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Is BV wrong? - 2nd best material to 300m

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ISUZUROVER

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Discussion starter · #1 · (Edited)
I have been doing a bit of research on axle material strengths - and I came up with the following info... (data from US and Oz steel manufacturers/Suppliers).

Material (other names) / Ultimate Tensile Strength (MPa / psi)

AMS-6418 (MIL S - 7108 / 4625M4 / HY-TUFF) / 1655 / 240 000

4340 / 1380 / 200 000

300m (4340m) / 1980 / 288 000

So it looks like HY-TUFF - as used by Superior and Maxi-Drive (Australia) to make axles - is almost as good as 300m (or about half-way between 4340 and 300m). And on www.outerlimits4x4.com (down at the moment so I can't post the link) Strange Rover posted that Jack at CTM told him he uses HY-TUFF when he can't get 300m anywhere.

But in the BV steel and axle bible, here is what BillaVista says about steels like AMS-6418/HY-TUFF...
THE HIGH SILICON, NICKEL CHROME STEELS
These are usually known by trade names such as Hi-Tuff and Stress Proof. They contain up to about 3 % silicon and are, as the names suggest, tough as hell. They are popular for stock car and off-road racing axles—and the alloys are very suitable for these applications. They are not as good as 4340 M or even 4340, but they are also a damned sight cheaper and, especially where the minimum weights imposed are high, the fact that a part with the same strength and fatigue resistance can be made lighter by using a better steel may be a lot less significant than the cost difference. However, these steels are tough only because of the high silicon content, which is mainly in the form of longitudinal fibers or strings of silicon. This limits the efficient (and safe) use of the alloys to parts with minimal section changes and virtually no transverse machining (we don't want to cut the longitudinal strings that make the stuff tough to start with, do we?). They also don't like being bent very much because that may rupture the silicon strings. Mind you, I have made a lot of street car antiroll bars from Stress Proof with excellent results and pretty severe bends—but in this case the bends are almost, by definition, in lightly stressed areas.
Click to expand...
Now we can see from the UTS values above, that HY-TUFF appears to be stronger than 4340 (sure there are discrepancies in the numbers between sources, but the 4340 value is the highest I could find for std 4340 from a steel manufacturer - and the HY-TUFF value was obtained from manufacturers, and is also the UTS claimed by Superior for their axles). As for the silicon content - 300m contains 1.45-1.8% silicon, HY-TUFF 1.3-1.7% - so surely the same should apply to 300m about the long silicone strings. I have looked around quite a bit and I cannot find any info (besides that from Billa-Vista above) that mentions the long silicone strings in Hy-Tuff being a problem for parts with section changes. And it has been reported that HY-TUFF axles can take a lot of plastic deformation without failing completely. If HY-TUFF is "a damned sight cheaper" than 4340m and 4340, but stronger than 4340 and the second best thing to 300m, then why isn't it used more?

So does BV or anyone else have any extra info?

There is also another good axle material (EN26 / X9940) that is reported by steel manufacturers to be stronger than 4340, which gives 2 choices for steels stronger than 4340, but not as strong as 300m. Info is here - note that both sites say that EN26 should be used for applications where more strength than 4340 is required.

http://www.interlloy.com.au/data_sheets/high_tensile_steels/en26.html

http://www.smorgonsteel.com.au/metalsdistribution/products/group.cfm?GroupID=18
 
#2 ·
Ben,

First, I'm pleased to see others digging into this stuff ;-)

Second - in the quote above you forgot the [7] at the very end, which is my footnote that correlates to (scroll to the bottom):

[7] "Engineer to Win". Carroll Smith; Motorbooks International, 1985 p.63

In other words, that particular italicized paragraph is not mine, but a quote from Carroll Smith.

With that said, my thoughts are:

- First, we need to realize that up here in the top end of steels (indeed, in any materials discussion) the use of terms such as "best' or "second best" is problematic at best. Best for what? Best in what sense? Considering the many factors from cost to ease of machining to the myriad of different ways to measure "strength" it's a difficult term to use and will always come with a vigorous amount of opinion and debate. Even declaring something as "strongest" is problematic because of the many different types of strength I discuss in the article, along with different applications and loads (repetitive, cyclical, shock, constant, etc.)

