Magnesium Myths vs. Facts
Parkway Addresses Reasons to Choose Magnesium
By: Matt Pohlman
Loveland, Colorado – Magnesium is the material that Buyers typically shy away from using based on insufficient facts and the lack of material knowledge. Parkway insists on myth busting these buyers’ concerns, and the company wants to shine a light on the truths of magnesium.
Myth #1: Magnesium catches fire immediately.
Fact: Many engineers have never forgotten the high school science teacher who ignited a pure magnesium strip in class. Dramatic … but not representative of an engineered alloy (mixtures of magnesium with other metals, often aluminum, zinc, manganese, silicon, copper, rare earth elements, and zirconium). By contrast, a Thixomolded part is a solid form of an engineered alloy and is much less susceptible to ignition. Magnesium alloys must be heated well past their incipient melting point of 790°F before ignition can occur at 990°F, although thin edges and fine particles are more easily ignited. It is very difficult to attain such temperatures because the thermal conductivity of magnesium allows rapid dissipation of heat. There are minor flammability issues (smaller than that of a die caster using fully molten or powdered material) with handling and casting the chipped magnesium alloy, but these are the concerns of the Thixomolding supplier, not the end user of the cast component. Once cast, the Thixomolded component is usually the last thing to ignite in a fire. Tests have shown that even in a car fire, the vehicle is consumed before magnesium parts will burn.
Myth #2: Magnesium is an exotic material with limited supply.
Fact: Many people rank magnesium with titanium as an exotic metal. In fact, it isn't even close to the price of that metal. As magnesium is the lightest of all structural metals, it forms the basis for commercial alloys that are successfully used in a wide variety of applications. It is also a plentiful element, comprising 2.7% of the earth’s crust. Although magnesium doesn’t occur in nature in metallic form, magnesium compounds occur worldwide, and commercial amounts of magnesium ores are found in most countries.
Myth #3: Yield rates of Magnesium parts are only 50%.
Fact: This statement may be true if purchasing magnesium castings offshore, but if any North American Thixomolder ran at this reject rate, they wouldn’t be in business very long. Parkway Product’s state-of-the-art magnesium Thixomolding machines, along with its highly skilled personnel, provide the same high quality castings that is expected from the company’s net shape, flash-free plastic injection molded parts.
Myth #4: The price of Magnesium is always fluctuating.
Fact: Magnesium is not a traded commodity like zinc and other metals. This unique situation, plus the abundant supply of magnesium, ensures the price remains relatively stable. Buyers are worried about the lack of magnesium supply. The world’s most common ores are carbonate, dolomite and magnesite. Double chloride carnilite forms salt deposits in natural brines, such as in the Great Salt Lake in Utah, one of the many sources of high quality magnesium for Parkway Products. The major source of magnesium is ocean water, constituting 0.13%. The world’s oceans provide a virtually inexhaustible supply of the metal.
Myth #5: Magnesium is difficult to machine and finish.
Fact: Magnesium has developed a long record of being the easiest metal to machine. It requires less power than other materials, resulting in faster speeds, heavier cuts, better surface finish and longer tool life. In addition, the fully enclosed melting of the magnesium alloy in the Thixomolding process produces castings with superior soundness and smoother surface finishes as-cast, resulting in less machining and finishing being required. Complex features can often be Thixomolded to net-shape specifications, eliminating all post-casting machining. When especially tight specs require further machining, Thixomolded magnesium parts can be machined at less cost than can any other metal. Machining magnesium parts requires no special equipment, only adherence to accepted good housekeeping machining department practices. Magnesium castings are highly receptive to a wide variety of coatings.
Myth #6: Magnesium corrodes too easily.
Fact: Thixomolding has eliminated the former corrosive effects of flux contamination found in die casting processes. New high-purity magnesium alloys provide far higher levels of corrosion resistance for mag parts, as-cast, with many components routinely used with no protective coating of any kind. Resistance to atmospheric corrosion can be enhanced by a variety of inexpensive chemical treatments commonly used for magnesium parts. When magnesium components are used in an assembly of parts, normal caveats would naturally be followed as in the case of a component produced in mild steel. The general perception is that Mg parts are prone to general surface corrosion. Under the right conditions, this is true. It is a reactive metal. But saltwater induced corrosion (for example, as simulated by the salt fog corrosion test) isn't a major factor today because current magnesium alloys are high purity. The content of critical impurities like nickel, iron and copper is strictly limited. The nickel and copper contents are kept to a minimum by careful selection of raw materials, while iron is limited by controlled addition of manganese. Today’s Magnesium alloys actually have better corrosion resistance than standard aluminum die castings.
So after looking at all of these myths, magnesium is a very dependable material to consider. Parkway offers magnesium Thixomolding where components are found to be light weight, extra strong, highly stiff, and contain a built-in EMI/RFI shielding while offering a greener alternative. Choosing magnesium as the material to mold components provide so many advantages.
For more information on magnesium, please contact Matt Pohlman at firstname.lastname@example.org
Downloadable version: Magnesium article1.docx