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

摘要： 利用Gleeble热模拟试验机，完成了同炉冶炼的S30432钢连铸和模铸工艺生产的管坯在高温下的拉伸热变形过程，设置了1 000、1 050、1 100、1 150 ℃系列温度和0.1、1、5 s-1应变速率的不同热模拟试验条件，获得了同炉冶炼的S30432钢连铸和模铸工艺生产的管坯在各个高温拉伸条件下的高温应力-应变曲线，并对其进行修正和拟合，使其尽可能符合实际试验情况。对同炉冶炼的S30432钢连铸管坯和模铸管坯的热变形本构方程进行了拟合，并对2种工艺管坯的高温热塑性差异进行对比分析。结果表明，连铸管坯和模铸管坯的热塑性在不同拉伸温度和速率下表现出一定规律性，连铸管坯的热塑性存在较大的波动，且整体上略逊于模铸管坯，为改进优化管坯的穿孔工艺提供了参考。通过扫描电镜对高温拉伸断口的微观组织结构进行表征，发现高温拉伸失效形式为塑性断裂，绝大部分断口形貌属于韧窝断口。然而，在特定条件下，部分连铸管坯试样表现出较差的热塑性，其断裂形式转变为脆性断裂。对于S30432钢连铸管坯的高温塑性加工，建议使用较高的应变速率和较高的应变温度以获得良好的加工性能。

关键词: S30432钢, 连铸, 模铸, 高温拉伸, 变形本构方程