Shape control method for copper-steel bimetallic bearing material produced by continuous casting method

Abstract

The present invention discloses a plate shape control method for producing copper-steel bimetallic bearing materials by a continuous casting method, wherein a convex roller is set at a predetermined position during the cooling process after the bimetallic strip is cast, and the predetermined position of the convex roller is set to a position where the temperature of the steel strip after cooling is 400-700°C. The convex roller is thick in the middle and thin at both ends, and the length of the convex roller is l. The difference between the maximum radius in the middle and the minimum radius at both ends is h, so that h / l is 0.005-0.1. After the bimetallic strip passes through the convex roller, an upward convex pre-deformation is generated at the bottom of the bimetallic strip; combined with cooling control, in the subsequent cooling process, the bimetallic strip becomes flat again due to the deformation and contraction of the upper part, which produces a deformation in the opposite direction of the pre-deformation, thereby achieving the purpose of reducing and preventing the deformation of the cross-section of the bimetallic strip.

Description

Technical Field

[0001] The invention belongs to the field of preparation of bimetallic bearing materials, and in particular relates to a plate shape control method for producing copper-steel bimetallic bearing materials by a continuous casting method. Background Art

[0002] Bimetallic bearing materials are essential key materials in diesel engines, internal combustion engines and other power machinery. Copper-steel bimetallic bearings have the advantages of high fatigue life and heavy load bearing capacity. The continuous casting method for producing copper-steel bimetallic bearings has the characteristics of low cost, stable performance, and good bimetallic bonding performance. Figure 1 The steel strip, gripped by traction rollers, passes continuously through various working zones, from the heating zone to the milling zone, completing the copper-steel bimetallic bearing manufacturing process. In the heating zone, the steel strip is heated to a specific temperature. In the pouring zone, molten copper alloy is poured onto the upper portion of the strip. In the cooling zone, forced cooling is achieved by spraying a coolant from the bottom of the strip or immersing the strip in the coolant. The copper alloy melt on the upper portion of the strip solidifies and cools along with the strip, resulting in a copper-steel bimetallic strip. In the milling zone, the upper copper alloy layer of the bimetallic strip is milled to remove impurities such as slag and ensure uniform thickness across each layer. Because the bimetallic strip is primarily cooled from the bottom during the manufacturing process, the upper portion of the strip cools and shrinks more slowly. This results in a downwardly convex bottom in the cross-section of the strip after cooling. Therefore, a dedicated leveling process is required before milling to level the bottom of the cooled bimetallic strip, a process known as flatness control.

[0003] The addition of the leveling process increases the equipment investment and operating costs. At the same time, due to the uneven thickness of the copper alloy layer in the bimetallic strip after casting and the irregular cross-section of the bimetallic strip, the manufacturing and adjustment of the leveling machine are more complicated than those of ordinary leveling machines. Specifically, Figure 2 Shown Figure 1 At section A, the bimetallic strip is formed after casting. The bimetallic strip 3 consists of a steel strip 1 and a copper alloy liquid 2 placed on it. The steel strip 1 has shoulders on both sides that extend beyond its center. These shoulders serve as grippers for the traction rollers and prevent the copper alloy liquid 2 from flowing out the sides of the strip. The temperature of the bimetallic strip 3 after casting is approximately 1150°C. After passing through the cooling zone, its temperature gradually drops to room temperature. Figure 3 As shown, in Figure 1 At the B section, since the bimetallic strip is cooled from the bottom, the upper portion corresponding to the copper alloy part lags in cooling and shrinking, and the bimetallic strip becomes a bimetallic strip 4 with a downwardly convex cross-section. Before the subsequent milling of the copper alloy layer, the bimetallic strip 4 needs to be changed into a bimetallic strip 4. Figure 4 The flat bottom shape shown corresponds to Figure 1 At the C section. Summary of the Invention

[0004] The purpose of the present invention is to solve the above technical problems and provide a plate shape control method for producing copper-steel bimetallic bearing materials by continuous casting method, thereby reducing equipment investment and operating costs.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] A plate shape control method for producing copper-steel bimetallic bearing materials by a continuous casting method is characterized in that a convex roller with a length greater than or equal to the bottom width of the steel strip is set at a predetermined position in the cooling zone after the bimetallic strip is cast, the convex roller is thick in the middle and thin at both ends, and the predetermined position is a position where the temperature of the cooled steel strip is 400-700°C. The relative height between the convex roller and the bimetallic strip is adjusted so that when the bimetallic strip passes through the convex roller, the bottom of the steel strip fits against the upper part of the convex roller, and the bottom of the bimetallic strip is pre-deformed to produce an upward bulge. In the subsequent cooling process, the bimetallic strip produces a reverse deformation due to the deformation and contraction of the upper part, and the bottom edge becomes flat again, thereby achieving the purpose of reducing or preventing deformation of the cross-section of the bimetallic strip.

