable for a heavy-duty carburized gear belongs to the technical field of heat treatment structure control of heavy-duty carburized gears. The method comprises the following steps of combining chemical components of the heavy-duty gear and phase change rules of austenite with different carbon contents after carburization of the heavy-duty gear, and controlling the tissue structure of the heavy-duty carburized gear by optimizing a heat treatment process to obtain a complex-phase structure with a gear carburized layer mainly containing martensite and containing 1-10% of film-shaped retained austenite; the intermediate transition zone is a mixed structure of twin crystal martensite and lath martensite; the core is a gradient structure of low-carbon lath martensite or lower bainite. By controlling the content and the form of the retained austenite, the heavy-load gear component has high wear resistance, high bearing capacity and high fatigue performance, and the quality consistency, the size and the precision stability of the heavy-load gear component are obviously improved.
Description
Technical Field
The invention belongs to the technical field of heavy-duty carburized gear heat treatment structure control, and particularly relates to a film-shaped residual austenite content control method for a heavy-duty carburized gear.
Background
The heavy-duty carburized gear is a key for determining the bearing capacity and service life of a transmission device, is widely applied to various transmission devices, such as heavy-duty special vehicle transmission devices, aircraft engine transmission devices, ship power system transmission devices, engineering machinery transmission devices, wind power gear boxes, high-speed trains and the like, and is a core component for ensuring the safety and reliability of the transmission devices. The heavy-duty carburized gear is in service in the environment with wide load range, wide temperature range, strong impact and complex vibration, and requires the parts to have the comprehensive properties of high surface hardness, high wear resistance and high core toughness.
The components of the steel material are the basis for determining the structure performance of the steel material, the heat treatment process is the key for obtaining reasonable structure performance, and the reasonable structure performance is an important factor for influencing the performance of the heavy-duty carburized gear. The heavy-duty carburized gears in all countries in the world are mainly made of Cr-Ni-Mo, Japan is mainly made of Cr-Mo, Germany is mainly made of Mn-Cr, and China is mainly made of heavy-duty carburized gears made of Cr-Ni-Mo, Cr-Mo, Mn-Cr-Ti and the like. At present, 20Cr2Ni4A, 20CrNiMoA, 17Cr2Ni2MoVNb, 18Cr2Ni4WA and other materials are generally selected for manufacturing the heavy-duty carburized gear in China, and the manufacturing process route is as follows: blanking → forging → normalizing + tempering → rough machining → thermal refining → rough machining → carburizing → high temperature tempering → quenching → low temperature tempering → sand blasting/shot blasting → fine machining → finished product warehousing, wherein the carburizing, quenching and tempering process is the key for influencing the comprehensive performance of the heavy-duty carburized gear.
Carburizing is a common surface strengthening means for heavy-duty gears, and a gear part is subjected to carburizing treatment after rough machining, so that the carbon content of the surface is increased to 0.80-1.20%, and the carbon content distribution gradient which gradually decreases from the surface to the core part is obtained; then quenching to obtain a mixed structure of high-hardness twin crystal martensite and residual austenite on the surface of the gear part by carburizing; twin crystal martensite and lath martensite are obtained in the transition region; the core part obtains a mixed structure of lath martensite and lower bainite, and further, the aims of high wear resistance, high bearing capacity, high fatigue performance, high precision and high quality consistency of the gear part are achieved. After the treatment, the stability of austenite can be obviously improved by the higher surface carbon content of the surface of the heavy-duty gear, and because the previously transformed austenite has an inhibiting effect on the untransformed austenite, after the gear part is cooled to room temperature, the surface carburized layer still has more residual austenite which is mainly block-shaped residual austenite, as shown in fig. 1.
The block retained austenite is in a face-centered cubic structure and has the characteristics of low hardness, low strength, instability and the like, so that the existence of the block retained austenite can reduce the hardness, the strength and the wear resistance of materials, and can influence the mechanical properties of parts such as strength, plasticity, toughness, fatigue and the like, and the block retained austenite can be transformed into martensite and film-shaped retained austenite along with the prolonging of time in the use process of the parts, and the macroscopic volume of a heavy-duty gear can be changed in the transformation process, so that the precision of the workpiece is reduced and the size of the workpiece is unstable.
