Stamping process can be roughly divided into separation process and forming process (also divided into bending, deep drawing, forming) two categories. Separation process is to separate stamping parts and blanks along a certain contour line in the stamping process, while the quality of the separated section of stamping parts must meet certain requirements; forming process is to make the blanks plastic deformation without destroying, and transform into the required finished product shape, but also to meet the requirements of dimension tolerance. What factors will affect the quality of stamping parts are briefly introduced below by Baida Borun Petrochemical Company.
I. Impact of Stamping Technology on Workpiece Quality
According to the temperature of stamping, there are two ways: cold stamping and hot stamping. This depends on the strength, plasticity, thickness, degree of deformation and equipment capacity of the material, and the original heat treatment state and final service conditions of the material should be taken into account.
(1) Cold stamping metal processing at room temperature is generally suitable for blanks with thickness less than 4 mm. The utility model has the advantages of no heating, no oxide skin, good surface quality, convenient operation and low cost. The disadvantage is work hardening, which makes the metal lose the ability of further deformation. Cold stamping requires uniform blank thickness and small fluctuation range, smooth surface, no spot, no scratch and so on.
(2) Hot stamping is a kind of stamping method which heats metal to a certain temperature range. The advantages are that internal stress can be eliminated, work hardening can be avoided, plasticity of materials can be increased, deformation resistance can be reduced and power consumption of equipment can be reduced.
2. The Effect of Stamping Material on Workpiece Quality
There are three main stamping processes: blanking, bending and stretching. Different processes have different requirements for sheet metal. The selection of sheet metal should also be considered according to the general shape of the product and the processing technology.
(1) The influence of material on blanking
Blanking requires that the sheet should have enough plasticity to ensure that the sheet does not crack during blanking. Soft materials can be blanked to obtain smooth cross-section and small inclination of the parts; hard materials have large cross-section roughness after blanking, especially for thick sheet materials, which are especially serious brittle materials, and tear easily occurs after blanking.
(2) The influence of material on bending
The sheet which needs bending forming should have enough plasticity and lower yield limit. Plates with high plasticity are not easy to crack when bending; sheets with lower yield limit and lower elastic modulus have smaller springback deformation after bending, and are easy to get accurate bending shape. The material with larger brittleness must have larger relative bending radius when bending, otherwise it is easy to crack in the bending process.
(3) Effect of Material on Tensile Processing
The drawing process of sheet metal requires not only the drawing depth as small as possible, the shape as simple as possible and smooth transition, but also the material has better plasticity. Otherwise, it is very easy to cause the whole distortion, local wrinkling and even the tension part cracking.
3. Impact of Stamping Oil Products on Workpiece Quality
Stamping oil plays a key role in the stamping process. Good cooling performance and extreme pressure and anti-wear performance have made a qualitative leap in improving the service life of the die and the accuracy of the workpiece. According to the different material of the workpiece, the emphasis of the performance of stamping oil is also different when it is used.
(1) Silicon steel sheet is a relatively easy punching material. In order to clean the workpiece, low-viscosity punching oil will be selected on the premise of preventing punching burr.
(2) When choosing punching oil for carbon steel sheet, the better viscosity should be determined according to the difficulty of process and the method of drawing oil and degreasing.
(3) Galvanized steel sheet and chlorine additives will react chemically, so when choosing stamping oil for galvanized steel sheet, attention should be paid to the possibility of white rust in chlorine stamping oil, while using Yida Borun sulfur stamping oil can avoid rust, but degreasing should be done as soon as possible after stamping.
(4) Stainless steel sheets are easy to harden. It is required to use oil film with high strength and sintering resistance. Pressing oil containing sulfur-chlorine compound additives is generally used to ensure extreme pressure performance and avoid burrs and cracks on the workpiece.
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