Determination of the ferritic phase content after heating or cooling of a steel strip

摘要

The present invention relates to a method for determining the ferritic phase fraction xα after heating or during cooling of a steel strip (2) in a metallurgical plant. Moreover, the invention relates to an apparatus for carrying out the method. The object of the invention is to provide a method by which the ferritic phase content in the steel strip (2) online, can be determined quickly and with as much as possible means. This object is achieved by a method which comprises the following method steps: measuring a width w1 and a temperature T1 of the steel strip (2), wherein the steel strip (2) has a ferritic phase fraction xα1 during the measurements; - Heating or cooling of the steel strip (2), wherein in the steel strip (2) during heating at least partially a phase transition α → y from the ferritic state α in the austenitic state y and at least partially cooling a phase transition from the austenitic state y to the ferritic state y α takes place; Measuring a width w and a temperature T of the at least partially converted steel strip (2); Determining the ferritic phase fraction xα by where T0 is a reference temperature, and αα and αy are the linear thermal expansion coefficients of ferrite and austenite