Question about Chrome Vanadium

You're probably looking for chrome-vanadium steel, used for making hand tools and parts of power tools. If so, it's AISI grade 6150 you're looking for. Or you may be looking for D2 tool steel. D2 usually isn't called "chrome-vanadium" steel, but it is one, and it has 12.5% chromium, so it's fairly corrosion resistant.

6150 falls between carbon steels and stainless steels for corrosion resistance. As for stiffness, all steels have about the same stiffness, regardless of their alloy or their hardness. They're all within a few percentage points of each other.

Stainless is a minor exception. It's about 5 or 6% less stiff than other steels, more or less.

By "stiffness" I assume you mean something like "springiness." In other words, its resistance to deflection under a given load. The difference among steels is how far you can bend them until they take a permanent bend. Up to that point, within the "springy" range, where they spring back like they were before you put the load on them, they're all about the same stiffness.

If you're talking about how much load you can put on them before they

*break*, or before they take on a permanent bend, that's a function of their strength and their elongation, or ductility.

-- Ed Huntress

Excellent info Ed. Thanks.

The catalog sheet says Chrome Vanadium Alloy. It's not hardened but is heat treatable.

How would you compare the strength and elongation of your best guess on the Chrome Vanadium to say 416 stainless? Or can you point me to a website with that info? Not having much luck finding specs on Chrome Vanadium

Thanks James

Ed Huntress wrote:

That's probably 6150.

'No need to guess. Here are some sources that will tell you most of what you want to know about steels. They're worth saving for reference:

(welding data)

(tool steel cross-reference)

(the Cartech site is a good one for your 416 question)

These are the sources I often use to answer questions about specific properties that come up here. Collectively, they'll handle about any steel-properties question you're likely to encounter.

Also, there are some excellent knifemaking and blacksmithing sites that have lots of practical information. Some of the folks here who follow those crafts can direct you to good sites.

As a minor aside, as you pick up the properties you're interested in, don't be surprised that chromium-containing alloys can be hardened quite a bit more than you'd estimate from their carbon content. A little chromium somehow interacts with the carbon to raise hardenability. That's true with some other alloy ingredients, too. I used to know how they worked but I've been out of the materials specialty for a long time.

-- Ed Huntress

Thanks for the links, Ed.

Harold

Thanks a bunch for the links!!

Just to pick your brain a tad more. WHat is involved with hardening the 6150 ? Is it plausable for a home machinist without special equipment? What about the dimensional stability? Will it shrink that much?

Thanks aga>

I would suppose a short soak at 1600°F or so, followed by a quench in water, or oil (be careful on that one, water will crack it if I'm wrong!), then temper anywhere from 300°F (file hard; brittle) to 800°F (much more elongation; no hardness to speak of). 400-500°F is good for tools that you want to bend a little before breaking, without being too soft.

*Checks Matweb*

6150 appears to be a low alloy steel (hey, 97% pure iron), presumably the Cr

• V assists carbide formation, concentrating the 0.50% C content as Ed mentioned. All the heat treated entries are oil quenched, so water quench would probably be, technically, a "bad thing". None for a temper under

1000°F, unfortunately. At that temper, it has very good strength (180ksi tensile) and 15% elongation.

Tim

-- "California is the breakfast state: fruits, nuts and flakes." Website:

Sorry, I got sidetracked.

I don't have specifics on 6150. It's an oil-hardening steel (that doesn't mean you necessarily quench it in oil; it really is just a rough indicator of the required quench rate, and oil-hardening is in the middle of the range). The basic specs on it don't suggest anything special.

However, I would look in up in those links I posted, or try to find it elsewhere if it's not there. One option is to find a big library that has the ASM's _Metals Handbook_ for steels.

Heat treating can lead to some real blue-smoke arguments, and we've had a few here. If you want maximum performance, you have to study the steel you're working with. Most people don't. But alloy steels can have some peculiar properties in heat treatment. Some are very sensitive to cracking and require temperature-ramping. Some require interrupted quenching for the same reason. And some shouldn't be tempered in the 500 - 700 deg. F range at all because they're susceptible to "blue brittleness."

So my recommendation is to do a little homework before heating the stuff up. I hope you'll find what you need in those links. If not, come on back and I'll try to find it.

