CN113802085A - Micro-carburizing process for improving mechanical property of 8Cr4Mo4V steel for aeroengine bearing - Google Patents

Micro-carburizing process for improving mechanical property of 8Cr4Mo4V steel for aeroengine bearing Download PDF

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CN113802085A
CN113802085A CN202111089881.5A CN202111089881A CN113802085A CN 113802085 A CN113802085 A CN 113802085A CN 202111089881 A CN202111089881 A CN 202111089881A CN 113802085 A CN113802085 A CN 113802085A
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micro
cooling
steel
8cr4mo4v steel
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CN113802085B (en
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于兴福
申向阳
魏英华
郑冬月
安敏
赵文增
吴玉胜
苏勇
闫国斌
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Shenyang University of Technology
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    • 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
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    • 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
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    • 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
    • C21D1/26—Methods of annealing
    • C21D1/32—Soft annealing, e.g. spheroidising
    • 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
    • C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
    • 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
    • C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
    • C21D1/773—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material under reduced pressure or vacuum
    • 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
    • C21D9/40—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for rings; for bearing races
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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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    • C23C8/00—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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Abstract

The invention belongs to the technical field of heat treatment, and relates to a micro carburizing treatment method for 8Cr4Mo4V steel for an aeroengine bearing. A micro carburizing treatment method for 8Cr4Mo4V steel for an aeroengine bearing comprises the following steps of 1, carrying out spheroidizing annealing treatment on 8Cr4Mo4V steel, and carrying out micro carburizing treatment on the steel. 2. And performing micro carburizing and quenching treatment on the 8Cr4Mo4V steel after the spheroidizing annealing treatment. And 3, performing high-temperature tempering on the 8Cr4Mo4V steel subjected to the micro carburizing and quenching treatment for three times. The invention aims at the heat treatment of 8Cr4Mo4V steel bearing parts, adopts an atmosphere control furnace for heating and solution treatment, increases the carbon content of the surface layer by adjusting the carbon potential to achieve the effect of increasing the carbon concentration of the surface layer, and simultaneously generates residual compressive stress on the surface after tempering, thereby obviously improving the hardness, the wear resistance, the impact toughness and the rotary bending fatigue limit strength of the surface layer of 8Cr4Mo4V steel. The method has low requirement on equipment, is simple to operate, has low cost and has high practical value.

Description

Micro-carburizing process for improving mechanical property of 8Cr4Mo4V steel for aeroengine bearing
Technical Field
The invention belongs to the technical field of heat treatment processes, and relates to a micro-carburizing process for improving the mechanical property of 8Cr4Mo4V steel for an aeroengine bearing.
Background
The 8Cr4Mo4V steel is a 2 nd generation molybdenum series high alloy bearing steel with extremely high temperature bearing capacity, and is widely applied to DN value lower than 2.4 multiplied by 106Main shaft bearing of aircraft engine. The prior heat treatment of 8Cr4Mo4V mainly aims at obtaining martensite, and after quenching and tempering treatment, higher hardness can be obtained, but the impact toughness and the wear resistance are lower. Carburizing means a process of infiltrating carbon atoms into a surface layer of steel to make a low-carbon steel workpiece have a surface layer of high-carbon steel, and then quenching and low-temperature tempering are carried out to make the surface layer of the workpiece have high hardness and wear resistance, while the central part of the workpiece still maintains the toughness and plasticity of the low-carbon steel. General application of carburizing technologyThe carbon steel is used for low-carbon steel or low-alloy steel, has good carburizing effect, and has the defects of special requirements on equipment and high cost. The 8Cr4Mo4V steel is used as one of high-carbon steel, the carbon content in a matrix of the high-carbon steel is almost saturated, if the 8Cr4Mo4V steel is carburized, the regulation and control of the carbon potential are difficult, the carburization effect is poor due to the excessively high or excessively low carbon potential, and even the mechanical property is reduced.
The invention is different from the traditional carburization mode, the 8Cr4Mo4V steel is subjected to heat treatment, and simultaneously, the carbon potential of the atmosphere protective furnace is regulated and controlled to carry out micro carburization treatment, so that the surface can obtain high hardness and surface layer compressive stress, the fatigue property is improved, the core can keep good toughness, and the 8Cr4Mo4V steel can obtain excellent comprehensive mechanical property.
