铸造C12A耐热钢的焊接及组织与性能的研究

The Study of Welding and Microstructure and Cast C12A Heat Resistant Steel

本文对铸造C12A高强耐热钢进行了组织与性能、可焊性、焊缝组织变化厦性能特点等方面进行了研究分析。试验结果表明：淬火组织为板务马氏体＋部分针状马氏体＋少量残余奥氏体，其硬度比较高，塑性和韧性不是很好；淬火＋回火组织为保留马氏体形态的回火索氏体，其硬度不是很高，塑性和韧性比较好，具有盘好的综合性能；退火组织为铁素体，其硬度低，塑性和韧性高；焊接后的全相组织中，没有焊接裂纹等焊接缺陷存在，具有良好可焊性。对于淬火＋回火后的铸造C12A耐热钢，经过焊接，基体组织和性能没有明显发生变化，过渡区的金相组织为板条马氏体＋奥氏体组织，其硬度有所降低；熔化区的金相组织为针状马氏体＋奥氏体＋板条马氏体，硬度很高；焊后经过回火处理的基体佥相组织与性能没有变化。过度区的金相组织为保留板条马氏体形态的回火索氏体组织，较基体组织要粗大，其硬度要比基体有所下降；熔化区的金相组织转变为保留板每马氏体的回火索氏体，但组织较为基体组织要细小，其性能表现为硬度要比基体的有所升高。铸造C12A焊接后再经回火处理，可使焊接后的组织差别消除；性能变化趋于平缓，有利于材料的使用。

The studies of microstructure and properties, weldability, wehting microstructure of cast CI2A and its properties were carried out. The results show that the quenched microstructure is composed of blocky martensite and partly needle martensite and little residual autensite. Its hardness is high and plasticity and toughness are not good. The microstructure of quenched and tempered cast C12A is the sorbite with the former martensitic morphology, which hardness is not too high and plasticity and toughness are good, so it has good comprehensive properties. The annealed microstructure is ferrite with low hardness and high plasticity and toughness. There is no defects, such as welding cracking, existed in the welded microstructure. Its weldability is very good. After welding, the microstructure and properties of the matrix of quenched and annealed cast C12A are not obviously changed. The microstructure of heat affected zone is blocky martensite and austenite and its hardness is decreased slightly. The microstructure of the melt zone is composed of needle martensite, austesite and blocky martcnsite with high hardness. The matrix and properties of the tempered weld microstructure has no change. The microstructure of heat affected zone after tempering is sorbite maintained blocky martensite and is bigger than that of matrix. , and its hardness is decreased slightly. The microstructure of melt zone changes to the tempering sorbite maintained blocky martensite with fine matrix microstructure, and its hardness is slightly increased compared with that of the matrix. After tempering of welded cast C12A, the difference of welded micrustructure is vanished and its properties are tended to the same, resulting in a increase in application.