Aluminum discs used in kitchenware are prone to problems such as “cracking” and “wrinkling” during operation. How to prevent them?

1. Introduction: Industry Pain Points and Impacts of Processing Defects in Aluminum Discs for Kitchenware

Aluminum discs for kitchenware (commonly used in pots, frying pans, tableware, etc.) are mainly made of 3003, 5052, and 1100 aluminum alloys. Their stamping and drawing processes require “thin-wall forming + dimensional accuracy + defect-free appearance”—however, “cracking” (local stress exceeding the material’s tensile strength) and “wrinkling” (local accumulation caused by uneven material flow) are two core defects, directly leading to:

1. Reduced pass rate (industry average defect rate: 8%-15%, reaching 20% for deep-drawn kitchenware);

2. Rising costs (raw material waste + mold maintenance costs increase by more than 30%);

3. Performance risks (cracking easily causes deformation during kitchenware use, while wrinkling affects uniform heat conduction).

To formulate practical prevention solutions, the root causes of defects must be accurately analyzed from three dimensions: material properties, process parameters, and mold design. Notably, Prevention of problems with aluminum discs used in kitchenware has become a key focus for manufacturers to improve production efficiency and product quality.

2. Core Cause Analysis of “Cracking” and “Wrinkling” Defects

(1) Cracking: Superimposed Effect of Stress Overload and Insufficient Material Ductility

1. Key Material-Related Triggers

• • Incorrect alloy selection: For example, using 5052 H18 temper (tensile strength: 260MPa, elongation: 10%) instead of 3003 O temper (tensile strength: 110MPa, elongation: 25%) for deep-drawn pots—insufficient ductility leads to cracking;

• • Internal material defects: Aluminum discs with rolling stripes (depth >0.02mm) or inclusions (Fe content >0.7% easily forms hard particles) become stress concentration points during drawing;

• • Improper heat treatment: Inadequate annealing (e.g., 3003 aluminum discs annealed at <340℃ for <1h) leaves internal stress uneliminated, causing a sudden increase in local stress during drawing.

2. Key Process and Mold-Related Triggers

• • Excessive drawing ratio: First drawing ratio (finished product diameter/blank diameter) >2.2 (limit for 3003 O temper) and subsequent drawing ratio >1.8, resulting in local thinning rate exceeding 35% (critical value for material fracture);

• • Too small mold fillet: Punch-die fillet radius R <5t (t = aluminum disc thickness; e.g., R <10mm when t=2mm), increasing the stress concentration factor from 1.2 to 2.5 and sharply raising cracking risk;

• • Lubrication failure: Lubricant carbonization (e.g., oil-based lubricant with flash point <180℃) during high-temperature drawing (mold temperature >60℃), increasing the friction coefficient from 0.05 to 0.15—local tension exceeds the material’s load-bearing limit.

(2) Wrinkling: Inevitable Result of Unbalanced Material Flow and Insufficient Constraints

1. Unbalanced Process Parameters

• • Insufficient blank holder force: Blank holder force F < K×t×D (K = coefficient, 1.2-1.5 for 3003 aluminum; t = thickness; D = blank diameter). For example, F <3600N when t=1.5mm and D=200mm—no effective constraint on the blank edge, causing excessive material flow into the cavity and wrinkling;

• • Abnormal drawing speed: Speed >2m/s (0.5-1.2m/s recommended for deep drawing) leaves no time for uniform material deformation, leading to local accumulation; speed <0.3m/s easily causes local material softening due to frictional heat accumulation, resulting in uneven flow.

2. Mold and Blank Design Defects

• • Unreasonable mold clearance: Single-sided punch-die clearance <1.05t (e.g., <2.1mm when t=2mm) increases material flow resistance; clearance >1.2t leaves insufficient material support, causing wrinkling;

• • Blank dimensional deviation: Aluminum disc roundness error >0.1mm (e.g., >0.2mm deviation for 200mm diameter) leads to uneven stress during drawing, with a >20% difference in edge material flow speed;

• • Poor exhaust: No vent holes (diameter <φ1mm) in the mold cavity or blocked vents form negative pressure (<-0.02MPa) inside the cavity during drawing, hindering material flow and causing local wrinkling.

