CN115637378B - Bearing steel for rolling bodies and manufacturing method thereof - Google Patents
Bearing steel for rolling bodies and manufacturing method thereof Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 147
- 239000010959 steel Substances 0.000 title claims abstract description 147
- 238000005096 rolling process Methods 0.000 title claims abstract description 98
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 21
- 238000000137 annealing Methods 0.000 claims abstract description 16
- 239000012535 impurity Substances 0.000 claims abstract description 12
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- 238000005266 casting Methods 0.000 claims abstract description 10
- 238000009792 diffusion process Methods 0.000 claims abstract description 9
- 238000003723 Smelting Methods 0.000 claims abstract description 8
- 229910001562 pearlite Inorganic materials 0.000 claims abstract description 8
- 238000007670 refining Methods 0.000 claims abstract description 8
- 238000002791 soaking Methods 0.000 claims abstract description 8
- 229910052729 chemical element Inorganic materials 0.000 claims abstract description 7
- 238000007599 discharging Methods 0.000 claims abstract description 4
- 238000000034 method Methods 0.000 claims description 30
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- 229910052739 hydrogen Inorganic materials 0.000 claims description 5
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- 229910052748 manganese Inorganic materials 0.000 claims description 4
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- 230000008569 process Effects 0.000 description 15
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- 238000009749 continuous casting Methods 0.000 description 4
- 238000001816 cooling Methods 0.000 description 4
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- 238000005496 tempering Methods 0.000 description 4
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 3
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- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 1
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- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910052797 bismuth Inorganic materials 0.000 description 1
- JCXGWMGPZLAOME-UHFFFAOYSA-N bismuth atom Chemical compound [Bi] JCXGWMGPZLAOME-UHFFFAOYSA-N 0.000 description 1
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- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 1
- 239000004571 lime Substances 0.000 description 1
- 229910000734 martensite Inorganic materials 0.000 description 1
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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
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Abstract
The invention discloses bearing steel for rolling bodies, which contains Fe and unavoidable impurities and also contains the following chemical elements in percentage by mass: c:0.75 to 0.85 percent, si:0.25 to 0.35 percent, mn:0.25 to 0.35 percent, cr:2.0-3.0%, mo:0.50 to 0.65 percent of Al:0.01 to 0.04 percent; the microstructure of the bearing steel for rolling bodies is granular pearlite+residual carbide. In addition, the invention also discloses a manufacturing method of the bearing steel for the rolling element, which comprises the following steps: (1) smelting, refining and casting; (2) rolling, which comprises: high-temperature diffusion is carried out in a soaking furnace, and square billets and bars are rolled by blooming; (3) spheroidizing annealing: after the heat preservation for 2-4 hours at 400-500 ℃, the temperature is raised to 800-880 ℃ at the speed of less than or equal to 60 ℃/h for heat preservation for 4-12 hours, then the temperature is reduced to 720-760 ℃ at the speed of less than or equal to 50 ℃/h for heat preservation for 4-6 hours, and then the temperature is reduced to 350-400 ℃ at the speed of 20-40 ℃/h for discharging.
Description
Technical Field
The present invention relates to a steel material and a method for manufacturing the same, and more particularly, to a bearing steel and a method for manufacturing the same.
Background
As is well known, rolling elements are core elements in rolling bearings, which mainly include steel balls and rollers, and based on rolling elements, rolling friction occurs between relatively moving surfaces.
At present, high-end rolling bodies are mainly represented by two major categories of automobile hub steel balls and wind-driven rollers. The automobile hub steel ball can be applied to an automobile wheel shaft and used for bearing and providing accurate guide for rotation of a hub. In the running process of the automobile, the automobile hub bearing bears radial force and axial force, and simultaneously runs at high speed, so that the automobile hub bearing is one of key parts in an automobile driving structure and is also one of parts related to the running safety of the automobile. The automobile hub bearing unit is an automobile part product which is manufactured by integrally designing main parts such as a hub bearing mounting flange, a hub bearing, a connecting mandrel of a hub and a brake disc or a wheel shaft, related sealing parts, a wheel speed sensor, a magnetic encoder and the like.
