Preparation method of bimetallic material and sliding bearing

Abstract

The invention relates to the field of manufacturing of special materials for wind power, in particular to a preparation method of a bimetallic material and a sliding bearing. The preparation method specifically comprises the following steps that a steel base body is pretreated to improve the roughness; gas flow and copper alloy powder are utilized to form gas-solid two-phase flow and impact the steel base plate to form the alloy layer, so that in the deposition forming process of the alloy layer, the lead phase does not reach the melting temperature all the time, and the low porosity is kept between the alloy layers, so that the possibility of the lead emitting phenomenon during sintering is reduced; sintering the alloy layer and the steel substrate; and rolling the alloy layer and the steel substrate.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of special materials for wind power, in particular to a preparation method of bimetallic material and sliding bearing. BACKGROUND

[0002] In the field of wind power, large rolling bearings are replaced by sliding bearings. Steel-copper bimetallic material is often used in sliding bearings, so that the sliding bearing has excellent load capacity of steel matrix and self-lubricating properties of copper alloy. The traditional preparation method of steel-copper bimetallic material is two-stage sintering and rolling. The first stage of sintering and rolling, i.e. one sintering and one rolling, makes the steel plate and copper powder combined. The second stage of sintering and rolling, i.e. two sintering and two rolling, makes the metallurgical bonding degree and mechanical properties of the copper layer improved.

[0003] Generally, after one sintering, the copper layer has a high porosity. During one rolling, the copper layer pores cannot be completely closed. In order to ensure the sufficient combination between powder particles during two sintering, a high temperature needs to be maintained, which makes the air in the copper layer pores expand when heated, so that the lead phase in the copper layer flows in liquid state and flows out of the surface of the material, i.e. lead out phenomenon. At the same time, the lead phase will also concentrate and separate in the copper layer pores, i.e. segregation phenomenon, which affects the mechanical properties of the material. SUMMARY

[0004] The present application provides a preparation method of bimetallic material and sliding bearing, which can reduce the possibility of lead out phenomenon and segregation phenomenon while maintaining a high temperature during two sintering.

[0005] The preparation method of bimetallic material provided by the present application adopts the following technical scheme.

[0006] The preparation method of bimetallic material specifically includes the following steps.

[0007] S1, pretreating the steel matrix to improve the roughness;

[0008] S2, forming gas-solid two-phase flow by using gas flow and copper alloy powder and impacting the steel base plate to form an alloy layer;

[0009] S3, sintering the alloy layer and the steel base plate;

[0010] S4, rolling the alloy layer and the steel base plate;

[0011] The temperature of the gas flow is 490-510℃, and the gas pressure is 3.0-3.5MPa.

[0012] By adopting the technical scheme, the gas-solid two-phase flow impacts the steel base plate to make the copper alloy powder undergo severe plastic deformation, so as to realize deposition of the alloy layer with extremely low porosity and fine grains, reduce the possibility of lead spitting or element segregation in the subsequent sintering process, and help to further improve the sintering temperature, enhance the metallurgical bonding degree in the alloy layer, and in addition, the gas-solid two-phase flow impacts the surface of the steel base plate and forms a mechanical interlocking structure with the rough steel base plate. The final bimetallic material has excellent characteristics of lead distribution dispersion, high bonding strength and high hardness of the alloy layer.

[0013] Optionally, the copper alloy powder in S2 includes, in percentage by mass, tin 9-11%, lead 8-15%, and the rest is copper.

[0014] By adopting the technical scheme, tin is too low in strength, tin is too high in toughness and is prone to brittleness, lead is too low in friction coefficient and is too large, and lead is too high in volume of liquid phase and is prone to grain boundary penetration, that is, lead spitting.

[0015] Optionally, before S2, the copper alloy powder is subjected to reduction treatment in a reducing atmosphere, and the copper alloy powder is spread to a thickness of less than 5 mm.

[0016] By adopting the technical scheme, the oxide film on the surface of the copper alloy powder is removed as much as possible, so that the metal powder particles can directly contact each other, and most of the energy of the airflow impact is used for the combination of the metal powder particles rather than the breaking of the oxide film, which helps to improve the deposition efficiency and tightness of the alloy layer and reduce the porosity in the alloy layer.

[0017] Optionally, the reduction treatment includes the following steps.

[0018] S21, temperature is raised to 255-265℃ at a rate of 4-6℃ / min, and then kept for 45 min;

[0019] S22, temperature is raised to 380-420℃ at a rate of 2-3℃ / min based on the temperature of the first stage, and kept for 60-90 min.

