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硅作为低碳贝氏体钢中的一种主要合金元素,在一定含量范围内可有效地提高钢中残留奥氏体量及其热稳定性和机械稳定性,从而使钢的强韧性得到改善。本文试验表明,随着硅含量增加,低碳贝氏体钢的强度和韧性呈先增加后降低的规律变化,在某一硅含量下强度和韧性同时达到最大。在冷却速度Vt=156℃/min时强度和韧性都达到最大的硅含量为1.62%;在Vt=7.5℃/min和0.9℃/min时硅含量为1.99%。由于硅含量和冷却速度不同,在低碳贝氏体钢中存在四类不同形态的M-A岛:第一类为全马氏体岛;第二类为全残留奥氏体岛;第三类为中心是马氏体外围是残留奥氏体的岛;第四类是外围是马氏体中心是残留奥氏体的岛。其中第二、三类M-A岛有利于提高钢的韧性。
Silicon, as a major alloying element in low-carbon bainitic steels, can effectively increase the amount of retained austenite and its thermal and mechanical stability within a certain range of contents, thereby improving the toughness of the steel . The experimental results show that with the increase of silicon content, the strength and toughness of low-carbon bainitic steel increase first and then decrease, and the strength and toughness reach the maximum at the same time. The silicon content with the highest strength and toughness at cooling rate of Vt = 156 ° C / min was 1.62%, and the silicon content was 1.99% at Vt = 7.5 ° C / min and 0.9 ° C / min. Four kinds of MA islands exist in low-carbon bainitic steels due to the difference in silicon content and cooling rate: the first is all-martensite, the second one is all-retained austenite and the third is Center is the outer martensite is retained austenite island; the fourth is the outer periphery of the martensite is the center of retained austenite island. Among them, the second and third M-A islands are helpful to improve the toughness of steel.