Six delivery of steel

1, hot rolling state
Steel in hot rolling or forging after no longer carry on the special heat treatment, cooling directly after delivery, known as hot rolled or hot forging, hot rolling (forging) the end temperature is 800 ~ 900 DEG C, after the general in the air natural cooling, and hot rolling (forging) state is equivalent to normalizing treatment. What is different is because the hot rolling (forging) end temperature high and low, unlike the normalizing temperature control strictly, and steel performance volatility than normalizing large organizations. At present, a lot of iron and steel enterprises use controlled rolling, because the final rolling temperature control is very strict, and after the end of rolling to take the forced cooling measures, thus the grain refinement, delivery steel has a higher comprehensive mechanical properties. No twist controlled cooling of hot-rolled coil than ordinary hot-rolled wire with superior performance is the truth, hot rolling (forging) delivery of steel, because the surface covered with a layer of iron oxide, which has certain corrosion resistance, storage and storage requirements as cold drawing (rolling) delivery of steel as strict, large and medium-sized steel, thick the plate can be in the open air or by covering storage yard.
2, cold drawing (rolling) state
Cold rolled, cold rolled steel products, without any heat treatment and direct delivery of the state, known as cold or cold state. Compared with hot rolling (forging) state, cold drawing (rolling) state of steel size precision and good surface quality, low surface roughness, and has high mechanical properties, due to cold drawing (rolling) no oxide covered steel surface state of delivery, and there are a lot of stress, vulnerable to corrosion or rust. The cold drawing (rolling) state of steel, its packaging and transportation have more stringent requirements, generally require storage in the warehouse, and should pay attention to control the temperature and humidity in the warehouse.
3, the normalized state
Before the steel factory is hot treatment, this delivery status is said to be normalized. The normalizing temperature is Accm+30 (Ac3+30, 50°, C, 50°), which is more strict than that of hot rolling, and the microstructure and properties of the steel are uniform. Compared with the annealed steel, because of normalizing the cooling speed and the number of pearlitic steel tissue increased, pearlite lamellar and steel grain refinement, which have higher comprehensive mechanical properties, and is conducive to the improvement of network cementite shaped low carbon steel structure and hypereutectoid steel, can organize well prepared for further heat finished processing. Carbon steel, steel bonded steel often used in the state of delivery. Some low alloy high strength steels, such as 14MnMoVBRE and 14CrMnMoVB steel, are required to be delivered in normalized condition in order to obtain bainite.
4, annealing state
Steel before the factory by annealing heat treatment, this delivery status is called annealing state. The main purpose of annealing is to eliminate and improve the process before left from the tissue defects and stress, and after the procedure for the preparation of microstructure and mechanical properties, alloy structural steel, ensure the hardenability of steel, cold heading steel, bearing steel, tool steel, steel, iron blade type stainless heat resistant cable the commonly used steel steel annealing delivery.
5, high temperature tempering state
Before the delivery of steel by high temperature heat treatment, which is called the state of high temperature tempering. High tempering tempering temperature is high, is conducive to the elimination of internal stress, improve plasticity and toughness, carbon structure, alloy steel, to ensure the hardenability of structural steel can be used in high temperature temper delivery. Some high strength martensitic stainless steel, high-speed tool steel and high strength alloy steel, the strengthening effect of high hardenability and alloy elements, often in quenching (or tempered) after a high temperature tempering, the carbide in the steel appropriate aggregation of carbide, coarse tempered sorbite structure (the spheroidizing, therefore, the similar organization) delivery state steel has good cutting performance.
6, solid solution state
The steel is treated by solid solution before delivery, the delivery state is called solid solution treatment. This state is mainly applicable to austenitic stainless steel before the factory. Through the solid solution treatment, the single phase austenite structure is obtained to improve the toughness and plasticity of the steel, and to create the conditions for further cold working (cold rolling or cold drawing), and also to prepare for the further precipitation hardening.