CN113337693A - Heat treatment method for reducing steel-mesh carbide level of large-size bearing - Google Patents
Heat treatment method for reducing steel-mesh carbide level of large-size bearing Download PDFInfo
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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
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
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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
- 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
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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
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/005—Heat treatment of ferrous alloys containing Mn
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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
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/008—Heat treatment of ferrous alloys containing Si
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
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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
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
Abstract
The invention relates to a heat treatment method for reducing the level of large-specification bearing steel network carbide, and belongs to the technical field of bearing steel heat treatment. In order to solve the problem that the mesh carbide grade of large-section bearing steel is too high due to no on-line cooling control means, the invention provides a heat treatment method for reducing the mesh carbide grade of large-size bearing steel, which comprises the steps of bearing steel quenching treatment → water cooling treatment → isothermal spheroidizing annealing treatment → furnace cooling treatment, wherein the specific quenching temperature is 930 +/-10 ℃, water cooling is carried out for 2-3 min after quenching heat preservation is finished, and the steel temperature is controlled to be 600-650 ℃ after water cooling; the isothermal spheroidizing annealing treatment is to firstly raise the temperature to 800 +/-10 ℃ and preserve heat for 13 hours, and then to reduce the temperature to 700 +/-10 ℃ and preserve heat for 5 hours. The method can effectively control the distribution form of the reticular carbide at the steel core part of the large-specification bearing, the grade of the obtained reticular carbide of the large-specification bearing is less than or equal to 2.5, and the product requirement of the cold-processed bearing steel for the large-specification rolling body is met.
Description
Technical Field
The invention belongs to the technical field of bearing steel heat treatment, and particularly relates to a heat treatment method for reducing the level of large-specification bearing steel network carbide.
Background
The cold-processed bearing steel for large-size rolling bodies of large-scale high-end equipment bearings such as high-power wind power and shield machines and the like adopts the production process of secondary forging forming and spheroidizing annealing of a roll forging material, and has the outstanding problems of long production period, low efficiency, serious internal reticular carbide and the like. The structural uniformity of the high-carbon chromium bearing steel, particularly the state of carbide, has important influence on the performance and the service life of a bearing rolling element. The domestic high-end equipment main bearing adopts 100 percent of imported products, and the domestic process of the main bearing is mainly limited by the quality of domestic high-quality bearing steel materials.
The large-section bar and the small-section bar have great difference in the rolling production process. The small-section bearing steel with the rolled material diameter smaller than 40mm can inhibit the net-shaped carbide by online control cooling, so that the grade of the net-shaped carbide is not more than 2.0; and the large-section bearing steel with the rolled material diameter larger than 40mm does not have an online cooling control means, and the net-shaped carbide in the rolled material can reach 3.0 level or even higher. The size of the main bearing rolling body of the large shield machine is more than 90mm, the rolled material is directly subjected to heat treatment without secondary processing, the mesh carbide after the heat treatment is required to be less than 2.5 grade, and the lower the grade is, the better the quality is. The conventional heat treatment only slightly improves the state of the network carbide and cannot fundamentally eliminate the influence of the network carbide.
Disclosure of Invention
The invention provides a heat treatment method for reducing the level of the network carbide of large-size bearing steel, aiming at solving the problem that the network carbide level of large-section bearing steel is too high due to no on-line cooling control means.
The technical scheme of the invention is as follows:
a heat treatment method for reducing the level of steel-mesh carbides of a large-size bearing comprises bearing steel quenching treatment → water cooling treatment → isothermal spheroidizing annealing treatment → furnace cooling treatment, wherein the quenching temperature is 930 +/-10 ℃, water cooling is carried out for 2-3 min after quenching and heat preservation, and the steel temperature is controlled to be 600-650 ℃ after water cooling; the isothermal spheroidizing annealing treatment is to firstly raise the temperature to 800 +/-10 ℃ and preserve heat for 13 hours, and then lower the temperature to 700 +/-10 ℃ and preserve heat for 5 hours.
