PRODUCTION OF HIGH CARBON COLD ROLLED STEEL STRIP

• Main Authors: FUKUI KIYOSHI, KIRIHATA ATSUSHI, MIYAZAKI HIDEAKI
• Format: Patent
• Language: English
• Published: 03.03.1998
• Edition: 6
• Subjects: ALLOYS; CHEMISTRY; FERROUS OR NON-FERROUS ALLOYS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUSMETALS OR ALLOYS; MAKING METAL MALLEABLE BY DECARBURISATION, TEMPERING OR OTHERTREATMENTS; METALLURGY; METALLURGY OF IRON; MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; TREATMENT OF ALLOYS OR NON-FERROUS METALS

PROBLEM TO BE SOLVED: To prevent the generation of seizing flaws in a steel strip by prescriging the conditions of annealing. SOLUTION: A hot rolled steel strip subjected to pickling and descaling is repeatedly subjected to soaking and slow cooling of executing soaking and holding for <=8Hr under heating to the Ac1 point to the Ac1 point +50 deg.C at a heating rate of 20 to 100 deg.C/Hr by using a bell-type batch annealing furnace in a gas atmosphere composed of >=75vol.% hydrogen, and the balance nitrogen and executing cooling to the Ar1 point or below at a cooling rate of <=50 deg.C/Hr for two times. In this way, the spheroidizing rate of cementite improves, and the production of a soft hot rolled steel strip is made possible. Then, it is subjected to cold rolling at 20 to 85% draft and is next subjected to finish annealing at 630 deg.C to directly below the Ac1 point by a bell-type batch annealing furnace. In this way, cold rolling strains are released to grow the crystal grains, by which a soft recrystallized texture can be obtd. As a result, the possibility of occuring seizing flaws can be solved.