Tham khảo tài liệu 'asm metals handbook - desk edition (asm_ 1998) episode 9', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Rolling. The traditional process for converting prime copper into wire rod involves hot rolling of cast wirebar. Almost all drawing stock is rolled to 8 mm in. diameter. Larger sizes up to 22 mm in. or more in diameter are available on special order. Some special oxygen-free copper wirebar is produced by vertical casting but most wirebar is produced by horizontal casting of tough-pitch copper into open molds. The oxygen content is controlled at to to give a level surface. Cast wirebars weigh 110 to 135 kg 250 to 300 lb each. The ends are tapered to facilitate entry into the first pass of the hot rolling mill. Prior to rolling bars are heated to 925 C 1700 F in a neutral atmosphere and then rolled on a continuous mill through a series of reductions to yield round rod 6 to 22 mm I to in. in diameter. The hot-rolled rod is coiled water quenched and then pickled to remove the black cupric oxide that forms during rolling. This method can produce rod at rates up to kg s 30 tons h . Disadvantages of this process include High capital investment to achieve low operating cost Relatively small coils that must be welded together for efficient production where the welded junctions present potential sources of weakness in subsequent wiredrawing operations Unsuitability of rod rolled from cast wirebars for certain specialized wire applications Continuous Casting. Because of the disadvantages inherent in producing rolled rod from conventionally cast wirebars processes have been developed for continuously converting liquid metal directly into wire rod thus avoiding the intermediate wirebar stage. Continuously cast wire rod has come to dominate the copper wire rod market and now accounts for more than 50 of the total amount of wire rod produced. Advantages of continuous casting and rolling include Large coil weights up to 10 Mg 11 tons Ability to reprocess scrap at considerable savings Improved rod quality and surface condition Homogeneous metallurgical .
