Influence on factors of cold crack formation factors of a steel 10G2FBYu welded joint by regulating linear energy

Abstract

ABSTRACT The article considers the influence of heat input and ambient temperature on the resistance to cold cracks formation in welded joints of high-strength steel 10GFBU. The studies were carried out on Tekken samples with variation of heat welding input from 5.7 to 14.3 kJ/cm and ambient temperature from – 20 to +20 °С. To analyse the reaction of the metal to the thermal cycle of welding, metallographic and durometric studies of the welded joints metal were carried out and its cooling rate was calculated in the temperature range of 800–500°C. As a result of the research, it was found out that the heat input has a direct impact on the resistance to the cold cracks formation in the welded joints metal and it should be taken into account when assigning the preheating temperature. In particular, at the value of the effective heat input of 10.3 kJ/cm cold cracks are not formed during the welding without preheating of steel of 18–36 mm thickness at an ambient temperature of 20°C, and are not formed at not less 14.7 kJ/cm heat input at – 20°C. The critical cooling rate, which provides resistance cold cracking of the weld metal made with electrodes ESAB MTG-01К is 55°C/sec. To assess the effect of preheating temperature and heat input on the cooling rate of the HAZ metal in the temperature range of 800–500°C the corresponding dependencies were constructed, from which it follows that the most significant effect of preheating on V8/5 is observed when welding at low heat input characteristic of manual electric arc welding.