A digital flying extensometer for temper rollins mills

STEEL STRIP is extremely hard after it has been cold rolled and it must then be softened by annealing. The next production process in the manufacture of tinplate is temper rolling. Temper mills are used to produce the desired surface finish in the strip with acceptable flatness plus the desired mechanical properties. The latter refers mainly to the elimination of a surface defect known as “stretcher-strain” markings which can occur in pressed-steel products. The tendency to this type of defect is directly related to the amount of yield-point elongation. If the steel can be subjected to a small amount of cold working this defect can be eliminated. The effect of various amounts of cold reduction upon the yield-point stress and the stress-strain relationship is shown in Fig. 1. It will be noted that with an extension of as little as 1.0% the yield point can be entirely suppressed.