There are several types of steel wires

Cold-drawn steel wirefor fabricating tension zone reinforcement in prestressed concrete components. In general, concrete has high strength to compressive forces, but when subjected to tensile forces, it shows brittleness and is prone to cracking. Prestressed concrete is to make the steel bar configured in the tension zone of the component bear a tensile force in advance and generate pretensile stress. The pretensile stress on the reinforcement reacts to the precompressive stress of the tension zone to offset or reduce the tensile stress of the external load acting on the concrete, thereby greatly improving the ability of the tension zone to resist the tensile force, thus reducing the size of the component, saving materials and reducing the self-weight of the component. Because of these advantages, prestressed concrete components have been successfully used in many projects such as large bridges, roof Trusses, crane beams, industrial and civil prefabricated floor slabs, iron track sleepers, electric pole pipe piles, large-diameter prefabricated pipelines, and nuclear power stations. The production of prestressed steel wire has developed rapidly with the wide application of prestressed concrete components.

A general term for steel wiresmade of high-quality high-carbon steel hot-rolled Wire Rods by heat treatment and cold working for prestressed concrete reinforcement requirements. The carbon content of this type of steel wire steel is 0.65%~0.85%, and the sulfur and phosphorus content is less than 0.035%. The tensile strength of steel wire is generally above 1470MPa, and its strength level has gradually transitioned from 1470MPa and 1570MPa to 1670~1860MPa. The diameter of the steel wire is more than 3mm, and has gradually transitioned from 3~5mm to 5~7mm.
Prestressed steel wire from the 20s of this century began industrial production and application, after decades of development, has formed a series of products with different characteristics suitable for different objects, including cold-drawn steel wire, straightened tempered steel wire, low relaxation steel wire, galvanized steel wire and scored steel wire, etc. These products and the prestressed steel strands made from them have become the most widely used varieties of prestressed steel in the world.

Cold-drawn wire
High-carbon steel hot-rolled disc rod is drawn into a round steel wire after lead solution quenching. Its elongation is low because it is not straightened and tempered. The steel wire is delivered in rolls, and the disc diameter is 500~1000mm. It is mostly used for railway sleepers and concrete pressure water pipes. The diameter of cold-drawn steel wire produced in China is mostly 3mm, and a small number is 4mm and 5mm. During production, the steel grade and wire rod diameter are selected according to the specifications and performance requirements of the finished product, and the lead solution quenching is carried out before drawing, the line temperature is 890~930 °C, and the lead temperature is 460~500 °C. After isothermal quenching, the strength is increased to 1080~1180MPa, and the metallographic structure is transformed into a soxtenite structure with excellent comprehensive properties. In order to ensure the surface quality of the finished product and facilitate drawing, the quenched wire rod needs to be pickled, phosphated or coated.

Straightening the tempered steel wire
The cold-drawn steel wire is straightened and tempered. The straightening and tempering temperature is 460~500°C, and the main function is to eliminate the internal stress generated during drawing. Compared with cold-drawn steel wire, the yield strength of straightened tempered steel wire is improved, and the ductility and stress relaxation properties are improved. The product is supplied in large coils, with a diameter of 1.5~2m. It has good straightness after uncoiling, can be constructed in single root or bunch, and is widely used in the manufacture of various types of prestressed concrete components.

Low relaxation wire
Cold-drawn steel bars are stabilized (i.e., tempered under tension) and named after them to reduce stress relaxation. Stress relaxation is an important property of prestressed steel, that is, the stress loss of the tension element under the condition of maintaining a constant length, and its magnitude is expressed as the percentage value of the stress loss to the initial stress, which is called the relaxation rate. In engineering applications, the stress relaxation loss of prestressed steel accounts for a considerable proportion of the total prestress loss of structural components, so reducing the relaxation rate through stability treatment is an effective method to improve the performance of steel wire. The tension is 0.4~0.5σb and the tempering temperature is controlled between 350~400°C. Due to the slight strain of 0.9%~1.3% produced by the steel wire in the hot tension state, its ability to prevent dislocation transfer under the action of external force is improved, which is manifested by the significant increase in the elastic limit and yield strength of the steel wire, and the stress relaxation rate is reduced to 1/3~1/4 of the straightened tempered steel wire. Under the same conditions, the residual stress in the prestressed tendon can be increased by 10%~15%. Therefore, in the past ten years, the production and application of low relaxation steel wire have made great progress.

Galvanized steel wire
It is made by using hot-dip galvanizing process to coat the surface of prestressed steel wire with a zinc layer of 250g/m2~350g/m2. Because the prestressed steel wire is a cold-worked steel with high strength, the surface is susceptible to damage, and it is more sensitive to medium corrosion and stress corrosion than ordinary carbon steel. In particular, the steel wire has a small breaking area, and works under high stress for a long time, because it is affected by the material properties, compactness, defects, condensation, cracks under stress and the use environment of the structure, etc., the risk of stress corrosion cracking resulting in the failure of the prestressed component is very great. The galvanized layer can play an effective role in protecting the steel wire matrix. Galvanized steel wire is suitable for more seriously corroded engineering structures such as bridge cables and sewage pools.