So like many on the SH forum I started salt bath annealing using a kit from Ballistic Recreations. It has worked well so far except that I only ordered one container of his salt mixture and now I don't have enough to fill the pot to the desired level.
So in search of replacement salts I read some of the threads on this forum and most people reported using a mixture of Sodium Nitrate and Potassium Nitrate which I ordered from Duda Energy. After my order arrived I looked more closely at the little container from BR and Gary actually uses Sodium Nitrite and Potassium Nitrate.
Now I don't remember much from high school chemistry so I started looking on the web. BR says the mixture attempts to match MIL-Std-10699 Type 1. I found the MIL-Std-10699 doc on everyspec.com and sure enough Class 1 uses a mixture of Sodium Nitrite, Potassium Nitrate and (optionally) Sodium Nitrate. It lists a working temperature of 163-593 degrees Celsius. The mixture for Class 2 has a working temperature of 288-593 degrees Celsius and is a 50/50 mixture of Sodium Nitrate and Potassium Nitrate.
My question to anyone who is more knowledgeable than I is: does it matter, Class 1 or 2? If the BR salts I've been using are Class 1, is it ok now to add Class 2 mixture of NaNO3 and KNO3? Seems like the main difference is the lower end working temperature. I monitor my salt temperature and keep it well below 550 degrees C as BR recommends.
BTW, MIL-Std-10699 actually has a very stern warning in Sec 6.3 about the use of Nitrate salt baths. The warning cautions against overheating above 593 degrees C and against the accidental immersion of any aluminum alloys as an explosion hazard. Worth a read.
Would like to hear what someone who is more of an expert has to say.
So in search of replacement salts I read some of the threads on this forum and most people reported using a mixture of Sodium Nitrate and Potassium Nitrate which I ordered from Duda Energy. After my order arrived I looked more closely at the little container from BR and Gary actually uses Sodium Nitrite and Potassium Nitrate.
Now I don't remember much from high school chemistry so I started looking on the web. BR says the mixture attempts to match MIL-Std-10699 Type 1. I found the MIL-Std-10699 doc on everyspec.com and sure enough Class 1 uses a mixture of Sodium Nitrite, Potassium Nitrate and (optionally) Sodium Nitrate. It lists a working temperature of 163-593 degrees Celsius. The mixture for Class 2 has a working temperature of 288-593 degrees Celsius and is a 50/50 mixture of Sodium Nitrate and Potassium Nitrate.
My question to anyone who is more knowledgeable than I is: does it matter, Class 1 or 2? If the BR salts I've been using are Class 1, is it ok now to add Class 2 mixture of NaNO3 and KNO3? Seems like the main difference is the lower end working temperature. I monitor my salt temperature and keep it well below 550 degrees C as BR recommends.
BTW, MIL-Std-10699 actually has a very stern warning in Sec 6.3 about the use of Nitrate salt baths. The warning cautions against overheating above 593 degrees C and against the accidental immersion of any aluminum alloys as an explosion hazard. Worth a read.
Would like to hear what someone who is more of an expert has to say.
