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Jack Wheet

Hardest Steel I've Ever Worked

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I've barely gotten ahead in my bladesmithing experience, but after a while, I knew enough to realize that continuing to use mild steel to make knives just wasn't gonna cut it (no pun intended). Having heard that nearly all types of spring steel make decent blades, I contacted a friend, who gave me the thinnest and thickest leaves of a leaf spring.

Photo

When I decided to try out the material, I cut off a section of the thicker leaf with an abrasive disc chop saw. Due to its thickness, I expected a long cut time, but not anything like the ~15 minutes I spent holding that saw to the steel. "Whatever," I thought, "Let's just see how it forges." 

The only time I was able to forge was for 25 minutes or so during my lunch in my high school's forging setup, and I quenched the piece after every working period to cool it enough to store. To me, that daily hardening explained why it would initially be hard to work. However, I can't explain why, after hand-hammering it for a grand total of about 7-8 hours, the thing was only 0.5" wider and 0.75" longer than when I started. At the end of the school year, I wanted to cut the piece smaller in line with a crack that had formed, so I took it to the shop's 3.5 ton hydraulic shear. The blade lowered, touched the steel, and nearly instantly, a section of the steel shot 6 feet out the back of the machine; almost no deformation whatsoever, just a straight fracture across the piece. 

So my question: Am I doing something wrong, or have I just found myself in the possession of extraordinarily hard stock that is impossible to work without a hydraulic press/power hammer? 

 

 

 

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A couple of things, the abrasive disc you mention, is that a cut-off disc for metal or for stone? If the latter, it's not suitable. A cutt-off disc for metal should get through without trouble, whether the steel is hardened or not.

Second, while forging, are you getting it hot enough? Don't forge when it's gone below orange, that's too cold. Do you have a decent size hammer, and anvil? If your tools are too light, and if you anvil is not fixed well enough (does it bounce?) then most of your physical effort is not going into deformation of the steel.

And finally: don't quench the steel when it's glowing. Let it air cool for a while, then you can quench it without hardening. From what you describe, you hardened the material when you tried to cut it, which is then extremely hard and brittle. Cutting that with a hydraulic shear is extremely dangerous, as one of those pieces that shot off could have gone straight through you. So don't do that again. If you want to cut, use a cut off disc suitable for metal, or hot cut the steel with a hot cutting chisel or hardy. 

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Have to agree with Mr. Zuiderwijk.

Another thing to remember is  leaf spring can be various grades of steel , some of which may be partially air hardening, so a slow cooling is always advisable before any cold work . Something like an AISI 5160 will be a little harder under than hammer than a 1060 or 1070 but they should still work easily at forging heats. Makes me wonder if you are trying to work the steels too cold.

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I can confirm from my experience leaf springs are not that hard to move.

Apart from working too cold as has been mentioned, possibly you are trying to work too large a piece steel.

The photo is too small, but it looks like you started with the thickest (10mm, normally close to flat) part right at the bottom.  That's a lot of steel to heat up and move.....might be better to start with the 8mm curved parts.

As far as the quench between forging sessions go, that sounds like a very bad idea, except if it's to get rid of the last bit of heat before storage.

If it's anywhere near working heat and you are presumably quenching in water, that would cause cracks.

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I agree with the above but will say that a chop saw (for me) has skated right over mild steel for a long period of time before cutting. I'm not sure why, but it did. It wasn't my saw so I didn't bother messing with it further. I assumed the blade may have gotten loaded up with molten metal and started to skate on itself. Try "dressing" the wheel with something to remove the caked on metal?

Whenever the steel is fracturing, you are working it too cold. But, the steel should move when you hit it hot enough. I would throw the portion you were working away. Lots of stress cracks I'd bet. 

People will advise you to start with bought steel to remove as many variables as possible. This is sound advice. My opinion is do it however you can within your means. You'll probably ruin a good few pieces to start. Do your homework though. 

