Steel plate manufacturing method capable of controlling forming deflection

Abstract

The invention discloses a steel plate manufacturing method capable of controlling forming deflection. The steel plate manufacturing method comprises a heating procedure, a rolling procedure, a cooling procedure, a straightening and leveling procedure, a straightening and transverse cutting procedure, a heat treatment procedure and a cutting and forming procedure which are carried out in sequence. Feeding the casting blank into a heating furnace, heating to a set rolling temperature, feeding into a rolling mill, and rolling to form a plate blank; carrying out cooling treatment; carrying out straightening and flattening treatment; and after the structural stress and thermal stress are eliminated through transverse cutting treatment and a thermal treatment procedure, cutting forming is performed in a cutting forming procedure, and the finished steel plate is obtained. In the heating process, a hot blank is charged. The method has the beneficial effects that production is carried out according to basic requirements of finished steel plates, the purpose of meeting the standard production of the telescopic boom of the suspension arm is achieved, personalized characteristics of materials are controlled, the steel plate manufacturing process is designed from the source of steel plate production, the plate shape quality of the materials is essentially improved, and the machining and forming effect is remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of sheet metal manufacturing, and particularly to a method for manufacturing a steel plate with controllable forming deflection. Background Art

[0002] The truck crane industry has always been on the path of independent innovation and has its own clear development context. Especially in recent years, the truck crane industry has achieved remarkable development. Although there is still a certain gap compared with foreign countries, this gap is gradually narrowing, and the performance of domestic medium and small-tonnage truck cranes has been very perfect and highly competitive. With the implementation of relevant national policies and the rapid development of the truck crane industry, the competition has become increasingly fierce.

[0003] With the improvement of the strength of the steel plate and the reduction of its thickness, when manufacturing the telescopic boom of a truck crane, to ensure that the deflection of the boom meets the standard requirements, the requirements for materials and the forming difficulty have doubled. Because according to the forming characteristics of high-strength steel, the higher the material strength and the thinner the thickness, under the same forming conditions, the greater the forming difficulty. After forming the telescopic boom of the crane, it is even more difficult to ensure the deflection of the boom, which will affect the quality of the boom and may lead to problems such as inability to install subsequently or even safety issues. To ensure the operation rate of truck crane manufacturers and the quality of finished parts, qualitative changes have also occurred in the manufacturing and forming control processes of materials.

[0004] Currently, the problem of forming deflection of the steel used for truck crane booms is widespread. In order to be used subsequently, measures must be taken for rescue and correction. The common methods in the industry include hammering and flame heating. Hammering mainly relies on manual operation to correct the deflection of the boom by borrowing the external force. However, for some severely excessive deflection problems, hammering alone is not sufficient for correction, and at this time, flame heating is required for correction. These correction methods are all carried out manually, which is time-consuming and laborious, and it is difficult to ensure the plate shape quality of the final finished parts. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for manufacturing a steel plate with controllable forming deflection, aiming to improve the plate shape quality of the finished steel plate for truck crane booms, in view of the deficiencies of the prior art.

[0006] The technical solution adopted by the present invention is as follows: A method for manufacturing a steel plate with controllable forming deflection, including the following steps in sequence: heating process, rolling process, cooling process, straightening and leveling process, straightening and transverse cutting process, heat treatment process, and cutting and forming process: In the heating process, the billet is fed into the heating furnace and heated to the set rolling temperature; in the rolling process, the heated billet is fed into the rolling mill for rolling to form a slab; in the cooling process, the rolled slab is cooled by the cooling device at the outlet of the rolling mill; in the straightening and leveling process, the cooled slab is straightened by the straightening machine and then leveled by the leveling machine; in the straightening and transverse cutting process, the leveled slab is straightened by the straightening machine and then transversely cut, and after eliminating the tissue stress and thermal stress through the heat treatment process, it is cut and formed in the cutting and forming process to obtain the finished steel plate.

[0007] According to the above solution, in the heating process, hot billets are charged into the furnace, the charging temperature is 420 - 520 °C, the temperature in the heating furnace is precisely controlled at 1300 ± 20 °C, and the duration is 58 - 68 min.