[0007] The length of the convex top roller is l, and the difference between the maximum radius in the middle and the minimum radius at both ends is h, so that h / l is 0.005-0.1.

[0008] The side wall of the convex top roller in contact with the bottom of the bimetallic steel strip can be a circular arc, an elliptical arc or other smooth curves along its axis.

[0009] The range of h / l value can be roughly determined according to the deformation of the bimetallic strip when it is not corrected. Assume that the bottom width of the bimetallic strip is L, the bottom convex height caused by the delayed cooling and shrinkage of the upper part when the bimetallic strip is not corrected is H, and the convex or concave height of the bottom after correction is H1. h / l is 20-50% of H / L, which can roughly achieve the matching of pre-deformation and reverse deformation on an order of magnitude. Assume that the temperature of the steel strip at the convex top roller is a fixed value between 400-700℃. You can first take a value of h / l, such as 30% of H / L, and perform convex top roller correction. Measure the deformation after correction by the convex top roller. When the reverse deformation is greater than the pre-deformation, increase the h / l value; otherwise, reduce the h / l value. In this way, an h / l value can be obtained through the test, so that H1 / L<20%h / l, and the pre-deformation and reverse deformation are roughly the same.

[0010] A rough h / l value can be set, and then the temperature of the strip at the convex roller can be adjusted to achieve roughly the same pre-deformation and post-deformation, that is, H1 / L < 20% h / l. For example, if h / l = 40% H / L, the strip is corrected using a convex roller with a predetermined h / l value, and the offset of the deformation after correction by the convex roller is measured. If the post-deformation is greater than the pre-deformation, the temperature of the bimetallic strip passing through the convex roller can be reduced by increasing the distance between the convex roller and the copper alloy pouring gate, thereby reducing the post-deformation, and vice versa.

[0011] On the basis that pre-deformation and reverse deformation are roughly the same (H1 / L < 20% h / l), the reverse deformation is supplemented by adjusting the cooling intensity after the bimetallic strip passes through the convex roller. When the reverse deformation is less than the pre-deformation, the reverse deformation is increased by increasing the cooling medium flow rate at the bottom of the bimetallic strip to increase the cooling intensity; conversely, the medium flow rate is reduced, the cooling intensity is reduced, and the reverse deformation is reduced, so that the reverse deformation is equal to the pre-deformation, achieving a flat bottom. When the cooling method is bottom injection, the cooling intensity can be adjusted by directly adjusting the flow rate of the nozzle in the cooling zone after the steel strip passes through the convex roller; when the cooling zone is immersion, the cooling intensity can be adjusted by adding cooling medium nozzles in the cooling zone after the steel strip passes through the convex roller.

[0012] The beneficial effect of the present invention is that during the cooling process of a continuously cast copper-steel bimetallic strip, the bottom of the strip is lifted and deformed by a convex roller, creating an upwardly convex pre-deformation. During the subsequent cooling process, the strip undergoes a reverse deformation due to the upper deformation and contraction, returning it to a flat state. This reduces and prevents cross-sectional deformation of the strip. This method is simple and easy to implement, eliminating the need for a dedicated leveling machine, and maintaining the main process steps and process parameters of the original production process, making adjustments easy. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the embodiment of the present invention, the embodiment will be described below with reference to the accompanying drawings.

[0014] Figure 1 The figure is a structural diagram of the process of producing copper-steel bimetallic bearing bushes by continuous casting method in the prior art.

[0015] Figure 2 Schematic diagram of bimetallic strip obtained by casting in the prior art.

[0016] Figure 3 This is a schematic diagram of the cross-sectional shape of the bimetallic strip after cooling in the prior art.

[0017] Figure 4 Schematic diagram of the shape of the bimetallic strip required before milling in the prior art.

[0018] Figure 5 Schematic diagram of the contact between the bottom of the bimetallic strip and the convex top roller.

[0019] Figure 6 Schematic diagram of the cross section of the bimetallic strip after passing through the convex top roller.

