小口径S32750超级双相不锈钢管组织及力学性能调控研究

Research on Microstructure and Mechanical Properties Control of Small Diameter S32750 Super Duplex Stainless Steel Tubes

采用拉伸试验、硬度试验、扫描电镜和金相显微镜观察,探究不同固溶温度对S32750超级双相不锈钢管组织和力学性能的影响。结果表明:固溶温度在1020℃及以下时,S32750双相不锈钢中存在析出相;固溶温度为1060℃时,基体内已观察不到析出相,但是晶界较宽;在固溶温度为1100℃,晶界恢复正常,此时S32750双相不锈钢的综合力学性能较好,抗拉强度和屈服强度分别为906 MPa和610 MPa,伸长率为34%,铁素体和奥氏体两相比例接近1∶1。随着固溶温度的升高,晶粒长大呈现先快再慢后快的趋势,基体中奥氏体逐渐分解、转化为铁素体。温度在980~1140℃,保温5 min,对S32750超级双相不锈钢强度的影响,从大到小的顺序为析出相、铁素体、晶粒尺寸。

Effects of different solid solution temperatures on the microstructure and mechanical properties of S32750 super duplex stainless steel tubes were investigated by means of tensile test,hardness test,scanning electron microscope and metallographic microscope.The results show that,when the solid solution temperature is 1020℃or below,there are precipitated phases in S32750 duplex stainless steel.When the solution temperature is 1060℃,no precipitation phase can be observed in the matrix,but the grain boundaries are wider.When the solution temperature is 1100℃,the grain boundaries return to normal.At this time,the comprehensive mechanical properties of S32750 duplex stainless steel are better.The tensile strength and yield strength are 906 MPa and 610 MPa,respectively,the elongation is 34%,and the ratio of ferrite and austenite is close to 1∶1.With the increase of the solid solution temperature,the grain growth shows a trend of fast first,then slow and fast,and the austenite in the matrix gradually decomposes and transforms into ferrite.The temperature range is 980-1140℃,and the holding time is 5 min,and the influence on the strength of S32750 super duplex stainless steel from large to small is:precipitated phase>ferrite>grain size.