The Influence of Laser Welding on the Mechanical Properties of Dual Phase and Trip Steels

Abstract

Nowadays, a wide range of materials is used for car body structures in order to improve both the passengers' safety and fuel consumption. These are joined by laser welding and solid state fiber lasers being used more and more in present. The article is focused on the research of laser welding influence on the mechanical and deformation properties, microstructure and microhardness of advanced high-strength steels: high-strength low-alloyed steel HC340LA, dual phase steel HCT600X and multi-phase residual austenite steel RAK40/70. The proper welding parameters have been found based on weld quality evaluation. The specimens for tensile test with longitudinal laser weld were used to measure mechanical and deformation properties. Microstructure and microhardness of laser welds were evaluated in the base metal, heat affected zone and fusion zone. The higher values of strength and lower ones for deformation properties of laser-welded materials have been found for dual and multi-phase steel. The microhardness strongly depends on the carbon equivalent of steel. Deformation properties are more sensitive than strength properties to the change of microstructure in the fusion zone and heat affected zone.

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

“…Several works were devoted to the laser welding of different DP steels, such as DP600, DP780, DP800, DP980, DP1000, and DP1180 grades with a different portion of ferrite and martensite phases [1, 3, 10, 11, 18, 22, 23, 25-28, 30, 33-36]. Other works were focused on laser welding of DP steels with HSLA [2,31,32] and TRIP steels [2,9,13,[37][38][39][40][41][42], but fewer works were focused on welding of DP steels with CP steels. The microstructure in the sub-zones of welded joints has been studied to define properties of welded joints.…”

Laser Welding

“…The present special issue on "Laser Welding" was a success with a total of 16 original research works published after peer-review. Different topics were discussed within this special issue: modelling and simulation of laser welding were presented in [1][2][3][4]; porosity control by means of high speed imaging and microscopy techniques was studied and discussed [5]; the effect of processing parameters on the microstructure and mechanical properties of laser-welded joints was evaluated for different metallic systems such as AZ31 alloy [6], steels [7][8][9][10], Ti-based alloys [11][12][13], and Al-based alloys [14]; and finally, dissimilar laser welding of aluminum to steel was presented [15,16].…”

Anisotropic Hardening Behaviour and Springback of Advanced High-Strength Steels

“…The Yld2000-2d yield function [6] has eight parameters (α [1][2][3][4][5][6][7][8] ) that require eight mechanical properties (σ 0 , σ 45 , σ 90 , σ b , r 0 , r 45 , r 90 , r b ). The m value is suggested as six for BCC and eight for FCC metal.…”

“…In this work, we investigate the application of advanced high-strength steels (AHSSs), with good strength and formability, in automotive parts. The demand for automotive parts made of AHSSs is based on their excellent impact resistance, which is an asset for the reinforcement of the car body structure, and which depends on their high strength [3][4][5][6][7]. However, along with their high strength and low thickness, the AHSSs exhibit anisotropic properties and large springback recovery after forming [8,9].…”