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I agree with everyone but, by my nature, have my own perspective. You have learned from the advice already given that there is a lot more to this than just "heating and beating" . Now you can begin your real education on the, seemingly, little details that make the gigantic differences. Go to the section in this forum on metalurgy and heat treating. Read, read a lot. You have to have in your mind, ahead of time, a very good idea of how hot you want to get the steel and, importantly, WHY you want to get it to a certain temperature for each step. This also includes when you want to quench it and, again, WHY you want to, or don't want to at a certain point. Everything you do to steel regarding heat has an effect. You need to know what you are trying to specifically do to the steel and what changes are happening to it. Some changes can be relatively benign and others can drastically change its form. Become familiar with terms like "pearlite and pearlite anneal, lamellar anneal, austenizing, decalescence, recalescence, critical temperature" and other terms you encounter in your research. At some point you will come to an "AH-HA" moment. The whole picture will become clear, well mostly. There are a thousand little details related to alloys and quenchants that are so specific they need to be learned individually on a case-by-case basis, but the big picture remains the same. For instance you didnt specify your quenchant liquid but I suspect it might have been water. That is, as a general, very general, rule something that is not suggested for this type of work. You will find out why in your research. As another wild "rule of thumb" if you have hammered for an hour, as a beginner, and you don't have something resembling a blade-shaped-object yet then either it's the wrong steel for you, it is too thick or you are not getting it hot enough. Ag ain, a rule of thumb but in that general time frame.

Keep trying, research and ask questions. Good luck.

 

Edited by Vern Wimmer

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The answer lies in the advice that has already been given, but I'm curious what you were using for a hammer.  You mention a high school shop.  You weren't using a 10oz ball-pein were you?

Even poor technique with a 2-lb hammer for that long should have moved more metal, and no, it isn't the spring's fault.  I doubt that it was made out of something very exotic.

 

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After Saturday's fun I might have to retract what I said.....

I have several orders for cleavers but no suitable material to make them from, best option 8mm thick leaf spring from a Toyota Land Cruiser.

I started on a piece at the end of a previous forging session, struggled a bit and just assumed I was tired.....

Saturday a friend dropped by and we took turns holding and striking, and it was not easy.....

I've forged some of that very same leaf spring before without much hassle, but I realised it was always narrower pieces I'd cut out, never the full width spring........?

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hey jack stay away from the shear high carbon steel has no place there

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After many failures leading me to this point, I can tell you that you are going to be uncovering variables for a long time.  This is an art for a reason, and there's nothing easy about mapping out what you can get away with and what you can't.  I have maybe 100-150 hours of forge time over the last 4 months, and I'm still a supernoob.  That said, all the advice here is good, from what I can tell.  Make sure you are heating to at least bright orange, preferably yellow.  If you are having that much trouble with it, the only thing to do is get it hotter.  Hit it with the heaviest hammer you can manage.  Don't tap.  Beat it hard.  Just don't hit it so hard that you have no control and mangle it.

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2 hours ago, Aaron Rheams said:

  Hit it with the heaviest hammer you can manage.  Don't tap.  Beat it hard.  Just don't hit it so hard that you have no control and mangle it.

Within reason, and one that you've worked up to.  If you start with a four-pound hammer you're going to hurt yourself sooner rather than later.  Most people are comfortable starting with a 2.5 lb / 1000 g hammer.  Once you get comfortable working with that weight for long periods, then you can move up IF you find it necessary.  My main sword hammer is 800 grams.  My axemaking hammer is 2.5 pounds.    My BIG axemaking hammer is 3.5 pounds.  And I've been doing this 20 years now.

Otherwise, yes.  Get it yellow hot, hit it hard, stop hitting it when it turns red.  DO NOT QUENCH.  And do not EVER put hardened high carbon steel in a hydraulic shear, it will kill you or the machine.

This is all assuming you're not just trolling us, which I suspected you might be at first.  

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I have had metal cutting abrasive wheels not cut through HC steel before and it was usually caused by the edge of the wheel glazing over during long cut times. The edge can be cleaned with a grinding stone conditioner or by running the saw full-out and bouncing it on the work piece lightly (the second option is kind of dangerous). It will resume cutting again.