Taking a heavy duty gear manufactured by selecting 20Cr2Ni4A and 17Cr2Ni2MoVNb steel as an example, the volume fraction of the retained austenite in a carburized layer after carburization and the form thereof are calculated by performing X-ray diffraction measurement by using a Co-Kalpha target, and the volume fraction of the retained austenite is calculated by using formula (1) and combining diffraction peak values of (110) alpha (200) alpha (211) alpha and (111) gamma (200) gamma (220) gamma (311) gamma, wherein V gamma is the volume fraction of the retained austenite.
V γ ═ 1.4I γ/(I α +1.4I γ) formula (1)
As can be seen from fig. 2 and 3, the residual austenite content of the carburized layer on the surface of the heavy-duty carburized gear is 15% to 30%, the wear resistance of the carburized layer is affected by the low surface hardness due to the presence of a large amount of massive residual austenite, and the dimensional accuracy and quality stability of the carburized layer are affected by the strain-induced martensite transformation during the service of the heavy-duty gear, which may lead to early fracture failure of the heavy-duty gear. Therefore, the method eliminates the blocky retained austenite of the carburized surface layer of the heavy-duty gear after carburization, reasonably controls the form and the content of the retained austenite, and is the key for obtaining heavy-duty gear parts with high bearing capacity, high fatigue life and high quality consistency.
At present, most of the ideas suggest that residual austenite in microstructure cannot be completely eliminated for high carbon content materials. The applicant believes that the retained austenite cannot be completely eliminated, but the content and the form of the retained austenite are controllable, so that a large amount of massive retained austenite is further transformed into martensite and film-shaped retained austenite, a smaller and more uniformly distributed lath martensite structure can be obtained, precipitation of nano-scale ultra-fine dispersion carbide can be promoted, the remaining film-shaped retained austenite is in an equiaxial compressive stress state, and when the remaining film-shaped retained austenite exists in the middle of lath martensite, the structure is stable, the plastic deformation is not easy to occur, and the retained austenite can exist in a toughness phase in the service process, so that the stress is relieved, and the fatigue crack expansion is prevented. Meanwhile, due to the existence of martensite formed secondarily and nano-scale carbides distributed in a dispersed mode, residual compressive stress can be generated on the surface when the heavy-duty gear is restored to the room temperature state, the damage of defects to the local strength of the material can be relieved due to the residual compressive stress, and finally the bearing capacity and the wear resistance are improved.
Disclosure of Invention
The invention aims to provide a residual austenite control method suitable for a heavy-duty carburized gear, which combines the chemical components of the heavy-duty gear and the phase transition rule of austenite with different carbon contents after carburization, controls the tissue structure of the heavy-duty carburized gear by optimizing a heat treatment process, changes the form of the residual austenite and reduces the content of the residual austenite, and obtains a complex phase structure of which a gear carburized layer is mainly martensite and contains 1-10% of film-shaped residual austenite; the intermediate transition zone is a mixed structure of twin crystal martensite and lath martensite; the core is a gradient structure of low-carbon lath martensite or lower bainite. Not only can increase the surface hardness and improve the wear resistance, but also can improve the bearing capacity, the fatigue life, the precision stability and the quality consistency of parts. By controlling the content and the form of the retained austenite, the heavy-load gear component has high wear resistance, high bearing capacity and high fatigue performance, and the quality consistency, the size and the precision stability of the heavy-load gear component are obviously improved.
Technical scheme of the invention
The invention completes the control of the retained austenite of the heavy-duty carburized gear by the following method: taking a hot-rolled steel bar (selected from heavy-duty carburized gear steel such as 20Cr2Ni4A, 17Cr2Ni2MoVNb, 20CrNiMoA, 18Cr2Ni4WA and the like), roughly processing the steel bar into a gear blank, and then carrying out heat treatment according to the following sequence:
step 1) carburizing: the gas carburizing process or the low-pressure pulse carburizing process can be selected.
