Steelmaking Equipment

Definition of steelmaking: use oxidation method to remove impurities in pig iron and scrap steel, add an appropriate amount of alloying elements, so that it becomes a steel with high strength, toughness or other special properties, this process is called "steelmaking".

 

Significance of 2.0%C in iron-carbon phase diagram for iron-carbon alloys with carbon content ≤2.0%. High temperature: austenite, good thermal processing performance; Room temperature: mainly pearlite.

 

Why steel is made: Pig iron is not widely available. High carbon content: no austenite at high temperature; Poor performance: hard and brittle, poor toughness, poor welding performance, can not be processed; Many impurities: S, P, high content of inclusions.

 

Common elements in steel: five elements: C, Mn, S, P, Si (required). Other elements: V, Cr, Ni, Ti, Cu, etc. (according to steel grade). Reasons for existence: ① process limitations: S and P can not be completely removed; ② Raw material residue: scrap steel residual Cu, Zn; ③ Improve performance: Mn improves strength Al refines grain. Element content: ① National standard requirements: GB; ② Enterprise standard: enterprise self-determined; ③ Other national standards: SWRCH82B (Japan).

 

 

 

 

Mix molten iron with scrap steel, pour it into the converter and then blow oxygen, the furnace temperature rises to about 1600℃, the reaction in the furnace is very violent, like a volcanic eruption, the carbon and the main impurities are quickly burned off (manganese and silicon in the molten iron are oxidized, and the carbon in the molten iron is also oxidized into carbon dioxide). The whole process is only about 30 minutes, and no longer add any fuel, you can chain a furnace of steel, and even "negative energy steel" with this method of steel, the quality can be comparable to the open furnace steel, the time required is only 1/10 of the open furnace, the efficiency is very high. Converter steelmaking has become the main process of modern steel production. The quality of the product was further improved after the addition of off-furnace refining.

 

1. Main features of safe production of steelmaking

Iron contains C, S, P and other impurities, affecting the strength and brittleness of iron, etc. It is necessary to re-smelter the iron to remove the above impurities and add Si, Mn, etc. to adjust its composition. The process of resmelting molten iron to adjust its composition is called steelmaking.

The main raw materials for steelmaking are molten iron or pig iron with high carbon content and scrap iron. In order to remove impurities from the molten iron, oxidizers, deoxidizers, and slagging materials, as well as ferroalloys and other materials, are added to the molten iron to adjust the composition of the steel. After the iron or pig iron with high carbon content is added to the steelmaking furnace, the impurities in the iron water are oxidized and removed through the processes of oxygen blowing, adding ore and removing carbon, and finally the alloy is added to carry out alloying, and then the steel is obtained. There are three kinds of steelmaking furnaces: flat furnace, converter and electric furnace. Flat furnace steelmaking method has been gradually eliminated due to high energy consumption and poor working environment. Converter and flat furnace steelmaking is the first iron into the mixing furnace preheating, scrap steel into the converter or flat furnace, and then the mixing furnace of high-temperature iron into the converter or flat furnace with the mixing iron car, melting and heating, when the temperature is appropriate, into the oxidation period. Electric furnace steelmaking is in the electric furnace furnace steel all add cold scrap, after a long time of melting and warming, and then into the oxidation period.

 

(1) Melting process. Iron and scrap contain C, Mn, Si, P, S and other impurities, in the low-temperature melting process, C, Si, P, S is oxidized, even if the monomorphic state of the impurities into the chemosynthetic state of the impurities, in order to facilitate the further removal of impurities at a later stage. Oxygen comes from the rust in the charge (composition of Fe2O3-2H2O), iron oxide, added iron ore, as well as oxygen in the air and blowing oxygen. The oxidation process of various impurities takes place between the interface of the slag and the steel.

(2) Oxidation process. The oxidation process is a decarburization, dephosphorization, degassing, and impurity removal reaction that takes place at high temperatures.

(3) Deoxidation, desulfurization and steel production. At the end of oxidation, the steel contains a large amount of excess oxygen, by adding lump or powdered ferroalloys or multi-element alloys to the liquid steel to remove excess oxygen in the liquid steel, resulting in harmful gases CO is discharged with the furnace gases, and the resulting slag can be further desulfurized, i.e., slag and steel are strongly mixed with rinsing to increase the desulfurization reaction in the final steel discharge process.

(4) Refining outside the furnace. Steel smelted from the steelmaking furnace contains a small amount of gas and impurities, generally the steel is injected into the refining package, argon blowing, degassing, ladle refining and other processes, to get a purer steel.

(5) Casting. From the steelmaking furnace or refining furnace out of the pure steel, when its temperature is appropriate, the chemical composition is adjusted appropriately after the steel. Steel through the steel package off into the ingot mold or continuous casting machine, that is, to get the ingot or continuous casting billet.

 

Casting is divided into two ways: mold casting and continuous casting. Mold casting is also divided into the upper casting method and the lower casting method. On the casting method is the steel from the ladle through the casting mold of the upper mouth directly into the mold to form ingots. Lower injection method is to pour the steel in the ladle into the injection pipe, flow steel brick, steel from the ingot mold into the mold from the lower mouth. Steel solidifies in the mold to get the ingot. Steel ingot through the de-insulation cap into the rolling mill of even heat furnace heating, and then the ingot mold and other transported back to the steel mill for the whole mold work.

