Steel vs Aluminum carabiner

I've read from multiple sources suggesting the use of steel carabiners or maillons for critical-cannot-break connection points, but anyone know why when aluminum biners are rated stronger? The suggestions were from modern articles and not referring to mega industry 40+kn steel. The regular steel carabiner and maillons I have are rated (25kn) which is lower than both Grivels (30kn). Is there more to it than the kn #? Feel free to point me in the direction of existing threads or websites if you know of them, my googling searching has been inconclusive. Happy climbing.

Its probably not the kn but the durability. Aluminum is softer which allows it to absorb more energy without failing, but will wear down faster due to this same property.

James Pae wrote: Its probably not the kn but the durability. Aluminum is softer which allows it to absorb more energy without failing, but will wear down faster due to this same property.

James, i am not saying this to be mean. However you are not correct here fundamentally and in the role that a material plays in a system. 

appropriately heat treated aircraft Aluminum (6060/T6 or 7000 series alum) are rigid. They are not ductile. They will snap when 3 way or torsionally loaded, or when loaded over and edge. Steel will usually survive these events. 

You never use a hardgood as an energy reducer in the system. That role is for a load reducing sling with tear away stitching (ie a screamer or absorbica) or a dynamic rope. The amount of stretch in a metal component is only relavent is it allows the object to deform without destroying itself.

Steel components will stretch considerably and deform before failure. The brittle crystalline structure of T6/T7 will deform only minimally before failure.

Steel is denser stronger and more elastic than the aluminums in use in climbing equipment. When steel carried a lower rating than its aluminum counterpart. The manufacturer is defering to the lowest necessary stamp and not the true MBS. Its quite possible for the MBS to be 2 or 3 times of an equivalent aluminum unit. Which can be problematic to even reach.

I am not a material scientist. I am using a combination anecdotal, instructional, and formal testing. I gained this knowledge (such as it is please ask josh brynes or jim titt if you want a real expert) from work in rope acess, arborism, technical rescue grip/entertainment rigging.

 I have had the benefit of several very compelling and competent equipment specialists in those fields speak at length with me about their findings both anecdotal and scientific. 

Depends on the application, but Aluminum does not have a minimum fatigue threshold. Steel does. This means any load on aluminum will cause fatigue. This is in normal cases not an issue for regular climbing, but for things like a slackline, it is an issue.

Well, I suppose each company does its own thing.
Here is a list of BD offerings in aluminium -
Black Diamond Oval Wire is rated at 23kN.
Black Diamond Oval is rated at 18kN.
Black Diamond HoodWire is 24kN
Black Diamond Oz is 20kN
Black Diamond Positron Straight is 25kN
Black Diamond Positron Bent is 25kN
Black Diamond Neutrino is 22kN
Black Diamond LiveWire is 25kN

I am going to guess that the rated strength might have something to do with construction as well.

Rob warden The space lizard wrote:

James, i am not saying this to be mean. However you are not correct here fundamentally and in the role that a material plays in a system. 

appropriately heat treated aircraft Aluminum (6060/T6 or 7000 series alum) are rigid. They are not ductile. They will snap when 3 way or torsionally loaded, or when loaded over and edge. Steel will usually survive these events.

You never use a hardgood as an energy reducer in the system. That role is for a load reducing sling with tear away stitching (ie a screamer or absorbica) or a dynamic rope. The amount of stretch in a metal component is only relavent is it allows the object to deform without destroying itself.

Steel components will stretch considerably and deform before failure. The brittle crystalline structure of T6/T7 will deform only minimally before failure.

Steel is denser stronger and more elastic than the aluminums in use in climbing equipment. When steel carried a lower rating than its aluminum counterpart. The manufacturer is defering to the lowest necessary stamp and not the true MBS. Its quite possible for the MBS to be 2 or 3 times of an equivalent aluminum unit. Which can be problematic to even reach.

I am not a material scientist. I am using a combination anecdotal, instructional, and formal testing. I gained this knowledge (such as it is please ask josh brynes or jim titt if you want a real expert) from work in rope acess, arborism, technical rescue grip/entertainment rigging.

 I have had the benefit of several very compelling and competent equipment specialists in those fields speak at length with me about their findings both anecdotal and scientific. 

