Cold forging

I am working on my first project: a cutting knife for my mother. I am going for something that resembles this:
http://www.geocities.com/soatoz/hamo...saku_Tama1.jpg

I have a piece of O1 that I annealed and cut to size.
I experimented a bit, and discovered that it is soft enough to shape with a 2,5lb hammer without heating it.
Granted, I have to file away as well, and the shaping goes slow, but I actually like being able to work on that piece for 15 minutes when I have time and then put it away again without having to fire up the bbq.

My main concern is: does this have a negative effect on the steel in some way?

This is the forging equivalent of fixing thebigspendur's nasty warped razor with a Belgian blue... :)

As long as the steel is soft enough, I think you should be OK. Cold forging is a legit technique, from what I understand. It probably imparts stresses as you go, but you should do a stress-relief treatment before you harden it, anyway. (Grinding also stresses the steel, and it's not a big problem as long as you deal with it.) It might be a good idea to re-anneal it every once in a while to minimize the stress build up.

When you read about forging too cold, usually that means while the steel is hot but in the black range. There's a range where steel is "blue brittle"--I think that's the term. It's roughly between 400 and 800 degrees F. You can crack the blade if you hit it in that range.

At room temperature, it's pretty ductile, so you should be fine. The nice thing is you'll have plenty of time to correct mistakes. :)

Josh

No you can not cold forge a blade. The stress will shatter it when heat treating starts. I find O1 to forge terribly, I stick with simple high carbon steels W1 is a good one and comes in many shapes, it works and treats like 1095. Cold forging a blade steel is not a good idea at all.

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Originally Posted by Twalsh341

No you can not cold forge a blade. The stress will shatter it when heat treating starts. I find O1 to forge terribly, I stick with simple high carbon steels W1 is a good one and comes in many shapes, it works and treats like 1095. Cold forging a blade steel is not a good idea at all.

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Well, I guess we should all throw our O1 in the trash, since it comes from the mill after being cold-rolled to shape. That's cold forging, my friends. What's going to impart more stress, a 2 lb. ballpeen hammer or hundred-ton presses forcing the steel ever thinner? :thinking:

Dealing with stress is a everyday part of making knives and razors. A simple normalizing routine will relieve any stresses that build up due to cold-forging, hot forging, grinding, machining...

A blade that is hot-forged at too low a temperature will develop stress cracks that will show up later when you heat-treat the blade. W1 is notorious for this.

O1 is a little stiffer under the hammer, but it moves well once you get it hot enough. The only reason I'm not forging blades from it is that it can be hard to drill after forging. Otherwise, it's great to work with.

Josh

I found that one end of the O1 was soft enough to use my files with ease, so atm I am trying to see how far that'll take me.

The advice about sticking to simple steels is well taken. I would disagree about forging O-1 though. I routinely reduce 1.5-2.0 round bar down to flat because it's a lot cheaper than buying flat bar. Never had a problem with any of the O-1 after the heavy work. Fascinatingly, even W-1 is considered a cold-working steel in the books I'm reading along with a bunch of others that might surprise folks.

O-1 will work harden when cold forged and that effect needs to be accounted for. As Josh mentions, he found out that it doesn't take much to harden it. It'll even air harden if you have a fan blowing nearby. It'll need to be annealed again, but that's not difficult.

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Originally Posted by JoshEarl

The only reason I'm not forging blades from it is that it can be hard to drill after forging. Otherwise, it's great to work with.

Josh

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Thats because O1 needs some interesting annealing cycles after its been worked above critical to reduce the grin size and carbide structures to soften it.

I'm not saying to trash all the O1 I love it for punches etc. there are just some ways you should handle a piece of steel. Risking developing fractures in a cold rolled steel, which has decreased ductility, doesn't make any sense to me.

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Originally Posted by Twalsh341

Thats because O1 needs some interesting annealing cycles after its been worked above critical to reduce the grin size and carbide structures to soften it.

