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what is seamless steel pipe

The seamless steel pipe is made of perforated whole round steel, and the steel pipe without weld seam on the surface is called seamless steel pipe. According to the production method, seamless steel pipes can be divided into hot-rolled seamless steel pipes, cold-rolled seamless steel pipes, cold-drawn seamless steel pipes, extruded seamless steel pipes, and pipe jacking. According to the cross-sectional shape, the seamless steel pipe is divided into two types: round and special-shaped. The maximum diameter is 900mm and the minimum diameter is 4mm. According to different uses, there are thick-walled seamless steel pipes and thin-walled seamless steel pipes. Seamless steel pipes are mainly used as petroleum geological drilling pipes, cracking pipes for petrochemical industries, boiler pipes, bearing pipes and high-precision structural steel pipes for automobiles, tractors and aviation.

seamless steel pipe
seamless steel pipe

What is Seamless Steel Pipe Used For?

Seamless steel pipes are widely used.

  1. General-purpose seamless steel pipes are rolled from ordinary carbon structural steel, low-alloy structural steel or alloy structural steel, with the largest output, and are mainly used as pipelines or structural parts for conveying fluids.
  2. According to different uses, there are three types of supply:
    a. Supply according to chemical composition and mechanical properties;
    b. Supply according to mechanical properties;
    c, according to the hydraulic test supply. Steel pipes supplied according to categories a and b, if they are used to withstand liquid pressure, shall also be subjected to a hydrostatic test.
  3. There are many kinds of seamless pipes for special purposes, such as seamless pipes for boilers, seamless pipes for chemical power, seamless pipes for geological use and seamless pipes for petroleum.
    Seamless steel pipes have hollow sections and are widely used as pipelines for transporting fluids, such as pipelines for transporting oil, natural gas, gas, water and certain solid materials. Compared with solid steel such as round steel, the steel pipe is lighter in weight when the bending and torsional strength is the same, and is an economical section steel.
    It is widely used in the manufacture of structural parts and mechanical parts, such as oil drill pipes, automobile transmission shafts, bicycle frames and steel scaffolding used in construction. The use of steel pipes to make ring parts can improve the utilization rate of materials, simplify the manufacturing process, and save materials and processing. Man-hours have been widely used to manufacture steel pipes.

What are the benefits of Seamless Steel Pipe?

Seamless pipes can be more expensive to produce and purchase, but it is more reliable and there are many benefits including

  1. They are very durable and withhold high levels of pressure, about 20% higher pressure than welded pipes. They are also very resistant to corrosion.
  2. Seamless pipes harden during the manufacturing process, so they generally don’t need heat treatment.
  3. A seamless pipe can be used in place of a welded pipe, but a welded pipe cannot be used in place of a seamless pipe.
  4. Seamless pipes have a more solid round cross section than welded pipes.
  5. It has great strength and can support large amounts of weight.

how seamless steel pipe is made

First, first, the worker confirms the length of the steel pipe with a tape measure, and then uses different types of micrometers to measure the outer diameter and wall thickness of the steel pipe. Then insert the steel pipe that meets the specifications into the rotating hammer breaker. The machine will grind the end of the steel pipe so that it can be inserted into the small diameter cavity, then apply lubricant to it, and insert the ground end into the pump. Line fill the mold, then grab the deep end with this large dolly and pull it out from the sight. This process is called cold drawing, which is to draw the steel pipe through a drawing die, so that the wall of the steel pipe becomes thinner, deeper, and gradually elongated. When the steel pipe passes through the two rollers of the machine in the next step, pressure will be exerted from the outside to expand the steel pipe slightly, so that a gap is formed between the pipe wall and the steel pipe inside, so that the machine can easily fish out the steel pipe.

Second, the worker sawed off the thinner end, then sent the steel pipe to the degreasing device, and cleaned the residual lubricant on the surface of the steel pipe with cleaning fluid. Then put the steel pipe into Feng Gancao, which can be placed at a slightly inclined angle. After waiting for the air inside to dry the steel pipe for half an hour, take out the steel pipe for further cleaning. The worker will stuff the felt pad into the steel pipe, then spray a small amount of cleaning liquid, and then inject compressed air into it with an air gun, so that the felt pad is sprayed out from the other end through the whole steel pipe, so that the inner wall of the whole steel pipe is wiped with the cleaning liquid again. Then workers tied the steel pipe to a conveyor belt and sent him to a 980-degree smelter for half an hour. The hot high temperature can soften just now, the purpose is to reduce hardness and improve machinability. This process is called annealing.

Third, the annealed steel pipe is then passed through the straightening machine, and the whole process is repeated continuously until the steel pipe reaches the length specified by the customer. The finished steel pipe can be up to 40 times longer than the original. In order to ensure the structural integrity of each steel pipe, the worker will apply current to its periphery. If the current is interrupted, it indicates a defect, then the part of the segment will be cut to the length specified by the customer, and the situation after cutting will be rough. fault, so put one end of the cut into the machine for grinding. After smoothing the edges, the steel pipes are soaked in an acid solution to remove iron filings or other impurities that were sticky during the production process. Finally, the samples are tested for product quality, and these seamless steel pipes can be packaged and sent to customers.

China’s current seamless steel pipe standard

  1. Current seamless steel pipe standards: a total of 47 items including: GB/T25 items HB3 items 19 items for special purposes; 2 basic items 45 items
  2. Commonly used standard:
    ① GB/T2102-2018 Acceptance, packaging, marking and quality certificate of steel pipes.
    ② GB/T17395-2008 Size, shape, weight and allowable deviation of seamless steel pipe.
    ③ GB/T5310-2018 Seamless steel tubes for high pressure boilers.
    ④ GB/T9948-2018 Seamless steel pipes for petroleum cracking.
    ⑤ GB/T6479-2018 Seamless steel pipes for high-pressure fertilizer equipment.
    ⑥GB/T18248-2018 Seamless steel pipes for gas cylinders.

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