HAZ hardness prediction of boron-added steels

The empirical equation to predict the heat-affected zone (HAZ) hardness of B-added steels has been proposed. For this purpose, weld thermal cycle simulation tests of both B-free and B-added steels in combination with hardness measurements were conducted. Firstly the previous HAZ hardness prediction equation was modified using the experimental results of B-free steels. Next, by introducing the B effect on hardenability to the modified equation, a new empirical equation to predict HAZ hardness of B-added steels was developed. The present equation takes into account the effects of peak temperature and Mo composition on B hardenability. The comparison of the predictions with the experiments of the weld thermal cycle simulation tests showed that the present equation can predict the HAZ hardness fairly well. The adjustable parameters of the B effect on hardenability introduced to the equation agree with the conventional results in the literature. To confirm that the present equation can be used to predict HAZ hardness of actual welded joints, hardness profile of welded joints was measured. The predicted HAZ hardness profile has shown to be in good accordance with the measured hardness profile.