METHOD FOR HEAT TREATING LONGER-LENGTH PRODUCT, METHOD FOR MANUFACTURING LONGER-LENGTH PRODUCT, AND HEAT TREATMENT FURNACE USED FOR SAID METHODS

摘要

Disclosed is a method which is for carrying out heat treatment on long material to be heat treated, and which uses a batch-type heat treatment furnace which is cylindrical in shape, and the inside of which has been divided into a plurality of heating zones along the length-wise direction thereof, and both ends of which have been blocked. The end-most sections of the heat treatment furnace are divided into a plurality of heating zones which are shorter in length than the heating zones which are not in the end most sections, and a heat source is disposed in every heating zone. The heat treatment method comprises a series of steps: in advance, determine the heating output pattern of each heat source in each heating zone in the end-most sections, on the basis of the results of actual measured temperatures during the heating of the end sections of the material to be heat treated (step one); individually control the heating output of the heat sources during the heat treatment of the material to be heat treated, on the basis of the heating output pattern of each heat source, as determined in step one, and the results of measuring the inside-furnace temperature of each heating zone in the end-most sections and the other heating zones (step two). This heat treatment method enables material to be heat treated to be accurately and evenly heated along the entire length thereof, even in heat treatment furnaces which do not have heat sources in both end walls.