Introduction
This Standard specifies the technical requirements of carbon steel, low alloy steel and alloy steel plates for boilers and pressure vessels. The chemical composition limits of these steels are used to determine their strength, toughness, weldability and other properties. The materials used in this standard are suitable for high temperature and high temperature operations and are commonly used in the manufacture of boilers and pressure vessels.
General
Carbon steel in accordance with this standard is divided into three grades：
1) Carbon Steel Plate Grade A (high strength, fine grain) and Grade B (low strength, fine grain).
2) Low Alloy Steel Plate Grade II and Grade III (low alloy, fine grain).
3) Alloy Steel Plate Grade IV, Grade V and Grade VI (alloy, fine grain).
Chemical Composition
The chemical composition of carbon steel and low alloy steel plates shall conform to the requirements in the table below：
Carbon steel：Carbon 0.17 to 0.29%, manganese 0.90 to 1.50%, phosphorus 0.035% or less, sulfur 0.035% or less.
Low alloy steel：Carbon 0.20 to 0.35%, manganese 0.80 to 2.00%, phosphorus 0.035% or less, sulfur 0.035% or less, chromium 0.60 to 1.50%, molybdenum 0.20 to 0.75%.
Alloy steel：Carbon 0.30 to 0.45%, manganese 0.80 to 2.00%, phosphorus 0.035% or less, sulfur 0.035% or less, chromium 0.45 to 1.00%, molybdenum 0.15 to 1.00%.
Mechanical Properties
The mechanical properties of carbon steel, low alloy steel and alloy steel plates shall meet the requirements in the table below：
Carbon steel：YS Tensile Strength ≥ 292 MPa, YS Yield Strength ≥ 270 MPa, elongation ≥ 25%, reduction in area ≥ 35%.
Low alloy steel：YS Tensile Strength ≥ 383 MPa, YS Yield Strength ≥ 345 MPa, elongation ≥ 20%, reduction in area ≥ 35%.
Alloy steel：YS Tensile Strength ≥ 440 MPa, YS Yield Strength ≥ 400 MPa, elongation ≥ 15%, reduction in area ≥ 25%.
Heat Treatment
Carbon steel and low alloy steel plates shall be annealed to obtain fine grain properties. Alloy steel plates should undergo heat treatment as required by the order.
Inspection
For the inspection of chemical composition and mechanical properties of carbon steel, low alloy steel and alloy steel plates, the recommended inspection methods are as follows：
Chemical composition：Using spark spectrometry to measure the content of carbon, manganese, phosphorus, sulfur and other elements.
Mechanical properties：Using tensile testing machine to measure the tensile strength, elongation and other parameters.
Conclusion
This Standard specifies the technical requirements of carbon steel, low alloy steel and alloy steel plates for boilers and pressure vessels, including chemical composition and mechanical properties. This Standard also provides methods for testing the quality of carbon steel, low alloy steel and alloy steel plates. This standard is suitable for use in high temperature and high temperature operations and is widely used in the manufacture of boilers and pressure vessels.
