Grade 2 Titanium Tube Bending

 

Grade 2 titanium tube bending is a high-precision plastic forming process that requires careful control of springback, cross-sectional deformation, and the risk of cracking; it is commonly used in high-end manufacturing sectors such as aerospace and deep-sea equipment.

When bending titanium tubes, the minimum bend radius must be observed; otherwise, the outer wall may crack or the inner wall may wrinkle. Depending on the tube specifications, the minimum bend radius is typically 1.2 to 3.2 times the outer diameter of the tube.

Titanium alloys exhibit significantly higher springback than stainless steel, typically ranging from 5° to 15°, or even higher. To compensate for springback, an angular allowance must be incorporated into the process design; CNC bending machines usually perform springback compensation calculations automatically. Heating to temperatures above 300°C can effectively reduce springback in pure titanium, while temperatures above 500°C can virtually eliminate springback in titanium alloy sheets.

 

 

Titanium (GR1/GR2 pure titanium, GR5, and other α+β alloys) has a modulus of elasticity that is only half that of steel, with a springback rate of 10%–15% (significantly higher than steel); it exhibits low plasticity at room temperature, rapid work hardening, and a tendency toward brittle fracture; above 400°C, it readily absorbs hydrogen, oxygen, and nitrogen, leading to surface oxidation and embrittlement, as well as a decline in mechanical properties.

Key deformation risks: Tensile stress on the outer side → thinning / cracking; compressive stress on the inner side → thickening / wrinkling; loss of circular cross-section → ovalization / flattening

Minimum bending radius (R): Cold bending of pure titanium: R ≥ 3d (d = outer diameter); Gr5: R ≥ 3.5d; hot bending can be reduced to R ≥ 1.5–2d; thin-walled sections (t/d < 0.08) must be filled or internally braced, otherwise wrinkling is inevitable

Springback compensation: Cold bending requires a pre-set springback angle of **3°–8°**; hot bending springback ≤ 1°, requiring minimal compensation.

 

 

1. Cold Bending Process (Room Temperature to 150°C)

Applicable Conditions: Thin-walled tubes (δ/D < 3%), small bending radii (R/D ≥ 2), pure titanium or low-alloy titanium tubes

Key Technical Points:

Mandrel Selection: Use multi-ball-joint mandrels or chain-type mandrels to support the inner side and prevent oval deformation

Die Design: Bending die groove radius = Target radius – Springback allowance (typically 5–15%)

Lubrication: Molybdenum disulfide-based lubricant or Teflon coating to reduce the coefficient of friction to 0.05–0.1

Speed Control: Feed rate ≤ 5 mm/s to prevent dynamic strain aging

2. Hot-bending Process (Medium-Temperature Forming)

Temperature Range: 200–400°C (below the recrystallization temperature of titanium)

Advantages:

Reduces yield strength by 30–40%

Significantly reduces springback (can be controlled to within 2°)

Improves wall thickness uniformity

3. Hot Bending Process (High-Temperature Forming)

Temperature Range: 600–800°C (above the recrystallization temperature)

Applications: Thick-walled tubes, small-radius bends (R/D < 2), complex spatial bends

Key Controls:

Atmosphere Protection: Argon or helium protection throughout the process, dew point < -40°C

Temperature Uniformity: Within ±15°C to prevent localized overheating

Deformation Rate: 0.01–0.1 m/s to avoid grain coarsening in the superplasticity region

4. Special Forming Processes

CNC Tube Bending

Combined push-pull bending: A press die provides additional force to counteract material flow resistance

Real-time compensation: Laser measurement of springback is used to iteratively adjust the bending angle

Multi-axis coordination: Enables continuous spatial bending with variable curvature

 

 

1. Dimensions: Bending radius R ±5%, angle ±1°, ovality ≤5% of outer diameter, wall thickness reduction ≤12% (Outer side)
2. Surface: Free of cracks, wrinkles, scratches, and scale; bright after acid pickling
3. Properties: Mechanical properties at the bend ≥ 90% of the base material; no internal defects as determined by non-destructive testing (PT/UT)
4. Standards: ASTM B338, AMS 4942

 

 

1. Aerospace

Engine piping: Gr5 titanium tubing, φ6–25 mm, R/D = 2–3, must comply with AMS 4928 standard

Hydraulic systems: Cold-bent, requiring an inner wall roughness of Ra ≤ 0.8 μm

2. Chemical processing equipment

Heat Exchanger Coils: Gr2 titanium tubing, continuous spiral bending, must undergo stress corrosion testing

Reactor Internal Coils: Hot bending + solution annealing, to eliminate residual stress

3. Medical Devices

Orthopedic Implants: Ti-6Al-4V ELI, bent in a ultra-clean environment, surface free of contamination

Surgical Instrument Handles: Precision small-radius bending, requires biocompatibility verification

 

 

 

E-mail: garychen3215@hotmail.com

Address: No.35, Baoti Rd, Baoji city, Shaanxi Province, China

Contact: Mr. Gary Chen

Phone: +86-917-8883215

Mobile/WhatsApp: +86 13092900605

 

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