Statistical Analysis Of Repetitive Repair Welding Using GMAW On Stainless Steel Joint

Akasak, Nurul Syazwani (2019) Statistical Analysis Of Repetitive Repair Welding Using GMAW On Stainless Steel Joint. Project Report. UTeM, Melaka, Malaysia. (Submitted)

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Abstract

This study is mainly about repetitive repair welding on similar stainless steel joint using GMAW. The material chosen is AISI304 and the welding process used is GMAW. AISI 304 is being used widely in high temperature working environment so they will face a lot of damage and failure. Repair welding is one of the important maintenance processes. Repair welding process able to restore original function of a part if weld failure happened due to service drop or defect during fabrication stage. Thus, this process is more convenient rather than replacing or buy new parts or structure. However, repetitive repair welding will produce high heat input to the weld metal and change the microstructural and mechanical properties. This study also reviewed about the effect of repetitive repair welding on AISI 304 stainless steel to the microstructural changes and mechanical properties of the weld metal. The planning matrix of parameters used was designed using Taguchi Method. After finished the analysis of the results using Analysis of Variance method (ANOVA), the optimum parameters for first repair are proposed and the modeling values are gained as reference for the next repair weld process. The low heat input combinations that occur during the repair welding process produce relatively high strength and vice versa. Subsequently, test results show that dendritic structures have been formed during welding, most of which consist of ferrite and austenite delta structures. The basic metals initially had a micro structure consisting of austenitic matrices and delta-ferrite bands. However, the microstructure changes as an induced heat input on the welded part which causes the ferrite delta to partially melt in HAZ which produces relatively low microhardness values over the weld metal.

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