Effect of Post Weld Heat Treatment on the Microstructure and Mechanical Properties of a Submerged-Arc-Welded 304 Stainless Steel

Tae-Hoon Nam,Namhyun Kang,Won-Seok Ko,Nokeun Park,Eunsol An,Sunmi Shin,Jong Jeon,Byung Kim

doi:10.3390/met8010026

Abstract

The present study is to investigate the effect of post heat treatment on the microstructures and mechanical properties of a submerged-arc-welded 304 stainless steel. The base material consisted of austenite and long strips of delta-ferrite surrounded by Cr-carbide, and the welds consisted of delta ferrite and austenite matrix. For the heat treatment at 850 °C or lower, Cr-carbides were precipitated in the weld metal resulting in the reduction of elongation. The strength, however, was slightly reduced despite the presence of Cr-carbides and this could possibly be explained by the relaxation of internal stress and the weakening of particle hardening. In the heat treatment at 1050 °C, the dissolution of Cr-carbide and disappearance of delta ferrite resulted in the lower yield strength and higher elongation partially assisted from deformation-induced martensitic transformation. Consequently, superior property in terms of fracture toughness was achieved by the heat treatment at 1050 °C, suggesting that the mechanical properties of the as-weld metal can be enhanced by controlling the post weld heat treatment.

Highlights

Austenitic stainless steels are widely used in important parts of chemical plants such as pressure vessels, chemical machineries, and pipes because they have excellent corrosion resistance, acid resistance, formability, and weldability
The base metal consisted of austenite single phase and hot-rolling strips
These rolling strips correspond to delta ferrite surrounded by Cr-based carbides precipitated during hot rolling (Figure 2d–f)

Summary

Introduction

Austenitic stainless steels are widely used in important parts of chemical plants such as pressure vessels, chemical machineries, and pipes because they have excellent corrosion resistance, acid resistance, formability, and weldability. They are extensively applied in gas turbines, jet propellants, and nuclear power plants because of their excellent toughness in high-temperature and high-pressure environments [1,2,3,4]. In SAW, a solid filler wire is automatically inserted to pre-dispersed granular flux and an arc generates between the base metal and the filler wire while being covered with flux.

Methods

Results

Conclusion