More knowledge needed

S

Saia Sailo

Joined
Jun 8, 2021
Messages
5
Hello, I am a beginner and just started making knives, I made it from vehicle leaf spring and grind with a belt grinder, but when I quench it in canola oil, it was not hardened and some kind of scales formed in the steel.

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Welcome! You will have better luck posting in the maker section called shop talk. :)

The scale is pretty normal especially for a home heat treat. There are lots of reasons it might not have hardened. It might not have been hot enough, or wasn't quenched fast enough. Also since you are using mystery metal there is a chance it may not harden at all. Usually the few times I have used a steel I am not sure what it is, I will take a small piece and try and heat treat it first just to double check it can be hardened. I would recommend going to the Shop talk section and looking up the sticky threads. There are some heat treat how tos in those that you would probably find helpful.

Good Luck!
 
S Saia Sailo do you have any of the original material left? If so pound it out to the same thickness as your blade, cut it into several pieces, then heat each piece to your desired temp and quench each one into something different.
Do one in warm water, one in oil and one just let it cool in air.
Then stick each one in the vice and whack it with a hammer. If it breaks, it got hard, and you have an idea on how to HT your steel.
Obviously that isn't the best way, but it'll get the job done.
The best way would be to send a piece of to get tested, so you know what the composition is, then you could develop a real HT protocol that can get the most out of the steel.... But that's expensive.
 
Leaf Spring steel is usually 5160 steel. Here's the HT process for that kind of steel.

knifesteelnerds.com

How to Heat Treat 5160 - Optimizing Toughness - Knife Steel Nerds

How does the toughness of 5160 compare with other knife steels? How do you heat treat 5160 to ensure that the properties are maximized?
knifesteelnerds.com knifesteelnerds.com

I am a beginner as well, and use 1084 steel for the time being. It is much easier to work with and HT, as the HT process is very basic and almost foolproof. I don't forge though. I just do stock removal.
 
Leaf springs used to be 5160 in the1940's, but today they can be many alloys. 5160 isn't normally one of them anymore. However, the HT for 5160 will usually work.

What I see on that blade is badly burned canola oil. The blade must have been very hot to do that.
The blistering also indicates overheating.
There is a good layer of decarb on a blade after quenching, and that layer can be very thick if the blade was overheated. Grind the blade down to a good edge and test for hard steel again. You will likely have to grind away a couple hundredths of an inch (.25-.5mm) of thickness to get to the good steel. Grind the edge back at least 1/16"/1.5mm to get rid of the burnt out edge.

Here is how to do a home HT on a leaf spring:
Grind the blade to about 80% done. Leave a little to grind away after HT.
Heat slowly and evenly to where a magnet does not stick anymore. The steel is around 1400F/760C then.
Heat to a full shade redder - 1500-1525F/815-830C. Watch the edge so as not to overheat it. It is OK if the spine isn't as hot as long as the edge area is at the proper temperature.
Immediately quench in 2 gallons of canola oil warmed to 120F/50C. Move up and down and keep in then oil for 10 full seconds. Remove and immediately straighten any warp before it cools down to 400F/200C. Do not try to straighten anymore once it gets cooled down to 400F/200C or it will break.
Let cool to room temperature and then temper twice at 400F/200C to 450F/230C
Grind the blade clean of all scale and decarb, then test the edge with a file.
 
Stacy E. Apelt - Bladesmith said:
Leaf springs used to be 5160 in the1940's, but today they can be many alloys. 5160 isn't normally one of them anymore. However, the HT for 5160 will usually work.

What I see on that blade is badly burned canola oil. The blade must have been very hot to do that.
The blistering also indicates overheating.
There is a good layer of decarb on a blade after quenching, and that layer can be very thick if the blade was overheated. Grind the blade down to a good edge and test for hard steel again. You will likely have to grind away a couple hundredths of an inch (.25-.5mm) of thickness to get to the good steel. Grind the edge back at least 1/16"/1.5mm to get rid of the burnt out edge.

