Does rolling direction matter?

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skillgannon

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Apr 27, 2009
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Just bought a 15.75" X 48" piece of 1084. I'm just doing stock removal. Does rolling direction matter?
 
Since I have never known which direction my steel was rolled I'm thinking no? However I always work from sticks, not sheets and it may be standard to cut them in the direction of the roll.
 
This question came up a short time ago on another forum, and I quickly replied that it didn't make a difference. A man by the name of Kevin Cashen chimed in a short time later to tell me I was wrong, and it actually can make a difference. He started using big words to explain it, and I followed most of it. The main thing is that it can make a difference. I also doubt that many end-users would notice the difference. He also said it was less of an issue in powder metallurgy steels.
 
In steels used in construction, it does matter. There are inclusions in the steel that get stretched out in layers in the direction of rolling, almost like layers of damascus. Apply stresses perpendicular to the inclusions and the steel has reduced toughness. (This is called "lamellar tearing".)
I would guess that the manufacturing process for the finer grade of steels that are used in tools and knives would reduce the layers of inclusions.
I agree with the people that say they didn't know what direction their steel was rolled so by chance they probably ground blades the wrong way. Maybe for the better steels it doesn't matter.
 
All steel starts as a hot-rolled product. Some goes on to be cold-rolled after that. Many of these cold-rolling processes are done to refine surface finish or improve flatness rather than work the steel into new dimensions.

I don't think the direction of superficial cold-rolling is important, but I think the direction of the hot-rolling is important.

Without a doubt, grain direction is very important in general metalworking. (For example, you can cold-bend 6061 aluminum against the grain, but not with the grain or else it will crack).

The topic is well documented and explored in the realm of industrial forging. "Grain flow" is the term used there - as an example http://www.farinia.com/forge/cold-forging/cold-forging-hot-forging-benefits-and-drawbacks

Recently I asked a reseller what the grain direction was. The reply I received was "There is no grain direction, because this steel is cross-rolled." More on that topic here http://www.eng-tips.com/viewthread.cfm?qid=141900
 
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Yes it can matter but it mattered much more in the past as steel making has improved with fewer inclusions. There are other considerations also [anisotropy ].Anisotropy is having different properties in different directions. That can be critical in precision die making where before/after HT dimensions can be different and those differences must be calculated for three different directions !!
One of the improvements that CPM process gives is better toughness but most of that is in transverse toughness . The other way to improve things is to cross roll. A more complicated process where the steel is cut into squares and each rolling pass the steel is rotated 90*
 
I asked Achim Wirtz if it mattered which way I cut his 115W8 and he said no because it had been cross rolled like the mill does for other steels used for big circular saw blades. Bestar lists their saw steel sheets as being cross rolled.
 
Well this is 1084 from aldo. I'm a welding inspector and it does matter for us so I just wanted to check.

Hoffman do you have the link to that thread? I would love to read it.

Mete. Are you saying that it's not worth worrying about? I'm going to be new anyway so maybe not but would like to develop good habits down the road.
 
Is it kosher to cross-post from another forum?
 
Almost all the steel we sell is cross rolled. Some are cross rolled hot and others cold. The only major steel mill we buy from who doesn't cross roll is Niagara.

One question I've never had answered, do powder metallurgy steels have a grain direction? I've been told yes and no by different companies.

Chuck
 
Skillgannon , AKS, both of you are familiar with it so you are better off with that knowledge. Much depends on the type of steel and how it will be used .
As for inclusions the cleaner the steel the less of a problem . So CPM as we know the difference is substantial.
Anisotropy - that's helped by cross rolling
Chuck , how many PM makers cross roll their steel? Shouldn't be too many! I did a lot of tool steel work and learned many little tricks but it always depended on knowing the steel an the uses.
Those companies that told you they didn't have grain direction depends again on cleanliness and steel type and how it's processed.
 
I don't know anything about the specific metallurgy involved with it, but my company makes a number of products for a number of customers who specify the grain direction of the parts we make for them. These are inevitably parts that see repeated stress in a particular direction in their application. The nature of our business is such that we also make extremely similar parts, from the same materials, that are applied in nearly identical fashion, in competitors products that do not specify grain direction.

My opinion on the question does it matter has developed from the above. It certainly matters to us as the manufacturer of the parts, because they behave differently during manufacturing in respect to the grain direction. I believe it can matter in a part engineered to be just sufficient to do the job it's supposed to, and it matters very little if at all in a part that is engineered with a 3x safety factor. Last, I believe it's a holdover from a time when steel making was less predictable than it is today.

Does it matter? It can, especially to the person making something from it. Does it affect the end product? Saying "it doesn't matter" would probably be less than accurate but it's very low on my list of concerns in how a knife performs for the end user. "This knife failed because it was made across the grain direction" is not a thread I ever expect to see.
 
