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Overheating a blade


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I am new to the forum so forgive me if I post this question in the wrong category.  

I have a knife I forged from coil spring and when I quenched it in oil it would not get hard.  After three attempts I tried water and the blade was still easy to cut with a file. I saw a couple of sparks shoot off the blade once during the forging process.  Do you think I over heated the blade and caused this problem?

 

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Have you checked that exact coil spring to see if it hardens without the over heating?  What type of coil spring is it?  In 40 years of smithing I've actually run into one low alloy strain hardened leaf spring---it couldn't be quench hardened.

What was your heat treat process? (The answer to your question is Yes, No, Maybe depending on information you haven't provided.)

Did you normalize?   What type of oil were you using? Was the oil at around 140 degF when quenched in?   How long did you have it in the forge?  Many people starting out take so long to forge a blade that they decarburize the stock in the forge.  (One reason I suggest folks not do knives till they got their forging down pat.)

Did you try filing deep or breaking to see if the issue was a surface decarb issue?

Have you thought of attending the American Bladesmiths Society school in Texarkana?

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Dear Odie,

There are lots of reasons why something made from an old coil spring will not harden or temper like new stock.  It could be some weird alloy, you might have de-carburized it while forging it at a high heat too many times, it might need very special heat treating, or a dozen other things.  That is why, when using a piece of steel of unknown qualities, you should take a small piece, forge it out to a flat, quench it, test for hardness with a file and putting it in your vise and hitting it sideways to see if it breaks off, examining the grain structure at the break,  and test the tempering process.  Take notes and label the remaining part so that you only have to do this once.

This should be done BEFORE you forge anything out of it so that you don't waste your time and effort on something that won't heat treat properly.

Also, using old coil springs is sometimes problematic because if they have been in hard and long use they may have developed internal micro fractures.  Basically, do you think it would be better to spend your time forging something out of material with unknown qualities and may have been through hundreds of thousands compression and expansion cycles or something new with known qualities.

"By hammer and hand all arts do stand."  

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To tell you guys the truth I have not test a piece to see if it will harden.  I took it for granted that it was spring steel and should be fine.  Rookie mistake.   Lol.  I don't know what vehicle it came from.  I am practicing my my forging skills on small blacksmith style knives with a squirrel tail tang so I can test their cutting ability without spending time working on handles and guards.  

I performed three thermal cycles after forging, and then heated the blade a little past nonmagnetic and quenched in motor oil. ( I know motor oil is not the best.).  The oil was about 100 degrees when I quenched.   My triangle file cut about .010 to .015 into the edge.  My concern about over heating is due to the fact I'm using an old Buffalo forge and my fire may be to shallow.  About 2 or 3 inches from the air vent. I may have an oxidizing fire. Thanks for the help.   

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The top picture is the spring material.  I heated it past nonmagnetic and quenched in water.  It snapped off and a file would dig a little on the outside but not at all on the inside.  

The second picture is the knife itself.  It snapped like glass and has a coarse grain structure.  The outside material still grabs the file.  I dropped that knife, point down, three times onto concrete and it didn't even break the tip after the water quench.  Lol.  Again thank you for all the help and advice.  

IMG_20210304_181524852.jpg

IMG_20210304_181543575.jpg

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REgardless, it's a lousy way to test hardened steel. 

What does the break in the blade tell YOU? 

Bearing in mind I am NOT a bladesmith I just blacksmith. I see an enlarged crystal structure (grain growth) making for a brittle piece of steel. REgardless of what is made from it. Test coupons made before you spent all that time would've told you your heat treat method was bad BEFORE you wasted all that time. Hmmm?

Evaluating found steels has been discussed by folk who KNOW what they're talking about more than once here. Keep that blade AFTER you "temper" it so it's safe and put it on the wall so you'll be able to SEE how far you've come at a later date.

Judging from your posts you spent WAY too long with it above critical without refining the grain under the hammer and used urban myth heat treatment methods. 

My advice is: Learn to blacksmith BEFORE spending so much time and effort on blades. Once you've mastered the basics a blade is just another product that requires a LITTLE more specialized heat management and heat treatment. Once you have a good handle on the basics, blades aren't a big deal to get right.

The bladesmithing lessons and sessions on Iforge are hosted and evaluated by published authors. They're spent valuable time and effort to help folks make blades properly. Hmmm?

I'm just a guy who knows my basics. I don't make blades but I know enough to pull it off with a little evaluation of MY technique and heat management. Say a couple maybe three tries BEFORE I made a blade.

We WANT you to make beautiful blades and post pics here. We LOVE pics and the more beautiful the blades the better.

Frosty The Lucky.

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Hey there buddy. Top notch advice from Frosty, heed it.

In my life experience(s), whether it be guns, knives, winemaking, woodworking, women, etc. etc., When dealing with raw goods or materials, one should start out with quality. Why? quality is the one thing we all should strive for, and it is extremely difficult to start out with something of low quality - especially when starting out anew as a craftsman, and improving the quality while crafting it into something of value. This is what separates the pros. 

In other words, if you are going to make a knife, get the extra pennies out, and spend for the appropriate level of quality steel to make the knife. At the end of the day, you wont end up with a piece of garbage, because unfortunately until you become a master craftsman, you slowly chip away at the quality of the material if you don't know exactly what you are doing.

-- And yes, I completely get this as well, "well I don't have a lot of money to spend on this and I want to do it on the cheap".... My response to this is, it isn't that much more expensive to spend a little bit to get much more, and we can all go without other extravagances in order to buy good steel to begin a project that you care about. Now if you just want to practice moving metal around, by all means use scrap. A piece of 440 stainless about 18 inches long 2 inches wide 5/32, new material of known composition, can be had for under $50. That will make a good number of blades. If that is still to spendy, check sources like certain online bidding sites where you can buy less of same in a kit form.

 

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Thanks for the help guys.  I agree with you about the new steel.  I have some 5160 and some 1080.  I have been practicing my forging skills with old coil spring and leaf spring so I don't waste my good steel.   

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9 hours ago, Apple Duck said:

well I don't have a lot of money to spend on this and I want to do it on the cheap

Nice response all round but the above brought something to mind that has bee around I don't know how long but is as true of learning as it is of anything.

Cheap, Fast, Good. Pick two. You can NOT learn quickly on the cheap and be good. You most certainly pick to NOT require all three. Take your time, only spend what you must and get VERY good. 

Cheap and take your time is why I recommend learning with low carbon, it's inexpensive so fails don't hurt so much. It moves more easily so you can develop hammer control before you really have to HIT IT. Make KSOs a really classy letter opener doesn't have to hold an edge so you can forget about heat management and heat treatment but you can dress is any way you like. Nice letter openers make great gifts and even sell.

Frosty The Lucky.

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I used to go to a place that made replacement car springs and buy their drops---the ends of known good stock they had left over. IIRC I was spending US$1 a pound for them. I bet you have spent enough time on that project that you could have shoveled snow or mowed lawns and bought enough known good steel to last you a year.  When folks say they can't afford to buy proper materials; but can waste hours or days of their time working with subpar stuff, I get to wondering...

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