No apology necessary Miller, thank you though sir.....like the Bible passages we all interpret words differently and I am sure I misread your postings.....?.........I took it as a personal attack (which appears all to common on this BBS) connected to Nitro's smart remarks.....probably my error......and my apology is probably more in order than yours.....so you have it.....
If you take a piece of low carbon steel (at or less than .03wt%C) and pack it in a rich solid carbon atmosphere of your choice and heat for a few hours you will easily attain a carbon depth hardness of about 1 mm.......so from there you, Miller, can work out what is necessary for a slight increase in dept.....
I think the original factories ran CCH at higher temperatures than most of us re-case today, key word here is re-case, therefore the original carbon depth already exists at about 1.2 mm or a little more IMO......I personally do not lower my temps prior to quench and find a lowering of temperature would be detremental to the whole process.....also detremental and key is to lower the crucible and drop the parts into the quench at the shortest possible drop height as the 02 rich atmosphere directly impacts carbon and colors........this is also another reason that I do not lower the temperature prior to quench......and have built special crucibles with an emphisis on this step..........the more 02 in the quench water the better.........
If time, temperatures and various mixtures of solid carbon rich additives are all monitered carefully, some very vibrant colors and uniform hardness can be achieved.....since most of us do not have extreme annealing times, most of the original carbon has not been removed IMO....of course, should you anneal for far too long, then most of the carbon would out gas as a result.....
Most of us keep records and know all our times, mixtures, temperatures and various patterns which satisfy the end result.........various experiments are tried to achieve different colors, but remember, each alloy of steel is different from manufacturer to manufacturer , what works for one, may not work for another....(records, records and more records)...and these alloys also can change from year to year even with the same manufacturer, CCH has and always will be like a snowflake....no two are alike............. this is truly the beauty and fasination of CCH for me........
Consistency on the hardness issue must be and is very consistent on re-cased items in my opinion.....some people I know heat small parts and quench these in a carbon rich medium, like various cyanide compounds........I personally do not like that process or the colors it achieves......I firmly believe in bone/charcoal and some secret sauces.....unless originally cased using the cyanide process, like Sterlingworths after 1912 or so, Savage, Sears, later Ithaca's etc....the cyanide process uses a lower temperature and the carbon layer will seldom exceed 1 mm and is not as uniform as the bone/charcoal hardness.........IMO........
I don't publish my times, temps and propriatary information that took me over 20 years to tweak, sorry, but I hope this helps in what you are looking for.....
Best,
