Hot Spots in Mold?

[Iron Mike Golf]

Newbie caster here (less than 1500 rounds). I am working with a used SAECO 441 and my furnace is a SAECO Model 24.

I am remelting some commercial cast bullets (92/6/2 alloy). I find that this mold drops this alloy at .4315 to .4335 at a melt temp of 600-650. If I get any frosting at all on the drive bands, the bullets will be under diameter (I want to size to .431). I miked a couple of hundred bullets until I got confident about being able to eyeball for diameter based on frosting.

It takes 8-10 casts to bring the mold up to temp, even after preheating on the furnace mold shelf. Once there, I am good for several cast, then the mold gets too hot. I have tried the sprue plate on wet rag technique, which seems partly effective. It seems the side of the mold blocks closes to my hands is hotter.

I do spill over occasionally, since I have not rigged up a mold rest and am still getting a feel for when to close the valve. When it spills, it is mostly on the side of the mold nearest my hand. Is the over-spill causing uneven temp in the mold blocks? When this happens, I end up opening the blocks and blowing on the cavities for 20-30 sec and that seems to work. I keep bullets that show frosting in the bottom of the lube groove, since the drive bands seem to mike OK.

Bullets often stick and it needs one or more sharp raps with a hammer handle to free up the bullets. Do I need to re-clean the cavities? Or is it something else?

Any insights and advice about all this is very welcome!

[Le Loup Solitaire]

Hi and welcome to the forum. Your alloy ratios look good and 650F is not overly hot. I would suspect that the spill repeatedly on one side is contributing to or is responsible for the overheating and uneven frosting. I would suggest trying one of those inexpensive fans (under $10.) that are sold in Sears, Walmart etc....set it up on the "hot side" where the spill is flowing down and or your hand is feeling more heat. Those little fans are around 4" in diameter and you might want to consider one that is somewhat larger. It also keeps the fumes away and your casting zone cooler. One or two sharp raps on a mold is not a lot of wear and tear; if it has to go beyond that then there may be another kind of prob. Usually a rap or two to the handle hinge does the job, but if necessary a shot of mold release usually helps. Mold cavities should be kept clean anyway and a pass or two with a brush regularly ought to do that. You don't want crud or inclusions in the cavities. Molds are fussy people with their own personalities that have to be coddled sometimes. Keep on asking questions; someone will always try to help you with any problem. Search the many articles and stickies and keep reading on the subject. It looks like you are off to a good start...keep up the good work. LLS

[oso]

Yep, I'm familiar with this problem. You might want to look at the Shrunken Bullet Syndrome article at Mountain Molds.com: http://mountainmolds.com/shrunken.htm

[KYCaster]

Is this a two cavity mold? Does the frosting show up first on the parting line where the cavities are closest?

If that's the case then the problem is too much heat. 650 is a reasonable casting temp., so I suspect the mold is getting to hot. I've never noticed spilling over to cause any unusual localized over heating...and I get pretty sloppy at times. :roll:

I suggest slowing the casting cadence or more aggressive cooling between casts. In addition to cooling the sprue plate, try cooling the bottom of the mold on the damp rag.

Localized shrinkage is sometimes caused by poor venting. Check out the "Leementing" stickie in the molds maintenance section, it will tell you how to improve venting.

Good luck
Jerry

[HangFireW8]

Yep, I'm familiar with this problem. You might want to look at the Shrunken Bullet Syndrome article at Mountain Molds.com: http://mountainmolds.com/shrunken.htm

LOL... that article reminds me of, me. I know all about the problem, except how to fix it quickly. I can fix it slow, but that fix applies only to that mold. [smilie=b:

I think there's multiple causes. One cause is a cavity venting into a still-molten poured cavity. Another is "too hot". Another is "too cold". Exactly which is too hot or cold (melt versus mold), "depends". haha I agree that good venting helps in all cases.

How's that for clarity?

I agree with another point in the article, Lyman #2 and Linotype are very user friendly. Try to tell some of the regulars here that, and they'll start talking about "tin poisoning" and "expensive waste" and blah blah blah.

