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Post by Dan Davis on Nov 7, 2009 2:35:17 GMT
Guys, I appreciate the comments. I am glad I was understandable and no one took offense. Avery, I could not agree more. As I have already said in other posts, that's why I hang my hat here. Tom, A2 and D2 are high-chromium alloys, both having approximately 11% chromium content; as opposed to the 13% or better needed in order to be classified as a "stainless alloy". Still, better than 1/10th of the material is chromium and that is a VERY high alloying value. Both A2 and D2 are toolmaking steels, specifically designed for making punches and dies that retain high hardness under high temperature and stress conditions. They were NOT designed for use as blade steels; While it is true that these steels were specifically designed for high cyclic stress applications they were not intended for use as springs, which is primarily what a sword-length blade is. In my opinion A2 and D2 should be treated the same as full-on stainless alloys and blades longer than 11-12 inches should be considered unsafe. Some smiths and production companies will disagree with me, but I would suspect that that disgreement was motivated by market share and advertising gimmicks based on use of those tool steels. On the other hand both A2 and D2 make super-spiffy war hammers, maces and battle axes  |
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Post by Tom K. (ianflaer) on Nov 7, 2009 6:01:37 GMT
thanks Dan that's good to know. The sword I had made of D2 was uber thick and stiff so I wonder if it is really ok since it seems to not act spring-like but it's hard to see what is really going on in a sword at full-speed.
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Post by Dan Davis on Nov 7, 2009 13:00:56 GMT
Yes, well it is very hard to tell; the major issue with ChrDSC is that it is a sudden, catastrophic failure without warning so you never know when it may let go.
The actual mechanism of ChrDSC is based on temperature differential. In blades this is mostly caused by deflection and compression when a blade flexes and also by impact, so repeated cuts increases the likelyhood of failure.
But, since temperature is temperature no matter what the source you can promote chromium migration in steels just by leaving your blade lying around in the sun.
Again, it is really hard to tell when this failure will happen and that is the main reason to just not use that steel for swords.
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Post by Deleted on Nov 7, 2009 14:03:08 GMT
Thanks, Dan. Very useful stuff to know.
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Post by Matt993f.o.d on Nov 7, 2009 14:09:25 GMT
So there you have it. Keep your stainless blades in the freezer! ;D lol
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Post by brotherbanzai on Nov 7, 2009 18:11:18 GMT
No, I wouldn't say that, because they aren't comparable statements. An important difference between 440A and 440C is that 440A can be fine blanked (stamped out of a sheet) but 440C can't as it would wear out the dies to quickly. Fine blanking knife and sword shapes is cheaper than laser cutting, which is why low end blades are often made from 440A rather than 440C. If a manufacturer spent the money to use 440C, there is at least a possibility that they also used optimal heat treating procedures. If the manufacturer is trying to make blades as cheaply as possible and thus opted for 440A, there is a pretty good chance that the heat treatment was also less than ideal. So if your cheap wall hanger is made of 440C, there is a chance that it is a well made blade. If your cheap wall hanger is made from 440A, it's probably useless.
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Post by Dan Davis on Nov 8, 2009 1:13:42 GMT
Again, BB, I am not sure where this information is coming from. What is your source for this? I know of several cutlery companies that stamp blades from 440C, including Schrade, Old Timer, and Buck. - Carbon content in ANY steel alloy has little to no affect on stamping operations or die wear when the alloy is in an annealled state.
- The primary issue with steels in an annealed state is alloying elements like vanadium or chromium that are wear-resistant in all molecular states.
440A, 440B, or 440C all have essentially the same alloy composition except for the carbon content and all of them are essentially identical when it comes to stamping operations. |
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Post by brotherbanzai on Nov 10, 2009 17:07:54 GMT
I thought Old Timer was a line manufactured by Schrade rather than a separate company? I'm not up on my knife maker trivia though. I'd ask them but it seems that Schrade has gone bankrupt.
Buck hasn't used 440c since the early '80's. The reason they switched from 440c to 420hc? Because the 440c didn't work well with their fine blanking machinery.
My source DD? I called Buck and asked them. 1-800-326-2825. Call them yourself if you don't believe me. Though I suppose it's possible the fellow I talked to was misinformed too.
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Post by Dan Davis on Nov 10, 2009 21:21:45 GMT
OT was a separate line, then part of Schrade, then a separate line again, so "all of the above". Remember, when it comes to "old timers" I am one I never said I didn't believe you, I was asking where the info came from. I'm not trying to start arguments either, just trying to have (as sparky said) "a civil stainless discussion". If I came across as anything else I apologize.I've been working off and on with the engineering staff (all three of them) of a die stamping factory for the last 5 years or so. One of the projects we researched extensively was deep-draw stamping of the 440 alloys, and my statements are based on that research. About the info from Buck: 420hc and 440A/B/C are fundamentally different; if they were having problems with 440C then they likely couldn't use 440A or B either. I'll run it past Tom and Bob and see what they say. |
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