The gas carburizing process comprises the following steps: carburizing the gear blank by adopting an easily-Presson controllable atmosphere multipurpose furnace, and introducing a mixed carburizing medium of 200L (160 +/-5 kg) propane and 20L BH-5 direct-growing type energizer into a carburizing furnace for carburizing according to the flow of 0.5-1.0L/h; strong infiltration period: carburizing at 930 +/-10 ℃ for 170 +/-5 min, wherein the carbon potential is 1.00-1.10 wt%; and (3) diffusion period: and (3) carburizing at 890 +/-10 ℃, with the carbon potential of 0.85-0.90 wt% for 120min +/-5 min, cooling to 400 +/-5 ℃ along with the furnace after carburizing, and discharging and air cooling.
The low-pressure pulse carburizing process comprises the following steps: and (2) carburizing the gear blank by adopting an ALD (atomic layer deposition) low-pressure high-temperature carburizing furnace, introducing acetylene into the carburizing furnace for carburizing at the flow rate of 128-130L/h, wherein the carburizing temperature is 950 +/-10 ℃, introducing an acetylene medium nine times in a strong carburizing period, wherein the first medium introduction time is 160s +/-2 s, the rest introduction time is 45s +/-2 s, the strong carburizing time is 90min +/-3 min, the diffusion time is 50min +/-3 min, cooling to 400 +/-5 ℃ along with the furnace after carburizing is finished, and discharging and air cooling.
Step 2) fine machining:
and (3) tempering the carburized heavy-duty gear blank at the high temperature of 680 +/-10 ℃, air cooling, and then performing finish machining according to the size requirement of the part.
Step 3) quenching:
and carrying out sectional quenching treatment on the gear after finish machining. The quenching temperature is 880 +/-10 ℃ and is kept for 30-35 min, the steel plate is cooled to 450 +/-5 ℃ at a cooling rate of more than or equal to 20 ℃/s after the heat preservation is finished, the steel plate is cooled to room temperature at a cooling rate of more than or equal to 10 ℃/s below 450 +/-5 ℃, and the quenching medium can be nitrogen or quenching oil.
Step 4), low-temperature tempering:
after gear quenching is finished, tempering treatment is finished in 24 hours by using a well type tempering furnace or a box type tempering furnace, wherein the tempering temperature is 200 +/-5 ℃, and the tempering time is 240 +/-10 min.
Step 5) deep cooling treatment:
after the gear tempering is finished, liquid nitrogen is used for carrying out cryogenic treatment at the cryogenic temperature of minus 150 +/-10 ℃ for 120min +/-5 min, and then the cryogenic treatment is carried out, and then the low-temperature tempering treatment at the cryogenic temperature of minus 150 +/-10 ℃ is carried out for 120min +/-5 min.
The cryogenic medium selected for the cryogenic treatment is liquid nitrogen, and the aim is to convert 15-30% of block residual austenite into 1-10% of film-shaped residual austenite and secondary martensite, so that a carburized layer of the heavy-duty carburized gear is made into a complex-phase structure which is mainly martensite and contains 1-10% of film-shaped residual austenite; the intermediate transition zone adopts a mixed structure of twin martensite and lath martensite; the core is a gradient structure of low-carbon lath martensite or lower bainite.
Advances in the invention
The microstructure of a carburized layer on the surface of a heavy-duty carburized gear is controlled by optimizing a heat treatment process, 15-30% of residual austenite is further converted into 1-10% of film-shaped residual austenite and martensite is secondarily refined, and the carburized layer obtains a complex phase structure which mainly comprises the martensite and contains 1-10% of film-shaped residual austenite; the intermediate transition zone adopts a mixed structure of twin martensite and lath martensite; the core is a gradient structure of low carbon lath martensite or lower bainite. The film-shaped residual austenite exists between the martensite laths, can exist in a toughness phase in the service process of the heavy-duty gear, and plays a role in relieving stress and preventing fatigue crack propagation. Meanwhile, the invention adds a cryogenic treatment process and adopts liquid nitrogen as a cooling medium. The liquid nitrogen is a byproduct of industrial oxygen generation, has wide source, easy storage, high chemical stability, no damage to parts, no toxicity or corrosion, no pollution to gear parts, economy and convenience, and is a green technology.
