Seamless steel pipe

Seamless steel tube: The most evident feature of an SML steel pipe is that it has no welded seam and it can resist greater pressure. The production of hot-rolled seamless steel pipes has the characteristics of a complex production process, various specifications, and small batches.

In pipeline engineering, hot-rolled pipes are often used when the pipe diameter exceeds 57mm, and cold-drawn (rolled) pipes are often used when the pipe diameter is less than 57mm. SML is made of ordinary carbon steel, high-quality carbon steel, ordinary low-alloy steel, and alloy structural steel, and are used to make liquid pipelines or make structures and parts.

Seamless steel pipe specification

StandardASTM ISO 9000-2001, CE CERTIFICATE, BV CERTIFICATE, DIN17175,DIN1629
Material16Mn,Q345B,P92,15CrMO,Cr5Mo,10CrMo910,12CrMo
Thickness1mm-300mm
Outer Diameter10mm-1500mm
Section ShapeRound
Surface treatmentpre-galvanized, hot dipped galvanized, black, coated
Grade10#-45#, 16mn, A53-A369
CertificationISO9001
ApplicationStructure Pipe, Oil Pipe, the general structure, mechanical structure

Seamless steel pipe standard

DiameterThicknessWeight/1 meterDiameterThicknessWeight/1 meter
159415.2982010199.75
518.9912239.1
622.6414278.26
219421.219208179.92
526.399202.19
631.5210224.41
736.612268.7
841.6314312.79
273533.0410208199.65
639.519224.38
745.9210249.07
852.2812298.29
325539.4614347.31
647.216396.14
754.8918444.77
862.54122010298.39
970.1312357.47
1077.6814416.36
377654.8916475.05
763.87142012416.66
872.814485.41
981.6716553.96
1090.5162012475.84
426662.1414554.46
772.3316632.87
882.4618711.1
992.55182012535.02
10102.5914623.5
480670.1316711.79
781.6518799.87
893.1220887.76
9104.53202014692.55
10115.916790.7
529790.1118888.65
8102.7820986.4
9115.41221083.95
10127.99222016869.61
6308122.7118977.42
9137.82221192.46
10152.89241299.68
7208140.46242016948.52
9157.8181066.2
10175.09201183.68
8208160.19221300.96
9179.99241418.05

The production process of  seamless steel pipe

The production of hot-rolled seamless steel pipes can be divided into three stages, namely, steelmaking and continuous casting (tube billet production), tube rolling, and tube processing.

Steelmaking and continuous casting are carried out in steel mills, tube rolling is carried out in tube rolling mills, and tube processing is carried out in tube processing plants. The process flow of the steelmaking stage: steel scrap or sponge iron is made by electric furnace, continuous casting by continuous casting machine, and flame cut into solid billets with a certain cross-section and length. These billets are sent to the tube billet warehouse after passing the inspection. The process flow of the tube rolling stage: the tube blank is extracted from the tube blank library, sawed, and then heated, the heated solid tube blank is pierced, and further rolled into a steel tube with a certain size and specification.

The process flow of the pipe processing stage: some types of steel pipes (such as hydraulic support pipes, oil cracking pipes, etc.) rolled out by the pipe rolling mill can be directly provided to users for use. They are finished pipes, and these pipes are sent to the offline finished product warehouse; Some types of steel pipes are semi-finished pipes (such as oil casing pipes, high-pressure boiler pipes, etc.), which can be used after further processing, but sometimes according to the contract, the company also sells some semi-finished pipes, and these semi-finished pipes ready to be sold to users are sent to offline semi-finished products warehouse.

The remaining semi-finished products are sent to the intermediate warehouse. The pipe processing plant extracts semi-finished pipes from the intermediate warehouse and processes them into steel pipes with specifications, dimensions, and performance required by users. Before being sent to the casing line for processing, some types of steel pipes (such as N80 grade oil casing) need to be heat-treated, and some types of steel pipes (such as grade 20 fluid pipes) do not need to be heat treated.

The main features of the seamless pipe

1. High-pressure resistance: Seamless pipes with the same specifications have different optional wall thicknesses and a wide range of pressure applications. However, the working pressure of the air-conditioning water system can be competent with welded pipes. This is not the reason for selection.
2. Wide diameter: The number of welded pipes above DN100 is less, while the number of seamless pipes is more. This is a reason for selection.
3. Easy to construct: Seamless pipes are connected by welding and flanges. Large-diameter pipes are difficult to install with threaded connections. Large-diameter pipes are now installed in grooves, but this method is not suitable for air conditioning water systems. This is the second reason for selection.

The distinction between seamless pipe and welded pipe

Since the welded pipe uses the strip as the raw material, and the seamless pipe uses the solid billet as the raw material, the comparison between the two can be transformed into the comparison between the seamless tube and the strip.

Since the welding pipe forming process only bears a small part of the deformation, the shortcomings of seamless pipe production are cleverly avoided, and the low-cost strip is directly used as the raw material so that the production cost of welded pipe is lower than that of seamless pipe.

Limited by the welding performance, the material range of the pipes that can be produced by the welded pipe process is small, and most alloy steel pipes can only be produced by the seamless pipe process.

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