The various types of high strength hot rolled steel sheets for automotive use have been developed. The effects of hot rolling conditions, especially cooling condition and coiling temperature, on the mechanical properties and the flatness of hot strip are discussed. It was found that the cooling pattern during traveling on runout table as well as coiling temperature was important factor to obtain as-hotrolled dual phase steel sheet having the uniform properties.
The dual phase steel sheets have a lower yield ratio, high work hardening rate and good ductility, compared with conventional high strength steel sheets. Some examples of the application of these high strength steel sheets are also introduced.