Study on bending and springback of DP800 two-phase high strength wear-resisting plate
With the continuous development of science and technology, the lightweight of construction machinery and automobiles has become an effective way to reduce exhaust emissions and fuel consumption, and lightweight design has gradually become the mainstream direction of product design and manufacturing. Advanced high-strength wear-resistant plates represented by dual-phase steel (DP), phase-change induced plastic steel (TRIP0) and low-carbon martensitic steel (MART) ensure the strength of structural parts at the same time, reduce the thickness of parts, play a role in lightweight and improve safety performance, and are currently the most popular lightweight materials.
DP800 belongs to the dual-phase high-strength wear plate composed of martensite and ferrite. With the increase of martensite content, its strength value can reach 1200MPa, which is used to make parts with high structural strength requirements. DP800 has a low yield strength ratio, high work hardening index and bake hardening performance without yield elongation and room temperature aging. High strength steel plate in the forming process will produce more elastic recovery and stress release, will lead to the parts have a tendency to return to the original state, causing rebound. Springback reduces the dimensional accuracy of parts and increases the difficulty of subsequent parts assembly. It should be strictly controlled and reduced in the actual production process.
At present, there are few studies on the optimization of process parameters in the forming and springback process of high-strength wear-resistant steel plates. Based on dynaform, researchers from the School of Materials, Hefei University of Technology studied the effects of friction factor, die clearance, stamping speed and die radius on the forming and springback of V-shaped parts, and optimized and analyzed the process parameters. Finally, the combination of forming process parameters to minimize the rebound Angle is obtained, which provides guidance for practical experiments.
The forming and springback of high strength wear-resistant plate is a process of multi-factors, so it is necessary to make a comprehensive analysis of the multi-factors and study the influence of multi-parameters on the forming and springback. Researchers based on the orthogonal test method, four factors and three levels of the friction factor, die clearance, stamping speed, die radius 4 process variables were designed for qualitative and quantitative analysis of the above factors on the forming and springback of V-shaped parts. The conclusions are as follows:
(1) Based on V-shaped bending simulation experiment, the bending forming and springback problems of high-strength steel DP800 were studied. Through orthogonal experimental design, the influence law of multiple process parameters on forming and springback was analyzed. The results showed that the process parameters had little influence on the maximum thinning rate of V-shaped parts after bending and had a greater influence on springback.
(2) Friction factor and mold clearance have a great influence on the rebound of V-shaped parts after bending: The rebound value decreases with the increase of friction factor. During the forming process of V-shaped parts, compressive stress and tensile stress are generated on the surface of the plate respectively. Due to the friction between the die and the plate, the tensile stress deformation zone can be increased, so that the stress state of the inner and outer surfaces of the plate tends to be consistent. However, when the friction is large, the tensile stress generated is also large, which will affect the surface quality of the heat insulation board, and the phenomenon of tensile cracking occurs in serious cases. The springback value increases with the increase of die clearance, because the smaller the gap between the bump and die, the larger the strain value generated during the forming process, which can effectively reduce the influence of elastic deformation, and thus reduce the springback after unloading. The rebound value increases with the increase of the radius of die fillet. The impact of stamping speed on the springback of V-shaped parts is small, and the effect of stamping speed on the springback can be ignored in actual production.
