Forged vs Stock Removal Knives

JDWARE said:
Great article Larrin. Thank you.

A question - How has the technology of Continuous Casting effected the "quality" of steel for knifemakers? I don't know if the steels we commonly use are produced this way or not. I imagine that the initial thickness for Continuous Cast steel is much less than the thickness of a traditionally cast ingot, and therefor is subject to less forging/rolling elongation. It's obviously more economical for the steel mills, but is it better for us?
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Larrin said:
I’m not a steelmaking expert. As I understand it high alloy tool steels are not well suited to continuous casting. Not sure how much it has caught on in tool steels, but is common for other types. It might be used in the strip steels, someone will have to remind me.
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The use of continuous cast slabs is fairly universal, as far as I'm aware. This eliminates the "slabbing mill" which converted ingots to slab. Slabs are generally still quite thick, however. A few steelmakers have endless "thin slab" technology, which is economical for production, but of course features lower levels of reduction. However, fast solidified thin slab steel is purported to have smaller primary carbides than conventional slabs.

Larrin, this is somewhat off topic, but what do you think about microstructure of near-net-shape manufactured (powder steel) knives, which have very low levels of reduction compared to the same alloy rolled into bar or flat stock?
 
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Nick Dunham said:
Larrin, this is somewhat off topic, but what do you think about microstructure of near-net-shape manufactured (powder steel) knives, which have very low levels of reduction compared to the same alloy rolled into bar or flat stock?
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I haven't heard of those knives being made. What companies are making them?
 
I should have realized you meant that.

Larrin said:
I haven't heard of those knives being made. What companies are making them?
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I was going to say that Ferrum Technology uses MIM; however I can't verify what technology they're using on the blades themselves. The discontinued Kershaw Offset has a 440C MIM blade.

I thought I saw one micrograph of MIM M2 HSS that has lots of fine carbides, but also several larger carbides, perhaps around 5-10 micron size. I've been unable to find it again, so perhaps I was mistaken. It's interesting to consider that MIM starts with fine powder, but does not undergo a forging process to refine the carbides.

All that to say... It would be cool to see as-HIP micrographs compares to rolled flat stock of the same PM steels, and I wonder if they're published/available.
 
Magnetic or true north?
AVigil said:
You totally did not take into consideration how the smiths spirit is imparted to the steel or the benefits of Yak Urine in the quench :D:D:D:D:D:D:D:D

Nice article, much appreciated
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Nick Dunham said:
I was going to say that Ferrum Technology uses MIM; however I can't verify what technology they're using on the blades themselves. The discontinued Kershaw Offset has a 440C MIM blade.

I thought I saw one micrograph of MIM M2 HSS that has lots of fine carbides, but also several larger carbides, perhaps around 5-10 micron size. I've been unable to find it again, so perhaps I was mistaken. It's interesting to consider that MIM starts with fine powder, but does not undergo a forging process to refine the carbides.

All that to say... It would be cool to see as-HIP micrographs compares to rolled flat stock of the same PM steels, and I wonder if they're published/available.
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You don’t have to use nitrogen atomized powder for those kinds of technologies. And with choices like M2 and 440C, ground steel powder seems like a strong possibility.
 
OK I understand what was being asked about round bar vs plate/sheet now. The reduction ratio is the original cross section divided by the final cross section. With plate the width is basically unchanged so the ratio is original thickness divided by final thickness. A 10" ingot reduced to 1" would be 10:1. With round bar after you cancel out pi and everything it ends up being original diameter squared divided by final diameter squared. So a 10" diameter ingot reduced to 1" round bar would be 100:1. To get the same reduction ratio with plate it would require rolling down to 0.1".
 
