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Steel production process
May 30, 2018

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Iron and steel: it is an alloy with Fe and C as its main constituent elements, and also contains Si, Mn, P, S and other impurity elements. Contains pig iron and steel. Pig iron: iron carbon alloy with high carbon content (wc>2.11%) and high content of impurity elements. Steel: the quality fraction of carbon is low (wc<2.11%), and the content of impurity elements is low in iron carbon alloy. Steel is generally of good toughness and is a commonly used metal material. Steel: ingot or billet are made into steel of various shapes and specifications by pressure.

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A, ironmaking

Iron refining: the process of reducing iron from ore

Ironmaking method: blast furnace ironmaking

Ironmaking materials: iron ore, coke, solvents, etc

The raw material

Iron ore: it is the main raw material for ironmaking, including magnetite "Fe3O4", hematite "Fe2O3" and lignite "2Fe2O3". "3H2O" and "FeCO3" of diamond mine. In addition to the compounds of iron, iron ore also contains compounds of silicon, manganese, phosphorus and sulfur, which are collectively called gangue

Coke: heat from burning provides heat source for ironmaking; Incomplete combustion of CO gas as a reducing agent, iron reduction from the ore

Flux: limestone (CaCO3), fluorite (CaF2). Its function is to combine with the gangue in iron ore to form low melting point, low density and good fluidity slag, so as to separate it from the iron liquid, so as to obtain more pure pig iron liquid

The blast furnace

The main products are pig iron, and the by-products are slag and furnace gas (see figure for smelting process and principle).

Pig iron

Steel-making pig iron: the quality fraction of silicon is low (wSi<1.25%), and the fracture is silver-white, mainly used in steelmaking

Cast pig iron: high quality fraction of silicon (wSi>1.25%~3.2%), gray-black fracture, used as casting raw material

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Second, the steelmaking

The essence of steelmaking: it is to reduce the content of carbon and impurity elements in pig iron by oxidation, so as to make it reach the standard components and properties.

Raw materials for steelmaking: raw iron, scrap steel, flux (limestone, etc.), deoxidizer (silicon iron, manganese iron, aluminum, etc.), alloy, etc.

Steelmaking process: mainly including oxidation, slag, deoxidation, etc.

Steelmaking methods: at present, the main steelmaking methods are oxygen top blown converter steelmaking and electric furnace steelmaking.

Oxygen top-blown converter steelmaking: mainly iron liquid as raw material, add the right amount of scrap steel, its characteristic is high productivity, save energy, low cost, suitable for large-scale integrated iron and steel enterprises, the main production of various kinds of general purpose of alloy steel (carbon steel)

Electric furnace steelmaking: electric arc furnace steelmaking, induction furnace steelmaking and other methods, commonly used is electric arc furnace steelmaking. It USES converter steel and scrap steel as raw materials, iron ore and pure oxygen as oxidizer, and provides heat source for smelting with the arc heat between electrode and metal furnace material. Arc furnace smelting high temperature (2000 ℃), smelting alloy steel containing high melting point alloy elements; Because of the purity of the furnace materials, the smelting process is easy to adjust, the chemical composition is easy to control, and it can smelt high quality steel and alloy steel.

Casting of steel: the process of solidifying molten steel into ingots or billets. According to the deoxygenation degree of steel, it can be divided into sedative steel and fluidized steel.

Calm steel: steel that is fully deoxidized. The steel structure of sedation is dense and the performance is good. The ingot head needs to be removed during processing to reduce the rate of finished products

Effervescent steel: steel that is not adequately deoxidized. Fluidized steel ingot has many air holes, loose tissue and poor performance compared with calm steel. But high rate of finished products, rolled sheet surface quality

Semi - killed steel: steel with deoxygenation between sedative steel and fluidized steel

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Iii. Steel production

Types of steel: steel plate, section steel, steel pipe, steel wire, etc.

Production methods: mainly include rolling (cold rolling and hot rolling), drawing, extrusion, forging and other methods.

Steel plate: rolled steel ingot or billet into steel plate. Steel plate can be galvanized, tin - plated, lead - plated, plastic composite surface treatment

Medium thickness plate: 5mm; The thickness of the middle plate is 3~5mm, generally hot-rolled

Thin plate: the thickness is less than 3mm, and the blank is medium and thick plate of hot rolling. Cold rolling is adopted

Steel tape: coil supply, cold rolling

Section steel: it is rolled by a section mill. There are round steel, square steel, flat steel, hexagonal steel, octagonal steel, i-steel, channel steel, Angle steel, t-steel, etc. Ordinary section steel is mainly used for building, bridge, vehicle, etc., high quality section steel is mainly used for mechanical parts, tools, etc

Steel wire: made of hot rolled wire (coil rod) with diameter of 6~9mm. Annealed low carbon steel wire can be used to bind objects or woven into various articles. High carbon steel wire can be made into various springs, or twisted into strands of wire rope and cable, used for sling, wire, cable, fixed objects, etc.

Steel pipe: seamless pipe and welded pipe.

Seamless pipe: the pipe is made by cold drawing or hot rolling after the solid steel billet is perforated by inclined rolling piercing machine. Seamless steel pipe is mainly used in petroleum, chemical and other industries

Formed by rolling steel sheet or strip, then welded. Sewing steel pipe is widely used, mainly for water pipe, gas pipe and so on