Welding technology is very important in the manufacture of steel pipes, one of which is called straight seam welded pipe. The production process of straight seam welded pipe is simple, with high production efficiency, low cost, and rapid development. The strength of spiral welded pipes is usually higher than that of straight seam welded pipes. Welded pipes with larger diameters can be produced from the narrower blanks of the solar panel greenhouse, and welded pipes with different diameters can also be produced from the blanks of the same width. However, compared with the straight seam pipe of the same length, the weld length is increased by 30~100%, and the production speed is lower.

　　 Generally speaking, the diameter of a pipe can be divided into outer diameter, inner diameter, and nominal diameter. The outer diameter of the spiral steel pipe of the spiral pipe factory is marked with the letter D. After this, the scale and wall thickness of the outer diameter are added. For example, a seamless steel pipe with an outer diameter of 108, with a wall thickness of 5MM, is marked with D1085. Plastic Pipes are also marked with outer diameters, such as De63. Others such as reinforced concrete pipes, cast iron pipes, galvanized pipes, etc. are marked with DN. In the planning drawings, the nominal diameter is usually used for marking. The nominal diameter is for the convenience of planning, production and repair. A kind of standard of rules, which is also a standard designation for pipes (or pipe fittings) compared to the nominal diameter.

      The nominal diameter of the pipe is not equal to its inner and outer diameters. For example, there are several types of spiral steel pipes with a nominal diameter of 100MM, such as 1025 and 1085. 108 is the outer diameter of the pipe, and 5 indicates the wall thickness of the pipe. Therefore, the steel pipe The inner diameter of (1085-5)=98MM, but it is not completely equal to the difference between the outer diameter of the steel pipe minus twice the wall thickness. It can also be said that the nominal diameter is close to the inner diameter, but it is not equal to the inner diameter of a pipe diameter standard Designation, the nominal diameter is used in the planning drawings. The intention is to determine the layout and connection dimensions of pipes, pipe fittings, valves, flanges, gaskets, etc. based on the nominal diameter. The nominal diameter is indicated by the symbol DN. If it is in the planning drawings The outer diameter is used to indicate, and a pipe standard comparison table is also made to indicate the nominal diameter and wall thickness of a certain pipe.

Many operators who process steel pipes report that there is trachoma at the butt welds of spiral steel pipes. Spiral steel pipe is formed by bending steel strip in the spiral direction through a coiling machine, and then through double-sided submerged arc welding of capacitors. In the production process of spiral steel pipe welding, there are many situations such as missing welding and wrong edge. However, the most difficult to grasp in these situations is the presence of trachoma at the butt weld of the spiral steel pipe. The so-called trachoma: during the welding process, on the outside of the weld or inside the weld, there are particles or bubbles that are not completely penetrated, and the pits in the shape of sand on the outside of the weld.

The reasons for the trachoma in the spiral steel pipe factory are as follows:

1. During the welding process, the current supplied to the welding gun is too small, and the capacitor time is too short. When the capacitor is not completely welded, it appears to be hardened outside the welding, so there are sand or bubbles that have not been welded through.

2. When the strip steel enters the scimitar-shaped adjustment arc, it is not properly butted, the strip steel is not tightly connected, and there is an excessively large open space between the butt steel strips.

3. When butt welding the strip steel, the rust or oxide scale on both sides of the strip steel was not cleaned up in time.

4. The production equipment was not repaired in time. The dust on the workbench may be dirty and fall into the welding gap of the butt strip by mistake.

5. The temperature in the operating workshop may be too low or too humid, which will affect the temperature and dryness of the solder joints.

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