Take Time For Hardening
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HARDENING CARBON STEEL FOR TOOLS
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The Working Of Steel
Uneven heating and poor quenching has
caused loss of many very valuable dies, and it certainly seems
that when a firm spends from $75 to $450 in cutting a die that
a few hours could be spared for proper hardening. But the usual
feeling is that a tool must be hurried as soon as the hardener
gets it, and if a burst die is the result from either uneven or
overheated steel and quenching same without judgment, the steel
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gets the blame.
Give the steel a chance to heat properly, mix a little common sense
with your 30 years experience on the other fellows steel. Remember
that high-carbon steel hardens at a lower heat than low-carbon
steel, and quench when at the right heat in the two above ways,
and 99 per cent of the trouble will vanish.
When a die flies to pieces in quenching, don't rush to the
superintendent with a poor-steel story, but find out first why it
broke so that the salesman who sold it will not be able to harden
piece after piece from the same bar satisfactorily. If you find
a cold short, commonly called a pipe, you can lay the blame
on the steelmaker. If it is a case of overheating and quenching
when too hot, you will find a coarse grain with many bright spots
like crystals to the hardening depth. If uneven heating is the
cause, you will find a wider margin of hardening depth on one side
than on the other, or find the coarse grain from over-heating on
one side while on the other you will find a close grain, which
may be just right. If you find any other faults than a pipe,
or are not able to harden deep enough, then take the blame like
a man and send for information. The different steel salesmen are
good fellows and most of them know a thing or two about their own
business.
For much work a cooling bath at from 50 to 75 deg.F. is very good both
for small hobs, dies, cutter plates or plungers. Some work will
harden best in a barrel of brine, but in running cold water, splendid
results will be obtained. Cutter plates should always be dipped
corner first and if any have stripper holes, they should first
be plugged with asbestos or fire clay cement.
In general it may be said that the best hardening temperature for
carbon steel is the lowest temperature at which it will harden
properly.