Here is how to do a home HT on a leaf spring:
Grind the blade to about 80% done. Leave a little to grind away after HT.
Heat slowly and evenly to where a magnet does not stick anymore. The steel is around 1400F/760C then.
Heat to a full shade redder - 1500-1525F/815-830C. Watch the edge so as not to overheat it. It is OK if the spine isn't as hot as long as the edge area is at the proper temperature.
Immediately quench in 2 gallons of canola oil warmed to 120F/50C. Move up and down and keep in then oil for 10 full seconds. Remove and immediately straighten any warp before it cools down to 400F/200C. Do not try to straighten anymore once it gets cooled down to 400F/200C or it will break.
Let cool to room temperature and then temper twice at 400F/200C to 450F/230C
Grind the blade clean of all scale and decarb, then test the edge with a file.
Click to expand...
Thanks. I'll follow these steps. One more Question.Should I insert the blade into the furnace only after the temperature had reach 830C?
OR
should I insert the blade before and slowly heat the blade as the furnace temperature rises.?
You are absolutely correct regarding the overheating, first I set the temperature to about 850 C and wait for a while but the blade had not reached the unmagnetic stage as fast as I had hope, So I again raised the temperature to about 1020C so that it would reached the unmagnetic stage faster.
I should set the temperature to around 830C only no matter how long it will take to reach the unmagnetic stage, Right?
Does it also mean that the blade is the useless now, or is there still a chance to repair it?
 
Last edited:
A.McPherson said:
S Saia Sailo do you have any of the original material left? If so pound it out to the same thickness as your blade, cut it into several pieces, then heat each piece to your desired temp and quench each one into something different.
Do one in warm water, one in oil and one just let it cool in air.
Then stick each one in the vice and whack it with a hammer. If it breaks, it got hard, and you have an idea on how to HT your steel.
Obviously that isn't the best way, but it'll get the job done.
The best way would be to send a piece of to get tested, so you know what the composition is, then you could develop a real HT protocol that can get the most out of the steel.... But that's expensive.
Click to expand...
Thank you, I will experiment it like you said to know the difference when quenching it into oil and water. If it's possible.
 
If yu are using a HT oven:
Heat the oven to 830C and once it has stabilized at that temperature put the blade in. When the temperature has rebounded to 830, start the timer. Heat for 10 minutes, remove and quench. It is important to have a sufficient volume of quench oil. 2 gallons is a good amount for most knives.
 
Stacy E. Apelt - Bladesmith said:
If yu are using a HT oven:
Heat the oven to 830C and once it has stabilized at that temperature put the blade in. When the temperature has rebounded to 830, start the timer. Heat for 10 minutes, remove and quench. It is important to have a sufficient volume of quench oil. 2 gallons is a good amount for most knives.
Click to expand...
Thank you very much for the reply, I will follow your method
 
I don't know where you live but in North America it is really inexpensive to get knife grade steel. In fact if anyone is close to you they will probably give you some. I'm in NY but could send you a piece if you are in the United States. If you fill out your profile someone might be close and can help you out or show you some basics. My favorite place to get supplies is Pops knife supply. They have fantastic prices on everything and they have 8670 steel for a incredible price and it's a fantastic steel. The usual steels they recommend are 1084 and 80CrV2 (if you get this steel from many places you might need a extra step in heat treatment. My favorite beginner steel is 15n20. It's super easy to work with and I have never had any problems with it and it's probably a bit tougher and doesn't rust quite as bad as the others. The only downside is that it only comes in thin stock. Just because these are called beginner steels doesn't mean they aren't good. 1084 and 15n20 are what is used for most Damascus and get crazy sharp super easy. Good luck with your journey. Let us know how it goes and if there is anything we can do to help just ask.
 
One thing you could try is water quench on a test piece. I had leaf springs from my old mans toyota land cruiser from the late ninetys and I wasn't able to harden it with canolla oil no matter how hard I tried. Same thing actually happened with a part of the suspension of the same car. I did three different test in canolla oil trying two temperatures at and using warm oil and one temperature at cold oil but no luck. When I did the water quench test it hardened on the first test after I heated to a shade over nonmagnetic.
 
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