What might prevent metal “blowing” and other forms of shaping from working if gravity was not a factor? Let’s handwave-ignore the extremes of temperature as it relates to techniques and the present primitive space habitats and craft.
Is it possible to suspend a pool of molten metal, with a tube inside, spin while adding a gas to shape a container, and form more complex shapes through additional heat cycles in a repeatable process?
Melting point doesn’t work like boiling point. Otherwise, what would we make rockets out of? They get really hot in a vacuum, but need to (and do) stay solid.
If you go to really high pressures like in an ocean trench or deeper, melting points will raise too (or lower, in water or silicon’s case), but 1 vs. 0 atmospheres is negligible. I haven’t seen it even mentioned in any vacuum engineering stuff.
While it’s true that the relationship between melting point and boiling point differ from material to material, the melting point always remains below the boiling point until the triple point.
The triple point is when the ambient pressure is low enough that a substance can be solid, liquid, and vapor in equilibrium at the same time.
As for engines, they burn at temperatures hot enough to melt the steel they are made of, even while on Earth. Engineers employ regenerative cooling to prevent the housing from melting at such high temperatures.
They still get very hot, though.
Another example: Every incandescent lighbulb. The filament is stupid hot in there, under a rough vacuum, and doesn’t melt. I would be surprised if 1 bar even amounted to a full degree of change in melting/freezing point.
Water is volatile, and so it’s a better example of variability at familiar scales. You’ll notice the freezing point is pretty much vertical at 0C on the phase chart until 100s of bars. (And then gets lower because pressure pushes matter towards denser states, and ice I is, unusually, less dense than the liquid)
The triple point shows up when the boiling point lowers to meet the melting point, and liquid water ceases to exist as a stable substance. It’s at ~0C.