Disclosure of Invention
In view of the problems in the prior art, the invention aims to provide a micro-carburizing process for improving the mechanical property of 8Cr4Mo4V steel for an aeroengine bearing, wherein the micro-carburizing treatment is realized on the surface layer of the 8Cr4Mo4V steel after heat treatment, so that the comprehensive mechanical property indexes such as the hardness, the impact toughness, the rotating bending fatigue limit strength and the like of the surface layer of the steel are obviously improved.
In order to achieve the purpose, the invention adopts the following technical scheme.
A micro-carburizing process for improving the mechanical property of 8Cr4Mo4V steel for an aeroengine bearing comprises the following steps:
step 1, carrying out spheroidizing annealing treatment on 8Cr4Mo4V steel.
Step 2, micro carburizing and quenching treatment: and (3) placing the spheroidizing annealed 8Cr4Mo4V steel in an atmosphere protection furnace, carrying out solid solution heating and heat preservation, adjusting the carbon potential of the atmosphere protection furnace by adopting methanol and propane, measuring the carbon potential by adopting an oxygen probe, automatically adjusting, and then cooling the sample.
And 3, placing the quenched 8Cr4Mo4V steel into an atmosphere protection furnace or a vacuum furnace, heating to 550 ℃ from room temperature at a speed of 8-10 ℃/min, preserving heat for 2.5 hours, taking out the sample, air-cooling to room temperature, and performing high-temperature tempering for three times.
Further, in the step 1, the spheroidizing annealing operation is performed after the ring blank is forged and then is placed into ash cooling, and when the ash cooling temperature reaches 400-. The time from forging to spheroidizing annealing is required to be 16 hours or less. Before annealing, the forging stock is boxed, the box is placed in an effective temperature zone in an annealing furnace, the preheating temperature is 700-750 ℃, the preheating time is 3h, then the box is heated to 830-860 ℃, the heat preservation time is 6-7h, then the box is cooled to 720-750 ℃ along with the furnace, the heat preservation time is 11-12h, then the box is cooled to 680 ℃ at the speed of 20 ℃/h, and then the box is cooled to 500-550 ℃ along with the furnace and taken out of the furnace for air cooling.
Further, in the step 2, the temperature is raised from below 500 ℃ to 840-860 ℃ at a rate of 8-10 ℃/min, the temperature is maintained at 840-860 ℃ for 30-40 min, then the temperature is raised to 1000-1020 ℃ at a rate of 3-6 ℃/min, the temperature is maintained for 15-30 min, and then the temperature is raised to 1075-1110 ℃ at a rate of 6 ℃/min, and the temperature is maintained for 5-20 min.
Further, in the step 2, oil with the temperature of more than 150 ℃ is adopted for cooling, the cooling is carried out in an air cooling mode, the cooling is directly quenched into isothermal salt bath with the temperature of 180-220 ℃, and after the temperature is kept for 2 hours, the sample is cooled to room temperature by air. The temperature is required to be cooled to below 220 ℃ from high temperature, and the time is less than 5 min.
Further, the control range of the carbon potential in the step 2 is 0.35% -0.65%.
Further, after the quenching in the step 3 is cooled to room temperature, tempering treatment can be performed, and after the quenching is completed, the time interval for performing the first tempering is within 5 hours. There is no strict time requirement between the second and third tempering treatments and the first tempering treatment.
Compared with the prior art, the invention has the beneficial effects of.
The invention aims at the heat treatment of 8Cr4Mo4V steel bearing parts, adopts an atmosphere control furnace for heating and solution treatment, increases the carbon content of the surface layer by adjusting the carbon potential to achieve the effect of increasing the carbon concentration of the surface layer, and simultaneously generates residual compressive stress on the surface after tempering, thereby obviously improving the hardness, the wear resistance, the impact toughness and the rotary bending fatigue limit strength of the surface layer of 8Cr4Mo4V steel. The method has low requirement on equipment, is simple to operate, has low cost and has high practical value.
Drawings
FIG. 1 is a photograph of the structure in a quenched state after the end of step 2 in example 1; FIG. 1 (a) shows a superficial layer structure; FIG. 1 (b) shows the core structure.
FIG. 2 is a photograph of the structure in the tempered state after the end of step 3 in example 1; FIG. 2 (a) shows a superficial layer structure; FIG. 2 (b) shows the core structure.
