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1·Welding stress and concaving deformation of man-hole of steel vessel influence directly welding quality and life of using.

钢制容器人孔的焊接应力及塌陷变形，直接影响容器的焊接质量和使用寿命。

(1)concave mirrorn. 凹透镜

(1)concave surface凹面，内弧面

(1)concave grating凹面光栅

(1)concave lens凹透镜；近视镜片

(1)concave bank凹河岸；冲刷河岸