The steel skelp is unrolled and heated then passed through grooved rollers, which make the ends curl up and form the pipe shape. The unwelded pipe is passed through welding electrodes – the metal resists the current, which causes heat and molten pools where the edges come into contact with each other and that process forms the weld.
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HFI welding is similar to ERW but uses an induction coil to create the current. HFI welded pipe is considered more suitable for use in the oil and gas industry because the process creates a stronger and better quality weld that is more suitable for pipes under high fatigue and stress conditions.
Longitudinal submerged arc welding is a process in which the weld and the arc zone are “submerged” under a layer of fusible flux. LSAW pipe is formed from steel plates rather than coils and is used for pipes with diameters larger than 24 inches or that require a particularly high wall thickness.
Seamless pipe is made when square steel billets are heated and moulded into cylinder shapes called “rounds”. The round is heated to white-hot in a furnace and rolled under high pressure. As the billet stretches out a hole forms in the centre and a bullet-shaped piercer point is pushed through. Larger diameter pipes then go through the mandrel mill process where after piercing the pipe shell is rolled through a mandrel mill with mandrel bars inside. This process creates a more standard outside diameter (OD) and controlled wall thickness (WT). Smaller diameter pipes are made using the plug mill process.
All these types of pipe are in use throughout the oil and gas industry. Seamless pipes are popular because the lack of seam indicates fewer stress points and they have superior mechanical strength. They can also be formed into more precise and predictable shapes. Seamless pipes are significantly more expensive than welded pipes, however, and have long lead times, because they are made in very few places. Although the seam in a welded pipe creates a potential weak point constant advances in welding technology have improved quality enormously. Welded pipes also have more consistent wall thickness and much shorter lead times.
A steel pipe is steel with a hollow section and its length is much greater than its diameter or circumference. There are many steel grades and specifications of steel pipe products, and their performance requirements are also various. All these should be differentiated according to user requirements or changes in working conditions. Generally, steel pipe products are classified according to cross-sectional shape, production method, pipe material, connection method, plating characteristics, and use.
The Types Of Steel Pipes
According to the cross-sectional shape, it is divided into round, square, rectangular, and special-shaped steel pipes; according to the material, it is divided into carbon structural steel pipes, low-alloy structural steel pipes, alloy steel pipes, and composite steel pipes; according to the purpose, it is divided into transportation pipelines, engineering structures, Steel pipes for thermal equipment, petrochemical industry, machinery manufacturing, geological drilling, high-pressure equipment, etc.; according to the production process, it is divided into seamless steel pipes and welded steel pipes, among which seamless steel pipes are divided into hot-rolled and cold-rolled (drawn) Two types, welded steel pipes are divided into straight seam welded steel pipes and spiral seam welded steel pipes.
1. According To The Section Shape
Steel pipes can be divided into round steel pipes and special-shaped steel pipes according to their cross-sectional shape.
Special-shaped steel pipes refer to steel pipes with various non-circular cross-sections. Mainly include:
Square tube
Rectangular tube
Oval tube
Flat oval tube
Semi-circular tube
Hexagonal tube
Hexagonal inner tube
Hexagonal tube with unequal sides
Equilateral triangle tube
Pentagonal plum blossom tube
Octagonal tube
Convex tube
Double convex tube
Double concave tube
Multi-concave tube
Seed-shaped tube
Flat tube,
Rhombus tube
Star tube
Parallelogram tube
Ribbed pipe
Drop tube
Inner finned tube
Twisted pipe
Type B tube
D-type tube and multilayer tube, etc.
Steel pipes are divided into equal-section steel pipes and variable-section steel pipes according to the shape of the longitudinal section.
Variable cross-section (or variable cross-section) steel pipe refers to a steel pipe whose cross-sectional shape, inner and outer diameter, and wall thickness along the length of the pipe change periodically or non-periodically. Mainly include:
Outer tapered tube
Inner tapered tube
Outer stepped tube, inner stepped tube
Periodic section tube
Bellows
Spiral tube
Steel pipe with heat sink
Barrels with double lines, etc.
2. According To Production Method
Steel pipes can be divided into two categories according to production methods: seamless steel pipes and welded steel pipes. Welded steel pipes are referred to as welded pipes for short.
(1) Types Of Seamless Steel Pipes
Seamless steel pipes are made of high-quality carbon steel or alloy steel and are divided into hot-rolled and cold-rolled (drawn).
According to production methods, seamless steel pipes can be divided into:
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Hot-rolled seamless pipe
Cold drawn tube
Precision steel pipe
Thermal expansion tube
Cold spinning tube
Extrusion tube etc.
(2) Types Of Welded Steel Pipes
Welded steel pipes are formed by welding steel plates rolled into a tube shape with butt seams or spiral seams. In terms of manufacturing methods, they are divided into welded steel pipes for low-pressure fluid transportation, spiral seam electric welded steel pipes, direct coil welded steel pipes, and electric welded pipes.