3. Systematic Prevention Solutions: Collaborative Optimization of Material, Process, and Mold

(1) Material End: Precise Selection and Pretreatment Control (Core Prevention Foundation)

1. Alloy-Temper Matching (Classified by Cookware Type)

2. Key Material Pretreatment Processes

• • Annealing (eliminating internal stress): 3003 aluminum discs are insulated at 340-360℃ for 1.5-2h, then furnace-cooled to <100℃ before 出炉 (removal from furnace), ensuring hardness ≤HV30 (Vickers hardness); 5052 H14 temper needs to be first annealed to O temper (370-390℃ for 2h), then aged to H14 as needed;

• • Surface treatment: Control the thickness of the aluminum disc’s oxide film at 5-8μm (film >12μm easily causes cracking), oil contamination ≤5mg/m² (drying temperature: 60-80℃ after solvent cleaning), and surface roughness Ra ≤0.8μm (avoiding uneven friction resistance);

• • Blank inspection: Eddy current testing for internal inclusions (single inclusion area <0.5mm²), laser thickness gauge for thickness deviation ±5% (e.g., ±0.1mm when t=2mm), and roundness error ≤0.08mm.

(2) Process End: Quantitative Parameter Optimization and Dynamic Regulation

1. Quantitative Standards for Core Process Parameters (Taking 3003 O Temper, t=2mm Aluminum Discs as an Example)

2. Dynamic Regulation Strategies

• • Real-time monitoring: Use force sensors (accuracy ±1%) to monitor stamping force; when instantaneous force exceeds 1.2 times the material’s tensile strength, automatically reduce drawing speed by 20%-30%;

• • Lubricant replenishment: Reapply lubricant every 500-800 pieces; use “spray + wiping” for deep drawing to ensure a 5-10μm coating thickness (excessive thickness easily causes wrinkling);

• • Process intervals: Stop operation for 10 minutes every 2 hours during continuous processing to cool the mold to the set temperature range (avoiding material softening due to overheating).

(3) Mold End: Structural Optimization and Precision Control

1. Key Structural Design Parameters

• • Punch-die fillet: Design per “R=5t-8t” (R=10-16mm when t=2mm); use upper limit (R=14-16mm) for deep drawing and lower limit (R=10-12mm) for shallow drawing; ensure fillet surface roughness Ra ≤0.4μm (reducing stress concentration);

• • Clearance control: Single-sided clearance =1.05t-1.15t (2.1-2.3mm when t=2mm); use upper limit (2.2-2.3mm) for deep drawing and lower limit (2.1-2.2mm) for shallow drawing;

• • Exhaust system: Drill 2-4 φ1.2-1.5mm vent holes at the maximum projection of the mold cavity, with a hole depth of 5-8mm—ensure cavity pressure ≤-0.005MPa during drawing (avoiding negative pressure-induced flow obstruction).

2. Mold Precision and Maintenance

• • Mold manufacturing precision: Punch-die coaxiality ≤0.02mm, flatness ≤0.01mm/100mm—avoid uneven material stress due to poor centering;

• • Regular maintenance: After processing 1,000 pieces, repair mold fillets with diamond grinding wheels (removing wear marks) and clean vent holes with ultrasonic waves (preventing aluminum chip blockage); ensure no scratches on the mold surface (depth <0.01mm).

At this stage, Prevention of problems with aluminum discs used in kitchenware relies heavily on the synergy of material selection, process regulation, and mold optimization—each link complements the others to minimize defect risks.

4. Full-Process Quality Control System: Defect Interception from Source to Finished Product

(1) Incoming Raw Material Inspection (Key Indicators)

1. Composition analysis: Use direct-reading spectrometers to test Mn (1.0%-1.5%) and Si (≤0.6%) in 3003 aluminum, and Mg (2.2%-2.8%) in 5052 aluminum—ensure compliance with GB/T 3880.2-2022 (National Standard of the People’s Republic of China for Aluminum and Aluminum Alloys – Part 2: Chemical Composition of Wrought Products);

2. Mechanical properties: Sample 5 pieces per batch for tensile testing (GB/T 228.1-2021); reject the entire batch if elongation is 10% lower than the standard value;

3. Appearance inspection: Use CCD visual inspection (accuracy 0.01mm) to identify surface scratches and inclusions; rework if the defective rate exceeds 2%.

