Simple Solutions That Work! Issue 12

This part displays “Hydrogen Porosity”. Its cause is completely different than the other 5 types of porosity. Understanding the differences is key to solving the problem. • Sponge Shrink Porosity • Gas Holes aka Air Holes • Pin Hole Porosity aka Surface Porosity or Reaction Porosity • Blow Holes Each of the above listed defects is technically a porosity defect. However, each of these defects are caused by different casting factors, each require different changes to the process to eliminate the defect, and the method of identifying each of these defects can vary. Pour temperature, mold material, coatings, hydrogen content, chill usage, chill condition, molten metal flow, mold design, molten metal additives, core condition, furnace condition, and pouring methods can all contribute to porosity formation. The foundry team must be able to identify the specific type of porosity defect and know its causes, cures, and controls. Without this knowledge, it is unlikely a permanent solution will be implemented. When you consider that these different porosity types represent only a small portion of potential casting defects, it becomes clear why expanding the knowledge base on the foundry floor is critical to a successful scrap reduction program. The good news is that institutions such as The Foundry Way Learning Center offer hands- on foundry courses specifically designed to provide the aluminum casting knowledge required to lead a successful scrap reduction program. Once training is provided to the foundry floor team, the work of solving the foundry scrap issues can begin. Most successful foundries use a structured problem-solving strategy to reduce scrap and improve their process. The following 5-Step Program is a good system for most aluminum foundries. 1. IDENTIFY THE DEFECT – The defect must be correctly identified. If identified wrong, there is no chance of success. This is why the knowledge base of the team is critical. If the team is not certain they should reach out to a foundry consultant. 2. DEFINE THE POTENTIAL CAUSES – This step should include a brainstorming session while using a cause and effect diagram (Ishikawa diagram) to track the results of the session. The cause and effect diagram forces the team to look at all potential causes, whether man, material, or method. The example diagram below is a Microsoft Excel option of the C&E Diagram. 41 BACK TO BASICS Continued on next page