Welded pipes are not seamless pipes. Many people understand and distinguish between seamless pipes and welded pipes. In fact, the distinction between the two is very easy. Below I teach you how to distinguish between the two. First of all, the seamless steel pipe and the welded pipe are mainly different in the molding process. Welded pipes are generally welded by bending the flat material. You can find a weld on the top; the coarser diameter is usually a spiral weld. The seamless steel pipe is generally formed by laminating molten steel in a molten state through a ring slit and then being subjected to a stretching process, so that there is no weld. This is the difference that is distinguished by the naked eye.
In terms of performance, especially the pressure-bearing capacity, the seamless pipe is greatly improved than the ordinary steel pipe, so it is often used for high-voltage equipment. The weld joint of ordinary steel pipe is its weak link, and the weld quality is also the main factor affecting its overall performance. The use of seamless tubes for high-pressure, high-strength, mechanical structural materials perfectly reflects its superiority. Mainly used in petroleum, aviation, smelting, food, water conservancy, electric power, chemical, chemical, chemical fiber, pharmaceutical machinery and other industries.
The variety of welded steel pipes is increasing, and seamless steel pipes have been replaced in more and more fields. Welded steel pipes are divided into straight welded pipes and spiral welded pipes in the form of welds. Classified according to production methods: process classification – arc welded pipe, erw steel pipe, (high frequency, low frequency) gas welded pipe, furnace welded pipe. Straight seam welded pipe has simple production process, high production efficiency, low cost and rapid development. The strength of the spiral welded pipe is generally higher than that of the straight welded pipe. It is possible to produce a welded pipe with a large diameter by using a narrow blank, and it is also possible to produce a welded pipe having a different pipe diameter by using a blank of the same width.
However, compared with the straight pipe of the same length, the weld length is increased by 30 to 100%, and the production speed is low. Small-diameter welded pipe adopts straight seam welding, and large-diameter welded pipe adopts spiral welding; according to the shape of the end of steel pipe, it is divided into round welded pipe and special-shaped (square, rectangular, etc.) welded pipe; it is divided into mining fluid according to material and use. Conveying welded steel pipes, galvanized welded steel pipes for low-pressure fluid transportation, and belt-welded steel pipes for belt conveyors. According to the specification table in the current national standard, the wall thickness of the outer diameter is sorted from small to large.
In order to ensure the welding quality, prevent the groove at both ends of the weld and reduce the influence of stress concentration on the dynamic load, after the weld is formed, the two ends can be left on the weldment unless it is used, otherwise it should be cut after the welding is completed. Fillet Weld: It is not necessary to finish the edge of the connecting plate, the plate has no gap, and the weld metal is directly filled in the right angle or oblique angle formed by the two weldments. The size of the right-angled edge in a right-angled weld is called the fillet size, and the size of the smaller side is indicated by hf.
In order to ensure the quality of the weld, it is advisable to choose the appropriate weld angle. If the size of the solder fillet is too small, the soldering is not strong, especially if the soldering piece is too thick, and cracks are easy to occur; if the soldering foot is too large, especially when the soldering piece is too thin, it is easy to burn and penetrate, and when the soldering is pasted, It is prone to undercut.’