Hot rolled wire rod
Hot-rolled wire rod is a round steel product produced through a hot-rolling process. Supplied in coils, it features high strength, good ductility, and excellent workability, making it widely used in construction, machinery manufacturing, and metal products. Materials include carbon structural steel (such as Q235 and Q355), high-quality carbon steel (such as 45 steel), and alloy structural steel (such as 20Cr and 40Cr). Diameters typically range from 5.5 to 20 mm, with coil weights of 1 to 3 tons. Depending on demand, it can undergo subsequent processing such as cold drawing, cold rolling, and forging. Compared to cold-rolled wire rod, hot-rolled wire rod has a higher yield strength (300-600 MPa) and a surface oxide scale, making it suitable for cold working or direct use in welded structures.
The production process for hot-rolled round wire rod requires strict control of rolling temperature and deformation. First, continuously cast square billets (120-150mm side length) are used as raw material and heated to 1050-1150°C in a walking-beam furnace to ensure optimal plasticity. The heated billets then enter the roughing mill, where they are rolled into round intermediate billets through multiple passes. The roughing process maintains a controlled reduction (20%-30% per pass) to prevent surface cracking. The intermediate billets then enter the intermediate and finishing mills, where alternating horizontal and vertical rolls bring the intermediate billets to the target diameter. The finishing rolling temperature is controlled at 800-900°C, and the rolling speed is 10-30m/s to ensure dimensional accuracy (diameter tolerance ±0.3mm). After rolling, the wire rod is water-cooled (cooling rate 10-20℃/s) to control the grain structure, then rolled into a disc by a coiler, and finally undergoes online flaw detection (eddy current testing) and mechanical property testing to ensure product quality.
In the construction industry, hot-rolled wire rod is a key material for reinforced concrete structures. In floor slabs and beams of ordinary civil buildings, Q235 wire rod, after cold drawing, is used as stirrups and structural reinforcement. Its excellent plasticity ensures the integrity of the concrete structure. The use of this material in a residential community project reduced steel usage by 10% and increased construction efficiency by 15%. High-strength wire rod (Q355) is used in the frame columns and shear walls of high-rise buildings. With a yield strength of ≥355 MPa, it can withstand greater vertical loads and horizontal seismic forces. Structural tests on a 30-story office building showed a 20% improvement in seismic performance in areas where high-strength wire rod was used. In bridge construction, prestressed concrete beams use low-relaxation wire rod, which generates prestress through tensioning, improving the beam’s crack resistance. This has extended the beam service life of a river-crossing bridge to over 50 years.
Hot-rolled wire rod is in high demand in the metal products and machinery manufacturing sectors. Wire rope and stranded steel are produced using 6.5-8mm Q235 wire rod, twisted into high-strength, load-bearing components through multi-filament twisting. An elevator manufacturer has achieved a 15% increase in breaking strength and a 10-year service life for wire ropes produced using this material. Standard parts (bolts and nuts) are manufactured using 45-gauge steel wire rod, which exhibits excellent strength after cold heading. Bolts from an automotive standard parts manufacturer achieve a tensile strength exceeding 800 MPa, meeting the requirements for high-strength connections. In spring manufacturing, 60Si2Mn wire rod, after cold rolling and heat treatment, achieves an elastic limit of 1200 MPa, increasing the fatigue life of products from an automotive suspension spring manufacturer by 30%.
With advancements in industrial technology, the performance and variety of hot-rolled wire rod are constantly evolving. Manufacturers have developed ultrafine-grained wire rod, which uses controlled rolling and cooling techniques to refine the grain size to below 10μm. This increases strength by 20% while maintaining excellent ductility, making it suitable for high-end metal products. To meet the needs of new energy vehicles, high-strength low-alloy wire rod (such as Q690) has been developed to reduce component weight while maintaining strength. For example, one electric vehicle manufacturer reduced the weight of its chassis springs by 15%. In the area of green manufacturing, scrap steel recycling and smelting processes are being used to reduce carbon emissions per ton of steel produced. A steel company’s wire rod production line has achieved a scrap steel utilization rate of 95%. In the future, with the development of prefabricated buildings and high-end manufacturing, hot-rolled wire rod will continue to develop towards higher strength and more precise dimensions, providing higher-quality raw materials for various industries.
