CN110735105B - Method for prolonging contact fatigue life of high-carbon bearing steel - Google Patents
Method for prolonging contact fatigue life of high-carbon bearing steel Download PDFInfo
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- CN110735105B CN110735105B CN201911033033.5A CN201911033033A CN110735105B CN 110735105 B CN110735105 B CN 110735105B CN 201911033033 A CN201911033033 A CN 201911033033A CN 110735105 B CN110735105 B CN 110735105B
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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
- 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
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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
- C21D2211/001—Austenite
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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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Abstract
A method for prolonging the contact fatigue life of high-carbon bearing steel belongs to the technical field of control of long service life of high-carbon bearing steel. The technical parameters of the process steps and control are as follows: carburizing the high-carbon bearing steel to obtain a carburized layer with the surface layer larger than 0.2mm, wherein the carburization temperature is 880-980 ℃, the carburization time is 3-10 h, the carburization is carried out by gas, the carburization carbon potential is 1.5-3.0%, the vacuum carburizing furnace pressure is 700-900 Pa, the vacuum carburizing gas flow is 1500-2000L/h, and the carburized steel is subjected to gas cooling at 2-4 bar; quenching the high-carbon bearing steel within 4 hours after carburizing treatment, heating the high-carbon bearing steel to 880-950 ℃, preserving the heat for 1-4 hours, performing water quenching, gas quenching or oil cooling, and cooling the high-carbon bearing steel to room temperature; and (3) carburizing, quenching, tempering at 120-220 ℃, keeping the temperature for 1-4 h, and air cooling. Has the advantages that: the contact fatigue life and the wear resistance of the high-carbon bearing steel are greatly prolonged, the contact fatigue life of the bearing steel or the bearing is maximally prolonged by more than 10 times, and the long service life and the high reliability of the bearing made of the high-carbon bearing steel are endowed.
Description
Technical Field
The invention belongs to the technical field of control of long service life of high-carbon bearing steel, and particularly relates to a method for prolonging the contact fatigue life of the high-carbon bearing steel, which greatly prolongs the contact fatigue life and the wear resistance of the high-carbon bearing steel, and improves the contact fatigue life of the bearing steel or the bearing by more than 10 times to the maximum.
Technical Field
The bearing is an indispensable basic part of various equipment, and the service life and the reliability of the main machine are determined. The bearing performance is closely related to the metallurgical quality of the bearing material. Generally, the metallurgical quality of bearing steel includes important metallurgical indexes such as oxygen content, titanium content and large-particle inclusions, and the performance of bearing steel mainly includes wear resistance, contact fatigue property and cold and hot workability. The oxygen content of the prior common vacuum degassing bearing steel is less than or equal to 10ppm, the titanium content is less than or equal to 20ppm and the DS of large-particle impurities is less than or equal to 1Grade, so that the test contact fatigue life L10 measured by a thrust sheet is more than or equal to 0.5x10 under the contact fatigue stress level of 4.5GPa7Secondly; the oxygen content of the high-end bearing steel is less than or equal to 6ppm, the titanium content is less than or equal to 15ppm and the DS of large-particle inclusions is less than or equal to 0.5 grade, so that the contact fatigue life L10 of the test, which is measured by a thrust piece, of the common bearing steel is more than or equal to 1x10 under the contact fatigue stress level of 4.5GPa7And meanwhile, the wear-resistant steel has excellent wear resistance and cold and hot processability.
However, with the increasing demands of the service life and reliability of high-end equipment main machines such as high-speed railways, aviation airplanes and high-speed precision machine tools, the contact fatigue life L10 of the surface of the bearing material is required to be more than or equal to 1x108Next, the process is carried out. The requirements of high-end equipment on the service life and reliability of bearing steel cannot be met only by improving the metallurgical quality and performance of materials. In order to meet the development requirements of long service life and high reliability, on the one hand, the cleanliness of steel is improved, the contents of oxygen and titanium in the steel are reduced, large-particle inclusions in the steel are controlled, and the service life and the reliability of the bearing are improved at home and abroad in the aspect of material metallurgical quality. For example, the mass fraction of oxygen in the highest-grade bearing steel of Japan Shanyang is generally controlled to be less than 5ppm, some oxygen even reaches 2-3 ppm, and the maximum inclusion size is 11 μm; for example, Ovako in Sweden is bearing steel smelted by die casting, the mass fraction of oxygen in the common-grade (B-grade) bearing steel is controlled to be 4-6 ppm, and the mass fraction of titanium is controlled to be 8-12 ppm. The service life of the bearing can be greatly prolonged through the regulation and control of the matrix structure and the carbide. The latest research results show that the heat treatment process technology of structure refinement and homogenization is adopted to realize the great refinement of the bearing steel matrix structure and carbide, thereby obviously improving the service life and reliability of the bearing. For example, on the basis of a high-cleanliness smelting technology, not only can grains be refined, but also carbides can be refined through special heat treatment, and the carbide distribution is improved. The special heat treatment technology for refining the structure can not only improve the strength and the hardness of the bearing steel, but also improve the contact fatigue life of the bearing by more than 5 times. In addition, the heat treatment technology of the excessive austenite content on the surface and the ultrahigh hardness on the surface is successfully developed abroad, and the contact fatigue life of high-carbon bearing steel such as bearing steel GCr15 and the like is prolongedThe highest life is improved by 10 times.
