Grain Refinement in Ferritic Stainless Steel Welds: The Journey so Far

Abstract

The ferritic stainless steel is a low cost alternative to the most often adopted austenitic stainless steel due to its higher strength, better ductility and superior corrosion resistance in caustic and chloride environments. However, the application of ferritic steel is limited because of poor ductility and notch impact toughness of its weld section with differential grain structures. Several techniques have been explored to control the grain features of the weld to minimize these problems. In the present effort, a review of these options in relation to the degree of grain refinement in ferritic stainless steel weld is conducted in order to have a better understanding about the grain refining phenomenon in the weld microstructure. So far, the most effective technique is found to be the pulse AC TIG welding which can produce weld with mechanical properties equivalent to 65% to those of the base metal. The refinement in this process occurred through dendrite fragmentation and grain detachment in the weld pool producing small-grained microstructures with a large fraction of equiaxed grains. However, in friction welding process where heat input and heat transfer are effectively controlled, the strength can be as high as 95% of the parent metal. This suggests that the total energy input for welding and heat transfer phenomenon mainly control the development of microstructural feature in the weld pool and hence the strength.

Metallurgical and Mechanical Properties Variation Along the Thickness of Electron Beam Welded Ferritic Stainless Steel Joints After Postweld Heat Treatment

“…Ferritic stainless steel has gained great popularity in the last decade, but its applications are still restricted due to postweld issues associated with the fusion welding process [4]. The main reason behind the poor weldability of ferritic stainless steel is the non-existence of any inter-phase, the occurrence of fully ferrite phase, and the coarsening of grains in the fusion zone and heat-affected zone during welding [1].…”

Effect of post weld heat treatment on metallurgical and mechanical properties of electron beam welded AISI 409 ferritic steel

“…Severe grain growth in the regions exposed to heat, absence of any interphase precipitations, and formation of fully ferrite structure during solidification of the weld pool leads to a reduction in ductility and toughness of FSS [12]. Amuda and Mridha [13] reported that a slow cooling rate during welding gave sufficient time for grains to elongate, which further affects the metallurgical and mechanical properties. Mohandas et al [14] compared the mechanical properties of a 3mm thick FSS weld joint using gas tungsten arc welding(GTAW) process and shielded metal arc welding (SMAW) process.…”

Influence of Size on the Microstructure and Mechanical Properties of an AISI 304L Stainless Steel – A Comparison between Bulk and Fibers

“…Stainless steels are a group of engineering materials that have been used extensively owing to their properties, such as corrosion resistance and physical and mechanical properties www.videleaf.com [1,2]. Among the various types of stainless steels, austenitic and ferrite types are ones of the most widely used.…”