Factors Affecting Gauge Uniformity of Flat Cold Rolled AHSS

摘要

Development of AHSS grades and their growing production are accompanied by tightening of the quality standards including shape and dimension requirements for flat coated/annealed products. One of the difficulties in meeting these requirements is related to macroscopic variations in cold rolled strip thickness (gauge) that lead to substantial out of gauge tolerance portions of coils. This cold band gauge defect (GD) originates from hot strip mill processing although the hot band gauge does not reveal any disturbances. The present work is aimed at quantifying the factors responsible for GD after tandem rolling. By means of statistical analysis of hot rolling data it is shown that GD manifestation and its severity strongly depend on hot rolling finishing and coiling temperatures, rolling speed and run-out table cooling conditions, all of which affect the type and kinetics of austenite phase transformation. Steel chemical composition was also found to produce an effect on GD. Reduction and elimination of GD may require fine tuning of hot rolling parameters as well as fine modification of steel composition.