Research On The Forming Limit And Spring-back Of Ultra High Strength Steel(Docoll200M) With Warm Bending

Because of its high strength and low plasticity of high strength steel, makes it’s noteasy forming at room temperature and the forming force is large and easy to crack,resulting in excessive spring-back. While the hot forming technology had overcome theshortcomings of the processing difficulties, there were still more serious surface oxidationproduct and surface quality is difficult to control. This subject present the warm formingprocess of ultra high strength steel according to the warm forming of light alloy materials,and combined finite element simulation and physical experiments to research warmbending limit and spring back angle of the ultra-high strength steel Docol1200M.The stress-strain curves and other mechanical performance parameters were tested inthe warm forming range (100-500℃) with the hot tensile test machine before the maincontents, which provide the precise parameters for the later finite element simulation, andthen to concrete research the two aspects of the warm forming of the material.Researchingthe bending limit of the ultra high strength steel Docol1200M with three ways, thenumerical simulation were mainly used to study the warm bending, looking for materialwhether get the bending limit according to the forming limit criterion we found; andcombined the bending limit theoretical formulas and physics experiments to study it. Theforming process influences on bending limit were obtained to comprise these threemethods.In the respect of spring back, through the numerical simulation combined theorthogonal experiment to study temperature, the bending angle, the bending radius to affectthe spring back angle, also study the influence law and causes of V-shape bending. Thenalso studied the influence of temperature and bending radius on U-shape bending. Thesame contents with numerical simulation were done with physics experiments. The warmforming bending spring back laws of ultra high strength steel Docol1200M were gotten bycomparing the simulation results physical experiments results.Study concluded that: the warm forming temperature of ultra high strength steelDocol1200M should not exceed400℃(avoid the blue brittle region300℃)from themechanical properties.The bending limit of the material has improved greatly with theincreasing temperature, and the finite element simulation result and the theoretical formularesult were close to the experimental values, the reliability of use them to research thebending limit is high.In the spring back aspects of V-shape bending, temperature, bendingradius and bending angle in turn increases the influence, the width of the sheet is not obvious.The spring back angle decreased with the increasing temperature; increased withthe increasing bending radius,; decreased with the increasing of bending angle. The springback angle.of U-shape bending decreased with the increasing temperature and increasedwith the increasing bending radius too.Studies have shown that: the warm forming process of ultra-high strength steelDocol1200M of this article can improve the bending limit and reduce the spring back angleto a certain extent, and the study results can guide the theoretical studies and follow-upresearch of the warm forming with ultra high strength steel Docol1200M.