Need to test a pin for brittleness. 1

[Opher]

I have two lots of .059x.972in. pins made from 52100 steel. Both tempered to RC58. One lot bends almost 90deg., with pliers, before breaking. The other snaps like glass at 5-10 degrees of bend.

I need a standardized test to perform post heat treatment to test for brittleness. I was thinking some kind of shear or impact test would be quick and cheap.

 

[Ron]

A simple pendulum test, similar to the Charpy Impact test would probably be appropriate here. Granted, it would not be a "standardized" test from the industry, but it would work for relative comparison in QA/QC.

Set the pendulum to swing the same distance for each test and strike the pin at the same location on each pin. The weight and striking face of the pendulum would always be the same.

 

[Opher]

Thanks. What is the Charpy Impact Test? Where can I get info about it, preferably free.

 

[Ron]

Most "Strength of Materials" textbooks have some mention of it, there is an ASTM Standard for the Charpy Test (you can order the individual standard from ASTM (

http://www.astm.org))

or you can check with the American Society for Metals. They have good publications.

If you are near a University library, I'm sure you can get all of this free.

Ron

 

[tafe]

A simple way to check the pins would be to place each pin in a clamp and then use a piece of pipe on the end and bend them.
An alternative method is use Edddy currents to sort the material on conductivity.
What sort of heat treatment has the part had?

 

[Opher]

The pin is Heat treated, tempered to 58RC, oil quenched, in an open air over. I'm beginning to think my good pins are austempered, salt quenched and the tempering is in a controlled atmosphere oven.

Why would you austemper in salt vs. temper in oil? Austempering preserves ductility. I'm getting a sample ran now to test my hypothesis. I will still need a test method. I am leaning toward supporting the pin on the ends and applying force to the center until failure.

 

[tafe]

Drill ahole in a piece of 1" plate and stick the pin in. Put a piece of water pipe over the pin and bend carefully.
As I said before Eddy currents would very easily do the job and you can then reheat the failed parts.

 

[Jim777]

If you mount in a plate you will need to bend over a radius of approximately 1 1/2 times diameter in order to avoid a concentrating the force at one point.