Question:
I'm going to stress relieve a bar of C1018 that has been well machined,
releasing considerable stress and causing the expected warpage, which has
been corrected by bending. After stress relieving the bar, I'll do the
finish machining. The bar will be a holding fixture for sharpening knives
for a power planer. I'd like to avoid scaling the bar excessively. I don't
have a controlled atmosphere furnace, nor do I have any stainless foil on
hand. Can any of you suggest a method to protect the steel from excessive
scaling? Barring anything else, I could drizzle argon into the furnace, but
that's no guarantee it will not scale., and the prolonged cycle could prove
quite costly gas-wise. How about it, heat treat experts?
Answer:
I seem to recall that coating the workpiece with sodium silicate will
prevent scaling. Sodium silicate or waterglass, is a liquid that could be
brushed on, and what remains after HT should be water soluble.
I'm no expert but I've heard to rub soap on the outside of cooking
utensils when cooking over an open fire for easy cleanup.
If it's small, a thin layer of borax (applied as a mush perhaps? Or have
you any paste flux?) might hold it long enough. Dunno about removing later,
could get pretty crunchy...
Only needs what, 1000°F or so? For an hour? Could take that off with
sandpaper later...
This is probably acedemic at this point, but if the base material was
cold rolled steel, this is really really common problem with that
stuff. If you have the opportunity or need to make more units, you
would be much happier with hot rolled steel, which will not give you
nearly any of the same problems: You probably will not need to bend
back to flat or stress relieve.
We used to use the hot rolled steel for punch plates and retainers for
high precision stamping. Occasionally, someone would spec out CRS
instead of HRS and man what a mess.
Sorry I can't really answer your real question, but using hot-rolled
material is so much better as it has a much lower internal stress
because it is hot worked.