However, in practical applications, bearings used in construction machines, mining, excavation, and other machinery often need to operate in harsh environments. Because the working environment of the bearing is very harsh, it often needs to withstand excessive impact loads and the service life is often very low.
In the prior art, the practical application conditions of traditional high-carbon chromium bearing steels such as GCr15, GCr15SiMn and the like are not ideal, and the steels have certain wear resistance due to higher carbon content, but have weaker impact resistance, and meanwhile, due to higher carbon content, the generated carbide can have larger influence on contact fatigue life in the steels. Thus, there is an urgent need for a new bearing steel for rolling elements having high toughness, long service life, and excellent wear resistance.
In response to this requirement, some researchers have conducted related researches on bearing steel, and have achieved a certain research result:
for example: the Chinese patent literature with publication number of CN102605256A and publication day of 2012, 7 month and 5 days, named as 'rare earth doped bearing steel and preparation method thereof', essentially discloses high-carbon chromium bearing steel, which is prepared by adding rare earth elements and adopting a vacuum induction and remelting process method to improve toughness, and the invention has high manufacturing cost and is not easy to control the addition of the rare earth elements.
Also for example: the four Chinese patent documents with publication numbers of CN100587099A, CN101724742A, CN101624677A and CN101376948A have the common characteristic that Cr is not added, and relatively good toughness is obtained by adopting micro-alloy elements such as V, nb, ti, re and the like to solve the problem of impact performance, but the technical scheme is difficult to meet the impact performance under the complex working condition.
For another example: two japanese patent documents with publication numbers JP07278740 and JPs62274052, both disclose carburized bearing steels, which reach surface wear resistance through a surface carburization process, and the internal structure after heat treatment is tempered sorbite, and the obtained carburized bearing steels have high toughness, although they can meet complex working conditions, the carburization process of this technical scheme is very complex, which is difficult for general bearing manufacturing enterprises to master or has high manufacturing cost.
From this, the existing bearing steel for high-toughness rolling elements has the following disadvantages: (1) The toughness of the high-carbon chromium bearing steel in the prior art is poor; (2) The Cr-Ni bearing steel in the prior art, such as carburized bearing steel of G20CrNi2MoA, G20Cr2Ni4Mo and the like, has the problems of high content of noble alloy elements and high production cost on one hand and complex carburization process on the other hand, and is difficult to meet the low-cost process requirement; (3) The bearing steel without Cr and Ni in the prior art can solve the carbide problem, but is difficult to solve the requirement on the toughness of the bearing steel under the complex working condition.
Based on the above, the present invention is expected to obtain a new bearing steel for rolling bodies which can obtain very excellent performance by reasonable chemical composition design and cooperation with an optimization process; the bearing steel for the rolling bodies can be prepared into bearing products, the prepared bearing products can be effectively applied to the fields of wind power, engineering machinery, mining, excavation and the like, are in service under severe working environments, have excellent impact resistance, can bear excessive impact load, have long service life, and have very good popularization prospect and application value, and the service life of the bearing steel is obviously better than that of the traditional bearing steel such as GCr15, GCr18Mo and the like.
Disclosure of Invention
The invention aims to provide the bearing steel for the rolling element with impact resistance and high toughness, the bearing steel for the rolling element can be used for preparing bearing products, the prepared bearing products can be effectively applied to the fields of wind power, engineering machinery, mining, excavation and the like, the bearing products are in service under severe working environments, the impact resistance is excellent, excessive impact load can be born, the service life is long, the service life is obviously longer than that of the traditional bearing steel such as GCr15, GCr18Mo and the like, and the bearing steel has good popularization prospect and application value.
In order to achieve the above object, the present invention provides a bearing steel for rolling elements, which contains Fe and unavoidable impurities, and which further contains the following chemical elements in mass percent:
C：0.75～0.85％，Si：0.25～0.35％，Mn：0.25～0.35％，Cr：2.0-3.0％，Mo：0.50～0.65％，Al：0.01～0.04％；
the microstructure of the bearing steel for rolling bodies is granular pearlite+residual carbide.
