A brief guide to different types of carbon steel pipes

A brief guide to different types of carbon steel pipes

The manufacturing process of pipe is determined by the material, diameter, wall thickness, and quality for a specific service. Carbon steel piping is classified according to the manufacturing methods as follows:

  • Seamless
  • Electric resistance weld (ERW)
  • Spiral-Submerged arc weld (SAW)
  • Double submerged arc weld (DSAW)
  • Furnace weld, butt-welded or continuous weld

Seamless Steel Pipe

Seamless pipe is formed by piercing a solid, near-molten, steel rod, called a billet, with a mandrel to produce a pipe that has no seams or joints. Figure below depicts the manufacturing process of seamless pipe.

ERW Steel Pipe

ERW pipe is made from coils that are cupped longitudinally by forming rolls and a thin-pass section of rolls that brings the ends of the coil together to form a cylinder.

The ends pass through a high-frequency welder that heats the steel to 2600 °F and squeezes the ends together to form a fusion weld. The weld is then heat-treated to remove welding stresses and the pipe is cooled, sized to the proper OD, and straightened.

ERW pipe is produced either in individual lengths or in continuous lengths that are then cut into individual lengths. ERW is supplied according to ASTM A53 and A135 and API Specification 5L.

ERW is the most common type of manufacturing process due to its low initial investment for manufacturing equipment and the process’ adaptability in welding different wall thicknesses.

The pipe is not fully normalized after welding, thus producing a heat-affected zone on each side of the weld that results in non-uniformity of hardness and grain structure, thus making the pipe more susceptible to corrosion.

Therefore, ERW pipe is not as desirable as SMLS pipe for handling corrosive fluids. However, it is used in oil and gas production facilities and transmission lines, after normalized or cold expanded, for 26″ (660.4 mm) OD and larger lines.

SSAW Steel Pipe

Spiral-welded pipe is formed by twisting strips of metal into a spiral shape, similar to a barber’s pole, then welding where the edges join one another to form a seam. This type of pipe is restricted to piping systems using low pressures due to its thin walls.

SAW or DSAW pipe ?

SAW and DSAW pipes are produced from plate (skelp’s), which are either formed into a “U” and then an “O” and then welded along the straight seam (SS) or twisted into a helix and then welded along the spiral seam (SW). DSAW longitudinal butt joint uses two or more passes (one inside) shielded by granular fusible materials where pressure is not used.

DSAW is used for pipe greater than 406.4 mm nominal. SAW and DSAW are mechanically or hydraulically cold expanded and are supplied according to ASTN Specifications A53 and A135 and API Specification 5L. It is supplied in sizes 16″ (406.4 mm) OD to 60″ (1524.0 mm) OD.

LSAW Steel Pipe

LSAW (LSAW) in leaflets plate as raw material, the steel plate in the mold or molding machine pressure (volume) into using double-sided submerged arc welding and flaring from production.

A wide range of the finished product specifications, weld toughness, ductility, uniformity and dense, with a large diameter, wall thickness, high pressure resistance, low-temperature corrosion resistance, etc.. Required steel pipe in the construction of high-strength, high toughness, high-quality long-distance oil and gas pipelines, mostly large diameter thick wall LSAW.

API standard provisions, in the large-scale oil and gas pipelines, when 1, Class 2 areas through the alpine zone, the bottom of the sea, the city densely populated area, LSAW only applied specifically casts.

The difference between hot rolled and cold rolled steel pipe

The difference between hot rolled and cold rolled steel pipe

The difference between hot rolled and cold rolled steel pipe

The difference between hot rolled and cold rolled steel pipe mainly depends on the temperature of rolling process. If it is over the recrystallization temperature, this process is called hot rolled; while if it is below the recrystallization temperature, this process is called cold rolled.