[0020] Figure 7 Schematic diagram of the cross section of the bimetallic strip after cooling after convex top. DETAILED DESCRIPTION

[0021] The following examples are merely used to illustrate possible implementations of the present invention, but are not intended to limit the scope of the present invention.

[0022] Such as Figures 5 to 7 As shown, the present invention provides a plate shape control method for producing copper-steel bimetallic bearing materials by a continuous casting method, wherein a convex roller 5 is set at a predetermined position during the cooling process after the bimetallic strip is cast, and the predetermined position is a position where the temperature of the cooled steel strip is 400-700 degrees. The longitudinal section of the convex roller 5 is drum-shaped, thick in the middle and thin at both ends. The length of the convex roller is set to be greater than or equal to the width of the bimetallic strip, which is l. The difference between the maximum radius in the middle and the minimum radius at both ends is h, and h / l is 0.005-0.1, so that when the bimetallic strip passes through the convex roller, the entire bottom of the cross section of the steel strip fits with the convex roller. The side wall of the convex roller can be a circular arc, an elliptical arc or other smooth curve along its axis, preferably a circular arc, which will cause the bottom of the bimetallic strip 6 to produce an upward convex pre-deformation. h / l is the most important control parameter that determines the degree of pre-deformation of the bimetallic strip after passing through the roller; it becomes Figure 6 The shape shown. In the subsequent cooling process, the bimetallic strip deforms upward and shrinks, and then deforms in the opposite direction and becomes flat ( Figure 7 shown).

[0023] In summary, the present invention uses a convex top roller with a convexity to support the continuously passing bimetallic belt (such as Figure 5 ), pre-deform the bimetallic strip into a bimetallic strip with an upward convex shape (such as Figure 6 ), in the subsequent cooling of the bimetallic strip, the temperature and cooling intensity are adjusted to make the reverse deformation caused by the delayed cooling shrinkage of the upper part offset the pre-deformation, and return it to the shape of the bimetallic strip with a flat bottom (such as Figure 7 ). This achieves the purpose of reducing the cross-sectional deformation of the bimetallic strip and controlling the shape of the bimetallic strip.

[0024] The aforementioned convex ridge operation should be performed after the bimetallic strip has cooled to a certain temperature range to ensure smooth pre-deformation of the bimetallic strip. If the bimetallic strip temperature is too low, the lower strip will become very hard, making it difficult to deform it convexly using the crowned top rollers. To ensure smooth strip deformation, the strip temperature should be maintained above 400°C when passing through the crown rollers 5. If the bimetallic strip temperature is too high, the unsolidified copper alloy liquid will flow to the sides of the strip due to gravity, causing the thickness of the copper alloy layer in the bimetallic strip to vary. If the center section is too thin, it will be difficult to maintain the effective thickness of the copper alloy layer after milling. Therefore, the convex ridge operation should be performed after the copper alloy melt surface has substantially solidified. For commonly used copper-lead-tin alloys, the surface solidification temperature is approximately 600°C. Considering the temperature difference between the upper and lower surfaces of the bimetallic strip, the bottom surface temperature of the bimetallic strip should be controlled between 400-700°C during the convex ridge operation.

[0025] The degree of upward pre-deformation (hereinafter referred to as pre-deformation) of the bottom of the bimetallic strip after passing through the convex top roller is mainly determined by the h / l parameter of the aforementioned top roller. The larger the h / l, the greater the pre-deformation. The reverse deformation (hereinafter referred to as reverse deformation) of the bottom of the bimetallic strip after passing through the convex top roller is mainly determined by two factors: its temperature at the convex top roller and the cooling speed after passing through the convex top roller. The higher the temperature of the steel strip at the convex top roller, the greater its reverse deformation; the greater the cooling intensity of the steel strip after passing through the convex top roller, the greater its reverse deformation. Therefore, by controlling the three parameters of the convex top roller h / l, the temperature of the steel strip at the convex top roller, and the cooling intensity of the steel strip after passing through the convex top roller, the size of the pre-deformation and reverse deformation can be controlled so that the reverse deformation is equal to the pre-deformation, and the bottom of the steel strip will become flat.

