Simple Solutions That Work! Issue 12

W hen visiting an Aluminum Foundry to assist in solving their scrap problems, the first thing that I look at is the foundries melt control procedures. My goal is to take the aluminum melt out of the equation when trying to solven scrap issues. Without controling these very first steps of the process, it is difficult, if not impossible, to solve most down-stream scrap issues. BRAD HOHENSTEIN President - Porosity Solutions Course Instructor - The Foundry Way Learning Center www.PorositySolutions.com ARTICLE TAKEAWAYS: • Quality castings start with quality incoming material • Lack of basic melt control cannot be overcome later in the process • Controlling the melt is simple and yet doing so pays HUGE DIVIDENDS! FOLLOW THESE BASIC STEPS TO ELIMINATE MELT QUALITY AS A SOURCE OF SCRAP in the smelting process to ensure the raw material does not contribute to your casting scrap. Your ingot producer should follow these same procedures. • In-line Filters – Fine ceramic filters are used in process of producing ingot to remove impurities, such as oxides. Without these filters, the impurities will be put into the ingot and ultimately into your castings increasing your scrap rate. • In-line Degassing – Quality smelters degas the melt while producing the ingot. When degassing is not performed in ingot production, your incoming ingot will have a much higher quantity of hydrogen gas. This will increase your costs by creating porosity scrap or greatly increasing the degassing time of the foundry melt. • Chemistry Control – Chemical variations from lot to lot can significantly effect the mechanical properties of your casting. It is critical to know that an accurate chemical certification is supplied with each shipment. Most aluminum foundries remelt their scrap. The maximum amount of scrap used for each melt should be controlled. I’ve seen foundries which don’t allow any scrap added to the melt and others which allow up to 50%. The percentage of scrap allowed by each foundry should be based on the specifications of the casting. The larger the percentage of scrap allowed, the greater the chance of intoducing oxides and other inclusions which will reduce the mechanical properties of the casting. It’s amazing to me how the quality personel of many foundries spend the bulk of their time and money controlling operations after the casting is poured while giving only token attention to what goes on prior to pouring. I believe this is because many quality and operations folks don’t understand the criticallity of what happens before the pour. They think it takes a metallurgist to understand and control the processes prior to pouring. The good news is that contolling the melt is not that complicated. It just takes common sense foundry practices and basic foundry equipment. To ensure the melt is not contributing to your scrap issues, follow these basic steps. STEP 1 – RAW MATERIAL We’ve all heard the acronym GIGO, Garbage In – Garbage Out. This is particularly true when it comes to the aluminum selected to produce your castings. The first thing to understand here is that all aluminum ingot is not created equal. Many buyers will only look at the price. Afterall, 356 is 356 right? WRONG! You should know the source of the ingot and how it is produced. Ingot that is a 5 cents a pound cheaper could end up costing the foundry a 25 cents a pound in scrap and extra processing costs. Quality ingot producers, such as ALCAN/Rio Tinto take many steps 34