- We also need to know something of Mr Smith to be able to fully digest his words. He was a brilliant man, no doubt, but a fairly stubborn and opinionated fella at that. he doesn't always fully describe his opinions either - sometimes just saying "this is junk, don't use it" and leaving it at that. There are others who would disagree with him, as there are in many engineering discussions.

Looking at this statement of his specifically, a few things stand out to me:

- keep in mind that his statement as quoted here was not in a book specifically about axles. He says "They are popular for stock car and off-road racing axles—and the alloys are very suitable for these applications" I think that's significant. he then follows with "They are not as good as 4340 M or even 4340" Does he mean "not as good for making axles, not as good for some other application, or just not as good in general?" In either case, we must keep in mind that this is his (highly qualified, but not infallible) opinion - others will have other opinions- I don’t think it's a scientifically provable fact one way or the other.

- He also states "This limits the efficient (and safe) use of the alloys to parts with minimal section changes and virtually no transverse machining " What is his definition of "minimal section changes?" We don’t really know, and he doesn’t say. Again, my interpretation is that he's not talking just about axles here, and that it’s entirely possible that any axle profile would indeed fit the definition of "minimal section changes" - but I can't say for sure.

- Finally, his statement of "Mind you, I have made a lot of street car antiroll bars from Stress Proof with excellent results ..." I think is important. Especially those first 2 little words, "mind you". It reminds us that often what should or shouldn't work in theory or on paper is not always the same as the real world.

So, If it’s a campfire debate as to what is “best” I think it’s one with no real answer.

If it’s a practical discussion as to what to use to make an axle, I’m certain hy Tuff is an excellent choice, and also pretty convinced that the forging process, quality control, machining process, profile used, and especially heat treating will all be a lot more important to the overall suitability of the finished product that whether the raw material was 4340 or Hy Tuff.

Why isn’t it used more? I’ve no idea – you’d have to ask the manufacturers, keeping in mind they have many factors to consider from cost to availability to quality. I think it is used quite a bit though – if Superior and Strange use it, as well as CTM.
 
Discussion starter · #4 ·
Thanks for the clarification Bill (and very comprehensive reply). When I first copied the quote I must have missed the citation.

When talking about which is "best" I agree that is application specific and depends on many factors - however steel manufacturers often refer to one steel being stronger than the other - i.e. the Smorgon Steel link at the bottom of my first post where they say that "EN26 should be used when higher strength than 4340 is required". Speaking of EN26 - have you ever seen/heard of it in the US or Canada???
 
Discussion starter · #5 ·
On another matter Bill - do you have any specs for the UTS of 1541H - which seems to be used by most US axle manufacturers. As I understand it, the steel is supplied already induction (case) hardened and the splines are hobbed with no heat treatment afterwards. Is this right? If so, it explains why it is used so often (significantly cheaper than Q&T post machining) and also explains why axles made from this aren't necked down (machining pre-hardened steel isn't fun).
 
#6 ·
ISUZUROVER said:
... Strange Rover posted that Jack at CTM told him he uses HY-TUFF when he can't get 300m anywhere.
Click to expand...
To clarify this statement, Jack has NEVER used HyTuff for ANY of his U-Joints. He only uses it from time to time for axle shafts...not axle yokes BTW, just shafts. Before he makes them, he confirms with the customer that they understand what material it is. His "material of choice" is 300M, but he also has had good results with the Hy Tuff axles, in a nutshell, zero failures on axle shafts.
Jack does believe there is a future for Hy Tuff as so far it has performed great, but for now, be sure that your CTM Joints and axle yokes are 300M.
 
#7 ·
I wanted to try HY-TUFF for the axles in the CV's I run but for testing it was 300M. I have heard some pretty interesting things about HY-TUFF, the twist you get out of them before they break! I would like to see some long term beating and see how it holds up.


Andy
 
#8 ·
i was talking to Mal Story of Maxidrive a couple of years ago and the reason he believes Hi Tuff is not used more widely is that the heat treatment processes to get good results are time consuming and critical, so you must have faith in your heat treatment specialist to do it properly or you may as well make your axles from licorice sticks. He said he gets his axles done by the ton and not just a few at a time.
Bill.
 
