According to requirements of customers, steel plates, steel pipes and other steel products supplied here can be delivered at the following states:
No extra heat treatment to steel product after hot rolling or forging, steel plate or pipe is directly delivered after cooling, called hot rolled or hot forging. Final temperature range of the steel product is 800 ~ 960 ℃, generally cooled naturally in the air.
Hot rolling status is simply as normalizing treatment. The difference is that hot rolled final temperature is not steady, while normalizing is more strict at fire heating temperature control, the fluctuations of microstructure and properties of steel is bigger than normalizing.
Steel product produced by cold drawing, cold rolling or other cold forming process, could be directly delivered without any heat treatment is known as the cold drawn or cold rolled condition. Compared with the state of hot rolling, forging.
Cold drawing (rolling) state has the advantages of high dimensional accuracy, good surface quality, and have higher mechanical properties. But for steel surface has no oxidation skin coverage for steel product at cold drawing (rolling) delivery status, and has higher internal stress, it is vulnerable to corrosion or rust, so packaging, storage and transportation requires more strict conditions for steel plate or steel pipe of this delivery state, generally use warehouse storage, and temperature and humidity should be controlled within a normal range.
Normalize heat treatment temperature (hypo eutectoid steel: Ac3+30 to 50 °C, eutectoid steel: Accm+30 to 50 °C), temperature control is more strict than hot-rolled state, it has uniform performance.
Normalized state,compared with annealed state, due to rapid cooling process of normalizing, the number of pearlite in the microstructure of the steel increased, so it has higher comprehensive mechanical properties and can improve the low carbon steel of the widmanstatten structure and eutectoid cementite network form, it is used to prepare for further heat treatment.
Carbon steel, alloy steel are usually produced at normalizing delivery condition. Some high strength low alloy steel such as 14MnMoVBRE, 14CrMnMoVB steel, in order to obtain Bainite microstructure, also requires normalizing delivery condition.
The purpose of annealing is mainly to eliminate the legacy of tissue defects and improve internal stress, it's the pre-treatment for better organization and performance for after processes.
Alloy structural steel, cold heading steel, bearing steel, tool steel, turbine blade steel, heat resistant stainless steel steel products are commonly used annealing state delivery.
High tempering temperature is conducive to eliminate internal stress, improve the plasticity and toughness of carbon structure steel, alloy steel; quench hardenability structural steel are adopted with high temperature tempering state delivery.
Some high strength martensite stainless steel, high-speed tool steel and high strength alloy steel, high temperature tempering is often after quenching (or drawing) process, steel product of this delivery state has good machinability.
Solid Solution State:
Solid Solution State is mainly applied to the treatment of austenitic stainless steel. Single-phase austenite is obtained through solid solution treatment, in order to improve the toughness and plasticity of the steel, also prepare for further cold rolled or cold drawn processing.
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