Further, in the bearing steel for rolling elements according to the present invention, the mass percentages of the chemical elements are:
c:0.75 to 0.85 percent, si:0.25 to 0.35 percent, mn:0.25 to 0.35 percent, cr:2.0-3.0%, mo:0.50 to 0.65 percent of Al:0.01 to 0.04 percent; the balance being Fe and unavoidable impurity elements.
In the bearing steel for rolling elements according to the present invention, the design principle of each chemical element is as follows:
c: in the bearing steel for rolling elements according to the present invention, it is considered that the addition of C element deteriorates the toughness of the steel. However, the element C is an important element for ensuring the strength and wear resistance of the bearing steel, and if a certain strength level is to be ensured in the bearing steel for high-toughness rolling elements, a certain C content must be added to the steel. Based on the above, the beneficial effects and adverse effects of the element C are comprehensively considered, and the weight percentage of the element C is controlled to be between 0.75 and 0.85 percent in the bearing steel for the rolling body.
Si: in the bearing steel for the rolling body, si element can partially replace chromium and nickel element to act, so that the strength of the steel is improved; in addition, si is also a good reducing agent and deoxidizing agent in the smelting process. Meanwhile, the concentration gradient of C in steel can be effectively reduced to promote carbon diffusion in an austenitic state, and the Si element can inhibit precipitation of carbide, so that the toughness of the steel can be improved. In the bearing steel for rolling elements according to the present invention, the mass percentage of Si element is controlled to be 0.25 to 0.35%.
Mn: in the bearing steel for rolling elements according to the present invention, mn element can partially replace chromium to maintain the strength of the bearing steel, and Mn is also a main element that significantly improves the hardenability of the bearing steel. However, it should be noted that the content of Mn element in the steel is not too high, and the Mn element has a disadvantage of promoting the growth of austenitized crystal grains in the steel, and the content of Mn element needs to be controlled in order to ensure the performance of the bearing steel. Based on this, in the bearing steel for rolling elements according to the present invention, the mass percentage of Mn element is controlled to be 0.25 to 0.35%.
Cr: when the carbon content of the common high-carbon chromium bearing steel in the prior art is about 1 percent, about 1.5 percent of Cr is generally required to be added, and the bearing steel also contains a small amount of Mn and Si elements. In the bearing steel for rolling bodies, a certain amount of Cr element is required to be added, so that the heat treatment performance, the hardenability, the structure uniformity and the tempering stability of the steel can be effectively improved, and the rust resistance and the grinding performance of the steel can be improved. Based on this, in the bearing steel for rolling elements according to the present invention, the mass percentage of Cr element is controlled to be between 2.0 and 3.0% to improve the non-uniformity of carbide by a high temperature diffusion process, thereby improving the impact toughness and fatigue strength of the steel.
Mo: in the bearing steel for the rolling bodies, mo element not only can effectively refine grains and improve the hardenability of the steel, but also can ensure that the steel has a certain strength level. In addition, the tempering brittleness of the material can be reduced by adding a proper amount of Mo element into the steel, and brittle fracture of the steel in a complex working environment is avoided. The appropriate amount of Mo element has very remarkable effect in the steel, can improve the hardenability of the part core, obviously inhibit the formation of non-martensite, and can improve the surface hardness of the part. Based on this, in the rolling element bearing steel according to the present invention, the mass percentage of Mo element is controlled to be 0.50 to 0.65%.
Al: in the bearing steel for rolling elements according to the present invention, al is a deoxidizer and a refined grain element, but experiments have shown that the content of Al element in the steel is not too high, and when too much Al is added, al tends to be formed 2 O 3 Nonmetallic inclusions, which are difficult to deform, tend to become sources of fatigue fracture, thereby affecting the impact resistance of the steel. Based on this, in the rolling element bearing steel according to the present invention, the mass percentage of Al element is controlled to be 0.01 to 0.04%.
