3 ms·

> and its high reactivity with the atmosphere when hot Isn't that a problem for everything? That's the nature of heat.

kergonath 1y ago
That’s a matter of degree. Iron gets reactive and form some oxide at high temperature. This can be worked around by controlling the atmosphere or adding reducing elements or oxygen traps. Other metals like magnesium just burn, which is much harder to work around. You need to go much higher in temperature than the usual manufacturing conditions to make iron burn in a normal atmosphere.
SubjectToChange 1y ago
Molten iron can be poured in open air. Doing that with titanium will yield a distinctly different results.
adrian_b 1y ago
For metals with high electronegativity, like iron and copper, high temperatures do not necessarily create problems due to greater reactivity than at low temperatures. On the contrary, the oxides of such metals may decompose at high enough temperatures. Moreover, when such metals are mixed with more reactive metals, at high temperatures those will combine preferentially with non-metals like oxygen and sulfur, removing them from the metal of interest. For metals with high affinity to oxygen, like titanium, aluminum or magnesium, no temperatures attainable during normal processing are high enough to decompose their oxides, but the high temperatures increase by several orders of magnitude the speed of reaction with the air, in comparison with room temperature, where the speed of oxidation of titanium and aluminum becomes negligible immediately after the formation of a protective oxide layer. Moreover, for such metals it may be more difficult to find even more reactive metals than them, which will extract oxygen from their oxides while not having other undesirable properties, like yttrium was found for titanium in the parent article. Yttrium is a metal with a reactivity not so great as calcium, but greater than magnesium, so also greater than titanium and aluminum. Neither calcium nor magnesium are suitable for removing oxygen from titanium, for various reasons, e.g. low boiling or melting temperatures, so yttrium is likely to create much less problems. So the effects of heat are not always the same.

That’s a matter of degree. Iron gets reactive and form some oxide at high temperature. This can be worked around by controlling the atmosphere or adding reducing elements or oxygen traps. Other metals like magnesium just burn, which is much harder to work around. You need to go much higher in temperature than the usual manufacturing conditions to make iron burn in a normal atmosphere.

SubjectToChange 1y ago

Molten iron can be poured in open air. Doing that with titanium will yield a distinctly different results.

adrian_b 1y ago

For metals with high electronegativity, like iron and copper, high temperatures do not necessarily create problems due to greater reactivity than at low temperatures. On the contrary, the oxides of such metals may decompose at high enough temperatures. Moreover, when such metals are mixed with more reactive metals, at high temperatures those will combine preferentially with non-metals like oxygen and sulfur, removing them from the metal of interest. For metals with high affinity to oxygen, like titanium, aluminum or magnesium, no temperatures attainable during normal processing are high enough to decompose their oxides, but the high temperatures increase by several orders of magnitude the speed of reaction with the air, in comparison with room temperature, where the speed of oxidation of titanium and aluminum becomes negligible immediately after the formation of a protective oxide layer. Moreover, for such metals it may be more difficult to find even more reactive metals than them, which will extract oxygen from their oxides while not having other undesirable properties, like yttrium was found for titanium in the parent article. Yttrium is a metal with a reactivity not so great as calcium, but greater than magnesium, so also greater than titanium and aluminum. Neither calcium nor magnesium are suitable for removing oxygen from titanium, for various reasons, e.g. low boiling or melting temperatures, so yttrium is likely to create much less problems. So the effects of heat are not always the same.