What are the raw materials for manufacturing liquefied natural gas cylinders?
Qineng Welding System introduces to you what are the raw materials for manufacturing liquefied natural gas cylinders?
Steel
Carbon steel: Carbon steel is one of the commonly used materials for manufacturing LNG cylinders. It has high strength and toughness, and can withstand the pressure generated by LNG during storage and transportation. For example, some medium and low pressure LNG cylinders are made of high-quality carbon steel. It has a moderate carbon content, and while ensuring strength, it also has good machinability, making it easy to make the shape of the cylinder through stamping, welding and other processes. In addition, the price of carbon steel is relatively reasonable, which has certain advantages in cost control.
Alloy steel: For LNG cylinders that need to withstand higher pressure or are used in special environments, alloy steel is used. Alloy steel is based on carbon steel with the addition of alloying elements such as chromium, molybdenum, and nickel. The addition of these elements can significantly improve the strength, toughness, corrosion resistance and low temperature resistance of steel. For example, nickel can improve the low-temperature toughness of steel so that cylinders will not be brittle in low-temperature environments (the storage temperature of liquefied natural gas is very low). Chromium and molybdenum elements help enhance the corrosion resistance of steel and prevent the cylinder from being corroded by the external environment and internal media.
Aluminum alloy
Aluminum alloy materials are also used in the manufacture of liquefied natural gas cylinders. It has the characteristics of light weight and strong corrosion resistance. Compared with steel, aluminum alloy cylinders can greatly reduce the overall weight, which is very beneficial for the load distribution and energy consumption reduction of transport vehicles. At the same time, aluminum alloy can naturally form a dense oxide film in the air, which can effectively prevent further corrosion of aluminum alloy, thereby extending the service life of the cylinder. However, the strength of aluminum alloy is relatively lower than that of steel, so in the manufacturing process, special structural design or processing technology (such as using high-strength aluminum alloy, heat treatment, etc.) is required to meet the strength requirements of the cylinder.
Liner material (for double-layer bottle structure)
Stainless steel: In a double-layer LNG cylinder, the inner liner is the part that directly contacts the LNG, and the corrosion resistance of the material is extremely high. Stainless steel is an ideal material for the inner liner, such as 304 stainless steel and 316 stainless steel. 304 stainless steel has good corrosion resistance and processing properties, and can resist corrosion from moisture and impurities in LNG. 316 stainless steel performs better in environments with strong corrosiveness such as chloride ions, and is suitable for some situations where it may be exposed to more complex composition media.
Composite materials (such as fiber-reinforced resin): In addition to stainless steel, some new liner materials are also gradually being used. For example, fiber-reinforced resin composite materials, which combine high-strength fibers (such as carbon fiber and glass fiber) with a resin matrix. It has excellent corrosion resistance, good strength-to-weight ratio, and can be flexibly molded according to the shape of the liner, which can effectively reduce the thermal conductivity of the liner and improve the storage efficiency of liquefied natural gas.
Other supporting materials
Welding materials: Welding is a key process in the manufacturing process of gas cylinders, so welding materials are essential. For example, for steel gas cylinders, welding rods or welding wires that match the parent material will be used. These welding materials must ensure that the strength and toughness of the weld are equivalent to those of the parent material, and have good crack resistance and corrosion resistance.
Sealing materials: The valves and interfaces of gas cylinders require good sealing materials to prevent liquefied natural gas leakage. Commonly used sealing materials include rubber seals, such as nitrile rubber and fluororubber. Nitrile rubber has good oil resistance and sealing properties, and is suitable for general liquefied natural gas cylinder sealing; fluororubber has better resistance to low temperature, chemical corrosion and high temperature, and is used in occasions with extremely high sealing requirements.
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