Further, in the bearing steel for rolling elements according to the present invention, each element in the unavoidable impurities satisfies at least one of the following: cu is less than or equal to 0.25%, S is less than or equal to 0.015%, P is less than or equal to 0.015%, O is less than or equal to 0.0008%, ti is less than or equal to 0.0015%, and H is less than or equal to 0.0001%.
In the above technical solution of the present invention, cu, P, S, O, ti and H are both unavoidable impurity elements in steel, and the content of impurity elements in steel needs to be controlled as low as possible under the condition that the technical conditions allow. Among them, cu, P, S are impurity elements in steel, which significantly reduce plasticity and toughness of steel, and particularly, the damage caused by P element is greatest.
In addition, it should be noted that, in addition to the above Cu, P, S, O, ti and H elements, lead, antimony and bismuth are impurity elements in steel at the same time, and the content thereof should be reduced as much as possible under the technical conditions permitting.
Further, in the bearing steel for rolling elements according to the present invention, the grain size is 7 to 11 grades.
Further, in the bearing steel for rolling elements according to the present invention, the impact energy at room temperature is not less than 40J.
Further, in the bearing steel for rolling elements according to the present invention, the brinell hardness thereof is not less than 195HB; under the stress condition of 4.5GPa, the contact fatigue life L of the alloy 10 ≥2.5×10 7 。
Accordingly, another object of the present invention is to provide a method for manufacturing a bearing steel for a rolling element, which is simple and convenient to operate, and the bearing steel for a rolling element manufactured by the method can be manufactured into a bearing product, and the manufactured bearing product can be effectively applied to the fields of wind power, engineering machinery, mining, excavation, etc., is served in a severe working environment, has excellent impact resistance, can bear excessive impact load, has a long service life, and has a good popularization prospect and application value, and the service life of the bearing steel is obviously better than that of the conventional bearing steel such as GCr15 and GCr18 Mo.
In order to achieve the above object, the present invention provides a method for manufacturing the bearing steel for rolling elements, comprising the steps of:
(1) Smelting, refining and casting;
(2) Rolling, comprising: high-temperature diffusion is carried out in a soaking furnace, and square billets and bars are rolled by blooming;
(3) Spheroidizing annealing: after the heat preservation for 2-4 hours at 400-500 ℃, the temperature is raised to 800-880 ℃ at the speed of less than or equal to 60 ℃/h for heat preservation for 4-12 hours, then the temperature is reduced to 720-760 ℃ at the speed of less than or equal to 50 ℃/h for heat preservation for 4-6 hours, and then the temperature is reduced to 350-400 ℃ at the speed of 20-40 ℃/h for discharging.
In the method for manufacturing the bearing steel for the rolling element, the three-step process flow can be adopted: the first step: primary smelting in an electric arc furnace (or a converter), vacuum refining in a ladle furnace and continuous casting pouring; and a second step of: hot working and rolling into a material by a rolling mill; and a third step of: and (5) spheroidizing annealing.
In the step (1), the primary smelting of molten steel can be controlled in an electric arc furnace (or a converter) with the weight of 20-250 tons, then refining is performed in a ladle furnace with the corresponding tonnage, and then continuous casting is performed to produce a continuous casting blank with a certain size and chemical components meeting the regulations.
In the primary melting furnace (arc furnace or converter), the molten steel may be obtained by: p is less than or equal to 0.035%, C is more than or equal to 0.05%, and T is more than or equal to 1620 ℃. Proper amount of lime or synthetic slag is required to be added in the later stage of tapping, then chemical components are adjusted to be controlled internally when the ladle furnace is refined, al is added to 0.02-0.05% in the initial deoxidation of the ladle furnace, and stirring is carried out for more than or equal to 5 minutes; then, in a vacuum degassing furnace, the vacuum degree is controlled to be less than or equal to 133Pa, and the vacuum refining of molten steel is completed after the vacuum degree is maintained at the pressure for more than or equal to 15 minutes. After refining, casting is needed, and the casting is cast into rectangular blanks with the size of 320mm multiplied by 425mm or other sizes.
