You can turn steel to dust with a file or abrasive stone, although it would take a long time. But there's no physical mechanism of turning steel to dust with an energy beam. All you can do is heat it up.
Steel is not like concrete. You could perhaps imagine some kind of very strong energy beam shaking concrete until it fractured and turned to dust. But steel does not fracture when you shake it, it's very plastic.
It's basically magic. There's no known technology that would do that without basically melting the beams.
And it's all moot anyway, as the steel did not turn to dust, there's zero evidence of that.