1060 アルミニウム丸シート調理器具延伸成形: 底割れと肉厚の不均一を制御する方法?

1060 aluminum alloy is the preferred material for deep drawing of aluminum cookware (ポット, ボウル, 盆地, 等) due to its excellent plasticity, 良好な熱伝導性, and low cost. しかし, bottom corner crackingそして 不均一な壁の厚さ​ are two high-frequency defects in the deep drawing process, directly affecting the yield rate, 強さ, and service life of the final product. This article systematically analyzes the causes from four dimensions—material, mold, プロセス, and equipment—and proposes a full-process control scheme to achieve stable, high-quality forming of 1060 アルミ調理器具.

私. Core Defect Mechanisms in Deep Drawing of 1060 Aluminum Disc Cookware

(私) Bottom Cracking: Stress Overload Failure at the Critical Section

During cookware drawing, the material stress is divided into three zones: the punch bottom (hydrostatic pressure, difficult to deform), the side wall (radial tensile stress + tangential compressive stress, main deformation zone), and the bottom corner (tangent point between the punch R-angle and side wall, どこ stress concentration is most severe).

• Mechanical Essence: The bottom corner experiences the superposition of radial tensile stressそして bending stress. When the stress exceeds the tensile strength of 1060 アルミニウム (110-145MPa, 気性が荒い), micro-cracks initiate and propagate, forming through-thickness cracking.
• Key Contributing Factors
  1. Unbalanced Material Flow: Excessive blank holder force or too small a die R-angle hinders the flow of the blank edge, causing the bottom to be forcibly stretched and “pulled apart.”
  2. Stress Concentration: An excessively small punch R-angle or rough surface leads to local stress far exceeding the material limit.
  3. Insufficient Material Properties: 1060 aluminum not annealed (H18/H24 temper), coarse grain size, surface scratches/impurities, significantly reducing plasticity.
  4. Mismatched Process Parameters: Excessive drawing speed, poor lubrication, drastically increasing frictional resistance, leading to bottom stress overload.

(Ⅱ) Uneven Wall Thickness: Spatial Differences in Material Flow Rates

Different degrees of deformation in various parts of the blank during drawing result in thicker upper side walls and thinner bottom corners. 重症の場合, the thickness difference exceeds 30%, directly affecting the strength and uniformity of the cookware.

• Root Causes
  1. Flow Rate Difference: Material at the die opening, subjected to tangential compressive stress, tends to thicken and flow faster; the bottom corner, subjected to tensile stress, tends to thin and flow slower. This rate difference causes uneven wall thickness distribution.
  2. Uneven Die Clearance: Poor concentricity between punch and die, excessive or insufficient clearance, causing excessive unilateral squeezing of the material, leading to local thinning or wrinkling.
  3. Uneven Blank Holder Force Distribution: Insufficient rigidity of the blank holder, unbalanced ejector pin forces, causing inconsistent inflow speed of the edge material, resulting in wavy wall thickness fluctuations.
  4. Blank Defects: Aluminum disc thickness tolerance exceeding ±5%, anisotropy (plasticity difference along rolling direction), causing thickness deviation during deformation.

Ⅱ. 材料管理: Enhancing Forming Stability from the Source

The temper, 微細構造, and surface quality of 1060 aluminum are the foundation for controlling cracking and uneven wall thickness.

1. Optimal Material Temper: O-Temper Annealing as the Core

• Preferred Temper: 1060-O fully annealed aluminum discs, with elongation ≥25%, hardness HB30-35, offering the best plasticity, 深絞り加工に適しています.
• Precise Annealing Process Control
  • 温度: 320-340℃ (complete recrystallization, avoiding grain coarsening);
  • Soaking time: Thickness ≤1mm → 30-45min, 1-2mm → 45-60min;
  • 冷却: Furnace cool to below 200°C before unloading, relieving internal stress and refining grains (grain size ≤ grade 5).
• Avoided Tempers: H18 (フルハード, 伸長 <10%), H24 (half hard, prone to cracking in deep drawing), suitable only for shallow drawing of small parts.

2. Strict Blank Quality Control

• 厚さの許容差: Controlled within ±3%​ (例えば, 0.8mm blank → 0.776-0.824mm) to prevent amplification of initial unevenness.
• 表面品質: 傷なし, rust, scale, hard inclusions; Degrease and clean​ before drawing (アルカリ脱脂 + water rinse + drying) to remove oil, contaminants, preventing uneven friction and cracking.
• 寸法精度: Aluminum disc shearing to be burr-free, ovality ≤0.5%, ensuring symmetrical force application during drawing.

