15 May

Semco Carbon Appears in Thermal Processing Magazine!

In this article from the magazine Thermal Processing, graphite machining experts from Semco explore a couple of the most common challenges that manufacturers encounter when machining graphite components for heat treat industries. While Semco machines graphite components for many different applications, the company’s mainstay is manufacturing graphite components used in vacuum furnaces and sintering operations. With decades of experience doing this work, Semco engineers have identified two particular challenges that manufacturers of these components should be aware of in order to produce quality parts and avoid manufacturing mishaps. The first issue explored here is the challenge of measuring electrical resistance in graphite heating elements. The reliability and consistency of heating element performance depends on uniform electrical resistance throughout the element, and from element to element. Print and material spec. sheets allow manufacturers to reliably create elements with uniform dimensions, but variation in graphite materials means that even in elements of the same dimensions, performance can vary due to differences in the resistance of the material. The article explores some causes of this variation in graphite materials. The article then describes ways that manufacturers can minimize the effects of this variability to ensure consistent electric resistance in heating elements. The second issue the article explores is eutectic melting during the sintering process. While eutectic melting is a desired condition in many heat treatment processes, such as brazing, it can cause harmful bonding in the hot zone between the graphite fixtures and the materials being processed. This bonding, which often results from carbon atoms migrating from the graphite to the processed metal, thus lowering the melting point of the metal and fusing it to the graphite, can be costly and destructive. After cataloguing and providing images of several examples of eutectic bonding, the article explores several solutions to eutectic bonding for manufacturers whose hot zones utilize graphite components. These solutions include modifying the treat temperature and using insulators to separate the graphite components from the treated metal.