CN116200581A - Surface strengthening method for bearing steel and bearing steel - Google Patents
Surface strengthening method for bearing steel and bearing steel Download PDFInfo
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- CN116200581A CN116200581A CN202211538324.1A CN202211538324A CN116200581A CN 116200581 A CN116200581 A CN 116200581A CN 202211538324 A CN202211538324 A CN 202211538324A CN 116200581 A CN116200581 A CN 116200581A
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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
- C21D7/00—Modifying the physical properties of iron or steel by deformation
- C21D7/02—Modifying the physical properties of iron or steel by deformation by cold working
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Abstract
The application provides a surface strengthening method of bearing steel and the bearing steel, which comprises the following steps: step (1): carrying out surface gradient micro-nano treatment on the bearing steel to form a nano-micro gradient structure on the surface of the bearing steel; the nano-micron gradient structure forms a gradient strengthening layer on the surface of the bearing steel. According to the surface strengthening method of the bearing steel and the bearing steel, the surface of the bearing steel can be effectively strengthened.
Description
Technical Field
The application relates to the technical field of material processing, in particular to a surface strengthening method of bearing steel and the bearing steel.
Background
Numerous examples show that the primary forms of aero-bearing failure are surface contact fatigue failure and frictional wear failure, the core generally remains intact, and therefore a suitable bearing steel surface treatment process is critical to the reliability of the bearing. The most widely used high temperature steel for aviation bearings is M50 steel at present; compared with the conventional bearing steel GCr15, the steel has better dimensional stability and higher hardness under the high-temperature condition. Therefore, the M50 steel is widely applied to the field of high-end equipment which is frequently subjected to high temperature, high speed and heavy load, such as an aeroengine, an aerospace craft, a naval vessel and the like. The M50 steel has the most outstanding advantages of long-term service at the temperature below 315 ℃, good dimensional stability and contact fatigue performance at high temperature, high enough hardness and strength, and good thermal stability of a reinforcing layer prepared on the surface of the M50 steel for the aviation bearing.
Currently, the main methods and approaches for improving the surface properties of M50 steel include:
(1) A hard wear-resistant coating or a coating with a low friction coefficient is deposited on a substrate by a surface coating technique, a beam ion implantation technique and an ion beam assisted deposition technique.
(2) A modified permeation layer with high hardness, antifriction and wear resistance is prepared by nitriding, carburizing, plasma carburizing and other methods.
(3) The reinforced layer with high residual stress is prepared by strong current pulse electron beam irradiation, shot blasting treatment, laser shock shot peening, deep rolling treatment, surface mechanical grinding technology and the like.
However, the above method has a certain problem in practical production and service practice, which is reflected in the following situations:
(1) The surface coating technology has simple operation, low cost and thicker available strengthening layer, but the film base has poor binding force and is easy to fall off. The binding force between the beam line ion implantation modified layer and the matrix is strong, but the beam line ion implantation technology has the limitation of direct injection, so that the uniformity of implantation dosage is poor, the treatment efficiency is low, the cost is high, and the beam line ion implantation modified layer is difficult to apply in the bearing production industry. The ion beam assisted deposition technique combines surface coating with beam line ion implantation, it can obtain a thicker deposition layer on the surface of the material, and the film base has strong binding force, can obtain more remarkable strengthening effect than single surface coating and single ion implantation, but it still has the limitation of ion beam technique straightness, is not suitable for processing parts with complex shapes, and has high processing cost.
(2) Nitriding and carburizing processes are complex and have certain pollution; although the high temperature environment in the nitriding and carburizing processes thickens the carburized layer, the matrix is softened, the crystal grains grow up, and the service performance of the bearing is damaged; the uniformity, depth and tissue consistency of the strike-through layer are also short plates that limit their wide application.
(3) High current pulsed electron beam irradiation is prone to large size pit defects (about 70 μm). The gradient strengthening layer can be prepared by shot blasting, laser shock peening and surface mechanical grinding technology. However, the defects of shot blasting treatment, laser shock peening and surface mechanical grinding treatment are that the prepared sample has high surface roughness, and the subsequent superfinishing process has large removal amount, which is not beneficial to bearing production. The deep rolling treatment can reduce the surface roughness of the workpiece. However, the traditional deep rolling treatment cutter has short service life, high comprehensive use cost and larger damage to the precision and service life of the machine tool.
Therefore, it is an urgent need for a bearing steel and a surface strengthening method of a bearing steel that can effectively strengthen the surface of the bearing steel.
