Constricting nozzle and tig welding torch using this nozzle

A constricting nozzle attached to a tungsten inert gas (TIG) welding torch, wherein a shielding gas that has flowed through an inside of a torch body of the TIG welding torch is laminarized by a gas lens disposed at a forward end of the torch body, wherein the laminarized shielding gas is discharged from a cylindrical shielding nozzle disposed at the forward end of the torch body toward a parent material to be welded, wherein an arc “a” is generated between the parent material and a tungsten electrode rod disposed in a center position of the shielding nozzle in an atmosphere of the shielding gas, and wherein the parent material is melted by heat of the arc “a”, and wherein the constricting nozzle comprises:

• (a) a cylindrical nozzle body disposed around a forward end of the tungsten electrode rod and concentrically with the tungsten electrode rod, and the cylindrical nozzle body defines an annular high-speed gas passage between the cylindrical nozzle body and an outer peripheral surface of the forward end of the tungsten electrode rod;
• and
• (b) a cylindrical spiral metal piece that is inserted in an inside of a forward end of the nozzle body, wherein the cylindrical spiral metal piece holds the tungsten electrode rod by an inner peripheral surface of the cylindrical spiral metal piece in a center position of the nozzle body, and the cylindrical spiral metal piece has a plurality of spiral gas-flow regulating grooves formed on an outer peripheral surface thereof, wherein the spiral gas-flow regulating grooves regulate and swirl shielding gas flowing through the high-speed gas passage;
• wherein a portion of the shielding gas flowing through the torch body flows through the high-speed gas passage, and is changed by the spiral metal piece into a swirling high-speed regulated gas that is flowing faster than laminarized shielding gas discharged from the shielding nozzle, and the swirling high-speed regulated gas flows from an opening at a front end of the nozzle body toward surroundings of the arc “a.”