A production process for stainless steel with a textured surface for gearbox friction plates

Abstract

The present invention relates to a production process for the textured surface of stainless steel strips for gearbox friction plates. The process uses 430 stainless steel as raw material and is carried out through the following steps: initial rolling with a large reduction rate for forming, first bright annealing to remove internal stress, texture rolling with a small reduction rate for fine-tuning the strip and texture the strip surface, second bright annealing to refine the grains and improve toughness, and strip cutting for storage. Through the two-rolling and two-annealing production process, the recrystallized grain size is increased, internal stress is removed, the toughness of the stainless steel strip is improved, and the service life and ride smoothness of the hybrid gearbox friction plates are improved. Through long-term production, data is summarized to obtain a functional relationship between the surface roughness of the initial rolling work rolls and the total number of rolling passes and the total reduction rate, and the selection of the surface roughness of the rolls for each pass is quantified. The textured rolls of the last pass of the textured rolling are ground by a texture machine to ensure that the roughness of the textured surface of the last pass is uniform, thereby improving the stability of the product and ensuring that the surface parameters of the final friction plate product are stable within the expected range.

Description

Technical Field

[0001] The present invention belongs to the technical field of production methods of precision stainless steel strips, and relates to a production process for a textured surface of a stainless steel strip for a gearbox friction plate, and in particular to a production process for a textured surface of a stainless steel strip for a hybrid gearbox friction plate. Background Art

[0002] During vehicle operation, gear shifting is necessary to adapt to different road conditions. This not only saves fuel but also protects the engine from overload. Currently, vehicles primarily have manual and automatic transmissions. The transmission achieves this by engaging and disengaging the friction plate and the mating plate. A typical vehicle's lifespan is 300,000 to 500,000 kilometers, and shifting gears is inevitable during this process. The durability of the friction plate affects the clutch's service life, and factors influencing the life of the friction plate include the friction material, lubricant performance, and operating conditions. Therefore, friction plates require high material adhesion, good wear resistance, toughness, and impact resistance.

[0003] 430 stainless steel offers excellent corrosion resistance, low thermal expansion coefficient, thermal fatigue resistance, high strength, good impact resistance, and excellent toughness after rolling and deformation, resulting from a modulated annealing treatment to increase recrystallized grain size. This low cost makes it suitable for hybrid transmission friction linings. These friction linings not only possess these characteristics but also require a high surface roughness, which requires a texturing treatment.

[0004] A search revealed that the invention patent, publication number CN113118218A, discloses a method for producing a sandblasted, textured surface on an ultra-hard, precision stainless steel strip for shrapnel. The method involves rolling the raw material, bright solution annealing, modulated rolling, degreasing and cleaning, tension straightening, and longitudinal shearing. The primary textured surface step is modulated rolling, which involves using a sandblasted textured roller and performing 5 to 6 textured rolling cycles to produce a stainless steel strip with a sandblasted textured surface. During the modulated rolling process, the sandblasted surface is evenly sprayed onto the roller, and then rolled 5 to 6 times. This makes it difficult to maintain uniform sandblasting on the roller surface, resulting in inconsistent surface quality and product performance errors. Furthermore, after rolling the raw material, solution annealing is performed, followed by modulated rolling. The resulting grains are flattened, resulting in high deformation storage energy and internal stress in the material, which cannot meet the production requirements for transmission friction plates.

[0005] Patent publication number CN101537425A discloses a cold rolling process for frosted stainless steel sheet. The process involves rolling the sheet to a final roll roughness of Ra 0.3-0.4, followed by recrystallization and softening annealing in a bright annealing furnace. Finally, the sheet passes through a leveling mill with Ra 0.4-0.5 leveling rollers to eliminate the yield plateau and produce a textured 430 stainless steel strip. This textured surface not only meets the surface roughness requirements of transmission friction plates, but also requires a leveler to achieve a high level of texture without a high reduction ratio, making it difficult to maintain a high level of texture.

