Classifications

• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D7/00—Modifying the physical properties of iron or steel by deformation
  • C21D7/13—Modifying the physical properties of iron or steel by deformation by hot working
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21B—ROLLING OF METAL
  • B21B28/00—Maintaining rolls or rolling equipment in effective condition
  • B21B28/02—Maintaining rolls in effective condition, e.g. reconditioning
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
  • C21D9/38—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for roll bodies

Definitions

• This invention relates to the production of forged rolls for hot-rolling by regenerating refused malleable rolls.
• rolls for use in hot-rolling rolls are manufactured by casting or forging steel materials and then subjecting the materials to the heat treatment in an electric furnace or gas-heating furnace and thereafter to a machining treatment to obtain the desired dimensions, and usuallythe rolls are so designed that they may be used so long as they are worn off about of the maximum diameter of thereof.
• This allowable range of use is a result of the difliculty in the rolling operation and the fault in the quality of the section of the roll deeper than this range. Rolls worn off over this range have been usually scrapped as refused rolls.
• the idea of the present invention is to salvage the refused rolls to be scrapped.
• An object of this invention is, therefore, to regenerate reusable rolls from thus refused hot-rolling rolls, that is, the object of this invention is to provide a process of regenerating rolls having excellent wear resistance and other mechanical properties from the above-mentioned refused rolls.
• Another object of this invention is to provide a process for making rolls having almost the same or even better qualities than those of fresh rolls from refused malleable rolls by subjecting them to improved forging and heat treatments.
• Still another object of this invention is to reduce remarkably the manufacturing cost of rolls.
• a refused malleable roll that is, refused cast roll or forged roll, which has no defects in the inside thereof as will exert deleterious effects on the subsequent treatments, is used as a material.
• the refused roll is thinly chipped at its surface to remove small scratches or other defects on the surface which would disturb the subsequent forging treatment.
• the roll After the roll has been thinly chipped, it is subjected to a heat treatment prior to a forging treatment.
• the heating treatment the roll may be treated as in a conventional method of producing normal fresh forged rolls. That is, it may be heated up to 800 C. at a heating rate of 20 C. per hour and held at this temperature for 24 hours at the first stage and thereafter heated up to the forging temperature of about 1,000 C. at heating rate of 40 C. per hour and held at this temperature for 8 hours at the second stage.
• the ice heat treatment may also be conducted much more quickly than in the conventional method. That is, it may be heated to 600 C. at a heating rate of 100 C. per hour and held at this temperature for 10 hours at the first stage, then further heated to 900 C.
• the heating treatment of the present invention may be conducted for a period of time less than half of the time required for the conventional method.
• the thus heat-treated roll is subjected to a forging treatment, but the method of the present invention is characterized in that a light forging treatment is sufficient. That is, a reduction ratio of section area, expressed by the ratio section area before forging: section area after forging may be 1.1 to 1.4.
• a roll having almost the same or even better qualities than those of fresh rolls can be obtained from refused rolls. That is, the hardness suitable for the rolling conditions can be easily obtained and at the same time the various properties required in a fresh roll, such as, wear resistance, anti face-coarsening properties, thermal cracking resistance, and toughness can be obtained.
• the economical advantage of the process is very great.
• the manufacturing cost of the thus generate-d roll by the process of this invention as described in the below-stated examples can be reduced about 35% as compared with that of a fresh roll.
• the roll was heated by increasing the heating temperature gradually at a rate of C./hr. to 600 C., maintained at the temperature for 10 hours. The temperature was then increased to 900 C. at a rate of 100 C./hr. and the roll was maintained at the temperature for 5 hours. Thereafter, the roll was heated to 1,130 C. by increasing the temperature at a rate of 90 C./hr. and maintained at the temperature for 4 hours.
