Ultra-high strength sheet material limit bending compound forming method

Abstract

The application discloses a kind of super high strength plate limit bending composite forming method, comprising: super high strength plate is carried out whole plate heat treatment, comprising: whole plate normalizing, whole plate quenching, whole plate tempering;After super high strength plate of whole plate heat treatment is segmented into workpiece monomer, workpiece monomer is bent into required shape using low-temperature heating step bending forming process.The application can make super high strength plate directly bent into finished product, solve the problem that super high strength material appears crack or breaks when limit bending.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of limit processing of ultra-high strength plate, and particularly relates to a limit bending composite forming method of ultra-high strength plate. BACKGROUND

[0002] According to the definition of the domestic standard, the strength greater than 600 MPa belongs to ultra-high strength material. The bending radius R is close to or equal to the material thickness, which belongs to limit bending. With the development of energy saving and light weight, the application of ultra-high strength steel plate in production and manufacturing is favored. At present, when the bending structure of the ultra-high strength steel plate is produced and processed, the hot bending forming is usually adopted first, and then the heat treatment is carried out to meet the strength requirement. In actual production, the large-sized steel plate cannot be realized by hot pressing forming, and in addition, after the steel plate is bent and formed, the heat treatment is carried out, the heat treatment deformation is uncontrollable, and the heat treatment cannot be economically controlled or corrected, so the forming size requirement cannot be met.

[0003] When the workpiece is bent, the outer layer of the material fillet area is stretched, and the inner layer is compressed. The smaller the relative bending radius r / t (t is the thickness of the plate), the greater the tangential deformation degree during bending. That is, when the thickness t of the material is constant, the smaller the inner fillet r of the bending, the greater the stretching and compression ratio of the material, and the greater the tensile stress and tensile strain of the outer surface of the deformation zone. When the tensile strain exceeds the limit of the performance of the workpiece material, even cracks or breakage may occur. SUMMARY

[0004] The purpose of the application is to provide a limit bending composite forming method of ultra-high strength plate, which can directly bend and form the ultra-high strength plate into a finished product, and solve the problem of cracks or breakage of the ultra-high strength material during limit bending.

[0005] To achieve the above purpose, the technical solution used by the application is:

[0006] The limit bending composite forming method of the ultra-high strength plate comprises:

[0007] The whole plate of the ultra-high strength plate is heat treated, including: whole plate normalizing, whole plate quenching and whole plate tempering;

[0008] The ultra-high strength plate after the whole plate heat treatment is divided into workpiece monomers, and the workpiece monomers are bent into the required shape by using a low-temperature heating step-by-step bending forming process.

[0009] Further, the heating temperature of the whole plate normalizing is 900±10 DEG C, the holding time is 25-30 min, and the cooling mode is air cooling; the quenching heating temperature of the whole plate quenching is 910±10 DEG C, the quenching holding time is 25-30 min, and the cooling mode is water cooling, and the cooling speed is 270-600 DEG C / s; the heating temperature of the whole plate tempering is 550 DEG C±10, the tempering holding time is 2.5-3.0 h, the cooling mode is water cooling, and the cooling speed is 270-600 DEG C / s.

[0010] Further, the low-temperature heating step-by-step bending forming process adopts a combined bending die to bend the workpiece monomer into a required shape, and the combined bending die comprises an upper die and a lower die, the upper die and the lower die are used in cooperation, the front end of the upper die is provided with an extrusion end face, the rear part of the upper die is provided with a connecting rod, the extrusion end face is an arc surface, the bending radius of the arc surface is R, and the connecting rod is used for connecting an extruder; the lower die is provided with a lower die groove in the middle part, the two side surfaces of the lower die groove are perpendicular to each other, the connecting position of the two side surfaces is an arc surface, and the bending radius of the arc surface is R.

[0011] Further, the low-temperature heating step-by-step bending forming process comprises the following steps: laying lubricating paper on the lower die groove of the lower die, placing the workpiece monomer on the upper part of the lower die groove, and laying lubricating paper on the top of the workpiece monomer; the extrusion end face of the upper die is abutted against the workpiece monomer, the extrusion end face of the upper die is pressed downwards to bend the workpiece monomer to a first bending angle, the workpiece monomer after the first bending is subjected to low-temperature tempering treatment at 420±10 DEG C, the tempering treatment time is 1-1.5 h, and the stress generated in the first bending process is removed; the second bending process is carried out, the extrusion end face of the upper die is abutted against the bending part of the workpiece monomer, the extrusion end face of the upper die is pressed downwards to bend the workpiece monomer to a second bending angle, and the required shape of the part is achieved.

[0012] Further, the thickness of the workpiece monomer is 5 mm, and R=6 mm.

[0013] Further, the first bending angle is 120-135 DEG, and the second bending angle is 90 DEG.