Drawings
FIG. 1 is a diagram showing a twin martensite + thin film retained austenite structure.
FIG. 2 is a diagram of a twin crystal martensite + massive retained austenite structure.
FIG. 3 is a graph of the retained austenite content of a bull gear made of 20Cr2Ni4A steel.
FIG. 4 is a graph of the retained austenite content of a bull gear made of 17Cr2Ni2MoVNb steel.
Detailed Description
The present invention will be further described with reference to the following specific embodiments. It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure herein. 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 application belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
Example 1
Hot rolling 20Cr2Ni4A steel bar (chemical components are C0.19-0.21%, Si 0.17-0.37%, Mn 0.30-0.60%, Cr 1.25-1.65%, Ni 3.25-3.65%, P0.010%, S0.005%) is used for blanking → forging → normalizing, rough machining → quenching and tempering → rough machining, rough machining is carried out after rough machining is carried out to heavy load gear blank:
1) the method comprises the following steps of performing gas atmosphere carburization on a heavy-duty gear blank by using an easily-Presson controlled atmosphere multipurpose furnace, introducing a mixed carburization medium of 200L propane and 20L BH-5 energizer into a carburizing furnace for carburization according to the flow of 0.8L/h, wherein the specific carburization process parameters are as follows: in the strong cementation period, the cementation temperature is 930 ℃, the carbon potential is 1.10 percent by weight, and the time is 170 min; and in the diffusion period, the carburizing temperature is 890 ℃, the carbon potential is 0.85 percent by weight, the time is 120min, the furnace is cooled to 400 ℃ after the carburizing is finished, and the furnace is taken out for air cooling.
2) And (3) tempering the heavy-duty gear blank subjected to carburization in the step at the high temperature of 680 ℃, air cooling, and then performing finish machining according to the size requirement of the part.
3) Quenching treatment: heating the finish-machined heavy-duty gear to 880 ℃ in a multi-purpose furnace in controllable atmosphere of the easily-Presson, preserving heat for 30min, introducing 20# special quenching oil, cooling to 450 ℃ at a cooling rate of 45 ℃/s, and cooling to room temperature at a cooling rate of 25 ℃/s below 450 ℃.
4) And (3) carrying out a low-temperature tempering process on the quenched heavy-duty gear: the tempering temperature is 200 ℃, and the tempering and heat preservation time is 240 min.
5) And after the heavy-duty gear is tempered, performing cryogenic treatment by using liquid nitrogen at the cryogenic temperature of-150 ℃ for 120min, and performing cryogenic tempering at the cryogenic temperature of 150 ℃ for 120min after the cryogenic treatment.
The depth of a carburized layer of the heavy-duty gear obtained by the process is 1.09mm, the hardness of a working surface is 60HRC, and a surface carburized layer is a complex phase structure which mainly contains martensite and contains 7% of thin-film residual austenite; the intermediate transition zone is a mixed structure of twin crystal martensite and lath martensite; the core part is a gradient structure mainly comprising low-carbon lath martensite, so that the fatigue strength, the service life, the precision stability and the quality consistency of the heavy-duty gear are obviously improved.
