Vol.2, No1&2, 2002, pp. 43-50
UDC 621.791.754.051:669.1

MICROCRACKS IN HAZ OF FINEGRAINED STEEL

WELDED IN CO2 SHIELDING

Aleksandar Živković 1

Marina Kutin 2

Stojan Sedmak 3

Zlatan Milutinović 2

M. Milanović 1

Miodrag Arsić 2

1 GOŠA - FOM, Smederevska Palanka

2 GOŠA - Institute, Smederevska Palanka

3 Faculty of Technology and Metallurgy, University of Belgrade

Abstract

Welding procedure specification (WPS) has been required for manufacturing of storage tanks of normalized fine grain microalloyed steel and of stainless steel for liquefied CO2 gas transport. MAG procedure has been selected for welding of these steels for low temperature application. Storage tank prototype had been tested by proof pressure 26 bar. Non-destructive testing (NDT) revealed microcracks, mainly distributed in the heat-affected-zone of fine grained steel. In order to identify the origin and cause of their initiation, mechanical tests and micrography analysis has been performed. Obtained results are discussed and a proposed version of improved WPS is presented in the paper.

Keywords: fine grain steel, CO2 shielded welding, welding procedure specification (WPS), heat-affected-zone, microcrack

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