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Sunday, March 26, 2017

Quenching Knife Steel

Strange how encounters with different people lead you on a interesting path. spent two days working on a theoretical model for a new quench tank.

Now I have to read up on thermodynamics for heat transfer methods in steel and related alloys, going to be an interesting project and environmentally friendly quite by accident.

Goal is to take a steel from 1500F up to 1950F and cool down to 600F in six seconds or less without the use of water quench which can shatter some steels or the use of oil which has high cost of disposal.

Stage one and the longest I have lots of reading and building of the test facility, sounds like it will be a fun year.

From a previous subject the use of heated water for quenching tool steels. Temperature of the water and addition of Propylene Glycol can greatly influence the cooling rate of a knife blade.

The temperature of water-base quenching baths should preferably be kept around 70 degrees F, but 70 to 90 or 100 degrees F is a safe range. The temperature of the hardening bath has a great deal to do with the hardness obtained.
The higher the temperature of the quenching water, the more nearly does its effect approach that of oil; and if boiling water is used for quenching, it will have an effect even more gentle than that of oil in fact, it would leave the steel nearly soft.
When water is used, it should be “soft” because unsatisfactory results will be obtained with “hard” water.    

A little update, from a heat treating journal written in 1929 where they were looking into heated water to replace oil in some circumstances. All testing was done on a steel that closely resembles AISI 1095 which is a good knife steel that requires a fast oil quench.

Water at 60C is much faster than a fast oil (6 seconds), will have to start testing at 70C on a 1095 steel.

As you can see in the top right graph 80 degree Centigrade water is slower than a fast oil and approaching a 11 second mineral oil.
So a temperature of 70C may match up with a six second oil like a #50 parks. This temperature will be raised or lowered depending on the effects of anti-corrosion agents if used.
From this graph raising the water temperature up to 80C will be suitable for use with 01 steels that harden very well with a medium speed quenching oil.

Na OH = Sodium Hydroxide
Na Cl = Sodium Chloride

1 comment:

  1. Thanks for sharing this very informative article. I appreciate your well written blog.