hardening stainless-not knife related

[hardheart]

Hey, I was wondering if anyone could toss a little advice my way about trying to get a good spiral pin for use in our downhole tools at work. One of our tools has a locking arm that normally uses a roll pin at the pivot (3/32D X 7/16L) Problem for our tech is that it breaks on almost all the jobs and has to be replaced, it seems a little too brittle. We found some spiriral pins, but the metal is much thinner and very soft, tearing and warping quite easily. Is there some way we could harden these pins just a bit more, or perhaps soten the roll pins with predictable results? I don't know how much more work can be done to the steel after it's been rolled into shape. The box has s/s 302 written on it (for the spiral pins, don't know what steel the roll pins are), don't know if that's the type of stainless used or just a part number of some sort.

The pin needs to remain a point of failure in case the motor dies or something gets up under the arm downhole, it'd just be nice if it didn't fail quite so often Operable downhole temp for this tool can go just a lil' bit north of 300 F, if that has any effect.

 

[george tichbourne]

Interesting question. There are some questions to be answered before you can proceede.

What is the exact failure mode?

Does the pin simply shear or is it subject to corrosion, abrasion or heat stress before failure?

If shearing with no other problems The pin could be too soft or too small. Replacing 302 SS with a carbon steel pin would increase hardness and increase shear resistance. Increasing pin diameter would increase strength.

Corrosion before failure as in sour gas environments would dictate use of more corrosion resistant materials like monel or stellite.
These materials may not be available in a spring pin configuration.

Abrasion before failure would dictate a more abrasion resistant material like stellite, stellite is widely used a thrust washers downhole for its abrasion resistance.

Heat stress could indicate a need for monel or stellite as well.

If the more exotic material is required changing from a spring pin to a ribbed pin and driving it into place would solve the broken pin retention concerns.

If your pins are in fact 302 stainless forget about hardening them, the 300 series stainess steel will not harden.