Accordingly, in the spheroidizing annealing of the step (3) of the present invention, the annealing temperature is controlled to be 800-880 ℃ and kept for 4-12 hours, so that the hardness of the obtained bearing steel for rolling bodies can be ensured. In general, when the annealing temperature of high alloy bearing steel is 860 ℃ after rolling and heating, massive carbide is hardly dissolved, flaky pearlite can be converted into austenite for 30-60 minutes to complete aggregation and partial dissolution, and the annealing heat preservation time is enough to be 1-2 hours in theory, but for spheroidizing annealing heat preservation time in industrial production, the whole furnace steel cannot be uniform and consistent in a short time due to the non-uniformity of original tissues and the different influences of furnace temperature uniformity and furnace charging methods, and the heat preservation time is controlled to be 4-12 hours in actual industrial production.
In addition, the cooling rate after annealing has a remarkable effect on the hardness of the steel, and as the cooling rate increases, the hardness of the steel increases, and in actual industrial production, a satisfactory hardness result can be obtained by controlling the cooling rate to 20 to 40 ℃/hr.
Further, in the manufacturing method of the invention, in the step (2), when the soaking furnace high-temperature diffusion step is carried out, the casting blank feeding temperature is controlled to be 600-900 ℃, and the heat is preserved for 20-40 min; then heating to 1200-1240 ℃ for 120-200 min, and preserving heat.
Further, in the manufacturing method of the present invention, in the step (2), when the bar is rolled, the heating temperature is controlled to be 1160-1200 ℃, the heating time is controlled to be 80-120 min, and then the bar is discharged when the temperature difference between the negative surface and the positive surface of the square billet is less than or equal to 40 ℃.
Further, in the manufacturing method according to the present invention, in the step (2), the finishing temperature is controlled to 760 to 900 ℃ when the bar is rolled.
Compared with the prior art, the bearing steel for the rolling element and the manufacturing method thereof have the following advantages and beneficial effects:
the invention designs a bearing steel for rolling bodies, which can be obtained by adding alloy elements such as chromium, molybdenum and the like into steel and designing corresponding components, and performing smelting, vacuum refining, casting, rolling and annealing.
The bearing steel for the rolling body can obtain the microstructure of the granular pearlite and the residual carbide through reasonable chemical component design and matching with an optimization process, and has very excellent performance; the bearing steel for the rolling bodies has high purity and low inclusion level (the detection according to GB/T10561 can be satisfied that A is less than or equal to 2, B is less than or equal to 2, C is less than or equal to 1, D is less than or equal to 1), O is less than or equal to 8ppm, H is less than or equal to 1ppm in the gas content, the grain size is 7-11 levels, the impact energy at room temperature is more than or equal to 40J, and the Brinell hardness is more than or equal to 195HB; in addition, the contact fatigue life L of the bearing steel for rolling elements under the stress condition of 4.5GPa 10 ≥2.5×10 7 。
The bearing steel for the rolling bodies can be rolled into bars or wires to prepare bearing products, and the prepared bearing products can be effectively applied to the fields of wind power, engineering machinery, mining, excavation and the like, are good in impact resistance and capable of bearing excessive impact load under severe working environments, have long service life, are obviously better than the traditional bearing steel such as GCr15, GCr18Mo and the like, and have very good popularization prospect and application value.
Drawings
Fig. 1 is a microstructure photograph of the bearing steel for rolling elements of example 1.
Fig. 2 is a microstructure photograph of the bearing steel for rolling elements of example 2.
Fig. 3 is a microstructure photograph of the bearing steel for rolling elements of example 3.
Detailed Description
The bearing steel for rolling bodies and the method for manufacturing the same according to the present invention will be further explained and illustrated with reference to the drawings and specific examples, but the explanation and illustration do not constitute an undue limitation on the technical solution of the present invention.
Examples 1 to 7
The bearing steels for rolling elements of examples 1 to 7 were each prepared by the following steps:
(1) Smelting is carried out according to the chemical composition ratio shown in table 1, wherein molten steel is initially smelted in a 150-ton electric arc furnace, then refined in a ladle furnace with corresponding tonnage, and then continuous casting is carried out, so as to produce a square billet with chemical composition meeting the regulation of 320mm multiplied by 425 mm.