[0006] In summary, reasonable rolling and post-processing processes are needed to solve the production problem of hybrid transmission friction plates. Summary of the Invention

[0007] In view of this, the present invention provides a production process for the textured surface of stainless steel strips for gearbox friction plates in order to solve the problem that the textured degree of the stainless steel plate prepared by the above-mentioned process method is difficult to ensure and cannot meet the production requirements of gearbox friction plates. The process uses low-cost 430 stainless steel as raw material and adopts a two-rolling and two-recessing production process to improve the strength and toughness of the product; by summarizing the functional relationship between the initial rolling pass and the surface roughness of the roller, the roughness of the roller in each pass of the initial rolling is accurately controlled to ensure the accuracy of the subsequent textured rolling step; by textured high-strength roller surface and then performing texture rolling, the roughness of the textured surface is ensured to be uniform.

[0008] In order to achieve the above object, the present invention provides the following technical solutions:

[0009] A production process for a stainless steel strip with a textured surface for a gearbox friction plate comprises the following steps:

[0010] S1. Raw material selection: Use Shanxi Taiyuan Iron and Steel 430 stainless steel with a thickness of 3.0mm to 5.0mm and a width of 1250mm;

[0011] S2. Preliminary rolling: The selected 430 stainless steel raw material is rolled through N passes with a total reduction rate of 35% to 60%. The reduction rate of the first N-1 passes is between 5% and 18%, and the reduction rate of the Nth pass does not exceed 10%. Ordinary rolls are used for all N rolling passes. In the preliminary rolling process, the work rolls need to be replaced after each rolling pass. The relationship between the surface roughness of the work rolls in the preliminary rolling process and the total reduction rate as a function of the number of rolling passes is:

[0012] z1=INT(-0.11875x+3.25y)

[0013] z x =z x-1 -0.1

[0014] z1 is the target roughness value of the working roll in the initial rolling process, x is the total number of rolling passes in the initial rolling process, x=2~8, y is the total reduction rate, z x is the target roughness value of the working roll in the xth pass, z x-1 is the target roughness value of the working roll in the x-1th pass;

[0015] S3, first bright annealing: the semi-finished stainless steel strip preliminarily rolled in step S2 is cleaned to remove surface oil stains and then bright annealed;

[0016] S4, texture rolling: The steel strip after the first bright annealing in step S3 is rolled for M passes, with a total reduction rate not exceeding 25% and a single pass reduction rate not exceeding 17%. The first M-1 passes are all rolled using ordinary rollers, and the Mth pass is rolled using textured rollers. The final product thickness is 1.8 mm.

[0017] S5, second bright annealing: the stainless steel strip rolled in step S4 is cleaned to remove surface oil stains and bright annealed again;

[0018] S6. Cutting into strips and storing: The stainless steel strips after the second bright annealing in step S5 are cut into strips, packaged and stored according to customer requirements.

[0019] Furthermore, the number of preliminary rolling passes in step S2 is N=4-8.

[0020] Furthermore, the first bright annealing in step S3 and the second bright annealing in step S5 are both performed using a horizontal bright annealing furnace; the annealing temperature is set at 860° C. to 900° C., the annealing furnace TV value is 3.0 m / min, the hydrogen concentration is 99.99%, and the annealing tension is 10 to 25 MPa.

[0021] Furthermore, the value M in the roughening rolling in step S4 is 2 to 3.

[0022] Furthermore, in step S4, the surface roughness parameters of the working roll during the final pass of the texturing rolling are: Ra=2.5±0.2, RPc=30±20, and Rsk=0.0±0.4.

[0023] Furthermore, after the texturing rolling in step S4 is completed, the surface roughness parameters of the final stainless steel strip are: Ra=0.9-2.6, RPc=20-55, and Rsk=-0.4-0.7.