• the roll was heated to 730 C. by increasing the temperature at a rate of 50 C./hr., maintained at the temperature for 10 hours, cooled in furnace to 680 C., and then after maintaining at the temperature for hours, cooled in furnace to 200 C.
• the roll was chipped roughly and then subjected to the following refining treatment, that is, after maintaining at 900 C. for 5 hours, the roll was spray-quenched down to 500 C., the temperature was increased to 550 C. and the roll was maintained at the temperature for hours and then cooled in furnace to conduct tempering.
• Example 2 In this example, the process of this invention was applied to a refused cast steel roll of a high carbon containing alloyed steel (MnCrNiMo).
• Heating The above-treated roll was heated to 800 C. in an electric furnace by increasing the temperature at a rate of 20 C./hr., maintained at the temperature for 24 hours and then sent to a forging step wherein the roll was heated to a forging temperature.
• the roll was maintained for 20 hours at 500 C., for 30 hours at 880 C., for 15 hours at 450 C., for 30 hours at 810 C., cooled to 600 C. at a rate of 10 C./ hr., and then cooled in furnace.
• the roll was preheated by increasing the temperature to 460 C. at a rate of 20 C./hr. and maintaining at the temperature for 24 hours, heated to 900 C. by increasing the temperature at a rate of 20 C./hr., maintained at the temperature for 15 hours and then forcibly cooled by air. Further, the roll was heated to 600 C. by increasing the temperature at a rate of 20 C./hr., maintained at the temperature for 15 hours and cooled in furnace to conduct tempering.
• Example 1 The surface and intermediate section of the roll Example 2 T.S. section, Hs 46-48 B.S. section, Hs 45 (ii) Structures of the roll (Examples 1 and 2):
• the tensile strength of the roll which had been processed in Example 1 was as follows:
• the numeral 1 stands for the surface portion
• 2 stands for a section of Mt inner towards the center from the surface
• 3 stands for a section intermediate between the center and the surface
• 4 stands for the surface of the non-forged portion.
• a process of regenerating a refused malleable roll to a forged roll which comprises heating the refused roll to a forging temperature of about 1,000 C., then subjecting said heat-treated roll to a forging treatment and thereafter subjecting the forged roll to the same heat treatment as that of a fresh forged roll.
• a process of regenerating a refused malleable roll to a forged roll which comprises chipping slightly the surface of the refused roll, heating said roll to 800 C. at a heating rate of 20 C. per hour and holding it at this temperature for 24 hours; further heating the roll to 1,000 C. at a heating rate of 40 C. per hour and holding it at this temperature for 8 hours; thereafter subjecting the heat-treated roll to a forging treatment to reduce the diameter of the roll at the reductiori ratio of 1.1 to 1.4 and finally subjecting said roll to the same heat treatment as that of a freshly forged roll.
• a process of regenerating a refused malleable roll to a forged roll which comprises chipping slightly the surface of the refused roll, heating said roll to 600 C. at a heating rate of 100 C. per hour and holding it at this temperature for 10 hours; further heating the roll to 900 C. at a heating rate of 100 C. per hour and holding it at this temperature for 5 hours; further heating the roll to nearly the forging temperature at a heating rate of C. per hour and holding it at this temperature for 4 hours, thereafter subjecting the roll to a forging to reduce the diameter of the roll at the reduction ratio of 1.1 to 1.4 and finally subjecting the roll to the same heat treatment as that of a freshly forged roll.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Crystallography & Structural Chemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Heat Treatment Of Articles (AREA)
• Reduction Rolling/Reduction Stand/Operation Of Reduction Machine (AREA)
• Forging (AREA)

Applications Claiming Priority (1)

Publications (1)

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ID=12470994

Family Applications (1)

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Cited By (1)

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Citations (1)

• 1966
  • 1966-06-16 DE DE19661303401D patent/DE1303401B/de active Pending
  • 1966-06-16 GB GB26845/66A patent/GB1153714A/en not_active Expired
  • 1966-06-17 US US558246A patent/US3471340A/en not_active Expired - Lifetime

Patent Citations (1)

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