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Seamless Steel Tubes for Structural and Mechanical Purposes - China Suppliers and Factory | GB/T 8162-2018
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 — Full Reference
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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Frequently Asked Questions
What is GB/T 8162-2018 and what does it cover?
GB/T 8162-2018 is a Chinese national standard that specifies the requirements for seamless steel tubes used for general structural and mechanical purposes. It covers dimensions, tolerances, chemical composition, mechanical properties, surface quality, inspection, and marking of seamless steel tubes.
What are the most commonly used steel grades under GB/T 8162-2018?
The most widely used grades are 20# (carbon steel) for general structural applications and Q345 (equivalent to 16Mn) for low-alloy high-strength applications. For high-strength mechanical components, grades such as 45#, 40Cr, and 42CrMo are commonly selected.
What is the difference between GB/T 8162-2018 and the previous 2008 edition?
GB/T 8162-2018 introduced updates to the available steel grades and tightened dimensional tolerances compared to the 2008 edition, ensuring higher quality and more precise specifications for modern engineering applications.
Is non-destructive testing (NDT) mandatory for GB/T 8162-2018 tubes?
No, non-destructive testing such as ultrasonic or eddy current testing is optional under GB/T 8162-2018 unless specifically required and agreed upon between the buyer and the manufacturer in the purchase contract.
What manufacturing processes are used to produce GB/T 8162-2018 seamless steel tubes?
GB/T 8162-2018 seamless steel tubes are produced by hot-rolling or cold-drawing processes. Depending on the steel grade and application requirements, additional heat treatment such as annealing, normalizing, or tempering may be applied.
What information should buyers include when ordering GB/T 8162-2018 seamless steel tubes?
Buyers should clearly specify the standard number (GB/T 8162-2018), the required steel grade (e.g., 20#, 45#, Q345), the dimensions including outer diameter, wall thickness, and length, as well as any special requirements such as heat treatment conditions or specific testing methods.