Hot Products
- Carbon & Carbon Alloy Steel
- Stainless Steel
- Copper & Nickel Alloy
- Heat Efficiency Tubes
- Pipe Fittings
- Pipe Flanges
- Gasket, Stud Bolt &Nut
- Industrial Valves
0102030405
General Seamless Steel Tubes for Structural and Mechanical Purposes - China Suppliers and Factory
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.
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)
- 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.
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.
📩 Want to order the same? Contact us Now to send your request!
Frequently Asked Questions (FAQ)
What is GB/T 8162-2018 and what does it cover?
GB/T 8162-2018 is the Chinese national standard for seamless steel tubes used in structural and mechanical purposes. It specifies the technical requirements for dimensions, mechanical properties, chemical composition, surface quality, and inspection methods for seamless steel tubes manufactured from carbon and alloy steels.
What are the most commonly used steel grades under GB/T 8162-2018?
The most widely used grades are 20# (carbon steel) and Q345 (equivalent to 16Mn, a low-alloy high-strength steel). These two grades are preferred for general structural applications due to their balanced strength, weldability, and cost-effectiveness.
What is the difference between GB/T 8162-2018 and the 2008 edition?
GB/T 8162-2018 introduced updated steel grades and tightened dimensional tolerances compared to the 2008 edition. These revisions align the standard more closely with modern manufacturing precision requirements and expand the range of applicable alloy grades.
Is non-destructive testing mandatory for GB/T 8162-2018 seamless steel tubes?
No, non-destructive testing (such as ultrasonic or eddy current testing) is optional under GB/T 8162-2018 and is only required if specifically agreed upon between the buyer and manufacturer in the contract. Similarly, hydrostatic testing is not mandatory unless otherwise specified.
What manufacturing processes are used to produce GB/T 8162-2018 seamless tubes?
Seamless tubes conforming to GB/T 8162-2018 are produced via hot-rolling or cold-drawing processes. Depending on the steel grade and application requirements, heat treatment processes such as annealing, normalizing, or tempering may also be applied to achieve the desired mechanical properties.
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), exact dimensions including outer diameter, wall thickness, and length, as well as any special requirements such as specific heat treatment conditions or additional testing methods in the purchase contract.