In most foundries, melt capacity is the big expense and overall limiting factor for production. Thermal analysis is a typical way to increase and maximize melting capacity without losing control of quality. Quality is achievable in different levels, based on the melting practice and the needs and demands of the customers.
Low-Level Quality — A very low level of required quality would be prevalent in foundries that melt everything iron, as provided by junkyards. Typically they would use inexpensive cupola melting and would not have a spectrometer lab. Some quality control for carbon content can be done by monitoring slag color, but silicon, manganese, chromium, copper, and other elements are free to wander all over the map. Here, a thermal analysis system would give the foundry a means to control silicon that could be adjusted by cupola additions, and possibly 75% FeSi additions to the ladle. Some additional information about hardening elements can be gleaned from a thermal analysis measurement of pearlite and carbides.
Moderate-Level Quality — A more typical, moderate required quality pertains to foundries that limit their incoming material to known scrap. Such foundries may have either electric or cupola melting and typically do not have problems with uncontrolled manganese, chromium or copper. For these foundries, carbon and silicon control is the main benefit of thermal analysis. A microstructure check on carbides and pearlite is less critical.
High-Level Quality — Foundries with the highest standard for quality will benefit greatly from thermal analysis, as well. These foundries have multiple levels of quality checks with cupola melting and holding furnaces, or electric melting furnaces, possibly with holding furnaces, and a full spectrometer lab with combustion analysis. Typically these foundries have one additional quality requirement—the chemistry must meet specific standards, limits and requirementsbefore the iron can be moved to the pouring line. This can add 10 -15 minutes to the melt cycle to wait for lab results. With the newer high-powered, medium-frequency furnaces, this delay can result in 20-25% lost melt capacity.
The secret here is that if the carbide stabilizers are reasonably consistent from heat to heat, then thermal analysis can evaluatethe other two elements—carbon and silicon—before the furnace gets up to temperature, is slagged, and ready to tap. The chemistrylab finishes its analysis and provides certification and feedback for the slowly changing carbide stabilizers. That extra +20% melt capacity alone could boost productivity an additional 10-15% per day and is worth a fortune to the foundry.