Chemical Composition of Carbon Steel, Alloy Steel and Austenitic Stainless Steel Pipe Specified for High Temperature Service Per BS 3059/2-1990
High temperature service pipes are used in a wide range of applications, from conveying natural gas, oil, and other petroleum products, to transporting corrosive and reactive fluids. To ensure that these pipes are of superior quality and able to withstand high temperature and pressure operations, the British Standard BS 3059/2-1990 specifies the chemical composition for three different groups of steels: carbon steels, alloy steels and austenitic stainless steels. This paper will summarize these requirements in detail.
Carbon steel is an alloy of iron and carbon and can be subdivided into low and mild, medium and high carbon steels. Apart from carbon, other alloying elements such as manganese, silicon, and chromium can be included to improve the mechanical and physical properties of the steel. According to BS 3059/2-1990 the chemical composition of carbon steels must not exceed the following limits:
Carbon: 0.17-0.25%
Manganese: 0.25-1.20%
Silicon: 0.15-0.4%
Phosphorus: 0.20/0.030 max
Sulfur: 0.040 max
Alloy steels are made from combining elements of steel with other materials, such as nickel, molybdenum, vanadium, or chromium, to improve wear-resistance, formability, and other mechanical properties. BS 3059/2-1990 requires the following maximum alloy content for alloy steels used in high temperature service pipe applications:
Carbon: 0.08-0.15%
Manganese: 0.50-2.00%
Silicon: 0.20-0.60%
Phosphorus: 0.030 max
Sulfur: 0.040 max
Chromium: 0.50-3.00%
Molybdenum: 0.25-2.00%
Vanadium: 0.13-1.00%
Austenitic stainless steel is made from chromium-nickel steel and is designed to provide superior corrosion and oxidation resistance. According to the requirements laid forth in BS 3059/2-1990, the maximum chemical compositions for austenitic stainless steel high temperature service pipe applications are as follows:
Carbon: 0.045 max
Manganese: 0.50 max
Silicon: 0.60 max
Phosphorus: 0.040 max
Sulfur: 0.030 max
Chromium: 18.0-22.0%
Nickel: 8.0-10.5%
Molybdenum: 0.70-1.50%
Nitrogen: 0.15-0.25%
In conclusion, BS 3059/2-1990 is a standard that sets the chemical composition requirements for carbon steel, alloy steel and austenitic stainless steel pipe specified for high temperature service to ensure that they are of superior quality and able to withstand high temperature and pressure operations. It sets the maximum limits for carbon, manganese, silicon, phosphorus, sulfur, chromium, molybdenum, vanadium and nitrogen in these three classes of materials.
