US, Chinese Automakers Increasingly Use Magnesium as Vehicle Body Material

The material used for car bodies is still primarily steel. However, efforts are being made to further reduce weight by using multi-materials combining aluminum and magnesium. Magnesium is not widely used in Japan in contrast to some automakers (OEMs) elsewhere who are actively increasing its use. FOURIN has conducted an interview with Mikio Kubo, the representative of the Japanese office of Meridian Lightweight Technologies, a major magnesium manufacturer regarding the advantages and challenges of using magnesium for car bodies and the effects of the intensity of adopting magnesium on the Japanese automobile industry. Magnesium is the lightest structural metal. It is 40-60% lighter than steel and 25-35% lighter than aluminum. Therefore, its strength per specific gravity is also high. In addition, thin and large products can be easily made from magnesium by die casting. Other features include high vibration damping and 100% recyclability. When magnesium is used for automobile parts, parts having a higher strength and weight ratio can be produced compared to those made of resins and aluminum. Moreover, double overlay required when making from steel is not necessary for integral molding. A large outer panel can be molded with a tact time of about one and a half minutes. Focusing on these advantages, non-Japanese OEMs have actively adopted magnesium. In particular, Ford uses magnesium from the 2004 model year (MY) for the front-end structure and seat frame of the F150 pickup truck which is the automaker’s most sold model. The F150 with magnesium components has already entered the third generation, during which the assembly process and galvanic corrosion compatibility have been simplified. Galvanic corrosion occurs when steel and magnesium are in direct contact with each other and are exposed to salt water. Eliminating this issue has been simplified thanks to accumulated experience. For example the 2017 MY of the F150 uses aluminum washers as insulation to prevent corrosion. With close cooperation with OEMs, magnesium parts, their assembly and galvanic corrosion prevention have made remarkable progress in the last 15 years.

Magnesium: US, Chinese OEMs Increase Adoption / Corrosion Compatible / Simplified Assembly Process

Based on an interview with Mikio Kubo (Japan office, Meridian Lightweight Technologies) and his lecture at Automotive World Nagoya (Nagoya City, Aichi Prefecture, Japan) on January 17, 2019)

Meridian Lightweight Technologies

Meridian Lightweight Technologies (Meridian) is originally based in Canada and has a history of over 30 years. In 2013, it was acquired by Wanfeng Auto Holding Group, the world's largest aluminum wheel manufacturer becoming a member of the group. Within the group, Meridian is in charge of magnesium and aluminum die-cast (high-pressure casting) products (90% of which are made of magnesium). Meridian has seven manufacturing sites around the world and employs approximately 2,000 people. The head office, R&D headquarters and main factories are located in Strathroy, Ontario, Canada and Eaton Rapid, Michigan, USA. In addition, there are facilities in Mexico (aluminum products only), the UK and China.

Meridian’s magnesium products

Meridian is not simply providing magnesium castings. What Meridian is offering is weight reduction. Based on this policy, the company supplies magnesium parts to automakers and parts makers around the world. Meridian’s end users are automakers, and its magnesium die cast products are almost 100% auto parts. Looking at supplies, direct supply to automobile manufacturers accounts for about 45%, while the other about 55% go to Tier 1 parts manufacturers. By region, North America accounts for about 75%, Asia (mostly China) for about 17%, and Europe for about 7%. In particular, sales in China have been increasing recently. Meridian began manufacturing magnesium die casts in the 1980s. The company’s strength is that it owns about 80 large die-casting machines from 500t to 4,500t worldwide. In addition, it excels at large die-cast machines over 2,500 tons compared to competing manufacturers. Meridian can do everything from mold design to process design in-house.

Locations of Meridian Lightweight Technologies

In addition, the parts design itself can be done in-house. This is because Meridian, who is familiar with the characteristics of magnesium, needs to support customer design. Furthermore, Meridian provides support from machining to parts assembly according to customer needs. In other words, Meridian is a company that provides full service from design to assembly of magnesium products.

Advantages of magnesium

Magnesium is an abundant resource on earth. According to its Clarke number, which estimates the proportion of elements near the surface of the Earth, it is the eighth most abundant element on our planet. Seawater is used for refining magnesium ingots. Therefore, there is no risk of exhaustion as a resource. Magnesium is the lightest structural metal. It is 40-60% lighter than steel and 25-35% lighter than aluminum. Therefore, the strength per specific gravity is also high. Another advantage of magnesium is that thin-walled and large products can be easily made by die casting. Other features include high vibration damping and 100% recyclability. Magnesium alloys with different properties, such as high strength, high temperature strength, elongation and toughness, can be purified.