(2) Real-Time Monitoring During Processing

1. Online inspection: Install industrial cameras (shooting frequency 30 frames/s) to real-time identify wrinkling (wrinkle height >0.5mm) and cracking (crack length >1mm); stop immediately for adjustment if defects are found;

2. Parameter recording: Store drawing force, blank holder force, and speed data for each product via MES (Manufacturing Execution System) to form a process traceability chain; trigger an alert if parameter fluctuation exceeds ±10%.

(3) Finished Product Inspection Before Delivery

1. Appearance: Visual + tactile inspection—no visible cracking or wrinkling (local protrusion ≤0.2mm), and no burrs on edges (height ≤0.1mm);

2. Dimensions: Use a coordinate measuring machine to test the finished diameter (deviation ±0.2mm), depth (deviation ±0.1mm), and wall thickness uniformity (maximum deviation ≤10%);

3. Mechanical verification: Sample pressure tests (0.3MPa pressure holding for 30s with no deformation for pots) and drop tests (1.2m drop height with no cracking).

5. Industry Application Cases: Optimization from 18% Defect Rate to 3%

Case 1: Deep-Drawn Pots with 3003 O Temper Aluminum Discs (Depth 60mm, t=2.5mm) in a Kitchenware Factory

1. Original problems: 12% cracking rate and 6% wrinkling rate—caused by excessive drawing ratio (2.4), too small mold fillet (R=8mm), and insufficient blank holder force (4,500N);

2. Optimization solutions:

• • Process adjustment: Split drawing ratio into two stages (first 2.0, secondary 1.6); increase blank holder force to 6,000N (calculated as F=1.5×2.5×200);

• • Mold improvement: Increase fillet R to 15mm (7t), set single-sided clearance to 2.7mm (1.08t), and add 4 φ1.5mm vent holes;

3. Results: Defect rate reduced to 3% (0.8% cracking, 2.2% wrinkling), pass rate increased by 15 percentage points, and unit cost decreased by 22%.

Case 2: Shallow-Drawn Frying Pans with 5052 H14 Temper Aluminum Discs (Depth 25mm, t=1.8mm)

1. Original problem: 10% wrinkling rate—caused by insufficient blank holder force (2,000N) and excessive drawing speed (2.5m/s);

2. Optimization solutions: Adjust blank holder force to 2,700N (F=1.0×1.8×150), reduce speed to 1.2m/s, and switch to dry lubricant;

3. Results: Wrinkling rate reduced to 0, and production efficiency increased by 30% (from 120 pieces/h to 156 pieces/h).

6. Future Trends: In-Depth Integration of Intelligent Technology and Material Innovation

1. Intelligent process regulation: Introduce AI visual inspection (recognition accuracy 0.05mm) + adaptive control systems to real-time adjust blank holder force and speed (response time <0.1s), forming a “defect prediction-parameter self-optimization” closed loop;

2. Material upgrading: Develop “3003 + trace Zr” composite aluminum alloys (elongation increased to 28%, tensile strength maintained at 115MPa) to adapt to larger drawing ratios (first drawing ratio 2.4);

3. Mold technology innovation: Adopt 3D printed molds (SLM metal printing, surface roughness Ra ≤0.2μm) to achieve integrated forming of complex cavities and reduce material flow resistance.

Prevention of problems with aluminum discs used in kitchenware will further leverage intelligent and innovative technologies to achieve higher efficiency and lower defect rates in the future.

7. Conclusion

The prevention of “cracking” and “wrinkling” in the stamping and drawing of aluminum discs for kitchenware centers on the collaboration of material selection and pretreatment, quantitative optimization of process parameters, and precise mold structure design. It is necessary to take “matching alloy properties with processing requirements” as the foundation, “dynamic regulation of process parameters” as the core, and “full-process quality control” as the guarantee. Meanwhile, integrating intelligent technology and material innovation will fundamentally solve industry pain points and achieve the goal of “high pass rate + low cost + high performance” in processing.