Crampons - Aluminum vs Steel

To me, it seems 7075 is comparable to stainless steel (not sure what alloy BD uses). Still loses out to chromoly. But if SS is acceptable for BD, I'm trying to figure out why there aren't more crampons with 7075 frames.

Chromoly Steel:
Ultimate Tensile Strength, psi 97,200
Yield Strength, psi 63,100

SS316:
Ultimate Tensile Strength, psi 89,900
Yield Strength, psi 60,200

SS304:
Ultimate Tensile Strength, psi 73,200
Yield Strength, psi 31,200

Aluminum (7075):
Ultimate Tensile Strength, psi 83,000
Yield Strength, psi 73,000

(data from onlinemetals.com)

Hardness, toughness, corrosion resistance, work-ability, weight and overall cost (material and process) has a lot to do with it.

Material properties are not limited to yield strength and tensile strength. There are a lot of factors that go into it, including stiffness, fracture toughness, hardness, and others.

Crampons never (or very rarely) break in pure yielding/ultimate strength manners. It's usually related to not holding and edge (don't see many knives made from aluminum, right?), fatigue, or crack propagation.

t.farrell wrote:To me, it seems 7075 is comparable to stainless steel (not sure what alloy BD uses). Still loses out to chromoly. But if SS is acceptable for BD, I'm trying to figure out why there aren't more crampons with 7075 frames. Chromoly Steel: Ultimate Tensile Strength, psi 97,200 Yield Strength, psi 63,100 SS316: Ultimate Tensile Strength, psi 89,900 Yield Strength, psi 60,200 SS304: Ultimate Tensile Strength, psi 73,200 Yield Strength, psi 31,200 Aluminum (7075): Ultimate Tensile Strength, psi 83,000 Yield Strength, psi 73,000 (data from onlinemetals.com)

Hmmm, the numbers you are quoting are a bit simplistic (some are wrong as well).
The values for stainless are in the annealed/unworked condition, for 304/316 worked you normally expect a UTS around 160-170,000psi. The yield strength for both is effectively identical.
The stainless used for Camp crampons is Sandvik Nanoflex which gets a UTS of up to 377,000psi.
7075 is weak and relatively brittle but light so good for some things but not others. Karabiners for example have to be physically quite large so a weaker, lighter material is used, if strength/weight ratio was all that mattered they wouldn´t be aluminium.
The simple lack of toughness and hardness makes aluminium crampons only suitable for easy snow.

Jim Titt wrote: Hmmm, the numbers you are quoting are a bit simplistic (some are wrong as well). The values for stainless are in the annealed/unworked condition, for 304/316 worked you normally expect a UTS around 160-170,000psi. The yield strength for both is effectively identical. The stainless used for Camp crampons is Sandvik Nanoflex which gets a UTS of up to 377,000psi. 7075 is weak and relatively brittle but light so good for some things but not others. Karabiners for example have to be physically quite large so a weaker, lighter material is used, if strength/weight ratio was all that mattered they wouldn´t be aluminium. The simple lack of toughness and hardness makes aluinium karabiners only suitable for easy snow.

Very interesting. I have absolutely 0 experience in this area, so I just saw some numbers that looked relatively equal and made some assumptions. Sounds like there's a lot more to learn.

Jim Titt wrote:The simple lack of toughness and hardness makes aluinium karabiners only suitable for easy snow.

From context I assume you mean "The simple lack of toughness and hardness makes aluminum crampons only suitable for easy snow.

t.farrell wrote: Very interesting. I have absolutely 0 experience in this area, so I just saw some numbers that looked relatively equal and made some assumptions. Sounds like there's a lot more to learn.

Metallurgy is surprisingly complex and just when you think you understand it, something else always pops up that is gonna make you wrong again!

One good thing to know however is that as Jim mentionned, a lot depends on the way the material has been treated (heat treatments and mechanical forming) so when you see those strenght specifications for a material, it is often just an indicator but it can vary quite substantialy.

That being said, aluminium will pretty much never be better than steel in regards to an object that you bash on rocks and ice all day long. It will degrade faster for a bunch of reasons.

Xam wrote: From context I assume you mean "The simple lack of toughness and hardness makes aluminum crampons only suitable for easy snow.

You might well be correct, changed that!

Material properties are highly dependent on final processing steps, so unless you have data or specs from the OEM for the finished product, I would not bother trying to compare.

In practice, aluminum crampons do not penetrate ice as well and they wear down more quickly on rock, which is why they are typically limited to applications without hard ice or rock.