FIG. 3 is a cross-sectional microhardness distribution at the end of step 3 of example 1.
FIG. 4 is a photograph of the structure in a quenched state after the end of step 2 in example 2; FIG. 4 (a) shows a superficial layer structure; FIG. 4 (b) shows the core structure.
FIG. 5 is a photograph of the structure in the tempered state after the end of step 3 in example 2; FIG. 5 (a) shows a superficial layer structure; FIG. 5 (b) shows the core structure.
FIG. 6 is a cross-sectional microhardness distribution at the end of step 3 of example 2.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
A micro-carburizing process for improving the mechanical property of 8Cr4Mo4V steel for an aeroengine bearing comprises the following steps:
step 1, carrying out spheroidizing annealing treatment on 8Cr4Mo4V steel.
Step 2, micro carburizing and quenching treatment: and (3) placing the spheroidizing annealed 8Cr4Mo4V steel in an atmosphere protection furnace, carrying out solid solution heating and heat preservation, adjusting the carbon potential of the atmosphere protection furnace by adopting methanol and propane, measuring the carbon potential by adopting an oxygen probe, automatically adjusting, and then cooling the sample.
And 3, placing the quenched 8Cr4Mo4V steel into an atmosphere protection furnace or a vacuum furnace, heating to 550 ℃ from room temperature at a speed of 8-10 ℃/min, preserving heat for 2.5 hours, taking out the sample, air-cooling to room temperature, and performing high-temperature tempering for three times.
Further, in the step 1, the spheroidizing annealing operation is performed after the ring blank is forged and then is placed into ash cooling, and when the ash cooling temperature reaches 400-. The time from forging to spheroidizing annealing is required to be 16 hours or less. Before annealing, the forging stock is boxed, the box is placed in an effective temperature zone in an annealing furnace, the preheating temperature is 700-750 ℃, the preheating time is 3h, then the box is heated to 830-860 ℃, the heat preservation time is 6-7h, then the box is cooled to 720-750 ℃ along with the furnace, the heat preservation time is 11-12h, then the box is cooled to 680 ℃ at the speed of 20 ℃/h, and then the box is cooled to 500-550 ℃ along with the furnace and taken out of the furnace for air cooling.
Further, in the step 2, the temperature is raised from below 500 ℃ to 840-860 ℃ at a rate of 8-10 ℃/min, the temperature is maintained at 840-860 ℃ for 30-40 min, then the temperature is raised to 1000-1020 ℃ at a rate of 3-6 ℃/min, the temperature is maintained for 15-30 min, and then the temperature is raised to 1075-1110 ℃ at a rate of 6 ℃/min, and the temperature is maintained for 5-20 min.
Further, in the step 2, oil with the temperature of more than 150 ℃ is adopted for cooling, the cooling is carried out in an air cooling mode, the cooling is directly quenched into isothermal salt bath with the temperature of 180-220 ℃, and after the temperature is kept for 2 hours, the sample is cooled to room temperature by air. The temperature is required to be cooled to below 220 ℃ from high temperature, and the time is less than 5 min.
Further, the control range of the carbon potential in the step 2 is 0.35% -0.65%.
Further, after the quenching in the step 3 is cooled to room temperature, tempering treatment can be performed, and after the quenching is completed, the time interval for performing the first tempering is within 5 hours. There is no strict time requirement between the second and third tempering treatments and the first tempering treatment.
Example 1.
And step 1, spheroidizing annealing operation is to perform spheroidizing annealing operation after the ring blank is placed into an ash cooling device after being forged and when the ash cooling temperature reaches 400 ℃. The time from forging to spheroidizing annealing is required to be 15 hours. Before annealing, boxing the forging stock, placing the box in an effective temperature zone in an annealing furnace, preheating at 700 ℃ for 3h, heating to 830 ℃ for 6h, cooling to 720 ℃ with the furnace, keeping the temperature for 11h, cooling to 680 ℃ with the speed of 20 ℃/h, cooling to 500 ℃ with the furnace, and taking out of the furnace for air cooling.
