The Shop > Metal Stuff

Oil fired crucible furnace

<< < (21/46) > >>

vtsteam:
Metal is poured. Just waiting for it to cool. Seemed to go pretty well. Mostly skimmed it in the furnace. I did give it a quick skim just before pouring while it was outside the furnace. Greensand was dry.  Riser filled, Well vented. Used thick Iron stock for the melt.  Total time from lighting furnace to pour was 1 hour 20 min. That included shutting down at 1 hour to add metal to the pot, and one time to scrape slag. Also of course making up the mold.

vtsteam:
Bit of a delay for dinner and family movie time.

So, shake out showed familiar problems. But not just similar problems, almost identical patterns of problems to a prior pour. And THAT was interesting. Take a look:

This pour:




And the earlier pour:

vtsteam:
So I'm not too upset about this one. Because it is a clue. So what is it trying to say?

Well, what am I looking at? Two sets of flaws in almost the same patterns.

The flaws appear almost entirely in  the central channel. And they don't appear in the middle of that channel, but in 2 groups either side of the center.

Now if these were gas or steam bubbles, we would expect them to be beside the channel, not in the channel itself, because they would tend to go to the highest point in  the casting. In fact it would be pretty hard to get them to stay under a ridge of sand, which is what the channel is as a mold surface.

So why are they there and why are they in the pattern they have?

Well lets try to draw them as groups on top of the photo.

vtsteam:

vtsteam:
These holes are in the flow lines going from sprue to the riser.

Why are they where they are?

The central channel sand ridge is slowing and trapping them before the freeze. These holes are slag covered bubbles. There is no way that increased sand permeability or vents are going to get rid of them. They are solids. They are lighter than the iron, so they don't appear on the bottom of the casting -- they are near the top, but the channel blocks them.

Navigation

[0] Message Index

[#] Next page

[*] Previous page