Simple Solutions That Work! Issue 17

Contact: JASON BERGMAN jbergman@eaglealloy.com 5 BASICS However, steel has other advantages like hardness and strength, and so lower volumes or thicknesses of material can provide the same or better performance, comparatively. Eagle Alloy and Eagle Precision often produce complex, thin-walled castings from different carbon and stainless steel alloys. The alloy affects the design, production process and finishing techniques used to manufacture each cast part. MELTING POINT The melting point of a material is defined as the temperature at which it changes from solid to liquid at atmospheric pressure . Melting point can be a major factor in deciding if an alloy will be possible to use for a particular product. Different alloys have different melting point ranges, as determined by the elements of their chemical makeup. For example, an alloy with a high percentage of tin or aluminum will melt at a much lower temperature than an alloy made of mostly iron and nickel. Melting point is an important consideration for metal manufacturers. Many casting facilities utilize sand casting methods like airset or shell mold casting because the non-metal molds can withstand higher temperatures required to melt steel. Aluminum, on the other hand, can be cast using reusable steel molds, since it has a much lower melting point than steel. THERMAL PROPERTIES Thermal properties include heat capacity, thermal conductivity, and thermal expansion. In manufacturing, all three properties are important factors in choosing the right alloy. • Heat capacity, also known as specific heat , is the amount of energy needed to change the temperature of a material, and is a key component of predicting casting solidification. • Thermal conductivity is defined as the rate at which heat can be transported through a material, and one thing metals have in common is high thermal conductivity. Electrical conductivity is a different property, but proportionally correlates to thermal conductivity. Metals like copper and gold, which are known as good electrical conductors, are also good thermal conductors. • Thermal expansion relates to the way metals expand upon heating and contract upon cooling. This property is especially important when designing tooling for metalcasting. Patterns and molds must be larger than the final part in order to account for shrinkage during cooling. MAGNETIC PROPERTIES Magnetic properties refer to the way in which the material responds to an applied external magnetic field . This magnetic response can be classified as diamagnetic, paramagnetic, ferromagnetic, antiferromagnetic, or ferrimagnetic. • Diamagnetic - repelled by magnetic fields • Paramagnetic - shows no magnetic order • Ferromagnetic - strongest type of magnetism • Antiferromagnetic - may exist at sufficiently low temperatures, but vanishes at/above Néel temperature • Ferrimagnetic - weak form of ferromagnetism Iron is one of the most magnetic metals, and so ferrous metals (metals containing iron) like steel also exhibit degrees of magnetism--specifically ferromagnetism. While the above properties are by no means exhaustive, they do represent many of the most important properties involved in choosing a material for metalcasting or CNC machining. At the Eagle Group, our metallurgy experts have the experience to evaluate a product's needs and based on customer input, ultimately suggest the optimal alloy for the job. We also employ an exhaustive APQP process for all new projects, which allows us to dial in exact parameters throughout the manufacturing process that lead to the best quality casting.