Steel pipe delivery status(condition)

Steel pipe delivery status(condition): cold / hard (BK), cold / soft (BKW), after cold stress relief annealing (BKS), annealing (GBK), normalized (NBK).

Hot-rolled condition

After hot rolling or forging of steel and no further special heat treatment, cooling directly after delivery, the state is called hot rolling or forging, hot-rolled (wrought) termination temperature is generally 800 ~ 900 ℃, generally in air after natural cooling, and thus hot-rolled (forged) status equivalent to normalizing. The difference is because of hot-rolled (forging) the termination of high and low temperatures, unlike normalizing strict temperature control heating and thus volatility in steel microstructure and mechanical properties than are well done. Currently many steel companies controlled rolling, because the finishing temperature control is very strict, and after finishing forced cooling measures taken thus grain refinement of steel, steel delivery have higher mechanical properties. No twisting controlled cooling of hot-rolled wire rod superior than ordinary hot-rolled wire rod performance is the truth, hot-rolled (forging) state delivery of steel, the surface is covered with a layer of iron oxide, which has a certain degree of corrosion resistance, storage custody Unlike the strict requirements as cold drawn (rolled) state of delivery of steel, medium-sized steel, thick steel plate can be stored in the open air yard or through thatch cover.

Cold drawn (rolled) condition

By cold drawing, cold-rolled steel products, such as cold forming, heat treatment and without any direct delivery of state called cold-drawn or cold-rolled condition. Compared with the hot rolling (forging) state, high dimensional accuracy cold-drawn steel (rolled) state, good surface quality, low surface roughness, and have a higher mechanical properties, due to the cold drawn (rolled) steel delivery status oxide surface is not covered, and there is a lot of stress, vulnerable to corrosion or rust, and thus steel cold drawn (rolled) state, its packaging, storage requirements are more stringent, generally need to be kept in the warehouse, and should pay attention to the temperature and humidity control coffers.

Normalizing condition

Former steel factory by normalizing heat treatment, the delivery status of said normalizing state. Since normalizing the heating temperature (hypoeutectoid steel as Ac3 +30 ~ 50 °C, eutectoid steel is Accm +30 ~ 50 °C) temperature control than hot-rolled termination strict, so the organization of steel, uniform performance. Compared with steel annealed condition, because normalizing cooling faster, increasing the number of organizations pearlite steels, pearlite lamellar and grain refinement of steel, and therefore have higher mechanical properties, and will help to improve widmanstatten low carbon steel and steel eutectoid cementite network, further heat treatment for the finished good organization and preparation. Carbon steel, alloy steel steel is often used normalizing the status of delivery.

Annealed condition

Former steel factory after annealing, this delivery condition is called annealed condition. Annealing main purpose is to eliminate defects and improve the organization and internal stress left before the procedure and after the procedure to prepare for the organization and performance, alloy structural steel, guaranteed hardenability structural steel, cold heading steel, bearing steel, annealed steel commonly used tool steel, turbine blade steel, heat-resistant stainless steel body cable delivery.

Tempering condition

Former steel factory by high temperature heat treatment, this condition is called tempering the delivery status. Tempering temperature is high, help eliminate stress, improve ductility and toughness, carbon structural steel, alloy steel, guaranteed hardenability structural steel for high temperature tempered condition can be delivered. Some high strength martensitic stainless steel, high speed tool steel and high-strength steel, due to the high hardenability and strengthening the role of alloying elements, often in the quench (or tempering) once after tempering, the steel carbides appropriate aggregation, coarse carbide particles get tempered sorbite organizations (organizations with similar goals annealing), and thus, the delivery status of the steel has good machinability.

State solution treatment

Former steel factory after solution treatment, this condition is called solution treatment delivery status. This state is mainly applied to austenitic stainless steel processing factory before. By solution processing, single phase austenite to improve the toughness of steel and plastic, to create conditions for further cold (cold-rolled or cold-drawn), but also make the organization prepare for further precipitation hardening.

Weled steel pipe specification, Standard and identification

Welded steel pipe (steel pipe manufactured with a weld) is a tubular product made out of flat plates, known as skelp, that are formed, bent and prepared for welding.