I am and this is right on. Tldr: Al is super brittle.  Only benefit over steel is weight savings in most applications it's used.

Edit to add: stop worrying about kn. How you use any climbing component will far undemine its lab rating.

My understanding was that aluminum carabiners are rated to an ultimate load, whereas steel is rated to a working load (usually around 1/10th of its ultimate)

Charlie S wrote: My understanding was that aluminum carabiners are rated to an ultimate load, whereas steel is rated to a working load (usually around 1/10th of its ultimate)

Steel carabiners are also rated to maximum break strength.  You may be thinking of the working load requirements of personal protection, which is 10% of the break strength, and 5% for non life support uses, as in rigging use.  For some reason soft goods are only rated to 22kN, rather than their true break strength.

Charlie S wrote: My understanding was that aluminum carabiners are rated to an ultimate load, whereas steel is rated to a working load (usually around 1/10th of its ultimate)

Don't know about steel carabiners, but that's the situation with steel quick-links. The working load rating is on the label, (e.g. 2000 lbs for most 5/16" Stainless) but my understanding is that the breaking strength is 3-4x that.

James Pae wrote: Its probably not the kn but the durability. Aluminum will wear down faster.  

There.  Fixed it.  Eliminate the energy absorption part and he was right.  

Inb4microfractures.

Steel for wear, Alu for weight.

But, maillons by design are far stronger and ideal for things that need to stay attached.

Brocky wrote:

Steel carabiners are also rated to maximum break strength.  You may be thinking of the working load requirements of personal protection, which is 10% of the break strength, and 5% for non life support uses, as in rigging use.  For some reason soft goods are only rated to 22kN, rather than their true break strength.

Awe I think you got that a little wrong. It's 10% for overhead or life critical and 25-33% for just plain working strength.

We only use Steel Carabiners for stunts. Steel Pulleys as well and Harkin Pulleys which have a very high strength rating and Stainless Steel shackles rated for 20,000 pounds.

Another important consideration is cross loading.  A mallion is less likely to crossload in most applications than a d shaped carabiner, which typically have crossload breaking strengths around 7-8 kN.  (of note, the metolius quicklink has a crossload strength of 10 kN).

For my harness attachment point in lead rope soloing (critical single point of failure, likely to crossload) I use a metolius steel biner with 40 kN in-line strength, 15 kN in crossload strength.  It gives me warm fuzzies.

If you worry about your gear cross loading or thinking about total failure in the back of your mind you may want to find another sport.

Jeffrey Constine wrote: If you worry about your gear cross loading or thinking about total failure in the back of your mind you may want to find another sport.

You do you, boo.

Julian H wrote: I thought that all the industrial gear is rated at half the breaking strength and climbing gear is rated at breaking strength.

Since you guys like braking stuff, I thought this was interesting. Nice stretch in steel on the first one. On the second it was the thread that didn't hold the load. 8.5Kn is still strong enough to bail

 

 

Cool video! Please don't bail off quicklinks as they become a bitch to remove if they rust or are very tight.

Julian H wrote:

I don’t. I have so many old  carabiners that is more  expansive to buy  quicklinks I was thinking of giving some away. Also, I keep finding quicklinks on climbs that I remove. Not from the  anchor. 

You're doing great things, then friend. I'm on a mission to rid the world of mid-route quicklinks

Jeffrey Constine wrote: If you worry about your gear cross loading or thinking about total failure in the back of your mind you may want to find another sport.

I do worry about carabiners cross loading at critical failure points.  Here's an accident report about Tom Randall who snapped his gri-gri biner while lead rope soloing.  The only reason he survived was because he had a backup knot.

​Tom Randall Accident Report​​​

Granted, lead rope soloing isn't a common technique, but there are a lot of times in standard climbing that cross-loaded or nose-clipped biners can be a safety hazard worth worrying about.

Sam Skovgaard wrote:... but there are a lot of times in standard climbing that cross-loaded or nose-clipped biners can be a safety hazard worth worrying about.

Not really.

Harumpfster Boondoggle wrote:

Not really.

Okay, maybe not a lot, but rarely.  Enough to have it in the back of your mind.