METHOD FOR PRODUCING STEEL-MADE HOT-WORKED PRODUCT HAVING HIGH STRENGTH AND STRENGTH GRADIENT

• Main Author: OFUJI YOSHIHIRO
• Format: Patent
• Language: English
• Published: 20.09.2012
• 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 provide a method for producing a steel-made hot-worked product having high strength and strength inclination and also having excellent machinability by which high strength, strength gradient and reduction in production cost are achieved.SOLUTION: Raw material made of steel having chemical composition containing the specific amounts of C, Si, Mn, P, S, Al, V, N, and the balance Fe with impurities is subjected to treatments of the following steps (1) to (3) successively: (1) after heating the whole of raw material to 750 to 950°C, a rough-formed product is obtained by a hot-working; (2) the portion having ≤50% of the volume of the obtained rough-formed product is heated to 1,100 to 1,300°C at an average heating speed of ≥5°C/sec, and thereafter, the hot-working for finish-formation is started and this hot-working is finished within 15 sec after completing the heating, then the portion finish-formed by the hot-working is cooled to 600 to 480°C at an average cooling speed of 1.5 to 30°C/sec to obtain the finish-formed product; and (3) the obtained finish-formed product is held for 250 to 3,600 sec with a heat treatment furnace having an in-furnace temperature of [1,090-the temperature after cooling]°C to [1,190-the temperature after cooling]°C.