All I can think is Wood's Metal.
But I'd think he's know that.

Wood's metal, also known as Lipowitz's alloy or by the commercial names Cerrobend, Bendalloy, Pewtalloy and MCP 158, is a eutectic, fusible alloy with a melting point of approximately 70 °C (158 °F). It is a eutectic alloy of 50% bismuth, 26.7% lead, 13.3% tin, and 10% cadmium by weight.

There has to be a downside to weld-additive construction. They'd have to do this in a vacuum or inert gas filled chamber to avoid oxidisation between layers.

I know you can't weld aluminium like this. Aluminium Oxide has a much higher melting point than aluminium, which is the main point of failure with aluminium welding.

Steel is a form of iron. Steel melts at about 1300 degrees Celsius (2400 Fahrenheit). It's boiling point is about 3000 C (or 5400 F).

Melting point of steel is around the temps he's talking about. Boiling point is a little higher.

Isn't this somewhat similar to mercury? low melting point and eats aluminum..

You mean in a death valley, one of the hottest place on earth, there's naturally occurring frozen carbon dioxide, whose melting point is -108.4°F (-78°C) and boiling point is -70.6°F (-57°C)?

Unlikely.

I think chocolate is just a good insulator. While it's melting point is much lower than other substances it cools faster, and the falloff of heat dispersion is a very short distance.

>> ^Trancecoach:

so because of the low melting point, the pewter liquifies when placed in the sand under plywood on the beach?


Looks like he has a little propane camping stove, you can see it very briefly at around 8 seconds.

so because of the low melting point, the pewter liquifies when placed in the sand under plywood on the beach?

No, he'd send weird materials up to the space station, and he'd run experiments to determine their melting points. It sounds cooler if you just say "melt stuff in space" though.

In reply to this comment by oohahh:
"melt stuff in space"? What does that mean? Like, shoot lasers at satellites? Suspend things in his shop and melt them with jets of hot air?

In reply to this comment by bmacs27:
Yea, the guy that made it used to melt stuff in space for a living, so I'm not surprised it came out pretty awesomesauce.

In reply to this comment by oohahh:
Best BM timelapse I've seen. Just forwarded it to portland@burningman.com in fact.

Thanks for uploading it!

In reply to this comment by bmacs27:
Thanks man!

In reply to this comment by oohahh:
*promote

As per wikpedia :

Benefits

The combination of fast joining times (on the order of a few seconds), and direct heat input at the weld interface, yields relatively small heat-affected zones. Friction welding techniques are generally melt-free, which avoids grain growth in engineered materials, such as high-strength heat-treated steels. Another advantage is that the motion tends to "clean" the surface between the materials being welded, which means they can be joined with less preparation. During the welding process, depending on the method being used, small pieces of the plastic metal will be forced out of the working mass (flash). It is believed that the flash carries away debris and dirt.

Another advantage of friction welding is that it allows dissimilar materials to be joined. This is particularly useful in aerospace, where it is used to join lightweight aluminum stock to high-strength steels. Normally the wide difference in melting points of the two materials would make it impossible to weld using traditional techniques, and would require some sort of mechanical connection. Friction welding provides a "full strength" bond with no additional weight. Other common uses for these sorts of bi-metal joins is in the nuclear industry, where copper-steel joints are common in the reactor cooling systems; and in the transport of cryogenic fluids, where friction welding has been used to join aluminum alloys to stainless steels and high-nickel-alloy materials for cryogenic-fluid piping and containment vessels.

Friction welding is also used with thermoplastics, which act in a fashion analogous to metals under heat and pressure. The heat and pressure used on these materials is much lower than metals, but the technique can be used to join metals to plastics with the metal interface being machined. For instance, the technique can be used to join eyeglass frames to the pins in their hinges. The lower energies and pressures used allows for a wider variety of techniques to be used.

http://en.wikipedia.org/wiki/Friction_welding

http://www.mtiwelding.tv/videos/index/31

In reply to this comment by rottenseed:
Why wouldn't you just make a mold that makes that whole piece?

I always wondered why to my mother that we couldn't just throw all the nuclear waste into a volcano like Kīlauea?? Could we? Have they!?
I think this is a good explanation. FROM INTERNET

Dumping all our nuclear waste in a volcano does seem like a neat solution for destroying the roughly 29,000 tons of spent uranium fuel rods stockpiled around the world. But there’s a critical standard that a volcano would have to meet to properly dispose of the stuff, explains Charlotte Rowe, a volcano geophysicist at Los Alamos National Laboratory. And that standard is heat. The lava would have to not only melt the fuel rods but also strip the uranium of its radioactivity. “Unfortunately,” Rowe says, “volcanoes just aren’t very hot.”

Lava in the hottest volcanoes tops out at around 2,400˚F. (These tend to be shield volcanoes, so named for their relatively flat, broad profile. The Hawaiian Islands continue to be formed by this type of volcano.) It takes temperatures that are tens of thousands of degrees hotter than that to split uranium’s atomic nuclei and alter its radioactivity to make it inert, Rowe says. What you need is a thermonuclear reaction, like an atomic bomb—not a great way to dispose of nuclear waste.

