Cold drawn (rolled) seamless welded pipe: round tube billet → heating → perforation → head → annealing → pickling → oiling (copper plating) → multi-pass cold drawing (cold rolling) → blank tube → heat treatment → straightening → Hydraulic test (inspection) → mark → storage.
Hot rolling (extrusion seamless welded pipe): round billet → heating → perforation → three-roll cross-rolling, continuous rolling or extrusion → pipe removal → sizing (or reducing diameter) → cooling → billet → straightening → water pressure Test (or flaw detection) → mark → warehousing.
The following is an overview of the two welded pipe processes:
The cold-drawn welded pipe is made of hot-rolled steel coil as raw material, and is subjected to pickling to remove scale and then cold-rolled. The finished product is rolled hard roll. The cold work hardening caused by continuous cold deformation makes the strength and hardness of the rolled hard roll rise and tough. The plastic index is reduced, so the stamping performance will deteriorate and can only be used for parts that are simply deformed. Rolled hard rolls can be used as raw materials for hot-dip galvanizing plants because the hot-dip galvanizing units are provided with an annealing line. The hard roll weight is generally 6~13.5 tons, and the inner diameter of the steel coil is 610mm.
Generally, cold-rolled rolled sheets and coils should be subjected to continuous annealing (CAPL unit) or hood furnace annealing to eliminate cold work hardening and rolling stress, and achieve the mechanical properties specified in the corresponding standards.
The surface quality, appearance and dimensional accuracy of the cold-rolled steel sheet are superior to those of the hot-rolled sheet, and the thickness of the product is thinly rolled to about 0.18 mm, which is favored by the majority of users. Deep processing of products with cold-rolled steel coils as a substrate has become a high value-added product. Such as electro-galvanizing, hot-dip galvanizing, fingerprint-resistant electro-galvanizing, color-coated steel coils and vibration-reducing composite steel sheets, PVC laminated steel sheets, etc., so that these products have excellent quality, high corrosion resistance and other excellent quality, and have been widely used. Cold rolled steel coils must be finished after annealing, including cutting, tailing, trimming, leveling, leveling, rewinding, or longitudinal shearing. Cold rolled products are widely used in automobile manufacturing, home appliances, instrument switches, construction, office furniture and other industries. The weight of each package after the steel plate is 3 to 5 tons. The flat roll weight is generally 3 to 10 tons. The inner diameter of the coil is 610 mm.
The hot-rolled welded pipe is made of continuous casting slab or slab as raw material, heated by step-type heating furnace, descaled by high-pressure water and then enters the rough rolling mill. The rough rolling material passes through the cutting head and tail, and then enters the finishing mill to implement computer control. After rolling, after the final rolling, it is subjected to laminar cooling and coiling, and becomes a straight hair roll. The head and tail of the straight hair roll are often in the shape of a tongue and a fishtail. The thickness and width are inferior in accuracy, and the side has frequent defects such as a wave shape, a folded edge, and a tower shape. The weight of the coil is heavier and the inner diameter of the coil is 760 mm. (Generally, the tube industry likes to use it.) After the straight hair is wound through the cutting, cutting, trimming and multi-pass straightening, leveling and other finishing lines, then cutting or rewinding, it becomes: hot rolling Steel plates, flat hot rolled steel coils, slitting belts and other products. If the hot-rolled finishing rolls are pickled to remove scale and oiled, they are hot-rolled pickled rolls. This product has a tendency to partially replace cold-rolled sheets, and the price is moderate, which is very popular among users.
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