Yes it matters. Cross rolling doesn't necessarily fix it because the degree of cross rolling is usually much smaller than the reduction in the "rolling direction." Reduction of impurities doesn't necessarily fix it because in tool steels it is often carbides that have the greatest effect on directional properties, and they are usually located in bands or stringers along the rolling direction. Powder metallurgy helps but even then the numbers they give are significantly lower in the transverse direction, often half or less: http://www.crucible.com/PDFs/DataSheets2010/dsS30Vv1 2010.pdf

In conclusion, you need to know what the rolling direction is, and understand how it will affect different use types and knife designs, or you might make a knife with different attributes than you desired, such as easily broken tips. On the flip side, carbide bands may affect the cutting behavior whether for good or bad when they are oriented transverse to the cutting edge.
 
Does it matter any - sure it does.
Does it matter a lot - not really, to a knifemaker
Does it determine a good vs bad knife - no it doesn't.

If I was building parts for NASA, or designing a 100 story skyscraper, I would pay a lot of attention to it.
If I was buying a bar of steel, I would assume the length of the bar was the direction of the roll. If cutting blades from a 12X36" sheet, I would guess the short direction as the roll direction grain (sheared off a longer roll).

With the thinness of blade steel and the nature of our HT, the difference in the blade from the rolling direction is minimal to anyone but a metallurgist or a lab. Beyond theoretical discussions among knifemaker/metallurgists, I don't ever recall reading about it being a concern.

My guess is that millions of knives are commercially and hobby made every year with no concern for the roll grain.
 
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I posted this in the carbide/banding thread but in light of this discussion, can one of our experts tell me that this banding is the grain direction? I'm just assuming that's the case. I have multiple blanks that I cut from this sheet of 1095, some with the grain, some opposed, some at various angles to achieve the best material utilization I could with the blanks I was cutting. Would I be able to expect this banding to show in different directions on those blades assuming the same heat treat and etching procedures are followed?

Now I wish I would have identified which was cut in which direction but I did not.

Cs5rmoA.jpg
 
Stacy E. Apelt - Bladesmith said:
Does it matter any - sure it does.
Does it matter a lot - not really, to a knifemaker
Does it determine a good vs bad knife - no it doesn't.

If I was building parts for NASA, or designing a 100 story skyscraper, I would pay a lot of attention to it.
If I was buying a bar of steel, I would assume the length of the bar was the direction of the roll. If cutting a 12X36" sheet, I would guess the short direction as the roll direction (sheared off a longer roll), but that wouldn't stop me from cutting a sword blank from a 12X36" sheet.

With the thinness of blade steel and the nature of our HT, the difference in the blade from the rolling direction is minimal to anyone but a metallurgist or a lab. Beyond theoretical discussions among knifemaker/metallurgists, I don't ever recall reading about it being a concern.

My guess is that millions of knives are commercially and hobby made every year with no concern for the roll grain.
Click to expand...
25% or 50% of the toughness in the transverse direction is not simply a theoretical discussion.
 
This is not meant as argumentative. You have my interest.

That is a huge difference. I have never read about such large variance. Can you cite those losses in any blade steel and dimensions at the hardness we do blades in?
I know it has an effect concerning flex and such in springs, and having an effect on bridge girders and major structural steel works in lower carbon steel.

Does forging reduce the degree of effect?
 
Stacy E. Apelt - Bladesmith said:
This is not meant as argumentative. You have my interest.

That is a huge difference. I have never read about such large variance. Can you cite those losses in any blade steel and dimensions at the hardness we do blades in?
I know it has an effect concerning flex and such in springs, and having an effect on bridge girders and major structural steel works in lower carbon steel.

Does forging reduce the degree of effect?
Click to expand...
http://www.crucible.com/PDFs/DataSheets2010/dsS30Vv1 2010.pdf See the listed longitudinal and transverse toughness numbers for S30V, 440C, and 154CM. 25-28 ft lbs in the longitudinal direction vs 10 for S30V and 2.5 for 154CM.

Forging vs rolling can lead to different distributions of carbides and impurities. The degree of differences depends on the degree of reduction. Forging to shape of course leads to a change in shape of the carbides and impurities, so the direction of those stringers follows the profile.
 
Thanks, I checked some other steels, and the only ones I could get comparative LvsT were the high alloy stainless steels. Above S30V, the transverse rises. The LvsT for CPMS35VN was very good .... probably why I never saw any issue.
http://www.crucible.com/PDFs\DataSheets2010\dsS35VNrev12010.pdf

Can you find the data sheets with the Charpy tests LvsT for steels like 52100, 1095, and 5160?

What I was referring to in my comments about a knife geometry not being apples to oranges is that the shape and very thin edge of a knife will yield to a blow far below the transverse yield point of a Charpy test. Even 3 to 4 joules is a big blow to a hardened blade.

I will amend my comment about deliberately cutting across the grain.
 
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