厚板のCO_2レーザ溶接金属の冶金学的性状

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In order to make clear the metallurgical characteristics of the heavy steel plate laser weld metal, the effects of cooling process and chemical compositions on hardenability and microstructure of the weld metal. Cooling rate and cooling time in the laser welding process were considerably correlated with the incident laser energy per unit welding length (heat input). Cooling rate and cooling time from 1073 to 773 K of the weld metal of 25 mm thick steel plate, which was welded with laser power of 45 kW and welding speed of 25 mm/s, was estimated at 35 K/s and 8 s respectively. The thermal efficiency in laser welding was almost the same as that in TIG welding, and the efficiency was estimated to be 50 to 60%. The hardness of laser weld metal was proportional to the carbon equivalent, Ceq IIW. Especially the laser weld metal with high carbon equivalent remarkably hardened compared to the submerged arc weld metal. The acicular ferrite structure, which was generally reported to result in high toughness, was also obtained in the laser weld metal containing Ti, O and B by controlling the chemical composition of weld metal in an optimum range. The acicular ferrite in the laser weld metal was finer than that in the submerged arc weld metal. The optimum range of carbon equivalent of the weld metal for acicular ferrite formation became narrow and sifted to lower carbon equivalent area as the cooling rate increased. For welding 25 mm thick steel plate with laser power 45 kW and welding speed 25 mm/s (cooling time from 1073 to 773 K : 8 s), the optimum Ceq IIW was ranged between 0.15 and 0.35 mass%.
社団法人溶接学会の論文
2000-02-05

厚板のCO_2レーザ溶接金属の冶金学的性状

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