Step 2, micro carburizing and quenching treatment: placing 8Cr4Mo4V steel after spheroidizing annealing in an atmosphere protection furnace, wherein the temperature is raised from below 500 ℃ to 840 ℃ at the speed of 8 ℃/min, the temperature is kept at 840 ℃ for 30min, then the temperature is raised to 1000 ℃ at the speed of 3 ℃/min, the temperature is kept for 30min, then the temperature is raised to 1075 ℃ at the speed of 6 ℃/min, the temperature is kept for 5min, the atmosphere protection furnace adopts methanol and propane to adjust the carbon potential, an oxygen probe is adopted to measure the carbon potential and automatically adjust the carbon potential, the carbon potential is controlled to be 0.5%, then the furnace directly quenches in an isothermal salt bath at 200 ℃, and samples are air-cooled to room temperature after the temperature is kept for 2 h. The sample is required to be cooled from high temperature to below 220 ℃ for less than 5 min.
And 3, placing the quenched 8Cr4Mo4V steel in an atmosphere protection furnace or a vacuum furnace, heating to 550 ℃ from room temperature at a speed of 10 ℃/min, preserving heat for 2.5 hours, taking out the sample, air-cooling to room temperature, and then tempering, wherein the time interval for tempering for the first time is within 5 hours. There is no strict time requirement between the second and third tempering treatments and the first tempering treatment. Three high temperature tempers are required.
The 8Cr4Mo4V steel after final heat treatment is subjected to surface Rockwell hardness, impact performance and rotary bending fatigue performance tests.
Example 2.
Step 1, carrying out spheroidizing annealing treatment on 8Cr4Mo4V steel: and after the ring blank is forged, cooling the ring blank in ash, and performing spheroidizing annealing when the ash cooling temperature reaches 500 ℃. The time from forging to spheroidizing annealing is required to be 10 hours. Before annealing, boxing the forging stock, putting the box into an effective temperature zone in an annealing furnace, preheating at 750 ℃ for 3h, then heating to 860 ℃ and keeping the temperature for 7h, then cooling to 750 ℃ along with the furnace, keeping the temperature for 12h, then cooling to 680 ℃ along with the furnace at the speed of 20 ℃/h, then cooling to 550 ℃ along with the furnace, and taking out of the furnace for air cooling.
Step 2, micro carburizing and quenching treatment: placing 8Cr4Mo4V steel after spheroidizing annealing in an atmosphere protection furnace, wherein the temperature rise process is to raise the temperature from below 500 ℃ to 860 ℃ at the speed of 10 ℃/min, preserving the temperature for 40min at 860 ℃, then raising the temperature to 1010 ℃ at the speed of 5 ℃/min, preserving the temperature for 15min, then raising the temperature to 1095 ℃ at the speed of 6 ℃/min, preserving the temperature for 10min, adjusting the carbon potential of the atmosphere protection furnace by adopting methanol and propane, measuring the carbon potential by adopting an oxygen probe, automatically adjusting the carbon potential, controlling the carbon potential to be 0.65%, then directly quenching in an isothermal salt bath at 200 ℃, and air-cooling a sample to the room temperature after preserving the temperature for 2 h. The sample is required to be cooled from high temperature to below 220 ℃ for less than 5 min.
And 3, placing the quenched 8Cr4Mo4V steel in an atmosphere protection furnace or a vacuum furnace, heating to 550 ℃ from room temperature at a speed of 10 ℃/min, preserving heat for 2.5 hours, taking out the sample, air-cooling to room temperature, and tempering, wherein the time interval for tempering for the first time is within 5 hours. There is no strict time requirement between the second and third tempering treatments and the first tempering treatment.
The 8Cr4Mo4V steel after final heat treatment is subjected to surface Rockwell hardness, impact performance and rotary bending fatigue performance tests.
Comparative example 1.
Step 1, carrying out spheroidizing annealing treatment on 8Cr4Mo4V steel: and after the ring blank is forged, cooling the ring blank in ash, and performing spheroidizing annealing when the ash cooling temperature reaches 450 ℃. The time from forging to spheroidizing annealing is required to be 15 hours. Before annealing, boxing the forging stock, placing the box in an effective temperature zone in an annealing furnace, preheating at 720 ℃ for 3h, heating to 840 ℃ for 6h10min, furnace-cooling to 740 ℃ for 11h20min, furnace-cooling to 680 ℃ at a speed of 20 ℃/h, furnace-cooling to 530 ℃ and discharging for air cooling.
