| 摘要 |
PROBLEM TO BE SOLVED: To shorten the piercing time. SOLUTION: Preheat oxygen and a combustion gas are fed into a passage 3 from a preheat oxygen opening 5b and a combustion gas opening 5c and are mixed. The mixed gas is blown out to the outer part from an opening end 3a formed by a taper outer face 1gt becoming gradually smaller toward the tip of an inner tip 1, a straight inner face 2ns of an outer tip 2 that is parallel to the center line O, and a taper inner face 2nt becoming gradually smaller toward the straight inner face 2ns so as to generate a preheat flame. During this time cutting oxygen is fed from a cutting oxygen opening 5a into a flow hole 1a and is blown off so as to cut a cut material. A flame core becomes untapered so as to improve the concentricity and the heating efficiency for the cut material by the preheat flame and drastically shorten the piercing time.
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