Effects of preheat on weldments of NICOP steel

Abstract

Shielded metal arc weldments of Armco Steel Corporation's NICOP class 3, 19mm (3/4 inch) plate, conforming to ASTM A710 grade A, were studied to provide information concerning the microstructure in the heat affected zone (HAZ) of weldments fabricated with and without preheat. Microhardness , scanning electron microscopy and transmission electron microscopy were used to determine the effect of preheating on the microstructure Similar microstructures in the preheat and non-preheat samples were observed. The microstructures were polygonal and acicular ferrite in the base and base/HAZ regions and increasing amounts of bainite and auto tempered martensite islands near the fusion line. From the point of view of microstructure, NICOP appears to be weldable without preheating.