TMCP工艺对X100管线钢M/A岛的影响

Effect of TMCP(Thermo-mechanical Control Process)on M/A Islands of X100 Pipeline Steel

M/A岛是X100管线钢典型组织,对钢的强韧性有着重要的影响。利用热模拟和显微分析技术研究了冷却速度、变形量和等温温度对X100管线钢中M/A岛的影响规律。结果表明:随着冷速增加,M/A岛体积分数和平均尺寸都减小,由在晶界处分布的较大块状向板条间隙弥散分布的细小片层状转变;随着变形量增加,M/A岛体积分数先增加,变形量为40%达到最大,变形量达到50%时,M/A岛体积分数降低;快冷后随着等温温度升高,M/A岛平均尺寸增大,等温温度为450℃时体积分数最大,温度继续升高体积分数减小。观察到M/A岛形貌多呈棱角状、链条状、片条状和针状,分布在晶界和基体内,岛内精细结构观察到微孪晶马氏体。

M/A islands（martensite-austenite islands） is a typical microstructure of XIO0 pipeline steel, which has an important influence on the strength and toughness of steel. The effect of cooling rate, deformation amount and isothermal temperature on M/A islands of X100 pipeline steel were studied by using analysis technique of heat simulation and microstructure. The results show that, with the increasement of the cooling rate, the volume fraction and average size of M/A islands were decreased, from the large block which distributed in grain boundaries to the small layer which distributed dispersively in lath gap; with the growth of the deformation amount, the volume fraction of M/A islands increased firstly,when the deformation up to 40~, the volume fraction was maximal;when the deforma- tion up to 50%, the volume fraction was decreased; after fast cooling, with the increasement of isothermal temperature, the average size of M/A islands was increased, when the isothermal temperature up to 4：50℃, the volume fraction was maximal,with isothermal temperature rising and volume fraction decreasing continuely. The morphology of M/A islands often presented as angular, chain, sublath and acicular shapes, distributed in grain boundaries and matrix, and micro-twin martensite distributed in the fine structure of islands.