Commonly used cold-working forming methods for stainless steel

(1) Cold bending forming
Cold bending is widely used to make components from stainless steel sheets and strips. Punch presses are open single-acting, mechanically or hydraulically driven, with a long and narrow workbench. This machine can only produce straight parts, but skilled tool designers can also use it to produce parts with complex shapes. The length of parts produced by a cold bend press depends on the original type and thickness of the stainless steel as well as the power of the machine and the size of the tools it can install. Some large punch machines, such as the 11-meter-long, standard 900-ton cold-formed punch machine, can produce austenitic stainless steel cold-formed parts with a length of 9 meters and a thickness of 8.0 mm. To minimize scratches on stainless steel, cold bending punch tools are usually made of hot work die steel with a chromium content of 12%, and plastic films can also be used as further protection measures. It is quite economical to use the general mold of a cold-bending punch machine to produce small batches of general parts. However, if a special mold is used to produce parts with special shape requirements, a large batch size is required to reduce the mold processing cost to meet its economy.
(2) Roll forming
The roll forming method uses a set of continuous stands to roll stainless steel into products of complex shapes and is suitable for the production of plates and special-shaped wire rods. The sequence of the rolls is designed according to the principle of gradually deforming the product. The rolling mill adopts automatic control, and the roll shape of each stand can be gradually and continuously rolled until the required final product shape is obtained. If the shape of the part is complex, up to thirty-six racks can be used, but for parts with simple shapes, three or four racks will suffice. Rolls are often made of cold work die steel, and the hardness is generally above HRC62. At the same time, to ensure the smoothness of the workpiece surface after rolling, the requirements for the smoothness of the roll surface are also very high. It is most economical to produce large quantities of long parts using roll-forming technology. For conventional plate rolling mills, the width range of strip steel that can be processed is 2.5 mm ~ 1500 mm, and the thickness is 0.25 mm ~ 3.5 mm; for conventional wire rod rolling mills, the width range of wire rods that can be processed is 1 mm ~ 30 mm, and the thickness is 0.25 mm ~ 3.5 mm. It is 0.5mm～10mm. Parts produced using roll-forming methods come in a variety of shapes, ranging from simple flat surfaces to complex, closed cross-sections. Generally speaking, due to the high cost of cutting tools, mold processing, and equipment, it is only economical to use the roll forming process when the monthly output of stainless steel plates is more than 30,000 meters, and the monthly output of stainless steel wire rods must reach more than 1,000T. Whether it is roll production of plates or wire rods, the surface of the raw materials must be guaranteed to be smooth, and the mold surface must be checked regularly to prevent surface contamination and scratches. The equipment also needs to be able to withstand cold work hardening of stainless steel and have a high rebound margin. Ability.
(3) Stamping forming
This technology uses punches and molds to produce the required product shape. Domestic stainless steel stamping production is common in stainless steel kitchenware manufacturers. Stainless steel pots and basins need deep stamping, and the handles of kitchenware also need to be stamped, bent and flattened. The punch can be mechanically driven or hydraulically driven, but it is best to use hydraulically driven when deep drawing because the hydraulic punch can provide full load pressure throughout the entire stroke. Most traditional technologies can be used for stamping stainless steel, but because the force required to stamp stainless steel is more than 60% greater than that required to stamp mild steel, the frame of the punch machine should be able to withstand such a large impact force. Moreover, it is also critical to solve the scratch problem, especially the scratches on the surface of the workpiece caused by the high friction and high temperature when stamping stainless steel. Commonly used soaps or emulsions are not effective. Special stamping lubricants or lubricants containing ultra-high pressure additives should be used. However, because such ultra-high pressure additives will cause corrosion to the stainless steel surface, the workpiece should be removed after stamping. Oil stains on the surface. Due to the high processing cost of stamping molds, stamping forming technology is only used in mass production.
(4) Rubber gasket molding
The use of rubber gasket molding technology can greatly reduce mold processing costs and can be used to produce small batches of products. The molding mechanism used in this technology is made of inexpensive materials, such as hardwood or reinforced epoxy resin for the male mold and rubber pads for the female mold. The rubber can be a solid rubber block or a layered rubber block, and its depth is about 30% higher than that of the forming mechanism. When the forming mechanism is closed, the rubber block extrudes the stainless steel blank. When the forming machine is lifted, the rubber pad recovers and the rubber pad can be used repeatedly. The process characteristics of rubber gasket molding determine that it cannot be used to produce products with complex shapes, and the maximum depth of the parts produced is also limited. This process is usually used to produce small batches of stainless steel parts with a thickness of less than 1.5mm.
(6) Folding and forming
As a simple bending machine, the folding machine can be either manual or motorized. The simplest method is to use a model with a bending radius to firmly fix the steel plate on the machine tool worktable, and place the protruding part of the material on another worktable that can rotate along the center of the bending radius. As the movable table rises, it bends the stainless steel to the desired angle, and it is obvious that the stainless steel slides on the table as the bending occurs. Therefore, to prevent scratches on stainless steel, the surface of the workbench must be smooth. In the actual processing process, a plastic film is usually used to protect the stainless steel surface. The upper beam is usually wedge-shaped to create a gap so that a suitably shaped blank can be hemmed into a quadrilateral box or trough. Folding machines were once used to produce large-sized stainless steel sheet products with simple shapes, but these products are now mostly produced with cold-bending punches.
(7) Barrel molding
The plate bending method is usually used to produce cylinders or cylinder sections made of thin plates for various purposes. A traditional plate rolling machine has a pair of adjustable rollers that can be adjusted according to the thickness of the steel plate, and the third roller, the bending roller, controls the diameter of the forming cylinder. There is also a variation of this machine that also uses three rollers in a pagoda-shaped configuration. The bottom roller is a driving roller, and the top roller rotates through the friction generated between the top roller and the workpiece. The diameter of the bottom roller is usually half the diameter of the top roller. The minimum diameter of the cylinder produced by the above two types of equipment is the diameter of the top roller plus 50mm. The maximum diameter of the cylinder produced depends on the size of the incoming material, the rigidity of the machine, and the molded parts. In special cases, an external bracket is required. to support the cylinder.