Further, the diameter of the section of the large-specification bearing steel is not less than 40 mm.
Further, the heat preservation time of the quenching treatment is 8 hours.
Further, the cooling speed of the isothermal spheroidizing annealing process from 800 +/-10 ℃ to 700 +/-10 ℃ is 10-15 ℃/h.
Further, the furnace cooling treatment is carried out after cooling to 600 ℃ at a cooling speed of 20 ℃/h.
Further, the bearing steel comprises the following chemical components in percentage by weight: c: 0.96-0.97%, Si: 0.21-0.24%, Mn: 0.28-0.29%, P: 0.007-0.014%, S: 0.001-0.006%, Als: 0.009-0.013%, Alt: 0.011-0.015%, Cr: 1.43%, Ni: 0.02%, Mo: 0.001-0.006%, V: 0.002-0.003%, Ti: 0.0010%, and the balance of Fe and inevitable impurities.
The invention has the beneficial effects that:
the heat treatment method for the large-size bearing steel provided by the invention can effectively control the distribution form of the network carbide of the large-size bearing steel, is applicable to rolling or forging bearing steel products, and solves the problem that the network carbide level of the large-size bearing steel is too high due to no on-line cooling control means.
The invention solves the problem that the conventional heat treatment can only slightly improve the state of the net-shaped carbide and cannot radically eliminate the influence of the net-shaped carbide. Isothermal spheroidizing annealing is adopted, the period of the isothermal annealing process is short, the tissues along the cross section are uniform and consistent, compared with repeated spheroidizing annealing, the operation is simple, the control is convenient,
the grade of 1/2R and the grade of the net-shaped carbide at the heart part of the large-size bearing steel section edge obtained by the heat treatment method provided by the invention are both less than or equal to 2.5 grades, the hardness can be stably controlled within 180-190 HBW, the microstructure is 2.0, and the structure is uniform and stable. The maximum specification of the bearing steel applicable to the heat treatment method provided by the invention can reach 150mm, and the product requirements of the cold-processed bearing steel for large-size rolling bodies of large-scale high-end equipment bearings such as high-power wind power and shield machines can be met.
Drawings
FIG. 1 is a distribution diagram of net-like carbides of a starting material of a bearing steel of phi 90mm in a hot rolled state according to example 1;
FIG. 2 is a distribution diagram of net-like carbides of a bearing steel material of phi 110mm in a hot rolled state of example 2;
FIG. 3 is a distribution diagram of net-like carbides of a bearing steel material of phi 150mm in a hot rolled state of example 3;
FIG. 4 is a graph showing the distribution of net-like carbides at the edge position of a bearing steel of 90mm diameter after heat treatment in example 1;
FIG. 5 is a graph showing the distribution of reticulated carbides at 1/2R sites in the phi 90mm bearing steel after heat treatment in example 1;
FIG. 6 is a distribution diagram of net-shaped carbides at the steel core position of a bearing with a diameter of 90mm after heat treatment in example 1;
FIG. 7 is a graph showing the distribution of net-like carbides at the edge position of a bearing steel of 110mm diameter after heat treatment in example 2;
FIG. 8 is a net-like carbide distribution plot of 1/2R locations in phi 110mm bearing steel after heat treatment in example 2;
FIG. 9 is a net-like carbide distribution diagram of the steel core position of a bearing with a diameter of 110mm after heat treatment in example 2;
FIG. 10 is a graph showing the distribution of net-like carbides at the edge position of a bearing steel of phi 150mm after heat treatment in example 3;
FIG. 11 is a graph of the net-like carbide distribution at 1/2R location for a bearing steel of 150mm phi after heat treatment in example 3;
FIG. 12 is a distribution diagram of the net-shaped carbide at the steel core part position of the bearing with the diameter of 150mm after the heat treatment of example 3;
FIG. 13 is a distribution diagram of reticulated carbides at 5mm of the edge of a bearing steel of phi 150mm after heat treatment in example 3;
FIG. 14 is a graph showing the distribution of reticulated carbides at 10mm of the edge of a 150mm diameter bearing steel after heat treatment in example 3;
FIG. 15 is a graph showing the distribution of reticulated carbides at 15mm of the edge of a 150mm diameter bearing steel after heat treatment in example 3;