 

Continuous casting is the steel from the ladle into the intermediate package, and then poured into the cleaner. The steel is pulled out of the crystallizer by the billet puller at a certain speed through the cooling, after the second cooling and forced cooling, to be all cooled, cut into a certain size of continuous casting billet, and finally sent to the rolling shop.

 

2. The main safety technology of steel production

(1) Elbow or reducer pipe explosion prevention. Oxygen gun on the upper part of the oxygen pipe bend or reducer due to the flow rate, local resistance loss, such as slag in the pipe or degreasing is not clean, it is easy to induce high-purity, high-pressure, high-speed oxygen combustion. Should be improved through the design, prevent sharp bends, slow down the flow rate, regular blowing, cleaning filters, perfect degreasing and other means to avoid accidents.

(2) The prevention and control of tempering and combustion accidents. Low-pressure oxygen resulting in negative pressure oxygen tube, oxygen gun nozzle blockage, are prone to high-temperature melting pool gas produced by the inverted tank backfire, explosion accidents. Therefore, the oxygen pressure should be closely monitored. Multiple furnaces with oxygen, do not rush to use oxygen, so as not to cause pipeline backfire.

(3) Steam resistance explosion prevention. Due to operational errors caused by the oxygen gun back to the water is not accessible, the oxygen gun accumulated water in the molten pool of high temperature vaporization, preventing the entry of high-pressure water. When the vapor pressure inside the oxygen gun is higher than the limit of the strength of the gun wall becomes explosive.

(4) the possible hazards of blasting: explosion seismic wave; explosion shock wave; debris and flying block hazards; noise.

(5) safety countermeasures: First, heavy scrap blasting. Scrap steel must be carried out in the underground blasting pit, blasting pit strength should be large, and pressure relief holes, pressure relief holes around the establishment of columns to block the wall; the second is the demolition of the furnace blasting, limiting the amount of charge, control of blasting energy; the third is to take the necessary preventive and control measures.

 

3, Steel, iron, slag burn protection technology

Iron, steel, slag liquid temperature is very high, heat radiation is very strong, and easy to splash, coupled with the high temperature of the equipment and the environment, very easy to burn accidents.

(1) burns and its causes: equipment leakage, such as steelmaking furnace, steel tanks, iron tanks, iron mixing furnace overflow; iron, steel, slag liquid in contact with the physical and chemical explosions and secondary explosions occurring in the water; superheated steam pipeline through the leakage or exposed; change the direction of the flame of the flat furnace hearth and the direction of the exhaust gas out of the hot gas or flame; violation of the operating procedures.

(2) safety countermeasures: regular inspection and maintenance of steelmaking furnace, steel tanks, iron tanks, iron mixing furnace and other equipment; improve the safety and technical regulations, and strictly enforced; improve personal protection; easy to leak the flange, the valve should be regularly replaced.

 

4, Steel making plant lifting and transportation operation safety technology

Steelmaking process requires raw materials, semi-finished products, finished products need lifting equipment and locomotives for transportation, there are many dangerous factors in the transportation process.

(1) the existence of danger: lifting objects falling hurt; lifting objects collide with each other; iron and steel tipping hurt; vehicles hit people.

(2) Safety countermeasures: consider enough space when designing the plant; innovate the equipment and strengthen the maintenance; improve the operation level of the workers; and strictly abide by the safety production regulations.

 

5, Steelmaking production accident prevention measures and technology

(1) The safety requirements of steelmaking plant room. Should consider the structure of the steelmaking plant room can withstand high temperature radiation; has enough strength and rigidity, can withstand the steel ladle, iron ladle, ingots and billets, such as load and collision and will not be deformed; a spacious operating environment, good ventilation and lighting, conducive to the dissipation of heat and emission of fumes, to give full consideration to the safety requirements of the personnel operation.

(2) Explosion-proof safety measures. Steel, molten iron, steel slag and slag at the bottom of the steelmaking furnace are high temperature molten material, which will explode when it comes into contact with water. When 1 kg of water completely into steam, its volume to increase about 1500 times, the destructive force is very great. Steel plant because of molten material in contact with water explosion situation are: converter, furnace oxygen gun, converter hood, continuous casting machine crystallizer high and medium pressure cooling water leakage, penetration of molten material and explosion; steel furnace, refining furnace, continuous casting crystallizer water-cooled parts because of the return of the water clogging, resulting in the continuation of the heat caused by the explosion; steel furnace, steel tanks, iron tanks, tanks, intermediate slag cans leakage of steel, leakage of slag and dumping of the explosion; to the wet steel tanks, iron tanks, intermediate tanks, slag tanks filled with steel, iron, liquid slag explosion; to have wet waste and water pits, pits, slag pits in the hot tanks, slag, slag over the explosion caused by; to the steelmaking furnace to add wet material caused by the explosion; steel casting system leakage and wet ground contact with the explosion. The main measures to prevent the explosion of molten material in contact with water is to ensure safe water supply to the cooling water system, the water quality should be purified, no leakage; materials, containers, workplaces must be dry.

Hot Tags: steelmaking equipment, China steelmaking equipment manufacturers, suppliers, factory, Honing machines, seamless pipe, helical welding steel pipe, thionizer, jaw crusher, limestone kiln