CO2 Laser Welding Characteristics of 800 MPa Class TRIP Steel

Abstract

Basic characteristics of CO 2 laser welded 800 MPa class TRIP steel such as defects, microstructure, mechanical properties and formability was investigated. Bead-on-plate welding was carried out under various power, welding speed and shield gas. Porosity fraction reduced with increasing the welding speed and using Ar-He mixed shield gas compared to Ar gas. The maximum hardness was obtained at the weld metal as well as HAZ near the weld metal. The value was the same regardless of welding speed and was nearly equal to that of water quenched raw metal. In the perpendicular tensile test to the weld axis, the joints produced at optimum condition were fractured at the base metal and the tensile property was nearly equal to the raw metal. In a parallel tensile test, the strength of the joints was higher than that of the base metal, but elongation was found to be lower than that of the raw metal because a crack was initiated in the bead at the strength levels corresponding to the tensile strength of the base metal and was propagated perpendicular to tensile direction. Elongation and formability were further improved using low power or ArϩHe mixed gas compared to high power or Ar gas.

Microstructural Development during Welding of Silicon- and Aluminum-Based Transformation-Induced Plasticity Steels—Inclusion and Elemental Partitioning Analysis

“…Cretteur et al [3,4] attempted to improve the weldability of TRIP steels by pre-and postweld heat treatments during resistance spot welding and reported better mechanical properties with modified weld thermal profiles. Studies on the influence of CO 2 laser welding parameters by Han et al [5,6] showed porosity formation in the weld beads, resulting in poor mechanical properties. These authors concluded that increasing the speed of welding and lowering the laser power reduced the volume fraction of porosity and improved the properties of the welded material.…”

Microstructures and Properties of Ultra-high Strength Steel by Laser Welding

“…5,6) It can satisfy the welding requirements of UHSS theoretically. In this paper, a 4 kW Yb:YAG laser welding system is used to conduct the experiment, the lapwelding joints are made at different welding speed, joint morphology, microstructure, hardness, tensile-shear properties and fracture mode are analyzed and compared.…”

Numerical and Experimental Investigation of Tensile Behavior of Laser Beam Welded TRIP700 Steel

“…The effects of laser welding on the microstructures and mechanical properties of the TRIP steels had been evaluated and discussed in previous works. [10][11][12][13] The global mechanical behavior of the welds depends on the mismatch in mechanical properties between the different welded zones (WM, HAZ and BM), their dimensions and loading mode.…”