(2) Rolling, comprising: and (5) diffusing at high temperature in the soaking furnace, and performing blooming to form square billets and bar rolling. When the casting blank is fed into a soaking pit for high-temperature diffusion, controlling the feeding temperature of the casting blank to be 600-900 ℃ and preserving heat for 20-40 min; then heating to 1200-1240 ℃ for 120-200 min, and then preserving heat for a period of time; after finishing the high-temperature diffusion of the soaking pit, the blooming mill rolls and blooms the qualified steel ingot into 200mm multiplied by 200mm square billets according to the conventional rolling process; when the bar is rolled, the billet is transferred to a heating furnace of a rolling mill for heating, the heating temperature is controlled to be 1160-1200 ℃, the heating time is controlled to be 80-120 min, then the billet is discharged from the furnace when the temperature difference between the negative surface and the positive surface of the square billet is less than or equal to 40 ℃, and when the bar is rolled, the final rolling temperature is controlled to be 760-900 ℃.
(3) Spheroidizing annealing: the hot rolled steel bar enters an annealing furnace, is heated to 800-880 ℃ for 4-12 hours at the speed of less than or equal to 60 ℃/h after being insulated for 2-4 hours at 400-500 ℃, is cooled to 720-760 ℃ for 4-6 hours at the speed of less than or equal to 50 ℃/h, and is cooled to 350-400 ℃ for discharging at the speed of 20-40 ℃/h.
It should be noted that the bearing steels for rolling elements in examples 1 to 7 according to the present invention were prepared by the above steps, and the chemical components and the related process parameters thereof all meet the control requirements of the design specifications of the present invention. 7 groups of high-toughness bearing steel with different chemical components are produced by adopting the manufacturing process, and rolled into steel bars with the diameter range of 50-120 mm.
Table 1 shows the mass percentages of the respective chemical elements in the bearing steels for rolling elements of examples 1 to 7.
Table 1 (balance Fe and unavoidable impurities other than Cu, P, S, O, ti and H)
Tables 2-1 and 2-2 list specific process parameters of step (1) to step (3) in the above-described manufacturing process for bearing steels for rolling bodies of examples 1-7.
Table 2-1.
Table 2-2.
The bearing steels for rolling elements of examples 1 to 7 obtained after spheroidizing annealing were sampled, and the bearing steels for rolling elements of examples 1 to 7 were observed and analyzed, and the microstructure of the bearing steels for rolling elements of examples 1 to 7 was found to be granular pearlite+residual carbide.
After the observation analysis was completed, various performance tests were conducted on the bearing steels for rolling bodies of examples 1 to 7 to determine the brinell hardness, impact work at room temperature and contact fatigue life of the bearing steels for rolling bodies of examples 1 to 7, and the test results obtained are shown in table 3.
The relevant performance test means are as follows:
brinell hardness test: part 1 of the Brinell hardness test of metals according to GB/T231.1: test methods the samples of each example were tested to determine the brinell hardness of the bearing steels for rolling bodies of examples 1 to 7.
U-notch test: the notch depth was controlled to 2mm, and the impact energy of the bearing steels for rolling elements of examples 1 to 7 at room temperature (20 ℃ C.) was measured.
Contact fatigue life test: the contact fatigue life of the bearing steels for rolling bodies of examples 1 to 7 under the stress condition of 4.5GPa was measured by controlling the contact stress level to be 4.5GPa and the rotational speed to be 1800r/min and performing the test according to the contact fatigue test method of the JB/T10510-2019 rolling bearing material.
Table 3 shows the results of various performance tests of the bearing steels for rolling elements of examples 1 to 7.
Table 3.
As can be seen from table 3, the bearing steels for rolling elements of examples 1 to 7 according to the present invention have grain sizes between 7 and 11 grades after spheroidizing annealing; accordingly, the bearing steels for rolling elements of examples 1 to 7 each had Brinell hardness of 195HB-210HB and impact energy at room temperature of 40-66J, and contact fatigue life L under stress conditions of 4.5GPa 10 At 2.5X10 7 -6.2×10 7 Between them.
