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lynyrdsky1

Metal Melting question?

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I know that lead has a very low melting point but, how are you able to melt tungsten since it has a very high density and melting point. The only thing I can think of is using a plasma cutter but it will just cut threw it. I was also thinking of freezing the tungsten, which will slow down the molecules, and then heating it at a rapid rate, which will speed up the molecules. But all this may do is either just crack and break the metal or nothing at all.

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What?  Huh?  Why?

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It has just been something flowing around in my head. Wondering how companies are able to form tungsten.

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Tungsten has a ridiculous melting point (~3400 *C).  In order to truly melt  it under standard conditions, you have to heat it above that temperature.  I don't know exactly how it's done, but I do know that solids can be "molded" into specific shapes from a powdered form the metal, which can be done at a lower temperature than the mp.  This is called "sintering."

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You could likely get it hot enough to melt with an Oxy/Acetylene torch, but whatever you poured it into to cast a sinker would be destroyed instantly. Tungsten powder is mixed with cobalt and cold pressed into the form of fishing weights, then they are heated in a scintering oven to make a finished weight.

Ronnie

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You could likely get it hot enough to melt with an Oxy/Acetylene torch, but whatever you poured it into to cast a sinker would be destroyed instantly. Tungsten powder is mixed with cobalt and cold pressed into the form of fishing weights, then they are heated in a scintering oven to make a finished weight.

Ronnie

So most baits are made with a cobalt/tungsten mixture?

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If you are wondering about tungsten weights they are machined ;)

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So most baits are made with a cobalt/tungsten mixture?

Yep, cobalt is used as a binder to hold the tungsten powder together while it is scintered.

Ronnie

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Tungstun is a powdered metal, it is not melted like say steel, but is mixed into a slurry and "formed".

               -gk

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Tungsten Carbide is probably what fishing weights are made of, which probably has a lower melting point. But I thought I read it was around 1600°F?

[edit]Nevermind, answered above. :)[/edit]

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I've always wondered if they just pressed them and used pressure instead of heat.

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I used to roll form tungsten from sintered billets into sheet and plates, and it had to be heated to 1550*C or it would crack once the pressure was applied. It also had to be reheated after each pass thru the rollers or it would shatter from the stress. Really difficult stuff to work with.

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Just a side bar to sintered metals. When I was in the scrap metal business I serviced an account for 25 years that made parts from powdered iron. The process mentioned is exactly correct. Powder metal, in my case iron, is blended with some elements like nickle and copper, very small amounts less than 1%, different parts require different blends. The blend is put into a press and pressed under pressure from 400 tons to 1000 tons, now you have part. This part can be crumbled in your hand or dropping it on the floor. The next step is heat treating. The parts are placed on nickle alloy "belts " 25/20 or 35/15 alloy and run thru a very hot furnace for a period of time, and out pops a very hard piece of metal that most would think is steel, but it isn't. What I found interesting when I first got this account was the use, parts go into automobile, transmission and rear end gears, clutch plates, and a few other things I can't remember.

The powdered metal capital of North America is St Marys & Ridgway , Pennsylvania.

I am totally unfamiliar with the process regarding tungsten sintering.

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No problem. If you have a heat source of 6170* f :o

http://www.tungsten.com/mtstung.html

I finally had a chance to check out this link. I've actually done the swaging and wire drawing processes mentioned in the "How tungsten wire is produced", along with the straightening process which is used to make welding electrodes from the drawn wire.

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