Vacuum Arc Remelting (VAR) and Electro Slag Remelting (ESR)

[nozh2002]

As I understand this purification technology in combination what Russian use for 100x18MSHD steel. Is this technology used in US for knife steels - like 440C which is similar by composition to 100x18MSHD? I know that Hitach in Yasuki adopted it but not sure that they use it for their knife steels.

From http://www.rosarmsusa.com/design.htm
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The application of 110x18M steel grade
When dealing with precision bearings employed in mission-critical systems where they have to operate without lubrication under high temperature conditions in corrosive mediums, one needs to use a metal of a special chemical composition and as free as possible of nonmetallic inclusions. The research of 1966 ascertained that 110x18M steel grade is the one to meet all requirements. To decrease the content of nonmetallic inclusions, vacuum-arc remelting (VAR) was suggested.
Point analysis of maximal nonmetallic inclusion content
Nitrides Oxides

Conventional remelting 4 points 4 points
Electroslag remelting (ESR) 2 points 2 points
Vacuum-arc remelting (VAR) 1 point 0.5 - 1.0 points

Metals undergoing double remelting (ESR + VAR) have half as many nonmetallic inclusions as compared with ESR plus a reduced gas component. The metal density is greather than when applying ESR alone. Thanks to that we have better plastic properties, improved polishabiliti, and good strength characteristics. Milled carbides help to grind the blade's edge and keep it constantly sharp.

All the above factors prolong the bearing service life.

Electroslag remelting process (ESR) is an arcless process of remelting a metal electrode in a flux bath. Electrofluxed metal is noted for its premium quality, lower impurity and gas content, improved micro- and macrostructure, lower anisotrophy (directional property), twice as high mechanical properties, two up to five times more reduced nonmetallic inclusion content (such as oxides, sulphides, globules), higher wear-resistance and contact resistance, plus minor improvment of other characteristics. Electrofluxed metal is used in the production of steels and alloys for defense industry and aircraft industry. Warranty assurance is twenty years.
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Any comments?

Thanks, Vassili.

 

[Larrin]

I'm not sure what the question is but I'll try to help. Conventional 440C, 154CM, etc. are not ESR or VAR. BG42 is VIM VAR, or Vacuum Inductional melted, and then Vacuum Arc Remelted or whatever those stand for. It's probably the cleanest and most uniform steel outside of PM or sprayform. Bohler does make an N690 ESR (though it's separate, most is just plain N690) that's probably pretty good, it's VG10 plus 2-3% chromium, so basically a cross between 440C and VG10. It has the cobalt, a little extra molybdenum, and a small percentage of vanadium just like VG10. There are one or two other ESR steels that I can think of but they're not common at all. I've also read that ESR or VAR reduces the carbide and grain size, but I haven't been able to find any numbers as to how much reduction actually goes on. As a side note, I'm sure you know what BG42 is, but Spyderco says that it's the best conventionally cast (as in not PM) that they've tested. Some 52100 is Vacuum remelted, but I'm not sure how much of it, I know Timken used to sell it in sheet that was remelted, but they don't seem to anymore. Some "Aircraft Quality" steel is Vacuum remelted. Basically it is some high quality stuff, with low impurity, etc.

 

[nozh2002]

...Basically it is some high quality stuff, with low impurity, etc...

I just like to understand where this Russian steel 110x18MSHD to put in between well known Western (including Japanese) steels. So if ESR and VAR is not common methids for western steel then, this one most likely better then just 440C which has same composition, but Russian steel was made using ESR and VAR, so it is not just Soviet analog of well known 440C, but something better, at least I may expect it.

It is nice surprize for me because I thought it is old good 440C, but looks like it bit more premium. So far I did not run any formal testing but by use it feels like premium steel, you can see it when sharpening etc...

Only one reference to ESR I saw in the article about Yasuki Special Steel, if you may describe a bit what it is on high level will be really interesting.

Thanks, Vassili.

 

[mete]

These special melting techniques are various ways of getting steels with fewer inclusions .It any not have any benefit for knives .They are " aircraft quality " or "bearing quality" which require minimum inclusions [BC42 is a bearing steel and 52100 is often used for bearings] . A more significant improvement for knives is the CPM method of Crucible and other companies.This minimizes inclusions but also makes smaller and more evenly distributed carbides.

 

[nozh2002]

...not have any benefit for knives .They are " aircraft quality " or "bearing quality" which require minimum inclusions [BC42 is a bearing steel and 52100 is often used for bearings].

It is hard to belive that it has no benefits for knives.

If this bearings have 20 years warranty I can imagine that knife will benefit from such steel feature. And this two bearings steels you mentioned are well respected steel for knife applications.