[0008] According to the above solution, in the rolling process, the billet is successively subjected to rough rolling and finish rolling. Among them, in the rough rolling stage, a 1 + 5 pass rolling mode is used. First, the first roughing mill performs 1 rolling pass, and then the second roughing mill performs 5 rolling passes; the side bend value at the head of the rough rolling is ≤ 20 mm.

[0009] According to the above solution, during finish rolling, the front-end F1 - F4 stands adopt a large crown control strategy with a proportional crown of 18 - 22 μm / mm, and the rear-end F5 - F7 stands adopt an equal-proportion crown control strategy of 5.2 - 5.6 μm / mm.

[0010] According to the above solution, in the cooling process, a uniform high-pressure water jet is simultaneously sprayed to cover the surface of the steel plate, the upper-lower water ratio is controlled at 0.75 - 0.85, and the temperature cooling rate of the sheet is controlled at 162 °C - 182 °C / s; then the temperature of the sheet is reduced to the coiling temperature of 600 - 640 °C by air cooling.

[0011] According to the above solution, in the straightening and leveling process, the six-high straightening machine adopts a constant pressure setting, and the roll gap setting value is -(6 - 8) mm; the leveling speed is controlled at 34 - 70 m / min, and the leveling rolling force is maintained at 550 - 600 t.

[0012] According to the above solution, in the straightening and transverse cutting process, a process of automatically tracking and pressing down with deep bending rolls as the coil diameter of the sheet changes is used. In the primary straightening, a large reduction is used for one-time pressing and straightening, and the reduction amount is set at 24 - 28 mm.

[0013] According to the above solution, in the straightening and transverse cutting process, the finish straightening uses a segmented straightening model parameter for straightening production, implements a positive bending roll strategy, controls the straightening plastic strain ratio at 76% - 82%, and makes the apparent flatness of the sheet ≤ 3 mm / m.

[0014] According to the above solution, in the heat treatment process, vacuum radiation heating is used to quench and temper the straightened and cross-cut plates. The tempering temperature is controlled in the range of 521 - 551 °C, and the holding time is 110 - 125 min.

[0015] According to the above solution, in the cutting and forming process, laser cutting and stamping and bending forming are used to control the strip steel plates.

[0016] The beneficial effects of the present invention are as follows:

[0017] 1. Based on the basic requirements of the finished steel plates and aiming to meet the standardized production of the telescopic boom, the present invention controls the personalized characteristics of the materials for production. Starting from the source of steel plate production, the parameters in the steel plate manufacturing process are designed. By optimizing the parameters of each process such as heating, rolling, and cooling, the shape quality of the materials is essentially improved, and the processing and forming effect is significantly enhanced. Compared with the traditional manufacturing method, the produced steel plates are superior in terms of the flatness of the plate shape, the uniformity of internal stress, etc., providing a better foundation for subsequent processing and greatly reducing the processing difficulties and waste rate caused by poor plate shape.

[0018] 2. In the heating process of the present invention, the hot billet charging method is adopted, which can improve production efficiency and reduce energy consumption without affecting the microstructure and properties of the cast billet materials. At the same time, it avoids the generation of uneven internal stress during the high-temperature - cooling - reheating process of the cast billet; in the rolling process, in the rough rolling stage, 1 + 5 passes of rolling are carried out. The first pass of rolling by the first roughing mill performs a preliminary large deformation rolling on the cast billet, providing a suitable blank shape and size for the subsequent 5 passes of fine processing by the second roughing mill, which is beneficial to improving the dimensional accuracy and surface quality of the product.

[0019] 3. In the cooling process of the present invention, the ultra-fast cooling process is adopted in the front section. The high-pressure jet water can break the gas film generated during high-temperature cooling, converting the cooling from film boiling cooling to nucleate boiling cooling state, avoiding the plate shape deformation and sharp increase in internal stress caused by uneven cooling in the transition boiling state. The differential water ratio control can uniformly cool the material in the thickness direction, reducing the generation of defects such as L warp and arch back.

