关键词: S30432钢, 连铸, 模铸, 高温拉伸, 变形本构方程

Abstract: The high-temperature tensile thermal deformation processes of continuously cast and mold cast S30432 steel tube billets in same heat were investigated using the Gleeble thermal simulation machine， different thermal simulation conditions were set for temperature series of 1 000， 1 050， 1 100， and 1 150 ℃， and strain rates of 0.1， 1， and 5 s-1.The high-temperature stress-strain curves of continuously cast and mold cast S30432 steel billets from in same heat were obtained for both types of billets under various high-temperature tensile conditions， and these curves were corrected and fitted to align as closely as possible with actual experimental situations. The constitutive equations for the hot deformation of the continuously cast and mold cast S30432 steel billets from the same heat were derived through fitting， and a comparative analysis of the high-temperature hot plasticity differences between the two processing methods was conducted. The results indicated that the hot plasticity of both types of billets exhibited certain regularities at different tensile temperatures and rates， the continuously cast tube billets showed more significant fluctuations in hot plasticity and were slightly inferior to the mold cast tube billets in overall performance， providing insights for improving and optimizing the piercing process of the tube billets. Scanning electron microscopy was employed to characterize the microstructural features of the high-temperature tensile fracture surfaces， it was observed that the predominant fracture mode at high temperatures was ductile rupture， with most fracture surfaces exhibiting dimple features. However， under specific conditions， some samples of continuously cast tube billets exhibited poor hot plasticity and its fracture form was transformed into brittle fracture patterns. For the high-temperature plastic processing of S30432 steel continuously cast tube billets， it is recommended to employ higher strain rates and temperatures to achieve enhanced processing performance.

Key words: S30432 Steel, Continuous Casting, Die Casting, High Temperature Stretching, Deformation Instanton Equation