Lee Ho Won, Yoo Kwang Jae, Tran Minh Tien, Moon In Yong, Oh Young-Seok, Kang Seong-Hoon, Kim Dong-Kyu
Department for Virtual Materials Processing, Korea Institute of Materials Science, Changwon 51508, Korea.
School of Mechanical Engineering, University of Ulsan, Ulsan 44610, Korea.
Materials (Basel). 2019 Sep 5;12(18):2862. doi: 10.3390/ma12182862.
In the present study, we have investigated the effect of post-welding heat treatment (PWHT) of quenching and tempering (QT) on the microstructure and mechanical properties of welded boron steel joints processed using laser-arc hybrid welding on two commercial filler materials, SM80 (Type-I) and ZH120 (Type-II). The microstructure and mechanical properties of the weld joints were characterized via optical microscopy, Vickers microhardness, and the uniaxial tensile test. The macrostructure of the weld joint was composed of a fusion zone (FZ), heat-affected zone (HAZ), and base metal zone (BMZ). After the QT-PWHT, the QT specimens revealed the V-shape hardness distribution across the weld joint, while the as-welded specimen exhibited the M-shape hardness distribution. As a result, the QT specimens revealed the premature fracture with little reduction in the area at the interface between the HAZ and FZ, while the as-welded specimen exhibited the local necking and rupture in the BMZ. In addition, the Type-II filler material with a greater value of equivalent carbon content was rarely influenced by the tempering, maintaining its hardness in the as-quenched status, while the Type-I filler material showed a gradual decrease in hardness with the tempering time. The results demonstrate that the Type-II weld joint outperformed the Type-I weld joint in terms of the structural integrity of welded parts.
在本研究中，我们研究了淬火回火（QT）后的焊后热处理（PWHT）对使用激光电弧混合焊接工艺在两种商用填充材料SM80（I型）和ZH120（II型）上加工的硼钢焊接接头的微观结构和力学性能的影响。通过光学显微镜、维氏显微硬度和单轴拉伸试验对焊接接头的微观结构和力学性能进行了表征。焊接接头的宏观结构由熔合区（FZ）、热影响区（HAZ）和母材区（BMZ）组成。经过QT-PWHT后，QT试样在整个焊接接头上呈现出V形硬度分布，而焊态试样则呈现出M形硬度分布。结果，QT试样在热影响区和熔合区之间的界面处出现过早断裂，断面收缩率很小，而焊态试样在母材区出现局部颈缩和断裂。此外，等效碳含量较高的II型填充材料很少受到回火的影响，在淬火状态下保持其硬度，而I型填充材料的硬度则随着回火时间的延长而逐渐降低。结果表明，在焊接部件的结构完整性方面，II型焊接接头优于I型焊接接头。
