Aluminum Stud — Material & Producing Key Points

(Aluminum threaded stud on cookware / welding stud, cookware‑relevant versions)

1. Common Material Grades & Application for the Aluminum studs

Cookware recommendation:

• Threaded stud (cold‑forged): 6061‑T6 (preferred)
• Weld stud for aluminum pot body: 5052‑H32；must match base metal alloy to avoid hot‑crack risk

Important note: 6‑series & 5‑series cannot be mixed randomly for stud‑welding.

2. Raw Material Key Points

1. Use qualified aluminum wire rod with stable chemical composition; strictly control Fe, Si impurity to avoid inter‑granular crack during cold forming.
2. Wire surface: no scratch, oxide scale, oil contamination. Oil will cause thread crack, black anodizing, weld porosity.
3. Temper condition: Raw material must be pre‑stabilized; eliminate residual stress to prevent stud bending after threading / anodizing.
4. Food‑contact cookware: Alloy shall comply with EU 10/2011, LFGB or GB4806.9‑2016. However, usually the Aluminum stud would not contact the food directly.

3. Manufacturing Process Key Points

3.1 Cold Forging (Cold Heading)

• Main forming process for mass‑production aluminum studs.
• Control forming speed & die clearance; aluminum is soft, easy to produce burr, fold crack at transition fillet.
• Fillet radius shall follow drawing; sharp corner will generate stress concentration, break under torque.

3.2 Thread Rolling

• Thread rolling (not cutting) preferred for better thread strength.
• Control rolling pressure: Over‑pressure causes thread crack; insufficient pressure leads to incomplete thread profile.
• Thread tolerance: 6H/6g for general cookware fasteners.

3.3 Heat Treatment (for heat‑treatable alloy )

• 6061 must achieve T6 temper after cold heading: tensile ≥260 MPa, yield ≥240 MPa.
• Non‑standard aging will cause low torque capacity, easy thread slipping during handle assembly.

3.4 Surface Treatment

1. Anodizing (most common):
   • Remove all oil before anodizing. Poor pre‑treatment results in color difference, local no‑film area.
   • Film thickness: 8‑12 μm for cookware studs.
2. No electro‑plating for aluminum stud in cookware (risk of peeling, food‑contact hazard).

3.5 If it is Aluminum Weld Stud (stud‑weld onto pot body)

1. Stud tip design: Special ignition tip for aluminum stud, ensures stable arc starting.
2. Surface cleaning: Remove Al₂O₃ oxide film, oil, dust before welding. Aluminum oxide will cause porosity, non‑fusion defect.
3. Shielding gas: High‑purity Argon ≥99.99% is mandatory for drawn‑arc stud welding.
4. Parameter window is narrow: Control current, weld time, lift height; avoid burn‑through for thin cookware sheet (0.8‑2.0 mm).
5. Weld quality check: Bend test 30°, no crack at weld joint; tensile test failure occurs on stud body rather than weld zone.

4. Critical Quality‑Control Items

1. Dimension: Thread major/minor diameter, stud length, perpendicularity tolerance.
2. Mechanical performance: Tensile strength, proof‑load, torque resistance; no thread slip when tightening.
3. Visual: No cold‑heading crack, thread burr, surface scratch.
4. Surface‑treatment: Anodizing film thickness, no color difference.
5. For weld‑stud: No porosity, no crack at weld interface; pull‑out test passed.
6. Food‑contact: Heavy‑metal leaching test for cookware application.

5. Typical Failure Modes in Cookware Production

1. Thread slipping → insufficient T6 aging; improper thread‑rolling pressure.
2. Stud bends after anodizing → residual stress from raw material / cold forging.
3. Weld‑stud falls off → oxide‑film not cleaned; bad shielding‑gas; mismatched alloy between stud and pot base.
4. Anodizing color difference → residual oil on raw‑material surface.

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