According to different welding processes, welding forms, and end shapes, welded steel pipes can be divided into:
Furnace welded pipe
Electric welding (resistance welding) pipe
Automatic arc welded pipe
Longitudinal welded pipe
Two types of spiral welded pipe
Round welded pipe
Special-shaped (square, flat, etc.) welded pipes
Seamless steel pipes can be used for liquid pressure pipes and gas pipes in various industries. Welded steel pipes can be used for water pipelines, gas pipelines, heating pipelines, electrical pipelines, etc.
3. According To Pipe Material
Steel pipes can be divided into carbon pipes, alloy pipes, stainless steel pipes, etc. according to the pipe material (that is, steel type).
Carbon tubes can be divided into ordinary carbon steel tubes and high-quality carbon structural tubes. And alloy tubes can be divided into low alloy tubes, alloy structural tubes, high alloy tubes, and high strength tubes. Bearing tubes, heat-resistant and acid-resistant stainless tubes, precision alloy (such as Kovar) tubes, and high-temperature alloy tubes.
4. According To Connection Method
Steel pipes can be divided into smooth pipes (with no threads on the pipe ends) and threaded pipes (with threads on the pipe ends) according to the connection method of the pipe ends.
The threaded pipe is divided into the ordinary threaded pipe and pipe end thickened threaded pipe. And thickened threaded pipes can also be divided into threaded pipes such as external thickening (with external threads), internal thickening (with internal threads), and internal and external thickening (with internal and external threads).
According to the thread type, the threaded pipe can also be divided into ordinary cylindrical or conical thread and special thread. In addition, according to user needs, threaded pipes are generally delivered with pipe joints.
5. According To The Characteristics Of Plating
Steel pipes can be divided into clarinet (uncoated) and coated pipes according to the characteristics of the surface coating.
Coated pipes include galvanized pipes, aluminum-plated pipes, chrome-plated pipes, aluminized pipes, and other alloy-layer steel pipes. And coated pipes include outer-coated pipes, inner-coated pipes, and inner-outer coated pipes. The commonly used coatings are plastic, epoxy resin, coal tar epoxy resin, and various glass-type anticorrosive coating materials. Galvanized pipe is divided into KBG pipe, JDG pipe, threaded pipe, and so on.
6. According To Use
Steel pipe is not only used to transport fluids and powdered solids, exchange heat, and manufacture mechanical parts and containers, it is also an economical steel. The use of steel pipes to manufacture building structural grids, pillars, and mechanical supports can reduce weight, save metal by 20-40%, and can realize factory mechanized construction. Using steel pipes to manufacture highway bridges can not only save steel, simplify construction, but also greatly reduce the area of the protective layer, saving investment and maintenance costs.
Pipes for pipes. Such as seamless pipes for water, gas pipes, steam pipes, oil transportation pipes, and oil and gas trunk lines. Agricultural irrigation water taps with pipes and sprinkler irrigation pipes, etc.
Pipes for thermal equipment. Such as boiling water pipes and superheated steam pipes for general boilers, superheating pipes, large smoke pipes, small smoke pipes, arched brick pipes, and high temperature and high-pressure boiler pipes for locomotive boilers.
Pipes for the machinery industry. Such as aviation structural tubes (round tube, oval tube, flat oval tube), automobile half-shaft tube, axle tube, automobile and tractor structural tube, tractor oil cooler tube, agricultural machinery square tube, and rectangular tube, transformer tube and bearing Tube and so on.
Pipes for petroleum geological drilling. Such as oil drilling pipes, oil drill pipes (kelly and hexagonal drill pipes), drill stems, oil tubing, oil casing, and various pipe joints, geological drilling pipes (core pipes, casings, active drill pipes, drill stems), Press hoop, and pin joints, etc.).
Tubes for the chemical industry. Such as petroleum cracking pipes, chemical equipment heat exchangers and pipes, stainless acid-resistant pipes, high-pressure pipes for fertilizers, and pipes for transporting chemical media.
Other departments use tubes. Such as container tubes (tubes for high-pressure gas cylinders and general container tubes), tubes for instruments and instruments, tubes for watch cases, injection needles and tubes for medical devices, etc.
The Manufacturing Processes Of Steel Pipes
Steel pipes are divided into seamless steel pipes and welded steel pipes.
The production process of seamless steel pipes is to pierce a solid tube billet or steel ingot into a hollow capillary tube, and then roll it into a steel tube of the required size. The different piercing and rolling methods used constitute different methods of producing seamless steel pipes. The production process of welded steel pipe is to bend the tube blank (steel plate or strip steel) into a tube, and then weld the gap to form a steel pipe. The different forming and welding methods used constitute different methods of producing welded steel pipes.
Seamless steel pipes are mainly produced by hot rolling. The extrusion method is mainly used to produce low-plasticity high-alloy steel pipes or special-shaped steel pipes and composite metal pipes that are difficult to pierce. Cold rolling and cold drawing can continue to process hot-rolled tubes into small diameter and thin-walled steel tubes. The welding steel pipe process is simple, the production efficiency is high, the cost is low, and the product variety is expanding day by day.
1. The Manufacturing Processes Of Seamless Steel Pipes
Hot rolling
Pipe jacking
Squeeze
Cold rolling
Cold drawing
2. The Manufacturing Processes Of Welded Steel Pipes
Chain furnace welding
Continuous furnace welding
Resistance welding
Arc welding
Induction welding
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