In glass manufacturing, the annealing process is critical for eliminating internal stresses formed during shaping. At the heart of this process lies the metal conveyor belt, a component that directly impacts annealing efficiency, product quality, and operational costs. This blog explores the vital roles of conveyor belts in glass annealing lehrs and compares the materials commonly used in their construction.
They ensure uniform heat distribution across glass products (e.g., bottles, panels) as they pass through heating, soaking, and cooling zones. Any temperature inconsistency can lead to residual stress or deformation.
By maintaining precise transit speeds and stable support, conveyor belts allow gradual stress relaxation within the glass structure at the annealing point (typically 510–600°C for soda-lime glass).
They bear the weight of glass products while resisting thermal expansion and mechanical wear, especially crucial for heavy or thick-walled items.
Belts must withstand prolonged exposure to high temperatures, oxidation, and occasional chemical corrosion from glass surface treatments (e.g., coatings).
Material selection depends on temperature ranges, environmental conditions, and cost considerations. Below are the most widely used options:
304 Stainless Steel
Max Temperature: 800°C
Properties: Cost-effective, excellent corrosion resistance, and smooth surface finish.
Applications: Ideal for soda-lime glass annealing (≤650°C), such as bottle production.
310S (0Cr25Ni20)
Max Temperature: 1100°C
Properties: High nickel-chromium content ensures superior oxidation resistance and structural stability under cyclic heating.
Applications: High-temperature processes like borosilicate glass annealing.
316/316L Stainless Steel
Max Temperature: 800°C
Properties: Molybdenum addition enhances corrosion resistance in acidic or humid environments.
Applications: Pharmaceutical or chemical glassware lehrs with coating treatments.
314 Stainless Steel
Max Temperature: 1150°C
Properties: High silicon content boosts oxidation resistance beyond 310S.
Drawbacks: Higher cost and limited weldability.
Inconel 600/601
Max Temperature: 1150°C
Properties: Nickel-chromium alloy with exceptional creep resistance and longevity.
Applications: Specialty glass (e.g., optical, LCD) requiring ultra-stable annealing.
A3 Mild Steel
Max Temperature: 400°C
Properties: Low cost but prone to oxidation. Requires frequent replacement.
Applications: Pre-annealing or low-budget setups.
Aluminized Steel
Max Temperature: 600°C
Properties: Aluminum coating mitigates oxidation, extending lifespan over plain carbon steel.
Molybdenum Disilicide (MoSi2)-Coated Belts
Max Temperature: 1300°C
Properties: Extreme oxidation resistance and minimal thermal expansion.
Applications: High-end lehrs for technical glass (e.g., fiberglass, vitrified ceramics).
| Material | Max Temp | Corrosion Resistance | Cost | Typical Use Cases |
| 304 Stainless | 800°C | Good | $$ | Bottles, jars |
| 310S Stainless | 1100°C | Excellent | $$$$ | Borosilicate, tempered glass |
| 316 Stainless | 800°C | Excellent (acidic) | $$$ | Labware, coated glass |
| Inconel 601 | 1150°C | Outstanding | $$$$$ | Optical, LCD glass |
| Aluminized Steel | 600°C | Moderate | $ | Low-temperature annealing |
Temperature: Match the belt’s max temperature to your lehr’s peak operating range.
Environment: Opt for 316 stainless in acidic conditions or MoSi2 coatings for extreme heat.
Load Capacity: Heavy products (e.g., automotive glass) demand high-strength alloys like Inconel.
Budget: Balance upfront costs with long-term savings—cheaper belts may incur higher replacement fees.
The conveyor belt is the unsung hero of glass annealing, directly affecting product consistency and throughput. While stainless steels like 304 and 310S cover most industrial needs, niche applications require advanced alloys or coatings. Always validate material performance with stress tests and consult manufacturers to align specifications with your lehr’s requirements.
By selecting the optimal belt material, manufacturers can achieve stress-free glass products, reduce downtime, and maximize the lifespan of their annealing lehrs.
• Balanced weave lehr belt, comprising alternating right and left-hand flattened spirals connected by crimped rods. This design ensures locked-in spirals for straight tracking and product stability. Edges are welded for added durability.
• Compound balanced weave lehr belt, balanced spiral belt with multiple spirals and cross rods per pitch, resulting in minimal apertures and a flat surface. This structure ensures a close and flat mesh, ideal for conveying very small items.
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