#9 ·
ISUZUROVER said:
On another matter Bill - do you have any specs for the UTS of 1541H - which seems to be used by most US axle manufacturers. As I understand it, the steel is supplied already induction (case) hardened and the splines are hobbed with no heat treatment afterwards. Is this right? If so, it explains why it is used so often (significantly cheaper than Q&T post machining) and also explains why axles made from this aren't necked down (machining pre-hardened steel isn't fun).
Click to expand...
1541 is not really an alloy, it is a plain carbon steel with a few additions, but not enough to classify it as an alloy. It is an excellent material to make axles out of, it forges well, machines well and responds very will to induction heat treating. It is not capable of being thru hardened like 4340, 300M or other alloys because it is just not made for that. Axle manufactures such a Foote axle buy the raw material in an annealed condition, forge, machine and heat treat axle blanks that they sell to places like Currie, Moser, Strange, etc. These companies just cut the axles to length, single point the splines and do minor machining to the flange.
 
#11 ·
Hy Tuff as far as I could find is cheaper but not as strong in axles apps as 4340 or 4340M. Plain and simple, but can be more cost effective. The reason people like Jack are having low failure with Hy tuff axles is becuase they have final got the correct design and the material is overengineering the product. As for forming Hy Tuff special precaustions need to be taken so the silicon that gives Hy Tuff the rep, are not broken. 300M does not have the same or similar properties. Section changes would have to be formed rather then machined, ect. If you want to know what the right material to build and axle is use 4340 austempered, imo. 300m is great stuff but not needed with the proper design.

Also UTS is pretty much worthless for designing by. Steel fails at UTC but once you get past the yeild point steel start inot the plastic state and from a design stand point have already failed to the point of being unusable.
 
#12 ·
There are lots of different alloys now a days that have excellent properties for axle shafts, some of the less know ones are astra alloy, super max, and even EN30B in the right applications.
 
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#13 ·
A machinist buddy of mine has spoke of Inkanel (spl?) It is used widely in the manufacturing of oilfield ball-type valves. He has complained about how much this stuff is killing his equipment. Where does this Inkanel fit into the spectrum?
 
Discussion starter · #17 ·
RedBullJeep said:
To clarify this statement, Jack has NEVER used HyTuff for ANY of his U-Joints. He only uses it from time to time for axle shafts...not axle yokes BTW, just shafts. Before he makes them, he confirms with the customer that they understand what material it is. His "material of choice" is 300M, but he also has had good results with the Hy Tuff axles, in a nutshell, zero failures on axle shafts.
Jack does believe there is a future for Hy Tuff as so far it has performed great, but for now, be sure that your CTM Joints and axle yokes are 300M.
Click to expand...
Thanks for the clarification, I wasn't ever trying to say that Jack doesn't fully inform his customers about what they are getting.
 
Discussion starter · #18 ·
GOAT1 said:
1541 is not really an alloy, it is a plain carbon steel with a few additions, but not enough to classify it as an alloy. It is an excellent material to make axles out of, it forges well, machines well and responds very will to induction heat treating. It is not capable of being thru hardened like 4340, 300M or other alloys because it is just not made for that. Axle manufactures such a Foote axle buy the raw material in an annealed condition, forge, machine and heat treat axle blanks that they sell to places like Currie, Moser, Strange, etc. These companies just cut the axles to length, single point the splines and do minor machining to the flange.
Click to expand...
Cheers for the info. So do any axle manufacturers use 1541H for axles without integral flanges? Do you have some typical specs for 1541H?
 
Discussion starter · #20 · (Edited)
Weasel said:
Hy Tuff as far as I could find is cheaper but not as strong in axles apps as 4340
Click to expand...
Any data to back this up? the Manufacturer data (and reports from people breaking these axles) suggests it is stronger.

As for forming Hy Tuff special precaustions need to be taken so the silicon that gives Hy Tuff the rep, are not broken. 300M does not have the same or similar properties.
Click to expand...
Again any info to back this up? - 300M has a higher silicon content than HY-TUFF, and although I am not a metalurgist I would have expected similar structures to be present. All reports I have read are that 300m is a bugger to heat treat properly as well.

HY-TUFF specifications

300M Specifications
 
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