FIG. 16 is a distribution diagram of reticulated carbides 20mm from the edge of a bearing steel of phi 150mm after heat treatment in example 3;
FIG. 17 is a graph showing the distribution of reticulated carbides at 25mm of the edge of a 150mm diameter bearing steel after heat treatment in example 3;
FIG. 18 is a graph showing the distribution of reticulated carbides at 30mm of the edge of a 150mm phi bearing steel after heat treatment in example 3;
FIG. 19 is a graph showing the distribution of reticulated carbides at 40mm of the edge of a 150mm phi bearing steel after heat treatment in example 3;
FIG. 20 is a graph showing the distribution of reticulated carbides at 45mm of the edge of a 150mm phi bearing steel after heat treatment in example 3;
FIG. 21 is a graph showing the distribution of reticulated carbides at 50mm of the edge of a 150mm diameter bearing steel after heat treatment in example 3;
FIG. 22 is a distribution diagram of the net-shaped carbides at 55mm of the edge of the bearing steel with the diameter of 150mm after the heat treatment of the embodiment 3;
FIG. 23 is a distribution diagram of reticulated carbides at 65mm of the edge of a 150mm phi bearing steel after heat treatment in example 3;
FIG. 24 is a distribution diagram of reticulated carbides at 70mm of the edge of a 150mm phi bearing steel after heat treatment in example 3;
FIG. 25 is a graph showing the distribution of reticulated carbides at 75mm of the edge of a 150mm diameter bearing steel after heat treatment in example 3;
FIG. 26 is a photograph of a microstructure of an edge position of a section of a bearing steel of Φ 150mm after heat treatment of example 3;
FIG. 27 is a photograph of the microstructure of example 3 at the 1/2R position of a section of a bearing steel of phi 150mm after heat treatment;
FIG. 28 is a photograph showing the microstructure of the center of a cross section of a bearing steel of Φ 150mm after heat treatment in example 3.
Detailed Description
The technical solutions of the present invention are further described below with reference to the following examples, but the present invention is not limited thereto, and any modifications or equivalent substitutions may be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention. The process equipment or apparatus not specifically mentioned in the following examples are conventional in the art, and if not specifically mentioned, the raw materials and the like used in the examples of the present invention are commercially available; unless otherwise specified, the technical means used in the examples of the present invention are conventional means well known to those skilled in the art.
Example 1
The embodiment provides a heat treatment method of large-size bearing steel with the section diameter of 90 mm.
The raw materials are hot rolled bearing steel with the section diameter of 90mm, and the bearing steel comprises the following chemical components in percentage by weight: c: 0.97%, Si: 0.24%, Mn: 0.28%, P: 0.009%, S: 0.002%, Als: 0.011%, Alt: 0.013%, Cr: 1.43%, Ni: 0.02%, Mo: 0.001%, V: 0.002%, Ti: 0.0010%, and the balance of Fe and inevitable impurities.
Because the high-carbon chromium bearing steel bar with a large section is difficult to effectively control and cool in the production process, the serious network carbide exists at the section.
When the high-carbon chromium bearing steel is slowly cooled, because the atomic arrangement at the crystal boundary is irregular, the defects are more, and the high-carbon chromium bearing steel is a rapid channel for element diffusion. Therefore, the carbide-forming elements such as C, Cr, Mn, etc. have a relatively sufficient time to diffuse to the grain boundaries and aggregate and grow at the grain boundaries, and the Cr, Mn elements form (Fe. Mn) by replacing a part of Fe atoms3C、(Fe·Mn)3C、Cr7C3、M23C6Carbonization of the like typeThese carbides are like bones and form network carbides along the prior austenite grain boundaries. With the increase of the cooling speed, on one hand, the diffusion rate of C, Cr and Mn elements is reduced, on the other hand, austenite rapidly passes through a carbide precipitation phase region and only stays for a short time, and the diffusion time of the austenite in a high-temperature region is shortened. Therefore, the contents of C, Cr and Mn elements at grain boundaries are reduced, thereby limiting the precipitation conditions of secondary carbides and effectively suppressing the number and thickness of network carbides.