[0020] 4. In the straightening and leveling process of the present invention, through a combination of parameters such as the specific setting of the straightening machine roll gap, the input of the skin pass mill deep bending roll, the speed and rolling force control, and the setting of the backup roll grinding crown, it can ensure that the edge wave defects are fully eliminated during the leveling process of the plate, the original curvature is completely eliminated, the generation of L wave defects is avoided, the internal stress state of the material is evenly distributed, and the apparent plate shape is good; in the straightening and cross-cutting process, the deep bending roll automatic tracking and pressing process can reduce or eliminate the additional original curvature generated after the plate is leveled and recoiled. The parameter settings of the preliminary straightening and finishing straightening can further eliminate and homogenize the internal stress of the plate, ensuring that the apparent flatness of the plate meets the requirements. Brief Description of the Drawings

[0021] Figure 1 Schematic diagram of the deflection of the lower cover plate of the telescopic boom of the truck crane in Embodiments 1 - 6 Figure 1 。

[0022] Figure 2 Schematic diagram of the deflection of the lower cover plate of the telescopic boom of the truck crane in Embodiments 1 - 6 Figure 2 。 Detailed Embodiments

[0023] To better understand the present invention, the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0024] A method for manufacturing a steel plate capable of controlling the forming deflection, the method comprising successively performing a heating process, a rolling process, a cooling process, a leveling and straightening process, a straightening and cross-cutting process, a heat treatment process, and a cutting and forming process;

[0025] In the heating process, the billet is fed into a heating furnace and heated to a set rolling temperature: in the rolling process, the heated billet is fed into a rolling mill for rolling to form a slab; in the cooling process, the rolled slab is cooled by a cooling device at the outlet of the rolling mill; in the leveling and straightening process, the cooled slab is straightened by a straightening machine and then leveled by a leveling machine; in the straightening and cross-cutting process, the leveled slab is straightened by a straightening machine and then cross-cut, and after eliminating the tissue stress and thermal stress through the heat treatment process, it is cut and formed in the cutting and forming process to obtain a finished steel plate.

[0026] Preferably, in the heating process, hot billets are charged into the furnace, and the charging temperature is 420 - 520 °C (the temperature of the billet has reached 420 - 520 °C before being charged into the heating furnace). Without affecting the tissue properties of the billet material, the production efficiency can be improved, energy consumption can be reduced, and at the same time, uneven internal stress generated during the process of high temperature - cooling - reheating of the billet can be avoided; the temperature of the high-temperature section in the heating furnace is 1300 ± 20 °C, and the time of the high-temperature section is 58 - 68 min, so that the austenitization of the billet tissue is uniform and the temperature is uniform, thus providing favorable conditions for subsequent uniform and low-stress rolling.

[0027] Preferably, in the rolling process, the billet is first rough-rolled and then finish-rolled. In the rough-rolling stage, 1 + 5 passes of rolling are adopted, that is, first, the billet is rolled 1 time through the first roughing mill to perform preliminary large-deformation rolling on the billet, perform preliminary compression and shaping on the slab, and provide a suitable blank shape and size for subsequent rolling; then, the billet is rolled 5 times by the second roughing mill (R2) to perform fine processing on the blank, making the thickness, width, shape, etc. of the blank closer to the requirements of the finished product, which is beneficial to improving the dimensional accuracy and surface quality of the product.

[0028] During the rough rolling process, the head of the steel plate may bend to one side, and the degree of this bend is measured by the side bend value. The side bend value control at the rough rolling head is ≤20 mm, providing good forming and shape control conditions for finish rolling. In the finish rolling stage, several front-end stands of the finish rolling (specifically, the four stands F1 - F4) adopt a large crown control strategy with a proportional crown of 18 - 22 μm / mm to ensure the stability and uniform deformation at the front end of rolling, greatly reducing the internal stress of deformation; several rear-end stands of the finish rolling (specifically, the three stands F5 - F7) adopt an equal-proportion crown control strategy of 5.2 - 5.6 μm / mm to control the flatness of the rolled sheet shape within the range of ±20 I, basically eliminating the wavy and L-shaped warpage morphologies of the rolled sheet shape, and making the longitudinal, thickness, width shapes and internal stresses of the material in a uniformly distributed state. According to the characteristics of shape heredity, it also provides better conditions for the shape control and processing of subsequent processes. The crown refers to the difference between the center thickness and the edge thickness of the cross-section of the steel plate, and the proportional crown is the ratio of the crown to the thickness of the steel plate.

