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Heat treating spring steel and normalizing spring steel.


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So I've already made a post about using spring steel for a makeshift anvil and welding spring steel. I got a lot of support and help! But I was wondering about heat treating spring steel. So I've heard from a couple different knife makers that spring steel is a pretty good material to make knives out of, but spring steel is already hardened (at least the spring steel I have). So I have a couple of questions:

- If your making a knife out of spring steel that is hard enough to dull a drill bit but soft enough to have a file just barely dig into it, does it need to be hardened further?

- If it does need to be hardened further, you would need to normalize it first right? But can you normalize spring steel?

- If you can normalize spring steel, will it eventually get down to the hardness of mild steel? Or will it always stay harder?

- If you can normalize spring steel, does it always remain bendy? Or does it lose its bendiness? 

- Lastly, is my info correct? Is spring steel a good material to make knives out of?

 

I hope I'm not annoying people about all these spring steel questions :D Sorry if I am!

 

 

- Brewny

 

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P.S. : I forgot to add this but if you can normalize spring steel, but it has to be normalized differently from mild steel, how would you normalize it?

 

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The term spring steel is too broad to give accurate answers. Another factor would be, where in the world you are located, springs in Russia, Germany, Israel, Australia may have totally different alloys than say Canada or the USA. Then you have to factor in the type of springs coil or leaf like those for RR cars, airplanes, motorcycles, trucks, cars, firearms etc.

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2021-04-14.jpg2021-04-14.jpg

 

 

Well I live Indonesia. But I'm from America. We run a touring business here in Indonesia called Wild Sumatra Tours. The spring steel I am using is from a big truck. Here are some pics :

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Also are you confusing normalizing with annealing?

You can anneal 5160, a common alloy for automotive springs,  and while it won't be as soft as annealed mild steel; it will still be easier to drill, file, etc.  One thing to be wary of: when you get down to blade thicknesses you often need to put a "helper" piece of steel in the annealing container with the blade to "donate heat" so that the blade cools slowly enough to anneal.  Dry sifted wood ashes make a good annealing compound and are generally easily found.

As to hardness:  most knife blades are harder than leaf springs.  However you want the hardness that *YOU* like.  Things like machetes are often a bit less hard than smaller blades to prevent chipping/cracking in use.

And yes *most* alloys used for automotive springs will make good knives.  (There are low alloy strain hardened springs out there that won't quench harden; but in 40 years of smithing I've only ran across it one time.)

All steels have pretty much the same Youngs Modulus; but annealed spring steel will take a set at a lower point.  So it will stay bent under less force when annealed.

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Brewny: Telling us where you are in one post isn't going to stick in our memories once we open another post. If you put your general location in your header it'll always be there. Your location has a LOT to do with many questions and I hope you're looking for useful information. I know we prefer to provide useful information.

When we're not engaging in a pun thread or joking at each other that is.

Used springs, especially broken ones can have micro fractures and suffer catastrophic failure as blades. blades like machetes and brush knives need to be flexible to work well. Be selective about old springs. I find spring steel to be more forgiving on heat treatment, small mistakes in temp and time have less effect in general performance.

Frosty The Lucky. 

 

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1 hour ago, ThomasPowers said:

Dry sifted wood ashes make a good annealing compound and are generally easily found.

To clarify: wood ashes are good for annealing because they are an effective insulator that is readily available at low-to-no cost. They don't affect the chemical composition of the steel in the way that, for example, case-hardening compound would.

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12 hours ago, ThomasPowers said:

Also are you confusing normalizing with annealing?

I probably am confusing them. I just started making knives a bit more seriously only a couple months ago, and I've learned quite a bit, but there is still SOOOO much that I still need to learn. What I did is I basically just got the plate red- cherry - hot, and I let it cool down normally. How would I "anneal" my plate of steel?

11 hours ago, Frosty said:

Brewny: Telling us where you are in one post isn't going to stick in our memories once we open another post. If you put your general location in your header it'll always be there.

Sorry! I'll put my location on. 

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If you're going to forge the knife  you probably don't need to do any annealing. Just put it in the forge. After you have it forge finished you'll need to normalize it then harden it followed by tempering. 

To anneal the plate you need to heat it to critical and let it cool slowly by burying it in an insulating material like vermiculite. 

 

Pnut

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16 hours ago, Brewny said:

What I did is I basically just got the plate red- cherry - hot, and I let it cool down normally.

Assuming that you're just letting it cool in still air, that's normalizing. 

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If it's actually a low alloy, a bit too much molybdenum or manganese IIRC imparts air quenching qualities so normalizing by regular methods is a hardening quench. I'm a fan of vermiculite or letting a piece cool in the forge. Again that only works on some alloys. 

I've had lime harden steel a couple times due to it's high specific heat. The line quenched the work before it warmed up enough to "insulate" the piece. I started to preheat the lime with a heated bar first.

Frosty The Lucky. 

 

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7 hours ago, JHCC said:

Lime is also hygroscopic, absorbing moisture from the surrounding air. That can affect heat transfer as well.

Doesn't that also form calcium hydroxide? 

Pnut

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pnut, lime is calcium hydroxide (and/or calcium oxide and other stuff). Hygroscopic means that a substance absorbs moisture from the air, either by absorbing it (pulling the water molecules inside it) or by adsorbing it (attracting the water molecules to its surface). However, in neither case is there a chemical reaction between the substance and the moisture, and the water molecules can be driven off by heating or by placing in a desiccating environment.  

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Never had lime harden anything ive annealed. I imagine if it absorbed enough water to have any affect in any way, one might see the consistency change. Perhaps clumps? Naa. I do live where its pretty dry, but i doubt that has any bearing on it. If it hardened steel instead of annealing it, I suspect some other cause. 

Works good in an outhouse too.  ;) Also when cleaning stalls. Lest I forget, its great in a garden.

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1 hour ago, JHCC said:

lime is calcium hydroxide (and/or calcium oxide and other stuff).

I thought quicklime was calcium oxide and slaked lime was calcium hydroxide. I was mistaken anyway. I was thinking of the chemical reaction between lime and wood ash making sodium hydroxide. It's been years since I read anything about it so thanks for prompting some review reading. 

Pnut

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I strongly suggest you read the heat treating sticky!

And please note that terms like Normal can mean very different things to different people.  For instance "normal" out here is 9" of rain a year; Normal where I used to live was 39 inches.  I remember hearing the news where a place was in extreme drought as they had *only* received to date  4 times as much rain as we get in a year.

So please take the time to explain things like normal or usual!

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