Influence of the Surface Layer when the CMT Process Is Used for Welding Steel Sheets Treated by Nitrooxidation

I Michalec,M Marônek

doi:10.14311/1528

Abstract

Nitrooxidation is a non-conventional surface treatment method that can provide significantly improved mechanical properties as well as corrosion resistance. However, the surface layer is a major problem during the welding process, and welding specialists face many problems regarding the weldability of steel sheets. This paper deals with the properties of a nitrooxidized surface layer, and evaluates ways of welding steel sheets treated by nitrooxidation using a Cold Metal Transfer (CMT) process. The limited heat input and the controlled metal transfer, which are considered as the main advantage of the CMT process, have a negative impact on weld joint quality. An excessive amount of porosity is observed,probably due to the high content of nitrogen and oxygen in the surface layer of the material and the fast cooling rate of the weld pool.

Highlights

Steel sheets with surface treatment are widely used, above all in the automotive industry
An investigation is made of a new surface treatment method that has a major effect on improving the surface properties of steel sheets, e.g. their corrosion resistance
Nitrooxidation leads to a significant increase in corrosion resistance, and an increase in mechanical properties, e.g. yield strength and tensile strength [1, 2, 3]

Summary

Introduction

Steel sheets with surface treatment are widely used, above all in the automotive industry. An investigation is made of a new surface treatment method that has a major effect on improving the surface properties of steel sheets, e.g. their corrosion resistance. Nitrooxidation in a fluidized bed is a non-conventional surface treatment method. This process consists of nitridation with subsequent oxidation. This method integrates the wire motion into the welding process and into the overall control of the process. In this way, the, thermal input can be limited. This is a major advantage of this welding method [1, 4, 5]

Aims

Materials and methods

Results

Conclusion