Chilled cast iron.

[dkwflight]

Hi
I experienced the chilled hard spots in some cast pieces.
It occurs to me the cast bits could be heat treated to remove these hard spots.
Question heat to what temp and cool slow?

Any ideas?

 

[goldstar31]

Two answers- maybe more???

You could be hitting inclusions- of carbides from scrap tooling. Well you will have people exposing the virtues of such things.#

I supposed that the only solutions are two harder things like CBN and diamond!

The other solution of actual chilling is to take it up to red heat or hotter and soak it over night.

The classic thing was a Beehive oven. Workington in Cumberland was full of them.

Does it help or should you start again?

Norman

 

[Jasonb]

I usually use a large propane torch to bring the casting upto red heat and hold it there for a good 15 mins then allow it to cool as slowly as possible. If you have an upen fire or wood burner then the casting can be placed in there and a good hot fire lit, leave it to cool in the ashes over night.

I have treated several chilled iron castings like this and then been able to drill and tap them, if it is just a flat surface that needs machining then carbide tooling usually does the trick without needing to treat the metal

The dark areas around this hole are the chilled areas

Bit of heat

And I was able to bore it out and tap for a cap