Influência da temperatura de soldagem interpasses na zona termicamente afetada de grãos grosseiros simulada de tubo de aço AIS 4130

Abstract

The increase of the welding interpass temperature (IT) is pointed out for reducing the welding cost and time despite compromising the welded joint. The present work analyzed the influence of IT on the microstructure and impact toughness of the coarse grain heat-affected zone (CGHAZ) of an AISI 4130 steel pipe. The welding process was simulated in finite element method commercial software. CGHAZ was physically simulated in Gleeble® machine and evaluated through optical and scanning electron microscopy, electron backscatter diffraction, Vickers microhardness, and Charpy Vnotch impact. The increase of IT changed the microstructure from bainite (B) and martensite (IT 315 °C and 400° C) to B, ferrite with aligned carbides (AC), and ferrite pro-eutectoid (FP) (IT 400 °C), followed by AC, FP, ferrite with carbides non-aligned, and ferrite-carbide aggregate (IT 475 and 550 °C). This increased the effective grain size, modified the grain boundary charter distribution, and sharply reduced the impact toughness (IT > 315 °C not meeting ASME B31.3). Therefore, the indiscriminate increase of IT cannot be adopted as a practice to reduce the welding costs for AISI 4130 steel pipe.