Simple Solutions That Work! Issue 10

Contact: ROD NARO rod@asi-alloys.com To date, numerous foundries have substituted Nodu-Bloc for high 9% MgFeSi or Ni-Mg alloys as an integral part of their daily production. Nodu-Bloc is used in a variety of ladle configurations, ranging from open ladles, the sandwich process or the tundish cover process. The most favorable results are obtained with ladles having a width to height ratio of 1 to 2.5. Many foundries make additions to the treatment ladle in a specific order. Typically, this involves sandwiching the Nodu- Bloc between alternate layers of magnesium ferrosilicon followed by adding up to 1% cover steel. In most cases, a lesser amount of MgFeSi is used along with the Nodu-Bloc addition, contributing some silicon units, but at a significantly reduced level. In all cases, cover steel is required to prevent alloy floatation. Magnesium recoveries typically range from 50 to 75% based on metal temperature, pouring speed and amount of cover steel. A real-life case study is foundry DI. Foundry DI is a coreless melt shop and uses 2 pressure pour channel furnaces holding and pouring various treated ductile iron grades into automated molding lines. Every weekly start- up includes a 5 to 6 ton “faded” ductile iron heel in each pressure pour furnace that has virtually no remaining magnesium left. Often referred to as “superboost” Mg treatments, Foundry DI uses one or two full 6,000 lb ladles (temperature 2650-2700oF) which contain a composite “sandwich” of alloys and cover steel in the ladle pocket to add sufficient Mg to replenish the “faded” low molten metal heel in pressure pour furnace. The following sequence of alloys used in the “superboost: 45 lbs of MgFeSi, 30 lbs of 10%Mg Nodu-Bloc, 45 lbs of MgFeSi, 30 lbs of clean, dry cover steel in the final layer. For pearlitic grades, 6 lbs of copper is added. Using this procedure, the magnesium level in the pressure pour furnace is restored to 0.040 – 0.044% Mg. The need to use "superboosts" is also required when there is a significant downtime on the molding lines such as a mechanical breakdown. However, the quantity of different alloys will vary depending on the residual magnesium content in the pressure pour. Foundry DI has used this “superboost” treatment for many years and has been able to have reliable restarts of the pressure pour furnaces for the last 8 years. In the past, a nickel magnesium master alloy was used, however, there was no requirement for nickel in their ductile iron grades. This was a major cost savings without any negative consequence. Nodu-Bloc usage has steadily increased over the past dozen years and is expected to continue it's upward climb as foundries look for cost saving production methods. Nodu-Bloc use allows simple control of final silicon and thereby enables a foundry to produce sound castings economically to the desired mechanical and chemical specifications. 53 HOW TO