Peter

jackie schmidt

jackie schmidt

New member
Something doesn't quite look right about your figures. According to the Charpy V Notch charts, S7 is far superior to 4340, and Flexor in reatained ductility at the higher HRC numbers. S7 shows a Charpy number of 170 at 48 HRC, while Flexor and 4340 are way down in the mid 20's at 45 HRC. In fact, flexor is only at 80 when tempered clear down to HRC 30.
I stand to be corrected, but that is what the charts I recieved today show........jackie
 
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Jackie- I believe that you'r correct but, That would be a C-Notch

jackie schmidt said:
Something doesn't quite look right about your figures. According to the Charpy V Notch charts, S7 is far superior to 4340, and Flexor in reatained ductility at the higher HRC numbers. S7 shows a Charpy number of 170 at 48 HRC, while Flexor and 4340 are way down in the mid 20's at 45 HRC. In fact, flexor is only at 80 when tempered clear down to HRC 30.
I stand to be corrected, but that is what the charts I recieved today show........jackie
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Figures and not a V-Notch, a big difference between the two. The C-Notch has a radius, V- Notch is a sharp V and Un-Notched is left unmarked. As one would expect the V-Notch has the lowest value and the Un-Notched has the highest value. Carpenters Aermet100 with V-Notch figures of 100fp are by far superior to anything else. About 2.5 times the figures of 4340.

Izodic/Charpy Impact Values are not always straight forward and clear and one really needs to know what to look for and how to "read between the lines".

I will put my balls on the line and say that the term used "Tough tool steels" are inferior where Izodic Impact is in concern to the "Mechanical engineering steels" even of the 4340, Hy-tuf, EN25, EN26, EN-30B etc. and lets not even think of the Aermet family of steels. The fact with any steel is that, as the hardness increases the Izodic Impact decreases.

Shoot better
Peter
 
The chart I have from Lone Star Heat treating listed that a a V Notch, not a C Notch. It could be a missprint.
Not to be arguementative, as I know you have good credentials in this matter, but your last paragraph concerning 'tough tool Steels' is exactly where S7, in particular, does shine. It's sole purpose for existence is retain superior ductility at higher harness values.........jackie
 
Jackie, I believe it's a missprint

jackie schmidt said:
The chart I have from Lone Star Heat treating listed that a a V Notch, not a C Notch. It could be a missprint.
Not to be arguementative, as I know you have good credentials in this matter, but your last paragraph concerning 'tough tool Steels' is exactly where S7, in particular, does shine. It's sole purpose for existence is retain superior ductility at higher harness values.........jackie
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I'ld be comfortable to say that's a missprint as I believe that it would be C-Notch Values. MatWeb and Crucible list the S7 as about where I would expected it to be. (below the 20fp mark) or about the same as AISI H 11.

Something here what is supporting my claim is also the content of Carbon 0.55% and the Chromium 3.5%. Both these elements are detrimental to the steel toughness. That's why the relatively "high" 1.4% content of Molybdenum. The Manganese and Vanadium to decrease the size of the grain and increase the toughness.
The higher content of the Chromium and the Carbon would also improve weare/abrasion, but also decrease the toughness.

There is no way that the chemical composition of the S7 could ever have the V-Notched Impact properties claimed by Lone Star. Like S7 at 170fp and the 4340 only at 20-40fp.

Shoot better
Peter
 
I agree.

I agree. The 170 fp at 48 Rc sounds like a Charpy "C" or "U" notch result instead of a "V" notch result.

I'm not familiar with the Flexor trade name - can anybody post some more info on this material (or family of materials).

The Aermet materials are certainly top-of-the line steels with incredible mechanical properties.

SteveM.
 
Yeh

That has to be a miss print.
Although I would expect it to be a little better than what is indicated.
But the facts do not lie. What makes S7 perform so well in some departments is certainly a detrement in others.
Being a "lay person" in this, I have a feeling that what is considered ductility in steels such as 4340, Flexor, (actually a brand name), and some of the precipitating hardenning stainless steels is different than that in the Tool Steels. How, I can't expalin.
Here is a good example. We use large stagger toothed round cutters to cut keways in large shafts on out horizonal boring mill. They have a 1.250 bore and a 1/4 inch key. A regular key will shear under the force exerted on the cutter. But, take a piece of Rex 95, (I know this is an entirely different type of "tool steel"), and it works fine. Hit that piece of Rex 95 with a hammer, it will break like glass.
It will stand a constant force, but not an "impact".
Maybe I am not making sense here, but do you understand what I am trying to convey. Being a metalurgist, you can certainly give us some good info on how all of this stuff works, and does not........jackie
 
Thanks Peter for shedding some light on this.