[0020] By adopting the technical scheme, S21 reduces the tin oxide first to generate corresponding water vapor, which is then discharged, and then S22 is performed to reduce the cuprous oxide, and part of the water vapor is discharged, so that too much water vapor is not generated in the reduction process, the partial pressure of the water vapor is not too large, the possibility of secondary oxidation of the water vapor and the cuprous oxide to be reduced and the tin oxide to generate high-order oxides is reduced, and the porosity in the alloy layer is reduced and the strength is improved.

[0021] Optionally, the reducing atmosphere includes 55-65% of hydrogen and 35-45% of nitrogen.

[0022] By adopting the technical scheme, the copper alloy powder is fully reduced without being prone to explosion.

[0023] Optionally, the multi-stage stress relief annealing is performed after the sintering of the S3 is completed and before the rolling of the S4.

[0024] By adopting the technical scheme, the alloy layer is not prone to cracks.

[0025] Optionally, the multi-stage stress relief annealing comprises the following steps.

[0026] S31, cooling the alloy layer and the steel substrate to 640-660 DEG C at 1-2 DEG C / min, holding for 25-35 min, then cooling to 200 DEG C or below with the furnace and discharging;

[0027] S32, holding the alloy layer and the steel substrate in a protective atmosphere at 240-260 DEG C for 90-100 min before rolling;

[0028] S33, holding the alloy layer and the steel substrate at 275-285 DEG C for 120-130 min after rolling, and then cooling to 100 DEG C or below at 0.5-1 DEG C / min.

[0029] By adopting the technical scheme, the residual stress in the alloy layer is reduced in S31, and the formation of micro-cracks is reduced; the plasticity of the alloy layer and the steel substrate is improved in S32, so that the rolling force is reduced during rolling, and the outer surface of the alloy layer and the steel substrate is smooth, and is not prone to uneven surface; the final residual stress of the alloy layer after rolling is reduced in S33, the fatigue life of the alloy layer is improved, and the interlayer cracking between the alloy layer and the steel substrate is not prone to occur.

[0030] Optionally, the pretreatment of the S1 comprises: first, wiping off the oil stains on the surface of the steel substrate with a solvent; then, placing the steel substrate in anhydrous ethanol for ultrasonic treatment for 2 min; and then, drying for 5 min to perform sand blasting; and then, performing the S2 within 2 h after the sand blasting is completed.

[0031] By adopting the technical scheme, mechanical interlocking is formed between the alloy layer and the steel substrate, and the interlayer bonding force is improved.

[0032] Optionally, the heating rate of the sintering in the S3 is 20 DEG C / min, until 850-900 DEG C and holding for 20 min, and then cooling with the furnace.

[0033] The application also provides a sliding bearing adopting the following technical scheme.

[0034] A sliding bearing is manufactured by using the bimetallic material obtained by the preparation method of the bimetallic material.

[0035] By adopting the technical scheme, a high-quality sliding bearing with high interlayer bonding strength and high hardness of the alloy layer is obtained, and is more suitable for use in the wind power field.

[0036] To sum up, the present application at least includes the following beneficial effects.

[0037] The gas-solid two-phase flow impacts the steel base plate to cause severe plastic deformation of the copper alloy powder, so as to realize deposition of the alloy layer with extremely low porosity and fine grains, reduce the possibility of lead spitting or element segregation in the subsequent sintering process, and help to further improve the sintering temperature, enhance the metallurgical bonding degree in the alloy layer, so that the final bimetallic material has excellent characteristics of dispersed lead distribution, high bonding strength and high hardness of the alloy layer. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 is a flowchart of the main steps of the present application;

[0039] Figure 2 The metallographic photograph of Example Two is on the left side, and the metallographic photograph of Comparative Example One is on the right side;

[0040] Figure 3 The metallographic photograph of Example Two is on the left side, and the metallographic photograph of Comparative Example One is on the right side; Figure 2 The enlarged view of the interlayer bonding position in the metallographic photograph on the left side is Figure 2 The enlarged view of the interlayer bonding position in the metallographic photograph on the right side is;

[0041] Figure 4 is a metallographic photograph of Example Two showing uniformity of element distribution, wherein the upper right view shows copper element distribution, the lower left view shows lead element distribution, and the lower right view shows tin element distribution;

[0042] Figure 5 is a metallographic photograph of Comparative Example One showing uniformity of element distribution, wherein the upper right view shows copper element distribution, the lower left view shows lead element distribution, and the lower right view shows tin element distribution. DETAILED DESCRIPTION

[0043] The present application will be further described in detail below in combination with the drawings.

[0044] The present application discloses a preparation method of a bimetallic material, referring to Figure 1 , specifically including the following steps.

