论文部分内容阅读
制造无缝钢管用的抗蠕变21/4Cr—Mo钢,用碱性电弧炉冶炼,锻成30毫米的元棒,并在空气中冷却.在这种条件下所得组织是具有少量铁素体晶粒的贝氏体(见照片1)。连续冷却转变曲线见图1。珠光体转变,尤其是共析物转变比贝氏体反应速度慢,这就是从奥氏体温度下空冷不形成珠光体而形成含(先析出的)铁索体或不含(先析出的)铁索体的贝氏体的理由。只有在非常慢的冷却速度(16小时下降到500℃)下才能完全转变成珠光体(见照片5)。这类钢的Ac_1是780℃,Ac_3是870℃,Ms是465℃,上临界冷却速度Km是0.7秒(870℃到500℃)。
Creep resistant 21 / 4Cr-Mo steels for seamless steel tubes were produced, smelted in a basic electric arc furnace, forged into 30 mm rods and air cooled, resulting in a microstructure with a small amount of ferrite Grain bainite (see photo 1). Continuous cooling transition curve shown in Figure 1. The pearlite transformation, especially the eutectoid transformation, is slower than the bainite reaction, which is the formation of a (pre-precipitated) ferrite body without or with (pre-precipitated) ferrite without forming pearlite from the austenite temperature Reason for bainite body. Only a very slow cooling rate (16 hours down to 500 ℃) can be completely converted to pearlite (see photo 5). Ac_1 of such steels is 780 ° C, Ac_3 is 870 ° C, Ms is 465 ° C, and upper critical cooling rate Km is 0.7 seconds (870 ° C to 500 ° C).