Subject: Re: Steel Problem

From: [email-masked] (Katana ---/-----------)
Date: Fri, 13 Sep 1996 13:48:17 GMT

I don't know if this opinion is qualified or not, but, It is possible that
the stress cracks were mirco-crystaline in there to begin with, and with
use got worse. What happened when you heated it is you RELEIVED the stress,
thus causing the cracks to widen and appear. I've had this happen on old
leaf spring (5160) especially on larger pieces (over 1/4" thick). I don't
think a gas forge could heat fast enough to cause thermal fractuing. That
would take a coal forge and Mongo on the crank. 
 
>> I was asked to repair the ends of a few crow bars. 
>> I was sucessful in all but one.   A double ended bar.  These are all
about 
>> 5feet in length and about 1 1/2inch thick.   The one bar developed a
crack  
>at 
>> each end on heating, before any work was done.    I did heat all them in
a 
>> comercial gas forge. 
>> Any Ideas?? 
>You heated too fast? Thermal stresses could have cracked the bar before 
>it had a chance to anneal. Any more qualified opinions on this? 
> 
>Ralph Snel 
>[email-masked] 
-- 
               Bill Wyant 
   Bladesmith / Art Blacksmith 
Avalon Ironworks, Ft. Wayne, IN 
    [email-masked]

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From: Tom Vincent <[email-masked]>
Date: Sun, 15 Sep 1996 17:36:36 -0500 (CDT)

I always take care in a few places, some already mentioned. 1) The use to 
which the tool was put before it broke sometimes creates fractures you 
can do nothing about, already discussed during threads regarding the use 
of old springs; 2) not only heating too fast, but too hot, 3) getting 
impatient and striking those few extra blows at the end of each heat when 
the metal has gotten too cold, 4) wrong quenching/hardening temperature 
and solution. Many of these fall into the category, in my shop, of too 
many irons in the fire at the end of a long day. Many, however are 
related to the differences in alloys not only from one tool company to 
the next, but over the years, the same tool company may move to a 
different (cheaper?) alloy. I always treat an unknown tool steel as if it 
were H-13, narrow forging temperatures, air cool. If that doesn't work, 
widen the ranges until I get close. Tom