Disclosure of Invention
The invention aims to provide a method for prolonging the contact fatigue life of high-carbon bearing steel. By carrying out surface deep carburizing on the bearing steel, 15-35% of carbide is introduced into the surface of the bearing steel, 15-30% of residual austenite is introduced, and the surface hardness of the bearing steel is improved by 10%. The contact fatigue life of the bearing steel is improved by more than 10 times by the process. The specific process steps and the controlled technical parameters are as follows:
(1) carburizing the high-carbon bearing steel to obtain a carburized layer with the surface layer larger than 0.2mm, wherein the carburization temperature is 880-980 ℃, the carburization time is 3-10 h, the carburization carbon potential is 1.5-3.0%, the furnace pressure of vacuum carburization (the vacuum degree is 3-5 Pa) is 700-900 Pa, the gas flow rate of the vacuum carburization is 1500-2000L/h, and the carburized layer is cooled by air at 2-4 bar; performing vacuum oil quenching on the mixture,
(2) quenching the high-carbon bearing steel within 4 hours after carburizing treatment, heating to 880-950 ℃, preserving heat for 1-4 hours, then performing water quenching, gas quenching or oil cooling (vacuum degree is 3-5 Pa), and cooling to room temperature;
(3) and (3) carrying out tempering treatment after carburizing and quenching treatment of the high-carbon bearing steel, heating at 120-220 ℃, preserving heat for 1-4 h, and then carrying out air cooling.
And (2) improving the carbon content of the surface layer of the high-carbon bearing steel by carburizing treatment in the step (1) to obtain the carbon concentration of the surface layer of more than 1.2 percent.
Through the carburizing treatment in the step (1) and the quenching treatment in the step (2), 10-30% of residual austenite is obtained on the surface layer of the bearing steel.
Through the carburizing treatment in the step (1), the quenching treatment in the step (2) and the tempering treatment in the step (3), 15-35% of carbide tissues are obtained on the surface layer of the bearing steel, and the carbide forms are in a grid shape and a strip shape.
The principle of the process selection of the invention is as follows:
the carbon content of the surface layer of the high-carbon bearing steel is improved through high-temperature carburization, and preparation for introducing a large amount of carbide and a large amount of austenite for the surface layer is made. Adjusting the carbon content in the high-carbon bearing steel to be in a range of 1.2-2.8% according to the carburizing temperature, the carburizing carbon potential and the carburizing time;
the heat preservation process is to rapidly transfer the carburized high-carbon bearing steel from the high temperature of carburization to a lower heat preservation temperature, ensure that carbon in high-carbon austenite obtained in the carburization process is converted into sheet carbide as much as possible, promote the formation of a latticed carbide structure and further improve the wear resistance and the contact fatigue performance;
the high-carbon bearing steel after heat preservation is quenched to a lower temperature to obtain a martensite structure with high hardness and a large amount of retained austenite of 15-30%, and the high hardness and the surface hardness of nearly 10% of the surface of the bearing steel are improved. A large amount of retained austenite and 10% of surface hardness are improved, and the key for ensuring the high contact fatigue life is also realized;
tempering is carried out at 120-220 ℃, and the main purpose of the tempering is to improve the stability of retained austenite and the dimensional stability of the high-carbon bearing steel. Through low-temperature tempering, the carbon content in the martensite enters austenite through distribution, so that the austenite is retained at the temperature, the quenching stress is reduced, and the dimensional stability of the carburized high-carbon bearing steel is improved.
The invention has the advantages that a high-hardness surface multi-phase structure containing a large amount of carbide and residual austenite is formed through surface carburization, the contact fatigue life and the wear resistance of the bearing steel are greatly improved, and the contact fatigue life L10 of the bearing steel measured by a thrust piece is more than or equal to 1x10 under the contact fatigue stress level of 4.5GPa8Next, the process is carried out. The contact fatigue life of the bearing steel or the bearing is improved by more than 10 times to the maximum extent, the long service life and the high reliability of the bearing made of the high-carbon bearing steel are endowed, the method becomes one of effective process methods for realizing the long service life and the high reliability of the bearing for high-end equipment, and the method has wide bearing manufacturing, popularization and application markets.
Drawings
FIG. 1 is a diagram of a high carbon bearing steel thrust plate sample used in the practice of the process technology of the present invention.
FIG. 2 is a data diagram of a fatigue life test of a high carbon bearing steel thrust piece sample after being treated by the method and the traditional process.
FIG. 3 is a structural diagram of a plurality of strip-shaped carbides formed on the surface of high carbon bearing steel after the treatment of the present invention and a latticed carbide formed therefrom.
FIG. 4 is M formed on the surface of high carbon bearing steel after treatment according to the present invention3Type C carbide diagram.
FIG. 5 is a graph showing the results of the surface hardness distribution of the sample after carburization.
FIG. 6 is a diagram of the results of the X-ray testing of the austenite on the surface of the high carbon bearing steel treated by the present invention.
