Excavator bucket pin material

[agen14]

I am designing a few excavator buckets for work. I'm trying to decide on the best material for the pins and the bushings. I am looking at ETD-150, however the cost is pretty high. These are for mini excavators, around 5 metric ton. Any suggestions are appreciated! The pins will be rigidly attached to the bucket bushing as shown in the picture attached.

 

[3DDave]

What's the cost if the pin fails?

From one supplier:

Why do People Choose e.t.d. 150 Steel Bar?​

Alro stocks e.t.d. 150® in round bars. This material was developed to provide manufacturers a machinable steel bar material, with in-the-bar strength, which they can use to design and produce parts that require higher levels of strength (150,000 psi min tensile and Rc 32 min hardness). Normally, to obtain strengths approximating this level, manufacturers have to specify a carbon or alloy steel heat-treated in the bar, or purchase steel in the annealed condition and quench and temper the part after machining. Engineers have often found either method a costly, time-consuming, and unsatisfactory solution. Both methods usually create additional production problems and require extra processing. Poor machinability, rejections from quench cracks, and a lack of uniform surface to center hardness problems that frequently add costs. Also, heat-treating involves materials handling, extra parts in the process, cleaning, straightening, and grinding - all problems that can be avoided when you don’t have to heat treat to obtain desired strength.

Seems like an excellent trade-off if the material is more expensive, if all other costs are lower.

 

[agen14]

What's the cost if the pin fails?

From one supplier:



Seems like an excellent trade-off if the material is more expensive, if all other costs are lower.

Thanks for the reply. My question was more focused on pin wear over time. The cost difference is as much as a factor of 3 so I feel that it is worth a bit of research.

 

[GregLocock]

I sort of doubt that UTS is the most important property of the pin material. I'd take a guess that most excavators use something designed to be hit with sledgehammers and covered in wet gravel. Somewhere between mild steel and axle steel.

 

[3DDave]

Again, add up the manufacturing costs. Almost always the material cost is a small fraction compared to material.

Other than that use 1020. It will wear out, is easy to machine, likely will break, but the material sure is cheap.

 

[TugboatEng]

What about the bushings? Shafts and bushings need to be selected as a pair. Nitronic steels make really nice bushings for poorly lubricated joints.

As an end user I don't see much difference in pin prices between 1020 steel (why are we even talking about 1020? 1040 doesn't cost more) or 17-4 PH. A $50 pin and a $100 pin to produce are going to be marked up as a $1000 or $1500 pin to buy.

 

[CWB1]

IME 4140 pins and 954 bronze bushings are common.

 

[agen14]

Thanks again for all of the replies. I think "bushings" might be misleading here. The bucket and pins will rotate together so there is not a rotating element between my parts.

The bushing in the excavator is greasable. I'll look at the suggestions here.

 

[TugboatEng]

A pin that doesn't rotate is the most difficult to lubricate.

 

[EdStainless]

You need to decide which part you want to wear.
It is going to happen someplace.
What is the easiest to replace?
That part should be the lower strength one.
For bushings on an excavator (wet and dirty) I would lean toward Nitronic 50 or 60, or a Hadfield Mn steel.
Both will work harden as you use them.

 

[TugboatEng]

Don't think about it as just wear. If these things start to corrode is that going to cause the pin to seize and be impossible to remove? From someone that works in corrosive environments, please bush every pin.

 

[SWComposites]

agreed, pins should always have replaceable bushings that are a softer material that will wear before the pins or the connecting parts.

 

[GregLocock]

Easier to replace a pin than a bushing.

 

[SWComposites]

yes, but a failed pin is worse than a failed bushing.

 

[TugboatEng]

A failed bushing, due to corrosion, makes it very difficult to replace a pin.