[0024] The beneficial effects of the present invention are:

[0025] 1. The disclosed process for producing a textured surface of stainless steel strip for transmission friction linings uses low-cost 430 stainless steel as raw material. The strip undergoes initial rolling with a large reduction rate followed by bright solution annealing to remove internal stress and increase the recrystallized grain size. A surface texturing treatment with a small reduction rate is then performed followed by a secondary bright solution annealing to remove internal stress and increase the toughness of the stainless steel strip. The result is a 430 stainless steel strip for transmission friction linings that is high in strength, good in toughness, and long in service life, further improving the service life and ride smoothness of hybrid transmission friction linings.

[0026] 2. The present invention discloses a production process for textured stainless steel strips for gearbox friction plates. Through long-term production research, the functional relationship between the surface roughness of the rollers and the number of passes in the initial rolling process is summarized, the surface roughness of the rollers in each pass is quantified, and the surface roughness of the working rollers in each pass of the initial rolling is precisely controlled to ensure the accuracy of the subsequent textured rolling process.

[0027] 3. The present invention discloses a production process for the textured surface of a stainless steel strip for a gearbox friction plate. In the last pass of the texture rolling, a high-strength M42 high-speed steel texture roller is used to texture the surface of the stainless steel strip to ensure uniform roughness of the textured surface and thus guarantee product quality.

[0028] 4. The disclosed process for producing a textured surface of a stainless steel strip for a gearbox friction plate ensures that the surface parameters of the final friction plate product are stable within the expected range by combining the above-mentioned texture roller surface parameters with the two-rolling and two-retracting process of the stainless steel strip.

[0029] Other advantages, objects, and features of the present invention will be described in part in the following description and, in part, will be apparent to those skilled in the art upon examination of the following description or may be learned from practice of the present invention. The objects and other advantages of the present invention may be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below with reference to the accompanying drawings, in which:

[0031] Figure 1 This is a process flow chart of the production process of stainless steel with a textured surface for a gearbox friction plate of the present invention;

[0032] Figure 2 This is a picture of the 430 stainless steel surface after texturing in Example 1 of the present invention. DETAILED DESCRIPTION

[0033] The following describes the embodiments of the present invention by means of specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0034] Among them, the accompanying drawings are only for illustrative purposes and represent only schematic diagrams rather than actual pictures, and should not be understood as limiting the present invention. In order to better illustrate the embodiments of the present invention, some parts of the accompanying drawings may be omitted, enlarged or reduced, and do not represent the dimensions of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions may be omitted in the accompanying drawings.

[0035] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", "front", "back", etc. indicating directions or positional relationships, they are based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operate in a specific direction. Therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0036] Example 1

[0037] like Figure 1 The production process of a stainless steel with a textured surface for a hybrid transmission friction plate shown in the figure includes the following steps:

[0038] S1. Select 3.0mm×1250mm Shanxi Taiyuan Iron and Steel 430 stainless steel strip for preliminary rolling;

[0039] S2. The initial rolling of stainless steel strip is five passes with a total reduction rate of 38.3%. The reduction rates of the first four passes are 13%, 10%, 10%, and 7%, respectively, and the reduction rate of the last pass is 5%. The thicknesses after the five rolling passes are 2.61mm, 2.35mm, 2.11mm, 1.95mm, and 1.85mm, respectively. The working rolls for the initial rolling use high-strength M42 high-speed steel rolls, and the working rolls need to be replaced after each rolling pass. The surface roughness of the working rolls in the initial rolling process is obtained through the functional relationship between the surface roughness, the rolling passes, and the total reduction rate, and are Ra0.7, Ra0.6, Ra0.5, Ra0.4, and Ra0.3, respectively. The surface roughness of the rolls in each pass is quantified, and the surface roughness of the working rolls in each pass of the initial rolling is accurately controlled.