Advantages of magnesium parts production

When magnesium is used for automobile parts, parts having a higher strength and weight ratio can be produced compared to those made of resins and aluminum. In addition, an integral shape that is not governed by the bonding strength is feasible. Moreover, double overlay required when making from steel is not necessary for integral molding. As is well known, the die-casting method is a method when molten magnesium is poured into a mold and the mold is removed when the magnesium is solidified. A large outer panel can be molded with a tact time of about one and a half minutes. High-pressure die casting can provide higher dimensional accuracy than sand casting or gravity casting. Since it has a uniform surface layer, it is used as cover element for oil sealing. Surface decoration is also easy by various methods such as smooth surface or pattern surface molding, or surface texturing. Molds are generally costly, but magnesium molding has a mold life two to three times that of aluminum molding. Such a performance can be obtained without special surface treatment of the mold. The reason is that magnesium and mold steel have a low fusion property. Therefore, when it comes to mass production, the mold cost is only one-half to one-third that of aluminum.

Simplified assembly and lower costs

Just like any other parts of a car, it is naturally necessary to attach magnesium parts to other parts or to the car body. For instance with bolts. When steel is bolted, a square nut or a weld nut is welded onto a steel plate and then bolted. As for magnesium, joints such as bosses and studs can be integrally formed. The pilot hole can also be cast, and it is compatible with self-screw tapping and rivets, so that the cost of the connecting portion and the assembly cost can be reduced.

Magnesium: US, Chinese OEMs Increase Adoption / Corrosion Compatible / Simplified Assembly Process

Based on an interview with Mikio Kubo (Japan office, Meridian Lightweight Technologies) and his lecture at Automotive World Nagoya (Nagoya City, Aichi Prefecture, Japan) on January 17, 2019)

Application of magnesium parts

Looking back on the history of magnesium parts that Meridian worked on, there were many relatively thick parts such as transfer cases and steering columns from the 1980s to the 1990s. These can be regarded as high-value-added parts with a high unit price. Around the mid-1990s, a magnesium alloy called AM60 was used. Its use was widespread for thin-walled and large body parts. Replacing car body structural parts, which had previously been made of steel, with magnesium began around this time. These parts include the front end structure and the rear’s liftgate inner.

Front end structure

The front end structure is a part that is incorporated inside the front grille. There is an opening in the center for the radiator. The headlamps and the hood’s latch are mounted on the front end structure. This part makes the best use of the advantages of magnesium. It serves various functions while it is also light weight. A typical model which uses magnesium for its front end structure is Ford’s F150 pickup truck. Over 500,000 units are manufactured annually. Ford has been using Meridian’s magnesium front-end structure for more than 15 years for 3 generations from the 2004 MY (model year). Other models adopted the same magnesium component include the North American-made Ford Expedition, Lincoln Navigator and Tesla Model S, the UK-made Land Rover Discovery, Range Rover and Jaguar XE / XF, and the Chinese-made Porsche Panamera.

Cross car beam

When a cross car beam is produced from steel, it is a combination of about 40 fine parts. Meridian's magnesium cross car beam has a single mold which stabilizes dimensions. Using magnesium reduces weight by 5 - 6 kg compared to steel. Although the price is not exactly the same as that of steel, the same functionality can be achieved with as little additional cost as possible. As of 2019, more than 30 vehicle models use Meridian’s magnesium cross car beams. Some of the models are the North American-made Chrysler Pacifica, Jeep Grand Cherokee, Jeep Compass, Jeep Wrangler, BMW X3 / X4 / X5 / X6, Honda Pilot, Honda Ridgeline, Honda Odyssey and Acura MDX, the UK-made Range Rover, Land Rover Discovery, Jaguar F-type and Jaguar XE / XF, and the Chinese-made Mercedes GLC, Porsche Panamera, Range Rover Evoque, Jaguar XE / XF, Geely Emgrand and SAIC MG6.

Liftgate inner

The liftgate inner is a structural part inside the liftgate of a minivan or hatchback. It is molded in one step using a huge 4,500-ton mold. Magnesium liftgate inner is half the weight of steel liftgate inner. Since the liftgate is located farthest from the center of gravity of the car, reducing its weight has a great effect on improving mobility. Our clients only have to attach a resin or aluminum outer to this part by hemming or bonding. It has been used in mass-produced vehicles since around 2010. Some of the models that use Meridian’s magnesium liftgate inner are the Ford Mondeo and Chrysler Pacifica.

Seat frame

By using magnesium, the weight of the Chrysler Pacifica’s cushion frame and back frame has been reduced by 11.8 kg. The back frame is integrally molded with a safety belt seat retractor. The use of magnesium makes it possible to achieve both high strength and light weight. Apart from the Pacifica, the Ford F150 / 250 / 350 and the Lincoln MKT / MKX also use magnesium seat frames.

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