[0045] S1, pretreating the steel base body to improve roughness.

[0046] The pretreatment can be specifically that first, the oil stains on the surface of the steel base body are wiped off using a solvent, which can be a hydrocarbon-based cleaning agent, then the steel base body is placed in anhydrous ethanol for ultrasonic treatment for 2 min, and then dried for 5 min for sand blasting, 100 mm 2The area sandblasting time is 15-20s. After sandblasting, the surface residual sand is removed by air gun, and S2 is performed within 2h after sandblasting. During the pretreatment process, the surface temperature of the steel substrate is maintained at 15-35℃, and the relative humidity is below 70%.

[0047] S2, forming a gas-solid two-phase flow by using airflow and copper alloy powder and impacting the steel substrate to form an alloy layer.

[0048] The airflow is divided into two streams, a carrier airflow and an acceleration airflow, the carrier airflow is used to mix the copper alloy powder to form a gas-solid two-phase flow, and the gas-solid two-phase flow and the acceleration airflow meet and impact the steel substrate. The pressure and temperature of the two streams are close to each other, both are 3.0-3.5Mpa and 490-510℃.

[0049] In addition, the copper alloy powder includes tin 9-11%, lead 8-15%, and the rest is copper by mass percentage, which can be prepared by vacuum air atomization method. Before use, the copper alloy powder is first subjected to reduction treatment in a reducing atmosphere, which can be 55-65% hydrogen and 35-45% nitrogen. And during the reduction process, the copper alloy powder is spread to a thickness of less than 5mm, and the powder is turned over every 20min. The reduction treatment includes the following steps.

[0050] S21, heating at 4-6℃ / min to 255-265℃, and then holding for 45min.

[0051] S22, on the basis of the temperature of the first stage, heating at 2-3℃ / min to 380-420℃, and holding for 60-90min.

[0052] S3, sintering the alloy layer and the steel substrate, the sintering heating rate is 20℃ / min, until 850-900℃ and holding for 20min, and then cooling with the furnace.

[0053] S4, rolling the alloy layer and the steel substrate, the rolling amount is 20% of the total thickness of the alloy layer and the steel substrate.

[0054] After S3 sintering holding ends and before S4 rolling, multi-stage stress relief annealing is performed, which includes the following steps.

[0055] S31, cooling the alloy layer and the steel substrate to 640-660℃ at 1-2℃ / min, holding for 25-35min, and then cooling with the furnace to below 200℃ and discharging.

[0056] S32, before rolling, the alloy layer and the steel substrate are held in a protective atmosphere at 240-260℃ for 90-100min.

[0057] S33, after rolling, the alloy layer and the steel substrate are kept at 275-285℃ for 120-130min, and then cooled to below 100℃ at 0.5-1℃ / min.

[0058] The following is described in detail in connection with specific examples and comparative examples.

[0059] Example One:

[0060] A method for preparing a bimetallic material, specifically comprising the following steps.

[0061] S1, pretreating the steel substrate to improve roughness.

[0062] The pretreatment can specifically be that the oil stains on the surface of the steel substrate are first removed using a solvent, which can be a hydrocarbon-based cleaning agent, then the steel substrate is placed in anhydrous ethanol for 2min of ultrasonic treatment, and then dried for 5min for sandblasting, with a sandblasting time of 17s per 100mm 2 of the area. The surface residual sand is immediately removed using an air gun after sandblasting, and S2 is performed within 2h after the end of sandblasting. During the pretreatment process, the surface temperature of the steel substrate is maintained at 25℃, and the relative humidity is below 70%.

[0063] S2, forming a gas-solid two-phase flow using airflow and copper alloy powder and impacting the steel substrate to form an alloy layer.

[0064] The airflow is divided into two streams, a carrier airflow and an acceleration airflow, the carrier airflow is used to mix the copper alloy powder to form a gas-solid two-phase flow, and the gas-solid two-phase flow and the acceleration airflow meet and impact the steel substrate. The pressure and temperature of the two streams are close to each other, both being 3.0Mpa and 490℃.

[0065] In addition, the copper alloy powder, by mass percentage, includes 9% tin, 8% lead, and the remainder copper, and can be prepared by a vacuum gas atomization method. Before use, the copper alloy powder is first subjected to reduction treatment in a reducing atmosphere, which can be 55% hydrogen and 45% nitrogen. And during the reduction process, the copper alloy powder is spread to a thickness of less than 5mm, and the powder is turned over every 20min. The reduction treatment includes the following steps.

[0066] S21, increase the temperature to 255℃ at 4℃ / min, and then keep it for 45min.

