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.

提出了经验公式来预测添加B的钢的热影响区（HAZ）硬度。为此，结合硬度测量结果对无B和添加B的钢进行了焊接热循环模拟测试。首先，使用不含B的钢的实验结果修改了先前的HAZ硬度预测方程。接下来，通过将B对淬透性的影响引入修正方程，开发了一个新的经验方程式来预测添加B的钢的HAZ硬度。本方程考虑了峰值温度和Mo组成对B淬透性的影响。将预测结果与焊接热循环模拟测试的实验结果进行比较表明，该方程可以很好地预测HAZ硬度。引入方程的B对淬透性影响的可调参数与文献中的常规结果一致。为了确认本方程可用于预测实际焊接接头的HAZ硬度，测量了焊接接头的硬度分布。预测的HAZ硬度分布已显示与测得的硬度分布非常吻合。