How fast is a sword swing that causes the blade to become red hot

[Sonoftanavast9]

Basically exactly what the title says

How fast do you need to swing a blade to cause it to glow red hot.

Basically in a novel I'm reading a character with enhanced speed swings their sword through another person's sword fast enough to leave the halves of the other person's sword red hot - How fast do they need to be to do this

 

[Sonoftanavast9]

Bump

 

[Arkenis]

Pretty sure calcs are done for clothes catching fire and that's mach 5. You're probably looking at anything transonic to supersonic I'd assume just off the difference in material and surface area. Here's the calc for clothes though

 

[CloverDragon03]

There's no real calc for that feat, it's just taken from a NASA page. But given that igniting your body (1500 degrees Celsius) requires speeds of 6000 km/h and igniting your clothes (500 degrees Celsius) requires speeds of 2500 km/h, we can at least say that it'd require more speed than 2500 km/h since steel has a higher ignition point (704 to 760 degrees Celsius)

So, somewhere between Mach 2.02 and Mach 5, but I can't give any specifics beyond that