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You've made a link between annealing and grain reduction that should be explained, please.

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Originally Posted by Twalsh341

Thats because O1 needs some interesting annealing cycles after its been worked above critical to reduce the grin size and carbide structures to soften it.

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Yeah, I don't have the equipment to spherodize anneal. O1 will be a stock removal steel for me. :)

Josh

When a metal is worked the grain structure is distorted, gaps form in the lattice, these stresses are what can cause a steel to break of develop fractures when quenching. Normalizing is letting a steel air cool after reaching CT, a full anneal is achieved when a steel is brought to the CT and cooled to a specific temperature at a certain rate.
When annealing the steel goes through several phases the first phase the defects are removed from the steel (dislocated atoms), then the grain structure redevelops. After this spherodizing occurs and the metal may become too soft for certain applications. O1 needs to be spherodized to machine easily after being worked.
When martensite is tempered or austenite cooled a laminated structure called pearlite is formed. Pearlite is layers of ferric carbide, a very hard material; which impairs machining and reduces ductility. Simply heating O1 to above critical and normalizing it allows the carbide to form and will not be sufficiently annealed. Further cold work of the steel will develop micro-fractures that can break it in the quench; or make it impossible to drill.

I'll be more specific.

How does the annealing process remove the defects? Why doesn't normalizing do the same thing as annealing?

When a steel is annealed, how does grain reduction occur?

If pearlite is layers of ferric carbide, a very hard material, why is pearlite softer than martensite?

The added energy allows the molecules of the steel to start moving by breaking the bonds of the steel. Normalizing is a shorter lower energy process (energy is only added for the 10 minutes or so it takes to heat the blade) whereas a full anneal adds energy to the steel for hours.

When annealed the grain realigns, and the pearlite transforms from its lamellar state into globs(spheroidizes). The amount of heat is what allows the atoms to rearrange. Pearlite forms when austenite is cooled slowly, martensite when cooled rapidly; martensite forms cutting edges. pearlite is part of annealed steel and forms in small sizes in tempered martensite.

I was hoping you'd be more specific. I was under the impression that spherodizing was a very specific application of heat (energy) to a specific point for a set amount of time and that carbides (cementite) spherodized in a ferrite matrix because of those specific conditions. Something along those lines.

I apologize for being repetitious: bainite forms from austenite, not martensite. I suppose that tempering any retained austenite has a chance of producing bainite but given the speed at which martensite forms, I'd estimate that chance as pretty slim without very tight thermal controls over time. If the heat treatment cycle was not precise, bainite could be found intermixed with martensite, but would likely to have formed first rather than secondarily. Bainite is a decomposition phase from austenite.

Do you want to know what geometric stricture turns into what? thats as more specific as it gets.

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Originally Posted by Twalsh341

Do you want to know what geometric stricture turns into what? thats as more specific as it gets.

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No, I'm back to my other questions. Please explain how, according to your assertion that pearlite is "layers of ferric carbide, a very hard material," and why pearlite is softer than martensite? This is a contradictory statement and I'm asking you to clarify the contradiction.

I'm pointing out the contradictory statements and asking for factual resolutions of the contradictions. I have no wish to put any one person "on the spot."

This is about information, not a person, that is not valid, clear and precise. Folks come to this forum to learn the right ways of doing things so they can make better razors/blades or understand claims made about how sharp steel items were manufactured. There may be many different ways to skin the cat, but they are not contradictory. It is not for you, or me, to propagate myths or magic or misunderstandings in this place.

I'm asking questions because I want to understand what you understand. It is possible that I don't know something and I'm actively correcting my mistakes as I go. But when I find a contradiction, I want to also know where the difficulty began and where it got off track, so I don't make a similar mistake in my thinking. Then I can reset my known starting point and keep moving from a solid foundation. If I would make a contradictory claim and someone here heat treated a blade that was then ruined or failed in the hard world of the customer's parlor, my credibility would suffer. I have no wish to have that happen to anyone. :)

I'm letting go of my end of this conversation because these things can be uncomfortable for everyone. But I've made my point.

