29-05-2012, 01:30 PM
Advances in Powder Metal Sintering Technology
Advances in Powder Metal Sintering Technology.pdf (Size: 167.09 KB / Downloads: 76)
Introduction
The traditional powder metal process, often referred
to as “press and sinter”, is constantly driven to change by an
industry goal of entering new markets through substitution
and the development of innovative products for new
applications. Although much advancement has been made in
the area of compaction, new materials and sintering
technology continue to broaden the applications and improve
the overall quality and competitiveness of powder metal
components.
The goal of any sintering furnace is to provide a
consistent, repeatable and economical relationship between the
times that a part is in each location of the furnace, the
temperature of the part as it travels through the furnace and the
atmosphere seen by the part during each stage of the sintering
process.
Advancements
The areas of advancement in sintering technology and
equipment can be grouped into five technological groupings.
• De-Lubrication
• High Temperature Sintering
• Sinter Hardening
• Sintering Atmosphere
• Furnace Connectivity and Control
De – Lubrication
Lubricants are blended into the metal powders prior
to compaction to reduce inter-particle friction and aid in
ejecting the compact from the die of the compaction press.
Although these hydrocarbons are beneficial to the compaction
process, they must be removed from the compact before
sintering can take place.
A great deal of work has been done on the removal of
lubricants from compacts. Many devices such as bubblers,
humidifiers and auxiliary combustion systems have been
developed to aid in the removal of the lubricants. These
systems are designed to introduce some source of oxidant,
such as water vapor, oxygen and carbon dioxide, into the
preheat section of a furnace. This water vapor is a source of
oxygen for the reaction of any carbon that results from the
decomposition of the lubricant as it is exposed to high
temperatures.
High Temperature Sintering
For many decades, 2050oF has been the standard
sintering temperature for ferrous powder metal components.
At this temperature the powder metal particles will diffuse
together to form a solid component with some degree of
porosity. This porosity has proven to be beneficial in
applications such as self lubricating bearings. However, the
porosity has also limited the application of powder metal
components in some designs due to a shortfall in properties
when compared to wrought components.
Sintering Hardening
The use of convective cooling units to rapidly cool
sintered component to a high hardness continues to expand the
applications and reduce the cost of powder metal components.
The designs of convective cooling units that are used
in sinter hardening continue to improve. Higher cooling rates
and an improvement in the ability to control the atmosphere
flow in the furnace continue to reduce the need for alloys in
the materials that were once needed to achieve hardness.
Furnace Connectivity and Control
Control of a sintering furnace can range in
complexity from the very simple stand alone controllers to
advanced computer systems. In the age of the internet and cell
phones, furnace manufacturers and users are beginning to
incorporate these technologies into the sintering furnaces.
Real-time remote monitoring systems are being used
to record information for both quality control and preventative
maintenance. Information about power draw can be
automatically sent to the furnace manufacturer on a routine
basis for their review and recommendations on maintenance