"quenching" is the heat treatment process that ultimately determines the properties of the bearing steel. The high and low quenching heating temperature will affect the amount of carbon in the austenite in solution, and ultimately the retained austenite content and the martensite morphology.
Spheroidizing annealing is annealing performed to spheroidize carbides in steel to obtain a structure of spherical or granular carbides uniformly distributed on a ferrite matrix to obtain a spheroidized structure similar to granular pearlite, thereby reducing hardness and improving machinability.
The heat treatment method of the embodiment comprises the steps of quenching treatment of a hot rolled bearing steel material → water cooling treatment → isothermal spheroidizing annealing treatment → furnace cooling treatment.
The quenching temperature of the hot rolled bearing steel is 930 ℃, and the heat preservation time is 8 hours, so that the carbide is further dissolved and diffused. And after quenching and heat preservation are finished, water cooling is carried out for 2-3 min, so that the steel plate quickly passes through the temperature range of 700-850 ℃, carbide precipitation is strongly inhibited, and the proportion of cementite in pearlite is increased. Meanwhile, the temperature of the bar after water cooling is controlled between 600 ℃ and 650 ℃, so that bainite or martensite structures are prevented from being generated, and the formation of network carbides and ribbon carbides of bearing steel is reduced.
The bearing steel has extremely high hardness after quenching, and is difficult to cut. After quenching, the hardness of the bearing steel is controlled through isothermal spheroidizing annealing treatment. The temperature is increased to 800 ℃ and is kept for 13h, so that the problem that the temperature difference of the central part and the surface of large-size bearing steel exists in the heat treatment process is solved, flaky pearlite disappears, a part of carbide which is not completely dissolved in austenite is reserved as a spheroidization core, and a normal spheroidization structure of coarse granular carbide is finally formed.
Cooling the steel plate to 700 ℃ along with the furnace at a cooling speed of 10-15 ℃/h, and preserving heat for 5h to finish the structure transformation, so as to obtain the structure of spherical or granular carbide uniformly distributed on the ferrite matrix. Cooling the mixture to 600 ℃ along with the furnace at a cooling speed of 20 ℃/h, and then performing air cooling.
Example 2
The embodiment provides a heat treatment method of large-specification bearing steel with the section diameter of 110 mm.
The raw materials are bearing steel hot rolling materials with the section diameter of 110mm, and the bearing steel comprises the following chemical components in percentage by weight: c: 0.96%, Si: 0.23%, Mn: 0.29%, P: 0.007%, S: 0.006%, Als: 0.013%, Alt: 0.015%, Cr: 1.43%, Ni: 0.02%, Mo: 0.006%, V: 0.002%, Ti: 0.0010%, and the balance of Fe and inevitable impurities.
The heat treatment method of the embodiment comprises the steps of quenching treatment of a hot rolled bearing steel material → water cooling treatment → isothermal spheroidizing annealing treatment → furnace cooling treatment.
The quenching temperature of the hot rolled bearing steel is 920 ℃, and the heat preservation time is 8 hours, so that the carbide is further dissolved and diffused. And (3) cooling the bar by water for 2-3 min after quenching and heat preservation are finished, and controlling the temperature of the bar to be 600-650 ℃ after water cooling. And (3) heating to 790 ℃ and preserving heat for 13h, cooling to 690 ℃ along with the furnace at a cooling speed of 10-15 ℃/h and preserving heat for 5h to finish the tissue transformation, thereby obtaining the spherical or granular carbide tissue uniformly distributed on the ferrite matrix. Cooling the mixture to 600 ℃ along with the furnace at a cooling speed of 20 ℃/h, and then performing air cooling.