I've got tin coming out my ears, while WW are getting harder and harder to find. I'm not afraid to use it if I have to.

-HF

[Calamity Jake]

Try using 2 molds at a time, it will help control mold temp. Plus you get the benefit of double the output.

[Walter Laich]

could also touch the top of the mold, after the lead has hardened (solidified sp?) to a wet rag for a second or two. I can get longer casting sessions doing this.

+1 Using two molds also helps the overheating of the mold

[peerlesscowboy]

Sounds like the same problem I posted about last week? You might be interested to read "Multiple Large Cavities", Mike.

John C. Saubak

[onondaga]

Some changes in casting cadence and pour method should cure the localized hot spot you are getting.

Mold temperature can get too hot at any practical casting alloy temperature if your cadence is too rapid. Dropping the pot temp 25 degrees would help to some degree if your mold is getting that hot also.

Most important is that hot spots are the definitive symptom of turbulence in the flow during the pour. Some molds will cause turbulent back flow and uneven cooling with frost spots if a dead center flow from the pour spout is used. The metal back-washes in turbulence and cuts off the airflow out as the metal flows in.

The simple cure for this is to pour a little differently. A mold guide would help, but you can try without one also. Adjust your distance that you hold the mold under the spout so your flow is 1/4 to 1/2 inch long. Pour with the flow 1/2 the diameter off center into the sprue gate hole while your mold is tipped about 5 degrees to the right or left.

The off center pour and tilted mold setup a swirl of the alloy into the mold and allow the air to escape very efficiently as the mold is filled. This is called 'Swirl Casting". It is an excellent overall method for casting and is the classic cure for casting into molds that are finicky and produce hot spot, cold spot or uneven fill due to flow turbulence or venting problems with some particular designs. Swirl casting is also very effective into molds with no vent cuts.

Gary (retired casting analyst)

[Iron Mike Golf]

Thanks for all the tips. Lots of things to try.

I am thinking about opening up the sprue gate holes a tad. It's much smaller than the ones on the Lyman and RCBS molds I have. I don't think I can swirl cast as it is. If my flow is too fast now, more alloy splashe out of the sprue funnel than seems to go in.

Maybe because of that I end up filling the cavities too slowly and the alloy cools improperly?

[onondaga]

Yes, metal splashing or gurgling at the sprue gate hole is definitely a sign that turbulence is causing you a problem.

I took some measurements to give you a comparison in sprue gate holes. I have a Lyman .223 mold and the gate hole measures .140 inches. My .458 Lee gate holes measure .162". The flow on my pot is adjusted to about 80% of the smaller of the two gates by appearance or approximately.112 inches in diameter. That is a fine stream compared to what I have seen others cast at. I do adjust the flow adjustment on my Lee 4-20 pot usually 2 times and sometimes 3 times from full pot to very low pot alloy level as I cast a potful of alloy.

If your pot is a Lee 4-20 I suggest you adjust your flow before you cut the sprue gate holes. If your flow is broad and fast it could be the culprit that is giving you grief with any type of casting method.

You will likely be surprised at how slow and fine you can adjust the flow stream and still get good mold fill and fill out if your mold temperature is in good casting temperature range.

Gary

[Iron Mike Golf]

I have a SAECO 24 and I will adjust the flow down. I have been controlling it by hand and eye so far.

[Lloyd Smale]

this will more then often happen when casting high tin content alloys like #2 or lineotype. Sometimes just using a alloy with less tin will help. Its one time extra tin doesnt help fillout.
Is this a two cavity mold? Does the frosting show up first on the parting line where the cavities are closest?

If that's the case then the problem is too much heat. 650 is a reasonable casting temp., so I suspect the mold is getting to hot. I've never noticed spilling over to cause any unusual localized over heating...and I get pretty sloppy at times. :roll:

I suggest slowing the casting cadence or more aggressive cooling between casts. In addition to cooling the sprue plate, try cooling the bottom of the mold on the damp rag.

Localized shrinkage is sometimes caused by poor venting. Check out the "Leementing" stickie in the molds maintenance section, it will tell you how to improve venting.

Good luck
Jerry