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Thread: Thiers Issard grades
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11-01-2006, 12:14 AM #1
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Thanked: 995Originally Posted by JLStorm
The most likely use, is to austenitize the steel, put all the carbon into solution and quench from that temperature. A molten bath, whether lead or high temperature salts (my choice, dangerous but not from nasty fumes) will be very easy to control temperature wise and reduce the risk of grain growth and other problems occuring when the austenitizing temperature is overshot. Frankly, the steel doesn't really care which method, of them all, is used.
The real purpose of both the graphite and lead (and so will molten salt baths) is to prevent oxidation at that temperature (scale formation). This is very desirable for production because the blade can be nearly completely polished and subsequently heat treated without any further grinding to clean up the steel.
The problems in production are the lead fumes that will cause nervous system issues. So the Euro equivalent of OSHA comes in to play. The steel, if finished sufficiently well, will not pick up any lead in quantity and unless someone is daring enough to routinely lick their blades, doubtful that enough will be ingested to make any difference. We're all nuts enough using straight razors to shave with eh?
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11-01-2006, 01:58 AM #2
Thanks Mike. That was useful.
So why do you think is it that they choose to use lead? Cheaper? Easier?
X
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11-01-2006, 02:13 AM #3
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Thanked: 995I suspect historically that it was both. Lead was a pretty well known compound since the Roman era, very easy to work and work with. The plus side, they had no idea of its health hazards as we do now. As a metal it's pretty sturdy, easy to shape, easy to cast with it's low melting temperature.
Whoever figured out that a piece of steel could be heat treated with little or no scale was an observant fellow indeed. Made for very consistent heat treatment. Hence the TI reputation. It would be really interesting from a history standpoint to know when molten lead became a part of the heat treatment industry.
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11-01-2006, 06:29 PM #4Originally Posted by xman
"LEAD HARDENING IS THE ABSOLUTE BEST METHOD FOR THE HARDENING OF RAZORS AS THE STEEL IS HEATED ABRUPTLY (WHEN PLUNGED INTO THE BOILING LEAD) RIGHT TO THE CORRECT TEMPERATURE! THUS GUARANTEEING THE MOST PERFECT PROPER HEAT TREATMENT."
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11-01-2006, 06:35 PM #5
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Thanked: 995The lead bath is a very good method of heat treatment, meaning hardening of the steel. They have to quench the blade in something after heating it to "set" the martensite formation at the edge at least. It'd be nice to know what they use for quenching medium. Oil would be good and likely a standard quenchant for most good razor steels. Water is very quick and would risk a large number of cracks/blade failures at those very thin dimensions. But they could also use a bath that was capable of about 400 F and go right into quenching and tempering at the same time.
The comment about annealing at 300 C is strange to me. That's about 572 F and would likely draw the hardness of the steel down to a lower Rockwell number. It'd make the blades easier to hone for sure. I'd like more info about that particular aspect.
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11-01-2006, 03:10 AM #6Originally Posted by Mike Blue
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11-01-2006, 03:15 AM #7
Joe,
Those numbers would be inline with hardening and annealing good steel and similar to what Mike has stated.
TonyThe Heirloom Razor Strop Company / The Well Shaved Gentleman
https://heirloomrazorstrop.com/
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11-01-2006, 02:05 PM #8
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Thanked: 995I'm going along with the info you guys are telling me. It's interesting to "look into" their processes though. Are there TI references for me to look at? It might not be all that interesting to the list here, but little tidbits might pop into my head.
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11-01-2006, 06:24 PM #9Originally Posted by Tony Miller