I understand better where you are coming from, I apologize for anything uncomfortable I may have said.

Back to the pearlite...
Pearlite is a layered structure of ferrite and cementite. Cementite is iron carbide. Cementite forms at two different times, during the cooling of austenite, and during the tempering of martensite. The cementite forms pearlite or bainite when it layers with ferrite at different temperatures. The carbides in cementite provide the hardness, while the ferrite (basically pure iron with very little dissolved iron) is tougher.

True damascus has been speculated to be visible grains of carbide and ferrite forged into patterns. Today we still don't know how such large layers of cementite and ferrite were made, possibly with alloying elements that increase the size of the grain structure.

I suppose martensite and cementite have similar strength/brittleness, however the cementite when laminated with ferrite is less brittle than a fully martensitic steel.

More thoughts on ferrite/cementite and Silver Steel

When austenite is formed at the CT the amount of carbon in the structure is about .8%. Silver steel has a carbon content of about 1-1.2% I need to do further research, but I believe the excess carbon atoms form more carbide, producing a higher carbide to ferrite ratio id est a harder steel. As mentioned I need to research this further, but that seems like a plausible explanation of Silver Steel's extreme hardness.

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Originally Posted by Twalsh341

... True damascus has been speculated to be visible grains of carbide and ferrite forged into patterns. Today we still don't know how such large layers of cementite and ferrite were made, possibly with alloying elements that increase the size of the grain structure. ...

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I was really prepared to let this go. But it seems that understanding of my request for clear and correct information remains elusive to you.

Read this article and any associated articles you want to search for by Dr. Verhoeven. Please.

The Key Role of Impurities in Ancient Damascus Steel Blades

Dr. Verhoven specifically mentions vanadium as an alloying element in wootz, aka original damascus steel. Vanadium should be well known to any metallurgist as a grain refining alloying element, NOT something that increases the size of the grain structure.

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Originally Posted by Twalsh341

I understand better where you are coming from, I apologize for anything uncomfortable I may have said.

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No apology is necessary. I would ask you to take the same care in your answers as I do.

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Back to the pearlite...
Pearlite is a layered structure of ferrite and cementite. Cementite is iron carbide. Cementite forms at two different times, during the cooling of austenite, and during the tempering of martensite. The cementite forms pearlite or bainite when it layers with ferrite at different temperatures. The carbides in cementite provide the hardness, while the ferrite (basically pure iron with very little dissolved iron) is tougher.

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What are the specific conditions for cementite to form in martensite? If you can answer this, you'll have answered part of your own thought about Silver Steel. I can live with the idea that pearlite is a lamellar structure with alternating ferrite and cementite, but how does cementite form into bainite? Isn't cementite a single phase crystal?

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More thoughts on ferrite/cementite and Silver Steel
When austenite is formed at the CT the amount of carbon in the structure is about .8%. Silver steel has a carbon content of about 1-1.2% I need to do further research, but I believe the excess carbon atoms form more carbide, producing a higher carbide to ferrite ratio id est a harder steel. As mentioned I need to research this further, but that seems like a plausible explanation of Silver Steel's extreme hardness.

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I'm curious as to how the subject has now been changed to include ancient damascus and silver steel which were not parts of the original discussion. They are pleasant distractions however and two of my favorite metals.

All that excess carbon (I think you mean hypereutectoid steel) has to go somewhere. But then that leads to another way of forming the specific carbide that you're speaking of. And, if we are speaking of a carbon steel like this, when raised to the CT and quenched, since you speak of extreme hardness, that requires a quench, where does the ferrite come from in that phase? Shouldn't it all be martensitic with other components?

I do agree that more research is needed. I think your understanding is a little off. What are the references that you're using anyway?