Disclosure of Invention
Therefore, the technical problem to be solved by the application is to provide a surface strengthening method of bearing steel and the bearing steel, which can effectively strengthen the surface of the bearing steel.
In order to solve the above problems, the present application provides a surface strengthening method of bearing steel, comprising the steps of:
step (1): carrying out surface gradient micro-nano treatment on the bearing steel to form a nano-micro gradient structure on the surface of the bearing steel; the nano-micron gradient structure forms a gradient strengthening layer on the surface of the bearing steel.
Further, in the step (1), the equipment adopted for carrying out the surface gradient micro-nano treatment on the bearing steel is micro-nano processing equipment; the micro-nano processing equipment comprises a processing cutter; the processing cutter can roll/grind on the surface of the bearing steel, so that the surface of the bearing steel is subjected to plastic deformation to obtain the nano-micron gradient structure.
Further, the surface gradient micro-nano treatment of the bearing steel comprises the following steps:
first-pass treatment: the cutter head of the machining cutter is pressed into the surface of the rotating bearing steel for the first time, and meanwhile, the cutter head of the machining cutter is fed along the axial direction of the bearing steel or the direction perpendicular to the rotation surface of the bearing steel;
further, according to the surface area of the bearing steel and the machining efficiency of the machining tool, controlling the excircle linear speed v1 and the feeding speed v2 of the rotation of the bearing steel;
further, during the first pass, the outer circular linear velocity v1=50-800 mm/s of the bearing steel rotation; and/or, the press-in depth a of the first press-in p =20-100 μm; and/or the speed of feed v2=1×10 -3 -2×10 -1 mm/r。
Further, the surface gradient micro-nano treatment for the bearing steel further comprises the following steps:
treatment of the n-th pass: pressing the tool bit of the machining tool into the surface of the rotating bearing steel for the nth time, and feeding the tool bit of the machining tool along the axial direction of the bearing steel or the direction perpendicular to the rotating surface of the bearing steel; wherein n=1-8;
further, during the nth pass treatment, the outer circular linear velocity v1=50-800 mm/s of the bearing steel rotation; and/or the press-in depth of the nth press-in is a p * n; and/or the speed of feed v2=1×10 -3 -2×10 -1 mm/r；
And/or controlling the pressing depth and the pressing pass of the first pressing according to the surface strengthening requirement of the bearing steel and the principle of no damage to the machined surface; and/or controlling the press-in depth a of the first press-in according to the surface strengthening requirement of the bearing steel and the principle of no damage to the machined surface p And press-in pass n.
Further, the micro-nano processing equipment comprises surface mechanical rolling processing equipment, wherein the surface mechanical rolling processing technical equipment comprises rolling balls, the rolling balls can freely roll, and the rolling balls form a processing cutter; further, the rolling ball is made of WC-Co hard alloy; and/or the diameter of the rolling ball is 4-10mm;
or the micro-nano processing equipment comprises surface mechanical rolling processing equipment, wherein the surface mechanical rolling processing technical equipment comprises fixed balls, and the fixed balls form a processing cutter; further, the fixing ball is made of WC-Co hard alloy; and/or the diameter of the fixing ball is 4-10mm.
Further, the micro-nano processing equipment comprises an oily lubrication cooling system; the oily lubrication cooling system can provide oily cooling liquid; in the step (1), the oil lubrication cooling system can lubricate and cool the bearing steel in the process of carrying out surface gradient micro-nano treatment on the bearing steel.
Further, the method also comprises the following steps:
step (2): carrying out heat treatment on the bearing steel treated in the step (1) to relax the martensitic substructure interface on the nano-micron gradient structure, thereby forming a stable strengthening layer;
further, the temperature of the heat treatment is 300-550 ℃; and/or the heat treatment time is 1-20h.
Further, the gradient strengthening layer has a thickness of 150-1000 μm; and/or the microhardness peak of the gradient strengthening layer exceeds 9GPa; and/or the surface residual compressive stress of the gradient strengthening layer is greater than 500MPa;
and/or, the bearing steel comprises M50 steel.
Further, before step (1), the method further comprises the following steps:
and grinding the surface of the bearing steel.
According to still another aspect of the present application, there is provided a bearing steel obtained after the bearing steel is treated by the surface strengthening method of the bearing steel described above.
