Thread: Interupted quench??

Hi,
Need to heat treat first blade 1084. I'm not prepared to pay for 25 litres of formulated quenchant (have made enquiries) . As next best thing will use heated peanut or canola oil. Read tons about interupting the quench and was wondering how it was done? Looking at the charts I figure I could pull the blade after 5 - 10 seconds agitated in the oil? I don't really know, can anyone elaborate? Is it really neccessary for 1084? Alternativley , does anyone know where I can get about 5L of formulated in the UK?

have you tried talking to the guys at the brittishblades forum they will now how to help you

Originally Posted by Deckard

Hi,
Need to heat treat first blade 1084. I'm not prepared to pay for 25 litres of formulated quenchant (have made enquiries) . As next best thing will use heated peanut or canola oil. Read tons about interupting the quench and was wondering how it was done? Looking at the charts I figure I could pull the blade after 5 - 10 seconds agitated in the oil? I don't really know, can anyone elaborate? Is it really neccessary for 1084? Alternativley , does anyone know where I can get about 5L of formulated in the UK?

What are you hoping to accomplish with the interrupted quench? How hot were you planning to get your heated oil?

There are good reasons to use an interrupted quench and super hot (400-degrees F) oil, but I don't think you need to worry about them right now.

1084 is very forgiving, and your canola or peanut oil will work just fine. An interrupted quench is usually used when quenching in water or brine. Done right it minimizes the chances of cracking the blade.

Get your steel to just above non-magnetic and quench quickly in 120-degree F canola oil and you'll be fine.

Good luck,

Josh

Chuckle. The formation of martensite occurs at the speed of sound. 1084 has about 0.8% manganese and was designed to through harden when quenched. By the time a second or two has passed, you've done all you can do with this steel and the steel will be faster than you.

Originally Posted by JoshEarl

What are you hoping to accomplish with the interrupted quench? How hot were you planning to get your heated oil?

There are good reasons to use an interrupted quench and super hot (400-degrees F) oil, but I don't think you need to worry about them right now.

1084 is very forgiving, and your canola or peanut oil will work just fine. An interrupted quench is usually used when quenching in water or brine. Done right it minimizes the chances of cracking the blade.

Get your steel to just above non-magnetic and quench quickly in 120-degree F canola oil and you'll be fine.

Good luck,

Josh

Thanks,

There is lots I don't know about steel and heat treat (yet), so I ask dumb questions sometimes. I read and watch stuff on the net and some ideas may not always be good ideas? I saw somewhere that this is advocated to avoid risk of cracking by lowering internal stresses during ht? My understanding is that industrial quenchant has a faster heat trasfer rate at the higher temperatures and this practice is "supposed" to mimick this effect? Not sure what type of steel was being treated but thanks for clarification for 1084.

Would your recomendations still be good for 1095 or O1 type steels?

It's not a dumb question. One problem with learning from the Web is that there often isn't any progression to the information you encounter--you're exposed to advanced stuff along with the basics, and it's hard to sort out what is foundational and what is optional.

There are two approaches you can take here. If you just want to make a few blades for fun, find a good heat treating recipie that you can follow with whatever equipment you have, and try to stick with that. Nothing wrong with this approach at all.

If you decide that you're really into it and want to try some advanced stuff, get a good book on basic metallurgy and start reading. You need some foundational knowledge before you can understand what techniques like interrupted quenches, marquenching, nitrogen baths, etc. can do.

1084 is an excellent choice when you're starting out. You can use a magnet to judge temperature, as the proper hardening temperature for this steel is very close to the point where steel loses its magnetism. (That isn't necessarily true for other steels.) You don't want to overshoot too much--getting the edge hotter than the rest of the blade is especially bad. If the steel gets too hot, you'll weaken the edge.

1084 will harden very well in canola or peanut oils. Heat the oil to about 120 degrees F, which (believe it or not) actually helps the oil cool the steel faster.

You are correct that commercial heat treating oils are specially designed to cool very fast in the upper ranges and then gently slow the cooling toward the lower range. 1084 is not particularly prone to cracking in oil, though. I've personally never seen an oil-quenched blade crack, even when ground thin. Usually they warp instead, which can be just as bad. Cracking is more of a problem in brine or water, which put a lot of stress on the steel. Interrupting the quench is usually done with water quenches where the chances of ruining the blade are higher.

