Eye opening quench test results.

Although I am very careful to protect the privacy of my clients for whom I do consulting and testing, this research has so much educational value that I asked for permission to share some of the results with my knifemaking friends. I am currently involved in a project to help a quenchant manufacturer (not Parks or Houghton) develop some oils to specifically meet the demands of certain steels. The first goal is a very fast oil that will work for shallow hardening steels, so I am testing with a fast oil control.

Below you will see results from one of the first prototype formulations, starting at lower speeds, on 1095. 1095 is one of the toughest to thoroughly harden so I thought it would be a good challenge. The samples where ground from the same bar of steel, austenitized side by side with direct thermocouple monitoring in salts, and quenched side by side in identical quantities of oils and agitation, surrounded by a 125F bath to assure temperature. The results were then cross sectioned and roughly polished for metallographic examination (so please overlook the scratches). Micrographs were actually taken at 1mm increments from the edge but I only took a sampling to put this image on the web. After this the samples were then tested for Rockwell hardness at roughly 3mm increments.



The light background is martensite (the good hard stuff we want), the dark stuff, making it look like blue cheese, is fine pearlite (the soft stuff that quenching is supposed to avoid). Please be aware that at the edge both of these samples would have skated a file just fine, would have flexed over a brass rod all you want, and would even have cut a few 2x4” with little problem. But every little black patch represents a percentage of overall loss in strength, and long term edge retention.

Do be aware that that prototype oil would probably have held its own against many medium speed oils and was made by guys who’s business it is to make oils specifically for quenching and know what they are doing. This was a good oil but was still a first step in moving from medium to the fast speed, with a few adjustments that were yet needed to reach the goal, and many more tests in that process. But the speed factor is just one area among many to account for, long term stability, vapor points, interaction with the surface finish etc…

The real point of this post is that making a real quench oil isn’t all that simple and testing it is even less so, believe it or not these are just rough preliminary tests and not all that exhaustive. I hope this gives somewhat of an insight as to my perspective when I express my doubts about all the homemade and improvised quenchants some folks feel work “just fine”, and I hope it gives pause to those of who feel carefully formulated quenchants are unnecessary.

 

Interesting question, since the speed of aging oil is not always slower. Yes both samples where fresh and ready for the test.

 

I have put the Parks bug in enough peoples head that I feel somewhat obligated to help in moving the industry forward in providing more equivalents. But in the meantime I feel it right to share the lessons I myself am learning about the intricacies of properly quenching steel. Many are very happy with "good enough" and what they are currently using, but when you can clearly see how much of a gain you can get I am sure there are many who will want to go for it.

 

Actually that has been true for around 5 years now, but now fate and forces beyond my power to oppose are bringing it to fruition whether my procrastinating self likes it or not (in other words my wife will simply slip a knife between my ribs if I put it off any longer)

 

Martensite is more tinny flavor, while pearlite tastes more chalky:barf: I tried to taste austenite once in 1095 but only picked up the flavor of scorched tongue too bad it would have been handy to determine how much retained austenite many tool steels could have. One can try stainless but the peppery bite of chromium totally overpowers it.