reducing grain growth

[JHCC]

For a really great overview of grain formation in metal, here's a lovey old informational film from the BBC:

 

[J Hiser]

I was under the impression annealing was more complicated than that. Guess I’ll be doing some more reading. Thanks for the info and the references to check out.

[Deimos]

Thank you for posting that video JHCC, very informative. 

To think people in the olden days knew about this by trail and error without knowing the science behind it.

[JHCC]

They didn't always, or they did the right things for the wrong reasons. For example, there's the myth of "edge packing", where blades would be would be heated to barely glowing and then lightly hammered on the edges, on the theory that this would compress the metal and make it tougher. Well, the rationale is nonsense, because steel is non-compressible. However, the thermal cycling could have a normalizing effect if the temperatures were right, and so the practice continued even though the hammering part was irrelevant and unnecessary.

[Deimos]

I did not know off this myth, but I do know there are tons of myths still present today that a lot of people still believe. Even tough science has proven otherwise.

I was more thinking in the line of just finding out how metal behaves when it is heated, cooled and hammered. And that there are still things we know of today but cannot recreate. 

[ThomasPowers]

John, don't forget that creating lots of dislocations in the crystalline structure by forging also works to create a new smaller grain structure when next heated---like for hardening *after* edge packing.  Early alloys profited a lot from the forging to decrease grain size as alloying wasn't as good.

[JHCC]

13 minutes ago, Deimos said:

And that there are still things we know of today but cannot recreate. 

Such as?

 

1 minute ago, ThomasPowers said:

creating lots of dislocations in the crystalline structure by forging also works to create a new smaller grain structure when next heated

True, but again, an unintended consequence of a procedure done for other reasons.

[Deimos]

Roman concrete and I have also heard some things about true Damascus being different then what we now call Damascus pattern, but I have not yet read up on that.

[ThomasPowers]

Actually the term "Damascus" has been used for two different materials for longer than the USA has been around.  They are: Wootz which is made by melting a special mix of materials and slow cooled and then thermocycled to get large sheafs of carbides that provide the pattern, AKA "true Damascus or crystalline Damascus and is a subset of crucible steel. The other form is Pattern Welding, where differing pieces of steel are forge welded together. There are a few examples where both materials was used in a single blade.

 

[Frosty]

Roman concrete was so hit and miss in the day, virtually every attempt to "recreate" the process is successful for somewhere in the Roman Empire. Concrete goes back way farther than Rome, many structures in Ancient Greek sites are made with concrete, especially docks and break waters. 

A lot of processes used for working iron and steel were done knowingly. Just because you can't see or measure on a molecular level doesn't mean you don't know the effects of a process. Edge packing is more effective with wrought iron blades as it breaks up the silica inclusions and reduces the size of crystal boundaries. 

This happens to a lesser degree with steel. Commonly called "grain growth" crystal size has a direct effect on embrittlement, the larger the crystal structures the more brittle. Like on the macro scale, every connection is a stress riser, a failure initiation point. The smaller the crystals, the smaller and more dispersed the stress risers. Hammering cooling steel can crush the crystals while aligning them making a less brittle but work hardened edge. Far from perfect and not effective on modern alloys. 

Damascus is a City made famous for being THE place to buy high quality steel. As Thomas describes steel made in such a way as to have a pattern. Pattern welding is a natural outgrowth as Wootz steel wasn't terribly controllable carbon content wise so welding more than one billet together made a more homogenous steel and humans being human wanted a gimmick to make THEIR steel/blades, etc. special and developed trademark patterns. 

Frosty The Lucky.

 

[JHCC]

3 minutes ago, Frosty said:

Roman concrete was so hit and miss in the day, virtually every attempt to "recreate" the process is successful for somewhere in the Roman Empire.

It also has to be remembered that high-quality concrete has a greater chance of long-term survival, while low-quality is more likely to crumble and get replaced. To be sure, the specific characteristics of the limestone and volcanic ash that went into ancient concrete structures in Rome itself and its environs generally produced an extremely durable product, but we shouldn't judge ALL Roman concrete by the remnants that were stronger than the forces placed on them over time -- that is, either environmental stresses and the wear of use, or simply getting torn down because they were in the way of something else that a later Roman wanted to build.

[ThomasPowers]

Except Pattern Welding came first as it's a natural out growth of working with real wrought iron where you stack and forge weld blooms/ muck bars to get larger pieces of iron and by repeating, less and more finely divided ferrous silicates. 

