Will these sear at lower temps, say 425?

They should, but it may not be as deep.  I just grilled two 1 1/2" ribeyes at 450 and it seared them good. 

Grate!
Thank you

Grill grates sear really nice using the flat side.  Try it both ways as long as you have 2+ steaks.  The center will be the hottest since it's where the flame comes out, at least my Yoder is like that.

When using the flat side for steaks is it just to sear or the whole cook?

If you just want something for searing you can also use a cast iron griddle. I use one in my Weber gasser at around 450. Takes longer to heat up that GrillGrates but has more heat capacity.

When using the flat side for steaks is it just to sear or the whole cook?

On my yoder, the steaks are to the far right side to come to temp, maybe 110 or so, then move the steaks for the sear to the fire side.

A sear is just a minute per side or so, it's fast.