Energy consumption in the mass production of PM components
A paper by Vladislav Kruzhanov and Volker Arnhold, GKN Sinter Metals Engineering GmbH, Germany, on “Energy Consumption in the Mass Production of PM Components” was presented by Mr. Narsi Chandrachud, GKN Sinter Metals Ltd., India.
The speaker discussed energy consumption in Powder Metallurgy (PM) especially in terms of competitive processes such as casting, forging and machining. He then went on to explain the breakdown of energy consumption in PM, with particular focus on powder production, powder compaction, and sintering amongst other processes. The talk concluded with the economic aspects of energy savings in PM.
PM presents cost effective ways for mass production of intricate specialised components. Due to the advances in PM technology die-casting, forging, machining and other traditional processes now face strong competition. Further usage of PM is necessary to combat the rising energy costs and adhere to CO2 emissions legislation.
As the energy consumed is dependent on the size of component and type of process used, the paper theorised that the average energy consumption at GKN Sinter Metals (5 kWh/kg) would be reasonably representative of the PM industry.
Additionally the paper states that the average energy used for production of water atomised powder (1.8 kWh/kg) at Hoeganaes Corp. (owned by GKN) would also be representative of the powder production industry as a whole.
Compared to the energy consumption for crude steel production of approximately 5 kWh/kg, 2 kWh/kg for water atomisation of scrap metal is relatively low. However, sponge iron powder produced from magnetite (Fe3O4) requires a larger amount of energy (approximately 4 kWh/kg).
Energy consumption for die-casting of iron-based materials is in the range of 6 kWh/kg, for forging in the range of approximately 2.5 kWh/kg and for machining in the range of 10 kWh/kg, typically twice the amount of energy compared to PM.
The most widely used powder metallurgy route is press and sinter. Energy consumed in the mass production of PM components was estimated by summation of the energy consumed in individual processes such as in the production of water atomised powder, blend preparation, compaction, de-lubrication, sintering , sizing, heat treatment and others.
Powder production by water atomisation requires energy of 2.1 kWh/kg while theoretical considerations showed that it can further be reduced to 0.85 kWh/kg.
The average energy consumption for compaction (mechanical, hydraulic and hybrid presses) was estimated to be approximately 0.8 kWh/kg.
The energy balance during sintering was investigated in a 300mm wide experimental electric belt furnace. A typical sintering profile for ferrous components was considered. Energy consumption in each heating zone, temperature and consumption of water in each cooling zone, power of the belt drive, temperature of the components during sintering and surface temperature of the furnace casing were measured. The “productive” heat for heating parts was found to be 0.13 kWh/kg (theoretical 0.14 kWh/kg).
With a throughput of 75 kg/h, an energy consumption of 0.5 kWh/kg of sintered parts was observed where the “productive” heat accounted for only 30% of the energy used.
The remaining energy was dissipated from the furnace, i.e. the efficiency of the furnace was below 30%. A recuperation of the energy derived from the gas and water could increase the efficiency of the furnace while good heat insulation could minimise the “unproductive” heat significantly. After considering the energy consumed in the sizing and post sintering operations the energy consumed in sintering operation was found to be 1.5 kWh/kg, or 30% of total energy (5 kWh/kg) consumed in the production of ferrous parts by PM.
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