Volcanoes aren’t hot enough to melt the zirconium (melting point 3,371˚) that encases the fuel, let alone the fuel itself: The melting point of uranium oxide, the fuel used at most nuclear power plants, is 5,189˚. The liquid lava in a shield volcano pushes upward, so the rods probably wouldn’t even sink very deep, Rowe says. They wouldn’t sink at all in a stratovolcano, the most explosive type, exemplified by Washington’s Mount St. Helens. Instead, the waste would just sit on top of the volcano’s hard lava dome—at least until the pressure from upsurging magma became so great that the dome cracked and the volcano erupted. And that’s the real problem.

A regular lava flow is hazardous enough, but the lava pouring out of a volcano used as a nuclear storage facility would be extremely radioactive. Eventually it would harden, turning that mountain’s slopes into a nuclear wasteland for decades to come. And the danger would extend much farther. “All volcanoes do is spew stuff upward,” Rowe says. “During a big eruption, ash and gas can shoot six miles into the air and afterward circle the globe several times. We’d all be in serious trouble.”

For reference...

NIST report and press conference:
Sunder said that his team investigated these hypothetical causes [thermite] and ruled them out. "We asked ourselves what is the minimum amount of charge we could use to bring the building down," he said. "And we found that even the smallest charge would release an extremely loud sound heard half a mile away." There were no reports of such a sound; numerous observers and video recordings found the collapse to be relatively quiet.

FEMA:
The eutectic temperature for this mixture strongly suggests that the temperatures in this region of the steel beam approached 1,000 degrees C (1,800 degrees F), which is substantially lower than would be expected for melting this steel...

FEMA:
Temperatures in this region of the steel were likely to be in the range of 700 to 800 degrees C (1290 - 1470 degrees F).

NIST:
In no instance did NIST report that steel in the WTC towers melted due to the fires. The melting point of steel is about 1,500 degrees Celsius (2,800 degrees Fahrenheit). Normal building fires and hydrocarbon (e.g., jet fuel) fires generate temperatures up to about 1,100 degrees Celsius (2,000 degrees Fahrenheit). NIST reported maximum upper layer air temperatures of about 1,000 degrees Celsius (1,800 degrees Fahrenheit) in the WTC towers (for example, see NCSTAR 1, Figure 6-36).
However, when bare steel reaches temperatures of 1,000 degrees Celsius, it softens and its strength reduces to roughly 10 percent [***NOTE: no reference] of its room temperature value. Steel that is unprotected (e.g., if the fireproofing is dislodged) can reach the air temperature within the time period that the fires burned within the towers. Thus, yielding and buckling of the steel members (floor trusses, beams, and both core and exterior columns) with missing fireproofing were expected under the fire intensity and duration determined by NIST for the WTC towers.

Modulus of Elasticity for Steel:
http://www.engineeringtoolbox.com/young-modulus-d_773.html

What is concerning is that thermite was rule out because of the noise, and that 1000 lbs would be needed.

Also, no one has explained the UL testing on the steel for 6 hrs at 1000C?

Finally, what is troubling is that softening girders causeing collapse, fine, steel is weakened at 1400degF, but the core wouldn't fall. Certainly wouldn't break apart.

>> ^jimnms:

>> ^Janus:
Robbersdog49 already pointed out the 58°F temperature difference between the melting point of ice (32°F) and the temperature of your hand (90°F).
To put it another way, when the temperature outside is just a few degrees above 32°F and there is ice or snow out, have you noticed how very long it takes to melt?

Milk chocolate has a melting point about the same as gallium (around 85°F). Because of the close melting point to my skin I shouldn't get chocolate on my fingers when I eat a candy bar, but I do.


Gallium also conducts heat more effectively than milk chocolate so the heat from your hand isn't concentrated in the surface of the metal.

>> ^jimnms:

Milk chocolate has a melting point about the same as gallium (around 85°F). Because of the close melting point to my skin I shouldn't get chocolate on my fingers when I eat a candy bar, but I do.


That would be milk chocolate which has been at room temperature, and thus was close to melting point to begin with?
OK then, have you stored milk chocolate in the freezer and then taken it out and held it? It doesn't melt very quickly and doesn't leave residue on your hand from brief contact, does it? But eventually, yes, it will melt in your hot hand. The same as the gallium spoon would if he'd had it in his hand long enough.

>> ^Janus:

Robbersdog49 already pointed out the 58°F temperature difference between the melting point of ice (32°F) and the temperature of your hand (90°F).
To put it another way, when the temperature outside is just a few degrees above 32°F and there is ice or snow out, have you noticed how very long it takes to melt?


Milk chocolate has a melting point about the same as gallium (around 85°F). Because of the close melting point to my skin I shouldn't get chocolate on my fingers when I eat a candy bar, but I do.