Ⅲ. Mold Design and Optimization: Eliminating Stress Concentration, Balancing Material Flow

The mold is the core for defect control, focusing on optimizing four key elements: corner radii, クリアランス, 表面, and blank holder system.

1. Corner Radii: の “Buffer Valve” for Stress Concentration

An excessively small corner radius is the primary mold-related cause of bottom cracking, requiring precise design based on material thickness (t):

• パンチ半径 (Rp): ≥ 4t​ (例えば, t=0.8mm → Rp≥3.2mm); Commonly used Rp=3-5mm for cookware. Larger radii are less prone to cracking, but too large can cause wrinkling.
• ダイ半径 (Rd): ≥ 6t​ (例えば, t=0.8mm → Rd≥4.8mm); Excessively small Rd hinders material inflow, drastically increasing bottom stress.
• Transition Treatment: Smooth transition between punch bottom and R-corner, side wall and R-corner, free of sharp corners or tool marks, polished to Ra ≤0.2μm.

2. Punch-Die Clearance: の “Gauge” for Wall Thickness Uniformity

Clearance directly determines the amount and uniformity of side wall thinning. Standard clearance for 1060 aluminum cookware drawing:

• Conventional Drawing: Clearance Z = (1.05-1.15)t​ (t is blank thickness);
  • 浅い描画 (depth-to-width ratio <1): Z=1.05t, wall thinning ≤5%;
  • 深絞り加工 (depth-to-width ratio 1-1.5): Z=1.1t, wall thinning 8-12%;
  • Extra-deep drawing (depth-to-width ratio >1.5): Z=1.15t, preventing excessive bottom thinning and cracking.
• Precision Requirement: Clearance tolerance ≤ 0.02mm, punch-die concentricity ≤0.02mm, consistent clearance at all four corners.

3. Mold Surface and Structure: Reducing Friction, Enhancing Rigidity

• Surface Hardening Treatment: Punch, 死ぬ, and blank holder treated with TD coatingまたは hard chrome plating, hardness HV1200+, for wear resistance, friction reduction, preventing scoring and uneven friction.
• Blank Holder System Optimization
  • Blank Holder: 使用 QT600-3 ductile iron​ or H13 steel for sufficient rigidity, preventing deformation;
  • Ejector Pin Layout: Evenly distribute 8-12 ejector pins, with corner pin forces 10-15% higher than center pins, ensuring uniform blank holder pressure;
  • Variable Blank Holder Force Structure: Use nitrogen cylinder groups to achieve dynamic adjustment: “high initial pressure → low forming pressure → high final pressure”.
• Auxiliary Structures: 追加 draw beads​ on the die (shallow beads, moderate resistance) to regulate edge material flow; 追加 vent holes​ on the punch bottom (φ1-2mm) to prevent vacuum-induced excessive bottom contact and thinning.

Ⅳ. Precise Control of Process Parameters: Dynamic Balance for Stable Forming

Process parameters (blank holder force, スピード, 潤滑, number of draws) are key for on-site调试. They must match the material and mold to achieve “material flows properly, stress does not exceed limits“.

1. ブランクホルダーフォース: の “Master Switch” for Material Flow

Excessive force → bottom cracking; Insufficient force → wrinkling, 不均一な壁の厚さ. Must be set precisely based on blank size and drawing depth:

• Calculation Formula: Blank holder force F = (0.3-0.5) × Annular area of blank × Material yield strength​ (1060-O yield strength ≈90MPa).
• Dynamic Adjustment (Variable Blank Holder Force)
  • Initial Stage (blank contacts mold): 3.5-4 MPa, preventing edge wrinkling;
  • Forming Stage (material flows into cavity): 2-2.5 MPa, reducing bottom tensile force, avoiding cracking;
  • Final Stage (forming complete): 3-3.5 MPa, correcting side wall thickness, preventing springback.
• On-site Judgment: With proper blank holder force, the blank edge shows no wrinkles, the bottom shows no cracks, and side wall thickness is uniform. If bottom cracks → ブランクホルダーの力を軽減; if edge wrinkles → increase blank holder force.

2. 描画速度: の “Pace Setter” for Stress Relief

1060 aluminum plasticity is sensitive to strain rate. Too fast → stress concentration, ひび割れ; Too slow → low efficiency.