According to the surface strengthening method of the bearing steel and the bearing steel, the surface strengthening method of the bearing steel is simple in implementation mode, the surface of the bearing steel is locally deformed at a high speed in the gradient micro-nano treatment process, dislocation is initiated and intertwined in martensite of the surface layer and the subsurface layer of the bearing steel, the surface is further strengthened, and the surface strength of the bearing steel is enhanced; after the surface gradient micro-nano treatment is carried out on the bearing steel, the surface roughness of the M50 steel is lower than that of the rough grinding and fine grinding state, the Ra value is smaller than 0.2 mu M, the thickness of a gradient strengthening layer on the surface of the M50 steel is 150-1000 mu M, the surface microhardness peak value exceeds 9GPa, the surface residual compressive stress is greater than 500MPa, and the heat stability is excellent at 400 ℃; can effectively strengthen the surface of the bearing steel.
Drawings
FIG. 1 is a schematic diagram of a surface gradient micro-nano process in an embodiment;
FIG. 2 is an organizational chart of M50 steel;
FIG. 3M50 is an org-chart of steel after being subjected to SMRT and 400 ℃ heat treatment for 2 hours;
FIG. 4M50 shows a characteristic dimension of a nano-micro gradient structure of steel after SMRT and heat treatment at 400 ℃ for 2 hours
FIG. 5 is a photograph showing the surface formation of the M50 steel treated by SMRT in the example;
FIG. 6 is a graph showing the microhardness distribution of the gradient strengthening layer of M50 steel for SMGT treated aero bearings in the examples;
FIG. 7 shows the microhardness distribution of the gradient strengthening layer of M50 steel for an SMRT-treated aviation bearing subjected to heat treatment at 300 ℃ for 2 hours in the example;
FIG. 8 is a microhardness distribution of a gradient strengthening layer of M50 steel for an SMRT-treated aviation bearing subjected to heat treatment at 400℃for 2 hours in the example;
FIG. 9 is a comparison of rolling contact fatigue performance of M50 steel with gradient strengthening layer and original samples in the examples.
Detailed Description
Referring to fig. 1-9 in combination, a method for strengthening the surface of bearing steel comprises the following steps:
step (1): carrying out surface gradient micro-nano treatment on the bearing steel to form a nano-micro gradient structure on the surface of the bearing steel; the nano-micron gradient structure forms a gradient strengthening layer on the surface of the bearing steel. The bearing steel is M50 steel for aviation bearings.
The surface strengthening method of the bearing steel is simple in implementation mode, and in the gradient micro-nano treatment process of the surface of the bearing steel, local high-speed deformation is generated on the surface of the bearing steel, dislocation is initiated and entangled in martensite of the surface layer and the subsurface layer of the bearing steel, so that the surface of the bearing steel is strengthened, and the surface strength of the bearing steel is enhanced; after the surface gradient micro-nano treatment is carried out on the bearing steel, the surface roughness of the M50 steel is lower than that of the coarse grinding and fine grinding state, the Ra value is smaller than 0.2M, the thickness of a gradient strengthening layer on the surface of the M50 steel is 150-1000 mu M, the surface microhardness peak value exceeds 9GPa, the surface residual compressive stress is greater than 500MPa, and the heat stability is excellent at 400 ℃.
The application also discloses some embodiments, in the step (1), the equipment adopted for carrying out the surface gradient micro-nano treatment on the bearing steel is micro-nano processing equipment; the micro-nano processing equipment comprises a processing cutter; the processing cutter can roll or grind the surface of the bearing steel, so that the surface of the bearing steel is subjected to plastic deformation to obtain a nano-micron gradient structure, and the nano-micron gradient structure forms a mechanical reinforcing layer. The surface strengthening method of the bearing steel is simple in implementation mode, and can strengthen the bearing steel rotating member. In the surface gradient micro-nano treatment process, the bearing steel rotating member rotates at a high speed, and the tool bit of the gradient micro-nano processing tool is pressed into the surface of the bearing steel to generate local high-speed deformation, so that a great amount of dislocation is generated in a local high-speed deformation area of the bearing steel and intertwined with each other, lath martensite in an original tissue is thinned, the original nano lath martensite is thinned into nano crystals, a nano-micro gradient structure is obtained, and a surface strengthening layer is further generated. The bearing steel can be M50 steel, the M50 steel rotating member rotates at a high speed, and the tool bit of the gradient micro-nano machining tool is pressed into the surface of the M50 steel to generate local high-speed deformation, so that a large number of dislocation are generated in a local high-speed deformation area of the M50 steel and intertwined with each other, lath martensite in an original tissue is thinned, the original nano lath martensite is thinned into nano crystals, and a surface strengthening layer is further generated. The skin layer is generally referred to as a skin layer at a depth of 0-50 microns; the subsurface layer is 50-300 microns. The surface layers and subsurface layers referred to herein are areas of stress applied by the tool tip, i.e., localized stress application areas, in a range of about several hundred microns (and this range is significant). Under the action of stress, new dislocation is generated, more dislocation is easy to be entangled, and the dislocation is difficult to restart, so that strengthening is generated.
