Comparison of microstructure and mechanical properties of ultra-narrow gap laser and gas-metal-arc welded S960 high strength steel

Abstract

The microstructural characteristics and mechanical properties, including micro-hardness, tensile properties, three-point bending properties and Charpy impact toughness at different test temperatures of 8 mm thick S960 high strength steel plates were investigated following their joining by multi-pass ultra-narrow gap laser welding (NGLW) and gas metal arc welding (GMAW) techniques. It was found that the microstructure in the fusion zone (FZ) for the ultra-NGLW joint was predominantly martensite mixed with some tempered martensite, while the FZ for the GMAW joint was mainly consisted of ferrite with some martensite. The strength of the ultra-NGLW specimens was comparable to that of the base material (BM), with all welded specimens failed in the BM in the tensile tests. The tensile strength of the GMAW specimens was reduced approximately by 100 MPa when compared with the base material by a broad and soft heat affected zone (HAZ) with failure located in the soft HAZ. Both the ultra-NGLW and GMAW specimens performed well in three-point bending tests. The GMAW joints exhibited better impact toughness than the ultra-NGLW joints.

Effect of the t8/5 Cooling Time on the Properties of S960MC Steel in the HAZ of Welded Joints Evaluated by Thermal Physical Simulation

“…Due to this, they are suitable for welding technologies with a concentrated heat source such as laser welding or electron beam welding. These phenomena are described in research papers by Guo et al [11,12] and Kopas et al [13]. Combining multiple techniques into one-the use of so-called hybrid technologies-is also one of the ways to achieve HSLA welded joints with satisfactory properties.…”

Microstructural characteristics of fibre laser welded joint of dual phase steel with complex phase steel

“…Advanced high strength steels (AHSSs) with zinc coatings such as high strength low alloy (HSLA) steels, dual phase (DP) steels, complex phase (CP) steels, TRIP steels, TWIP steels, martensitic steels, press hardened steels, etc. have been intensively studied [1][2][3][4][5][6]. A combination of high strength level and toughness of these steels is the consequence of their microstructure together with precipitation hardening and grain boundary strengthening mechanisms achieved through thermo-mechanical processing.…”

“…AHSSs are used in a wide variety of applications as structural components, pressure vessels and line pipes, and in shipbuilding, offshore construction, automotive, industrial vehicles, lifting and cranes. The application of AHSSs for such components enables lighter and more slender products and reduces construction costs without loss of structural integrity [5][6][7]. *Corresponding author: tel.…”

“…These properties guarantee the strength at still sufficient formability of safety car body parts made of TWBs using deep drawing process. The joining of sheets in TWBs is usually done by fibre laser welding because of excellent beam quality and high brightness of fibre lasers, high power, deep penetration, low beam divergence, high plug efficiency, and compact size coupled with flexible beam delivery [6,8,[17][18][19][20][21]. Low heat input is an important characteristic of laser welding, and it is the consequence of small fusion zone (FZ) and heat affected zone (HAZ) and the lower cost and higher flexibility compared to other welding methods.…”

Residual Stress Analysis of Laser Remanufacturing

“…Residual stress analysis of high-strength aluminium alloy pieces remanufactured by laser welding Solidification cracking and stress corrosion cracking frequently occur in high-strength aluminium alloys, on the account of their relatively large linear expansion coefficients and high stress corrosion cracking susceptibility [7,8]. Narrow gap laser welding (NGLW) is considered as one of the most effective ways to repair the cracks, for its lower heat input, less repairing deformation and better repairing quality, comparing with the conventional electric arc or plasma arc welding method [9][10][11][12]. However, residual stress of NGLW is also a vital factor for repairing quality of cracks and has been one of the research focuses of NGLW [13][14][15].…”