[0029] Preferably, in the cooling process, the cooling is carried out by combining the ultra-fast cooling process in the front section with air cooling. First, the laminar flow cooling device uses the upper and lower headers to simultaneously spray a uniform high-pressure water jet to cover the surface of the steel plate to achieve ultra-fast cooling at high temperatures; the water volume of the upper and lower water pipes can be adjusted, and the upper-lower water ratio is controlled within the range of 0.75 - 0.85 (upper-lower water ratio = water volume of the upper header / water volume of the lower header), and the cooling rate of the sheet temperature is controlled at 162℃ - 182℃ / s; then the air cooling is used to reduce the sheet temperature to the coiling temperature of 600 - 640℃.

[0030] In the present invention, the high-pressure jet water of ultra-fast cooling is sufficient to break through the gas film generated during high-temperature cooling, enabling the cooling to be converted from film boiling cooling to nucleate boiling cooling state, avoiding the shape deformation and sharp increase in internal stress caused by uneven cooling in the transition boiling state, reducing the influence on the forming performance of the material, and controlling the differential water ratio to cool the material uniformly in the thickness direction, avoiding the generation of defects such as L-shaped warpage and arched back, and making the internal stress in the thickness direction small and uniform; the subsequent air cooling further reduces the influence of laminar flow cooling water on the temperature uniformity of the sheet, further ensuring the uniform cooling effect.

[0031] Preferably, in the straightening and leveling process, a straightening machine is arranged at the leveling inlet. The strip steel is straightened by the straightening machine before leveling. The six-roll straightening is set with a constant pressure (using a six-roll straightening machine), and the roll gap setting value is -(6 - 8) mm (this roll gap represents the distance between the upper roll of the straightening machine and the straightening horizontal line); when entering the leveling machine for leveling treatment, the deep bending rolls of the leveling are fully engaged, the leveling speed is controlled at 34 - 70 m / min, the leveling rolling force is controlled at 550 - 600 t, and the leveling backup rolls are ground with a +(1 - 3) micron crown roll shape and combined with the positive bending roll leveling model parameter setting for leveling.

[0032] In the present invention, through the parameter setting of the straightening and leveling process, it can be ensured that the edge waviness defects of the sheet are fully eliminated during the leveling process, the original curvature is completely eliminated, the generation of L-shaped waviness defects is avoided, and thus a material with a uniform internal stress state distribution and a good apparent sheet shape is obtained.

[0033] Preferably, in the straightening and cross-cutting process, a deep bending roll is used to automatically track the rolling-down process with the change of the sheet coil diameter, continuously applying a reverse bending moment to the original coil to reduce or eliminate the additional original curvature generated after the sheet is leveled and recoiled. For the primary straightening, a large rolling-down is carried out once for rolling-down straightening, and the rolling-down amount is set to 24 - 28 mm; for the finish straightening, a segmented straightening model parameter is used for straightening production, with a positive bending roll strategy, and the straightening plastic strain ratio is controlled to be 76% - 82%, so that the apparent flatness of the sheet is ≤ 3 mm / m, completely eliminating the edge waves, L-warping and other morphologies of the sheet, and further eliminating the internal stress of the sheet and homogenizing it. The straightened strip steel is subjected to cross-cutting treatment.

[0034] Preferably, in the heat treatment process, the sheet after straightening and cross-cutting is quenched and tempered by vacuum radiation heating to eliminate the stress of the sheet and adjust the material properties; the tempering temperature is controlled in the range of 521 - 551 °C, and the holding time is 110 - 125 min to ensure that there is no change and uniformity in the internal structure of the sheet, making the mechanical service performance of the sheet excellent, and eliminating the tissue stress and thermal stress, so as to minimize and evenly distribute the stress inside the sheet.