[0040] The functional relationship between the surface roughness of the working roll and the rolling pass is:

[0041] z1=INT(-0.11875x+3.25y)

[0042] z x =z x-1 -0.1

[0043] z1 is the target roughness value of the working roll in the initial rolling process, x is the total number of rolling passes in the initial rolling process, x=2~8, y is the total reduction rate, z x is the target roughness value of the working roll in the xth pass, z x-1 is the target roughness value of the working roll in the x-1th pass;

[0044] S3. After the initial rolling, the 1.85mm×1250mm 430 stainless steel strip is alkaline-washed for surface oil stains and then bright annealed. After the initial rolling, the 430 stainless steel strip has a large deformation, high internal deformation storage energy, and high internal stress in the strip, which is not conducive to the subsequent texturing rolling. The first bright annealing is performed in a horizontal bright annealing furnace with an annealing temperature of 890°C, a TV value of 3.0m / min, a hydrogen concentration of 99.99%, and an annealing tension of 22MPa.

[0045] S4. After the first bright annealing, the 430 stainless steel is subjected to one more pass of texturing rolling with a reduction ratio of 2.7%. The thickness of the stainless steel after rolling is 1.8 mm. The working rolls of the final texturing rolling pass are textured rolls, which are textured using a texturing machine. The surface parameters are Ra = 2.5 ± 0.1, RPc = 30 ± 20, and Rsk = 0.0 ± 0.2. The surface roughness of the 430 stainless steel after texturing meets the production requirements of friction plates.

[0046] S5. After rough rolling, the 1.8mm×1250mm 430 stainless steel strip needs a second bright annealing after alkali washing to completely recrystallize the rough rolling elongated grains into a stable state of equiaxed crystals, so that the performance of the friction plate is stable and the toughness is better. The second bright annealing uses a horizontal bright annealing furnace with an annealing temperature of 870℃, an annealing TV value of 3.0m / min, a hydrogen concentration of 99.999%, and an annealing tension of 12MPa. The surface of the strip after annealing is as follows: Figure 2 It can be seen that the textured surface of the stainless steel strip after two rolling and two bright annealing is uniformly granular.

[0047] S6. The 430 stainless steel after the second bright annealing is cut into strips, packaged and stored according to customer needs.

[0048] Example 2

[0049] A production process for a stainless steel strip with a textured surface for a hybrid transmission friction plate includes the following steps:

[0050] S1. Select 5.0mm×1250mm Shanxi Taiyuan Iron and Steel 430 stainless steel strip for preliminary rolling;

[0051] S2. The stainless steel strip is initially rolled in seven passes with a total reduction of 53.4%. The reductions of the first six passes are 12%, 10%, 11%, 10%, 10%, and 10%, respectively. The reduction of the last pass is 9%, and the thicknesses after the seven passes are 4.40mm, 3.96mm, 3.55mm, 3.19mm, 2.87mm, 2.58mm, and 2.33mm, respectively. The working rolls for the initial rolling use high-strength M42 high-speed steel rolls, and the working rolls need to be replaced after each rolling pass. The surface roughness of the working rolls in the initial rolling process is obtained through the functional relationship between the surface roughness and the rolling passes and the total reduction rate, which are Ra1.0, Ra0.9, Ra0.8, Ra0.7, Ra0.6, Ra0.5, and Ra0.4, respectively. The surface roughness of the rolls in each pass is quantified, and the surface roughness of the working rolls in each pass of the initial rolling is accurately controlled.

[0052] The functional relationship between the surface roughness of the working roll and the rolling pass is:

[0053] z1=INT(-0.11875x+3.25y)

[0054] z x =z x-1 -0.1

[0055] z1 is the target roughness value of the working roll in the initial rolling process, x is the total number of rolling passes in the initial rolling process, x=2~8, y is the total reduction rate, z x is the target roughness value of the working roll in the xth pass, z x-1is the target roughness value of the working roll in the x-1th pass;

[0056] S3. After the initial rolling, the 2.33 mm × 1250 mm 430 stainless steel strip is subjected to alkali washing to remove surface oil stains and then subjected to the first bright annealing. The first bright annealing is performed in a horizontal bright annealing furnace at an annealing temperature of 900° C., a TV value of 3.0 m / min, a hydrogen concentration of 99.999%, and an annealing tension of 25 MPa.

