Manual Metal Arc Welding of Modified 9Cr-1Mo Steel Pipe

Abstract

Welding of modified 9Cr-1Mo Steel Pipe has been carried out by two filling passes using Manual Metal Arc Welding (MMAW) process at different energy inputs and post weld heat treatment at different temperatures. Microstructure-of the weld and HAZ has been studied and correlated with the post weld heat treatment and energy Input of the second pass, where the energy Input of the first pass was practically kept constant. At a given energy Input of first filling pass the influence of post weld heat treatment and energy input of the second pass on hardness of the weld and HAZ has been studied. At a given preheating the correlation among hardness (weld and HAZ). energy Input of first pass and energy Input of second pass, observed at different post weld heat treatments has been investigated. The tensile properties of weld joint, prepared at different energy Inputs of the second filling pass†and post weld heat treated at different temperatures, are also studied. It Is observed that the variation in energy input of the first and second filling passes, to control proper filling of the weld groove, affects the microstructure and hardness of the weld and HAZ. The post weld heat treatment at temperatures upto about 1123K(850"C) has been found to retain sufficient strength of the weldment. when the energy inputs of the first and second filling passes of SMAW are kept as about 2.7 and 4.1kJ/cm respectively.