The application also discloses some embodiments, wherein the surface gradient micro-nano treatment of the bearing steel comprises the following steps:
first-pass treatment: the cutter head of the machining cutter is pressed into the surface of the rotating bearing steel for the first time, and meanwhile, the cutter head of the machining cutter is fed along the axial direction of the bearing steel or the direction perpendicular to the rotation surface of the bearing steel;
some embodiments are also disclosed, wherein the outer circular linear velocity v1 and the feeding velocity v2 of the bearing steel rotation are controlled according to the surface area of the bearing steel and the machining efficiency of the machining tool.
Some embodiments are also disclosed herein, in which the outer circular linear velocity v1=50-800 mm/s of bearing steel rotation during the 1 st pass treatment; and/or, the press-in depth a of the first press-in p =20-100 μm; and/or the speed of feed v2=1×10 -3 -2×10 -1 mm/r. The reinforced layer obtained by the method has high depth and good thermal stability, and the service life of the aviation bearing can be effectively prolonged. The processing parameters can enable the processing to be uniform and ensure certain processing efficiency.
The application also discloses some embodiments, wherein the surface gradient micro-nano treatment for the bearing steel further comprises the following steps:
treatment of the n-th pass: pressing the tool bit of the machining tool into the surface of the rotating bearing steel for the nth time, and feeding the tool bit of the machining tool along the axial direction of the bearing steel or the direction perpendicular to the rotating surface of the bearing steel; wherein n=1-8; the surface strengthening effect can be further improved, and the more the processing passes are, the more the hardening layer is obvious on the premise of no damage.
Some embodiments are also disclosed in which during the nth pass treatment the bearing steel rotates at an outer circular linear velocity v1=50-800 mm/s; and/or the press-in depth of the nth press-in is a p * n; and/or the speed of feed v2=1×10 -3 -2×10 -1 mm/r。
The application also disclosesSome embodiments are provided, and the pressing depth and the pressing pass of the first pressing are controlled according to the surface strengthening requirement of the bearing steel and the principle of no damage to the processing surface; and/or controlling the press-in depth a of the first press-in according to the surface strengthening requirement of the bearing steel and the principle of no damage to the machined surface p And press-in pass n.
The application also discloses some embodiments, the micro-nano processing equipment comprises surface mechanical rolling processing equipment, the surface mechanical rolling processing technical equipment comprises rolling balls, the rolling balls can freely roll, and the rolling balls form a processing cutter; the application also discloses some embodiments, wherein the rolling ball is made of WC-Co hard alloy; and/or the diameter of the rolling ball is 4-10mm; the rolling ball adopting the hard alloy is hard and low in price, and the cutter is not easy to damage in the use process.
Or the micro-nano processing equipment comprises surface mechanical rolling processing equipment, wherein the surface mechanical rolling processing technical equipment comprises fixed balls, and the fixed balls form a processing cutter; the application also discloses some embodiments, wherein the material of the fixing ball is WC-Co hard alloy; and/or the diameter of the fixing ball is 4-10mm. The fixing ball is directly pressed down on the surface of the bearing steel, the diameter is in the range, the surface strengthening effect is better, and the hardness is greatly improved.
Namely, the adopted surface gradient micro-nano technology comprises a surface mechanical rolling treatment technology (SMRT) and a surface mechanical rolling treatment technology (SMGT). The surface gradient micro-nano treatment is performed on special numerical control surface nano processing equipment, and the system comprises an SMRT/SMGT processing cutter and an oily lubrication cooling system.
Some embodiments are also disclosed in which the micro-nano machining apparatus includes an oil lubrication cooling system; the oily lubrication cooling system can provide oily cooling liquid; in the step (1), the oil lubrication cooling system can lubricate and cool the bearing steel in the process of carrying out surface gradient micro-nano treatment on the bearing steel.
Some embodiments are also disclosed herein, further comprising the steps of:
step (2): carrying out heat treatment on the bearing steel treated in the step (1) to relax the martensitic substructure interface on the nano-micron gradient structure, thereby forming a stable strengthening layer; the present application further stabilizes the strengthening layer and improves strength by heat treatment induced grain boundary relaxation.