Example 3
The embodiment provides a heat treatment method of large-specification bearing steel with the section diameter of 150 mm.
The raw materials are bearing steel hot rolling materials with the section diameter of 150mm, and the bearing steel comprises the following chemical components in percentage by weight: c: 0.97%, Si: 0.21%, Mn: 0.28%, P: 0.014%, S: 0.001%, Als: 0.009%, Alt: 0.011%, Cr: 1.43%, Ni: 0.02%, Mo: 0.004%, V: 0.003%, Ti: 0.0010%, and the balance of Fe and inevitable impurities.
The heat treatment method of the embodiment comprises the steps of quenching treatment of a hot rolled bearing steel material → water cooling treatment → isothermal spheroidizing annealing treatment → furnace cooling treatment.
The quenching temperature of the hot rolled bearing steel is 940 ℃, and the heat preservation time is 8h, so that the carbide is further dissolved and diffused. And (3) performing water cooling for 2-3 min after quenching and heat preservation, controlling the temperature of the bar material to be 600-650 ℃ after water cooling, raising the temperature to 810 ℃, preserving the heat for 13h, performing furnace cooling at a cooling speed of 10-15 ℃/h to 710 ℃, preserving the heat for 5h, completing the tissue transformation, and obtaining the tissues of spherical or granular carbides uniformly distributed on the ferrite matrix. Cooling the mixture to 600 ℃ along with the furnace at a cooling speed of 20 ℃/h, and then performing air cooling.
The distribution of the net-like carbides of the bearing steel raw materials in the hot rolled state in examples 1-3 was examined according to GB/T18254-2016. As shown in FIGS. 1-3, the grades of the net-like carbides of the core of the hot rolled bearing steel raw materials with phi 90mm, phi 110mm and phi 150mm were all greater than 3 grades.
The distribution of the net-shaped carbides of the bearing steels of examples 1-3 after heat treatment was examined according to GB/T18254-2016, and the results are shown in FIGS. 4-12 and Table 1.
TABLE 1
As can be seen from the comparison between the distribution of the reticulated carbides shown in FIGS. 4 to 12 and the levels of the reticulated carbides shown in Table 1, the heat treatment method provided by the present invention can effectively control the distribution of the reticulated carbides at the core of the large-size bearing steel and reduce the levels of the reticulated carbides of the large-size bearing steel.
The test of the full-section network carbide was performed every 5mm for the phi 150mm bearing steel after the heat treatment of example 3, and the results are shown in fig. 13 to 25 and table 2.
TABLE 2
As can be seen from the distribution of the reticulated carbides shown in FIGS. 13 to 25 and the reticulated carbide grades shown in Table 2, reticulated carbides begin to appear at the radius 1/2R, with the reticulated carbides being of grade 1 to 2 and the reticulated carbides being of grade 2.5 at the center.
The hardness of the bearing steels of examples 1 to 3 after heat treatment was examined, and the results are shown in Table 3.
TABLE 3
The data in Table 3 show that the hardness of the bearing steel after heat treatment can be stably controlled to be 180-190 HBW, the hardness standard of 179-207 HBW after GB/T18254 standard spheroidizing annealing is met, and the problems that the bearing steel after quenching is high in hardness and difficult to machine are solved.
As a result of observing the microstructures of the cross-sectional edge, 1/2R and the core of the heat-treated bearing steel of Φ 150mm in example 3, all the microstructures of the cross-sectional edge, 1/2R and the core were granular pearlite and rated at 2.0 as shown in FIGS. 26 to 28. Therefore, the bearing steel obtained by the heat treatment process has uniform and stable microstructure.