Example 2
The hot rolling is adopted to carry out blanking → forging → normalizing + tempering → rough machining → quenching and tempering → rough machining on a heavy-duty carburized gear by using a hot-rolled 17Cr2Ni2MoVNb steel bar (the chemical components are C: 0.16-0.20%, Si: 0.37% or less, Mn: 0.50-0.90%, Cr: 1.50-1.80%, Ni: 1.50-1.70%, Mo: 0.25-0.35%, Nb: 0.02-0.06%, V: 0.01-0.10%, P: 0.010% or less and S: 0.005%) to carry out the following heat treatment after the rough machining is carried out to a heavy-duty gear blank:
1) a German ALD vacuum carburizing furnace is used for carburizing the heavy-duty carburized gear, the carburizing medium is acetylene, and the specific carburizing technological parameters are as follows: the carburizing temperature is 950 ℃, the acetylene flow is 129L/h, the acetylene medium is introduced for 9 times in the strong infiltration period, wherein the introduction time of the medium for the first time is 160s, the introduction time of the rest 8 times is 45s, the strong infiltration time is 90min, the diffusion time is 50min, the furnace is cooled to 400 ℃ after the carburizing is finished, and the furnace is taken out for air cooling.
2) And (3) tempering the heavy-duty gear blank after the carburization in the step at the high temperature of 680 ℃, air cooling, and then performing finish machining according to the size requirement of the part.
3) Quenching treatment: heating the finish-machined heavy-duty gear to 880 ℃ in a Germany ALD vacuum furnace, preserving heat for 30min, introducing nitrogen for cooling after heat preservation, cooling to 450 ℃ at a cooling rate of 40 ℃/s, and cooling to room temperature at a cooling rate of 20 ℃/s below 450 ℃.
4) And (3) carrying out a low-temperature tempering process on the quenched heavy-duty gear: the tempering temperature is 200 ℃, and the tempering and heat preservation time is 240 min.
5) And after tempering the heavy-duty gear, performing cryogenic treatment by using liquid nitrogen at the cryogenic temperature of-150 ℃ for 120min, and performing cryogenic tempering at the cryogenic temperature of 150 ℃ for 120min after cryogenic treatment.
The depth of a carburized layer of the heavy-duty gear obtained by the process is 1.12mm, the hardness of a working surface is 61HRC, and a surface carburized layer is a complex phase structure which mainly contains martensite and contains 8% of thin-film residual austenite; the intermediate transition zone is a mixed structure of twin crystal martensite and lath martensite; the core is a gradient structure mainly comprising low-carbon lath martensite, so that the fatigue strength, service life, precision stability and quality consistency of the heavy-duty gear are obviously improved.
Example 3
The hot-rolled 18Cr2Ni4WA steel bar (chemical components are 0.13-0.19% of C, 0.17-0.37% of Si, 0.30-0.60% of Mn, 1.35-1.65% of Cr, 4.00-4.50% of Ni, 0.80-1.20% of W, less than or equal to 0.015% of P and less than or equal to 0.005%) is subjected to blanking → forging → normalizing + tempering → rough machining → quenching and tempering → rough machining, and after rough machining is carried out to obtain a heavy-duty gear blank, the following heat treatment is carried out:
1) the method comprises the following steps of performing gas atmosphere carburization on a heavy-duty gear blank by using an easily-Presson controlled atmosphere multipurpose furnace, introducing a mixed carburization medium of 200L propane and 20L BH-5 energizer into a carburizing furnace for carburization according to the flow of 0.75L/h, wherein the specific carburization process parameters are as follows: in the strong cementation period, the cementation temperature is 930 ℃, the carbon potential is 1.05 percent by weight, and the time is 170 min; and in the diffusion period, the carburizing temperature is 880 ℃, the carbon potential is 0.85 wt%, the time is 120min, the carburization is finished, the temperature is cooled to 400 ℃ along with the furnace, and the steel plate is taken out of the furnace and air-cooled.
2) And (3) tempering the heavy-duty gear blank after the carburization in the step at the high temperature of 680 ℃, air cooling, and then performing finish machining according to the size requirement of the part.
3) Quenching treatment: heating the finish-machined heavy-duty gear to 880 ℃ in a multi-purpose furnace in controllable atmosphere of the easily-Presson, preserving heat for 30min, introducing 20# special quenching oil, cooling to 450 ℃ at a cooling rate of 40 ℃/s, and cooling to room temperature at a cooling rate of 20 ℃/s below 450 ℃.
