Use of Inert Atmosphere Reduces Scaling of Induction-Heated Fording Stock: Part 1

摘要

Preheating billet and bar forging stock in fuel combustion direct flame furnaces results in significant metal loss through oxidation and scaling. Also, combustion products present in the furnace prevent the use of protective atmospheres; that is, to use a protective atmosphere in a fuel combustion furnace, the heating space has to be separated from the flame space through the use of a muffle, retort or radiant tubes, which create practical difficulties in preheating billets and bars for forging. Advancements in induction heating make it possible to use a protective atmosphere in preheating forging stock. Nitrogen, nitrogen-based atmospheres, argon and other atmospheres can be introduced into the inductor(s) to prevent or reduce oxidation and scaling of the material. The BOC Nitrogen Atmosphere System for induction heating was developed as an alternative to heating in air, which has disadvantages relative to scale formation. The selection of the atmosphere and flow rate is determined mainly by the following factors: centre dot Composition and surface condition of the material to be heated and forged centre dot Design, size and number of induction coils (inductors) and atmosphere circulation within coils centre dot Distance between the inductor (or the last inductor, if using more than one) and the forging press centre dot Availability and cost of the equipment and atmosphere gases