Some embodiments are also disclosed herein, wherein the temperature of the heat treatment is 300-550 ℃; and/or the heat treatment time is 1-20h. The hardness can be further improved.
Some embodiments are also disclosed in which the gradient strengthening layer has a thickness of 150-1000 μm; and/or the microhardness peak of the gradient strengthening layer exceeds 9GPa; and/or the surface residual compressive stress of the gradient strengthening layer is greater than 500MPa; the microhardness peak referred to herein refers to the hardness maximum in the gradient reinforcement layer.
And/or, the bearing steel comprises M50 steel.
Some embodiments are also disclosed herein, further comprising, prior to step (1), the steps of:
and grinding the surface of the bearing steel. The grinding treatment can process the bearing steel workpiece to the required shape, remove the defects of larger shape on the surface and ensure the uniform treatment of the surface gradient micro-nano processing.
The specific method comprises the following steps: and (3) treating the surface of the M50 steel rotating member for the aviation bearing by adopting surface gradient micro-nano treatment. The surface gradient micro-nano processing system comprises a surface gradient micro-nano processing cutter and an oily lubrication cooling system, and can be embedded into a numerical control machine tool. The front end of the processing cutter is a hard ball (WC-Co hard alloy ball) with the diameter of 4-10mm. The machining tool bit is micro-nano-machined by using the surface gradient, and is pressed into the surface of M50 steel (pressing depth ap=20-100 mu M) rotating at high speed (excircle linear speed v1=50-800 mm/s), and at the same time, the machining tool bit is fed along the axial direction of the M50 steel (or the direction perpendicular to the rotation surface of the M50 steel) (speed v2=1×10) -3 -2×10 -1 mm/r). And lubricating and cooling the M50 steel treatment process for the aviation bearing by adopting oily cooling liquid so as to ensure the stability and uniformity of the treatment process. After the single pass machining is completed, n (1-8) passes are processed on the M50 steel rotary member according to a preset pressing depth ap x n in the same step. Menstruation meterAnd (3) carrying out heat treatment at 300-550 ℃ for 1-20h on the M50 steel rotating member subjected to the surface gradient micro-nano treatment, rearranging dislocation under the action of an internal stress force field and heat, refining nano lath martensite in the M50 steel into nano crystals, and further strengthening (figure 3) the interface relaxation of a martensite substructure on the surface of the treated workpiece, so as to obtain the gradient strengthening layer with good heat stability, strength and higher surface residual stress. Under the action of an internal stress force field and heat, dislocation rearranges, and the grain boundary strengthening effect of the subsurface layer of the M50 steel is further improved and more stable.
Compared with the existing method for improving the surface performance of M50 steel for aviation bearings, the method has the following advantages:
1. simple process and low cost, and can realize industrial production and processing. The SMRT/SMGT treatment process has no noise pollution, no dust and no chip in the processing process, and the method is environment-friendly. The surface gradient micro-nano machining system can be embedded into a numerical control machine tool, the processing mode of the process is similar to the turning process mode, and the surface gradient micro-nano machining tool is only required to be added with a surface gradient micro-nano machining program instruction and is provided with an oily lubrication cooling system. Therefore, the technology of the invention can realize industrial production and processing.
2. The surface quality of the M50 steel after the surface gradient micro-nano processing is good. The processing mode has a rolling effect on the surface of the workpiece, and good surface quality of the workpiece is ensured.
3. The thickness of the gradient reinforced layer obtained by the surface gradient micro-nano treatment and the heat treatment composite process treatment can reach 150-1000 mu m, and the reinforced layer has larger thickness and higher heat stability. The maximum shear stress of the aero-bearing is distributed 100-500 μm from the bearing surface. Therefore, an effective reinforcing layer is a key for guaranteeing the service life of the aviation bearing; moreover, the service temperature of the aviation bearing is high, and the aviation bearing is required to have high tissue stability. The reinforced layer obtained by the method has high depth and good thermal stability, and the service life of the aviation bearing can be effectively prolonged.
The embodiment of the invention provides a method for generating a stable gradient strengthening layer on the surface of M50 steel for an aeronautical bearing, which comprises the following specific implementation process flows:
(1) And (3) manufacturing the aviation bearing into a rotating member by using M50 steel, and grinding the surface of the rotating member. The grinding treatment can process the M50 workpiece to the required shape, remove the defects of larger shape on the surface and ensure the uniform treatment of the surface gradient micro-nano processing.
