| 摘要 |
PURPOSE:To provide the titled head case which sufficiently withstands the heat of welding and does not soften and to obtain high durability by forming the head case, etc., for the welding head of an automatic welding machine of a sintered body of silicon nitride. CONSTITUTION:This head case is constituted to a circular ring shape by butting and combining the ends of two pieces of case constituting bodies 1, 2 each having a semicircular shape. These bodies 1, 2 are formed of the sintered body of silicon nitride. The sintered body of silicon nitride which is ceramics has various excellent characteristics including electrical insulating characteristic, heat resistance, high temp. strength and wear resistance and, therefore, withstands the heat of arc welding. The softening of the head case or the failure thereof by receiving the heat of the arc at the time of welding the joint part of a pipe A is, consequently, obviated. Such head case maintains the sufficient mechanical strength and has no possibility of a decrease in the electrical insulating characteristic by the influence of the heat of welding.
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