recommendations for type of stainless steel pins to manufacture

[ssylvest]

I welcome some suggestions on a metallurgy question about which stainless steels specifications would be most appropriate for some manufactured hinge pins. My project is 99% structural using carbon steel, of which I am very experienced, designing heavy industrial structures, flood walls, and flood gates. But the flood gates require some specially fabricated hinges of which the specific choices of metals is less clear to me. We have guide-specifications and example details for similar hinges from the USACE, but they note several choices, which is not obvious to me of what the pros and cons are.

For an example, the main lower hinge pin has been calculated to be 5.5” diameter and about 18” long. The guide specs and details suggest ASTM A276 with one of these as the material: UNS S 20910, or S 30400, or S 40500, or Type 431. It specified Condition A, hot-finished or cold-finished, Class C.

Which of those 4 might be the best choice and why?

In table 2 of ASTM A276, under Type 431, why does it have “…” under the mechanical properties and what does that mean?

My task is designing the structural elements and specifying the materials required (including hinge components), which will then be put out for bids to be fabricated and erected by a general contractor (and his subcontractors and shops).

 

[EdStainless]

The ellipsis (...) means that it is not specified.

What is the environment?
What is the hinge material?

Cold finished S20910 will be the strongest of the group, and still a very tough material.

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Plymouth Tube

 

[ssylvest]

EdStainless,

Regarding the ellipsis, what is the approapriate way to know or specify reaonable values if they are not specified? Why do you think they are not specified?

The environment is a steel flood gate sitting out in the weather for 50+ years, getting used seldom (perhaps once every couple of years as a large hurricane approaches).

The pin discussed will fit inside of a bushing. The buishing is proposed to be Bronze castings conforming to ASTM B22, Copper Alloy UNS No. C91300 or Type 937. It is to be fit inside of a steel tube, that the guide specification suggests A513 Type 6 (or another document suggested A53Type S Grade B seamless), with a Class 6 fit between the bushing and the outer steel tube.

The whole hinge assembly if further built up with exterior carbon steel plates and stiffener plates, welded. It has a grease fitting tapped into the zone between the pin and bushing, and shows some 1/8" grease grooves in various locations.

 

[EdStainless]

If the (...) is there then there is no specified value. Either that is not important or it is not reliable or it is not controlled.
There are a lot of 4xx series alloys with (...) for elongation, it is so low and variable that you don't bother.

This sounds like a reasonable set up.
Is there a chance of salt water exposure?
If so then I would suggest S32205 for a pin material.

If we are dealing strictly fresh water then the S20910 sounds like a good option.

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Plymouth Tube

 

[TVP]

The reason there are no properties listed for Type 431 is because it is a hardenable stainless steel, forming martensite upon quenching. It is not meant to be used in the annealed or rolled condition.

With regards to materials selection, UNS S20910 or S30400 will be more available than either of the 4xx series grades. I concur with Ed, use

S32205 if there is any salt water exposure
S20910 if fresh and you need higher strength
S30400 if fresh and low stress