Defocused CO_2 laser beam irradiation strengthening of 60kgf/㎟ grade steel sheet was investigated to obtain the tensile strength similar to that of fully penetrated one by the focused beam. The melted line width by the defocused beam was 3∼4 times...
Defocused CO_2 laser beam irradiation strengthening of 60kgf/㎟ grade steel sheet was investigated to obtain the tensile strength similar to that of fully penetrated one by the focused beam. The melted line width by the defocused beam was 3∼4 times larger compared to that of the focused beam. However, the increase of tensile strength with 1 line irradiation by the defocused beam was similar to that of 2∼3 lines by the focused beam. The increase(37.6%) of bending strength with 1 line by the defocused beam was higher than the increase(12.9%) of tensile strength. Also, the effect of cooling gas to strengthening was observed.