Abstract: A scale removing device for removes scale adhering to the interior of a shell-and-tube-heat-exchanger-type steam generator. The scale removing device is provided with a flexible lance (58) holding a high-pressure water hose (91) movable with respect to a tube plate, tube support plates, and heat-transfer tubes. A cleaning head (60) is mounted to the forward end of the flexible lance. Formed inside the cleaning head is a cavitation generating nozzle hole (99a, 99b) communicating with the high-pressure water hose. Bubbles are generated at the time of cleaning, and the impact pressure generated when the bubbles collapse is propagated to remove scale over a wide range.

Abstract: A method of improving the functions of the surface of alloy steel by means of the irradiation of a laser beam is disclosed. In this method, the alloy steel is kept in contact with the aqueous solution of oxidizing acid or salt thereof and the irradiation of a laser beam is applied on the surface of the alloy steel through the aqueous solution, thereby concentrating an alloy component on the surface of the alloy steel. The aqueous solution contains at least one selected from the group consisting of nitric acid or nitrate, chromic acid or chromate, or permanganic acid or permanganate. In addition, the irradiation of the laser beam is applied so as to depict a given pattern on the surface, and a computer controls the shape and the size of the beam, the position of the alloy steel, and the like. The present method enables the improvement of a surface function of the alloy steel by providing various kinds of color-patterns.