[0014] Further, before the super-high-strength plate material after the whole plate heat treatment is divided into workpiece monomers, the super-high-strength plate material after the whole plate heat treatment is subjected to sand blasting and correction.

[0015] The technical effects of the present application include:

[0016] The present application can directly bend the super-high-strength plate material meeting the required performance into a finished product, effectively solves the problem that the deformation after heat treatment cannot be corrected after bending, and the limit bending does not produce bending cracks or breakage, and solves the problem that cracks or breakage occur when the super-high-strength material is subjected to limit bending.

[0017] The present application improves the comprehensive performance of the part after heat treatment by whole plate heat treatment, and realizes the limit forming manufacturing process by using low-temperature heating step-by-step bending forming process, solves the problem of cracks or breakage of the material in the limit bending, and solves the problem of not reaching the correction standard caused by bending first and then heat treatment. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is the side structure schematic diagram of the upper die in the present application;

[0019] Figure 2 is the side structure schematic diagram of the lower die in the present application;

[0020] Figure 3 is the process schematic diagram of the step-by-step bending forming in the present application. DETAILED DESCRIPTION

[0021] The following description fully illustrates the specific embodiments of the present application to enable a person skilled in the art to practice and reproduce.

[0022] The specific steps of the limit bending composite forming method of the ultra-high strength plate are as follows:

[0023] Step 1: whole plate heat treatment is performed on the ultra-high strength plate, including: whole plate normalizing, whole plate quenching, and whole plate tempering.

[0024] The ultra-high strength plate adopts 25CrMnSiA steel plate with length, width and height of 2500*1500*5mm, a normalizing process is added through heat treatment, the purpose of whole plate quenching is to obtain martensite structure, improve the hardness and strength of the material, and the whole plate tempering temperature is adjusted to improve the comprehensive performance of the part after heat treatment. After the whole plate heat treatment, the performance reaches the Q690-WJ533-1997 standard, and the Q690 yield strength is above 690MPa.

[0025] The purpose of the whole plate normalizing is to homogenize the structure, refine the grains, and improve the mechanical properties; the heating temperature is 900±10℃, the holding time is 25-30min, and the cooling mode is air cooling, natural cooling.

[0026] The specific process of the whole plate quenching is that the quenching heating temperature is 910±10℃, the quenching holding time is 25-30min, and the cooling mode is water cooling, and the cooling speed is 270-600℃ / s.

[0027] The purpose of the whole plate tempering is to obtain tempered martensite, eliminate the internal stress of the quenched steel, improve the toughness and plasticity, and the specific process of the whole plate tempering is that the heating temperature is 550℃±10, the tempering holding time is 2.5-3.0h, the cooling mode is water cooling, and the cooling speed is 270-600℃ / s.

[0028] Step 2: The ultra-high strength plate after heat treatment is divided into workpiece units 3, and the workpiece units 3 are bent into the required shape by using the low-temperature heating step-by-step bending forming process.

[0029] Step 21: The ultra-high strength plate after heat treatment is sandblasted, corrected, and laser cut to form workpiece units 3.

[0030] The purpose of sandblasting is to remove the iron oxide skin on the surface of the ultra-high strength plate. If the surface state has reached the required standard, sandblasting is not required. The purpose of correction is to correct the deformation that occurs during the heat treatment process to provide preparation work for the subsequent process. The purpose of laser cutting is to cut the ultra-high strength plate into the required size of the workpiece units 3 to provide raw materials for bending.

[0031] Step 22: The workpiece units 3 are bent into the required shape by using the low-temperature heating step-by-step bending forming process.

[0032] (1) Design and manufacture a combined bending die.

[0033] As shown in Figure 1 , it is a side structure schematic diagram of the upper die 1 in the present application; as shown in Figure 2 , it is a side structure schematic diagram of the lower die 2 in the present application.

[0034] The combined bending die comprises: an upper die 1 and a lower die 2, the upper die 1 and the lower die 2 are used in cooperation, the front end of the upper die 1 is provided with an extrusion end face 11, the rear part is provided with a connecting rod 12, the extrusion end face 11 is an arc surface, the bending radius R of the arc surface is 6 mm, and the connecting rod 12 is used for connecting the extruder; the lower die 2 is provided with a lower die groove 21 in the middle part, the two side surfaces of the lower die groove 21 are perpendicular, and the connecting position of the side surfaces is an arc surface, and the bending radius R of the arc surface is 6 mm.

[0035] (2) The bending forming process adopts a step-by-step bending method, and the purpose of the bending forming is to bend the workpiece units 3 into the required shape.

[0036] As shown in Figure 3 , it is a process schematic diagram of the step-by-step bending forming in the present application.

