论述
Carbon steel and carbon manganese steel seamless steel tubes for ships
Seamless steel tubes are essential components in various engineering and manufacturing applications. They are mainly used in combination with highpressure equipment to manufacture ships, boilers, and other large-scale applications. GB/T5312-1999 is the national standard of carbon steel and carbon manganese steel seamless steel tubes for ships. This standard specifies the material requirements, technical performance, dimensional tolerances, test methods and inspection rules for these tubes.
GB/T5312-1999 is applicable to seamless steel tubes manufactured by hot forming. Only tubes of carbon steel and carbon-manganese steel are included in the standard. These materials are suitable for general engineering purposes. The sizes range from outside diameter 10mm to 273mm and wall thickness from 0.5mm to 30mm.
In terms of materials, the standard provides detailed requirements for chemical components and mechanical properties. For example, the maximum chemical components shall meet the values given in Table 1, which shows the maximum allowable percentages of various elements in the steel. For mechanical properties, the minimum yield strength and tensile strength limits are also specified in Table 1.
Table 1: Chemical Composition and Mechanical Properties Requirements for Carbon Steel and Carbon Manganese Steel Seamless Steel Tubes According to GB/T5312-1999.
In terms of dimensional tolerances, the standard has clear regulations for the allowable variation in diameter, wall thickness and length. The diameter shall not vary more than plus or minus 6.3% of the nominal diameter. The wall thickness shall not vary more than about 0.4 mm when the nominal thickness is over 10mm, but the deviation shall not exceed 0.5mm when the nominal wall thickness is less than 10mm. The length shall not be less than the nominal length. The standard also prescribes permissible levels of ovality, straightness and surface roughness.
The standard also states the technical performance requirements; tubes must conform to the chemical and mechanical properties requirements specified in the standard. Additionally, tubes must meet hydrostatic test, eddy current test and nondestructive testing requirements.
In terms of testing and inspection, the standard states that each tube shall be subjected to a hydrostatic test, with a nominal pressure equal to or greater than the minimum yield strength, which is determined according to the rules of Table 1. The test pressure shall not exceed the maximum pressure stated in Table 1 either. In addition to the hydrostatic test, certain eddy current tests must also be performed in the factory. A final inspection for surface quality, dimensional tolerances and finishes must also be conducted.
In conclusion, carbon steel and carbon manganese steel seamless steel tubes for ships must comply with GB/T5312-1999. This standard covers materials requirements, technical performance, dimensional tolerances, and test methods and inspection rules. It is important for manufacturers, suppliers and purchasers to understand and adhere to the specified requirements, in order to ensure the safe operation and reliable performance of the tubes.
