cold treating blades

[awm]

i had a couple of set treated and have been using them about a wk. i could make no real evaluation as i was waiting on this thursday and friday to do my test. the test involved using an untreated blade in the middle an treated on each side.
about 1230 i had a tire pressure problem . so decided to put
the mower on the ramps and see if i could see a difference.
results were very surprizing . the untreated needed to be replaced then and was markedly duller than the treated ones.
all blades were exmark issue high lifts. i am very surprized as i really was wondering if it would make any real difference.
i dont know how to spell the process but jerry spruell
of COLD FIRE mooresville nc did mine.they have a webb site.
i will be recommending to jerry that he become a lawnsite sponcer as i think this can really help us. later now TM

[AltaLawnCare]

I've heard of hardening steel by heating it, then cooling it with oil. I don't know if this is true or not.

[awm]

i can only report the result of my test . one test is not allconclusive but id have to say right now im convinced
that the process works. a little surprized at how well also.
later now TM

[msd_woody]

You're probably referring to cryrogenic (sp?) freezing. I've heard of this process used on gun barrels to make them more accurate. It's a process of freezing steel at extreme cold temperatures. It's supposed to make the metal more dense and less porus. In the case of mower blades, it would make sense. A dense piece of steel is less likely to chip or nick than a porus one.

Matt

[JLC]

Do you only have to do this process once per blade or will you have to do it each time it is resharpened?

[awm]

that was one of my questions. once its treated it stays that way

[racerdave]

From what I understand it changes the molecular structure of the metal. It causes the molecules to align themselves in nice tight little rows causing the material to become more dense. This also removes areas fo stress in the metal.

Once they have been aligned, resharpening should not change them unless you can get the blade back into a molten state.

David

[crazygator]

Thanks for telling us your experience and keep us informed as to the progress. I have heard of heat treating, but not cold treating. Maybe I will just have to by a bigger freezer now!

[Ricky]

What is the cost of this process and does it make it harder to sharpen?

[lars]

When the molecules are rearranged the pack into a denser shape. This dense shape is smoother on the microscopic level and provides less friction, and thus there is less wear. In some applications life is extended by 8 times. Freezing is popular in agriculture, manufacturing, and automobiles. I've even heard of people freezing the teeth on backhoe and loader buckets.

[awm]

concerning price ,my blades were used as tester by COLDFIRE OF MOORESVILL NC. HE WAS TRYING TO ESTABLISH WHAT TO CHARGE THE LAST TIME I TALKED TO JERRY. i think there was another lco that used this and i think he told what it cost.
im interested also as i plan to have several more sets coldfired.

[awm]

okay just a follow up . sharpened my blades this morning .
just a quick lick with the grinder. again very impressed.
jerry ive left you messages but havnt heard from you.
like to have a couple sets of lighter blades done .

[John DiMartino]

AWM-you might be onto something here,if so congratilations,and cash in while its leading egde(literally).LOL If it could increase life by 4x even,that is a lot of time saved,I know i rarely hit anything,so I could go longer if the edge stayed razor sharp,saving time,and money.

[wallzwallz]

i'm definetly interested in price and continued use/wear+ tear updates,what about continued wet mowing? please post further results when you get a chance thanks

[awm]

somebody on lawnsite named RON i think has been doing this a while.
now. i still cant get a hold of the fella that did mine .
probably at the beach or something.later now TM

[skipwatson]

Here's a place in Chicago:

http://www.coldfirechicago.com/index.html

[awm]

thanks skip i emailed them . im trying to get them to contact chuck.we ll see TM

[alabubba]

From an engineering perspective, the cryogenic treatment of metals has become an accepted and popular technique as a secondary process to follow the quenching of heat-treated parts.

Some of the benefits that it offers are improved stress relief, better dimensional stability, more uniform structural stability, and, most importantly for the LCO, improved wear resistance.

The improvements are connected to the transformation of retained austenite into martensite, and/or the precipitation of newly formed carbides caused by the sub-zero treatment process. Best results are seen for tool steels and high carbon steels, (with wear improvements as great as 500 percent being reported), where the amount of retained austenite normally is high.

Since blade sharpness is a function of wear, cryogenic blade treatment could be a great maintenance-reducer for the LCO. The cost of treatment should be minimal, since the process can be performed with liquified N2, which is a readily available commodity.

When this catches on with LCOs, I would think that it would only be a matter of time before the blade manufacturers would offer cryogenically treated replacement blades, with a reasonable premium, through their ordinary outlets.

[AltaLawnCare]

Wonder if you can only treat the cutting edge.

If that blade strikes something hard, I would rather it bend than shatter.:confused:

[racerdave]

Originally posted by AltaLawnCare
Wonder if you can only treat the cutting edge.

If that blade strikes something hard, I would rather it bend than shatter.:confused:

I don't think you would have the brittleness of a heat treated blade. The stresses have been reduced but the bending moment is not increased substantally.

I beieve Alabubba might know about this.


David

[alabubba]

AltaLawnCare, excellent question which goes straight to the heart of research and development and process development. My thoughts are that the cryogenic treatment process could be controlled so as to be a surface treatment of limited depth. Assuming a typical blade thickness of .2 in, if the thickness of the treatment-affected zone could be controlled, say by controlling the initial temperature of the blade and its time of immersion in the liquid N2, to be about .02 thick, then the core 80% of the blade thickness (0.16) would be certain to maintain its malleability and ductility (components of shatter resistance), however the new leading edges that would be exposed each time the blade was sharpened would always exhibit the improved wear properties.

With that said, however, it is quite possible that the added wear resistance that results from the cryogenic treatment comes without any significant increase in brittleness, therefore not requiring close control of the cryogenic treatment process. If I was a manufacturer, I'd test for that, and if it proved to be the case, viola!

Bottom line? I think awm is participating in a great field experiment, and I'm intuitively thinking the results are going to be benificial for the LCO community sometime in the future.

[awm]

well i dont pretend to understand all of it. i can say though that the blades are niether brittle nor particularly hard to sharpen.
although i have to admit i had to take so little off ,it might be harder to sharpen a completely dulled out blade. later

[sheppard]

This sounds like a great side business for anyone already in the lawn business. The advantage of a local 'company' doing it is the proof of the work. Distant corporations can always 'fudge' on doing the real thing.

Sheppard

[coldfire]

Sorry AWM this reply took so long. As chief Metallurgist for Coldfire Carolina Thermal Cycling Treatment Center, I can hopefully respond to some questions. In general we cycle numerous times between cryogenic and noncryogenic temperatures to achieve our improved material properties.

The process takes about 12 to 16 hours and is permanent, irreversible, and effects not only the surface but also entire crossection of the blade. Thermal cycling creates a more uniform molecular structure. The blade will be tougher, more wear resistant and a bit less brittle.

Wear mechanisims and wear rates are very complex. But in general you should see at least double the life (we guarantee 200%) and less material will be lost during sharpening.

We are a new technology and in our infancy in understanding of the improvement mechanisms. But we do know that we increase yield and tensile strength and relieve stresses from mechanical working. You have a tougher blade.

The cost varies with size, composition, and number of parts but should be less than one half the original cost and with volume orders, as little as one fourth the original cost.

Thanks

[awm]

thanks jerry,youve been very helpful. ill be contacting you later.
right now i got a blade clutch acting up and they estimate 250
for installing new blade engagement clutch thingee. later TM