Abstract: The slag formed when concrete is melted by exposure to a laser beam, when caused to incorporate therein a MgO-rich supplementary material, loses it viscosity and, on cooling, refrains from expanding and, consequently, assumes a readily removable state. The slag thus set can be easily removed by allowing a cleaning device such as the rotary wire brush to pass along the part of concrete melted by the laser beam. In accordance with this method, the apparatus for cutting concrete can be readily applied to a remote control system and will manifest an outstanding effect in a highly hazardous site such as is involved in the dismantling of a biological shield wall of concrete in a nuclear reactor.

Abstract: Welding of deep penetration is obtained in a sustrate by a method which comprises first melting the joint portion of the substrates by MIG welding and then focusing a laser beam in the bottom surface of a crater formed in consequence of the MIG welding thereby effecting laser welding of the crater.

Abstract: A process of making a hole in a metal material of a large thickness comprises bringing the tip of an arc electrode wire into contact with the metal material while laterally reciprocating the arc electrode wire to thereby form an entry path on one side of the arc electrode wire and an exit path on the other side of the arc electrode wire within the hole, and causing a pressurized fluid to be introduced into the entry path, guided to the bottom of the hole and the exit path, and discharged out of the hole together with the molten metal lumps.

Abstract: Gas cutting of a plate material such as of stainless steel or stainless-clad steel is efficiently carried out by advancing a cutting torch along a mild steel bead formed on the material by melting thereon mild steel using a welding torch. When the material preheated in advance is burnt by directing a jet of oxygen thereto, the mild steel bead on the material effects to elevate the combustion temperature, thereby allowing refractory slag produced in cutting to be fused and blown off by virtue of the jet of oxygen.

Abstract: Disclosed herein is a device for cutting a pipe from the inside by the oxy-arc cutting technique. This device comprises, in combination, guide means for guiding the device proper inside a pipe subjected to cutting, fixing means provided with a plurality of claws adapted to be thrust radially from a cylinder in the direction of the inner wall of the pipe by the action of a piston actuated by the supply of a compressed fluid to the cylinder so as to hold the device immovable in position inside the pipe, and oxy-arc cutting means for cutting the pipe from the inside by the use of a covered hollow stick cutting rod rotated by a rotary shaft pierced through the center of the piston, with the exposed core of the cutting rod held in sliding contact under a fixed force with the inner wall of the pipe.

Abstract: In the consumable-electrode type arc cutting process whereby the work subjected to cutting is fused and severed by means of a continuous electric arc formed between the wire electrode protruding from the contact tip and the work, an improvement is obtained by the additional utilization of a jet of high-pressure water projected out of a water projection nozzle disposed on the outside of the contact tip. The jet of high-pressure water projected from said nozzle is directed to the point of arc formation on the work so as to blow the molten metal of the work away, whereby the severed edges of the work are prevented from being joined again and, at the same time, the dross is prevented from being deposited on the work and consequently the cut edge of the work is finished neatly.