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Microstructure Characterization of High-heat-input Welding Joint of HSLA Steel Plate for Oil Storage Construction

2009; Elsevier BV; Volume: 25; Issue: 06 Linguagem: Inglês

1941-1162

Weihua Sun, Guodong Wang, Jiming Zhang, Dianxiu Xia, Hao Sun,

Welding Techniques and Residual Stresses

In this paper, microstructure and mechanical properties of welding metals in 610 MPa high strength low alloy (HSLA) were studied after high-heat-input welding. Both the base material and the weld joint proved excellent strength and toughness by vibratory electrogas arc (VEGA) welding under 90 to 100 kJ/cm heat- input. The heat-afiected zone (HAZ) was comprised of flne-grain zone (FGZ) and coarse-grain zone (CGZ), which characterizes flne granular structure and lathing-bainite substructure. It has found that large quantity of dispersed TiN and M23C6 precipitates restrain structure growing in HAZ and strengthen the weldment together with dislocations in the welded joint. joint of 610 MPa steel plate was examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Strength and toughness were also tested for the weldment. 2. Experimental The JGR610E material was manufactured in Ji- nan Iron and Steel Co., Ltd., China. The steel plate was 34 mm in thickness processed by on-line accel- erated cooling and ofi-line tempering. The chemical composition of the steel plate is listed in Table 1. The steel plate was welded by VUP-NA3 type VEGA welding machine on V-type slope under a heat- input about 90 to 100 kJ/cm with a controlled cur- rent and voltage approximately 390 A and 40 V, re- spectively. The welding speed was 1.6 mm/s. The welding material was DWS-60G. Tensile tests and V- notch Charpy impact tests were carried out at speci- fled positions parallel to the weldment central line on an Instron 1251 type tensile machine and a JB-30B Charpy impact test machine according to GB/T228- 2002 and GB/T229-1994, respectively. For V-notch Charpy impact tests, three samples were tested and compared with the base material. The weld joint was cut by a Struers cutter to make TEM investigations in the welding line, HAZ and in the base material, respectively vertical to the plate thickness. Microstructures of the weldment were examined on an FEI X30 SEM after etched in 4% nital solu- tion. A highly automated 300 kV TEM (FEI Tecnai G2 F30, USA) was applied to carry out the investiga- tion.