The aim of the present work was to investigate the combined effect of prior austenitic grain size and the tempering temperature on the energy absorption characteristics of low alloy quenched and tempered steel. High frequency (HF) electric resistance welded tubes made of Boron added low carbon steels were used for the study. Induction hardening at two different temperatures (above upper critical temperature) led to two different prior austenitic grain sizes 20 µm and 100 µm. Both the set of samples were subjected to conventional tempering at different temperatures and it resulted in variation in the distribution and morphology of the carbides. Microstructural evolution at each tempering temperature, carbide morphology and distribution of carbides was investigated using SEM. Low temperature tempering leads to precipitation of rod like carbides and with increase in tempering temperature the carbide morphology turns spherical followed by carbide coarsening at higher temperatures. Three point bend test of the tempered samples was carried out using Schimadzu Universal testing machine to determine the energy absorption characteristics. Test results indicate that optimum combination of high energy absorption and better mechanical properties was delivered by tempered martensite with fine spherical carbides and fine prior austenitic grain size. Thus the work established the correlation between energy absorption; prior austenitic grain size and tempering temperature in low alloy quenched and tempered steel.

本工作的目的是研究先验奥氏体晶粒度和回火温度对低合金调质钢能量吸收特性的综合影响。该研究使用了由添加了硼的低碳钢制成的高频（HF）电阻焊管。在两个不同的温度（高于上临界温度）下的感应淬火导致了两个不同的先有奥氏体晶粒尺寸20 µm和100 µm。两组样品均在不同温度下进行常规回火，这导致碳化物的分布和形态发生变化。使用SEM研究了在每个回火温度下的显微组织演变，碳化物形态和碳化物的分布。低温回火导致棒状碳化物析出，并且随着回火温度的升高，碳化物形态变为球形，随后在较高温度下碳化物粗化。使用Schimadzu Universal试验机对回火样品进行三点弯曲试验，以确定其能量吸收特性。测试结果表明，回火马氏体具有良好的球形碳化物和较细的先前奥氏体晶粒尺寸，可以实现高能量吸收和更好的机械性能的最佳组合。因此，工作建立了能量吸收之间的相关性。低合金调质钢的先验奥氏体晶粒度和回火温度。