Effects Of Deformation Parameters On Hot Deformation Behavior Of X70HD High Deformation Pipeline Steel

Because of its economy, safety and continuity, pipeline transportation has receivedextensive attention in the developed countries.The research and production of pipelinesteel had become an important branch of low alloy high strength steel. In the previousstudy, scientists proposed various prediction models for stress. It provided a theoreticalbasis for practical production and finite element simulation, but the former models werethe basic structure of a simple macro deformation model based on material.While themodel of the micro mechanism of materials was rarely involved. In the actual process ofplate production, the strain rate can only reach25s-1. Obviously, this strain rate can notmeet the future needs of production. However, the strain rate’s improving at the same time,the requirements for equipment will be a corresponding increase, So it has an importantsignificance for the quality production efficiency, equipment’s protection and products.Controlled rolling and controlled cooling technology to the production of X70HDhigh deformation pipeline steel can controll the deformation parameters(deformationtempreture,deformation and deformation rate) quantitatively. It can not only make themacro shape and size properties of an ideal, but also make micro grain size andorganizational structure of the steel an ideal.This paper introduces a stress model of microscopic mechanism, and does theexcersie under10s-1~50s-1on Gleeble3500thermo-simulation machine. Therefore, basedon the relationship among the thermal processing, microstructure and performance, amodel for high strain rate was developed. That will provide a feasibility theoretical basisfor the production of thick plate. Metal material can occur dynamic softening (mainlydynamic recrystallization), static softening (mainly static recrystallization andmetadynamic recrystallization) and grain growth. This microstructure (austenite) evolutionhas a great influence of the final performance of the production. The austeniterecrystallization behavior of X70HD high deformation pipeline steel during single-passand double-pass hot compression deformation tests is investigated at different deformationconditions on Gleebe3500thermo-simulation machine. Static softening mechanism duringthe interpass time is researched deeply. Austenite evolution kinetics model is set up.According to analyzing, the intensive study of austenite evolution is proven to moreaccurately, which deepen the understanding of the microstructure evolution to controll therolling process more accurately, thereby enhancing the product’s mechanical properties.