RADIANT TUBE HAVING HIGH HIGH-TEMPERATURE OXIDATION RESISTANCE AND ITS MANUFACTURE

摘要

PROBLEM TO BE SOLVED: To improve the service life of a radiant tube laid in a heat-treating furnace for steel by increasing the high-temperature oxidation resistance of the tube. SOLUTION: A melt-sprayed film composed of Al or an Al-Si alloy containing 0.5-15 wt.% Si and having a thickness of 30-500μm is formed in a desired area (particularly, the area which receives high heat from a burner during combustion) on the internal surface of a radiant tube. An Al2 O3 coating film formed on the surface of the melt-sprayed film is highly compact and stable and effectively suppresses or prevents the oxidation loss of the tube. In addition, the melt-sprayed film is firmly adhered to and coupled with the base material of the tube due to an Al-Si alloy layer formed at the boundary between the base material and the film and does not readily comes off the base material even when a thermal impact is repeatedly applied. Therefore, the melt-sprayed film can stably maintain its function as a protective film over a long period.