[0026] To ensure the cooling structure and properties of the bimetallic material, the control of the cooling intensity after the strip passes through the cam rollers is limited, and generally, the adjustable amount is approximately 20% of the pre-deformation. Therefore, the main parameters for controlling the strip shape should be the h / l ratio and the temperature of the strip at the cam rollers. This is done to ensure that the pre-deformation and post-deformation are roughly the same. The post-deformation is then supplemented by adjusting the cooling intensity at the bottom of the strip after passing through the cam rollers to achieve a smoother bottom. Specifically, the bottom cooling intensity after the strip passes through the cam rollers is set to medium, which can be achieved by varying the cooling medium flow rate. The strip is then shaped and cooled by controlling the h / l ratio and the temperature of the strip at the cam rollers. The relative height of the convex or concave portion of the strip after shaping and cooling is measured and set to H1, ensuring that the pre-deformation and post-deformation are roughly the same, that is, H1 / L < 20% h / l. The post-deformation cooling intensity is then supplemented by adjusting the post-deformation cooling intensity to achieve a smoother bottom.

[0027] The h / l value range can be roughly determined based on the deformation of the bimetallic strip when it is uncorrected. Assume that the bottom width of the bimetallic strip is L, and the height of the convexity caused by the delayed cooling and shrinkage of the upper portion of the bimetallic strip when it is uncorrected (meaning before the original leveler) is H. H / L represents the degree of convex deformation of the bimetallic strip. Generally, an h / l of 20-50% of H / L can roughly achieve a matching of pre-deformation and post-deformation within an order of magnitude. Assuming a fixed strip temperature between 400-700°C at the crown roller, a h / l value of, for example, 30% of H / L can be used to perform crown roller correction. The deformation after crown roller correction can be measured. If the post-deformation exceeds the pre-deformation, the h / l value is increased; otherwise, the h / l value is reduced. Through testing, an h / l value can be determined that H1 / L is less than 20% h / l, making the pre-deformation and post-deformation roughly equal.

[0028] Alternatively, a rough h / l value can be set, and the temperature of the strip at the crown roller can be adjusted to achieve approximately the same pre-deformation and post-deformation, with H1 / L < 20% h / l. For example, if h / l = 40% H / L, the strip can be corrected using a crown roller with the specified h / l value, and the offset of the deformation after correction by the crown roller can be measured. If the post-deformation exceeds the pre-deformation, the temperature of the bimetallic strip passing through the crown roller can be reduced by increasing the distance between the crown roller and the copper alloy pouring gate, thereby reducing the post-deformation, and vice versa.

[0029] Assuming pre-deformation and post-deformation are roughly equivalent (i.e., H1 / L < 20% h / l), post-deformation is supplemented by adjusting the cooling intensity after the bimetallic strip passes through the convex rollers. If post-deformation is less than pre-deformation, the post-deformation is increased by increasing the cooling medium flow rate at the bimetallic strip's bottom to increase the cooling intensity. Conversely, the medium flow rate is reduced, reducing the cooling intensity and post-deformation, thus equalizing post-deformation and achieving a smooth bottom. When the cooling method is bottom-injection, the cooling intensity can be adjusted by directly adjusting the flow rate of the nozzles in the cooling zone after the strip passes through the convex rollers. When the cooling zone is immersion-type, the cooling intensity can be adjusted by adding cooling medium nozzles in the cooling zone after the strip passes through the convex rollers.

[0030] Take the continuous casting method for producing a 3.8mm thick (0.8mm copper alloy layer, 3.0mm steel layer) and 300mm wide copper-steel composite bearing as an example. A 3mm thick steel strip is used, heated to 1150°C, and the copper alloy CuPb20Sn1 is poured at 1150°C to a thickness of 5mm. Finally, the copper alloy layer is milled to a thickness of 0.8mm. To ensure quality, the bottom unevenness (horizontally, the same applies below) of the bimetallic strip must not exceed 1mm / m.

[0031] During production, without correction, the cross-sectional deformation of the copper-steel bimetallic strip was measured, revealing an unevenness exceeding 16 mm / m. Since the unevenness of the bimetallic strip's bottom edge remains constant before and after milling, the uncorrected bimetallic strip does not meet product requirements. In existing production, a leveling machine is used in the leveling area to level the bimetallic strip. The addition of a leveling step increases equipment investment and operating costs. Furthermore, due to issues such as uneven thickness of the copper alloy layer and irregular cross-section of the bimetallic strip after casting, the leveling machine becomes more complex to manufacture and adjust than standard levelers.

