1. Definition and Purpose
A sintering furnace is specialized equipment that heats powder compacts to achieve desired physical, mechanical, and microstructural properties.
- Used to dry paste on silicon wafers, remove organic components, and complete aluminum back contacts and grid line sintering.
- Enables powder metallurgy parts, hard alloys, and ceramics to consolidate into dense, usable components.
2. Principle of Vacuum Sintering Furnaces
- Operates under a vacuum or protective atmosphere to prevent oxidation.
- Heating methods include:
- Resistance heating
- Induction heating (vacuum induction furnaces)
- Microwave heating
- Magnetic-saturated core reactors for precise temperature control
- Vacuum induction sintering furnaces use medium-frequency induction to sinter hard alloy tools, metal powders, and ceramics.
- Designed specifically for hard alloys, metallic dysprosium, and ceramic industrial production.
3. Detection of Furnace Lining Thickness
Accurate monitoring of furnace lining is crucial for longevity and performance. Methods include:
- Stress Wave Method:
- Sensitive to structural defects.
- Waves reflect, refract, scatter at cracks, pores, or discontinuities.
- Measures cooling wall thickness.
- Capacitance Method:
- Embeds coaxial circular capacitors in the lining.
- Capacitance correlates with length; measurement determines lining thickness.
Components of the sintering furnace:
- Furnace body, vacuum system, water-cooling system, pneumatic & hydraulic systems, feed & discharge mechanisms, base, worktable, induction heating elements (tungsten heaters + insulation), power supply, and electrical control system.
4. Furnace Operation Considerations
- Powder compacts have large free surfaces; sintering usually requires a protective atmosphere.
- Surface oxide films on metal powders must be reduced during sintering to ensure bonding.
- Compaction-induced internal stresses need removal during sintering.
- Volatile additives in compacts must be removed during the heating stage.
5. Furnace Bottom Sintering Layer
- Furnace bottoms must be sintered at sufficiently high temperatures with adjusted material composition to form durable and long-lasting sintering layers.
- Some advanced factories use iron oxide sintering layers for improved furnace life.
- Widespread adoption is slow due to:
- Lack of a universally recognized sintering layer formation theory
- Varied methods for materials, mix ratios, and temperature schedules
Summary:
Powder metallurgy sintering furnaces are highly specialized and sensitive systems, requiring careful control of atmosphere, temperature, compaction, and lining quality. Selecting proper materials and methods ensures efficient sintering, extended furnace life, and high-quality powder-metal products.