The intermediate stage, simple stacking AKA "piling", was known by both the Romans and the Celts for blades and the Celts were definitely selecting for harder edge materials in their blades. (Not always successfully..."The Celtic Sword", Radomir Pleiner)

Getting refractories that will take molten iron was a major problem; not to mention having ores with the correct carbide forming elements in them naturally so Wootz seems to have a more limited area of production in Central Asia, Merv for instance.  ("Crucible Steel in Central Asia", Doctoral Thesis of  Dr Ann Feuerbach)

There is a whole lot of BAD info on Wootz and Pattern Welding out there.  I like the Urban Legend that Europeans were introduced to Wootz in the Crusades and went home and came up with pattern welding when they tried to figure out how to reproduce it!  I've heard that one a lot! Nice story; but the early hay day of Pattern welding in western Europe was *centuries* before the first crusade. (500's and 600's AD with it's use dying out around 1000 vs the first crusade starting 1096. "The Sword in Anglo-Saxon England, H.R. Ellis Davidson) and there is a continuous record going from piling to pattern welding to monosteel swords. ("The Sword and the Crucible", Alan Williams)

(yup got the books and thesis in my book shelf...)

[Deimos]

Frosty, I understand that they could see/test what the effect was of different methods, its how they came to those methods that I find amazing.

From what I have read/heard is that ancient concrete main difference against modern concrete is its resistance against salt water. And indeed, we would never know if the old civilizations made some bad version, since it would have crumbled away already.

Thomas, thanks for all that extra information and for ruining the internet even more , its pretty hard to find the truth among the myths if you are just starting to learn about all this stuff.

[JHCC]

One nice thing about IFI is that we tend to rely a bit more on peer-reviewed studies than on myths that "everybody knows".

[Deimos]

And that everyone who knows something about a subject just chimes in. I wish the Dutch blacksmithing forum was as active as IFI, it really feels like all craft is dying out over here. And with it tons of knowledge. 

[Frosty]

Ah, I liked that myth about pattern welded blades in the west too. Spoil sport. I forget what was the alloying metal in the original iron ores that gave Damascus such good properties. one of my voice keeps saying manganese but the others just laugh.

Deimos: What makes  you think modern concrete doesn't hold up in salt water? The only modern concrete that doesn't do well is "high early" type III it sets much faster than type I or II and is popular for things that need to be poured and go to work quickly like sidewalks. 

If you want concrete specifically for,  intermittent salt water immersion you spec type V. Even regular concrete kept completely submerged lasts centuries, it's wetting and drying in a salt environment that degrades concrete, the surface is permeable and when it dries salt crystals break it up a few thousandths at a time, any cracks really accelerate the effect. The wet and dry cycle is why it's not good for any concrete to use sodium chloride salt for a deicer. Calcium chloride causes minimal damage and magnesium chloride does none but it's sticky and gets on everything. 

We used a lot of salt and less corrosive deicers working for road maintenance, there were even classes during my soils lab days.

Frosty The Lucky.

[Deimos]

grumble grumble, everything I know is wrong then. I heard that theory on some history show/channel years back about the properties of ancient vs new concrete. 

[ThomasPowers]

It's been remarked that Americans are often very free with sharing information.  Some people think it was due to the lack of the Guild System here in America.  Well we did start with one but it died off fairly quickly especially out on the frontier where there there wasn't the population density to have people confined to separate areas of craft.  The Jack of ALL Trades is a very American thing. 

Of course a lot of us know "information hoarding" folks at work.  People thinking that if they are the only person who knows how to do a particular job then they have more employment security.  I lucked out and my first 14 years was with Bell Labs. it had an "information sharing" culture.  Or as one Engineer told me:  "I don't want to be the only guy they can call at 3 am because there is a problem overseas!"

[Deimos]

Over here old timers have to be "forced" to educate the new generation (and since companies have no idea how long that takes they start doing this 2 months before someone has his retirement).

I have left more then one company because to many people refused to teach me new things, just to keep their own job "safe". On the Dutch blacksmithing forum I heard one blacksmith say "Real blacksmiths are more busy doing blacksmithing stuff instead of talking about it". Great way to motive the young ones... 

Its very rare to find people here that really WANT to teach someone something, either you pay hard cash for it ($1000 to $2000 for a few days is nothing) or they just take their knowledge to the grave.