[0057] S4. After the first bright annealing, 430 stainless steel is subjected to two more passes of texturing rolling, with a total reduction of 22.7%. The reductions of the two passes are 15.88% and 8.16% respectively. The thickness of the stainless steel after the two passes is 1.96mm and 1.8mm respectively. The surface roughness of the working roll in the first pass of texturing rolling is the surface roughness of the working roll in the last pass of preliminary rolling, Ra0.3. The working roll in the last pass of texturing rolling uses a texturing roll, and the texturing roll is texturized using a texturing machine. The surface parameters are Ra = 2.6 ± 0.1, RPc = 30 ± 20, and Rsk = 0.0 ± 0.2.

[0058] S5. After roughening and rolling, the 1.8mm×1250mm 430 stainless steel strip needs a second bright annealing after alkali washing. The second bright annealing uses a horizontal bright annealing furnace with an annealing temperature of 880°C, an annealing TV value of 3.0m / min, a hydrogen concentration of 99.99%, and an annealing tension of 15MPa.

[0059] S6. The 430 stainless steel after the second bright annealing is cut into strips, packaged and stored according to customer needs.

[0060] Example 3

[0061] A production process for a stainless steel strip with a textured surface for a hybrid transmission friction plate includes the following steps:

[0062] S1. Select 4.0mm×800mm Shanxi Taiyuan Iron and Steel 430 stainless steel strip for preliminary rolling;

[0063] S2. The initial rolling of stainless steel strip is five passes with a total reduction rate of 43.75%. The reduction rates of the first four passes are 12%, 11%, 11%, and 11%, respectively, and the reduction rate of the last pass is 8%. The thicknesses after the five rolling passes are 3.5mm, 3.1mm, 2.76mm, 2.46mm, and 2.25mm, respectively. The working rolls for the initial rolling use high-strength M42 high-speed steel rolls, and the working rolls need to be replaced after each rolling pass. The surface roughness of the working rolls in the initial rolling process is obtained through the functional relationship between the surface roughness, the rolling passes, and the total reduction rate, and are Ra0.9, Ra0.8, Ra0.7, Ra0.6, and Ra0.5, respectively. The surface roughness of the rolls in each pass is quantified, and the surface roughness of the working rolls in each pass of the initial rolling is accurately controlled.

[0064] The functional relationship between the surface roughness of the working roll and the rolling pass is:

[0065] z1=INT(-0.11875x+3.25y)

[0066] z x =z x-1 -0.1

[0067] z1 is the target roughness value of the working roll in the initial rolling process, x is the total number of rolling passes in the initial rolling process, x=2~8, y is the total reduction rate, z x is the target roughness value of the working roll in the xth pass, z x-1 is the target roughness value of the working roll in the x-1th pass;

[0068] S3. After the initial rolling, the 2.25 mm × 1250 mm 430 stainless steel strip is subjected to alkali cleaning of the surface oil and then bright annealed for the first time. The first bright annealing is performed using a horizontal bright annealing furnace with an annealing temperature of 890° C., a TV value of 3.0 m / min, a hydrogen concentration of 99.999%, and an annealing tension of 23 MPa.

[0069] S4. After the first bright annealing, 430 stainless steel is subjected to three passes of texturing rolling. The total reduction is 20%, and the three-pass reductions are 9%, 7%, and 5%, respectively. The thicknesses of the stainless steel after the three passes are 2.05mm, 1.9mm, and 1.8mm, respectively. The surface roughness of the work rolls in the first two passes of texturing rolling is the same as the surface roughness of the work rolls in the last pass of preliminary rolling, Ra0.5. The work rolls in the last pass of texturing rolling use texturing rolls, and the texturing rolls are textured using a texturing machine. The surface parameters are Ra = 2.4 ± 0.1, RPc = 30 ± 20, and Rsk = 0.0 ± 0.2.

[0070] S5. After roughening and rolling, the 1.80mm×1250mm 430 stainless steel strip needs a second bright annealing after alkali washing. The second bright annealing uses a horizontal bright annealing furnace with an annealing temperature of 860°C, an annealing TV value of 3.0m / min, a hydrogen concentration of 99.99%, and an annealing tension of 18MPa.

