Cars use high-strength wear-resistant plates. Because of their higher strength, the plate thickness can be reduced to make the car structure lighter. At the same time, the car's dent resistance, wear resistance and large deformation impact strength and safety are improved, and the cost is lower than that of lighter metals. . The advantages of high-strength wear-resistant plates have led to their rapid development and wide application in the automotive industry, helping to achieve the unification of vehicle lightweighting and safety. However, the forming range of high-strength wear-resistant plates is narrow, and problems encountered during the forming process are more difficult to solve than traditional steel. Therefore, advanced processing methods must be adopted based on the characteristics of high-strength wear-resistant plates. The forming technology of high-strength wear-resistant plates mainly includes cold stamping, hot forming, hydroforming, etc.
1. Cold stamping technology
The cold stamping forming technology of high-strength wear-resistant plates is similar to that of traditional steel cold stamping. However, the forming range of high-strength wear-resistant plates is limited, and springback is prone to occur after forming, and the amount of springback is much greater than that of ordinary low-carbon steel stamping-formed parts. The amount of spring brings great difficulties to the prediction and control of springback. At the same time, high-strength steel faces problems such as wrinkling and cracking of formed parts during application. These problems all lead to poor dimensional and shape accuracy during forming of high-strength wear-resistant plates. Japan's NKK Co., Ltd. has developed a new steel plate easy stamping technology to solve the problem of cracking during the stamping process of high-strength wear-resistant plates. This technology injects lubricating oil from the openings in the mold to create a number of connections between the steel plate and the mold. The gap of ten microns prevents the problem of steel plate cracking during the stamping process, and this method can be realized with slight modifications on ordinary stamping machines.
2. Hot stamping technology
When the strength of the wear-resistant plate exceeds 1000MPa, some parts with complex shapes are difficult to form using the conventional cold stamping process. Even if the cold stamping process can be used, there are still problems such as high stamping force required, easy cracking of molded parts, and large rebound. Therefore, Thermoforming technology came into being. Hot stamping technology is to heat the boron steel plate (initial strength is 500~600MPa) to the austenitized state, and quickly transfer it to the mold for high-speed stamping forming. Under the condition of ensuring a certain pressure, the parts are formed in the mold body at a temperature greater than Quenching treatment is performed at a cooling rate of 27°C/s, and the pressure is maintained for a period of time to obtain a uniform martensite structure while the parts are being formed. High-strength steel hot stamping technology divides forming and strengthening into two steps to solve the contradiction between the strength and plasticity of high-strength steel. Its main advantages are: small deformation resistance, good plasticity, high forming limit, and good stamping formability; easy rebound control, high dimensional accuracy of formed parts; reduced tonnage requirements of stamping machines; low steel forming resistance, small unit pressure of the mold; formed parts Short production cycle, etc. However, hot stamping technology also has some shortcomings, such as large equipment investment, complex mold design and processing, and high maintenance and upkeep costs.
3. Hydroforming Technology
Hydroforming technology is a plastic processing technology that relies on high-pressure liquid (water or oil) as a force transmission medium to shape the workpiece. During the hydroforming process, the plate is formed by fitting the male or female mold through the pressure of the force-transmitting medium, which is a flexible processing technology. Hydroformed parts are mainly pipes, plates and shells. The required medium pressure is generally above 400MPa. The main advantages of using hydroforming technology are: hollow components with changes along the component axis and cross-section can be formed in one go; mold costs are reduced; the precision of formed parts is improved and springback is reduced; components that originally required the combination of multiple parts can be modified Replaced by a single part, while increasing the rigidity of the car body, which is beneficial to reducing mass.