Willie71 said:
Hmmm..... Natlek hasn’t commented here yet.
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And reason for that is because personally I don t take ALL your test relevant .HT on all that samples you test was done in most unreliable oven and temper was done in toaster oven !
rihOemT.jpg


We have done a limited number of other comparisons between longitudinal and transverse toughness. Z-Tuff was 45.7 ft-lbs longitudinal and 29.2 ft-lbs transverse, both at 61.3 Rc. Vanadis 4 Extra was 13 ft-lbs longitudinal and 9 ft-lbs transverse when at 64.6 Rc. No appreciable difference in toughness was seen between direction in Vanax or M390, which may be because there is less difference between orientations at lower toughness values.
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I don t take seriously someone who write this ......
Forging typically leads to maintaining the orientation of the “grain” along the edge rather than modifying it, such as in this simple schematic, where stock removal is on top and forged is on bottom. Therefore I wouldn’t expect a drastic difference in edge behavior.
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Wouldn t expect drastic difference ?????? is scientific answer ? Imagine that ......I wouldn t except ?? So is there difference and HOW MUCH drastic it is ??
Where is test for comparison between forged and stock removal blade ? And who done that ?
Carry on , I do not care about this topic without real proof .You ask about my opinion so there it is ..
 
Larrin said:
OK I understand what was being asked about round bar vs plate/sheet now. The reduction ratio is the original cross section divided by the final cross section. With plate the width is basically unchanged so the ratio is original thickness divided by final thickness. A 10" ingot reduced to 1" would be 10:1. With round bar after you cancel out pi and everything it ends up being original diameter squared divided by final diameter squared. So a 10" diameter ingot reduced to 1" round bar would be 100:1. To get the same reduction ratio with plate it would require rolling down to 0.1".
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Thanks, Larrin. That's what I was asking about. I appreciate that with modern steels there may be a point of diminishing returns as to the benefits of reduction. But in the hypothetical example you gave, a knife forged from the round bar would have seen at least 10 times the reduction of a knife ground from a section of plate. Probably closer to 40 times reduction, if the knife is forged closely to shape.

Edit: sorry, I didn't think about how your example was for 1" plate, which is clearly not a good size for stock removal. So let's assume it's 1/8" plate, then it's an 80:1 reduction from the 10" ingot, vs 100:1 for the 1" round bar. But then if the round bar is forged, you still end up with let's say a final 200:1 or greater total reduction, which is a large difference. I imagine it won't make much difference in performance, but it's also not true that the stock removal knife has seen the same level of reduction.
 
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Natlek said:
And reason for that is because personally I don t take ALL your test relevant .HT on all that samples you test was done in most unreliable oven and temper was done in toaster oven !
rihOemT.jpg



I don t take seriously someone who write this ......

Wouldn t expect drastic difference ?????? is scientific answer ? Imagine that ......I wouldn t except ?? So is there difference and HOW MUCH drastic it is ??
Where is test for comparison between forged and stock removal blade ? And who done that ?
Carry on , I do not care about this topic without real proof .You ask about my opinion so there it is ..
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Ok then.
 
Natlek said:
And reason for that is because personally I don t take ALL your test relevant .HT on all that samples you test was done in most unreliable oven and temper was done in toaster oven !
rihOemT.jpg



I don t take seriously someone who write this ......

Wouldn t expect drastic difference ?????? is scientific answer ? Imagine that ......I wouldn t except ?? So is there difference and HOW MUCH drastic it is ??
Where is test for comparison between forged and stock removal blade ? And who done that ?
Carry on , I do not care about this topic without real proof .You ask about my opinion so there it is ..
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No one should take your opinion seriously too.

I hate when a person like you keep trolling people who who actually take their time and resource to contributing all of this test.
 
Willie71 said:
Hmmm..... Natlek hasn’t commented here yet.
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So if you know that someone is going to give you an opinion that you don’t like, and then you call them out and wonder why they haven’t commented... who’s really trolling who?
 
Great article again larrin and thank you
So would there be more noticeable "dynamic recrystillization" of carbides in hand forging 1" round down to shape for integrals for example more so than forging tapers and bevels in to thin stock? Esp with those with vandium
Again great article
 
John mc c said:
Great article again larrin and thank you
So would there be more noticeable "dynamic recrystillization" of carbides in hand forging 1" round down to shape for integrals for example more so than forging tapers and bevels in to thin stock? Esp with those with vandium
Again great article
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Carbides also suppress recrystallization. Suppressing recrystallization usually makes grains finer once recrystallization doesn’t occur.
 
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