In order to transport liquid or gas, a variety of pipes are crucial in the delivery. Except for steel pipes which are common (not surprisingly), there are different kinds of pipe fittings either: elbow bend, tees, flanges, valves, expansion joints to reduce the impact of thermal expansion or frequent vibration of the piping system. In addition, where the pipeline supply something, a variety of instruments is connected to various joints, plug and so on. We know as pipe fittings.

Metal is the most widely used industrial materials in our everyday lives. It is mainly divided into steel, iron, non-ferrous metals and other categories, and steel is one of the most commonly used material. The main ingredient in steel is iron, and the rest is various alloys and impurities human artificially added. Because of these varieties of different alloy added, a variety of steel is developed, such as ordinary carbon steel, stainless steel, alloy steel and so on. In these added parts of chemistry, the carbon plays a very important role.

Carbon steel: alloy includes only ‘C’, ‘Si’, ‘Mn’, ‘P’, ‘S’ five kinds according to its P, S impurity content level, is divided into carbon steel (P, S general <=0.040%) and quality carbon steel (P, S general <=0.03%)

Alloy steel: Except for C, Si, Mn, P, S contained, there are 10% of Cr Mo V such as common steel: 15CrMo, 12Cr1MoV, 1Cr5Mo, etc. Compared with carbon steel, alloy steel strength is high. It also improves heat resistance, but corrosion resistance is poor. Therefore, steel corrosion is not used for high temperature and pressure applications usually, such as boiler steel, thermal power plant steam delivery.

Stainless Steel: Compared with carbon steel, it increases a high proportion of Cr, Ni alloy. The content ratio is up to 20%. For instance, 304 is basic steel types containing only (C <0.08%), Cr (18%), Ni (9%). 304 (C <0.05%). 304L: ultra-low carbon 304L. 321, 316, 316L ----- ultra-low carbon C.

According to diverse alloy varieties added in the steel, steel will simply be divided into three categories: carbon steel, stainless steel, and alloy.

Pipe can be parted into pipe (Longitudinal spiral welded pipe) and seamless pipe. Pipe (also called pipe joints) is generally used for low pressure (20KG/CM2) pipeline. And the spiral welded pipe is primarily used for large diameter (DN400 above) system. Thus, the thickness is generally thin. Pressure is generally higher for seamless pipe. Due to limited seamless production process, industrial seamless pipe manufactured usually made of hot-rolled steel. Therefore, the wall thickness of hot-rolled seamless pipe available on the market has a definite limit.

There is considerable room for expansion in the pipe industry for the present. The main factors of the expansion include the growing energy demand, sustained increase in global population and urbanization in developing countries, the process of industrialization after the financial crisis. This trend has been growing steadily for years. Currently, the world's major economies have already entered the economic recovery cycle. The pipe industry was showing a steady upward growth therewith.