(2) And adopting surface gradient micro-nano processing to treat the surface of the rotary member made of M50 steel for the aviation bearing. The tool bit is selected and the rotating speed, the feeding rate and the pressing depth of the rotating member are based on the actual industrial requirements of the product; and the tool bit size selection is referenced to the actual machined work piece size. If a gradient residual stress layer is formed on the surface of the rotating member, in one embodiment, the SMRT tool bit is preferred, the rotational speed is between 300 and 800mm/s, and the feeding speed is v2=1×10 -3 -2×10 -1 mm/r, the pressing depth is 20-40 mu m, and 1-3 passes are processed; if the rotating member is used to form the gradient reinforcement layer with the highest surface hardness, in one embodiment, the SMGT cutter head is preferred, the rotation speed is between 50 and 400mm/s, and the feeding speed is v2=1×10 -3 -3×10 -2 The pressing depth is 20-50 mu m, and the processing is 1-3 passes. If the rotating member is used to form a gradient reinforced layer with higher peak hardness and deeper hardening, an SMRT cutter head can be adopted, the rotation linear speed is 50-800mm/s, and the feeding speed is v2=1×10 -3 -3×10 -2 The pressing depth is 20-50 mu m, and the processing is 3-8 passes.
(3) In the heat treatment process of the M50 steel for the aviation bearing, the heat treatment system is 300-550 ℃ for 1-20h. Preferably, the heat treatment temperature is 300-480 ℃ and the heat treatment time is 1-3 hours. The heat treatment can effectively prevent the M50 steel matrix from being excessively tempered and softened, thereby achieving the purpose of further forming a stable gradient strengthening layer.
Examples
Example 1:
the quenching and tempering M50 steel cylindrical test bar with the diameter of 10mm is treated by adopting the SMRT surface micro-nano processing system, and the main technical parameters are as follows:
the diameter of the SMRT machining tool bit is 6mm;
the linear speed v1=320 mm/s of the excircle rotation of the M50 steel test rod;
SMRT addingTool feed speed v2=2×10 -2 mm/r；
Processing pass n=3 times;
the single processing pass pressing depths are respectively as follows: ap (1) =40 μm, ap (2) =80 μm, ap (3) =120 μm.
Experiments show that the M50 steel for the aviation bearing is smooth in surface and high in smoothness after being subjected to SMRT treatment (figure 5). The residual compressive stress of the surface after SMRT treatment can reach-1003 MPa, and the residual stress of the matrix is close to 0, so that a gradient reinforcement layer with gradient residual stress is formed.
Example 2:
the quenching and tempering M50 steel cylindrical test bar with the diameter of 10mm is treated by adopting the SMGT surface micro-nano processing and heat treatment composite technology, and the main technical parameters are as follows:
the diameter of the SMGT processing tool bit is 8mm;
the linear speed v1=320 mm/s of the excircle rotation of the M50 steel test rod;
SMGT machining tool feed speed v2=1×10 -2 mm/r；
Processing pass n=2 times;
the single processing pass pressing depths are respectively as follows: ap (1) =40 μm, ap (2) =80 μm;
the heat treatment temperature is 400 ℃, and the heat preservation time is 2 hours.
After being treated by SMGT, the M50 steel for the aviation bearing has the highest surface hardness, the hardness value can reach 11GPa, and after being subjected to heat treatment, the surface hardness is further increased, and the hardness value can reach 11.4GPa.
Example 3:
the quenching and tempering state M50 steel cylindrical test bar with the diameter of 10mm is treated by adopting the SMRT surface micro-nano processing and heat treatment composite technology, and the main technical parameters are as follows:
the diameter of the SMRT machining tool bit is 6mm;
the linear speed v1=400 mm/s of the excircle rotation of the M50 steel test rod;
SMRT machining tool feed speed v2=2×10 -2 mm/r；
Processing pass n=4 times;
the single processing pass pressing depths are respectively as follows: ap (1) =40 μm, ap (2) =80 μm, ap (3) =120 μm, ap (4) =160 μm;
the heat treatment temperature is 300 ℃ and 400 ℃, and the heat preservation time is 2 hours.
The gradient strengthening layer of the M50 steel for the aviation bearing after being treated by the SMRT can reach 600 mu M; the M50 steel peak hardness further increased after heat treatment (fig. 7 and 8).
