Seamless steel pipes are made of steel ingots or solid tube billets through perforation into capillaries, and then made of hot-rolled, cold-rolled or cold-drawn. The mold production company will use it to make mold steel. Seamless steel pipes are made of high-quality carbon steel or alloy steel, and are divided into hot-rolled and cold-rolled (drawn). Welded steel pipes are made of rolled steel plates and welded with butt or spiral seams. In terms of manufacturing methods, they are further divided into welded steel pipes for low-pressure fluid transportation, spiral seam electric welded steel pipes, direct coiled welded steel pipes, and electric welded pipes. Seamless steel pipes can be used for various liquid and gas pipelines, etc. Welded pipes can be used for water pipes, gas pipes, heating pipes, etc. From the perspective of diameter, those with <φ76 account for 35%, and those with <φ159-650 account for 25%. In terms of varieties, general-purpose pipes are 1.9 million tons, accounting for 54%; oil pipes are 760,000 tons, accounting for 5.7%; hydraulic struts and precision pipes are 150,000 tons, accounting for 4.3%; stainless pipes, bearing pipes, and automobile pipes total 50,000 tons. tons, accounting for 1.4%.

The raw material for rolling seamless steel pipes is a round tube blank, which is cut by a cutting machine into a billet with a length of about 1 meter, and sent to a furnace for heating through a conveyor belt. The billets are fed into the furnace and heated at about 1200°C. The fuel is hydrogen or acetylene. The temperature control in the furnace is a key issue. After the round tube blank is released from the furnace, it must be pierced by a pressure piercer. Generally, the more common punching machine is the conical roller punching machine. This kind of punching machine has high production efficiency, good product quality, large amount of perforation and expansion, and can wear a variety of steel grades. After perforation, the round tube blank is successively cross-rolled, continuously rolled or extruded by three rolls. After extrusion, the tube should be removed and sizing. The sizing machine rotates into the steel billet at high speed through the conical drill bit to punch holes to form steel pipes. The inner diameter of the steel pipe is determined by the outer diameter of the drill bit of the sizing machine. After the steel pipe is sizing, it enters the cooling tower and is cooled by water spray. After the steel pipe is cooled, it will be straightened. After straightening, the steel pipe is sent to the metal flaw detector (or hydraulic test) by the conveyor belt for internal flaw detection. If there are cracks, bubbles and other problems inside the steel pipe, it will be detected. After the steel pipe quality inspection, it must pass strict manual selection. After the quality inspection of the steel pipe, the serial number, specification, production batch number, etc. are sprayed with paint. And lifted into the warehouse by crane.

Specifications: The specifications of seamless steel pipes are expressed in millimeters of outer diameter * wall thickness. φ: 756MM; wall thickness: below 100MM

Classification of seamless steel pipes: seamless steel pipes are divided into two categories: hot-rolled and cold-rolled (dial) seamless steel pipes.

Structural steel pipe GB/T8162-99 Oil drilling steel pipe YB528-65 Fluid steel pipe GB/T8163-99

Marine steel pipe GB5312-85 Medium pressure boiler steel pipe GB/T3087-99 Petroleum sleeve steel pipe API5CT

Geological drilling steel pipe YB235-70 Automobile half shaft steel pipe GB3088-8 Chemical fertilizer special steel pipe GB6479-86

Hydraulic prop steel pipe GB173-98 Petroleum cracking steel pipe GB9948-88 Pipeline steel ASTMA53B/106B/API 5L B High pressure boiler steel pipe DIN17175 ST45.8-Ⅲ GB5310-95 20G

Seamless steel tubes are rolled from solid tube blanks after perforation.

Hot-rolled seamless steel pipes are divided into general steel pipes, low and medium pressure boiler steel pipes, high pressure boiler steel pipes, alloy steel pipes, stainless steel pipes, petroleum cracking pipes, geological steel pipes and other steel pipes.

In addition to general steel pipes, low and medium pressure boiler steel pipes, high pressure boiler steel pipes, alloy steel pipes, stainless steel pipes, petroleum cracking pipes, and other steel pipes, cold-rolled (pulled) seamless steel pipes also include carbon thin-walled steel pipes, alloy thin-walled steel pipes, Stainless thin-walled steel pipe, special-shaped steel pipe. The outer diameter of the hot-rolled seamless steel pipe is generally greater than 32mm, and the wall thickness is 2.5-75mm. The diameter of the cold-rolled seamless steel pipe can reach 6mm, and the wall thickness can reach 0.25mm. Cold rolling has higher dimensional accuracy than hot rolling.