• Stepped Speed Control
  • Fast Downward Stroke: 50-80 mm/s (idle travel, 効率の向上);
  • Contact Forming: 5-10 mm/s (critical stage, slow speed allows uniform material flow, stress relief);
  • Holding & Return Stroke: 10-15 mm/s (hold for 2-3s, eliminating springback, stabilizing wall thickness).
• Equipment Requirement: 使用 CNC hydraulic presses​ with closed-loop speed control to avoid impact and fluctuations.

3. Lubrication System: の “Decelerator” for Frictional Resistance

Poor lubrication increases the friction coefficient above 0.3, raising bottom stress by 30%+, a primary cause of cracking.

• Lubricant Selection: Special drawing oil for 1060 アルミニウム​ (containing extreme pressure additives), kinematic viscosity 68-100 mm²/s at 40°C, または graphite paste + engine oil​ mixed lubricant.
• Lubrication Method: Apply evenly on both sides, reapply every 200 strokes; Maintain complete oil film on mold surface (especially R-corners), avoiding dry friction.
• Effect Assessment: 形成後, the workpiece surface is smooth, free of scoring, friction coefficient <0.12, bottom shows no overheating discoloration.

4. 多段描画: の “Decomposition Method” for Complex Cookware

For cookware with depth-to-width ratio >1.5 (例えば, deep stock pots, 炊飯器の内釜), single-stage drawing is prone to cracking and uneven wall thickness. 2-3 drawing stages​ are required to distribute deformation.

• Stage Allocation
  • ステージ 1: Draw to 60-70% of total depth, with enlarged bottom punch radius (1.2 times final value) and enlarged clearance (1.2 times final value);
  • 中間焼鈍: 300-320℃, hold for 30min, eliminating work hardening, restoring plasticity;
  • ステージ 2/3: Gradually reduce corner radii and clearance to final dimensions, improving wall thickness uniformity to within ±8%.

V. Equipment and Process Control: Ensuring Process Stability

1. Equipment Accuracy Requirements

• 使用 200-500KN CNC hydraulic presses, slide parallelism ≤0.05mm/m, perpendicularity ≤0.03mm/m, blank holder force repeatability ±1%.
• Blank Holder System: 使用 independent hydraulic blank holder cylinders​ or nitrogen cylinders, avoiding uneven mechanical blank holder force.

2. Online Monitoring and Debugging

• 初品検査: Check the first piece of each batch for bottom corner (亀裂なし), wall thickness (6 ポイント: upper/middle/lower/four corners, difference ≤10%), 寸法精度.
• Rapid Defect Troubleshooting
  • Bottom corner cracking: → Increase Rp/Rd, ブランクホルダーの力を軽減, optimize lubrication, slow down forming speed;
  • Excessive thickness at upper side wall, excessive thinning at bottom: → Increase die clearance, reduce final stage blank holder force, adjust draw bead resistance;
  • Unilateral uneven wall thickness: → Correct mold concentricity, adjust ejector pin force distribution, re-grind blank holder surface.

3. Mold Maintenance

• Inspect mold R-corners, surface wear every shift, polish promptly (Ra ≤0.2μm);
• Replace worn ejector pins, nitrogen cylinders regularly to ensure stable blank holder force;
• Perform comprehensive inspection of mold clearance, 同心, rigidity every 5000 strokes.

VI. Integrated Control Scheme and Effect Verification

(私) Standard Process Parameters (例: 0.8mm 1060-O Aluminum Disc, 240mm Diameter Deep Pot)

(Ⅱ) Effect Verification

After implementing the above scheme for 1060 aluminum cookware deep drawing:

• Bottom cracking rate: Reduced from 15-20% に <1%;
• Wall thickness uniformity: Thickness difference controlled within ±7%, meeting cookware strength standards;
• 歩留まり率: Increased from 75% to over 98%, significantly reducing production costs.

Ⅶ. 結論

Bottom cracking and uneven wall thickness in deep drawing of 1060 aluminum disc cookware result from the coupling of multiple factors: 材料, mold, プロセス, and equipment. The core of control lies in: using O-temper annealed material as the foundation, employing molds with large corner radii and uniform clearance as the carrier, implementing variable blank holder force, 低速, and strong lubrication processes as the means, and relying on high-precision equipment as the guarantee, to achieve “uniform flow, balanced stress, and controllable deformation” of the material.