[0032] Remove the leveler, without changing the original process and process parameters, and add a convex roller with a length l of 300mm and a difference h between the maximum and minimum radius of the convex roller of 8mm in the cooling zone. The convex roller is set in the middle of the cooling zone, when the steel strip temperature is 550℃. Adjust the relative height of the convex roller and the bimetallic strip until the bottom edge of the bimetallic strip is completely in contact with the top edge of the roller, which will cause the bottom of the bimetallic strip 6 to produce an upward convex pre-deformation, becoming Figure 6 The shape is shown. During the subsequent cooling process, the bimetallic strip undergoes reverse deformation due to upward deformation and contraction, becoming flat. The bottom edge roughness of the bimetallic strip's cross section after passing through the cooling zone was measured to be approximately 1.5 mm / m. Further increasing the cooling medium flow rate and the intensity of the bimetallic strip's cooling after passing through the crown rollers increased the reverse deformation of the bimetallic strip, further offsetting the pre-deformation and reducing the bottom edge roughness to less than 1 mm / m, meeting operational requirements.

Claims

1. A method for controlling the plate shape of copper-steel bimetallic bearing materials produced by continuous casting, characterized in that: A convex roller with a length greater than or equal to the width of the bottom of the steel strip is set at a predetermined position in the cooling zone after the bimetallic strip is cast. The convex roller is thick in the middle and thin at both ends. The predetermined position is where the temperature of the cooled steel strip is 400-700°C. The relative height between the convex roller and the bimetallic strip is adjusted so that when the bimetallic strip passes through the convex roller, the bottom of the steel strip fits against the upper part of the convex roller, pre-deforming the bottom of the bimetallic strip to produce an upward bulge. During the subsequent cooling process, the bimetallic strip undergoes a reverse deformation due to the deformation and contraction of the upper part, and the bottom edge becomes flat again, thereby reducing or preventing the deformation of the cross-section of the bimetallic strip. The length of the convex roller is l, and the difference between the maximum radius in the middle and the minimum radius at both ends is h, so that h / l is 0.005-0.1; The range of h / l value is determined according to the deformation of the bimetallic strip when it is not corrected. The bottom width of the bimetallic strip is set to L, the bottom convex height caused by the delayed cooling and shrinkage of the upper part when the bimetallic strip is not corrected is H, the convex or concave height of the bottom after correction is H1, and h / l is 20-50% of H / L, which roughly achieves the matching of pre-deformation and reverse deformation on an order of magnitude. The temperature of the steel strip at the convex top roller is set to a fixed value between 400-700℃. First, take a value of h / l, perform convex top roller correction, and measure the deformation after correction by the convex top roller. When the reverse deformation is greater than the pre-deformation, increase the h / l value; otherwise, reduce the h / l value. In this way, an h / l value can be obtained through the test so that H1 / L<20%h / l, and the pre-deformation and reverse deformation are roughly the same.

2. The plate shape control method for producing copper-steel bimetallic bearing material by continuous casting method according to claim 1, characterized in that: The side wall of the convex top roller contacting the bottom of the bimetallic steel strip is a circular arc, an elliptical arc or other smooth curves along its axis.

3. The plate shape control method for producing copper-steel bimetallic bearing materials by continuous casting according to claim 1, characterized in that: Set an h / l value, and then adjust the temperature of the steel strip at the convex roller to achieve roughly the same pre-deformation and reverse deformation, that is, H1 / L<20%h / l, use the convex roller with a fixed h / l value to correct the deformation, and measure the deformation offset after correction by the convex roller; when the reverse deformation is greater than the pre-deformation, reduce the temperature of the bimetallic strip passing through the convex roller by increasing the distance between the convex roller and the copper alloy pouring gate to reduce the reverse deformation, and vice versa.

4. The plate shape control method for producing copper-steel bimetallic bearing material by continuous casting method according to claim 1, characterized in that: On the basis that the pre-deformation and the reverse deformation are roughly the same, the reverse deformation is supplemented by adjusting the cooling intensity after the bimetallic strip passes through the convex top roller. When the reverse deformation is less than the pre-deformation, the cooling intensity is increased by increasing the flow rate of the cooling medium at the bottom of the bimetallic strip; otherwise, the medium flow rate is reduced, the cooling intensity is reduced, and the reverse deformation is reduced, so that the reverse deformation is equal to the pre-deformation and the bottom is flat; when the cooling method is the lower injection type, the cooling intensity is adjusted by directly adjusting the flow rate of the cooling zone nozzle after the corresponding steel strip passes through the convex top roller; when the cooling zone is the immersion type, the cooling intensity is adjusted by adding a cooling medium nozzle in the cooling zone after the corresponding steel strip passes through the convex top roller.

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