brine

[HWooldridge]

Originally Posted by irnsrgn

Many, Many years ago an old timer who was known for his hardening and tempering ability, told me that difference between water and brine was the size of the bubbles formed from the steam the hot piece makes when immersed in the solution. Some of the tool makers I know use a 1/4 inch of vegetable oil floating on top of the brine to take the shock off the item. It also has a tendency to remove the water from the item as it comes out of the quench.

Robb Gunter's lye-based Super Quench formula yields similar results but is somewhat dangerous to use. I was quenching tools in a batch several years ago and wound up burning my lungs with the vapor. I now use his revised recipe which is basically salt, Dawn and water (although I can't remember the proportions off the top of my head).

I was also told that brine forms a smaller steam pocket than plain water.

One thing to remember is to balance the steel type with the proper quench. Plain water hardening steels will get hard as a banker's heart in a brine quench because the austenite is turned to martensite so quickly. In fact, garden variety A36 will often get in the Rockwell 40 range in brine. However, typical air hardening steels like S7 may be harmed by a rapid quench due to excessive stress.

[ApprenticeMan]

So brine is a harder quench than water?

[ThomasPowers]

Yes 1234567

[ApprenticeMan]

Hmm, I always thought it was slower? I thought in terms of fast to slow quenches, it went water, brine, oil, boiling oil?

[HWooldridge]

Plain water makes larger steam pockets, which is an insulator. It's also a reason why thin items warp in the quench - because some areas are cooling and others are being insulated so stresses develop.

Agitation is the key - a falling column of water works well so if you had, for example, a six inch pipe coming out of a large cistern, you could get a piece quenched pretty quickly if you could dump the water on the item.

[Tyler Murch]

Brine is, shonuff, faster than water.