[0071] S6. The 430 stainless steel after the second bright annealing is cut into strips, packaged and stored according to customer needs.

[0072] After testing and analysis, the range of surface performance parameters of the stainless steel strips prepared in Examples 1 to 3 is shown in Table 1:

[0073] Table 1 Surface performance parameter ranges of stainless steel strips prepared in Examples 1 to 3

[0074] Ra RPc Rsk Example 1 1.2～2.2 25～52 -0.2～0.4 Example 2 1.0～2.3 22～46 -0.1～0.6 Example 3 0.9～2.4 31～55 0.1～0.6

[0075] In summary, the present invention's combination of rationally selected texture roller surface parameters and the two-rolling, two-reeling process for the stainless steel strip ensures that the surface parameters of the final friction plate product remain stable within the desired range. Furthermore, the resulting textured stainless steel strip exhibits high strength, excellent toughness, and a long lifespan, meeting the production requirements for transmission friction plates and ensuring a smooth ride.

[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions, which should all be included in the scope of the claims of the present invention.

Claims

1. A production process for a stainless steel strip with a textured surface for a gearbox friction plate, characterized in that: The following steps are involved: S1. Raw material selection: 430 stainless steel with a thickness of 3.0mm to 5.0mm and a width of 1250mm; S2. Preliminary rolling: The selected 430 stainless steel raw material is rolled through N passes with a total reduction rate of 35% to 60%. The reduction rate of the first N-1 passes is between 5% and 18%, and the reduction rate of the Nth pass does not exceed 10%. Ordinary rolls are used for all N rolling passes. In the preliminary rolling process, the work rolls need to be replaced after each rolling pass. The relationship between the surface roughness of the work rolls in the preliminary rolling process and the total reduction rate as a function of the number of rolling passes is: z1=INT(-0.11875x+3.25y) With x =z x-1 -0.1 z1 is the target roughness value of the working roll in the initial rolling process, x is the total number of rolling passes in the initial rolling process, x=2~8, y is the total reduction rate, z x is the target roughness value of the working roll in the xth pass, z x-1 is the target roughness value of the working roll in the x-1th pass; S3, first bright annealing: the semi-finished stainless steel strip preliminarily rolled in step S2 is cleaned to remove surface oil stains and then bright annealed; S4, texture rolling: The steel strip after the first bright annealing in step S3 is rolled for M passes, with a total reduction rate not exceeding 25% and a single pass reduction rate not exceeding 17%. Conventional rolls are used for the first M-1 passes, and texture rolls are used for the Mth pass. The final product thickness is 1.8 mm. The surface roughness parameters of the working rolls during the final texture rolling pass in step S4 are: Ra = 2.5 ± 0.2, RPc = 30 ± 20, and Rsk = 0.0 ± 0.

4. The surface roughness parameters of the final stainless steel strip after the texture rolling in step S4 are: Ra = 0.9-2.6, RPc = 20-55, and Rsk = -0.4-0.

7. S5, second bright annealing: the stainless steel strip rolled in step S4 is cleaned to remove surface oil stains and bright annealed again; S6. Cutting into strips and storing: The stainless steel strips after the second bright annealing in step S5 are cut into strips, packaged and stored according to customer requirements.

2. The process for producing a textured surface of a stainless steel strip according to claim 1, wherein: The number of preliminary rolling passes in step S2 is N=4 to 8.

3. The process for producing a textured surface of a stainless steel strip according to claim 1, wherein: The first bright annealing in step S3 and the second bright annealing in step S5 are both performed using a horizontal bright annealing furnace; the annealing temperature is set at 860° C. to 900° C., the annealing furnace TV value is 3.0 m / min, the hydrogen concentration is 99.99%, and the annealing tension is 10 to 25 MPa.

4. The process for producing a textured surface of a stainless steel strip according to claim 1, wherein: The numerical value M in the roughening rolling in step S4 is 2 to 3.

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