Continuous cooling transformation behavior in the weld coarse grained heat affected zone and mechanical properties of Nb-microalloyed and HY85 steels
Continuous cooling transformation behavior in the weld coarse grained heat affected zone and mechanical properties of Nb-microalloyed and HY85 steels
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DOI：
10.1016/j.matdes.2015.10.071
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发表时间：
2016-01-15
影响因子：
8.4
通讯作者：
Kumar, Vinod
中科院分区：
文献类型：
--
作者：
Kumar, Sanjeev;Natha, S. K.;Kumar, Vinod
用Gleeble(R)3800热模拟试验机测定了Nb微合金钢和HY 85钢焊接模拟粗晶热影响区的连续冷却转变图。将试样加热到最高温度1573K(1300℃)，以0.5K/S到120K/S的不同冷却速度冷却，根据模拟的焊接热循环，测定了223K下的组织、硬度和冲击韧性。用膨胀法测定了相变温度A(C3)、A(C1)、B-S、B-f、M-S和M-f。在慢速冷却时，Nb微合金钢中出现先共析铁素体和珠光体，HY-85钢中出现贝氏体铁素体和粒状贝氏体的混合体，但未观察到先共析铁素体。在中等冷却速度下，两种钢中都只观察到贝氏体。在较高的冷却速度下，两种钢均观察到板条马氏体。发现原始奥氏体晶粒度与力学性能有很强的相关性。Nb微合金钢和HY85钢的奥氏体晶粒度约为30µm(80K/S)，其冲击韧性分别大于100J和198J。根据显微组织、硬度、冲击韧性和相变温度，确定了焊接CGHAZ区的CCT图。(C)2015爱思唯尔有限公司。保留所有权利。
Continuous cooling transformation (CCT) diagramswere determined for weld simulated coarse grained heat affected zone (CGHAZ) of Nb-microalloyed and HY 85 steels using a Gleeble (R) 3800 thermo-mechanical simulator. Samples were heated to a peak temperature of 1573 K (1300 degrees C) and cooled at different cooling rates from 0.5 K/s to 120 K/s. Microstructures, hardness, and impact toughness at 223 K were determined corresponding to simulated samples of weld CGHAZ thermal cycles. Transformation temperatures A(C3), A(C1), B-s, B-f, M-s, and M-f were also determined using dilatometric analysis. At slow cooling rates pro-eutectoid ferrite and pearlite were observed in Nb-microalloyed steel and a mixture of bainitic ferrite and granular bainite was observed in HY 85 steel but no pro-eutectoid ferrite was observed. At moderate cooling rates, only bainite was observed in both the steels. At high cooling rates, lath martensite was observed for both the steels. A strong dependence of prior austenite grain size on mechanical properties has been found. A prior austenite grain size of approximately 30 mu m (80 K/s) has shown impact toughness more than 100 J and 198 J for Nb-microalloyed steel and HY85 steel samples respectively. Based on microstructures, hardness, impact toughness, and transformation temperatures, CCT diagrams for the weld CGHAZ region were determined. (C) 2015 Elsevier Ltd. All rights reserved.