Material selection for gripper jaw

[caravoy]

I'm currently using A2 tool steel hardended to 53 RC as fingers for gripping an iron ring which is cast into an aluminum part.(The fingers are attached to a three-jaw concentric gripper) The parts are between 700-700 deg. F. The fingers are about 1-1/2 wide, profiled for the ring, and serrated. The fingers got about 1-1/2 weeks of use before significant wear occured. Geometry doesn't lend itself well to carbide inserts. Any suggestions for longer life out of these jaws (material selection, etc)? Thanks.

 

[tygerdawg]

Try cooling the gripper fingers between grips. I once saw a robot used for extacting red-hot forgings. In between cycles the robot literally put its gripper into a 5 gallon bucket of water ("ssssssssssss"). Depending on your application water may not be a good idea, but maybe a vortex chiller?

Otherwise some other options:
=> H13 tool steel used for high temp / high impact forging tools
=> machined ceramic fingers

TygerDawg

 

[unclesyd]

I would try D-2 at any hardness above 58 Rc.

Then look at H-11 and H-13 as mentioned above.

 

[TVP]

High Speed Steels like M2 are tempered well above 700 F(typically 900-1050 F) to hardness levels of 60-64 HRC. A2 and D2 are Cold Work Tool Steels, meaning that they are not really suitable for applications involving elevated temperature. There are quite a number of tool steels with better wear resistance than M2, so you may want to contact a technical representative from a tool steel supplier like Timken Latrobe, Crucible, or Carpenter.

 

[unclesyd]

What got the A2 to underperform is the low hardness used with respect to wear.
We used D2 for its wear resistant properties at 600-650°F in multiple applications.
We used D2 instead of A2 as we could get a little more toughness and the lack for dimensional change is respect to other materials such as the A2, good but not as good as D2.

unclesyd's Number
There is an order of magnitude change in the wear resistance of tool steels if the hardness is Rc58 or above. The magnitude of the increase in wear resistance, like all other wear problems, is the based on the combatants, but I've found that there is always a step change in the measurable increase in wear resistant properties at this point. This approach again has to be tempered by other physical parameters required to do the job. If your application allows it keep Tool Steels above Rc 58 to get better wear resistance.

 

[btrueblood]

Unclesyd,

When using the Unclesyd Number in future documents (in similar fashion as Reynold's number (Re) or Peclet number (Pc)), is the abbreviation uS or Us?

 

[unclesyd]

I would tend to go with the Us. I'll try to find me one of the little squiggly characters that's not in use.
The definition might be one less than hard enough.