From this, it can be seen that the bearing steels for rolling elements of examples 1 to 7 are excellent in mechanical properties, have not only a high brinell hardness but also excellent impact resistance and contact fatigue life, and are very wide in applicability, having a good popularization prospect and application value.
Correspondingly, the bars rolled by the bearing steel for the rolling bodies in the embodiments 1-7 can be further used for preparing bearing products, and the prepared bearing products can be effectively applied to the fields of wind power, engineering machinery, mining, excavation and the like and are used in a severe working environment.
In order to verify the above method, the bearing steels for rolling elements of examples 1 to 7 obtained by spheroidizing annealing may be further quenched and tempered, and then the corresponding bearing articles may be produced. Wherein, the quenching and tempering process can be selected as follows: oil quenching at 840-870 deg.c and tempering at 170-210 deg.c. The carbide properties of the bearing products corresponding to the rolling element bearing steel bars of examples 1 to 7 were obtained by analyzing the bearing products obtained by the bar materials, and the carbide properties of the bearing products corresponding to the production of examples 1 to 7 are shown in Table 4 below.
In addition, the austenite grain sizes of the bearing products produced in accordance with the bearing steels for rolling bodies of examples 1 to 7 can be further examined, and the heat treatment process can be controlled: preserving heat for 45-60 min at 830-860 ℃ and cooling with oil. The austenite grain sizes of the bearing products corresponding to examples 1 to 7 were thus obtained, and the relevant test data are shown in Table 4 below.
Table 4.
As shown in Table 4, the austenite grain sizes of the bearing products corresponding to examples 1-7 were 7-8 grades, and the liquid-out carbides of the produced bearing products were not more than 0.5; the mesh tissue grade is less than or equal to 2.5; the band-shaped tissue grade is less than or equal to 2.5, and the performance is very excellent.
Fig. 1 is a microstructure photograph of the bearing steel for rolling elements of example 1.
Fig. 2 is a microstructure photograph of the bearing steel for rolling elements of example 2.
Fig. 3 is a microstructure photograph of the bearing steel for rolling elements of example 3.
As shown in fig. 1, 2 and 3, in examples 1 to 3, the microstructure of the bearing steel for rolling elements according to the present invention was granular pearlite+residual carbide.
From the above, it can be seen that the bearing steel for rolling bodies according to the present invention can obtain a microstructure of granular pearlite+residual carbide, which has very excellent properties, through reasonable chemical composition design and cooperation with an optimization process; the bearing steel for the rolling bodies has high purity and low inclusion level (the detection according to GB/T10561 can be satisfied that A is less than or equal to 2, B is less than or equal to 2, C is less than or equal to 1, D is less than or equal to 1), O is less than or equal to 8ppm, H is less than or equal to 1ppm in the gas content, the grain size is 7-11 levels, the impact energy at room temperature is more than or equal to 40J, and the Brinell hardness is more than or equal to 195HB; in addition, the contact fatigue life L of the bearing steel for rolling elements under the stress condition of 4.5GPa 10 ≥2.5×10 7 。
The bearing steel for the rolling bodies can be rolled into bars or wires to prepare bearing products, and the prepared bearing products can be effectively applied to the fields of wind power, engineering machinery, mining, excavation and the like, are good in impact resistance and capable of bearing excessive impact load under severe working environments, have long service life, are obviously better than the traditional bearing steel such as GCr15, GCr18Mo and the like, and have very good popularization prospect and application value.
It should be noted that the prior art part in the protection scope of the present invention is not limited to the embodiments set forth in the present application, and all prior art that does not contradict the scheme of the present invention, including but not limited to the prior patent document, the prior publication, the prior disclosure, the use, etc., can be included in the protection scope of the present invention.
In addition, the combination of the features described in the present application is not limited to the combination described in the claims or the combination described in the embodiments, and all the features described in the present application may be freely combined or combined in any manner unless contradiction occurs between them.