As for dimensional stability, how much do you need? Steel usually is unstable in the "up" dimension. It swells rather than shrinks. That's because martensite (the hard phase) is less dense than the softer phases. And some steels are difficult to fully convert to martensite all at once. If you do a bad or marginal job, steel can grow for years. That's why double-tempering and sub-zero treatments are recommended.

However, we're talking about gage-block dimensional stability here. Again, how much stability do you need?

-- Ed Huntress

The best cheap source for Chrome-Vanadium steel is your local auto salvage. Leaf and coil springs make excellent tools. It can be forged, cut, or machined [after annealing]. One caveat is that it tends to be hot short when forging. Just don't overheat it or it will turn to Sh_t. Bugs

That's good steel, and it will perform pretty close to 6150 in most ways, but it isn't chrome-vanadium steel. Most leaf springs are made from plain-carbon AISI/SAE 1085 or chrome-manganese, 5160. 5160 also is the common steel for coil springs. It's chosen for its fatigue strength.

I don't think you'll see a lot of difference between these steels and 6150 in most applications, except where impact strength is a basic requirement. That's where 6150 shines.

-- Ed Huntress

Great links.

But, I'm curious about your comments on SS/chrome. SS is less stiff?? Not the stuff I deal with, esp. tubing. Or sheet. Chrome aids hardening? Then why is hardenable SS so rare?? I think a rel recent development, as well.

And sears lawnmower blades. I think these things come from another planet!

Yes. It's a little less stiff than mild steel. I'll see if I can find some Young's Modulus figures for common materials and post them. The "springiness" of a material -- that is, its stiffness up to the point where it breaks or takes a permanent bend -- is measured by Young's Modulus, or the Modulus of Elasticity.

Yes. I'd have to go back to my texts, but my recollection is that, up to some moderate percentage, it *slightly* improves superficial hardness, but that it *greatly* increases depth of hardening. The air-hardening steels, which through-harden to great depth, get their through-hardening properties from chromium. It's all but impossible to through-harden a thick piece of plain, high-carbon steel, such as AISI 1095.

Common grades of stainless, the 300-Series, can't be quench-hardened because the high chromium content (and maybe the nickel contributes; I forget) prevent the steel from transforming into the hard phase, which is called martensite. 300-Series stainless remains in the austenitic phase at room temperature.

When you heat-treat a piece of high-carbon steel, heating it above the transformation temperature (say, 1400 - 1650 deg F) converts the steel phase to austenite, where it remains as long as you keep it above the transformation temperature. Austenite is soft. If you cool the steel slowly, it transforms into another soft phase, called ferrite. If you quench it quickly, faster than the rate known as its "critical quench rate," it transforms into martensite, instead of ferrite. Martensite is hard.

Plain carbon steels have a very fast critical quench rate. That's why you have to quench them in water. Certain alloy ingredients slow that rate down. That's "oil-hardening" steel. You don't necessarily quench it in oil (whether you do depends on the piece's thickness, and the result you want), but the suggestion is that you can quench it a little slower and the austenite will still convert to martensite.

High-alloy steels that can be quenched even more slowly are the air-hardening steels. In very thin sections, even 4130 is more-or-less air-hardening. The A-Series tool steels will fully harden in air, up to substantial thicknesses.

I hope this is clear. I hate to have to re-edit these things.

-- Ed Huntress

Here's a short story on Sears lawnmower blades. My dad was a Sears store manager, which is where this comes from.

Up until the early '60s, Sears lawnmower blades were harder than a witch's heart. Then pieces tended to break off when they hit rocks. A few people lost toes as a result. They sued the socks off of Sears. So Sears (and everyone else) started softening the steel in their lawnmower blades until pieces wouldn't break off.

The result was blades that behaved as if they were made of frozen shit. I don't know if they've found a way to harden them without the breaking problems since, which your message implies. The ones I buy today for another mower are soft enough to sharpen with a worn file -- which is exactly what I do, when I'm not so lazy that I used the angle-head grinder.

-- Ed Huntress

Dizzying, but clear--I think! Where'd you learn alladis?? Sounds like you were a heat treater in a former life! Dat is a tough job!! Esp. in the summer...

But, the diff. between the SS tubing I have and CR is like night and day: SS is clearly stiffer. Sometimes, depending on finishes, you can't tell by looking at it, but you can tell by banging it/tugging on it. Also much harder! which mebbe is the flip side of stiffness?

