A Study on the Fiber YAG Laser Welding of 304L Stainless Steel

Essam R I Mahmoud,Abdulrahman Aljabri,Hamad Almohamadi,Mohamed Abdelghany Elkotb

doi:10.3390/met11122022

Abstract

This work aims to optimize the main YAG fiber laser parameters to weld 304L stainless steel plates of 3 mm thick. Different laser powers (2500, 2000, and 1500 W) and speeds (60, 40, and 20 mm/s) were used and merged in heat input, maintaining the defocusing distance at –2 mm to get full penetration. The weld quality and the effect of the laser heat input on the microstructures of the weld and heat-affected zones were investigated. Besides, the fracture strength of the welded joints and hardness distribution through the cross-sections were evaluated. The weld width has a direct relationship with heat input. The laser power of 2800 W produced full penetration joints without any macro defects while reduction in laser power pronounced partial penetration defects. The size of the heat-affected zone in all the processing parameters was very small. The microstructure of the weld zone shows columnar dendrite austenite grains with small arm spacing in most of the welded zone. The size of the dendrites became finer at lower heat input. At a higher heat input, a reasonable amount of lathy equiaxed grains with some delta ferrite occurred. A small amount of delta ferrite was detected in the heat-affected zone, which prevented the crack formation. The hardness of the weld metal was much higher than that of the base metal in all processing parameters and it has a reverse relationship with the heat input. The fracture strength of the welded joints was very close to that of the base metal in the defect-free samples and it increased with decreasing the heat input.

Highlights

Alloys 304 and 304L stainless steels are extensively used as austenitic stainless steel alloys
This low carbon content is attributed to the typical corrosion resistance in 304L stainless steel
Macro/Microstructure of the Welded levels isFigure directly affected by theFigure net heat input

Summary

Introduction

Alloys 304 and 304L stainless steels are extensively used as austenitic stainless steel alloys. Alloy 304L is a low-carbon version of the 304 stainless steel alloy with a carbon content that reaches 0.03% This low carbon content is attributed to the typical corrosion resistance in 304L stainless steel. Alloy 304L exhibits deep drawing capacity with excellent resistance to corrosion as well as relative ease in fabrication. Due to these properties, it finds a wide spectrum of applications, especially in nuclear applications (Pumps, steam lines, spend fuels reprocessing, and transport), food processing industry (breweries, milk, etc.), kitchen features (sinks, platforms, equipment, appliances, etc.), architecture industry (trims, molds, panels, etc.), marine applications, fasteners, heat exchangers, chemical containers, welded, and woven water filtration screens, etc. It finds a wide spectrum of applications, especially in nuclear applications (Pumps, steam lines, spend fuels reprocessing, and transport), food processing industry (breweries, milk, etc.), kitchen features (sinks, platforms, equipment, appliances, etc.), architecture industry (trims, molds, panels, etc.), marine applications, fasteners, heat exchangers, chemical containers, welded, and woven water filtration screens, etc. [4,5,6,7,8]

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