Method for continuous annealing of metal strips

A method of increasing the rate of production of narrow strip in a continuous annealing furnace having heating and cooling sections and which was designed to anneal a wide strip at a given production rate for a given gauge, comprising the steps of

• providing a continuous annealing furnace with a heating zone having a plurality of gas jet heaters and a cooling zone having a plurality of gas jet coolers,
• heating and cooling said continuous strip in said heating and cooling zones to target temperature patterns for said strip, by convection with mixtures of gases consisting of hydrogen and nitrogen that are impinged against both sides of said strip through said gas jet heaters and gas jet coolers,
• monitoring the temperatures of said strip in said heating and cooling zones, and
• setting and adjusting ratios of the mixtures of the gases to control the heat transfer rate and to achieve and maintain the target temperature patterns for said narrow strip in said heating and cooling zones in response to a reduction in the material width of the strip below the width for which the annealing furnace was designed, thereby the permit substantially more rapid movement of a narrower strip through the furnace than was possible for a wider strip of the same gauge and to improve the production rate for the narrow strip.