Wire rod is a hot rolled steel product classified its shape. It is a rolled alloy or plain carbon steel product, produced from a semi mainly billet. It has a round, rectangular or other cross-section. In case of rounds its diameter ranges from 5.5 mm to 14 mm. Wire rod is wound into coils and transported in this form. In case the diameter is higher the product is called ‘Bar in coil’. Fig 1 shows wire rod coil.
Fig 1 Wire rod coil
Wire rod coil is held in a unit with at least four steel straps in the transverse direction and transported and stored without further packaging. Before the steel strapping is applied, the wire rod must be sufficiently compressed. The strapping is fixed in the transverse direction with a single circumferential strap so that the strapping does not slip and cause the coil to come apart.
Wire rod coils must be handled carefully owing to its sensitivity to mechanical damage. Damage may be prevented by correct handling and the use of suitable handling and slinging equipment (e.g. crossbars, C hooks, coil mandrels, webbing slings, chain slings). Lifting or setting down the wire rod coils with excessive force results in distortion, which is detrimental to further processing. The permissible loading capacity of the slinging and handling equipment and the lifting capacity of the lifting gear must also be taken into account. If the metal strapping is damaged or broken, the wire coils loosen and may result in tangled wire rod or other damage. Loosened wire rod coils result in problems during handling and during unrolling prior to further processing.
Wire Rod is used for many products. It is the raw material for the wire drawing units. Different uses of wire rod include wire ropes, springs electrodes, barbed wires, steel reinforcement for Aluminium conductor and prestressed concrete, wire mesh, fasteners, automobile components and hardware manufacturers. The major usage of wire rods are described below:
- Mild steel wire rod – Mild steel wire rod is made of steel having lower carbon. Its carbon content is less than 0.22%. It is used for manufacturing of various kinds of steel wires, nails and wire entanglement.
- Spring steel wire rod – The main usage of spring steel quality wire rod is for coil springs and stabilizer bars. There are two types of spring steels: coil spring and torsion bar produced through hot forming and used for automobile suspension system; and wire spring made by cold forming and used for electronics, precision machinery and furniture. Wire rod for springs must have high elasticity limits to prevent plastic deformation. It must also possess defect free surface to ensure high fatigue limits and good dimensional precision for improved operation.
- Bearing steel quality wire rod – Bearing steel quality wire rod requires a high degree of durability to withstand repeated loads and high speed rotations during operation. This type of wire rods are used in a variety of industrial machine parts, including ball bearings and ring bearings.
- Carbon steel wire rod for cold heading quality (CHQ)– Plain carbon steel wire rod for cold heading quality is cold headed, forged or extruded to make bolts, nuts or screws used widely in automobile parts and industrial machines. This quality of steel needs strict quality control since the steel is placed under severe working conditions and used for special purposes. Hence it should be handled with utmost care to prevent surface flaws.
- Wire rod for core wire of covered electrodes – The wire rod slow cooling operation and the technical specification deviation control are carried out to guarantee rod drawability. Precise component control is required to ensure weldability and deposit metal quality. The rods are used for general welding electrode wire, for CO2 gas shielded arc welding wire and for submerged arc welding wire.
- High carbon steel wire rod – High carbon steel wire rod needs the micro structure of fine pearlite to maintain its high strength and to ensure its wire drawability. This steel is used in wire ropes, precision springs, bead wires. It is also as reinforcement wires for prestressed concrete.
- Wire rod for tire cord – This quality of wire rod is drawn to 0.4-0.15mm. Tire cords are usually made from high carbon steel wire rods. Steel cord is used to reinforce the durability of automobile tires. This type of wire rod requires particularly clean and high strength steel.
- Wire rod for high strength steel (HSS) – This Prestressed concrete bar type steel is used in reinforcing the concrete in telegraph poles and piles. Structural carbon steel containing traces of boron, or a large amount of silicon, undergoes high frequency heat treatment to produce this quality of wire rods. Compared with mild steel, this type of steel has higher elastic limits and lower relaxation.
- Free cutting carbon steel wire rod– In this type wire rod is made from free cutting steel where free cutting elements such as P, Pb, Bi and S are added. This steel type of wire rod is used in precision parts of automobiles and in components of home appliances.
- Wire rod for piano wire – These wire rods are often used for production of high strength bead wire, Low relaxation pre stressed concrete (LRPC) steel wire and music wire. This quality of wire rod is made from high carbon steel with excellent filamentary drawability, high strength and fatigue resistance.
- Alloy steel wire rod for machine structural use – Wire rods made from this steel is mainly used for the joints of mechanical parts, such as high strength bolts and nuts. It is also used for the delivery of driving force. It is normally alloy steel having high strength due to the addition of alloying elements such as chromium, nickel and molybdenum etc.