Nippon Steel Sumitomo Metal Corporation

Sunao Takeuchi

Hideki Hamatani

Shinji Kodama

Hitoshi Asahi

Fuminori Watanabe

Tetsuro Nose

Nobuo Mizuhashi

Takashi Miyakawa

Michimasa Mukai

Michitoshi Tanimoto

Oleg Pavlovich Solonenko

Andrey Vladimirovich Smirnov

Tomohiro Nakaji

A plasma torch comprises a cascade between a cathode and an anode. The cascade is an inter-electrode insert. An interior of the cascade is shaped so that a diameter of the interior expands in series in a plurality of steps from a side of the cathode to a side of the anode. As a result of the cascade being provided, the output power of the plasma torch is obtained not by an increase in the electric current but by an increase in the arc electric voltage. Therefore, the lifespan of each of the electrodes, i.e., the cathode and the anode, becomes remarkably longer. In addition, since a quasi laminar flow of the plasma is generated in the interior of the cascade, a fluctuation in the output power of the plasma jet is reduced. Thus, it is possible to lower the driving and operating costs. Therefore, it is possible to perform surface treatment such as plasma spraying, utilizing a high-performance plasma processing, a processing of refractory powder materials, and plasma chemistry processing and the like, with a high degree of efficiency. In addition, a side shield module is provided at an outlet side of the anode of the forming nozzle. The side shield module generates a gas shield jet which is coaxial, annular, and low-velocity. Thus, gas from the surrounding environment is prevented from flowing in. Consequently, oxygen is prevented from entering the forming nozzle and the plasma jet. Hence, it is possible to generate a plasma jet having a low Reynolds number of the plasma forming gas, with a quasi laminar flow, exhibiting low noise, the diameter of its cross section expanding in a stable manner, having a long plasma length, and comprising argon, nitrogen, and hydrogen.

Plasma torch

The present invention provides a method of production of electric resistance welded steel pipe able to stably reduce weld defects due to oxides by firing plasma and furthermore able to reduce plasma jet noise and comprises shaping steel plateinto a tube and electric resistance welding the abutting end facesduring which blowing on at least the abutting end facesin the regionat the welding upstream side from the weld pointwhere the temperature becomes 650&#xb0; C. or more a reducing high temperature (pseudo) laminar plasma obtained by applying voltage to a reducing gas containing Hgas: 2 to 50 vol % to which is added a balance of Ar gas alone or a mixed gas of Ar gas to which Ngas, He gas, or both are added. At that time, it is preferable to make the applied voltage over 120V and the make the plasma blowing conditions satisfy the following formula (1). 

Method of production of electric resistance welded steel pipe and high Si or high Cr electric resistance welded steel pipe

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Tokyo, Japan

Sunao Takeuchi