The sears blades: Yeah, I couldn't vouch for the edge (did seem crappy, in retrospect), but tryna bend a bent blade back into shape (roots, donchaknow), was pert near impossible. Needed O/A. Mebbe not hard, but incredibly tough--which, IIUC, has its own measure of sorts.

I was the Materials Editor at _American Machinist_, back when the top trade magazines were taken seriously. I also covered heat treating. Learning that, and EDM, and gearmaking took me about three years of reading textbooks on the train twice a day.

Which meant I had to visit a lot of heat-treating shops, and, in the summer, I was damned glad to get out of them at the end of a day. The gearmaking shops ruined my leather-soled shoes from all of the sulfated cutting oil. And I had to wear suits, even in steelmaking plants.

d8-)

Stainless, even in the annealed state, is quite a bit harder than annealed mild steel. Once the mild steel is cold-rolled its hardness goes up considerably. But stainless's hardness goes up even more from cold-working. It work hardens like crazy, as we all know from machining it.

However, you can prove to yourself that stainless is not quite as stiff. Take equal-dimensioned sticks of stainless and any carbon steel, wire, strips, or rods, hard or soft, and put the stainless in a vise, hanging out enough so you can measure deflection (a few inches to a couple of feet, depending on thickness). Then hang a weight on the end and measure the deflection. Don't put on so much weight that it bends permanently; you're measuring springiness, not strength.

Then do the same with the stick of carbon steel. As you'll see, it will deflect slightly less than the stainless.

Hardness has nothing to do with stiffness, although it's closely related to strength. You can put more load on a hard/strong piece of steel before it will break or take a permanent bend. But, within the "springy" range, it doesn't matter if the steel is plain-carbon or high-alloy, heat-treated as hard as it can be or annealed. Within that springy range, the stiffness will be the same. Except for stainless. It will be slightly less stiff. (Going from memory, the carbon steel has an elastic modulus on the order of 31 Mlb.; stainless is around 28 or so).

I think I know what you're basing your assessment on. The stainless is enough harder and stronger than plain-carbon steel that you find it's a b*tch to bend it permanently. And, because it work hardens so quickly, it's even more of a b*tch to bend it back. So it seems extremely "stiff." But it's not stiff. It's just miserable to cold-work.

What they probably did was to go to a low-cost alloy that's tough and that has just enough carbon to harden a little bit. A manganese alloy will be very tough, and around 30 or 40 points of carbon will let them get it a little bit hard without being brittle.

It's easy on toes, but it dulls awfully fast. I had a Power Products mower made around 1957 that I held on to for over two decades, just because the blade was hard as hell. When the blade wore out I trashed the mower.

-- Ed Huntress

You can selectivly harden a mower blade, assuming decent material.

The Japanese did it very well with swords

Gunner

Rule #35 "That which does not kill you, has made a huge tactical error"

I made my mower blade out of P-20 on the recommendations of a mould and die guy.

Seems to work pretty well, edge holding is so so. But I dont have many big rocks.

Gunner

Rule #35 "That which does not kill you, has made a huge tactical error"

Sounds like the train rides mighta been pretty long! Lotsa reading??!! Was this in your Mount Vernon days? The only thing I have encountered in the summer that is worse than a heat treater's shop is a foundry. We got one in Queens, about the only one left. Talk about hell on earth... goodeffinggawd... And the noise!!! Oh, and add, to this ambiance, the fact that drug dealers&friends use the sidewalks during the summer the way you and I would use a beach--replete w/ towels, coolers, and rinse-offs under the nearest fire hydrant..

Metallurgy is just too goddamm complicated!

---------------------------- Mr. P.V.'d formerly Droll Troll

Well, I lived in Princeton for the first couple of those years. That was

2-1/2 hours, door-to-door. Sheesh. Then I moved to Metuchen. That's a 35-minute train ride into Penn Station NY, and then a ten-minute walk and ride up the 6th Ave. subway, to Rockefeller Center. That's where _American Machinist_ was located in those days. A very classy location, across the street from Radio City and next door to TIME-Life.

Oh, no. I left Mount Vernon when I was nine years old. You could still walk on the streets at night in those days. It really was Westchester then.

They're bad, but the one I hate is diecasting shops when they're really cooking. One of my co-editors compared them to Dante's Inferno.

It's not easy, but the practical stuff with steel really *is* fairly easy. You don't need metallurgy to heat-treat steel. You just need some good instructions and a little practice. But, unless you're an expert cook, stick to the cookbook.

-- Ed Huntress