Spring tempering question

[LRB]

The goals in hardening steel for springs or cutting tools is, or should be, the same. You want fine grain and all the hardening you can get. Both together make up the core of strength in high carbon steels. The only difference between heat treating springs and cutting tools should be the temper. ATF oil works OK for quenching 01 steel, but is too slow in cooling 10xx steels. For cooling 10xx steels, the closest one can get to a commercial quench oil is canola. Canola oil is a fast cooling oil, when heated to 130°. Faster warmed than at ambient because when red hot steel goes into most oils, a vapor jacket around the steel is created, and no drastic cooling occurs until that jacket disperses and allows direct contact between the oil and steel. Warmed canola oil forms very little of this jacket, and cools the steel faster, which is what the 10xx steels require for max hardness. 01 requires a medium cooling speed quench which is more suited to ATF oil. The major cause of broken springs, from my experience, is from large grain growth caused by over heating, improper tools used in removing springs, and as Jerry mentioned, internal flaws, especially in cast springs, which I believe have improved over time. A well cast spring from clean steel can be a very good reliable spring when normalized before HT.

 

[jdkerstetter]

I know you know. It's not you I'm worried about. :wink:

Isn't this fun though? Enjoy, J.D.

 

[dave_person]

Hi Wick,
As always, you provide excellent information. I use 10x steel for springs and successfully used (many, many times) a quench in ATF floating on water. I did that because quenching solely in ATF or any motor oil produced mushy springs. They simply did not cool sufficiently fast to create the proper hardness. You nicely explained the reason for that problem. A good friend is an avid knife maker and metalsmith and he advocates (as you do) using vegetable oil for quenching 10x steel. I am going to try that on my next project. One additional advantage to vegetable oil is that it does not stink badly like any of the ATF or motor oils.

dave

 

[Joe Sullivan]

EUREKA! :applause: One of my springs loaded right up and it's stiff and strong. Wonderfull, just wonderfull. Thank you guy's very much. I learned a lot and I mean to use all this info as I make more spare springs. We have a saying around here"Happy as a clam"

 

[LRB]

Yours is a fairly common and reasonably successful method for fast quenching, which I confess to have never used, but it's not just vege oil. Of all the vege oils, or common lube oils, canola is the fastest when warmed, and the closest you will get to Parks AAA, the best for 10xx steels, and there are no toxic fumes to deal with. If you want the best, invest in some Parks, but it isn't cheap. Gallon vs gallon, Parks isn't too much more, but you have to buy 5 gallons at a time. Minimum.

 

[jerrywh]

Wick knows his stuff.

 

[LRB]

A correction to a misprint in my post. The quench oil best suited for 10xx steels is Parks #50, and not AAA. I had the AAA on my mind because that's what I use for 01 quenching. Sorry for any confusion. Parks #50 cools faster than canola, but canola will get the job done well enough.

 

[Robert Egler]

Faster warmed than at ambient because when red hot steel goes into most oils, a vapor jacket around the steel is created, and no drastic cooling occurs until that jacket disperses and allows direct contact between the oil and steel

Called the Leidenfrost Effect, it is the same reason you can completely dip your hand momentarily into a vat of liquid nitrogen at minus 320 degrees F and not suffer any cold damage to your skin. "Momentarily" is the key word here, the vapor layer lasts only a second or less (trust me on this! :wink: ). A common demonstration in physics classes.

 

[Robert Egler]

Congratulation! Glad to hear it worked out :hatsoff:

 

[LRB]

That, I did not know. I have never had a reason to do cryo treating because of the steels I use, or have used. The problem in heat treating 10xx steels, is that they require a fast quench. 1095 is the hardest to deal with. It requires a short soak at around 1475°, then it goes in the quench, which requires a medium that will lower the temp in .6 to .8 of one second to below 900°, or it will not reach full hardness. That requires brine to completely max out the hardness, but then you are risking cracking the steel. Parks #50 cools it at just a fraction over one second, which is sufficient for most purposes. Canola oil comes right behind at maybe about just under 2 seconds, which still works well enough in most cases. Either oil "usually" prevents cracking. Any slower of a cooling rate, and you would be much better off using a lower carbon 10xx steel such as 1080/84/75.

 

[Joe Sullivan]

Nother Question. :shake: If a person was to make a nice set of springs but he made them too long, being that he's his own worst enemy, could he rework them by heating, making them shorter, quenching and then tempering them again or would he just have to make another set?
:dead:

 

[dave_person]

Hi White Rabbit,
You should have no problem. If the spring requires major change beyond what can be accomplished with a grinder, then reheat the springs to red hot and let cool slowly to anneal them. Reshape the springs and reharden and temper. You can do that as many times as you need to get it right.

dave

 

[Joe Sullivan]

Thanks Dave.
I can't find a way that works for marking my lenght. Soapstone does'nt mark on clean steel. I have a paint marker that works in the fire but I loose it when the part scales over.
I tried scribing a line but loose that in the scale too. Eyeball'n is'nt working. I need to figure out a way of lining up the hot part with an object with my length on it.