预硬型贝氏体钢中合金元素的作用

Roles of alloying elements in pre hardened Bainitic steel

研究了新型预硬型贝氏体钢（Ｙ８２）的合金设计及性能，分析了合金元素Ｓｉ， Ｓ， Ｃａ 的作用。结果表明： 新型预硬型贝氏体钢（Ｙ８２）成分简单，价格低廉，空冷淬透性好； 合金元素Ｓｉ改变了奥氏体连续冷却转变曲线（ＣＣＴ）的位置，使ＣＣＴ曲线中贝氏体转变区向右下方移动。使贝氏体转变发生在较低的温度，可以形成细小的针状下贝氏体，从而提高了钢的机械性能； 合金元素Ｓ提高了钢的易切削性，元素Ｃａ 对夹杂物有变质作用，使钢中ＭｎＳ形成一种特殊的形态，因而使Ｙ８２ 在预硬状态时（硬度约为３５～４０ ＨＲＣ）仍具有良好的切削加工性能。

Alloying design, properties of pre hardened Bainitic steel (Y82) and the function of alloying elements such as Si, S, Ca were studied. Bainite/Martensite duplex structure can be obtained during air cooling in Y82. It has advantages of lower costs, simple processing, and high hardenability. The position of continuous cooling transformation diagram (CCT) curve is changed by Si, and Bainite transformation zone shifts to lower right so that Lower Bainite becomes finer due to forming at lower temperature, and mechanical properties of the steel are improved with the adding of silicon. The roles of sulfur and calcium were investigated, the shape of inclusions can be controlled by calcium, and a special shape of MnS was formed, thus the machinabality is improved.