As well as low impurity - I think it is also important for overall steel properties including toughness and wear resistance.

Thanks, Vassili.

 

[mete]

Those melting methods help bearings because bearings fail most often by fatigue[ Spalling].You will never get a knife failure due to fatigue !! Wear resistance should not be improved . Toughness will ,to some degree, be improved. BTW, I started my career as a metallurgist at Timken !

 

[Cliff Stamp]

You will never get a knife failure due to fatigue !!

The most common failure of knives is due to fatigue, it is a major source of the reason why edges take damage. Edges deform readily in use as the steel is about 0.1 micron thick and it keeps bending back and forth and is compressed and torsionally loaded until it breaks off. You can see the folding lines even under light magnification and then later see the edge break off in sections. There are other issues as well such as damage to the tip in reverse load fatigue failure that everyone has seen demonstrated commonly with a paper clip.

-Cliff

 

[mete]

That's not quite the definition of fatigue that we mean in bearings . The bearing fatigue failures occur after many thousands of cycles.

 

[Larrin]

That's not quite the definition of fatigue that we mean in bearings . The bearing fatigue failures occur after many thousands of cycles.

No offense, but neither me nor my father has talked to a metallurgist from Timken that knew as much as the Crucible guys.

 

[nozh2002]

Really interesting what conan will say about it - if he still around. He is from Crucible as I understand.

Thanks, Vassili.

 

[Cliff Stamp]

That's not quite the definition of fatigue that we mean in bearings . The bearing fatigue failures occur after many thousands of cycles.

The edge can deform multiple times during a cut and it isn't unusual for people to make a very high number of cuts before resharpening, especially for people who use edge alignment techniques such as steeling or mild stropping which will leave fatigued metal on the edge and in fact induce more fatigue themselves. I have noted in the past several times where fatigue failure lead to premature damage on chopping blades there the damage is visible by eye. An edge will see far more than 1000 contacts with wood when used limbing before sharpening, it isn't unusal to do even 10 times that.

Chad234 discussed the same thing a few years back and note why he stopped using methods of edge alignment on larger blades for the same reason as leaving fatigued metal on the edge induced visible damage. Now on the edge the fatigue is mainly torsional or tensile but there is also significant compression, even on cutting soft objects. It is a combination of on/off, static + dynamic and variable load fatigue. It also isn't just a chopping thing, as noted previously you can see it in just cutting, I have done lots of work where blades cut over a 1000 times before sharpening and you can readily see the deformation and watch the damage grow even under light magnification.

-Cliff

 

[James Polk]

The most common failure of knives is due to fatigue, it is a major source of the reason why edges take damage. Edges deform readily in use as the steel is about 0.1 micron thick and it keeps bending back and forth and is compressed and torsionally loaded until it breaks off. You can see the folding lines even under light magnification and then later see the edge break off in sections. There are other issues as well such as damage to the tip in reverse load fatigue failure that everyone has seen demonstrated commonly with a paper clip.

-Cliff

The problem is, the paper clip demonstration is NOT fatigue. Yes, I know everyone does it. See your mother's advice re: jumping off a cliff.

Fatigue is cause by repeated stresses BELOW the yield point - it's an elastic phenomenon. The edge behaviour described is plastic.

 

[Cliff Stamp]

That was why I was surprised by mete's comment about 1k cycles, generally most of the metals book define low fatigue failures at 10k and 100k and even 1M cycles being common as they are dealing with loads significantly under the yield point. Note here for example :

http://www.epi-eng.com/BAS-Fatigue.htm

They start off by discussing failure under UTS, specifically noting that the first fatigue lab tests are done at high loads which produce failure in a low number of cycles and then note the relationship between load and cycles, they also use the plastic clip as fatigue.

Back to knives, you can get high cycle below YS issues, it isn't all just an issue of plastic deformation. I have seen tips for example break after sessions of repeated digging/prying without plastic deformation and it isn't difficult to grossly load a knife laterally much more than 1K times.

Consider for example chopping with a large knife and using it to pry out chips, it isn't unreasonable to do well more than 1K chops in a single day, and then you have impacts which torsionally load the edge as well during the work. I have seen blowouts on blades time after time. They will work fine for awhile, but in hours to days they can start to come apart.

In edges you see the same thing, while the very edge deforms plastically there is elastic deformation above it and you can see stress lines in that region which will eventually crack. These stress lines are more common in some steels than others, it would be interesting to compare the fatigue properties to the edge behavior.

There are lots of other examples of use where knives can be loaded laterally significantly back and forth in the 10k-100K region, lots of common uses involve significant flexing.

-Cliff