Simple Solutions That Work! Issue 10

Over the centuries the foundry industry has moved from an art & craft base to science & technology. A path that will only continue. The modern foundry man now has a far wider range of tools available, to measure and quantify the various foundry processes, but as margins get ever tighter, maintaining specification even more critical, he needs them. One area that has intrigued me is how foundry men accurately know what the metal temperature is in the ladle. This dates back to when I first started visiting foundries and, very much wet behind the ears, I would ask how they judged the metal temperature. Even then I’d worked out that this was an important point although I didn’t understand just how essential this was for maintaining the quality of the casting process. I remember being told that a skilled man could tell the temperature from the color of the metal, how it poured and from its taste. Back then, most foundries were using cupola melting and perhaps things were not quite as critical as they are now. I have to admit that “tasting the metal” left me more than a little confused. Although, over time I did think that I came to understand what they meant. Today, with electric melting being the standard, melting temperature is a known factor, but once the metal is transferred to the ladle then unknowns can start to creep in. While it is standard working practice to use a pyrometer there are a number of practical considerations that have to be taken into account. With small capacity ladles, especially lip-pour type, it’s not a problem to take a reading with the pyrometer before casting commences. Access to the ladle can easily be achieved without the operator needing to put himself in a potentially dangerous place to take the reading. However, as the ladle gets larger in size, and especially if the ladle has a cover, using a pyrometer might become more difficult. I’ve usually seen the pyrometer kept by the melt deck, which isn’t a problem if the molding line is close by but if the ladle has to travel a distance from the furnace to the molding line, perhaps changing cranes on the way, there might be a delay of several minutes from the ladle being filled to pouring commencing. Also, the pyrometer obviously measures the temperature of the metal at the surface. It might be more useful, especially with bottom pouring ladles to know what the metal temperature is closer to the nozzle. Heraeus manufacture a range of temperature measuring equipment for foundries and steelworks and they have hit on the idea of adapting a temperature probe developed for the steel industry for foundry ladles and which addresses the above issues. While I will briefly outline their process it is the ladle aspect that is of more interest to me. So please contact Heraeus directly for technical details. The Heraeus probe is mounted in the side of the ladle shell in a special holder and protrudes through the refractory lining into the metal. The probe position is usually below the center band but away from the direct metal stream when the ladle is being filled. The actual temperature probe is inserted through a refractory sleeve and fixed via a clamp arrangement on the outside of the ladle shell. The sleeve allows probes to be changed without interfering with the ladle refractory lining. The probe sends a signal to a static receiver unit via radio transmitter and can give a continuous temperature measurement from the ladle. So the ladle has full free movement and the operator can check the temperature as the ladle advances along a molding line. Several ladles can be used with the same display, with each probe having its own log in code. 19 Continued on next page HOW TO