无磁钻铤用0Cr19Mn21Ni2N高氮钢的高温塑性变形行为

采用Gleeble-2000热模拟试验机对无磁钻铤用0Cr19Mn21Ni2N高氮奥氏体不锈钢进行高温拉伸试验,用扫描电镜和能谱仪对拉伸试样断口及断口附近的组织进行分析,用Thermo-Calc软件计算试验钢的相变及析出相,研究了0Cr19Mn21Ni2N高氮奥氏体不锈钢的高温塑性变形行为。结果表明,试验钢的第Ⅰ脆性区＞1150 ℃,第Ⅲ脆性区为800~950 ℃,未出现第Ⅱ脆性区。第Ⅰ脆性区的出现主要是在加热过程中试验钢由奥氏体向δ铁素体转变引起的,第Ⅲ脆性区的出现是因为M₂(C, N)析出相及Al₂O₃夹杂物引起的。试验钢的高温抗拉强度随温度升高而逐渐降低,断面收缩率在1000~1150 ℃温度范围内表现出极佳的热塑性,温度超过1150 ℃后断面收缩率逐渐下降,因此0Cr19Mn21Ni2N高氮奥氏体不锈钢的热锻温度应选择在1000~1150 ℃之间,在此温度范围内断面收缩率均在73%以上,并且可以避开第Ⅰ与第Ⅲ脆性区。

High temperature plastic deformation behavior of 0Cr19Mn21Ni2N high nitrogen steel for non-magnetic drilling collar

High temperature tensile test of 0Cr19Mn21Ni2N high nitrogen austenitic stainless steel for non-magnetic drilling collar was conducted by using Gleeble-2000 thermal simulation testing machine, the tensile fracture and the microstructure nearby the fracture were analyzed by means of SEM and EDS, the phase transformation and precipitated phases were calculated by using Thermo-Calc software, and then the high temperature plastic deformation behavior of the steel was studied. The results show that the brittle zone I of the tested steel is higher than 1150 ℃ and brittle zone III is in the range of 800-950 ℃, and the brittle zone II is not observed. The appearance of the brittle zone I is mainly caused by the transformation of the tested steel from γ to δ ferrite during the heating process. The brittle zone III is caused by M₂(C, N) precipitates and Al₂O₃ inclusions. With the increase of temperature, the high temperature tensile strength of the tested steel gradually decreases. The reduction of area shows excellent thermoplasticity in the range of 1000-1150 ℃ and gradually decreases after the temperature exceeds 1150 ℃. The hot forging temperature of the 0Cr19Mn21Ni2N high nitrogen austenitic stainless steel should be selected between 1000 ℃ and 1150 ℃, the reduction of area in this temperature range is all above 73%, and the brittle zone I and III can be avoided.