440 Hc

Larrin said:
But 440A also has large carbides, just a smaller volume of them.
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The carbides are both smaller and much lower in volume and this gives greater edge stability.

sog said:
Interesting. Described where? Are you sure it is 440C they are talking about?
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Yes, Carpenter makes it :

http://www.carpentersteel.com/products/wr_products_tool_440xh.html

It is essentially 440C with a much higher carbon content.

sog said:
I have some 440 knives but the steel is so soft it doesn't get very sharp and wont hold an edge. I think I'll get some carbon and make the edge red hot and try to put carbon in the steel and quench it.
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Just have it properly rehardened, it can reach ~59 HRC.

-Cliff
 
When we're talking about the HC designation with stainless isn't that just a marketing term? There are quite a few ads I've seen that say "High carbon stainless steels" for steels such as 420j, 440A, etc. I think you guys are attributing too much to the "HC" designation here. It's likely put there by someone without any knowledge of steel classifications ie; an ad writer. Joe
 
The HC modifier means more carbon, even a steel which is normally classified as a high carbon steel can get the HC modifier and thus be a higher carbon version.

-Cliff
 
Thanks Cliff, I will roll with that. Do you think that RC56 would be a bit soft for this steel, or should it hold a realatively decent edge? Like I said I haven't used any 440 grade steel for a few years. I can resharpen just about anything with little effort, but don't want a butter knife at the end of every other day either. Actually it would be easy to resharpen a softer steel obviously just don't want to everyday. Thanks, Cliff
 
56 HRC is the hardness of the Swiss Army knives so you will likely notice a difference between that and a 60 HRC edge it will be similar to the difference between a SAK and the low end kitchen cutlery around 52 HRC.

You can however always go a long way with an optomized edge and grit. I have for example cut ~50 meters of cardboard with AUS knives of similar hardness (mid fities) and they still slice paper readily.

However, aside from 420J2, all of the 440/420 series should be much harder than 56 HRC for optimal blade performance unless you are making more of a utility tool than a knife.

-Cliff
 
Cliff,
I was pretty much thinking the same thing about the steel being too soft for the optimal knife application. What would you reccomend as the optimal edge and grit for this particular knife steel and hardness? maybe a coarser grit at an steeper angle?
Jeff
 
opening boxes, nylon rope, cardboard, fuel lines (rubber), plastic fertilzer bags, heck I ever cut an aluminum reccessed lighting fixture a couple days ago when no other tool was available. So pretty much anything. Although aluminum is pretty rare. I cut soda cans at least once a month for small drain pans where other pans wont fit. But as we both know they don't do much damage just dull a little bit. I have put my sebenza through the mill over the last couple years.
 
Gene Martin said:
What 440HC means is that they won't tell you what the real steel is. Same as saying surgical stainlerss. It's a lack of description as opposed to being specific.

Gene
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I agree with this. Lets remember it's Microtech that were talking about. They're not known (according to some),as the most scrupulous of companies.
 
My guess like before is that 440 HC simply means a 440 steel that is high in carbon. Since 440A is often referred to as a "high carbon" steel, I bet 440HC simply refers to 440A. If you're lucky, it might be 440C, but it's not some extremely high carbon 440C.
 
sevenedges said:
opening boxes, nylon rope, cardboard, fuel lines (rubber), plastic fertilzer bags, heck I ever cut an aluminum reccessed lighting fixture a couple days ago when no other tool was available.
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The first materials are all very soft and do well with fairly acute and coarse edges so I'd first start with something like 15 degrees per side and at least 600 DMT or more coarse. However even light metals will damage such edges fairly easily and are best suited by a higher polish so I would move up to 1200 DMT with a 20 degree edge. So, as a first pass I would regrind the edge at 15 degrees with an x-coarse stone, refine it to 600 DMT, then sharpen the last bit of the tip with the 1200 DMT and use that for cutting the metals. If you don't have DMT's then use anything similar, medium/fine Spyderco for example or coarse/fine india. These are not exact grit replacements but the general same class. You then refine these grits and angle by the way the blade behaves.

-Cliff
 
Cliff Stamp said:
Quote:

Originally Posted by Larrin
But 440A also has large carbides, just a smaller volume of them.

The carbides are both smaller and much lower in volume and this gives greater edge stability.
-Cliff
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Isn't 440 A, ,B C, all made from the same stuff with different amounts of carbin? I'm assumeing the carbides themselves would be the same size?
 
440A is used for blades that are manufactured by stamping. The lower carbon content makes it "stampable" unlike the B and C versions which have a tendency to fracture when stamped. Also, B and C versions of 440 alloy cannot be rolled into large coils which is another reason they are not used in full production type blades. 420HC can be rolled into coils as can Aus6. That is why they all get lumped into the cheap category because that is all that is available for stamped stainless steel.
 
db said:
Isn't 440 A, ,B C, all made from the same stuff with different amounts of carbin? I'm assumeing the carbides themselves would be the same size?
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The type of carbide is influenced by the amount of alloy. For the mean compositions, the austeniste in 440A has K1 carbide, 440B a mix of K1/K2 and 440C K2 carbide. However the main difference in behavior comes from the volume fraction. 440C and 13C26 for example both have K2 chromium carbide but it is up to 50 microns in 440C and < 1 micron in 13C26.

This is actually why Buck switched from 440C to 420HC, the "cheaper" steel gave better results on the CATRA work. This is also why the P/M steels are typically high alloy as low alloy steels don't have issues with segregation so you are solving a problem which doesn't exist. For example, the chromium carbides in RWL34 (P/M ATS-34) are up to ten times the size of the carbides in 13C26 (ingot).

-Cliff
 
Interesting that no one has proposed asking Microtech. Is it just that we don't think it's worth the trouble as their reply wouldn't be believed?
 
Cliff, you are the man. I wish I knew all of the techincal stuff. I think I'm going to dedicate a few hours each week doing research on steels and steel composition. I have a very nice welding book from when I was in Tulsa Welding School. It has a lot of info on heat treat, steels, and other stuff. I've just got to make the time to do it. As for asking Microtech I bet they would only give you the "pros" of the steel and not the "cons". I could be wrong though.
Jeff
 
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