Cold Drawn Seamless Tube Production Process and Heat Treatment
E355 Cold Drawn Seamless Tube Production Process and Heat Treatment
1. Billet Preparation: Material Selection: High-quality carbon steel, alloy steel, or stainless steel billets are sourced. Cleaning: Billets are cleaned to remove surface oxides or contaminants.
2. Heating: Billets are heated in a furnace to 1100–1300°C (depending on material) for plasticity and machinability.
3. Piercing: A rotary piercer or cross-roll piercer is used to create a hollow tube blank (mandrel bar) at high temperatures. This step forms the initial tube shape.
4. Hot Rolling (Pilger Rolling) :The hollow tube is elongated and reduced in diameter via a pilger mill, improving dimensional accuracy and surface finish.
5. Cold Drawing
- Process: The tube is drawn through a die and mandrel at room temperature using a cold drawing machine. Multiple passes may be required to achieve final dimensions.
- Lubrication: Lubricants (e.g., soap or emulsion) reduce friction and prevent galling.
- Result: Enhanced mechanical properties, tighter tolerances, and smoother surface.
6. Heat Treatment
- Annealing:
- Purpose: Relieve residual stresses, soften the material, and improve machinability.
- Method: Tube is heated to 600–800°C, held, then slow-cooled in a furnace.
- Normalizing:
- Purpose: Refine grain structure and enhance strength.
- Method: Heated above AC3 temperature (~850–950°C), air-cooled.
- Quenching & Tempering (Quenched and Tempered):
- Purpose: Achieve high strength and toughness.
- Process: Tubes are quenched in oil/water (hardening) and tempered at 500–650°C.
7. Straightening : Tubes are passed through a mandrel straightener to correct any bending or warping.
8. Cutting: Finished tubes are cut to required lengths using saws or shears.
9. Inspection
- Dimensional Checks: Wall thickness, outer diameter, and roundness via calipers or laser micrometers.
- Surface Inspection: Visual or eddy current testing for defects.
- Mechanical Testing: Tensile, hardness, and impact tests.
- Non-Destructive Testing (NDT): Ultrasonic or radiographic testing for internal flaws.
Key Features of E355 Cold Drawn Seamless Tubes
- Superior dimensional accuracy and surface finish.
- High strength-to-weight ratio due to cold working.
- Customizable properties via tailored heat treatments.