[0067] S22, on the basis of the temperature of the first stage, increase the temperature to 380℃ at 2℃ / min, and keep it for 60min.

[0068] S3, sintering the alloy layer and the steel substrate, with a sintering temperature increasing rate of 20℃ / min, until 850℃ and keeping it for 20min, and then cooling with the furnace.

[0069] S4, rolling the alloy layer and the steel substrate, the rolling amount being 20% of the total thickness of the alloy layer and the steel substrate.

[0070] S3, after the sintering and holding, and before and after the rolling, a multi-stage stress relief annealing is performed, including the following steps.

[0071] S31, cooling the alloy layer and the steel substrate to 640℃ at a rate of 1℃ / min, holding for 25min, then furnace cooling to below 200℃ and discharging.

[0072] S32, before the rolling, holding the alloy layer and the steel substrate in a protective atmosphere at 240℃ for 90min.

[0073] S33, after the rolling, holding the alloy layer and the steel substrate at 275℃ for 120min, then cooling to below 100℃ at a rate of 0.5℃ / min.

[0074] Example Two:

[0075] The difference between Example One and Example Two is that:

[0076] In the pre-treatment process of S1, the sandblasting time per 100mm 2 of the area is 20s, and the surface temperature of the steel substrate is maintained at 35℃.

[0077] In S2, the pressure and temperature of the two gas streams are 3.5Mpa and 510℃. The copper alloy powder includes, by mass percentage, tin 11%, lead 15%, and the rest copper. The reducing atmosphere can be 65% hydrogen and 35% nitrogen.

[0078] The reduction treatment includes the following steps.

[0079] S21, heating to 265℃ at a rate of 6℃ / min, then holding for 45min.

[0080] S22, on the basis of the temperature of the first stage, heating to 420℃ at a rate of 3℃ / min, holding for 90min.

[0081] S3, sintering the alloy layer and the steel substrate, the sintering heating rate being 20℃ / min, up to 900℃ and holding for 20min, then furnace cooling.

[0082] The multi-stage stress relief annealing includes the following steps.

[0083] S31, cooling the alloy layer and the steel substrate to 660℃ at a rate of 2℃ / min, holding for 35min, then furnace cooling to below 200℃ and discharging.

[0084] S32, before the rolling, holding the alloy layer and the steel substrate in a protective atmosphere at 260℃ for 100min.

[0085] S33, after rolling, the alloy layer and the steel substrate are kept at 285°C for 130 min, and then cooled to below 100°C at 1°C / min.

[0086] Comparative Example 1:

[0087] The difference from Example 2 is that:

[0088] S2, the steel substrate is placed in a tray, the copper alloy powder is placed on the surface of the steel substrate and leveled with a spatula, and then molded at a pressure of 80 MPa to form a composite blank.

[0089] S3, the composite blank is heated to 820°C at 15°C / min and kept for 25 min, and then cooled to below 200°C with the furnace to obtain a green sheet.

[0090] S4, the green sheet is rolled by 18%.

[0091] S5, the alloy layer and the steel substrate are sintered.

[0092] S6, the alloy layer and the steel substrate are rolled.

[0093] Comparative Example 2:

[0094] The difference from Example 2 is that:

[0095] During the reduction process, the copper alloy powder is heated to 420°C at 3°C / min, and kept for 135 min.

[0096] Comparative Example 3:

[0097] The difference from Example 2 is that the multi-stage stress relief annealing is not performed.

[0098] Comparative Example 4:

[0099] The difference from Example 2 is that the multi-stage stress relief annealing does not perform S31.

[0100] Comparative Example 5:

[0101] The difference from Example 2 is that the multi-stage stress relief annealing does not perform S32.

[0102] Comparative Example 6:

[0103] The difference from Example 2 is that the multi-stage stress relief annealing does not perform S33.

[0104] The following tests the following indicators of the bimetallic material prepared in each example and comparative example.

[0105] Interlayer bonding strength, take 20mm x 10mm standard sample of each bimetallic material, use high-strength adhesive to stick the steel substrate and the alloy layer one by one on two tensile clamps, and perform tensile test on the universal material testing machine until the alloy layer and the steel substrate connection separate to obtain the maximum failure load, and combine the bonding area of the sample to calculate the interlayer bonding strength.

[0106] Alloy layer hardness, obtained via Vickers hardness test.

[0107] Porosity, according to the metallographic image of the alloy layer of each sample and combined with image analysis software, the proportion of white and black area to the total area is calculated to obtain the porosity.

