Steel finishing is the last process in the process of rolling steel production, and it plays a final role in ensuring the quality of the products to a certain extent. The content of the finishing process varies depending on the technical requirements of the product. Generally, the steel must be cut off or rolled, cooling, straightening, finishing, heat treatment, surface cleaning, inspection and packing, weighing, marking and other specific processes.
1) steel cutting: finished products need to cut the head and tail (cut off irregular part of head and tail) and cut the ruler. During rolling, rolling process is carried out smoothly, and the workpiece needs to be cut off. Commonly used cut-off equipment is WeChat photo _20180412165807_ copy.
Parallel blade shearing machine: usually used for transverse hot shear square and rectangular sections; oblique blade shears: usually used for cold shear and hot shear steel, strip, thin slab, welded pipe, etc.
Sometimes used for cutting small wood; flying shears: rolling pieces mainly used for transverse shear movement; disc shears: a class of longitudinal shear used for steel and strip, and a class for small, wire.
Sawing machine: commonly used for sawing steel pipes and shaped materials; flame cutting: commonly used for cutting thickness > fifty mm thick plate.
2) cooling after rolled steel: according to the chemical composition of the steel, the state of the tissue, the size of the product section, the possible defects after cooling, the rolling mill output and the cooling site, the different cooling methods are adopted respectively.
Undefinedundefined
Air cooling: natural cooling in the air. It is often used for cooling after low carbon steel, ordinary low alloy high strength steel, most carbon structural steel and alloy structural steel.
Fast cooling: that is to use blast, spray, spray water, no pressure layer water cooling and other sudden cooling to a certain temperature and then natural cooling. It is often used to cool the steel bar required for checking carbide mesh defects and after rolling of common carbon steel wire rod.
Slow cooling: the forthcoming rolled steel or steel in a slow cooling pit, a movable cold box or on the ground, covered with sand, asbestos slag and so on. It is often used in high speed tool steels, martensitic stainless steels, some high alloy tool steels and high alloy structural steels.
Natural cooling equipment is mainly a different type of cold bed: a cold bed with steel rope drawing machine: mostly used for large and medium steel; a cold bed with chain conveyor: the steel pipe and strip that are used for the surface of the rolling mill; the rack type cold bed is mainly used for small steel which is prone to bend and twist during the cooling process. In addition, there are hook conveyors, which hang the wire rods and transport them on the side while cooling, mainly for wire rods.
3) steel straightening: after rolling steel rolled steel, due to the unequal cooling of the rolled steel and other obstacles and after rolling, the bending, ladling or end torsional deviation often occur. It is necessary to straighten the steel through straightening equipment, such as pressure straightener, tension straightener and roller straightening machine, etc. Plastic section of material section.
Undefined
4) finished product heat treatment: through the heating, thermal insulation, cooling method, according to the different heating, thermal insulation, cooling curve, annealing steel, normalizing, quenching, tempering treatment to improve the steel structure, thus obtaining the required performance.
If steel is heated and insulated according to a specific heating and thermal insulation curve, it is quickly cooled in water or oil, that is, the quenching treatment can improve the strength and hardness of the steel, and increase the wear resistance. If the quenched steel is reheated to a certain temperature range below 723 centigrade, and then cooled in the oil or air, that is, the tempering treatment can reduce or completely eliminate the internal stress produced when the steel is quenched, reduce the brittleness of the hardened steel, and get better fit of toughness and strength.
5) inspection of the finished product
Most of the products are on-line ultrasonic and magnetic flux leakage testing (NDT), on-line hydraulic test for steel tube products, and various mechanical tests, heat treatment test, corrosion resistance test, metallographic analysis and chemical composition analysis.
About the author