Steel is widely used. According to the shape of the section, steel is generally divided into four categories: profiles, plates, pipes and metal products. In order to facilitate the production of steel products, order supply and management, it is divided into heavy rail , light rail, high-quality steel, wire,steel square bar, medium-thick steel, thin steel, electrical silicon steel sheet, large steel, medium steel, small steel, cold-formed steel, strip steel, seamless steel pipe, welded steel pipe, metal products and other varieties.
Delivery status of steel：
State The steel that has been cold-formed, such as cold-drawn or cold-rolled, is delivered in a cold-drawn or cold-rolled state without any heat treatment. Compared with the hot-rolled (rolled) state, the steel in the cold-drawn (rolled) state has high dimensional accuracy, good surface quality, low surface roughness, and high mechanical properties, and is delivered in a cold-drawn (rolled) state. The surface is free of scale covering, and there is a large internal stress, which is highly susceptible to corrosion or rust. Therefore, the steel in the cold drawn (rolled) state has strict requirements for packaging, storage and transportation, and generally needs to be stored in the warehouse. And should pay attention to the temperature and humidity control in the warehouse
Hot rolled condition
Steel is not heat treated after hot rolling or forging, and is directly delivered after cooling. It is called hot rolling or hot forging. The termination temperature of hot rolling (forging) is generally 800-900 ° C, and then generally in the air. Naturally cooled, the hot rolled (forged) state is equivalent to normalizing. The difference is because the hot rolling (forging) termination temperature is high or low, unlike the normalizing heating temperature control is strict, so the steel structure and performance fluctuations are larger than the normalizing. Many steel companies adopt controlled rolling. Since the final rolling temperature control is very strict and forced cooling measures are taken after the final rolling, the grain of the steel is refined, and the delivered steel has a high comprehensive mechanical property. This is the reason why the non-twist-controlled cold-rolled wire rod is superior to the ordinary hot-rolled wire rod. The steel that is delivered in the hot-rolled (forged) state has a certain corrosion resistance due to the surface covered with a scale of iron oxide, and is stored and transported. The requirements are not as strict as the steel delivered in the cold-rolled (rolled) state. Large and medium-sized steel and medium-thick steel plates can be stored in open storage yards or after being covered.
The steel is subjected to normalizing heat treatment before leaving the factory, and this delivery state is called a normalizing state. Due to the normalizing heating temperature (the sub-eutectoid steel is Ac3+30～50°C, the hypereutectoid steel is Accm+30～50°C), the temperature control is stricter than the hot rolling end temperature, so the microstructure and properties of the steel are uniform. Compared with the steel in the annealed state, the amount of pearlite in the microstructure of the steel increases due to the normalizing cooling rate, and the pearlite layer and the grain of the steel are refined, so that it has high comprehensive mechanical properties and is beneficial to improvement. The Wei’s structure of the mild steel and the cementite network of the hypereutectoid steel can be prepared for further heat treatment of the finished product. Carbon steel and consolidated steel are often delivered in a normalized state. Certain low-alloy high-strength steels such as 14MnMoVBRE and 14CrMnMoVB steels are also required to be delivered in a normalized state in order to obtain a bainite structure.
High temperature tempering
State The steel is heat-treated by high temperature tempering before leaving the factory. This delivery state is called high temperature tempering. The high tempering temperature of high temperature tempering is beneficial to completely eliminate internal stress and improve plasticity and toughness. Carbon structure, alloy steel and steel structure ensuring hardenability can be delivered in high temperature tempering state. Some martensitic high-strength stainless steels, high-speed tool steels and high-strength alloy steels are often subjected to high-temperature tempering after quenching (or tempering) due to high hardenability and strengthening of alloying elements. The medium carbides are properly aggregated to obtain a tempered sorbite structure with a coarse carbide particle (similar to the spheroidized annealed structure), and thus the steel in this delivery state has good cutting performance.
The steel is annealed and heat treated before leaving the factory. This delivery state is called annealing. The purpose of annealing is mainly to eliminate and improve the structural defects and internal stress left in the previous process, and to prepare for the organization and performance of the subsequent process, alloy structural steel, guaranteed hardenability structural steel, cold heading steel, bearing Steel, tool steel, steam turbine blade steel, iron wire type stainless steel heat-resistant steel.galvannealed steel sheet suppliers
State Steel is solution treated before leaving the factory. This delivery state is called solution treatment. This state is mainly applicable to the treatment of austenitic stainless steel before leaving the factory. Through solution treatment, a single-phase austenite structure is obtained to improve the toughness and plasticity of the steel, to create conditions for further cold working (cold rolling or cold drawing), and to prepare for further precipitation hardening.