Weldability of direct quenched, low-carbon, Ti-B-containing steels
- Pukyung National Univ., Pusan (Korea, Republic of)
- Pohang Iron and Steel Co. (Korea, Republic of)
On the basis of the thermodynamic equilibrium between nitrides of titanium, aluminum and boron in austenite, the soluble boron that influences the hardenability of direct quenched steels was calculated. The variation in tensile strength and impact toughness of steels has a good correlation with the calculated value at the start cooling temperature, 920 C. Impact toughness of the heat-affected zone (HAZ), however, was not influenced by the soluble boron alone but by the soluble boron to soluble nitrogen ratio at the welding peak temperature, 1,350 C. Only when the ratio was kept below 0.2 did the HAZ show a ferrite dominant microstructure and higher than 100 J of absorbed energy at {minus}20 C. During the welding cooling cycle, soluble boron combines with soluble nitrogen to form boron nitrides, consequently reducing the soluble boron and hardenability. Unlike conventional high-carbon steel, a low-carbon steel containing a controlled amount of boron showed a controlled amount of boron showed no cold cracking, without preheating, and a high HAZ toughness, with an energy transition temperature of {minus}37 C.
- OSTI ID:
- 477337
- Journal Information:
- Welding Journal, Vol. 76, Issue 4; Other Information: PBD: Apr 1997
- Country of Publication:
- United States
- Language:
- English
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