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GB/T 8162-2018 General Seamless Steel Tubes for Structural and Mechanical Purposes
Ordering Information
Buyers should specify in contracts:
- Standard number (GB/T 8162-2018)
- Steel grade (e.g., 20#, 45#, Q345, etc.)
- Dimensions (outer diameter, wall thickness, length)
- Special requirements (e.g., heat treatment, testing)
Main Steel Grades
Common grades include:
- Carbon steels: 10#, 20#, 35#, 45#
- Alloy steels: 16Mn (Q345), 27SiMn, 40Cr, etc.
Manufacturing Process
- Hot-rolled or cold-drawn seamless tubes.
- Heat treatment (annealing, normalizing, or tempering) may be required based on grade.
Technical Requirements
- Chemical composition: Must comply with GB/T 699 (carbon steels) or GB/T 3077 (alloy steels).
- Mechanical properties: Tensile strength, yield strength, elongation per steel grade.
- Surface quality: Free from cracks, folds, and severe imperfections.
- Dimensional tolerances: Specified for outer diameter, wall thickness, and length.
Inspection & Testing
- Non-destructive testing: Optional unless specified (e.g., ultrasonic or eddy current testing).
- Mechanical tests: Tensile, hardness, or impact tests as required.
- Hydrostatic test: Not mandatory unless agreed upon.
Marking & Packaging
- Tubes are marked with manufacturer’s name, grade, size, and standard number.
- Packaging methods (bundling, protection against corrosion) per agreement.
Key Differences from Previous Versions
- GB/T 8162-2018 updated steel grades and tightened tolerances compared to the 2008 edition.
Main Steel Grades
1. Carbon Structural Steels (Based on GB/T 699-2015)
- 10#
- 20# (Most commonly used)
- 35#
- 45# (High-strength applications)
2. Alloy Structural Steels (Based on GB/T 3077-2015)
- Q345 (Equivalent to 16Mn, a low-alloy high-strength steel)
- 27SiMn (High strength, used in hydraulic supports)
- 40Cr (Chromium alloy, good hardness and wear resistance)
- 20Cr
- 35CrMo (Molybdenum alloy, high-temperature strength)
- 42CrMo (Higher strength than 35CrMo)
3. Other Grades (Less common but included in some applications)
- 15CrMo (Chromium-molybdenum alloy, heat-resistant)
- 12CrMoV (For high-temperature service)
Key Notes:
- 20# and Q345 are the most widely used grades for general structural purposes.
- Higher carbon grades (45#, 40Cr, 42CrMo) are used for high-strength mechanical components.
- Alloy steels (27SiMn, 35CrMo) are selected for specialized applications requiring toughness or heat resistance.
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