[0035] Preferably, in the cutting and forming process, the forming of the sheet is controlled by laser cutting and stamping and bending forming. Through the control design of the subsequent user laser cutting process, the R-angle compensation process of the die bending, the multi-pass progressive stamping and bending process, the bending stamping speed, and the holding time, it is ensured that the sheet meets the process requirements for the production performance of the boom parts, and the deflection in the length direction of the boom parts after bending and forming is ≤ 6 mm.

[0036] In the present invention, the control of the subsequent user laser cutting process, the R-angle compensation process of the die bending, the multi-pass progressive stamping and bending process, the bending stamping speed, and the holding time are all set by existing technologies.

[0037] In the present invention, the equipment used in each process is a mature equipment in the industry, only the relevant parameters are designed, and there is no improvement in the structure of the process equipment; other process parameters not mentioned in this application are set according to the conventional settings.

[0038] The present invention can be used for the manufacturing and forming deflection control of steel plates with a thickness of 3.01 - 6.01 mm, a length ≤ 11.2 m, and a strength grade of 915 - 1035 MPa, and can specifically be used for the deflection control of the telescopic arm cover plate of a truck crane.

[0039] In the present invention, ensuring the shape quality of the plate and the coordination of the bending process are the keys to solving the deflection problem. The control of the plate deflection is related to the processes of the entire production flow.

[0040] Examples 1 - 6

[0041] As Figure 1 and Figure 2 shown, the bent forming part 1 of the lower cover plate of the telescopic boom of a truck crane, which is also the finished steel plate to be obtained in Examples 1 - 6, is horizontally placed on the detection platform 2. By measuring the distance (the maximum distance) between the lower contour line of the finished steel plate and the straight line (the dotted line in Figure 1 ), that is, the vertical projection of the lower contour on the detection platform 2, the deflection in the entire length direction of the part is fed back. The thickness of the finished steel plate is 3.01 - 6.01 mm, the length ≤ 11.2 m, the strength grade is 915 - 1035 MPa, and the deflection in the length direction ≤ 6 mm. In Examples 1 - 6, the finished steel plate is obtained by the above method (the slab specifications in Examples 1 - 6 are the same). The relevant parameter settings for the heating process, rolling process, and cooling process in Examples 1 - 6 are shown in Table 1; the relevant parameter settings for the leveling process and straightening and cross-cutting process are shown in Table 2; the relevant parameter settings for the heat treatment process are shown in Table 3; the head and tail of the steel plate after heat treatment are protected and cooled, and the mechanical properties of the obtained original steel plate are shown in Table 4; after the original steel plate is cut, multiple bending operations are carried out according to the process technical plan. The bending process parameters in Examples 1 - 6 are implemented according to Table 5, and the overall bending effect is shown in Table 6. Comparative Examples 1 - 3 are obtained by the existing traditional methods, and the relevant parameters of the obtained plate shapes are shown in Table 6. Through comparative analysis, when the finished thickness is the same, the deflection of the part finished products obtained by the method of the present invention is much smaller than that of the part finished products obtained by the existing technology. The advantages of the technical solution of the present invention in terms of plate deflection control are obvious.

[0042] Table 1 Relevant parameter settings for each process in Examples 1 - 6

[0043]

[0044] Table 2 Relevant parameter settings for the leveling process and straightening and cross-cutting process in Examples 1 - 6

[0045]

[0046] Table 3 Relevant parameter settings for the heat treatment process in Examples 1 - 6

[0047] Example Thickness / mm Tempering temperature / ℃ Insulation time / min 1 3.10 532 121 2 3.75 542 123 3 4.12 539 119 4 4.65 545 118 5 5.55 539 120 6 6.01 550 124

[0048] Table 4 Mechanical properties of the original steel plate

[0049]

[0050]

[0051] Table 5 Related parameter settings for the bending process

[0052]

[0053] Table 6 Straightness after overall bending

[0054] Example Thickness / mm Deflection of the bent part / mm 1 3.10 5.5 2 3.75 5.2 3 4.12 5.0 4 4.65 4.8 5 5.55 5.2 6 6.01 4.5 Comparative example 1 3.10 17.5 Comparative example 2 4.65 16.4 Comparative example 3 6.01 13.2

[0055] The content not described in detail in this specification belongs to the prior art well-known to those skilled in the art.