4) And (3) carrying out a low-temperature tempering process on the quenched heavy-duty gear: the tempering temperature is 200 ℃, and the tempering temperature is 240 min.
5) And after tempering the heavy-duty gear, performing cryogenic treatment by using liquid nitrogen at the cryogenic temperature of-150 ℃ for 120min, and performing cryogenic tempering at the cryogenic temperature of 150 ℃ for 120min after cryogenic treatment.
The depth of a carburized layer of the heavy-duty gear obtained by the process is 1.05mm, the hardness of a working surface is 61HRC, and a surface carburized layer is a complex phase structure which mainly contains martensite and contains 6 percent of film-shaped retained austenite; the intermediate transition zone is a mixed structure of twin crystal martensite and lath martensite; the core part is a gradient structure mainly comprising low-carbon lath martensite, so that the fatigue strength, the service life, the precision stability and the quality consistency of the heavy-duty gear are obviously improved.
Claims (3)
1. A method for controlling the content of film-shaped retained austenite of a heavy-duty carburized gear is characterized in that a hot-rolled steel bar is roughly processed into a gear blank and then is subjected to heat treatment; the technical parameters of the steps and the control are as follows:
step 1) carburizing: the method comprises the following steps: gas carburizing process or low-pressure pulse carburizing process
The gas carburizing process comprises the following steps: carburizing the gear blank by adopting an easily-Presson controllable atmosphere multipurpose furnace, and introducing a mixed carburizing medium of 200L propane and 20L BH-5 direct-growing type energizer into a carburizing furnace for carburizing according to the flow of 0.5-1.0L/h; and (3) a strong infiltration period: carburizing at 920-940 ℃, with the carbon potential of 1.00-1.10 wt% for 165-175 min; and (3) diffusion period: the carburizing temperature is 880-900 ℃, the carbon potential is 0.85-0.90 wt%, the time is 115-125 min, the furnace is cooled to 395-405 ℃ after the carburizing is finished, and the furnace is taken out for air cooling;
the low-pressure pulse carburizing process comprises the following steps: carburizing the gear blank by adopting an ALD (atomic layer deposition) low-pressure high-temperature carburizing furnace, introducing acetylene into the carburizing furnace for carburizing at the flow rate of 128-130L/h, wherein the carburizing temperature is 940-960 ℃, and acetylene media are introduced in nine times during the strong carburizing period, wherein the introduction time of the media for the first time is 158-162 s, the introduction time of the rest is 43-47 s, the strong carburizing time is 87-93 min, the diffusion time is 47-53 min, cooling to 395-405 ℃ along with the furnace after the carburizing is finished, and discharging and air cooling;
step 2) fine machining:
tempering the carburized heavy-duty gear blank at the high temperature of 670-690 ℃, air cooling, and then performing finish machining according to the size requirement of the part;
step 3) quenching:
and carrying out sectional quenching treatment on the gear after finish machining. The quenching temperature is 870-890 ℃, the temperature is kept for 30-35 min, the steel plate is cooled to 445-455 ℃ at a cooling rate of more than or equal to 20 ℃/s after the temperature is kept, the steel plate is cooled to room temperature at a cooling rate of more than or equal to 10 ℃/s below 445-455 ℃, and the quenching medium is nitrogen or quenching oil;
step 4), low-temperature tempering:
after gear quenching is finished, tempering treatment is finished in 24 hours by using a well type tempering furnace or a box type tempering furnace, wherein the tempering temperature is 195-205 ℃, and the tempering time is 230-250 min;
step 5) deep cooling treatment:
after the gear is tempered, liquid nitrogen is used for cryogenic treatment at the cryogenic temperature of minus 160 ℃ to minus 140 ℃ for 115min to 125min, and after the cryogenic treatment, the cryogenic treatment is carried out for cryogenic tempering at the cryogenic temperature of 145 ℃ to 155 ℃ for 115min to 125 min.