 

Process flow:

Hot rolled (extruded) seamless steel tube : round solid billet → heating → perforation → three-high cross rolling, continuous rolling or extrusion → tube stripping → sizing (or reducing) → cooling →billet tube→ straightening → hydraulic test (or flaw detection) → marking → storage.

Cold rolled (drawn) seamless steel tube: round solid billet → heating → perforation → heading → annealing → pickling → oiling (copper plating) → multi-pass cold drawn (cold rolled) → billet tube→ heat treatment → straightening → hydrostatic test (flaw detection) → marking → storage.

 

Products under different processes have different characteristics.

Hot Rolled Seamless Steel Pipe 

Advantages: it can destroy the casting structure of ingot, refine the grain of steel, and eliminate the defects of microstructure, so that the steel structure is compact and mechanical properties are improved. This improvement is mainly reflected in the rolling direction, so that the steel is no longer isotropic to some extent; Bubbles, cracks and porosity formed during pouring can also be welded together under high temperature and pressure.

Disadvantages: After hot rolling, the non-metallic inclusions (mainly sulfide, oxide, as well as silicate) inside the steel are pressed into thin sheets, resulting in lamination (interlayer). Lamination greatly degrades the tensile properties of the steel along the thickness direction and may lead to interlayer tearing during weld shrinkage.The local strain induced by weld shrinkage often reaches several times of the yield point strain, which is much larger than the strain induced by load. Residual stress caused by uneven cooling, is the internal self-phase equilibrium stress under the action of no external force. The hot rolled steel section of all sections have this kind of residual stress, the larger the section size of the general section, the larger the residual stress. Although the residual stress is self-phase equilibrium, it has a certain effect on the performance of steel members under the action of external forces. For example, it may produce adverse effects on deformation, stability, anti- fatigue and other aspects. For hot-rolled steel products, it is difficult to control the thickness and side width.We are familiar with thermal expansion and cold contraction. Even if the length and thickness of the hot rolling reach the standard at the beginning, there will still be a certain negative difference after cooling. The wider the negative difference is, the thicker the thickness will be. So for large steel, it can not be too accurate in steel side width, thickness, length, angle, and edge line.

 

Cold Rolled Seamless Steel Pipe 

Advantages: Fast molding speed, high yield, and no damage to the coating. It can be made into a variety of cross section forms, to meet the needs of the usage conditions. Cold rolling can produce great plastic deformation of steel, thus raising the yield point of steel.

Disadvantages: Although there is no thermal plastic compression during the forming process, residual stress still exists in the section, which will inevitably affect the overall and local buckling characteristics of the steel. Cold rolled steel section is generally open section, so that the section of the free torsional stiffness is low. Torsion is easy to occur in bending, bending and torsional buckling is easy to occur in compression, and the torsional resistance is poor. The cold rolled section steel wall thickness is smaller, and there is no thickening at the corner of the plate connection, so the ability to bear local concentrated load is weak.

Other aspects

  1. Dimension accuracy: cold rolled steel pipe has high accuracy in dimension;
  2. Appearance: The surface of cold-rolled steel pipe is bright, while the surface of hot-rolled steel tube has obvious oxidation skin or red rust;
  3. Diameter: The diameter of cold-rolled steel pipe is smaller than that of hot-rolled steel pipe (Diameter of hot rolled steel pipe is larger than 32mm, and wall thickness is between 2.5-75mm; while diameter of cold rolled steel pipe can be 5mm, and wall thickness can be less than 0.25mm);
  4. Price: cold rolled steel tube is 1000-2000 more expensive than hot rolled steel pipe per ton;
  5. Use: Hot rolled steel pipe is used in the field in which dimension is not so precise, such as fluid transport and mechanical structure; while cold rolled steel pipe is used in precision instruments, such as hydraulic systems, pneumatic…

If you any needs or questions of hot rolled seamless steel pipe for various application, welcome to consult and contact us!

