So many terms used in metallurgy, and it's fairly complicated so I'll try to phrase my question/info I'm seeking in a way that makes sense...
I weld (MIG) a lot of bolt bodies for the Mosin-Nagant. Dozens per week.
Unlike the Mauser, the MN does not have an integral bolthead- so the concern about heat transfer affecting temper of the bolthead lugs doesn't exist.
However, there may (or may not) be an issue of "wear resistance", as relates to the cocking cam at the rear, and front notched section of the bolt body that engages the bolthead to rotate it into, and out of, battery.
This is not an issue of "strength", or "hardness", or "brittleness", in my non-expert opinion, because there is very little in the way of external forces applied to these parts.
I use a simple, aluminum heatsink that I insert into the bolt body "just because", but to the point of my question: I have been unable to find with my "Google-fu", the temperature at which steel becomes "softened" (don't know if that is the correct technical term) and it's wear resistance is affected.
I've done over 1,000 of these, have had two weld failures (two too many- but they were at the beginning), and never an issue related to wear brought to my attention by a customer.
But as my Daddy said long ago- anything worth doing, is worth doing "right"- so I'd like to know what this critical temperature is. It will be simple enough for me to check both ends of the bolt body after welding with my IR thermometer to see what I've got. The MIG process goes very quickly and the steel never gets red hot, so I'm probably overthinking this, just want to be sure I'm turning out the best product possible.
Edit to add: Bolts are allowed to slowly air-cool. No quenching with oil/water, wet rags, etc...
I weld (MIG) a lot of bolt bodies for the Mosin-Nagant. Dozens per week.
Unlike the Mauser, the MN does not have an integral bolthead- so the concern about heat transfer affecting temper of the bolthead lugs doesn't exist.
However, there may (or may not) be an issue of "wear resistance", as relates to the cocking cam at the rear, and front notched section of the bolt body that engages the bolthead to rotate it into, and out of, battery.
This is not an issue of "strength", or "hardness", or "brittleness", in my non-expert opinion, because there is very little in the way of external forces applied to these parts.
I use a simple, aluminum heatsink that I insert into the bolt body "just because", but to the point of my question: I have been unable to find with my "Google-fu", the temperature at which steel becomes "softened" (don't know if that is the correct technical term) and it's wear resistance is affected.
I've done over 1,000 of these, have had two weld failures (two too many- but they were at the beginning), and never an issue related to wear brought to my attention by a customer.
But as my Daddy said long ago- anything worth doing, is worth doing "right"- so I'd like to know what this critical temperature is. It will be simple enough for me to check both ends of the bolt body after welding with my IR thermometer to see what I've got. The MIG process goes very quickly and the steel never gets red hot, so I'm probably overthinking this, just want to be sure I'm turning out the best product possible.
Edit to add: Bolts are allowed to slowly air-cool. No quenching with oil/water, wet rags, etc...