Troubleshooting Cracked Sterling Silver Ring Castings

Question
Dear Sir,
I am having small casting unit and mainly do silver castings. Now a days suddenly shanks of the rings after casting are coming cracked from the center of sizing area and near the sprue.
Please give reasons for this and give suggestion to get rid of this problem.
Your precious suggestions will great help to us.

Thanks

Kripal Singh Shekhawat

Answer
Dear Kripal, I am grateful for the question.  I will try to provide sound knowledge, however, please realize without seeing the casting process and the metals used I must speculate as to reasons for faults in the castings.

You have previously cast many silver items.  You did not have the problem of cracks near the sprue attachment area.  Now, you do have this disturbing problem.  What could be the cause?  Several possible reasons come to my thinking.  I will tell those possible reasons for the new cracking problems and you will have to study your methods and see if any of these reasons may apply.  If not, then I do not have more to offer without being present in the casting process. Fair enough to you, Kripal, and fair enough to me? I believe this is a fair and honest approach to the answer.


1. Has the metal been used many times in castings or is fresh metal used mixed at least 50% with previously cast metal?  (I do not know the alloy of silver you are casting but over casting of the same metal always will lead to problems in surface textures and integrity of the cast metal.

2. Has the time for cooling the casting prior to removing the investment been changed?  Too sudden quenching and cooling of the castings can lead to stress in the metal and cracking.  If metal has been cast too many times without fresh metal added and the cooling is not sufficient, the problem is possibly increased.

3. Is the metal when melted for the casting being poured at the same temperature?  If the metal is being overheated, perhaps in an attempt to speed the process, overheating of the metal can also lead to defects in the castings.  Some may be apparent as shrinkage caused "cracking" or defects near the sprue area.

4. Has the sprue location or capacity changed?  Are you using the same sprue methods and size of sprue rod as before when castings were not damaged?

5. Have you changed to another alloy of silver or are you obtaining the metal from a different source? There is a possibility of new metal requiring a different casting process.  However, if the same alloy as previously, even if from a new supplier, all should be ok.

My suspicions are in possible problems of #1 and #2.


I honestly do not know if this information will assist you.  Much is trial and effort in watching each stage of the casting process carefully and noting any changes.  Something has changed.  If nothing had changed and all was the same as previously, there would be no problem.  I want you to do well and find the answer.  I want you to make fine castings with no defects.

God Bless and Peace. Thomas.  September 10, 2008  7:36pm