I am going to take some 1/2" and 3/4" cold rolled rod, and basically make it
up into a catcher's mask configuration, just bigger. Squares about 2-3"
square. I am going to weld it together , then hard face it.

This will certainly change the properties all around. It is going to be
used in 40-50 degree F water, and be subject to right around 1,000# of
striking force, and 4,000 pulses per second. It could be subject to below
freezing temperatures, too, but not used at that time.

What can anyone tell me? Which rod would be the best for joining the rolled
bars? I have some hard face rod that a friend of mine who sells mining
supplies got for me that is supposed to be the best choice for the
conditions described. If I buy some 1/2" flat bar to use in this
fabrication, I probably will be able to cut it with my chop saw without too
much HAZ. But, then when I weld it together, there will be substantial HAZ.

What would be the best heat treatment? Anything to do particularly right
after welding? Let it cool on the bench? Quench? Throw in an oven at a
high temp, and slowly cool? I want to keep from cracking mainly.

These will probably be throw away items, that is, when they either break, or
wear through, they would be replaced with new rather than fixed by
replacement of bars, since the bars would be hard to cut out, and put new
short sections in.

Help appreciated.

I'm getting the first prototypes of the gold dredge head ready.

Steve