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Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work. |
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#1
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Aging cast iron = Old wife's tale?
It is baffling to me why most people here are saying day temperature has little effect on the metal. I was once told and also read that well ground gauge blocks can unite completely if left over night. This tells me that there is motion of atoms even at day temperature state of energy. I am only a toolmaker so I can't state with authority that curing of cast is important or not however I feel dismissing it based on laboratory tests conducted on limited time is fatal.
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#3
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Aging cast iron = Old wife's tale?
On 11/26/2017 2:14 PM, Gunner Asch wrote:
On Sun, 26 Nov 2017 13:24:43 -0800 (PST), wrote: It is baffling to me why most people here are saying day temperature has little effect on the metal. I was once told and also read that well ground gauge blocks can unite completely if left over night. This tells me that there is motion of atoms even at day temperature state of energy. I am only a toolmaker so I can't state with authority that curing of cast is important or not however I feel dismissing it based on laboratory tests conducted on limited time is fatal. Oh its quite true and I agree You wouldn't know, dole scrounger. |
#4
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Aging cast iron = Old wife's tale?
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#5
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Aging cast iron = Old wife's tale?
On 26-Nov-17 7:15 PM, Ed Huntress wrote:
.... It isn't clear what you're referring to here, but gray cast iron does stress-relieve over time. Pratt& Whitney Machine Tool used to leave their castings out in the yard for six months before machining them. That was common practice before people figured out the cost of "work in process" (WIP). .... Back 50 year ago now, nearly, bought a Powermatic Model 66 TS and arranged for direct pickup from factory in McMinnville, TN. Talked them into tour while there; they had mounds of raw castings pile all over the yard 20-ft high; they used 18-months for jointer tables and the like; a year for the TS tables. Now, it's an abandoned lot... -- |
#6
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Aging cast iron = Old wife's tale?
On Mon, 27 Nov 2017 01:29:52 -0600, dpb wrote:
On 26-Nov-17 7:15 PM, Ed Huntress wrote: ... It isn't clear what you're referring to here, but gray cast iron does stress-relieve over time. Pratt& Whitney Machine Tool used to leave their castings out in the yard for six months before machining them. That was common practice before people figured out the cost of "work in process" (WIP). ... Back 50 year ago now, nearly, bought a Powermatic Model 66 TS and arranged for direct pickup from factory in McMinnville, TN. Talked them into tour while there; they had mounds of raw castings pile all over the yard 20-ft high; they used 18-months for jointer tables and the like; a year for the TS tables. Now, it's an abandoned lot... Wow, a year and a half. That's a long time to tie up your working capital and pay or lose interest on it. But, as I said, it once was common practice, and it worked. Not to belabor this, but the OP actually was asking about two different things. The stresses in castings are the result of different rates of cooling in thin versus thick sections. Stresses build as the metal contracts upon cooling. Over time, or with heat or vibration, the metal grains will slip across each other to relieve the stresses. The gage block (yes, the spelling of "gage" is intenional) issue is different. That's about growth in the metal that results from a phase change -- from austenite to martensite, in this case. And that's the result of incomplete conversion to the harder martensite when you heat-and-quench. -- Ed Huntress |
#7
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Aging cast iron = Old wife's tale?
"Ed Huntress" wrote in message
... Not to belabor this, but the OP actually was asking about two different things. The stresses in castings are the result of different rates of cooling in thin versus thick sections. Stresses build as the metal contracts upon cooling. Over time, or with heat or vibration, the metal grains will slip across each other to relieve the stresses. Ed Huntress Do steel welds slowly stress-relieve? -jsw |
#8
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Aging cast iron = Old wife's tale?
On Mon, 27 Nov 2017 12:45:07 -0500, "Jim Wilkins"
wrote: "Ed Huntress" wrote in message .. . Not to belabor this, but the OP actually was asking about two different things. The stresses in castings are the result of different rates of cooling in thin versus thick sections. Stresses build as the metal contracts upon cooling. Over time, or with heat or vibration, the metal grains will slip across each other to relieve the stresses. Ed Huntress Do steel welds slowly stress-relieve? -jsw I think so, but I'd have to check to be sure. BTW, vibratory stress relief, as a commercial operation, was developed in Germany to stress-relieve the welds on their big steel weldments, including those on machine tools. -- Ed Huntress |
#9
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Aging cast iron = Old wife's tale?
On 27-Nov-17 10:11 AM, Ed Huntress wrote:
On Mon, 27 Nov 2017 01:29:52 -0600, wrote: .... Back 50 year ago now, nearly, bought a Powermatic Model 66 TS and arranged for direct pickup from factory in McMinnville, TN. Talked them into tour while there; they had mounds of raw castings pile all over the yard 20-ft high; they used 18-months for jointer tables and the like; a year for the TS tables. Now, it's an abandoned lot... Wow, a year and a half. That's a long time to tie up your working capital and pay or lose interest on it. But, as I said, it once was common practice, and it worked. The old mill foreman that took me around explained they had come to the various time periods from long observation of results for various aging periods. The jointer tables were the most problematic being so varied in thickness from the gibs area to the long tapered bed tails. The Model 60 8" tables were each 24" long so they had the longest cure. Made sense but was surprising on first blush to see the piles of rusty castings scattered all over the lot... Not to belabor this, but the OP actually was asking about two different things. The stresses in castings are the result of different rates of cooling in thin versus thick sections. Stresses build as the metal contracts upon cooling. Over time, or with heat or vibration, the metal grains will slip across each other to relieve the stresses. The gage block (yes, the spelling of "gage" is intenional) issue is different. That's about growth in the metal that results from a phase change -- from austenite to martensite, in this case. And that's the result of incomplete conversion to the harder martensite when you heat-and-quench. Yes, I understood the difference... -- |
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