Are Folded Steels Stronger?

N

Nodestar

Joined
May 16, 2007
Messages
16
This question has a couple parts to it so bare with me as I try to explain what I mean.

In regard to Japanese Swords made in the traditional manner I've heard that folding was required to remove any impurities in the steel. Also modern day Japanese swords made with various steels 1095, 1060, etc. Will normally be folded a few times perhaps simply to make the blade more harmonious. But modern Japanese Swords made of a single pure steel. Say 1095 will not have any foldes.

So does folding a blade make it stronger? Whether or not it is composed of different materials and is Forge Folded (or Forge Welded) or not. Or does folding a blade do nothing for strength?

A final note. I'm not really talking strickly about Japanese blades but rather all blades. Useing Japanese blades as examples was the easiest way I could get my points and questions across.
 
Forge welding will not make modern steels stronger, done properly you won't notice a difference between folded and non-folded steels. However, if done improperly, folded steels can be much weaker because of things such as inclusions and delaminations. At least that's how I've come to understand it.
 
Folding will also not remove impurities. It might spread them out some and make a large impurity into many smaller impurities. The thing about modern steels is that they are usually made with a vacuum degas process that removes most of the impurities. Todays modern steels are vastly superior to steels of just 20 years ago.

The cleanest steel you could probably use is 52100 bearing steel. This steel is always made with a vacuum degas process and is the cleanest steel on the market today.
 
How about this? Why were japanese swords folded back in the day? What purpose did it serve back then?
 
Nodestar said:
So in short. Unless your are forgewelding Damascus there is no reason to fold steel?
Click to expand...

YES

now not saing that a blade smith cant make a great blade by forge welding but for the most part you dont need to fold over steel to "make it good "
 
stingray4540 said:
How about this? Why were japanese swords folded back in the day? What purpose did it serve back then?
Click to expand...

scottickes said:
Folding will also not remove impurities. It might spread them out some and make a large impurity into many smaller impurities. The thing about modern steels is that they are usually made with a vacuum degas process that removes most of the impurities. Todays modern steels are vastly superior to steels of just 20 years ago.

The cleanest steel you could probably use is 52100 bearing steel. This steel is always made with a vacuum degas process and is the cleanest steel on the market today.
Click to expand...

That's already been answered
 
stingray4540 said:
How about this? Why were japanese swords folded back in the day? What purpose did it serve back then?
Click to expand...

back then you could not get a good batch of ALLOY you hadb to smelt it and work it down to "good working blade steel " the foldingn was to make the steel as homomogenas (sp) as it could be to make a good blade
 
reading a historical website on traditional japanese smelting methods, they built up a big chimney with bellows at the base and layered charcoal and crushed ore up the chimney (turure?) lit it at the base and pumped air up it. Instead of melting and running out the base as in a blast furnace the iron formed spoungy masses inside. these then got forged into pancake shaped lumps. depending on where in the furnace they were they had higher or lower amounts of iron in them, and the japanese smiths would break those up and sort them into piles of generally similiar lumps, then start forging them together, and folding, and forging untill the bar that would form the blade was as homogenous as possible. this also decarbonised the billets to an extent during the protracted forging process reducing brittle high carbon iron (6 to 3%) to lower carbon steels (1 to .8%).
Western methods at a similar stage of iron technology was to use a proportionally taller and narrower chimney shape and the iron would melt and run out the bottom into pigs. hence the term pig iron.

mind you, take this with a grain of salt since I got this off the 'net and it's filtered through a rather defective/selective memory) :D
 
In a modern steel, folding can not compete with particle metals technology and the processes Scott mentioned.

In the ancient days folding homogenized the steel into a more even carbon content and a better purity. The blades from The Middle East and Japan were folded and refolded until the result was a near-monosteel with a super fine grain (called Hada in Japan, Damascene in the Middle East). These blades were stronger and more flexible than simple steel blades. The presence of small amounts of Vanadium, Cobalt, Chromium, and other alloy elements was a probable reason for some of the hardness features. The makers didn't necessarily know that the alloying elements were there. They were in the ore gathered at "secret" mines and other sources. Some have even suggested meteorites as a source of the alloys. Meteorites were quite serious religious objects in the Islamic world ,as well as in the Orient.
Good steel was just about as valuable as gold, and in battle was much more useful.
Stacy
 
Jared Stenoien said:
Considering he works at Timkens, and they use it a lot, he's probably his own source. :)
Click to expand...

Yep, shoulda read the profile. So its cleaner than M2 and other tool steels and high temperature bearing steels?