[Frosty]

Sorry, I think I saw that one or one like it too. Did it have the medieval stone tower the Germans had to shoot more than half a dozen times before it broke and a big section of the top is still laying in tact on the ground after falling something like 70'? There are some examples of lime mortar that are way stronger than the native stone.

There are current living history projects building historic and prehistoric structures using period technology. One of the education channels had quite a special about building a section of Roman aqueduct using Roman concrete. The reenactor in charge of Roman concrete talked about how hit and miss getting good concrete was until they'd been working at it a while. Then they realized there were detailed instructions including how to select material, evaluate and adjust the mix. 

Step one build a big fire in the iron mixing tub, two toss in the right amount of broken limestone, when the smoke burns the skin cover with ash and allow to cool. Mix thoroughly and add water, add gravel until the right consistency and fill the forms. 

Making concrete the Roman way was hard work, exciting and dangerous. Mixing water and large quantities of quick lime rapidly comes to a boil and is really caustic. Makes good concrete though. 

One of the things I really like here is the free flow of information and how quickly folks point out when I get something wrong. A day doesn't go by I don't learn something. Even if it's to just keep my mouth shut. (fingers off keys)

About folk keeping secrets, it's a sure sign of insecurity. Being the best or only one who can . . . doesn't compare to being the guy who can do many valuable things. My folks drummed a few important things into us. "Always have a fall back" has stood me in good stead my whole life. They generally meant a fall back trade incase this job closes it's easier to find another. I collected crafts and trades to a point I had a good handle on the basics. It made it easy to teach me a new job so I was farther down the list than the specialists when layoff times came.

Seriously, what do you do with a one trick pony when the trick no longer sells? 

Frosty The Lucky.

[JHCC]

40 minutes ago, Frosty said:

I forget what was the alloying metal in the original iron ores that gave Damascus such good properties. one of my voice keeps saying manganese but the others just laugh

If memory serves, Pendray and Verhoeven demonstrated that it was trace amounts of vanadium that made the difference. 

45 minutes ago, Frosty said:

Even regular concrete kept completely submerged lasts centuries, it's wetting and drying in a salt environment that degrades concrete

Plus any salt that gets inside far enough to corrode steel or iron rebar.

17 minutes ago, Frosty said:

what do you do with a one trick pony when the trick no longer sells? 

Make glue!

[Deimos]

I fail to remember seeing them shoot a tower, but I do remember some grayish man telling about the roman/Greek stuff on location. Since I am horrible with remembering when I saw things it could have been 15 years ago or longer.

The constant stream of information is what keep me coming back as well, interacting with people is pretty exhausting for me (internet makes it easier but the autism still proves a problem on some days) but even when I am just lurking I find myself making mental notes about things other people found out or talked about.

The funny thing is that most of the time I was the guy who could do 90% of all the tasks in a company, some of them as good as people with 10+ years more experience than me. People hated that I can learn anything 10 to 20 times faster then they can. And as soon as I get to the level they got after years and years of working kept growing and getting better.

Fallback skills are very important, the problem here is that being a "jack of all trades" is frowned upon, it just means you don't know what you want and are rubbish at everything you do, else you would just do the same skill for over 40 years... Imagine how I get treated with 4 diploma's and 21 certificates 

On trick ponies can be made into a really nice sausage 

[Frosty]

No they didn't shoot the tower in the special, the German Army did that in WWII and used armor piercing rounds. They showed it in the special to show how strong lime mortar could be. In close ups they showed how the stone broke rather than the mortar.

Yes, vanadium! The other voices were right laughing at manganese. I sure wish they'd just speak up instead of holding out hoping I'll embarrass myself . . . AGAIN!

Oh yeah, Galvanized or and coated rebar was coming into use a couple years after I transferred to the geology section to make holes in things. 

Ayup: glue, sausage, dog food, etc. Bingo that.

Frosty The Lucky.

[JHCC]

I think there was also something somewhere about how the Wootz-makers knew that they got the properties they wanted when they used the ore from one particular area, this being the stuff that had the trace amounts of vanadium. This desirability made that area a hotly contested prize of war, even though the specific chemical composition wasn't identified until centuries later. I'll have to see if I can track that down.

[ThomasPowers]

And there is some suppositions that the use of wootz disappeared when the mine(s) with the right alloy mix played out.

The thing that Verhoeven figured out was it was traces of vanadium; so low they are usually ignored as part of the "trash" in the analysis, that made all the difference!  (I volunteered to be Pendray's helper at Quad-State the year he did a demo there; best location in the house and able to ask him any questions I wanted to!)