1. Welded square pipe for low-pressure fluid transportation (GB/T3092-1993) is also called general welded pipe, commonly known as black square pipe. It is a welded steel pipe used to transport water, gas, air, oil, heating steam and other general lower pressure fluids and other purposes. The wall thickness of steel pipe connections is divided into ordinary steel pipes and thickened steel pipes; the connection end forms are divided into unthreaded steel pipes (plain pipes) and threaded steel pipes. The specifications of steel pipes are expressed in nominal diameter (mm), which is an approximate value of the inner diameter. It is customary to express it in inches, such as 11/2, etc. In addition to being directly used to transport fluids, welded steel pipes for low-pressure fluid transportation are also widely used as the original pipes for galvanized welded steel pipes for low-pressure fluid transportation.
2. Galvanized welded steel pipe for low-pressure fluid transportation (GB/T3091-1993) is also called galvanized electric welded steel pipe, commonly known as white pipe. It is a hot-dip galvanized welded (furnace welded or electric welded) steel pipe used to transport water, gas, air, oil, heating steam, warm water and other general lower pressure fluids or other purposes. The wall thickness of the steel pipe connection is divided into ordinary galvanized steel pipe and thickened galvanized steel pipe; the connection end form is divided into non-threaded galvanized steel pipe and threaded galvanized steel pipe. The specifications of steel pipes are expressed in nominal diameter (mm), which is an approximate value of the inner diameter.
3. Welded steel pipes are divided into straight seam welded pipes and spiral welded pipes according to the form of the weld. The production process of straight seam welded pipe is simple, the production efficiency is high, the cost is low, and the development is rapid. The strength of spiral welded pipes is generally higher than that of straight seam welded pipes. Welded pipes with larger diameters can be produced from narrower billets, and welded pipes with different diameters can also be produced from billets of the same width. However, compared with straight seam pipes of the same length, the weld length is increased by 30~100%, and the production speed is lower. Therefore, smaller diameter welded pipes mostly use straight seam welding, while large diameter welded pipes mostly use spiral welding.