Step 2, micro carburizing and quenching treatment: placing 8Cr4Mo4V steel after spheroidizing annealing in an atmosphere protection furnace, wherein the temperature is raised from below 500 ℃ to 850 ℃ at the speed of 10 ℃/min, preserving heat for 35min at 850 ℃, then raising to 1020 ℃ at the speed of 6 ℃/min, preserving heat for 30min, then raising to 1110 ℃ at the speed of 6 ℃/min, preserving heat for 20min, the atmosphere protection furnace adopts methanol and propane to adjust the carbon potential, an oxygen probe is adopted to measure the carbon potential and automatically adjust the carbon potential, the carbon potential is controlled to be 0.8%, then the furnace is directly quenched in an isothermal salt bath at 200 ℃, and the sample is air-cooled to the room temperature after the temperature is preserved for 2 h. The sample is required to be cooled from high temperature to below 220 ℃ for less than 5 min.
And 3, placing the quenched 8Cr4Mo4V steel in an atmosphere protection furnace or a vacuum furnace, heating to 550 ℃ from room temperature at a speed of 10 ℃/min, preserving heat for 2.5 hours, taking out the sample, air-cooling to room temperature, tempering, wherein the time interval for tempering for the first time is within 5 hours, and no strict time requirement exists between the tempering for the second time and the third time and the tempering for the first time.
The 8Cr4Mo4V steel after final heat treatment is subjected to surface Rockwell hardness, impact performance and rotary bending fatigue performance tests.
Comparative example 2.
Step 1, carrying out spheroidizing annealing treatment on 8Cr4Mo4V steel: and after the ring blank is forged, cooling the ring blank in ash, and performing spheroidizing annealing operation when the ash cooling temperature reaches 470 ℃. The time from forging to spheroidizing annealing is required to be 15 hours. Before annealing, boxing the forging stock, placing the box in an effective temperature zone in an annealing furnace, preheating at 710 ℃ for 3h, then heating to 845 ℃, keeping the temperature for 6h and 30min, then furnace-cooling to 740 ℃, keeping the temperature for 11h and 15min, then cooling to 680 ℃ at the speed of 20 ℃/h, furnace-cooling to 540 ℃, and discharging from the furnace for air cooling.
And 2, placing the spheroidizing annealed 8Cr4Mo4V steel in an atmosphere protection furnace, wherein the temperature is raised to 840 ℃ from below 500 ℃ at the speed of 10 ℃/min, preserving the heat at 840 ℃ for 40min, then raising to 1010 ℃ at the speed of 6 ℃/min, preserving the heat for 25min, then raising to 1100 ℃ at the speed of 6 ℃/min, preserving the heat for 10min, then directly quenching into an isothermal salt bath at 200 ℃, preserving the heat for 2h, and then cooling the sample to room temperature in air. The sample is required to be cooled from high temperature to below 220 ℃ for less than 5 min.
And 3, placing the quenched 8Cr4Mo4V steel in an atmosphere protection furnace or a vacuum furnace, heating to 550 ℃ from room temperature at a speed of 10 ℃/min, preserving heat for 2.5 hours, taking out the sample, air-cooling to room temperature, and tempering, wherein the time interval for tempering for the first time is within 5 hours. There is no strict time requirement between the second and third tempering treatments and the first tempering treatment.
The 8Cr4Mo4V steel after final heat treatment is subjected to surface Rockwell hardness, impact performance and rotary bending fatigue performance tests.
The above examples were compared with the 8Cr4Mo4V steel of comparative example, and the following results were obtained.
Table 1 comparative test results of examples and comparative examples.
Figure 784603DEST_PATH_IMAGE001
By comparing the examples and the comparative examples, the invention can obviously improve the hardness, the impact toughness and the rotary bending fatigue limit of the material by comprehensively considering.
It can be seen from FIG. 1 (a) that the surface layer of example 1 has more retained austenite and less bainite and martensite; the core part of FIG. 1 (b) is mainly a martensite + bainite composite structure.
As can be seen from fig. 2 (a), in example 1, fine and uniformly distributed carbides are dispersed and precipitated on the tempered ferrite, and a small amount of martensite structure is contained; FIG. 2 (b) shows the core structure, mainly ferrite and fine and uniformly distributed carbides.
It can be seen from fig. 4 (a) that the surface layer of example 2 has more retained austenite and less bainite and martensite; in FIG. 4 (b), the core is mainly a martensite + bainite composite structure.
