Steel
It is a kind of material with various shapes, sizes and properties required by ingots, billets or steel products through pressure processing.
Steel is an essential material for national construction and the realization of the four modernizations. It has a wide range of applications and varieties. According to different section shapes, steel is generally divided into four categories: profiles, plates, pipes and metal products. In order to facilitate the organization of steel production, ordering and supply, and do a good job in business management, it is also divided into heavy rail, light rail, large section steel, medium section steel, small section steel, steel cold-formed section steel, high-quality section steel, wire rod Medium and thick steel plate, sheet steel, silicon steel sheet for electrical engineering, strip steel, seamless steel pipe, welded steel pipe, metal products, etc.
Converter steelmaking
The molten iron transported from the torpedo car can be poured into the converter as the main charge after desulfurization, slag blocking and other treatment, and less than 10% scrap steel can be added. Then, oxygen is blown into the converter for combustion. The excess carbon in the molten iron is oxidized and gives off a large amount of heat. When the probe measures that the predetermined low carbon content is reached, the oxygen blowing is stopped and the steel is drawn. Generally, deoxidation and composition adjustment are required in the ladle; Then put carbonized rice husk on the surface of molten steel to prevent the molten steel from being oxidized, and then send it to the continuous casting or mold casting area. For steel with high requirements, bottom argon blowing, RH vacuum treatment and powder spraying (Si-Ca powder and modified lime) can be added, which can effectively reduce the gas and inclusions in the steel and further reduce carbon and sulfur. After these refining measures outside the furnace, the composition can be finally adjusted to meet the needs of high-quality steel.
Blooming
The new process of hot charging and hot delivery is adopted for the mold cast ingots, which are heated in the soaking pit, and then rolled into slabs, tube billets, billets and other primary rolled products through the blooming mill and billet continuous rolling mill. After head cutting, tail cutting and surface cleaning (flame cleaning and grinding), high-quality products also need to be peeled and flaw detected for the primary rolled billets, which are warehoused after passing the inspection. At present, the products of the blooming mill include blooming slab, rolled square billet, steel billet for oxygen cylinder, round tube billet for gear, axle billet for railway vehicle and steel for plastic mold, etc. Blooming slab is mainly supplied to hot rolling plant as raw material; The rolled billets are mainly sent to the high-speed wire rod mill as raw materials, except for some of them. Due to the progressiveness of continuous casting slabs, the demand for blooming slabs has been greatly reduced, so they have turned to other products mentioned above.
Hot continuous rolling
Continuous casting slab or blooming slab is used as raw material, heated by walking beam furnace, descaled by high-pressure water, and then enters the roughing mill. The roughing material enters the finishing mill after head cutting, tail cutting, and then implements computer-controlled rolling. After final rolling, it passes through laminar cooling (computer-controlled cooling rate) and coiler coiling to become a straight coil. The head and tail of straight hair curls are often tongue shaped and fishtail shaped, with poor thickness and width accuracy. There are often wave shaped, folded and tower shaped defects at the edges. The coil weight is heavy, and the inner diameter of the steel coil is 760mm. (generally used in the pipe making industry.) After the straight hair coil is processed by head cutting, tail cutting, edge cutting, multi pass straightening, leveling and other finishing lines, it is then cut or rewound to become: hot rolled steel plate, flat hot rolled steel coil, longitudinal cutting strip and other products. If the hot-rolled finishing coil is pickled to remove the oxide skin and coated with oil, it will become hot-rolled pickled coil. This product has the tendency to partially replace the cold-rolled sheet, with moderate price, and is deeply loved by the majority of users.
Tandem cold rolling
The hot-rolled steel coil is used as raw material for cold continuous rolling after acid pickling to remove the oxide skin. The finished product is hard rolled coil. The cold work hardening caused by continuous cold deformation increases the strength and hardness of the hard rolled coil and decreases the toughness and plasticity index. Therefore, the stamping performance will deteriorate and can only be used for simple deformed parts. The hard rolled coil can be used as the raw material of the hot galvanizing plant because the hot galvanizing units are equipped with annealing lines. The weight of rolled hard coil is generally 6~13.5t, and the inner diameter of steel coil is 610mm.
Generally, continuous annealing (CAPL unit) or bell type furnace annealing shall be carried out for cold rolled plates and coils to eliminate cold work hardening and rolling stress, so as to meet the mechanical property indexes specified in corresponding standards.
The surface quality, appearance and dimensional accuracy of cold-rolled steel plate are better than those of hot-rolled steel plate, and its product thickness is right rolled to about 0.18mm, so it is favored by the majority of users. Taking cold-rolled steel coil as the base plate for deep processing of products, it has become a high value-added product. Such as electro galvanizing, hot galvanizing, fingerprint resistant electro galvanizing, color coated steel coil, vibration damping composite steel plate, PVC coated steel plate, etc., which make these products have good quality such as beauty and high corrosion resistance, and have been widely used. Cold rolled steel coil must be finished after annealing, including head cutting, tail cutting, edge cutting, leveling, leveling, rewinding, or longitudinal shear plate. Cold rolled products are widely used in automobile manufacturing, home appliances, instrument switches, construction, office furniture and other industries. The weight of each bundle of steel plates after bundling is 3~5 tons. The weight of flattening coil is generally 3~10 tons / coil. The inner diameter of steel coil is 610mm.
Most steel processing is through pressure processing, so that the processed steel (billet, ingot, etc.) produces plastic deformation. According to the processing temperature of steel, there are two types: cold processing and hot processing. The main processing methods of steel include:
Rolling: it is a pressure processing method that the metal blank passes through the gap (various shapes) of a pair of rotating rollers, and the material section is reduced and the length is increased due to the compression of the rollers. This is the most commonly used production method for producing steel, which is mainly used to produce profiles, plates and pipes. It is divided into cold rolling and hot rolling.
Forging: a pressure processing method that uses the reciprocating impact force of the forging hammer or the pressure of the press to change the blank into the shape and size we need. It is generally divided into free forging and die forging. It is often used to produce large-scale materials and materials with large section sizes such as billet.
Pulling: it is a processing method that the rolled metal billets (shapes, tubes, products, etc.) are pulled into sections through die holes to reduce the length and increase. It is mostly used for cold processing.
Extrusion: it is a processing method that puts the metal in a closed extrusion cylinder and applies pressure at one end to extrude the metal from the specified die hole to obtain finished products with the same shape and size. It is mostly used to produce non-ferrous metal materials