Abstract
AISI Type 304L austenitic stainless steels are extensively used in industries, and welding is an indispensable tool used for joining these materials. In a multi-pass weld, the development of residual stress to a large extent depends on the response of the weld metal, heat affected zone and parent material to complex thermo-mechanical cycles during welding. Earlier researchers on this area used either mechanical tensioning or heat treatment to modify the residual stress distribution in and around the weld. In this research, microstructural refinement with modification of residual stress state was attempted by using high pressure cold rolling followed by laser processing in 12mm thick 304L austenitic stainless steels which is a novel technique. The hardening of the weld metal was evaluated after welding, post weld cold rolling, and post weld cold rolling followed by laser processing. The residual stress was determined non-destructively by using neutron diffraction. Residual stress analysis show that post weld cold rolling was effective in modifying the longitudinal residual stress distribution throughout the entire thickness. Post weld cold rolling followed by laser processing performed in this research was to induce recrystallization of the cold rolled grains. However, post weld cold rolling followed by laser processing showed minor grain refinement but was not effective as it reinstated the stress state.
Highlights
Austenitic stainless steel types are the most widely used stainless steels which contain nominally 18% chromium and 8% nickel
Effect of post weld cold rolling followed by laser processing Laser processing after cold rolling has been shown to increase the longitudinal residual stress from compressive stress of 80 MPa to peak tensile stress of 479 MPa (Fig. 11) indicates a high thermal input and non-uniform cooling of the material, generating inhomogeneous plastic deformation and tensile residual stresses
This paper investigates the possibilities of using local mechanical tensioning followed by laser treatment to create a refined and recrystallized microstructure with modified residual stress state, improving the fatigue life of welded structures
Summary
Austenitic stainless steel types are the most widely used stainless steels which contain nominally 18% chromium and 8% nickel. These material exhibits an attractive combination of good strength, ductility, toughness, excellent corrosion resistance and good weldability [1,2]. Due to these attributes, austenitic stainless steels are used in a range of industries such as thermal power generation, biomedical and petrochemical, automotive, and chemical engineering [3]. In 300 series austenitic stainless steel grades, AISI 304L stainless steels are extensively used in industries due to their superior low temperature toughness in addition to high corrosion resistance. Example of application of these materials include storage and transportation of liquefied natural gas [4] which was reported that, an estimate of more than 20,000 t of 304 and 304L austenitic stainless steels are used per year [5]
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