The rolling contact fatigue test was performed on M50 steel with a gradient strengthening layer, with a contact stress of 6.5GPa. Tests show that after the treatment by the method, the rolling contact fatigue life of the M50 steel for the aviation bearing with the gradient strengthening layer is remarkably improved (figure 9). Wherein, L of the M50 steel with the gradient strengthening layer 10 4 times the original sample, L 50 The lifting is about 3 times. The surface nano layer and higher residual compressive stress of the M50 steel with the gradient strengthening layer effectively inhibit the initiation of surface cracks, and further the capability of the M50 steel for resisting rolling contact fatigue is remarkably improved.
Example 4:
the quenching and tempering state M50 steel cylindrical test bar with the diameter of 4mm is treated by adopting the SMRT surface micro-nano processing and heat treatment composite technology, and the main technical parameters are as follows:
the diameter of the SMRT machining tool bit is 4mm;
the linear speed v1=800 mm/s of the excircle rotation of the M50 steel test bar;
SMRT machining tool feed speed v2=1×10 -3 mm/r；
Processing pass n=8 times;
the single processing pass pressing depths are respectively as follows: ap (1) =20 μm, ap (2) =40 μm, ap (3) =60 μm, ap (4) =80 μm, ap (5) =100 μm, ap (6) =120 μm, ap (7) =140 μm, ap (8) =160 μm;
the heat treatment temperature is 300 ℃, and the heat preservation time is 1h.
Forming a gradient strengthening layer on the surface of the M50 steel for the aviation bearing after SMRT treatment; the M50 steel peak hardness further increased after heat treatment.
Example 5:
the 130mm diameter quenched and tempered M50 steel cylindrical test bar is treated by adopting the SMGT surface micro-nano processing and heat treatment composite technology, and the main technical parameters are as follows:
the diameter of the SMGT processing tool bit is 10mm;
the linear speed v1=50mm/s of the excircle rotation of the M50 steel test bar;
SMRT machining tool feed speed v2=2×10 -1 mm/r；
Processing pass n=3 times;
the single processing pass pressing depths are respectively as follows: ap (1) =40 μm, ap (2) =80 μm, ap (3) =120 μm;
the heat treatment temperature is 300 ℃, and the heat preservation time is 1h.
The surface of the M50 steel for the aviation bearing is subjected to SMRT treatment to form a gradient strengthening layer.
Example 6:
the quenching and tempering state M50 steel cylindrical test bar with the diameter of 60mm is treated by adopting the SMRT surface micro-nano processing and heat treatment composite technology, and the main technical parameters are as follows:
the diameter of the SMRT machining tool bit is 8mm;
the linear speed v1=600 mm/s of the excircle rotation of the M50 steel test bar;
SMRT machining tool feed speed v2=2×10 -2 mm/r；
Processing pass n=2 times;
the single processing pass pressing depths are respectively as follows: ap (1) =100 μm, ap (2) =200 μm;
the heat treatment temperature is 300 ℃, and the heat preservation time is 1h.
The surface of the M50 steel for the aviation bearing is subjected to SMRT treatment to form a gradient strengthening layer.
Comparative example 1:
the preparation method is basically the same as that of example 1, except that the SMGT cutter head is adopted to process for the third time, the heat generation in the processing process is serious, and the surface of the sample is abraded.
Comparative example 2:
the preparation method is basically the same as that of example 2, except that after the SMRT tool bit is adopted, the hardness of the surface of the sample before and after the sample is processed is 8GPa, and no obvious change exists.
Comparative example 3:
the preparation process was essentially the same as in example 3, except that the indentation depth exceeded 400 μm (50 μm x 8). The sample processing process generates severe heat and the surface is worn.
Comparative example 4:
the preparation process was substantially the same as in example 3, except that heat treatment at 550℃was carried out for 20 hours. The sample matrix is obviously softened from 8GPa to 7.5 GPa.
The embodiment of the application also discloses bearing steel, which is obtained after the bearing steel is treated by the surface strengthening method of the bearing steel.
It will be readily appreciated by those skilled in the art that the above advantageous ways can be freely combined and superimposed without conflict.
The foregoing description of the preferred embodiment of the present invention is not intended to limit the invention to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. The foregoing is merely a preferred embodiment of the present application and it should be noted that it will be apparent to those skilled in the art that several modifications and variations can be made without departing from the technical principles of the present application, and these modifications and variations should also be regarded as the scope of the present application.