1095 and O1 are also excellent steels, but both benefit from better control over your temperatures. 1095 demands very fast cooling and almost requires a commercial heat treating oil, and you also need to get it hotter than 1084 but without overheating it. O1 requires that you get it to the proper temperature and then hold it there for 10 to 20 minutes--again without overheating it. Hard to do without a good forge or kiln.

I would stick to 1084 right now. It's very good steel and is similar to the composition of most vintage razors.

Keep reading and asking questions.

Josh

Originally Posted by JoshEarl

...find a good heat treating recipie that you can follow with whatever equipment you have, and try to stick with that. Nothing wrong with this approach at all.

Allow me to reinforce this concept. There are a great many more blades that have been made throughout history that did not have any of the fancy metallurgical treatments than have been made in the past sixty years. Our ancestors did very well with the simplest of methods and equipment.

Chasing after unobtanium or wunderstahl, or the most scientific quenchant and the best kind of forge or grinder and all manner of specialized tooling will do only one thing; it will distract you from making anything. Get some blades done, quench them in simple fluids. Try some water just to see what happens. I particularly like water for quenching. But a long time ago I started listening to the steel talk to me. It's a much better teacher than all the words you read here. It will only talk to you when you play with it. Yes, you'll break some blades. But you won't learn anything significant without making mistakes either.

Keep things simple and the mistakes in the early years are much less expensive.

Excellent.

I have watched Kevin Cashen (MS) perform interrupted quenchs on 1084 blades on several occasions. The technique works (I have used it myself) and has several benefits; chiefly, it allows you a chance to correct any warping and gives a sort of auto temper to the blade. As part of his heat treating demonstrations, Kevin will often bend the blade as he pulls it out of the interrupted quench, then straighten it again before the blade fully hardens.

When you are heat treating a blade, you heat it to the proper temperature for the steel, soak at temperature, then quench the blade. Once the temperature of the blade has dropped sufficiently fast enough to beat the Pearlite nose on the TTT chart, it will form Martensite as it cools to room temperature. The speed with which it achieves room temperature is not critical (unless you prevent it), and slower speeds are less stressful on the blade.

When you are interrupting a quench, you are usually trying to remove your blade when it gets to about 400 degrees F. Then, as it cools it gives an auto temper to the blade and makes the blade less likely to crack before you can get it into a tempering oven.

I'm sure Kevin Cashen can explain this procedure and why it works much better than I, but it does work. I believe that Kevin has posted explanations on the BladeForums website. I'll try to post links later...

Originally Posted by ChrisMeyer

I have watched Kevin Cashen (MS) perform interrupted quenchs on 1084 blades on several occasions. The technique works (I have used it myself) and has several benefits; chiefly, it allows you a chance to correct any warping and gives a sort of auto temper to the blade. As part of his heat treating demonstrations, Kevin will often bend the blade as he pulls it out of the interrupted quench, then straighten it again before the blade fully hardens.

When you are heat treating a blade, you heat it to the proper temperature for the steel, soak at temperature, then quench the blade. Once the temperature of the blade has dropped sufficiently fast enough to beat the Pearlite nose on the TTT chart, it will form Martensite as it cools to room temperature. The speed with which it achieves room temperature is not critical (unless you prevent it), and slower speeds are less stressful on the blade.

When you are interrupting a quench, you are usually trying to remove your blade when it gets to about 400 degrees F. Then, as it cools it gives an auto temper to the blade and makes the blade less likely to crack before you can get it into a tempering oven.

I'm sure Kevin Cashen can explain this procedure and why it works much better than I, but it does work. I believe that Kevin has posted explanations on the BladeForums website. I'll try to post links later...

How about if I take a shot at the problem? No point in ordering online when you can buy local...

There is a line on the TTT diagram that is labelled M sub S that indicates the Martensite Start temperature. There is a second line labelled M sub F that indicates Martensite Finish temperature. This portion of the isothermal transformation diagram is not auto-tempering. Untempered martensite occurs after M sub F temperatures. It still needs a tempering cycle or more depending on whatever recipe you choose.

Between those two lines is where all the potential magic can happen with a smith asute enough to understand what the curves are saying.

Time is a critical element. If there is a significant length of time, in essence the smith (Kevin) delays the movement toward M sub F after crossing the M sub S line, there is all that time to bend, straighten, correct warpage etc. and play with what essentially remains a plastic material. Once M sub F is reached, all the play time is over. The material stiffens considerably and is now prone to cracking if stressed too much.

Then temper the blade to reduce brittleness and improve toughness.

Things have to be done in the right order, for the right amount of time at the right temperature, and for the right reasons. You can't cheat steel or the heat treatment.