Carbon steel pipes are made of an alloy of iron and carbon. They are widely used in various heavy industries because of their strong, durable and corrosion-resistant properties. Carbon steel pipes can not only withstand high pressures, but also have good oxidation resistance. The following introduces the specifications, manufacturing processes and applications of carbon steel pipes in various types of pipes.
Carbon steel pipe specifications and standards
The specifications of carbon steel pipes, such as outer diameter, wall thickness, and weight, usually follow the ASME B36.10 standard. Nominal pipe sizes can be expressed in millimeters and inches, while wall thickness is in millimeters. Standard pipes are identified by "nominal pipe size" (NPS), and the wall thickness of the pipe is defined by the "Schedule" (SCH).
Common pipe classification
Steel pipes can be divided into the following types according to manufacturing methods and uses:
Standard pipes
Standard metal pipes include welded pipes (such as ERW pipes), seamless pipes, and galvanized pipes. This type of pipe is mainly used for general engineering and construction applications, accounting for about 10% of all pipe products.
Line pipe
Mainly used in oil and gas transmission systems. Manufactured according to API 5L specifications, including ERW, FW, SAW and DSAW pipes. Common grades are X42, X50, X60, etc., accounting for 21% of all pipe products.
Oilfield Tubular Goods (OCTG)
This type of pipe is used for drilling and completion operations of oil and gas wells, including drill pipe, tubing and casing. Oilfield tubulars can be manufactured by ERW and seamless, accounting for 35% of all pipes.
Pressure pipe
Mainly used for industrial and high-pressure applications, manufactured by seamless process, accounting for 2% of all pipes.
Mechanical pipe
Used in mechanical structural applications, meets ASTM specifications, can be produced by
ERW pipe and seamless methods, accounting for 17% of the market share.
Structural pipe
Used for structural support or other construction purposes, can be round or square, mainly manufactured by ERW pipe, often used for fencing and building support, accounting for 15% of the market share.
Pipe Sizes and How to Measure The size of a pipe is usually identified by NPS (Nominal Pipe Size), while the wall thickness is defined by Schedule. NPS is a dimensionless index, and while it indicates the size of the pipe, it is not equivalent to the actual size. For example, the outside diameter of pipes from NPS 1/8 to NPS 12 is defined by ANSI standards. Within this range, the size of Schedule 40 pipe is approximately equal to its inside diameter. For larger sizes, such as NPS 14 and above, the outside diameter is easier to understand. For example, a 14 NPS pipe corresponds to an outside diameter of 14 inches (OD). The standards for different types of pipes are slightly different. For example, a 4.5" OD pipe in standard pipe is called 4" NPS, while it is simply called 4.5" in line pipe and OCTG.
Pipe Weight Calculation
The weight of steel pipe is usually expressed in pounds per foot or kilograms per meter. It should be noted that the pipe weight in the standard table is a theoretical value, and the actual weight may vary due to manufacturing tolerances. The formula for calculating the weight of steel pipe is as follows:
W=[{OD-WT} x WT] x 10.69
Where W is the weight per linear foot, OD is the outside diameter, and WT is the wall thickness.
Pipe Manufacturing Process
The manufacturing process of steel pipe is mainly divided into two categories: welded pipe and seamless pipe.
Welded pipe
Welded steel pipe is made by heating and welding steel strips or steel plates. The main welding methods are:
Furnace welding (FW): Also known as continuous weld.
Electric resistance welding (ERW): Uses electric current to pass through the contacting surfaces of steel plates to form a weld.
Submerged arc welding (SAW): includes single-sided or double-sided submerged arc welding, which is usually used for large-diameter pipes.
Seamless pipe (SMLS)
Seamless pipe is made by heating the steel billet, then piercing, stretching and forming it. It does not require welds, has higher strength and pressure resistance, and is often used in high-pressure applications.
Comparison of carbon steel pipe and stainless steel pipe
In addition to
carbon steel pipe, stainless steel pipe is also very common. The main difference between the two is the material composition and corrosion resistance. Stainless steel pipe is manufactured according to A312 specification, and common materials are 304 and 316. Stainless steel is often used in chemical, food processing and other environments requiring high corrosion resistance due to its stronger corrosion resistance.
Summary
Carbon steel pipes occupy an important position in construction, oil and gas, machinery and pressure applications due to their strength and durability. Depending on the application scenario, carbon steel pipes can be manufactured by welding or seamless, and there are many specifications and standards to choose from. Whether it is conventional structural applications or high-pressure needs in the oil and gas industry, carbon steel pipes can provide reliable solutions.
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