CF8M hardness/toughness
CF8M hardness/toughness
(OP)
Good day!
My company have been producing castings in CF8M and WCB material for a few years now.
The jobs in particular require a drilling and tapping operation, and this has been causing one or two issues for the machinists (in both materials).
Compared to our competitors castings, our own have regularly appeared much harder to drill and tap.
More recently, a separate machinist has complained of our 25/12 material breaking several taps.
Whenever the hardness has been checked, there has never been any difference between our own and our competitor. Is this more of a toughness problem? I have heard sulphur levels can alter machinability, but cannot see any difference between chemistry samples from our own and our competitors castings... Can anyone think of any other avenues for me to look down? Is there something inherently wrong in the way we are casting?
My company have been producing castings in CF8M and WCB material for a few years now.
The jobs in particular require a drilling and tapping operation, and this has been causing one or two issues for the machinists (in both materials).
Compared to our competitors castings, our own have regularly appeared much harder to drill and tap.
More recently, a separate machinist has complained of our 25/12 material breaking several taps.
Whenever the hardness has been checked, there has never been any difference between our own and our competitor. Is this more of a toughness problem? I have heard sulphur levels can alter machinability, but cannot see any difference between chemistry samples from our own and our competitors castings... Can anyone think of any other avenues for me to look down? Is there something inherently wrong in the way we are casting?





RE: CF8M hardness/toughness
RE: CF8M hardness/toughness
RE: CF8M hardness/toughness
I can't imagine the tooling is an issue, however, due to the fact the same tooling is used for both our castings and our competitors castings.
RE: CF8M hardness/toughness
Austentic Stainless steels tend to work harden as you progress, requiring more pressure .
Look for the right drill bit (point angle 120-135Degrees), use low speeds, a rigid drill chuck and clamp the job well. I have used coconut oil,while drilling or tapping. A Cobalt based drill bit will be helpful.
I recently drilled Hardox 550, like butter with Co drill bit and low speed.
Hope it helps.
RE: CF8M hardness/toughness
If this is a customer saying your castings are more difficult than your competitors, I would suspect that the reason they are having trouble with yours is becasue that is what they are working with now.
IME, machining problems get blamed on:
1) Material
2) Tooling
3) Drawing
In that order. And, in the case of material, the other lot, which they don't have any more of, ran without any problems.
rp
RE: CF8M hardness/toughness
RE: CF8M hardness/toughness
If you find same microstructure then its something related to your machining process.
the following microstructure will affect your machining tool life:
1. carbide precipitate.
2. Ferrite pahse transfer to sigma phase during machining due to temperature increase to the level of 650C.