Delivery status of steel

Hot rolled condition

Steel is no longer special heat treatment after hot rolling or forging, and is delivered directly after cooling, called hot rolling or hot forging state, the termination temperature of hot rolling (forging) is generally 800 ~ 900℃, and then it is generally cooled naturally in the air, so the hot rolling (forging) state is equivalent to normalizing treatment. The difference is because the hot rolling (forging) termination temperature is high and low, unlike the normalizing heating temperature is strictly controlled, so the fluctuation of steel structure and performance is larger than the normalizing. Many iron and steel enterprises use controlled rolling, because the final rolling temperature control is very strict, and take forced cooling measures after the final rolling, so the grain refinement of steel, steel delivery has a higher comprehensive mechanical properties. No twist control cold and hot rolled wire is superior to ordinary hot rolled wire performance is this reason, hot rolled (forged) state delivery of steel, because the surface is covered with a layer of oxide, so it has a certain corrosion resistance, storage and storage requirements are not as strict as cold drawn (rolled) state delivery of steel, large and medium-sized steel, medium thick steel can be stored in the open yard or after the cover

Cold drawing

The state of cold drawing, cold rolling and other cold processing steel, without any heat treatment and direct delivery, called cold drawing or cold rolling state. Compared with the hot rolling (forging) state, the steel in the cold drawing (rolling) state has high dimensional accuracy, good surface quality, low surface roughness, and high mechanical properties. Because the steel delivered in the cold drawing (rolling) state is not covered by oxide, and there is a great internal stress, it is easy to suffer corrosion or rust, so the steel in the cold drawing (rolling) state is easily corroded. Its packaging, storage and transportation have more strict requirements, generally need to be kept in the warehouse, and should pay attention to the temperature and humidity control in the warehouse.

Normalizing state

The steel is treated with positive fire before leaving the factory, and this delivery state is called normalizing state. Because the normalizing heating temperature (Ac3+30 ~ 50°C for hypoeutectoid steel, Accm+30 ~ 50°C for hypereutectoid steel) is strictly controlled than the hot rolling termination temperature, the structure and performance of the steel are uniform. Compared with annealed steel, due to the faster normalizing cooling rate, the amount of pearlite in the structure of the steel increases, the pearlite lamellar and the grain refinement of the steel, so it has higher comprehensive mechanical properties, and is conducive to improving the Weil structure of low carbon steel and the cementite network of hypereutectoid steel, which can prepare the organization for further heat treatment of the finished product. Carbon bonded steel, bonded steel steel is often delivered in normalizing state. Some low-alloy high-strength steels such as 14MnMoVBRE and 14CrMnMoVB steel also require normalizing delivery in order to obtain bainite structure.

Annealed condition

Steel is annealed before leaving the factory, and this delivery state is called annealed state. The purpose of annealing is mainly to eliminate and improve the organizational defects and internal stresses left over from the previous process, and to prepare for the organization and performance of the subsequent process, alloy structural steel, to ensure the hardenability of structural steel, cold heading steel, bearing steel, tool steel, turbine blade steel, iron wire type stainless heat-resistant steel steel commonly delivered in annealing state

High temperature tempering

The steel is tempered by high temperature heat treatment before leaving the factory, and this delivery state is called high temperature tempering state. The tempering temperature of high temperature tempering is high, which is conducive to completely eliminating internal stress, improving plasticity and toughness, and carbon structure, alloy steel, and structural steel to ensure hardenability can be delivered in high temperature tempering state. Some martensitic high-strength stainless steel, high-speed tool steel and high-strength alloy steel, due to high hardenability and the strengthening effect of alloying elements, often in quenching (or tempering) after a high temperature tempering, so that the carbide in the steel is properly gathered, the carbide particles are coarse tempered sortenite structure (similar to the nodulating annealing structure), so that the carbide particles are relatively large tempered sortenite structure. The steel in this delivery condition has good machinability.

Solution treatment

State Steel is treated by solution before leaving the factory, and this delivery state is called solution treatment state. This state is mainly suitable for the processing of Austenitic stainless steel before leaving the factory. Through solution treatment, the single phase austenitic structure is obtained to improve the toughness and plasticity of the steel, create conditions for further cold working (cold rolling or cold drawing), and prepare the structure for further precipitation hardening.