parent metal的用法和樣例：
例句
- After welding is complete, they shall be removed flush with the base metal without undercutting.
焊接完成後，應清除這些臨時部件至與母材金屬表面齊平，不得出現咬邊。 - The results show that certain thickness of the base metal and the regime of heat treatment will increase the peak hydrogen concentration and promote the tendency of disbonding.
結果顯示，一定的母材厚度和焊后熱處理條件，使熔合線附近氫濃度峰值提高，從而使氫剝離傾向增大。
