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Some things you need to know about seamless carbon steel pipes

Brief introduction

Seamless carbon steel pipe, is made from ingots or solid billets that are perforated to form a burr tube, and then hot rolled, cold rolled or cold drawn. Seamless carbon steel pipe has an important position in China's steel pipe industry.

Production process

Seamless carbon steel pipe raw material is round pipe billet, round pipe billet to be cut and processed into a length of about 1 meter billet by the cutting machine, and sent to the furnace by the conveyor belt heating. The billet is fed into the furnace and heated at a temperature of about 1200 degrees Celsius.

The fuel is hydrogen or acetylene. Temperature control in the furnace is the key issue. After the round billet is discharged from the furnace, it is hollowed out by a pressure piercing machine. The more common perforating machine is the conical roller perforating machine, which has high productivity, good product quality, large perforation and expansion, and can perforate a variety of steel grades.

After perforation, the round billet is successively three rolled oblique rolling, continuous rolling or extrusion. After extrusion, the tube should be sized. Sizing machine through the conical drill bit high-speed rotation into the steel embryo perforation, the formation of steel pipe. The inner diameter of the steel pipe is determined by the length of the outer diameter of the sizing machine bit.

After sizing, the steel pipe enters the cooling tower and is cooled by spraying water, and after cooling, the steel pipe is straightened. Steel pipe is straightened and sent by conveyor belt to the metal flaw detector (or hydraulic test) for internal flaw detection.

If there are cracks, bubbles and other problems inside the steel pipe, they will be detected. The steel pipe quality inspection is followed by a strict hand selection. After quality inspection, the steel pipe is sprayed with paint with number, specification, production lot number, etc. and lifted into the warehouse by crane.

Classification of seamless carbon steel pipe

Seamless steel pipe is divided into two categories: hot-rolled and cold-rolled (dialed) seamless steel pipe.


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


Cold rolled (dialed) seamless steel pipe is divided into general steel pipe, low and medium pressure boiler steel pipe, high pressure boiler steel pipe, alloy steel pipe, stainless steel pipe, petroleum cracking pipe, other steel pipe, including carbon thin-walled steel pipe, alloy thin-walled steel pipe, stainless thin-walled steel pipe, shaped steel pipe. Hot-rolled seamless tube outer diameter is generally greater than 32mm, wall thickness 2.5-75mm, cold-rolled seamless steel tube diameter can be up to 6mm, wall thickness up to 0.25mm, thin-walled tube outer diameter can be up to 5mm, wall thickness less than 0.25mm, cold-rolled than hot-rolled high dimensional accuracy.

General seamless carbon steel pipe

It is made of 10, 20, 30, 35, 45 and other high-quality carbon knotted steel 16Mn, 5MnV and other low-alloy structural steel or 40Cr, 30CrMnSi, 45Mn2, 40MnB and other alloy steel hot-rolled or cold-rolled. 10, 20 and other low carbon steel made of seamless pipe is mainly used for fluid transmission pipeline. 45, 40Cr and other medium carbon steel made of seamless pipe is used to manufacture mechanical parts, such as The force parts of automobiles and tractors. Seamless steel tubes are generally used to ensure strength and crush test. Hot-rolled steel pipe is delivered in hot-rolled condition or heat-treated condition; cold-rolled is delivered in heat-treated condition.

Seamless steel pipe for low and medium pressure boilers

Used in the manufacture of various low and medium pressure boilers, superheated steam tubes, boiling water tubes, water-cooled wall tubes and superheated steam tubes for locomotive boilers, large smoke tubes, small smoke tubes and arch brick tubes, etc. Hot-rolled or cold-rolled (dialed) seamless steel tubes made of high-quality carbon structural steel. Mainly made of 10, 20 gauge steel, in addition to ensuring the chemical composition and mechanical properties to do the hydraulic test, rolled edge, flaring, flattening and other tests. Hot-rolled to hot-rolled state delivery, cold-rolled (dial) to heat treatment state delivery.

High-pressure boiler steel pipe

Mainly used in the manufacture of high pressure and above pressure steam boiler pipes, such as high-quality carbon structural steel, alloy structural steel and stainless heat-resistant steel seamless steel tubes, these boiler tubes are often at high temperature and high pressure work, tubes in the role of high-temperature flue gas and water vapor will also be oxidation and corrosion, so the steel pipe is required to have high lasting strength, high oxidation resistance, and has good organizational stability.

The use of steel grades are: high-quality carbon structural steel grades 20G, 20MnG, 25MnG; alloy structural steel grades 15MoG, 20MoG, 12CrMoG, 15CrMoG, 12Cr2MoG, 12CrMoVG, 12Cr3MoVSiTiB, etc.; rust heat-resistant steel commonly used 1Cr18Ni9, 1Cr18Ni11Nb high-pressure Boiler tube in addition to ensure the chemical composition and mechanical properties, to do the hydraulic test root by root, to be flaring, flattening test. Steel tube to heat treatment state delivery.

In addition, the finished steel pipe microstructure, grain size, decarburization layer also have certain requirements.

Seamless steel pipe for geological drilling and oil drilling

To explore the underground rock structure, groundwater, oil, natural gas and mineral resources, the use of drilling rigs to drill wells. Oil and natural gas extraction is even more inseparable from drilling, and seamless steel pipes for geological drilling and oil drilling are the main equipment for drilling, mainly including core outer pipe, core inner pipe, casing, drill pipe, etc. The working conditions are extremely complicated, and the drill pipe is subjected to stresses such as tension, pressure, bending, torsion and unbalanced impact load, as well as mud and rock abrasion.

Therefore, the pipe must have sufficient strength, hardness, wear resistance and impact toughness, steel pipe with "DZ" plus the number of a representative steel yield point, commonly used steel number DZ45 45MnB, 50Mn; DZ50 40Mn2, 40Mn2Si; DZ55 40Mn2. DZ55's 40Mn2Mo, 40MnVB; DZ60's 40MnMoB, DZ65's 27MnMoVB.

Petroleum cracking pipe

Seamless tubes for furnace tubes, heat exchanger tubes and pipelines in petroleum refineries. Commonly used high-quality carbon steel (10, 20), alloy steel (12CrMo, 15CrMo), heat-resistant steel (12Cr2Mo, 15Cr5Mo), stainless steel (1Cr18Ni9, 1Cr18Ni9Ti) manufacturing. In addition to the chemical composition and various mechanical properties of the steel pipe, but also to ensure the hydraulic pressure, flattening, flaring and other tests, and surface quality and non-destructive testing.

We offer various types of seamless carbon steel pipes, including rectangular seamless steel pipes, etc. If there is a demand, you can contact us at any time.