2. The method for controlling the content of the film-like retained austenite of the heavily carburized gear according to claim 1, wherein the hot-rolled steel rod in step 1) is 20Cr2Ni4A, 20CrNiMoA or 17Cr2Ni2MoVNb, 18Cr2Ni4WA gear steel.
3. The method for controlling the content of the thin-film retained austenite of the heavy-duty carburized gear according to claim 1, characterized in that in step 5), a cryogenic medium selected for cryogenic treatment is liquid nitrogen, so as to convert 15-30% of the block retained austenite into 1-10% of the thin-film retained austenite + secondary martensite, so that a carburized layer of the heavy-duty carburized gear has a complex phase structure with martensite as the main component and 1-10% of the thin-film retained austenite; the intermediate transition zone adopts a mixed structure of twin martensite and lath martensite; the core is a gradient structure of low-carbon lath martensite or lower bainite.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116497262A (en) * | 2023-06-20 | 2023-07-28 | 成都先进金属材料产业技术研究院股份有限公司 | Method for improving surface hardness of low-carbon high-alloy martensitic bearing steel |
Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103290419A (en) * | 2013-06-25 | 2013-09-11 | 清华大学 | Gear treatment method |
| CN105400944A (en) * | 2015-12-01 | 2016-03-16 | 张贺佳 | Cryogenic heat treatment technology for improving performances of countershaft gear |
| CN106222606A (en) * | 2016-08-31 | 2016-12-14 | 中车戚墅堰机车车辆工艺研究所有限公司 | A kind of process controlling the carburized workpiece non-martensite degree of depth |
| CN106756753A (en) * | 2016-12-12 | 2017-05-31 | 中车戚墅堰机车车辆工艺研究所有限公司 | The carburization quenching method of low-speed heavy-loaded gear |
| CN108660395A (en) * | 2018-05-30 | 2018-10-16 | 东北大学 | Manganese high-strength cut deal and quenching-dynamic partition production technology preparation method in a kind of 690MPa grades of low-carbon |
| CN110951962A (en) * | 2019-12-16 | 2020-04-03 | 武汉理工大学 | High-performance gear heat treatment method for realizing fine and homogenized structure |
| CN111304581A (en) * | 2020-03-21 | 2020-06-19 | 哈尔滨工程大学 | Circulating carburization treatment method for carburization layer on surface of heavy-duty gear |
-
2022
- 2022-04-14 CN CN202210391496.4A patent/CN114908242B/en active Active
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103290419A (en) * | 2013-06-25 | 2013-09-11 | 清华大学 | Gear treatment method |
| CN105400944A (en) * | 2015-12-01 | 2016-03-16 | 张贺佳 | Cryogenic heat treatment technology for improving performances of countershaft gear |
| CN106222606A (en) * | 2016-08-31 | 2016-12-14 | 中车戚墅堰机车车辆工艺研究所有限公司 | A kind of process controlling the carburized workpiece non-martensite degree of depth |
| CN106756753A (en) * | 2016-12-12 | 2017-05-31 | 中车戚墅堰机车车辆工艺研究所有限公司 | The carburization quenching method of low-speed heavy-loaded gear |
| CN108660395A (en) * | 2018-05-30 | 2018-10-16 | 东北大学 | Manganese high-strength cut deal and quenching-dynamic partition production technology preparation method in a kind of 690MPa grades of low-carbon |
| CN110951962A (en) * | 2019-12-16 | 2020-04-03 | 武汉理工大学 | High-performance gear heat treatment method for realizing fine and homogenized structure |
| CN111304581A (en) * | 2020-03-21 | 2020-06-19 | 哈尔滨工程大学 | Circulating carburization treatment method for carburization layer on surface of heavy-duty gear |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116497262A (en) * | 2023-06-20 | 2023-07-28 | 成都先进金属材料产业技术研究院股份有限公司 | Method for improving surface hardness of low-carbon high-alloy martensitic bearing steel |
| CN116497262B (en) * | 2023-06-20 | 2023-10-31 | 成都先进金属材料产业技术研究院股份有限公司 | Method for improving surface hardness of low-carbon high-alloy martensitic bearing steel |
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