超导磁体热处理对N50H不锈钢铠甲力学性能的影响

Effect of superconducting magnet heat treatment on mechanical properties of N50H stainless steel jacket

目前,低温超导体(LTS)中应用最成熟的是铌三锡(Nb_(3)Sn)超导体,高温超导体(HTS)中钇钡铜氧(YBCO)超导体因其优异的性能,且不需要热处理成为中国聚变工程试验堆(CFETR)中超导线圈的候选材料。而316L、316LN、JK2LB等铠甲材料低温下的力学性能不满足未来超导磁体的使用要求。因此,以N50H奥氏体不锈钢为研究对象,对冷加工样品热处理后的力学性能进行测试,探究热处理工艺对N50H不锈钢力学性能的影响。结果表明,在4.2 K下,热处理前的N50H不锈钢试样抗拉强度为1800 MPa左右,屈服强度在1500 MPa以上。经两种Nb_(3)Sn热处理制度后N50H不锈钢试样的抗拉强度均远大于1800 MPa,屈服强度较未热处理略有提高。同时,断后伸长率在两种热处理制度后均高于25%,对比未热处理时的变化幅度最大为5%左右。验证了N50H不锈钢未来作为YBCO和Nb_(3)Sn CICC铠甲材料应用的可行性。

At present,the most mature low-temperature superconductor(LTS)is the Nb_(3)Sn superconductor,and YBCO in high-temperature superconductor(HTS)has become a candidate material for superconducting coils in China Fusion Engineering Test Reactor(CFETR)because of its excellent properties and no need for heat treatment.However,the mechanical properties of 316L,316LN,JK2LB and other jacket materials do not meet the requirements of future superconducting magnets at low temperatures.Therefore,taking N50H austenitic stainless steel as the research object,the mechanical properties of the cold-worked specimens after heat treatment were tested to explore the effect of heat treatment on the mechanical properties of the N50H stainless steel.The results show that before heat treatment,the tensile strength of the N50H stainless steel is about 1800 MPa and the yield strength is above 1500 MPa at 4.2 K.After the two Nb_(3)Sn heat treatments,the tensile strength of the N50H stainless steel increases to more than 1800 MPa,and the yield strength is slightly higher than that without heat treatment.At the same time,the elongation is higher than 25%after both heat treatments and the maximum change is 5%compared with that without heat treatment.These further verifie the feasibility of the N5OH stainless steel as YBCO and Nb_(3)Sn CICC jacket material in the future.