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 Post subject: Question for the Metallurgists/Metalworkers
PostPosted: Thu Aug 14, 2025 6:43 pm 

Joined: Sun Aug 22, 2004 11:54 pm
Posts: 2573
Is a solid part being made simply from the application of pressure and not from melting?

https://www.youtube.com/shorts/4flmQbopeBs


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 Post subject: Re: Question for the Metallurgists/Metalworkers
PostPosted: Thu Aug 14, 2025 7:18 pm 

Joined: Sun Aug 22, 2004 1:51 pm
Posts: 11903
Location: Somewhere east of Prescott, AZ along the old Santa Fe "Prescott & Eastern"
This is "sintering":

https://en.wikipedia.org/wiki/Sintering

A powdered metal alloy is first compressed to shape, then heated in a sintering oven to a bonding temperature. This method of production allows for self lubricating materials and various alloy-formed parts that can not be produced by other methods.


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 Post subject: Re: Question for the Metallurgists/Metalworkers
PostPosted: Thu Aug 14, 2025 9:54 pm 

Joined: Fri Aug 20, 2010 8:25 pm
Posts: 510
Sintering compresses metal powder into a solid shape. It is heated to a "bonding" temperature below the temperature where the metal totally melts.

Widely used (before high performance plastics) as bushings in home appliances (Fans, Air Conditioners, Washing Machines, Clothes Dryers, etc.) and automobiles. The final bonded metal is like a sponge and can be saturated with oil. Easier to make than solid metal bushings and normally does not need an external oil supply (oil cups, grease fittings, etc) for the limited lifetime of a home appliance.

Most 20th century Automotive starter motors used sintered bronze bushings to support the motor shaft. Inexpensive, "permanently lubricated", and could last 5-10 years. You can purchase oil impregnated bronze bar stock to make custom sized bushing to restore many old starter motors, fan motors, etc. Automotive generators and alternators usually used ball bearings since they rotated the whole time an engine was running.

Cheaper than ball bearings and not regularly used for "Heavy Industrial" applications.

Mostly Bronze metals.

Not used for structural members.

https://oilite.com/oilite

Comes in "Food Safe" versions (with mineral oil), "Marine" versions (impervious to salt water) and lots of other specialty versions. There are now "impregnated" plastic materials that combine PTFE and Bronze powders to make bushings that perform very much like a solid metal bushing.

As someone commented at that site, this is NOT forging. Forging raises the temperature of a metal above it's "plastic" temperature and compresses the metal together to make it denser and stronger.

The press used for sintering compacts metal powder grains closer together so they will "fuse" when heated to a temperature below the plastic state of the metal. Like warming up wax beads and pressing them together to make a wax sponge material.


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