 

 

 

Introduction of 3PE anti-corrosive coating steel pipe

Introduction of 3PE anti-corrosive coating steel pipe

Brief introduction:

The base material of 3PE anti-corrosive coating steel pipe includes seamless steel pipe, spiral welded steel pipe and straight seam welded steel pipe. Three layer polyethylene (3PE) anti-corrosive coating has been widely used in the oil pipeline industry for its good corrosion resistance, water vapor permeability resistance and mechanical properties. 3PE anti-corrosion coating is very important for the service life of buried pipelines. Some pipelines of the same material are buried in the ground for decades without corrosion, and some are leaked in a few years. The reason is that they use different coatings.

Anti-corrosion structure:

3PE anti-corrosion coating is generally composed of three layers of structure: first layer is epoxy powder (FBE) > 100um,second layer adhesive (AD) 170 ~ 250um,the third layer is polyethylene (PE) 1.8-3.7mm.In the actual operation, the three materials are mixed and integrated, which are processed to be firmly combined with the steel pipe to form an excellent anti-corrosive coating. The processing method is generally divided into two types: winding type and circular mold covering type.

3PE anti-corrosive steel pipe coating (three-layer polyethylene anti-corrosive coating) is a new anti-corrosive steel pipe coating produced by ingenious combination of 2PE anti-corrosive coating in Europe and FBE coating widely used in North America. It has been recognized and used for more than ten years in the world.

The first layer of 3PE anti-corrosive steel pipe is epoxy powder anti-corrosive coating, and the middle layer is copolymerized adhesive with branch structure functional group. The surface layer is high-density polyethylene anti-corrosive coating.

3LPE anti-corrosive coating combines the high impermeability and mechanical properties of epoxy resin and polyethylene. Up to now, it is recognized as the best anti-corrosive coating with the best effect and performance in the world, which has been applied in many projects.

Advantages:

The common steel pipe will be severely corroded in the bad use environment, which will reduce the service life of the steel pipe. The service life of the anti-corrosion and heat preservation steel pipe is also relatively long. Generally, it can be used for about 30-50 years, and the correct installation and use can also reduce the maintenance cost of the pipe network. The anti-corrosion and heat preservation steel pipe can also be equipped with an alarm system, Automatic detection of pipe network leakage fault, accurate knowledge of fault location and also automatic alarm.

3PE anti-corrosion and heat preservation steel pipe has good heat preservation performance, and the heat loss is only 25% of that of traditional pipes. Long-term operation can save a lot of resources, significantly reduce energy costs, and still have strong water-proof and corrosion-resistant ability. Moreover, it can be directly buried in the underground or in the water without additional pipe trench, which is also simple, rapid and comprehensive in construction. The cost is also relatively low, and it has good corrosion resistance and impact resistance under low temperature conditions, and it can also be directly buried in frozen soil.

Application:

For the purpose of 3PE anti-corrosion steel pipe, many people only know one thing and don’t know the other. Its function is really wide coverage. It is suitable for underground water supply and drainage, underground shotcreting, positive and negative pressure ventilation, gas drainage, fire sprinkler and other pipe networks. Waste residue and return water transmission pipeline for process water of thermal power plant. It has excellent applicability for the water supply pipeline of anti spray and sprinkler system. Power, communication, highway and other cable protection sleeve. It is suitable for high-rise building water supply, heat supply network, water works, gas transmission, buried water transmission and other pipelines. Petroleum pipeline, chemical and pharmaceutical industry, printing and dyeing industry, etc. Sewage treatment discharge pipe, sewage pipe and biological pool anti-corrosion engineering. It can be said that 3PE anti-corrosion steel pipe is indispensable in the current construction of agricultural irrigation pipe, deep well pipe, drainage pipe and other network applications, and it is believed that through the extension of science and technology, it will still have more brilliant achievements in the future.

If you need any kind of anti-corrosion coating steel pipes such as 3PE coating steel pipes,FBE coating steel pipes and 3PP coating steel pipes,etc. Please contact us!