Use of Martensitic Stainless Steel Welding Consumable to Substantially Improve the Fatigue Strength of Low Alloy Steel Welded Structures

Abstract

An iron base alloy containing 10wt.% Cr and 10wt.%Ni with a martensite start temperature around 180°C has been developed by Ohta et al. Numerous studies have shown that Low γ→α’ Transformation Temperature (LTT) welding consumables enable weld beads to be in compression after cooling. Owing to this, fatigue strength can be substantially improved. Low carbon martensitic stainless steel consumables (EN ISO 17633-A -T Z 16 5 1) are widely available on the market in Europe, which also exhibit γ→α’ low temperature transformation (around 225°C), despite dilution with base material. Experimental work conducted on partially penetrated symmetric and asymmetric fillet welded test pieces have shown good results with respect to weld root crack initiation and a substantial improvement of fatigue resistance with respect to weld bead toe crack initiation (m = - 5, FAT > 160). These results are all the more interesting because the weld bead connecting radius obtained with a heterogeneous welding consumable is smaller than with a homogeneous consumable such as G3Si1. This study shows that using a LTT –type consumable with designation G 16 5 1 is an interesting alternative to more conventional techniques such as TIG re-melting or high frequency mechanical impact to improve fatigue strength of welded structures.