Performance advantages of spiral submerged arc welded steel pipe are following below: [1] The heat insulation performance is good, the heat loss is only 25% of the traditional double-sided submerged arc welded pipe, long-term operation can save a lot of energy, and significantly reduce energy costs. [2] With a strong waterproof and corrosion resistance, no need to attach a trench, can be buried directly in the ground or water, the construction is simple and rapid, low overall cost. [3] The double-sided submerged arc welded pipe also has good corrosion resistance and impact resistance under low temperature conditions and can be directly buried in the underground frozen soil. [4] The service life can reach 30-50 years. The correct installation and use can make the maintenance cost of the double-sided SAW pipe extremely low. [5] The alarm system can be set to automatically detect the leakage failure of the double-sided submerged arc welded pipe, accurately indicating the fault location and automatically alarming.

It is roughly divided into the oblique rolling method (mengnessmann method) and the kneading method. The oblique rolling method (Mengnessmann method) is to first use a diagonal roll to perforate seamless steel tubes and then use a rolling mill to extend them. This method has a high production speed, but it has a higher requirement on the processability of seamless steel tubes. It is primarily suitable for the production of carbon steel and low-alloy steel tubes. The kneading rule is to use a piercing machine to perforate seamless tube blanks or steel ingots and knead them into a seamless steel tube using a kneading machine. This method has lower power than the oblique rolling method and is suitable for producing high-strength alloy seamless steel tubes. The oblique rolling method and the kneading method must first heat the tube blank or the steel ingot, and the produced steel tube is called a hot-rolled seamless steel tube. Seamless pipes produced by hot working can sometimes be cold-worked as needed. There are two kinds of cold processing methods: one is the cold drawing method, that is, drawing a seamless steel pipe through a pipe drawing die, so that the steel pipe gradually becomes thin and elongated; the other method is a cold rolling method, which is to Meng Neisiman. The siblings invented hot rolling mills used in cold working methods. Cold-working of seamless steel tubes can advance the standard accuracy and processing finish of steel tubes and improve the mechanical properties of materials.

Thermal expansion process characteristics of seamless steel pipe is following: The first process is heating: one is heating below the critical point Ac1 or Ac3; the other is heating above the critical point Ac1 or Ac3. The first is mainly to stabilize the structure of seamless steel tubes and eliminate the residual stress of seamless steel tubes. The second is mainly to austenitize the steel. The second procedure is thermal insulation: the purpose is to heat the uniform seamless steel tube to obtain a reasonable heating of the tissue. The third process is cooling: the cooling process is the key process for the heat treatment of the seamless steel tube and decided the microstructure and mechanical properties of the seamless steel tube after cooling. The seamless steel tube cooling method used in the actual production process is various. The commonly used cooling methods are furnace cooling, air cooling, oil cooling, polymer cooling, and water cooling.

The defects on the outer surface of a seamless steel pipe are mainly the following: 1. Fold outside. The reasons for the formation are: poor quality of raw materials, mechanical scratches, and cracks in the metal surface during the deformation process. 2. Surface indentation (pits, scars). The reasons are: the surface of the tool is sticky metal, the surface of the seamless steel pipe is sticky to foreign matter, and metal blocks or other foreign materials are left in the hole type. 3. Ears, tweezers and green lines. The reasons for the formation are: the tools used are unreasonable, improper adjustments, hole-type asymmetry, or improper size of incoming materials. 4. External abrasions. The cause of the formation is that foreign objects scratch the surface of the seamless steel pipe. 5. Point (face). Mainly due to tool wear and oxide scales.

Cold-drawn pipe inner surface defects High-precision cold-drawn pipe inner surface roughness Ra ≤ 0.8μm, inner diameter size accuracy can reach H9 ~ H10, only in this way to ensure that after honing to H7 ~ H8 inner hole size and Ra ≤ 0.2μm inner surface roughness requirements. The main factors that affect the surface roughness of the honing tube In addition to the precision of the honing machine, the quality of the inner surface of the cold drawn tube is another key point. The internal surface defects of the cold drawn tube are classified by the measured data of the domestic A factory, there are mainly three kinds. 1. Point After the cold-drawn tube is roughed, it can be found that its surface is composed of many pit-shaped defects. If such defects are not worn out, it will seriously affect the finish of the inner bore of the cylinder barrel, which is a waste product for the cylinder barrel. 2. Scratch Scratch defects are generated during cold drawing. Generally, a scratch along the axial direction of the steel pipe must have a honing allowance exceeding the depth of the scratch, so that it is possible to wear off such defects and process a qualified cylinder. 3. Not round When the cold drawn tube is in production, the inner mold fixed on the core rod can float up and down. Therefore, the inner diameter of the cold drawn tube is not as straight as the machine tube. In addition, some hot-rolled pipes and the wall thickness of the same pipe are relatively large, and there is a non-uniform deformation of the pipe during cold-drawing deformation, and the out-of-round spots of the cold-drawn pipe are easily generated. After the tube is polished, it will be found that the inner hole has a sheet surface with different reflectance in other places. If the grinding amount is small, the phosphate layer in the cold drawing is not worn out. Seriously affect the cylinder surface quality.