Increasing Safety Requirements Demand Stronger Steel

With an increasing awareness about car safety – governments and regulatory agencies have been passing stricter safety regulations for autos. At the same time, consumers began demanding better protections, and car makers began building safer vehicles. While there are many factors to consider in building a safer car – airbags, seatbelts, glass type – the crashworthiness, or structural integrity, of the car’s body frame is one of the most critical.

In 1975 the average vehicle was manufactured with 55.9% mild steel and just 3.6% medium and high strength steels. By 2007, the percentage of medium and high strength steels used in an average car had increased by more than 230%. In the seventies, steel companies simply did not have the technology to make the steel that they can produce today because while it was strong, it was brittle and difficult to work with. Today, innovations in steel technology have given car makers the ability to use a variety of advanced high-strength steels (AHSS) that exceed 1,000MPa – meaning it can withstand more than 100 kilograms-force per square millimeter – because they are both strong and formable.

To demonstrate how far we come in terms of building stronger, safer vehicles, watch this crash test performed by the IIHS for their 50th anniversary with a 1959 Chevrolet Bel Air and a 2009 Chevrolet Malibu.

POSCO GIGA STEEL, the Industry’s New Standard for Strength and Formability

With a tensile strength of more than 1,000MPa, POSCO GIGA STEEL falls in the strongest categories of steel available to auto manufacturers today. In addition to providing the strength needed to meet safety regulations, POSCO GIGA STEEL is also ideal because of its formability and processability.

While recent years have seen ultra strength steels come on to the market with tensile ratings above 1,000MPa, these have often been rigid and brittle, making them difficult to process and mold into workable parts. POSCO GIGA STEEL bridges that gap by offering an automotive steel solution with high ductility and high tensile strength. This unique technology makes POSCO GIGA STEEL a unique fit for automakers seeking materials that can be processed into complex parts while also offering the highest levels of strength and safety for consumers.

Because of the combination of both strength and formability, SsangYong Motor unveiled their new G4 Rexton SUV with a body frame that contains 63% POSCO GIGA STEEL – the highest ratio ever achieved in a body frame design. Manufacturers like SsangYong Motor can use such high ratios of AHSS because of the technological advancements that have improved its formability in line with its improvements in strength.

The body frame of SsangYong Motor’s new G4 Rexton is manufactured with 63% POSCO GIGA STEEL.

Testing the Strength of POSCO GIGA STEEL and Aluminum

As lightweighting has become a priority for car makers seeking to build more fuel efficient cars, many have been looking toward alternative materials to step in as a substitute for steel. However, while offering certain benefits in weight, these alternative materials offer tradeoffs in strength and formability. On the other hand, POSCO GIGA STEEL offers an ideal solution in terms of strength, weight, and formability for auto manufacturers that must adhere to safety and environmental regulations along with consumer demand.

To compare the strength and impact energy absorption of POSCO GIGA STEEL (CR1180TRIP) and aluminum (Al5083), researchers at the KAIST National Center for Standard Reference Data performed an experiment in which a projectile was fired at three equidistantly spaced pieces of POSCO GIGA STEEL and aluminum.

Traveling at 185 meters per second, researcher Park Myung-joon noted that “the projectile ripped through all three pieces of aluminum while not even breaking one sheet of the POSCO GIGA STEEL.” Saying, “This experiment helped demonstrate how POSCO GIGA STEEL is more than three times stronger than aluminum making it ideal for automotive applications.”

Watch the video below to see how the experiment was designed, set up, and carried out.

POSCO GIGA STEEL is seeing increasing demand with car makers as they realize the dual benefits of strength and formability. At the Seoul Motor Show last month, Renault Samsung Motors and Chevrolet both unveiled new vehicles that were made using POSCO GIGA STEEL instead of aluminum – boosting the car body’s strength and safety for passengers.

Due to POSCO GIGA STEEL’s increased strength and high formability, the new Renault Samsung QM6 was able to maintain excellent safety standards with easy integration into its production process.

POSCO GIGA STEEL is unique because it combines both strength and formability. With strength more than three times stronger than aluminum and with formability properties that allow it to be made into complex auto parts – POSCO GIGA STEEL is the most ideal solution for car makers today.

Throughout April & May, The Steel Wire will explore the uses and benefits of POSCO GIGA STEEL and what POSCO is doing to lead the industry with new automotive steel solutions.

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A Breathtaking Sound Experience, ‘Korando C’ Speaker System
For the first time in Korea, Ssangyong Motor offers the state-of-the-art sound quality through speakers with POSCO’s magnesium sheet applied, to 2015 ‘Korando C’, Ssangyong’s new automobile. The sound quality of the speaker is far beyond the quality of 6.5 inch-paper speaker, which is applied to 2000cc SUVs of default features.

As a component that plays sounds, the magnesium diaphragm of ‘Korando C’ receives electronic signals and sends out vibrations into the air. Since a diaphragm is the main component that determines the sound quality, it must be lightweight, high in rigidity and automatically dissipates resonance which is irrelevant with the genuine signal. Previously, speaker’s diaphragms were mostly created with paper materials but they were insufficient in high-tone playback due to paper’s shortage in intensity. In order to improve the audio quality, various materials have been considered for development.

Magnesium Diaphragm: the Secret of Full Spectrum Audio Performance
Magnesium sheets are evaluated as the most idealistic material for speaker diaphragms so far. Lightweight and stern, the magnesium sheet can create high-pitch yet pure sound due to the material’s expansive range of frequency. As an ultra-light material, the magnesium sheet can cover a full spectrum from a low note to a high note even with a feeble driving force. Compared to other materials, the magnesium diaphragm provides softer and richer pitch while also offering refined tone with its excellent transmissibility. Especially, the magnesium sheet is less susceptible to unnecessary vibrations that lead to an unpleasant resonance noise. As a result, the high-quality dynamic speaker device, which realizes the sound that is closest to the original tone, is obtained.

POSCO’s Magnesium Sheet behind Your Dynamic Sound on the Road
The magnesium sheets supplied by POSCO undergo the process of figuration, surface treatment, speaker manufacturing, and finally get installed in automobiles. Currently, the magnesium sheets are produced at POSCO’s magnesium plant, located in Suncheon, Jeonnam Province, where the ultra-thin warm-rolling technology is secured. As Ssangyong Motor successfully implemented the magnesium diaphragm speaker to their new ‘Korando C’, they are considering the application of the magnesium diaphragm for other automobiles in the future.

More Applications of POSCO’s Magnesium Sheet in the Auto Industry
Last September, prior to ‘Korando C’, POSCO has already conducted a joint development with Renault Samsung Motors for magnesium sheet auto parts. In fact, POSCO’s magnesium sheet was applied to ‘New SM7 Nova’, specifically where the back seat and the trunk meet, largely contributing to vehicle weight reduction. Being the world’s first case of automobile application, POSCO’s magnesium sheet reduced up to 2.2 kg by replacing the previous component of 3.6 kg with the magnesium piece that weighs only 1.4 kg. Since the outstanding quality of the magnesium sheet has been confirmed through POSCO’s current step into the automobile market, POSCO is planning to accelerate development of the magnesium sheets for television and audio in the upcoming future.