The maximum specification of the bearing steel applicable to the heat treatment method provided by the invention can reach 150mm, and the product requirements of the cold-processed bearing steel for large-size rolling bodies of large-scale high-end equipment bearings such as high-power wind power and shield machines can be met.
Example 4
The embodiment provides a heat treatment method of large-specification bearing steel with the cross section diameter of 100 mm.
The raw materials are bearing steel hot rolling materials with the section diameter of 100mm, and the bearing steel comprises the following chemical components in percentage by weight: c: 0.96%, Si: 0.23%, Mn: 0.29%, P: 0.007%, S: 0.006%, Als: 0.013%, Alt: 0.015%, Cr: 1.43%, Ni: 0.02%, Mo: 0.006%, V: 0.002%, Ti: 0.0010%, and the balance of Fe and inevitable impurities.
The heat treatment method of the embodiment comprises the steps of quenching treatment of a hot rolled bearing steel material → water cooling treatment → isothermal spheroidizing annealing treatment → furnace cooling treatment.
The quenching temperature of the hot rolled bearing steel is 935 ℃, and the heat preservation time is 8 hours, so that the carbide is further dissolved and diffused. And (3) performing water cooling for 2-3 min after quenching and heat preservation, controlling the temperature of the bar material to be 600-650 ℃ after water cooling, raising the temperature to 805 ℃ and preserving the temperature for 13h, and performing furnace cooling to 705 ℃ at a cooling speed of 10-15 ℃/h and preserving the temperature for 5h to finish the tissue transformation, thereby obtaining the tissues of spherical or granular carbides uniformly distributed on the ferrite substrate. Cooling the mixture to 600 ℃ along with the furnace at a cooling speed of 20 ℃/h, and then performing air cooling.
Claims (6)
1. The heat treatment method for reducing the level of the steel-mesh carbide of the large-size bearing is characterized by comprising bearing steel quenching treatment → water cooling treatment → isothermal spheroidizing annealing treatment → furnace cooling treatment, wherein the quenching temperature is 930 +/-10 ℃, water cooling is carried out for 2-3 min after quenching and heat preservation are finished, and the steel temperature is controlled to be 600-650 ℃ after water cooling; the isothermal spheroidizing annealing treatment is to firstly raise the temperature to 800 +/-10 ℃ and preserve heat for 13 hours, and then lower the temperature to 700 +/-10 ℃ and preserve heat for 5 hours.
2. The heat treatment method for reducing the level of the large-specification bearing steel reticulated carbides according to claim 1, wherein the large-specification bearing steel has a cross-sectional diameter of not less than 40 mm.
3. The heat treatment method for reducing the level of the steel mesh carbide of the large-specification bearing, according to the claim 1 or 2, is characterized in that the quenching treatment holding time is 8 h.
4. The heat treatment method for reducing the grade of the steel-mesh carbide of the large-specification bearing according to claim 3, wherein the temperature reduction speed from 800 +/-10 ℃ to 700 +/-10 ℃ in the isothermal spheroidizing annealing process is 10-15 ℃/h.
5. The heat treatment method for reducing the grade of the steel mesh carbide of the large-specification bearing according to claim 4, wherein the furnace cooling treatment is air cooling after cooling to 600 ℃ at a cooling speed of 20 ℃/h.
6. The heat treatment method for reducing the level of the large-specification bearing steel reticulated carbide, according to claim 5, is characterized in that the chemical composition of the bearing steel comprises the following components in percentage by weight: c: 0.96-0.97%, Si: 0.21-0.24%, Mn: 0.28-0.29%, P: 0.007-0.014%, S: 0.001-0.006%, Als: 0.009-0.013%, Alt: 0.011-0.015%, Cr: 1.43%, Ni: 0.02%, Mo: 0.001-0.006%, V: 0.002-0.003%, Ti: 0.0010%, and the balance of Fe and inevitable impurities.
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| CN202110719928.5A CN113337693B (en) | 2021-06-28 | 2021-06-28 | Heat treatment method for reducing grade of large-size bearing steel net-shaped carbide |
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