Super Short Interval Multi-pass Rolling Process for Ultrafine-grained Hot Strip

• Published in: ISIJ International 2008/08/15, Vol.48(8), pp.1142-1147
• Main Authors: Etou, Manabu, Fukushima, Suguhiro, Sasaki, Tamotsu, Haraguchi, Youichi, Miyata, Kaori, Wakita, Masayuki, Tomida, Toshiro, Imai, Norio, Yoshida, Mitsuru, Okada, Yasutaka
• Format: Article
• Language: English
• Subjects: Applied sciences; cooling; C–Mn steel; Exact sciences and technology; ferrite transformation; grain refinement; grain size; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Metals. Metallurgy; multi-pass; rolling; rolling load; yield strength
• ISSN: 0915-1559; 1347-5460
• DOI: 10.2355/isijinternational.48.1142

As a process to manufacture ultrafine-grained hot strip or plate of which ferrite grain size was about 1 μm, heavy reduction hot rolling at relatively low temperature, such as larger than 70% reduction per pass at lower than 700°C, had been presented. However, it is quite difficult to apply the process to commercial production because the rolling load is very large. A new process of multi-pass rolling at extremely short interval has been proposed and developed in order to manufacture ultrafine-grained hot strip at ordinary rolling load. Authors named it “Super Short interval Multi-pass Rolling (SSMR) process”. Ultrafine-grained hot strip of 1.2 mm thick was successfully manufactured in laboratory with the simple chemical composition of 0.15%C–0.74%Mn. Its grain size was 0.9 μm at 50 μm beneath the surface and 1.2 μm on the average over the thickness. The rolling load in SSMR was smaller than 30 kN/mm and it was relatively small owing to relatively small reduction, smaller than 50% per pass, and relatively high temperature, higher than 820°C. Consequentially it was confirmed that the rolling load in SSMR process could be reduced to half compared to the previously presented process of heavy reduction hot rolling at low temperature.