Detailed Description
The present invention will be described in further detail with reference to examples.
Example (b):
selecting super-clean bearing steel GCr15 bar materials produced by domestic steel works, wherein the oxygen content is 5ppm, the titanium content is 9ppm and the DS of large-particle inclusions is less than or equal to 0.5 grade. The specific chemical composition is shown in Table 1.
TABLE 1 GCr15 chemical composition (balance Fe)
The GCr15 steel thrust plate sample is processed as shown in figure 1, and the heat treatment process comprises the following steps:
(1) vacuum carburization, the vacuum degree is 4Pa, the pressure in the furnace is 800Pa, the carburization temperature is 950 ℃, carburization-diffusion circulation is carried out for 20 times, the carburization time is 4 hours, and 2bar air cooling is carried out after the carburization is finished.
(2) Vacuum oil quenching, wherein the vacuum degree is 4Pa, the heating temperature is 840 ℃, the temperature is kept for 1h, and oil cooling is carried out.
(3) Tempering: keeping the temperature at 170 ℃ for 3h, and cooling in air.
The processed GCr15 steel thrust piece sample is subjected to a fatigue test, the maximum Hertz stress of the test is 4.5GPa, the rotating speed is 1500 rpm, oil lubrication is adopted, data are processed according to Weibull distribution, and the fatigue test result is shown in figure 2. Compared with the traditional treatment process, the fatigue life is improved by more than 10 times.
The processed GCr15 steel thrust piece sample is characterized by a surface microstructure, and the results are shown in fig. 3, 4 and 5 by means of EBSD orientation scanning under an optical microscope and a scanning electron microscope, X-ray diffraction and the like. By passingFor carburized layer. FIG. 3 shows a number of strip-shaped carbides and the resulting lattice-like carbide structure observed using an optical microscope. The carbide content was analyzed to reach 30%. From the carbide hardness (1040HV) and the matrix hardness (680HV), it was found that the surface hardness reached 788 HV. This is substantially in accordance with the experimentally measured surface hardness 765 HV. It is shown that by carburizing and surface carbide control, a 10% increase in surface hardness can be achieved, as shown in fig. 5. FIG. 4 shows the orientation results of the carbide and matrix structure characterized by EBSD, indicating that the 30% carbide formed during carburization is M3Type C carbide. FIG. 6 shows the surface austenite content measured by X-ray, which yields about 20% of surface retained austenite.
Claims (3)
1. A method for improving the contact fatigue life of high-carbon bearing steel is characterized in that the technical steps and the controlled technical parameters are as follows:
(1) carburizing the high-carbon bearing steel to obtain a carburized layer with the surface layer larger than 0.2mm, wherein the carburization temperature is 880-980 ℃, the carburization time is 3-10 h, the carburization is carried out by gas, the carburization carbon potential is 1.5-3.0%, the vacuum carburizing furnace pressure is 700-900 Pa, the vacuum carburizing gas flow is 1500-2000L/h, and the carburized steel is subjected to gas cooling at 2-4 bar;
(2) quenching the high-carbon bearing steel within 4 hours after carburizing treatment, heating to 880-950 ℃, preserving heat for 1-4 hours, then performing water quenching, gas quenching or oil cooling, and cooling to room temperature;
(3) carrying out tempering treatment after carburizing and quenching treatment on the high-carbon bearing steel, heating at 120-220 ℃, preserving heat for 1-4 h, and then carrying out air cooling;
through the carburizing treatment in the step (1), the quenching treatment in the step (2) and the tempering treatment in the step (3), 15-35% of carbide tissues are obtained on the surface layer of the bearing steel, and the carbide forms are in a grid shape and a strip shape.
2. The method for improving the contact fatigue life of the high-carbon bearing steel according to claim 1, wherein the carbon content of the surface layer of the high-carbon bearing steel is increased by the carburizing treatment in the step (1), and the carbon concentration of the surface layer is more than 1.2%.
3. The method for improving the contact fatigue life of the high carbon bearing steel according to claim 1, wherein 10 to 30% of the retained austenite is obtained on the surface layer of the bearing steel by the carburizing treatment in the step (1) and the quenching treatment in the step (2).
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH02159360A (en) * | 1988-12-09 | 1990-06-19 | Mazda Motor Corp | Production of carburization hardened member |
| CN101058865A (en) * | 2007-05-30 | 2007-10-24 | 太原理工大学 | Supersaturated carburizing steel |
| CN102505067A (en) * | 2011-12-29 | 2012-06-20 | 瓦房店轴承集团有限责任公司 | Bainite quenching method at variable temperatures of high-carbon-chromium bearing steel |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH02159360A (en) * | 1988-12-09 | 1990-06-19 | Mazda Motor Corp | Production of carburization hardened member |
| CN101058865A (en) * | 2007-05-30 | 2007-10-24 | 太原理工大学 | Supersaturated carburizing steel |
| CN102505067A (en) * | 2011-12-29 | 2012-06-20 | 瓦房店轴承集团有限责任公司 | Bainite quenching method at variable temperatures of high-carbon-chromium bearing steel |
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