As can be seen from fig. 5 (a), in example 2, fine and uniformly distributed carbides are dispersed and precipitated on the tempered ferrite, and a small amount of martensite structure is contained; FIG. 5 (b) shows the core structure, mainly ferrite and fine and uniformly distributed carbides.
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.

Claims (7)

1. A micro carburization process for improving the mechanical property of 8Cr4Mo4V steel for an aeroengine bearing is characterized by comprising the following steps:
step 1, carrying out spheroidizing annealing treatment on 8Cr4Mo4V steel;
step 2, micro carburizing and quenching treatment: placing the spheroidizing annealed 8Cr4Mo4V steel in an atmosphere protection furnace, carrying out solid solution heating and heat preservation, adjusting the carbon potential of the atmosphere protection furnace by adopting methanol and propane, measuring the carbon potential by adopting an oxygen probe, automatically adjusting, and then cooling a sample;
and 3, placing the quenched 8Cr4Mo4V steel into an atmosphere protection furnace or a vacuum furnace, heating to 550 ℃ from room temperature at a speed of 8-10 ℃/min, preserving heat for 2.5 hours, taking out the sample, air-cooling to room temperature, and performing high-temperature tempering for three times.
2. The micro-carburizing process for improving the mechanical property of 8Cr4Mo4V steel for an aircraft engine bearing as claimed in claim 1, wherein in the step 1, the spheroidizing annealing operation is performed after the ring blank is forged and then placed in ash cooling, and when the ash cooling temperature reaches 400-500 ℃; the time from forging to spheroidizing annealing is required to be less than or equal to 16 h; before annealing, the forging stock is boxed, the box is placed in an effective temperature zone in an annealing furnace, the preheating temperature is 700-750 ℃, the preheating time is 3h, then the box is heated to 830-860 ℃, the heat preservation time is 6-7h, then the box is cooled to 720-750 ℃ along with the furnace, the heat preservation time is 11-12h, then the box is cooled to 680 ℃ at the speed of 20 ℃/h, and then the box is cooled to 500-550 ℃ along with the furnace and taken out of the furnace for air cooling.
3. The micro-carburizing process for improving the mechanical property of the 8Cr4Mo4V steel for the aircraft engine bearing, according to claim 1, characterized in that in the step 2, the temperature is raised from 500 ℃ below at a rate of 8-10 ℃/min to 840-860 ℃, the temperature is maintained at 840-860 ℃ for 30-40 min, then raised to 1000-1020 ℃ at a rate of 3-6 ℃/min, the temperature is maintained for 15-30 min, and then raised to 1075-1110 ℃ at a rate of 6 ℃/min, and the temperature is maintained for 5-20 min.
4. The micro-carburizing process for improving the mechanical property of 8Cr4Mo4V steel for an aeroengine bearing according to claim 1, wherein the cooling in the step 2 is any one of methods of cooling by using oil with the temperature of more than 150 ℃, cooling by air cooling, directly quenching into isothermal salt bath with the temperature of 180-220 ℃, keeping the temperature for 2 hours, and then cooling the sample to room temperature by air cooling.
5. The micro-carburizing process for improving the mechanical property of 8Cr4Mo4V steel for aeroengine bearings according to claim 4, wherein the cooling is required to be carried out from high temperature to below 220 ℃ for less than 5 min.
6. The micro-carburizing process for improving the mechanical property of 8Cr4Mo4V steel for an aircraft engine bearing according to claim 1, wherein the carbon potential in the step 2 is controlled within the range of 0.35-0.65%.
7. The micro-carburizing process for improving the mechanical property of 8Cr4Mo4V steel for an aeroengine bearing according to claim 1, wherein the tempering treatment can be performed after the quenching in step 3 is cooled to room temperature, and the time interval for performing the first tempering is within 5h after the quenching is completed; there is no strict time requirement between the second and third tempering treatments and the first tempering treatment.
CN202111089881.5A 2021-09-17 2021-09-17 Micro-carburizing process for improving mechanical property of 8Cr4Mo4V steel for aeroengine bearing Active CN113802085B (en)

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CN111411203A (en) * 2020-04-15 2020-07-14 沈阳工业大学 Method for obtaining 8Cr4Mo4V steel and optimizing quenching process

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