Claims (10)
1. A method for surface strengthening of bearing steel, comprising the steps of:
step (1): carrying out surface gradient micro-nano treatment on the bearing steel to form a nano-micro gradient structure on the surface of the bearing steel; the nano-micron gradient structure forms a gradient strengthening layer on the surface of the bearing steel.
2. The method for strengthening the surface of a bearing steel according to claim 1, wherein in the step (1), the apparatus for performing the surface gradient micro-nano treatment on the bearing steel is a micro-nano treatment apparatus; the micro-nano processing equipment comprises a processing cutter; the processing cutter can roll or crush the surface of the bearing steel, so that the surface of the bearing steel is subjected to plastic deformation to obtain the nano-micron gradient structure.
3. The method for surface strengthening bearing steel according to claim 2, wherein the surface gradient micro-nano treatment of the bearing steel comprises the steps of:
first-pass treatment: the cutter head of the machining cutter is pressed into the surface of the rotating bearing steel for the first time, and meanwhile, the cutter head of the machining cutter is fed along the axial direction of the bearing steel or the direction perpendicular to the rotating surface of the bearing steel;
further, according to the surface area of the bearing steel and the machining efficiency of the machining tool, the outer circular linear velocity v1 and the feeding velocity v2 of the bearing steel rotation are controlled.
4. A method of surface strengthening bearing steel as recited in claim 3, wherein the surface gradient micro-nano treatment of the bearing steel further comprises the steps of:
treatment of the n-th pass: pressing the tool bit of the machining tool into the surface of the rotating bearing steel for the nth time, and simultaneously feeding the tool bit of the machining tool along the axial direction of the bearing steel or the direction perpendicular to the rotation surface of the bearing steel; wherein n=1-8;
further, during the nth pass treatment, the outer circular linear velocity v1=50-800 mm/s of the bearing steel rotation; the press depth of the nth press-in is a p * n; the speed of the feed v2=1×10 -3 -2×10 -1 mm/r；
And/or controlling the pressing depth and the pressing pass of the first pressing according to the surface strengthening requirement of the bearing steel and the principle of no damage to the processing surface; and/or controlling the press-in depth a of the first press-in according to the surface strengthening requirement of the bearing steel and the principle of no damage to the machined surface p And press-in pass n.
5. A method of surface strengthening bearing steel according to claim 2, wherein the micro-nano machining device comprises a surface mechanical rolling treatment device comprising rolling balls capable of free rolling, the rolling balls forming the machining tool; further, the rolling balls are made of WC-Co hard alloy; and/or the diameter of the rolling ball is 4-10mm;
or, the micro-nano processing equipment comprises surface mechanical rolling processing equipment, wherein the surface mechanical rolling processing technical equipment comprises fixed balls, and the fixed balls form the processing cutter; further, the fixing ball is made of WC-Co hard alloy; and/or the diameter of the fixed ball is 4-10mm.
6. The method for strengthening the surface of bearing steel according to claim 2, wherein the micro-nano machining equipment comprises an oil-based lubrication cooling system; the oily lubrication cooling system can provide oily cooling liquid; in the step (1), the oily lubrication cooling system can lubricate and cool the bearing steel in the process of carrying out surface gradient micro-nano treatment on the bearing steel.
7. The method for surface strengthening of bearing steel according to claim 1, further comprising the step of:
step (2): performing heat treatment on the bearing steel treated in the step (1) to relax a martensite substructure interface on the nano-micron gradient structure, thereby forming a high-temperature stable reinforcement layer;
further, the temperature of the heat treatment is 300-550 ℃; and/or the heat treatment is carried out for 1-20h.
8. The method for surface strengthening of bearing steel according to claim 1, wherein the gradient strengthening layer has a thickness of 150-1000 μm; and/or, the microhardness peak of the gradient strengthening layer exceeds 9GPa; and/or the surface residual compressive stress of the gradient strengthening layer is greater than 500MPa;
and/or, the bearing steel comprises M50 steel.
9. The method for surface strengthening of bearing steel according to claim 1, further comprising, before said step (1), the steps of:
and grinding the surface of the bearing steel.
10. Bearing steel, characterized in that it is obtained after treatment by the method for surface strengthening of a bearing steel according to any one of claims 1-9.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202211538324.1A CN116200581A (en) | 2022-12-02 | 2022-12-02 | Surface strengthening method for bearing steel and bearing steel |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202211538324.1A CN116200581A (en) | 2022-12-02 | 2022-12-02 | Surface strengthening method for bearing steel and bearing steel |
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- 2022-12-02 CN CN202211538324.1A patent/CN116200581A/en active Pending
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