论文部分内容阅读
通过对间断端淬钢棒显微组织的观察,研究了AISI4340,9840、86840、4140和5140钢的冷却转变。已发现,当马氏体在冷却中形成时便立即回火,而且这种回火通常引起软化。缓冷可推迟马氏体反应的开始。先共析铁素体的形成也会推迟马氏体反应,因为先共析铁素体会引起相当数量的奥氏体保留在4140钢中。先共析铁素体的形成也会推迟贝茵体反应。在大多数情况下冷却时,贝茵氏形成之前先转变为类似于贝茵体形状但无可见碳化物颗粒的针状组织。在宽广的冷却速度范围内,针状组织开始形成的温度是一常数。在快速冷却下4340钢中不会形成这种组织。而且此时针状组织被所形成的第一个转变产物——贝茵体所取代。(ASM—SLA类:N8、Ay)。
The cooling transformation of AISI 4340, 9840, 86840, 4140 and 5140 steels was studied by observing the microstructure of discontinuous quenched steel bars. It has been found that when martensite is formed upon cooling, it is tempered immediately, and this tempering usually causes softening. Slow cooling can delay the beginning of the martensite reaction. The formation of pro-eutectoid ferrite can also delay the martensitic reaction, as pro-eutectoid ferrite can cause a significant amount of austenite to remain in 4140 steel. The formation of pro-eutectoid ferrite will also delay the bivalve reaction. In most cases, when cooled, the bainite was first transformed into acicular tissue similar to bainite without visible carbide particles. The temperature at which acicular tissue begins to form is a constant over a wide range of cooling rates. In the rapid cooling 4340 steel will not form this organization. And at this time acicular tissue is formed by the first transformation product - birch body replaced. (ASM-SLA category: N8, Ay).