Often times, people (even "metalurgists") read charts on steels and don't take in ALL the information. (not implying you Peter) There's tricks if you will in the text that's printed. Take for instance, "S7 - Shock Resisting Tool Steel". A person reads that heading and thinks, WOW, this stuff is really great at taking shock. What is it used for? Then reads the application data and sees, it's great for pneumatic tools and die punches, etc. Then it says this material is superior to ALL other tool steels in impact and fatigue resistance.

The word there people didn't read is superior to all other TOOL steels. NOT superior to all other steels by any stretch of the imagination.

What S7 is superior at is holding shape under repeated load. However it is not an ideal choice when subjected to yield level stress repeatedly. Tool steels as a rule are not happy when subjected to yield level stress. One reason is that they tend not to yield, they tend to fail. The way to address that issue in die making is to make the part such that the individual areas of the part never reach yield levels. (In other words, make stuff beefier and apply radii correctly). By doing this you can bring load levels to a point where the steel really shines. Those in the die making industry know that a common warranty on a die set is to guarantee it for a million parts. That warranty isn't given in confidence just by selecting steels. It's done by eliminating stress levels beyond the design specs of the steel. Many times simply by using more steel.

Jackie, I also have had people question MY actions suitability. There's no fix for that other than probably just start loosing more. Then they won't care. In my case, I was questioned about fatigue of my actions. I have 1.625" diameter actions with round lugs, Military Spec (used for military helicopter rotor bolts) 4340 steel that's 100% certified content (every piece) with lugs that are .850" long and I'm questioned by a person shooting a POS Remington. Furthermore, I HAVE tested bolts TO DESTUCTION, twice... (something I bet not many people here , including some action mfgrs can say) and had to make parts wrong in order to see a failure. (A2 head on a bolt with no draw cycle) Even then, it was not a safety issue. This is why I posted earlier that much of the problem stems from ignorance, which we all have in different areas I guess.
 
4Mesh

I had a good conversation with Jim Borden today, and it was very enlightenning. I have also been having conversations with my Metalurgist.
After having these conversations, I see nothing to disagree with in your last post........jackie
 
4Mesh-100% score.

4Mesh said:
Thanks Peter for shedding some light on this.

Often times, people (even "metalurgists") read charts on steels and don't take in ALL the information. (not implying you Peter) There's tricks if you will in the text that's printed. Take for instance, "S7 - Shock Resisting Tool Steel". A person reads that heading and thinks, WOW, this stuff is really great at taking shock. What is it used for? Then reads the application data and sees, it's great for pneumatic tools and die punches, etc. Then it says this material is superior to ALL other tool steels in impact and fatigue resistance.

The word there people didn't read is superior to all other TOOL steels. NOT superior to all other steels by any stretch of the imagination.

This is why I posted earlier that much of the problem stems from ignorance, which we all have in different areas I guess.
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Phil

You'r absolutely 100% correct and that's where always the problem starts.

When I somewhere else here mentioned , "that one has to know how to correctly interpret these values by be able to read between the lines" You done exactly that. That's exactly what it means.

I couldn't have said it better than you did Phil, 100% score.

For all those who are still to defend the term a " Really tough tool steel" it's about like the term a "Really tough eggshell". It only applies to the other eggs and nothing else as even a brittle nutshell will break the toughest eggshell.

Even the metalurgists and the engineers fall for this far too often. The ignorant it is.

Shoot better
Peter
 
Phil and Peter

Thanks for the right on perspective.

Another item that is often missed is that the textbook values for 4140 and 4340 address only the "standard" method of heat treat and quench. there are many variations to that.

Strong, tough, resilient and ductile are all relative terms and each material has be looked at for its intended applications. In the case of a rifle bolt--strain to shear to failure modes need to be investigated when selecting a material.

Jim
 
Jim I agree 100%

Jim Borden said:
Thanks for the right on perspective.

Another item that is often missed is that the textbook values for 4140 and 4340 address only the "standard" method of heat treat and quench. there are many variations to that.

Strong, tough, resilient and ductile are all relative terms and each material has be looked at for its intended applications. In the case of a rifle bolt--strain to shear to failure modes need to be investigated when selecting a material.

Jim
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Jim

Without going to a "material overboard"

A simple, abundant material 4340 would be hard to beat in virtually every aspect, such as cost, availability, material property information, mechanical properties, low temperature toughness etc.

Where rifle bolts/actions are concern using 4340 and austempering (an Interupted quench) at 350*C for 5-6 hours would take care of all those even the most demanding mechanical concerns.

4340 in the same hardness would have

0 - 1% higher UTS
5-10% higher YTS
5-10% higher Impact value

Austempering also will offer better more controlled range of hardness from piece to piece and parts also can be made 2-3HRC harder and still have the same Impact value.

It's a pity that some Custom action makers are persistant in using some materials that aren't even suitable for bolts and actions. 4340 even in the so called "standard" hardenned condition has mechanical properties that will put shame on virtually every other material used by Custom action makers.

I'm not to hold my breath to expect a change to this, as an ignorance is a very strong habit.

Shoot better
Peter
 
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