| 摘要 |
PROBLEM TO BE SOLVED: To suppress the generation of blowholes and pits in a steel sheet and to impart excellent arc weldability thereto by applying the surface of a plated steel sheet coated with a specified amt. of galvanizing with a specified amt. of zinc phosphate film. SOLUTION: The surface of a steel sheet 1 is plated with galvanizing so as to control the coating weight per side to 15 to 80 g/m2. Next, the surface of this plating layer 2 is applied with a zinc phosphate film 3 of 0.1 to 3.0 g/m2 coating weight. By an arc, the galvanizing is made into vapor, and zinc phosphate is also dispersed into zinc, phosphorous, oxygen and hydrogen. Phosphorous forms a compd. of phosphorous-iron to fix zinc, and oxygen is compounded with zinc to form into zinc oxide and fixes zinc. Gaseous hydrogen promotes the releasing action of vaporized zinc to the outside of the weld zone. The surface of this galvaznied steel sheet is, if required, applied with an amorphous inorganic film 4 soluble in an acid aq. soln., hard to dissolve in a neutral or alkali aq. soln. and contg. about >=5% Mg via the zinc phosphate film 3 to improve its workability and corrosion resistance.
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