Microstructure and Mechanical Properties of Heat-affected Zone of Repeated Welding on 304 Stainless Steel
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摘要: 采用自动钨极氩弧焊接（GTAW）工艺设计刚性约束坡口，制备了304不锈钢1次焊接和1~5次试样。采用光学显微镜、X射线衍射（XRD）、扫描电子显微镜（SEM）与电子背散射衍射（EBSD）技术对重复焊接试样的热影响区（HAZ）显微组织进行观察分析，并开展室温拉伸性能测试，研究重复焊接对显微组织与力学性能的影响。结果表明，重复焊接试样的HAZ显微组织主要由奥氏体和条状δ铁素体组成，随着重复焊接次数增加，HAZ奥氏体晶粒尺寸呈长大趋势，δ铁素体含量先减少后增加，组织择优取向由<101>转变为<111>，局域取向差逐渐增大；晶粒尺寸是影响抗拉强度和延伸率变化的主要原因，加工硬化致使试样屈服强度逐渐增加。Abstract: The effect of the repeated welding on the microstructure and mechanical properties of the heat-affected zone (HAZ) for 304 stainless steel were investigated under repeated welding up to five times by automatic gas tungsten arc welding using an optical microscope, a x-ray diffraction, a scanning electron microscope and an electron back-scattered diffraction. The repeated welding specimens were consisted with the microstructures of austenitic matrices with lath δ-ferrite. With the increasing of the repeated welding times, the average values of the austenitic grain size increased, and the δ-ferrite content decreased then increased. The preferred orientation of the HAZ changed from <101> to <111>. The values of location misorientation increased monotonically with the increasing number of repeated welding. The variation of the ultimate tensile strength and elongation was affected by the grain size mainly. Due to the hardening rate increasing, the yield tensile strength was increasing.
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图 1 焊件坡口尺寸与试样取样位置示意图
Figure 1. Dimensions of Welding Groove and Sampling Position of Test Specimen
图 6 重复焊接试样的HAZ室温拉伸性能
Figure 6. Tensile Properties of the HAZ of Repeated Welding at Room Temperature
图 7 重复焊接试样的HAZ硬化率-真应变曲线局部图
Figure 7. Enlargement of Hardening Rate-true Strain Curves of the HAZ of Repeated Welding
图 8 重复焊接试样的HAZ拉伸断口形貌（纤维区）
Figure 8. Micro-Fracture of the HAZ of Repeated Welding (Fibrous Region)
表 1 钢板化学成分与力学性能
Table 1. Chemical Composition and Mechanical Properties of AISI 304 Stainless Steel
位置 化学成分/wt%① 拉伸强度/MPa C Cr Ni Mn Si P S N 平均抗
拉强度屈服
强度母材 0.05 18.545 8.211 1.6 0.5 0.034 0.001 0.12 550 240 焊材 0.023 19.111 9.303 1.56 0.543 0.026 0.006 —② — — 注：①wt%—质量百分数；②“—”—无数据 
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表 2 自动GTAW焊接参数
Table 2. Welding Parameters of Auto-GTAW
焊道
编号电流/
A电压/
V焊接速度/
(mm·s−1)送丝速度/
(mm·min−1)热输入/
(kJ·mm−1)1 260 9.50 1.52 89 1.62 2 260 9.20 1.52 89 1.57 3~7 260 9.50 1.52 89 1.62
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