| 摘要 |
PURPOSE:To remove the local residual stress in the expanding part of a tube and to eliminate steps to prevent the generation of pitting by expanding the end of the tube, fixing this part to a supporting member and forming a thermally sprayed layer on the inside wall surface of the expanded part of the fine tube. CONSTITUTION:An evaporating water tube 2 which is the tube is fixed to the cylindrical wall part 1 of the frame of a heat exchanger body by expanding the end of this tube. The residual stresses are locally generated at the expanded point and the steps are formed on the inside wall surface. The thermally sprayed layer 3 is formed on the inside wall surface of the expanded part of such water tube 2. The generation of the pitting due to the residual stress and the erosion is prevented. The above- mentioned thermal spraying is executed by the thermal spraying device constituted of a thermal spraying gun section 4 which is provided with a delivery section 15 for feeding a thermal spraying wire 13, a main thermal spraying section 5 which has an air supplying plug 19, a vent hole 20 and an air ejection hole 21 and can be inserted into the above-mentioned expanded part, and a rotary type thermal spraying nozzle section 6 having an aperture. |
