Effect of Preheating Temperature on Retention of δ-Ferrite in ASTM A355 Grade P92

Grade P92 steel has a possibility of forming delta (delta) ferrite phase in the weld fusion zone, which has several detrimental effects on mechanical properties. This study investigates the effect of preheating temperatures on the retention of delta-ferrite in Grade P92 steel welds. A relation between preheating temperature and thickness of welded plate using Rosenthal 2-D heat equation was developed, which can predict the preheat temperature for a given thickness of thin plates to achieve the full penetration. The welded joints were made using different preheating temperatures and with a fixed heat input using autogenous tungsten inert gas welding. Thermo-Calc software was used to predict phases formed as a function of temperature and for Scheil's solidification calculation. A DICTRA diffusion model was used to predict the volume fraction of delta-ferrite for different preheating temperatures. Full penetration was achieved with a preheat temperature of 300 degrees C for a 6 mm plate thickness. As preheating temperature is increased the volume fraction of delta-ferrite is reduced. The delta-ferrite retention is overestimated by DICTRA as compared to the retention measured experimentally from micrographs. (c) The Minerals, Metals & Materials Society and ASM International 2022

Automated summary

This study investigates the effect of preheating temperatures on the retention of delta-ferrite in Grade P92 steel welds. A relation between preheating temperature and thickness of welded plate using Rosenthal 2-D heat equation was developed. The volume fraction of delta-ferrite was predicted using the DICTRA diffusion model for different preheating temperatures.