Self-Gathering Effect of the Hydrogen Diffusion in Welding Induced by the Solid-State Phase Transformation.

Zhiliang Xiong,Jianguo Yang,Liping Tang,Wenjian Zheng

doi:10.3390/ma12182897

Abstract

The hydrogen diffusion in welding was investigated by using thermal-mechanical-hydrogen diffusion sequential coupled procedures based on finite element method. A self-gathering effect induced by the solid-state phase transformation was discovered. Because of the self-gathering effect, the hydrogen concentration in weld metal was accumulated to a peak value which can be larger than the initial hydrogen concentration in molten pool, and subsequently the hydrogen concentration in heat affect zone was redistributed. In multi-pass welding, the gathered effect not only happened inside a weld pass, but also in the inter-pass, which further increased the sensitivity of the hydrogen-assisted cold cracking. Controlling should be adopted to restrain the hydrogen accumulation. Welding stress evolution during the solid-state phase transformation process had limited effect on the hydrogen diffusion.

Highlights

High strength steel (HSS) usually requires manufacture processes and assembling methods in fabrication industry, such as welding, coating, additive manufacturing, etc
In our investigation, with the influence of solid-state phase transformation (SSPT), the hydrogen concentration of the center domain of the weld metal (WM) increased in the temperature range of SSPT
The hydrogen diffusion in the single-pass and multi-pass welding was predicted by a thermal-mechanical-hydrogen diffusion sequential coupled procedure considering the SSPT effects in a high strength X80 pipe steel

Summary

Introduction

High strength steel (HSS) usually requires manufacture processes and assembling methods in fabrication industry, such as welding, coating, additive manufacturing, etc. It is generally agreed that the occurrence of hydrogen-induced cracking requires several factors. For the HACC in welded joint, the factors are hardened microstructures such as martensite and bainite, residual stress and the hydrogen introduction from the atmosphere [10]. There has not been an effective in situ testing method to detect the hydrogen concentration inside the welded joint. Most of the studies were concentrated on the hydrogen effect on the welded joint after the welding [11,12,13,14,15,16,17,18,19], rather than during the welding

Methods

Results

Conclusion