How to make a choice from welded steel pipes in the current steel pipe market

In steel pipe industry, welded steel pipe is a very common type of steel materials today. It has been widely applied to various fields in daily life and some working operation. Furthermore, it brings more convenience to our living and production activities. In the current steel pipe market, there are two major categories of welded steel pipe as follows:

1) General welded pipe: general welding is used for conveying low pressure liquid. It is manufactured with Q195A, Q215A, Q235A steel materials in a mill. General welded steel pipe s have pressure, bending, flattening and other experiment, and the surface quality is a certain request, and usually the delivery length is 4-10m, often required sizing delivery of the goods. The specifications of the welded pipe uses nominal diameter (mm or inches), and the nominal diameter is different from the actual diameter. The welded pipe wall thickness following by the regulation includes ordinary steel pipe and thickening steel pipe, and steel pipe by the form of the pipe end includes the pipe with thread and pipe without thread.
2) Galvanized steel pipe: in order to improve the corrosion resistance of steel pipe, we can have galvanization to the common steel pipe commonly. Galvanized steel tube includes hot dip galvanized steel pipe and pre galvanized steel pipe in the current steel pipe market. And hot dip galvanized zinc coating is thick when compared with pre galvanized steel pipe in a mill.

In addition, China steel pipe manufacturers produce welded steel pipes by taking such flat substrates as steel plate or HR coil, and shaping and welding them. Classification of the pipes can be the result of different approaches. Professionals consider whether the steel pipe is straight seam or spiral welded. Others may divide the material into its purpose e.g. mining, oil drilling, agricultural, or manufacturing. One of the more common ways of classifying welded steel pipes is by looking at the process. In other words, classifying steel pipes according to production methods and/or sub-processes.
1)Electric-Resistance Welded (ERW): ERW is either high or low frequency. Restricted to a size of a maximum of approximately 24” in diameter, this type of welded steel pipe is the result of longitudinally welded HR coil, which has been widely used as steel conduits in wire systems today.
2.Longitudinal (LSAW or DSAW): The main substrate for this method is heavy steel plate. Producers use one of two methods, submerged arc welded (SAW) and the double submerged arc welded (DSAW). The resulting flat plate features a straight seam stretched the full length of the pipe. Standard sizes for this type of pipe range between 12m and 18m. By using this method, the weld quality is high with few defects.
3).Spiral welded or spiral welded longitudinal: spiral welded, like the name indicates, is the result of a circular motion. The manufacturer takes the plate, and winds and welds the substrate of an HR coil or steel plate in a spiral. This method is called helical submerged arc welded (HSAW). The resulting product is longer and thicker than other methods. Overall, this method is favored because it proves to be simple, efficient, cost-effective and fast.