Date: 2025/5/12
Category: Metallurgical encyclopedia terms
Views: 136
Definition: In the steel industry, the long process is a traditional steel production process that includes ironmaking, steelmaking and steel rolling. It uses iron ore, coke and other main raw materials, first in the blast furnace to make iron, get hot metal, and then the hot metal after pretreatment in the converter or electric furnace to make steel, produce a variety of steel products, and finally enter the steel rolling process to become the final product.
Process Flow
1.Ironmaking Process:
Raw material preparation: The first is the preparation of iron ore. After a series of pretreatment such as crushing, screening and beneficiation, iron ore is mixed with coke, sinter (or pellets) in a certain proportion. Coke is mainly used as a reducing agent and heat source, sinter (or pellets) is the iron ore after sintering (or pellets) process, its purpose is to improve the metallurgical properties of iron ore.
Blast furnace ironmaking: the mixed raw materials are loaded from the top of the blast furnace, and the hot air is blown in from the bottom of the blast furnace. Inside the blast furnace, the coke burns to produce high temperatures and carbon monoxide gas, which acts as a reducing agent to reduce the iron oxide in the iron ore to iron. The reaction formula mainly includes (coke combustion), (Budol reaction), (iron oxide reduction) and so on. Molten iron accumulates at the bottom of the blast furnace and is discharged from the outlet regularly. At the same time, the generated blast furnace gas is discharged from the top of the furnace and can be used as fuel for other processes after purification treatment.
2.Steelmaking Process
Hot metal pretreatment: Hot metal from the blast furnace usually contains sulfur, silicon, phosphorus and other impurities, need to be pre-treated. For example, the use of desulfurization, desiliconization, dephosphorization and other processes to reduce the content of these impurities to meet the quality requirements of steelmaking.
Converter steelmaking (or electric furnace steelmaking): after pretreatment, the hot metal enters the converter, and at the same time, the scrap steel and slag making agent are added. In the converter, the carbon, manganese, silicon and other elements in the hot metal are oxidized by blowing oxygen into the converter, and the heat generated by the oxidation reaction is used to melt the scrap steel and adjust the composition of the liquid steel. The reaction is as follows. If it is electric furnace steelmaking, it mainly uses electric energy to generate heat to melt raw materials, and the proportion of waste steel used in electric furnace steelmaking is relatively high. After steelmaking is completed, the liquid steel goes through refining, continuous casting and other processes, and finally forms various steels.
3.Steel Rolling Process
First, the billet is heated by the reheating furnace, and after the heated billet is descaled (the surface of the oxide scale is removed), it is rolled into the roughing mill for preliminary rolling, the billet is rolled into the intermediate shape, and then into the finishing mill for further rolling into the required size and precision of the finished product. For example, in the production of hot rolled strip steel, the intermediate blank of the rough-rolled strip steel is continuously rolled by the finishing mill group, and finally the hot rolled strip steel with uniform thickness and good surface quality is obtained.
Cold rolling usually takes the semi-finished product after hot rolling as the raw material, and goes through pickling (removing surface oxidation scale), cold rolling mill rolling, annealing (improving steel properties), smoothing (improving surface quality) and other processes. For example, in the production of cold-rolled sheet, the hot-rolled sheet enters the cold rolling machine after pickling, and the thickness of the sheet is thinned and the surface is smoother through multi-pass small reduction rolling, and then the high-quality cold-rolled sheet is obtained after annealing and leveling.
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