Carbon Equivalence and Weldability of Microalloyed Steels

摘要

In the final report of the effort determine the validity of carbon equivalent formulae to predict weldability of low carbon microalloyed steels, the HAZ of a range of steels was characterized (HSLA 80-130, HY 130, DQ and AC types) and the formula of Yurioka was found to be most accurate in predicting HAZ hardness. The CE1 carbon equivalent formula was also found to most accurately predict hardenability except that the effect of copper is not linear above 0.5%. The hydrogen sensitivity was evaluated by the Implant, Battelle and UT-Mod Hydrogen Sensitivity tests at two hydrogen levels. The Lower critical stress in the Implant test was utilized to define the critical preheat temperatures for the steels evaluated. The HSLA 80 type materials may require a preheat of 150 F under highly restrained conditions with hydrogen present. HSLA 130 was found to be superior to HY 130 in regard to hydrogen cracking sensitivity. The high strength steels can be ranked in the order of increasing preheat required to prevent cracking as: HSLA 100--HSLA 130--DQ 125--HY 130 DQ 80 and AC 50 steels responded well to testing at high hydrogen levels (20ppm) and ambient temperature preheat.