Patent ID: 7722728
Filing Date: 2010-05-25
Classification: C21D,C23C

Abstract:
1. A heat treatment method for supplying transforming gas and enriched gas inside a furnace and heat treating a workpiece inside the furnace, comprising the steps of: performing feedback control of carbon potential by operating a supply flow rate of the enriched gas based on carbon potential inside the furnace; stopping the feedback control at any one of before an opening of the furnace is opened, while the opening of the furnace is open and before an atmosphere outside the furnace begins to flow into the furnace, and after the opening of the furnace is opened and before the atmosphere outside the furnace begins to flow into the furnace, and increasing a supply flow rate of the transforming gas from a supply flow rate thereof immediately before the feedback control is stopped; and resuming the feedback control when a furnace pressure reaches a predetermined pressure after the opening of the furnace is closed, wherein the opening is a carry-out port for carrying out a workpiece from the furnace, wherein the predetermined pressure is the furnace pressure before the furnace opens, and wherein increasing the supply flow rate of the transforming gas prevents a decrease of the carbon potential inside the furnace.