20MnSi螺纹钢的冷却速率──贝氏体量──机械性能间的关系

RELATIONS AMONG COOLING RATE,BAINITE QUANTITIES AND MECHANICAL PROPERTIES OF THE LOW CARBON SCREW-THREAD STEEL

用连续冷却、砂坑堆冷、等温冷却共１５种不同条件对２０ＭｎＳｉ螺纹钢进行轧后模拟冷却试验．测定了不同冷却条件下的冷却速率．用定量金相网格法测定了各种冷却速率下钢中贝氏体数量．并进行了钢的机械性能试验．试验结果表明．快速连续冷却可获得最多的粒状贝氏体（２５％）．６５０℃～５００℃之间的砂坑堆冷可获得较多的粒贝（１８％）。在本实验条件范围内．钢的强度与贝氏体量线性正相关．钢的延伸率与贝氏体量线性负相关．钢均不会发生因粒贝数量过多而引起冷弯和反弯不合格．

After the low carbon screw-thread steel with Mn and St is rolled down,simulating cooling tests are carried out under fifteen kinds of conditions including continuous,sand heaped and isothermal cooling. Then, cooling rates of different conditions are determined. Bainite quantities of the steel subjected to cooling are measured by using method of quantitative metallography. And the mechanical properties of the Steel are measured after cooling too. Experiments show that maximum granular bainite (25%) can be got when the steel subjected to fast continuous cooling,about 18% of granular bainite can be got when the steel subjected to sand heap cooling between 650℃ and 500℃,the strength of the steel is linear positive dependent on bainite quantity and spectific elongation of the steel is linear negative dependent on bainite quantity. It is important that the steel does not crack caused by granular bainite under cold bend reverse bend in our test