[0037] The low-temperature heating step-by-step bending forming process is as follows:

[0038] a. Laying lubricating paper on the lower die groove 21 of the lower die 2, placing the workpiece units 3 on the upper part of the lower die groove 21, and laying lubricating paper on the top of the workpiece units 3;

[0039] Selecting appropriate lubricating paper to be laid between the workpiece units 3, the upper die 1 and the lower die 2 to reduce the friction during the bending process, so as to reduce the tensile force suffered by the material.

[0040] b. The extrusion end face 11 of the upper die 1 is pressed against the workpiece 3, and the extrusion end face 11 presses the workpiece 3 downward to bend the workpiece 3 to a first bending angle α1 (in the preferred embodiment, α1 is 120-135°). The initially bent workpiece 3 is subjected to a low-temperature tempering treatment at 420±10°C for 1-1.5 hours to remove the stress generated during the first bending process;

[0041] c. Perform the second bending process, in which the extrusion end face 11 of the upper die 1 rests against the bend of the workpiece monomer 3, and the extrusion end face 11 presses down the workpiece monomer 3, bending the workpiece monomer 3 to the second bending angle α2 (α2 is 90° in this preferred embodiment) to achieve the required shape requirements of the part without cracks or breakage.

[0042] Since the thickness of workpiece 3 is 5mm and the bending radius R is 6mm, which is close to the plate thickness, this is an extreme forming process. Workpiece 3 is made of ultra-high-strength material. During extreme bending, cracks or fractures may occur at the R position, resulting in product failure. A composite forming method combining intermittent bending, heat treatment, and auxiliary (die and lubrication paper) processes achieves a qualified ultra-high-strength extreme bending process, eliminating the problem of cracking or fracture during extreme bending. Parts can include tie rods, welded and stamped parts, and high-strength structural components.

[0043] The terms used in this invention are descriptive and exemplary, rather than restrictive. Since the present invention can be embodied in a variety of forms without departing from the spirit or essence of the technical solution, it should be understood that the above-described embodiments are not limited to any of the foregoing details, but should be interpreted broadly within the spirit and scope of the appended claims. Therefore, all changes and modifications that fall within the scope of the claims or their equivalents are intended to be covered by the appended claims.

Claims

1. An ultra-high strength sheet limit bending compound forming method, characterized by, The method comprises: The whole plate is subjected to heat treatment, including: whole plate normalizing, whole plate quenching, and whole plate tempering; the heating temperature of the whole plate normalizing is 900±10℃, the holding time is 25-30min, and the cooling mode is air cooling; the quenching heating temperature of the whole plate quenching is 910±10℃, the quenching holding time is 25-30min, and the cooling mode is water cooling, and the cooling speed is 270-600℃ / s; the heating temperature of the whole plate tempering is 550℃±10, the tempering holding time is 2.5-3.0h, and the cooling mode is water cooling, and the cooling speed is 270-600℃ / s; The workpiece unit is bent into a required shape by using a low-temperature heating step-by-step bending forming process, the low-temperature heating step-by-step bending forming process adopts a combined bending die, and the workpiece unit is bent into a required shape by using the combined bending die, the combined bending die comprises: an upper die and a lower die, the upper die and the lower die are used in cooperation, the front end of the upper die is provided with an extrusion end face, the rear part of the upper die is provided with a connecting rod, the extrusion end face is an arc surface, the bending radius of the arc surface is R, and the connecting rod is used for connecting an extruder; the lower die is provided with a lower die groove in the middle part, the two side surfaces of the lower die groove are perpendicular to each other, the connecting position of the two side surfaces is an arc surface, and the bending radius of the arc surface is R; The low-temperature heating step-by-step bending forming process comprises the following steps: laying lubricating paper on the lower die groove of the lower die, placing the workpiece unit on the upper part of the lower die groove, and laying lubricating paper on the top of the workpiece unit; the extrusion end face of the upper die is abutted against the workpiece unit, the extrusion end face of the upper die is pressed downward to bend the workpiece unit to a first bending angle, the workpiece unit is subjected to 420±10℃ low-temperature tempering treatment for 1-1.5h to remove the stress generated in the first bending process; in the second bending process, the extrusion end face of the upper die is abutted against the bending part of the workpiece unit, the extrusion end face of the upper die is pressed downward to bend the workpiece unit to a second bending angle, and the workpiece unit reaches the required shape requirement.

2. The ultra-high strength sheet limit bend hybrid forming method of claim 1, wherein, The thickness of the workpiece unit is 5mm, and R=6mm.

3. The ultra-high strength sheet limit bend hybrid forming method of claim 1, wherein, The first bending angle is 120-135°, and the second bending angle is 90°.

4. The ultra-high strength sheet limit bend hybrid forming method of claim 1, wherein, Before the whole plate heat-treated ultra-high strength plate material is divided into workpiece units, the whole plate heat-treated ultra-high strength plate material is subjected to sand blasting and correction.

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