The manufacturing of hot-rolled seamless steel pipes is a complex thermal processing procedure that transforms solid billets into hollow steel pipes. United Steel Industry Co., Ltd has meticulously summarized the key steps involved in this process:
1. Tube Billet Preparation
Selection of Tube Billets: Raw materials typically include round ingots, rolled billets, or continuous casting billets. The quality of these billets directly impacts the final product, requiring strict quality control.
Inspection and Cleaning: A visual inspection is performed to detect and remove surface defects such as cracks and inclusions.
Cutting: Billets are cut to the required length to facilitate subsequent heating and piercing.
2. Tube Heating
Heating Furnace: Cut billets are heated in specialized furnaces such as ring furnaces or stepping furnaces.
Temperature Control: Billets are heated to a rolling temperature between 1100-1300℃. Maintaining optimal temperature is crucial—excessive heat can cause overburning, while insufficient heat increases rolling difficulty.
Uniform Heating: Ensures consistent temperature distribution within the billet, allowing for smooth piercing and rolling.
3. Piercing
Punching Machine: The heated billet is fed into a punching machine to create a hollow center, forming a rough tube.
Punching Methods:
Oblique Rolling Punching: The most widely used method, where rollers rotate and apply axial movement to create a central hole.
Push Rolling Punching: Another method used based on specific requirements.
Punching Head: Supports the inner wall, controls the internal diameter, and prevents deformation.
Quality Requirements: The rough tube must have uniform wall thickness, smooth surfaces, and no cracks or folds.
4. Rolling
Tube Rolling Mill: The perforated rough tube undergoes rolling to reduce wall thickness and adjust the outer diameter.
Rolling Methods:
Automatic Tube Rolling Mill: Uses conical rollers that rotate and apply axial force to the tube blank.
Continuous Tube Rolling Mill: Comprises multiple rolling stands for seamless, continuous production.
Periodic Tube Rolling Mill: Used for specific rolling requirements.
Rolling Process: The tube continuously rotates and moves forward, undergoing plastic deformation under roller pressure to achieve the desired size and wall thickness.
5. Wall Thickness Control and Sizing
Scaling: A leveling machine is used to refine wall thickness accuracy.
Sizing: The steel pipe’s outer diameter is precisely adjusted using a sizing mill or stretch reducer to meet final specifications.
6. Cooling
Cooling Methods:
Air Cooling: Slower cooling process.
Water Cooling: Faster cooling rate, improving the pipe’s strength and hardness.
7. Straightening
Straightening Machine: The cooled steel pipe undergoes straightening to correct bending and ensure uniform alignment.
8. Cutting and End Trimming
Head and Tail Removal: Defective sections at both ends are cut off to eliminate irregularities from rolling and cooling.
Length Cutting: Pipes are cut to the required dimensions.
9. Quality Inspection
Non-Destructive Testing (NDT): Includes ultrasonic testing, eddy current testing, and hydrostatic pressure testing to detect internal and surface defects such as cracks or inclusions.
Additional Tests: May include chemical composition analysis and mechanical property testing based on requirements.
10. Marking and Storage
Marking: Stamping or labeling pipes with specifications, material grade, batch number, and other details.
Anti-Rust Coating: A protective oil layer is applied to prevent corrosion during storage and transportation.
Packaging: Pipes are bundled or packed as per customer requirements.
Warehousing: Finished pipes are stored in warehouses, ready for distribution.
Conclusion
The hot-rolled seamless steel pipe production process is a multi-step operation, where each stage plays a critical role in ensuring final product quality. By implementing stringent control measures at every stage, manufacturers can produce high-quality seamless steel pipes to meet diverse industrial applications.
United Steel Industry As the most important steel pipe manufacturer and exporter in China, in the past 20 years, we have completed more than 100 projects, with partners in more than 100 countries, and established relationships with oil and gas and EPC companies in many countries business relationship.
For more information about the product price, catalog and rolling mill inspection certificate,
please consult:Email:Sales@usisteels.com
