For more than 50 years, ALD and it’s predecessors have manufactured sintering furnaces for hard metals, cermets, magnets, MIM products and special oxide ceramics.

The sintering process consolidates particles in a coherent, pre-determined solid structure. Mass transport in the atomic range happens during this process. Single-phase powders are sintered at 2/3 to 4/5 of their melting temperature, multi-phase powders (mixtures) are sintered near the solidus of the lowest melting phase.

Dewaxing Process

In order to produce PM parts, the powder (powder metal mixture) is pressed into near net shape before sintering. To reduce friction and press force, additives, such as paraffin, PEG and others, are added to the powders. They have to be removed in a dewaxing process before sintering, thus obtaining a pore-free and chemically predetermined material structure.

The Sintering Process

The sintering process happens in vacuum or under protective gas at the appropriate temperature for the material. A defined, reproducible sintering atmosphere without atmospheric oxygen is important. At certain pressures and temperatures the process gas feed during sintering with argon, N2, H2, CH4, CO2 and others may influence the structure and chemical composition of the workpieces.

1. Various micro tools from cemented carbides, 2. Vacuum furnace for dewaxing and vacuum sintering, type VKPgr 50/50/170 with integrated rapid cooling system, 3. Coated, cemented carbide drills

Overpressure Sintering (HIP)

Following the vacuum sintering process, 6 to 10 MPa Argon gas is introduced into the furnace at sintering temperature to further reduce porosity and to ensure the material quality of high-performance hard metal tools and other sintered parts.

Applications of Sintering Furnaces

Dewaxing, vacuum sintering and/or overpressure sintering at 6 to 10 MPa for hard metal materials and powder metallurgical products.
• Dewaxing, vacuum sintering and overpressure sintering of wear and tear parts
• Sintering of hard metal tools and micro drills
• Sintering of MIM parts (metal injection moulded)
• Dewaxing and sintering of UO2 and MOX pellets for nuclear fuel elements
• Sintering and heat treatment of rare earth permanent magnets.

Furnace line VKPgr

The features of this furnace line are:
• One single furnace performs up to 4 different dewaxing processes
• High temperature uniformity
• Special graphite felt insulation with long service life
• Graphite heating with integrated, closed graphite muffle
• Two integrated and one external rapid cooling systems to reduce cycle time
• Metallurgical treatment of workpieces using process gases
• Operating pressure 6 MPa or 10 MPa

Furnace line VKUgr

The new VKUgr furnace line meets market demands for a "fast sintering furnace" for small and medium loads and various types of dewaxing processes and process parameters.

The features of this furnace line are:
• One single furnace performs up to 4 different dewaxing processes
• High temperature uniformity
• Graphite insulation
• Graphite heating
• Integrated, controllable rapid cooling system
• Metallurgical treatment of workpieces using process gases

Furnace line VKMQ

The features of the VKMQ furnace line are:
• Rated temperature up to 1300 °C in vacuum or under convection
• Durable graphite heating with hard felt insulation
• Integrated, large-sized heat exchanger with fan for high-pressure gas cooling to be used for rare earth magnet sintering

Furnace line GWSmo

Pusher type furnaces with hydrogen atmosphere, ceramic brick lining for insulation, molybdenum heaters for sintering of UO2 pellets or MOX pellets, being used for nuclear fuels.

1. Vacuum dewaxing and sintering furnace type VKUgr,
2. Pusher furnace for sintering of MOX pellets type GWSmo,
Example of the use of up to 100 magnets in high-quality cars