It should also be noted that the above-mentioned embodiments are merely examples of the present invention, and it is obvious that the present invention is not limited to the above-mentioned embodiments, and many similar variations are followed. All modifications attainable or obvious from the present disclosure set forth herein should be deemed to be within the scope of the present disclosure.
Claims (7)
1. A bearing steel for rolling bodies contains Fe and unavoidable impurities, and is characterized by further containing the following chemical elements in percentage by mass:
C：0.75～0.85％，Si：0.25～0.35％，Mn：0.25～0.35％，Cr：2.15-3.0％，Mo：0.55～0.65％，Al：0.01～0.04％；
the microstructure of the bearing steel for the rolling bodies is granular pearlite and residual carbide; the grain size is 7-11 grade;
the Brinell hardness of the alloy is more than or equal to 195HB; under the stress condition of 4.5GPa, the contact fatigue life L of the alloy 10 ≥2.5×10 7 The method comprises the steps of carrying out a first treatment on the surface of the The impact energy at room temperature is more than or equal to 40J.
2. The bearing steel for rolling elements according to claim 1, wherein the mass percentages of the chemical elements are:
C：0.75～0.85％，Si：0.25～0.35％，Mn：0.25～0.35％，Cr：2.15-3.0％，
mo:0.55 to 0.65 percent of Al:0.01 to 0.04 percent; the balance being Fe and unavoidable impurity elements.
3. Bearing steel for rolling elements according to claim 1 or 2, characterized in that each element in the unavoidable impurities satisfies at least one of the following: cu is less than or equal to 0.25%, S is less than or equal to 0.015%, P is less than or equal to 0.015%, O is less than or equal to 0.0008%, ti is less than or equal to 0.0015%, and H is less than or equal to 0.0001%.
4. A method of manufacturing a bearing steel for rolling elements according to any one of claims 1 to 3, comprising the steps of:
(1) Smelting, refining and casting;
(2) Rolling, comprising: high-temperature diffusion is carried out in a soaking furnace, and square billets and bars are rolled by blooming;
(3) Spheroidizing annealing: after the heat preservation for 2-4 hours at 400-500 ℃, the temperature is raised to 800-880 ℃ at the speed of less than or equal to 60 ℃/h for heat preservation for 4-12 hours, then the temperature is reduced to 720-760 ℃ at the speed of less than or equal to 50 ℃/h for heat preservation for 4-6 hours, and then the temperature is reduced to 350-400 ℃ at the speed of 20-40 ℃/h for discharging.
5. The method according to claim 4, wherein in the step (2), when the soaking furnace high temperature diffusion step is performed, the casting blank is controlled to have a furnace-in temperature of 600 to 900 ℃ and is kept for 20 to 40 minutes;
then heating to 1200-1240 ℃ for 120-200 min, and preserving heat.
6. The method according to claim 4, wherein in the step (2), the heating temperature is 1160 to 1200 ℃ and the heating time is 80 to 120 minutes when the bar is rolled, and the bar is discharged when the temperature difference between the negative surface and the positive surface of the square billet is not more than 40 ℃.
7. The method according to claim 4, wherein in the step (2), the finishing temperature is controlled to 760 to 900 ℃ when the bar is rolled.
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| US4642219A (en) * | 1984-03-14 | 1987-02-10 | Aichi Steel Works, Ltd. | Bearing steel and method of manufacturing the same |
| CN110484837A (en) * | 2019-08-16 | 2019-11-22 | 江阴兴澄特种钢铁有限公司 | A kind of ball-screw steel and its manufacturing method |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JPH11335773A (en) * | 1998-05-22 | 1999-12-07 | Nippon Koshuha Steel Co Ltd | Bearing steel excellent in cold workability |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4642219A (en) * | 1984-03-14 | 1987-02-10 | Aichi Steel Works, Ltd. | Bearing steel and method of manufacturing the same |
| CN110484837A (en) * | 2019-08-16 | 2019-11-22 | 江阴兴澄特种钢铁有限公司 | A kind of ball-screw steel and its manufacturing method |
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| 刘红.《工程材料》.北京理工大学出版社,2019,第124-126页. * |
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