Why 300M???

[atomicjoe23]

I've been wondering about this for awhile. . .whether 300M is really all that better than 4340 or if it's just a marketing ploy. . .

. . .and with my new job (tool & die maker apprentice) I have access to a lot more resources (both written and experienced toolmakers) I'm leaning towards 300M being a marketing ploy unless I'm missing something.

I looked up the numbers on 300M today to compare it to 4340 and here's what I came up with. . .

If 300M has quite a bit higher tensile strength in the Rc56 condition (340 ksi) than 4340 does in the Rc54 condition (287 ksi), but the yield strength is WAY low for the 300M (only 180 ksi) vs. the 4340 (at 270 ksi) plus the percent elongation for 300M is ridiculous, only ranging from 6-9.5% and the percent reduction is also pretty sad ranging from 10-34%. While 4340 has a percent elongation range of 11-23% and a percent reduction range of 339-63%. . .this is of course dependent upon the heat treat condition of the material, but let's look at what is probably the most useable condition only:

300M (Rc 54.5) 4340 (Rc 53)
tensile strength 310 ksi 287 ksi

yield strength 240 ksi 270 ksi

percent elongation 7% 11%

percent reduction 27% 39%


Just from looking at these numbers it seems like the 4340 should be a significantly "tougher" material with the only real difference being the ultimate tensile strength. . .but the higher yield strength, percent elongation, and percent reduction of 4340 meaning that there is less likelihood of seeing a catastrophic failure than with 300M which would be a harder, more brittle material and therefore more likely to experience catastrophic failure.

I'm just wondering if I'm missing something here or if 300M is not such the great material that it is being played up to be.

Looking forward to hearing the feedback from inidviduals in the know.

Thanks!

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[atomicjoe23]

Figured that I should also mention that 300M is 4340 modified with additional silicon, slightly higher carbon and molybdenom, plus vanadium. . .

here's the breakdown for those of you who are metallurgically inclined:

300M (%) 4340 (%)
Carbon 0.40-0.46 0.37-0.44

Manganese 0.65-0.90 0.55-0.90

Silicon 1.45-1.80 0.15-0.35

Chromium 0.70-0.95 0.65-0.95

Nickel 1.65-2.00 1.55-2.00

Molybdenum 0.30-0.45 0.20-0.30

Vanadium 0.05 min. N/A

So you can see there isn't that much difference between the two and depending on how well the alloy is controlled they overlap pretty much everywhere with the exception of the silicon and vanadium.

The vanadium contributes significantly to the strength and hardness of 300M. . .vanadium is used in higher quantities than 300M when producing HSS (think the tool bits used with lathes and mills. . .and a minimum percentage of 0.15% vs. the 0.05% found in 300M). . .

. . .while the silicon

[sickdayz]

Interesting... I think...

[Bro_Gill]

I have spoken with a machinist on this as well. He has said he doesn't understand what the push is for 300m in many of the things we build, especially since it can't be welded properly. He thinks 4340 would be a much better material for much of the stuff. Another machinist/metalurgist who does a lot of Penske work says 300m is exactly what you allude to, just a marketing ploy and says there are plenty of other materials that are much better for what we do. I think 300m was what Sway-a-way had to come up with to charge more for their torsion bars after they lost their good supplier of standard material and started using inferior material in their standard line of bars and could charge more for 300m since it would be the equivilent of their old bars. I don't think anyone who has been around for a while remembers how their standard bars used to last just fine and now a days, even 300m material takes a dump pretty quick. Anyway, that is how I see it.

[Haycock]

yea but all the cool kids run 300m....

there is alot of stuff in the off road industry that is overpriced and over hyped. i believe 300m is one of them.

Thanks for the info!

[mikeyfrombc]

what heat treating for the 4340 are you using when comparing to 300M ?? and are you sure the RC #s are correct , i recall 4340HTSR being 39/42 RC , 54 is pretty tough most bearings are 60/65RC

[atomicjoe23]

what heat treating for the 4340 are you using when comparing to 300M ?? and are you sure the RC #s are correct , i recall 4340HTSR being 39/42 RC , 54 is pretty tough most bearings are 60/65RC

I was using the highest Rc that looked to be useable for 300M and then using the closest equivalent Rc for 4340. . .

. . .I will be happy to post numbers that compare 4340 and 300M in the 39-42 Rc range if that is what is most common in this application. I didn't/don't know what the draw temperature was for gears and axles so I just guessed. . .

here are the numbers for 4340 with an Rc of 39 (draw temperature of 1000*F, which is a pretty darn high draw temp!!!. . .I've been heat treating some O-1 1-2-3 blocks, angle plates, datum pin, and a 4340 grinding arbor at work the last week and have drawn all of them at 400*F) and 300M with an Rc of 45 (lowest my chart shows which is a draw temp of 800*F), 4340 first followed by 300M

Tensile Strength 180 ksi 260 ksi

Yield strength 168 ksi 215 ksi

% Elongation 17 8.5

% Reduction 53 23

[FABRICATOR]

You might try Googling:
"300m for aerospace"
"300m for military aircraft landing gear"
"300m for turbine blades"
"300m for drag racing"

It's not much different than many super alloys in that it can eventually suffer failure from corrosion or other surface damage. If you are pushing things to the limit you will need it, Maraging steel, or something similar.

[mikeyfrombc]

after looking at the cost i,d stick with 4340 LOL , i priced out a 3" OD piece of 300M and for a 6" long crop it,s $496.00 where the same piece of 4340annealed is roughly $65.00

[atomicjoe23]

You might try Googling:
"300m for aerospace"
"300m for military aircraft landing gear"
"300m for turbine blades"
"300m for drag racing"

It's not much different than many super alloys in that it can eventually suffer failure from corrosion or other surface damage. If you are pushing things to the limit you will need it, Maraging steel, or something similar.

I've been looking at Maraging steel the last day or so. . .specifically Vascomax T or C series, on paper the VascoMax seems MUCH more desirable than 300M and the price isn't much different.

after looking at the cost i,d stick with 4340 LOL , i priced out a 3" OD piece of 300M and for a 6" long crop it,s $496.00 where the same piece of 4340annealed is roughly $65.00

I'm with you on this one. . .the properties of 300M don't seem to merit the extra cost that's for sure!!!