[0056] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. However, any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for manufacturing a steel plate capable of controlling forming deflection, characterized in that: It includes a heating process, a rolling process, a cooling process, a straightening and leveling process, a straightening and cross-cutting process, a heat treatment process and a cutting and forming process which are carried out in sequence: in the heating process, the ingot is fed into a heating furnace and heated to a set rolling temperature; in the rolling process, the heated ingot is fed into a rolling mill for rolling to form a slab; in the cooling process, the slab after rolling is cooled by a cooling device at the outlet of the rolling mill; in the straightening and leveling process, the cooled slab is straightened by a straightener and then leveled by a leveler; in the straightening and cross-cutting process, the leveled slab is straightened by a straightener and then cross-cut, and then, after the structural stress and thermal stress are eliminated by a heat treatment process, it is cut and formed in the cutting and forming process to obtain a finished steel plate.

2. The method for manufacturing a steel plate capable of controlling forming deflection according to claim 1, characterized in that: In the heating process, the hot billet is charged into the furnace with a charging temperature of 420-520°C. The temperature in the heating furnace is precisely controlled at 1300±20°C and the heating duration is 58-68 minutes.

3. The method for manufacturing a steel plate capable of controlling forming deflection according to claim 2, characterized in that: In the rolling process, the ingot is subjected to rough rolling and finish rolling in sequence. The rough rolling stage adopts a 1+5-pass rolling mode, where the first rough rolling mill performs one rolling, and then the second rough rolling mill performs five rolling. The lateral bending value of the rough rolling head is ≤20mm.

4. The method for manufacturing a steel plate capable of controlling forming deflection according to claim 3, characterized in that: During finish rolling, the front end F1~F4 stands adopt a large crown control strategy with a proportional crown of 18~22μm / mm, and the rear end F5~F7 stands adopt an equal proportional crown control strategy of 5.2~5.6μm / mm.

5. The method for manufacturing a steel plate capable of controlling forming deflection according to claim 4, characterized in that: During the cooling process, a uniform high-pressure water jet is sprayed simultaneously to cover the surface of the steel plate. The upper and lower water ratio is controlled at 0.75-0.85, and the temperature cooling rate of the plate is controlled at 162°C-182°C / s. Air cooling is then used to reduce the plate temperature to a coiling temperature of 600-640°C.

6. The method for manufacturing a steel plate capable of controlling forming deflection according to claim 5, characterized in that: In the straightening and leveling process, the six-roller straightening machine adopts a constant pressure setting, and the roll gap setting value is -(6~8)mm; the leveling speed is controlled at 34~70m / min, and the leveling rolling force is maintained at 550~600t.

7. The method for manufacturing a steel plate capable of controlling forming deflection according to claim 6, characterized in that: In the straightening and cross-cutting process, deep bending rollers are used to automatically track the pressing process as the coil diameter of the plate changes. The initial straightening is performed by pressing down once with a large amount of pressure, and the pressure reduction is set to 24 to 28 mm.

8. The method for manufacturing a steel plate capable of controlling forming deflection according to claim 7, characterized in that: In the straightening and cross-cutting process, the fine straightening adopts the segmented straightening model parameters for straightening production, implements the positive bending roll strategy, controls the straightening plastic strain ratio at 76% to 82%, and makes the apparent plate shape unevenness ≤3mm / m.

9. The method for manufacturing a steel plate capable of controlling forming deflection according to claim 8, characterized in that: In the heat treatment process, vacuum radiation heating is used to quench and temper the straightened and cross-cut plates. The tempering temperature is controlled in the range of 521 to 551°C, and the holding time is 110 to 125 minutes.

10. The method for manufacturing a steel plate capable of controlling forming deflection according to claim 9, characterized in that: In the cutting and forming process, laser cutting and stamping and bending are used to control the strip steel plate.

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