When forging HC steels and you anticipate not completing the forging in a single session, you should normalize before you store it. Bring the steel up to past critical temp and let air cool until all color disappears when held in shadow or the dark (typically this is about 800* F) and then you can quench to remove the residual heat. Water quench is fine for this regardless of what was said above. It will cause no effective hardening. 

In your post, you said this was the hardest steel you have ever forged, but I see from your previous posts that you have only been forging for a short time, so the comparison is vague at best. Without knowing a lot of the details about what the steel really is, what heat you are forging at, what equipment you are using, and what the quechant and quench temps were, it's very difficult to pin down what is happening. Leaf springs are notoriously varied unless they are more than say 20 years old. In which case they are not ideal because they probably are so damaged that they will form more cracks than you could work around.

Edited by Joshua States

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6 minutes ago, Alan Longmire said:

This is all assuming you're not just trolling us, which I suspected you might be at first. 

Hey, at least he has a name other than "Guest":D

  • Haha 1

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Joshua is correct about the water quench having no hardening affect at below 800f of full dark color. I just stay away from water as a method of avoiding problems in general. I use it with a grinder to keep steel cool when grinding but do not keep a tank or large container around with water in it to avoid mistakes.

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On ‎1‎/‎14‎/‎2019 at 1:08 PM, Vern Wimmer said:

Joshua is correct about the water quench having no hardening affect at below 800f of full dark color. I just stay away from water as a method of avoiding problems in general. I use it with a grinder to keep steel cool when grinding but do not keep a tank or large container around with water in it to avoid mistakes.

OK, Vern, I'll come right out and ask. Do you actually do any forging? You should always have a slack tub of water in your forging area, every smithy I've ever stood in or seen a photo of, has one. If for nothing else, regularly quenching your tongs, or putting out the occasional small unintended fire.

Edited by Joshua States
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Yes I do. Get the hair pulled out. I also have a big and faucet in my shop. I just don't keep a tank of water there because I have a habit of getting in a hurry with out steel and also don't always have the best light to determine temperature with. Matter of fact I hope to have a chance to post up some shop pictures in the next few days since the weather is cooperating and we are having a warm session. My shop i am sure you will find quite interesting.

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I'm just asking. I've never seen anything from you is all and I was starting to wonder.......

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Leaf spring is easier to forge with somebody holding it for you.
Vinegar removes scale.

Patience is a virtue.

Practice gets you to Wimbledon.

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On 1/14/2019 at 1:30 PM, Joshua States said:

Hey, at least he has a name other than "Guest":D

... And then Alan was like "the dawn will take you all!"... See what I did there? Huhhh? The reference!? Huhhh!? Trolls!!?? :D

Sorry, I been reading The Hobbit.

 

That blade looks pretty choppy there Gerhard! B)

 

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4 hours ago, Gerhard said:

Leaf spring is easier to forge with somebody holding it for you.
Vinegar removes scale.

Patience is a virtue.

Practice gets you to Wimbledon.

IMG_20190112_183535.jpg

IMG_20190114_162828.jpg

IMG_20190114_173119.jpg

IMG_20190115_163925.jpg

IMG_20190115_173720.jpg

IMG-20190114-WA0001.jpeg

IMG-20190114-WA0003.jpeg

IMG-20190114-WA0010.jpeg

Now that is a very nice cleaver, looks nicer than the one I have.

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Not only is a slack tub good for cooling hot tongs it's also good for cooling overheated body parts or a source of water to pour over your head.  I would consider them necessary safety equipment.

Doug

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On 1/11/2019 at 2:15 AM, Jeroen Zuiderwijk said:

A couple of things, the abrasive disc you mention, is that a cut-off disc for metal or for stone? If the latter, it's not suitable. A cutt-off disc for metal should get through without trouble, whether the steel is hardened or not.

Second, while forging, are you getting it hot enough? Don't forge when it's gone below orange, that's too cold. Do you have a decent size hammer, and anvil? If your tools are too light, and if you anvil is not fixed well enough (does it bounce?) then most of your physical effort is not going into deformation of the steel.

