JPS57207129A - Controlling method for temperature of continuous heat treatment furnace - Google Patents

Abstract

PURPOSE:To stabilize the quality after heat treatments and to improve heat treatment efficiency in the stage of heating upset steel pipes with a preheater and tempering the same in a continuous heat treatment furnace by controlling the temp. of the furnace with cumulative tempering parameters. CONSTITUTION:At the outlet end of a furnace 20, the M of an upset part A at the inlet end of the furnace necessary for obtaining a target cumulative tempering parameter (a function of a stagnation time and a heating temp.) M is operated. This M is converted to a temp. and the part A is heated with a preheater 10 so that it attains this temp. at the inlet end of the furnace. When a steel pipe is charged into the furnace 20, a device 40 controls the furnace temp. by the furnace temp. instruction in accordance with the set heat pattern of an operator 60. The operator 60 estimates the temps. at the part A and the pipe body part from the detected furnace temp. and tracks the respective M values from this and the stagnation time. It determines an average M value from both M values, and inversely operates the M necessary for obtaining the target M value at the furnace outlet under the current furnace temp. at plural arbitrary points in the furnace. This and said average M value are compared and if the difference thereof exceeds the prescribed value, the temps. in the respective zones of the furnace are changed by each one unit.