On topic of the thread, I've heard it argued for years that pattern welded steels and folded steels were tougher/stronger, but that they werent used by industry because of cost. Knowing that the P/M steels, vacuum processes and such were out there, the arguements were just convincing enough to consider, until I saw the article about the guy that had a home made rolling mill he used to make patternwelded damascus and then met another guy at a flea market in NC that claimed he had made one too. It just seems if there was that great an improvement, then someone would figure out how to do it cheap enough to make it practical, and reap the monetary benefits of such processing. To my knowledge, there have been no independent tests comparing strength of patternwelded or folded steels to other steels. Of course, I havent looked in about 5 years, so it may be there.
 
me2 said:
....To my knowledge, there have been no independent tests comparing strength of patternwelded or folded steels to other steels. Of course, I havent looked in about 5 years, so it may be there.
Click to expand...

;) well...

One of the problems with comparing strength/toughness in pattern welding and homogenous steel is all the darned variables that get thrown at you with the creation of the pattern welding. Any differences I have seen can be chalked up to fresh inclusions added in the welding, decarb, and other unforeseen effects. Some have claimed that they experience a greater toughness in folded steel, assuming that it is the same steel welded to itself (lets face it, vary the alloys and the possibilities and variables will go off the scale), extended times at welding temperatures with the exposed surfaces being folded back into the mix, it would be naive to attmept chalk a change in toughness vs. strength to any mysterious mechanical effect when the real culprit should be a no-brainer.
 
So folding has it's uses in the distribution of alloys and possibly carbon when useing different but similar steels? Such as 1084 and 15n20. I've heard 15n20 was made from 1075. So with enough folds the carbon might redistribute into a more homogenized blade. Making a more distributed carbon content somewhat lower than 1084 and higher than 1075? And this might be the same with the alloys in the steel? Or even if that does not occur would anyone agree or disagree that spreading the small amounts of alloys throughout the blade more finely might yield better... somthing..
I know very little on the subject. Any information would be great. And everything I said above is a question not a statement.
 
Your getting the idea, but have a little reading to do yet. 15N20 is basically 1075 with 2% nickel. It is not made from 1075, but is similar composition, plus nickel.
There is a certain amount of carbon migration when folding and forging, but the real benefit is the homogenization of the mix, by fine layering. Take two colors of clay and a rolling pin. Place them in a stack, fold,roll,fold,roll, The colors start to blend. The clay sheet is still two colors, but the mix gets so fine that the color becomes a uniform single color.

( NOTE: The following examples are exclusive of the real world problems of oxidation and other process related effects of hammering metal at high heats for a long time.)
If you take 1084 and 15N20 and fold them to 100 layers,there will be a bold dark/bright striping. At 500 layers there will be a very fine bright stripe between each darker layer (use a magnifying glass). At 1000 layers it will just look like a fine grain with a sheen to it. At 5000 it will be appear to be a monosteel with .8% carbon and 1% nickel. If you took a micrograph, you would still see the grain, though.
So you would seem to have decreased the 1084 to .8% carbon, raised the 15N20 to .8% carbon, and re-distributed the nickel evenly throughout the mix, but you didn't.

Now, you could actually remix the alloy if you melted the two original steels and repoured it. You would get .8% carbon and 1% nickel.

The assay is the same, but the two bars of steel will not be identical. Some would take the bar of 5000 layer steel and others would take the alloyed bar. For as sword or knife, I would rather have the folded bar. There is less chance of a weak spot, flaw in the steel melt, or other factory related problem. If the source of the steel bar was not well known, or inferior, the folded bar would be far more reliable. Which is stronger - It is hard to say. Which would I take into battle - It is easy to say.
Stacy
 
correct me if i am wrong but if the "grain" of the layers is perpendicular to the blade itself the wearing away of the steels would be slightly different thus giving micro serrations? maybe?

-matt
 
bladsmth said:
( NOTE: The following examples are exclusive of the real world problems of oxidation and other process related effects of hammering metal at high heats for a long time.)
Click to expand...

I would like to know about these real world problems. When and why does Oxidation occur. And what problems are faced when making several thousand layers over several days?

I'm also wondering... if these steels were folded so manytimes and so close to becoming one. Then how would that affect heat treating. Would it make two steels that would normally not go good togeather because of different heat treating fall under the same heat treatment within the context of the folded blade. For example and with no practical purpose you made a billet of 1095 and 1018 and the carbon content came closer to say.. 1075. Would you heat treat the blade at 1095 or 1075 temperatures?
 
from my understanding (i could be wrong and i know i will be corrected if i am) but most oxidation on folding steels is in the forge from improper flux and/or incorrect flames (gas rich vs oxy rich)

leaving steels out for a few days shouldn't do much unless you have it in a corrosive environment from my understanding
-matt
 
You must log in or register to reply here.
Back
Top