Study the effects of the microstructure and microhardness on the external joint welding of stainless steel 316 pipe in sea water

الملخص

Austenitic stainless steels are very popular due to their high strength properties, ductility, excellent corrosion resistance and work hardening. This paper presents the test results for joining AISI 316 austenitic steel. The technologies used for joining were the most popular welding techniques such as TIG (welding with a non-consumable electrode in the shield of inert gases). The objectives of this research is to study the effect of welding parameters on the microstructural features and the micro hardness austenitic stainless steel 316 pipes. The welding process of Tungsten inert gas welding (TIG) process with stainless steel filler metalon austenitic stainless steel 316 pipes with outside diameter of 60mm and inside diameter of 55mm and 400mm length was carried using three different welding current of 130A,150A and 180A welding volte of 20V, welding speed and heat input. The welded pipe was left in offshore topside environment for six months.  Microstructural examinations in the face, center and root areas of the weld revealed different contents of delta ferrite with skeletal or lathy ferrite morphology. Additionally, the presence of columnar grains at the fusion line and equiaxed grains in the center of the welds was found. The hardness value of the welded seam in these joints ranges from 101 to 123 HB.