[0108] Lead distribution uniformity, qualitatively evaluate the distribution of white points or areas on the metallographic image of the alloy layer of each sample. The more uniform the lead phase distribution, the more dispersed the white area.

[0109] Bending performance, perform three-point bending test on long strip-shaped samples of the same size specification, observe the alloy layer cracking and separation between the alloy layer and the steel substrate under bending to 90° and record.

[0110] The following table is the specific experimental results.

[0111] Table 1:

[0112]

[0113] In combination with Examples 1-2 and Comparative Example 1, Figure 2 and Figure 3 It can be seen that the application uses gas-solid two-phase flow to impact the steel substrate, which can realize lower porosity in the alloy layer compared to traditional one-burn and one-rolling, and form fine and directional pits on the surface of the steel substrate, so that mechanical interlocking between the alloy layer and the steel substrate is realized, and the interlayer bonding force is higher. In combination with Figure 4 and Figure 5 It can be seen that the lead distribution uniformity of the bimetallic material of the application is better.

[0114] In combination with Examples 1-2 and Comparative Example 2, it can be seen that the reduction treatment of the copper alloy powder according to the application before use can better reduce the porosity of the alloy layer. The metallographic image of Comparative Example 2 is similar to that of Comparative Example 1, only the segregation degree of lead phase is lower, so it is not shown.

[0115] In combination with Examples 1-2 and Comparative Examples 3-6, it can be seen that multi-stage stress annealing can effectively improve the plasticity of the alloy layer, so that the bimetallic material is more difficult to crack during bending, and the interlayer bonding force is higher, and S31 and S33 mainly contribute to the improvement of the plasticity of the alloy layer.

[0116] This application also discloses a sliding bearing, which is manufactured using the bimetallic material obtained by the above-described method for preparing a bimetallic material.

[0117] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A method for preparing a bimetallic material, characterized in that: Specifically, the following steps are included: S1. Pre-treat the steel substrate to improve its roughness; S2. Gas-solid two-phase flow is formed by airflow and copper alloy powder and impacts the steel substrate to form an alloy layer; S3. Sinter the alloy layer and the steel substrate; S4. Roll the alloy layer and the steel substrate; The gas flow temperature is 490-510℃, and the gas pressure is 3.0-3.5MPa.

2. The method for preparing a bimetallic material according to claim 1, characterized in that: The copper alloy powder in S2, by mass percentage, includes 9-11% tin, 8-15% lead, and the remainder is copper.

3. The method for preparing a bimetallic material according to claim 1, characterized in that: Before performing S2, the copper alloy powder is first reduced in a reducing atmosphere until the copper alloy powder is spread out to a thickness of less than 5 mm.

4. The method for preparing a bimetallic material according to claim 3, characterized in that: The restoration process includes the following steps: S21. Increase the temperature to 255-265℃ at a rate of 4-6℃ / min, and then hold for 45min. S22. Based on the temperature of the first stage, increase the temperature to 380-420℃ at a rate of 2-3℃ / min and hold for 60-90min.

5. The method for preparing a bimetallic material according to claim 3, characterized in that: The reducing atmosphere comprises 55-65% hydrogen and 35-45% nitrogen.

6. The method for preparing a bimetallic material according to claim 1, characterized in that: After the S3 sintering and heat preservation is completed and during the S4 rolling process, multi-stage stress-relief annealing is carried out.

7. The method for preparing a bimetallic material according to claim 6, characterized in that: The multi-stage stress-relief annealing specifically includes the following steps: S31. Cool the alloy layer and steel substrate to 640-660℃ at 1-2℃ / min, hold for 25-35min, then cool with the furnace to below 200℃ and remove from the furnace. S32. Before rolling, the alloy layer and the steel substrate are kept in a protective atmosphere at 240-260℃ for 90-100 minutes. S33. After rolling, the alloy layer and the steel substrate are held at 275-285℃ for 120-130 min, and then cooled to below 100℃ at 0.5-1℃ / min.

8. The method for preparing a bimetallic material according to claim 7, characterized in that: The pretreatment of S1 includes first wiping the oil stains on the surface of the steel substrate with a solvent, then immersing the steel substrate in anhydrous ethanol for 2 minutes of ultrasonic treatment, then drying for 5 minutes and then sandblasting, and then performing S2 within 2 hours after the sandblasting is completed.

9. The method for preparing a bimetallic material according to claim 1, characterized in that: The sintering temperature rise rate in S3 is 20℃ / min, up to 850-900℃ and held for 20min, and then cooled with the furnace.

10. A sliding bearing, characterized in that: The bimetallic material is manufactured using the preparation method of a bimetallic material according to any one of claims 1-9.

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