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利用PCY热膨胀仪(热膨胀系数仪),以2℃/min的加热/冷却速率,测定了含Nb微合金钢Q345B,Q345C和管线钢X70的临界点温度Ac1,Ac3,Ar1和Ar3,并依据膨胀曲线图计算出它们的热膨胀系数。试验结果表明,对Q345B和Q345C进行加热时,它们的临界点Ac1和Ac3大致相同,分别相差8℃和3℃;而冷却时的临界点Ar1和Ar3,分别相差23℃和25℃。由于在X70钢中,含有更多的微合金元素Nb,V,Ti等,它们的碳氮化物的溶解和析出会对钢材的相变带来较大的影响,所以X70钢的各个临界点温度比Q345B和Q345C高出许多。但所测试的3个钢种的热膨胀系数没有太大的差别。
The critical temperatures Ac1, Ac3, Ar1 and Ar3 of the Nb microalloyed steel Q345B, Q345C and the pipeline steel X70 were measured with a PCY thermal expander (CTE) at a heating / cooling rate of 2 ° C / min, The graph calculates their thermal expansion coefficient. The experimental results show that the critical points Ac1 and Ac3 of Q345B and Q345C are about the same, which differ by 8 ℃ and 3 ℃, respectively; while the critical points Ar1 and Ar3 of cooling are different by 23 ℃ and 25 ℃ respectively. Because X70 steel containing more microalloying elements Nb, V, Ti, etc., their carbonitride dissolution and precipitation will have a greater impact on the phase transition of steel, so the X70 steel each critical point temperature Much higher than the Q345B and Q345C. However, the thermal expansion coefficients of the three steels tested did not differ much.