And finally: don't quench the steel when it's glowing. Let it air cool for a while, then you can quench it without hardening. From what you describe, you hardened the material when you tried to cut it, which is then extremely hard and brittle. Cutting that with a hydraulic shear is extremely dangerous, as one of those pieces that shot off could have gone straight through you. So don't do that again. If you want to cut, use a cut off disc suitable for metal, or hot cut the steel with a hot cutting chisel or hardy. 

The cutoff saw was in my high school's metal shop, so yes, it was for metal. My best guess is that the disc had just seen quite a bit of use from several classes of machining students, making it quite worn down.

I can guarantee that I was getting the steel hot enough, I was heating it to a bright yellow, almost yellow-white. I can't give a weight for the anvil, but it was heavy and secured enough that it never shifted, and the hammer I was using was a 4 lb Kobalt cross-peen.

When I did quench it, there was always little-to-no glow. Is it possible that the steel could've retained a high enough temp inside to internally harden? When I did shear it (yes, I realize there's some risk in that, but I had the piece double-clamped on the input side, and the output was pointed towards a wall 10 feet away), the internal grain was huge. I would've cut it with the cut-off saw, but this was on the last day of the school year, coming up on when I had to catch a bus, so I was looking for a quick option.

Sorry if it seems like I'm trying to rebuke all your advice, I'm just expanding on my original information so I can find out why the steel was acting so weird.

Edited by Jack Wheet

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On 1/11/2019 at 2:37 AM, MacKINNON said:

Have to agree with Mr. Zuiderwijk.

Another thing to remember is  leaf spring can be various grades of steel , some of which may be partially air hardening, so a slow cooling is always advisable before any cold work . Something like an AISI 5160 will be a little harder under than hammer than a 1060 or 1070 but they should still work easily at forging heats. Makes me wonder if you are trying to work the steels too cold.

I had found that, but was unable to find out specifically what grade my leaf was, so it's currently a mystery material. Like I told Jeroen, I am confident I was forging hot enough because I was hammering at forge welding temperatures, which, even with my amateur knowledge, I know is hot enough to make nearly all steels workable.

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On 1/14/2019 at 12:23 PM, Alan Longmire said:

Within reason, and one that you've worked up to.  If you start with a four-pound hammer you're going to hurt yourself sooner rather than later.  Most people are comfortable starting with a 2.5 lb / 1000 g hammer.  Once you get comfortable working with that weight for long periods, then you can move up IF you find it necessary.  My main sword hammer is 800 grams.  My axemaking hammer is 2.5 pounds.    My BIG axemaking hammer is 3.5 pounds.  And I've been doing this 20 years now.

Otherwise, yes.  Get it yellow hot, hit it hard, stop hitting it when it turns red.  DO NOT QUENCH.  And do not EVER put hardened high carbon steel in a hydraulic shear, it will kill you or the machine.

This is all assuming you're not just trolling us, which I suspected you might be at first.  

I can assure you, I am not trolling, simply trying to learn how a chunk of spring steel managed to best me. 

As for hammers, I did work up to the 4 lb cross-peen that I used to attempt to beat this spring into submission. I first started with a one pound ballpeen to make a simple mild steel coat hook, then moved up to a 2.5 pound mini-sledge for larger projects. Due to the thickness of the leaf spring section, I opted for the 4 lb hammer to give more force behind my swings.

When you say "DO NOT QUENCH," I assume you, like the other comments, mean don't quench when the steel is still glowing? Whenever I did dunk it, it was after there was no glow remaining, just to cool the steel before storage. 

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Glad you're not trolling! :)

And yes, the "do not quench" was from any glowing heat.  

I suspect it's just a thick piece and more than you can currently deal with.  That is not a put-down, it happens to us all when we start out.  You should have seen the first time I tried to hand forge a 1.5" sway bar, about two months after I began forging.  Barely dented it.  A few years later I stuck it under a power hammer and it squooshed just fine.  Once I had it down to around 3/8" thick it worked just like any leaf spring I've used, i.e. tougher than snot, but manageable.  

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