Effects of Chromium on the Microstructure and Inclusions of Multipass Low Alloy Steels Weld Metal in Shielded Metal Arc Welding

Effect of chromium content on the microstructure and inclusions formation in low alloy steel multipass welds was investigated. Manual metal arc welding was performed in flat position according to AWS A5.5-96 standard. The ferro-chromium content in the coating was varied such that the final weld metal consists of 0.05, 0.53 and 0.91 wt.% chromium. Microstructure was studied by optical and scanning electron microscope in both columnar and reheated regions of the weld metal. The results showed increase in acicular ferrite formed at the expense of primary ferrite and ferrite with second phase with steady refinement of microstructure. Amount of microphases also increase as the chromium content of the weld metal increases. It is believed that chromium does not affect apparent characteristics (such as volume fraction and average size) and chemistry of inclusions.