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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Since the inception of the auto industry, steel has been used to manufacture cars because it is strong, manufacturable, and durable. Also, because roughly 55-60% of a car’s weight comes from steel, it is an obvious place to make lightweighting a priority, which is exactly what has happened. Recent innovations in steel production technologies have created solutions that are lighter, stronger, and more environmentally friendly to produce.     

Steel Alternatives Present New Obstacles for Car Manufacturers

Advanced High Strength Steels (AHSS) provide the most eco-friendly alternative for car makers in material production. (Chart courtesy of AutoSteel)

As the auto industry adapts to new government regulations and consumer expectations, many have been looking toward alternative materials to step in as a substitute for steel. However, each material carries both benefits and drawbacks that they must constantly weigh as they seek to strike a balance that adheres to safety & emissions regulations and consumer demand.

Aluminum, magnesium, and carbon fiber composites are all being used to various degrees in recent auto designs. They have become attractive as lightweighting has become more of a priority for car manufacturers; however, there are tradeoffs.

Certain types of aluminum can be weaker, more expensive, and less formable than some steels. Magnesium, while lighter than both steel and aluminum, is also more expensive. In addition, extraction of magnesium can emit more than 20 times more carbon emissions than steel. Lastly, while carbon fiber composites offer the most in lightweighting potential, it is still prohibitively expensive for mass produced cars, and producing carbon fiber is 14 times more energy intensive than steel.

Advanced High Strength Steel Offers Lightweighting Solution

Typically, to make steel lighter, sacrifices had to be made in strength and ductility. However, recent innovations in advanced high-strength steels (AHSS) have been able to bridge that gap.  AHSS offers lightweight solutions with high ductility coupled with high tensile strengths that can go beyond 1,000 MPa – meaning it can withstand more than 100 kilograms-force per square millimeter.  

In addition, compared to alternative materials used in autos, AHSS offers the most eco-friendly option for car markers. It has the lowest production emissions and because it is infinitely recyclable and durable, it can be used in multiple applications throughout its life cycle.

AHSS grades allow car manufacturers to achieve a new level of strength, ductility, and durability in steel that is also lighter and more eco-friendly due to improved production efficiencies.

Third generation AHSS provides both high tensile strength and elongation. (Chart courtesy of World Autosteel)

The Third Generation of AHSS

Recently, engineers and researchers have been working to improve the balance between strength and elongation in AHSS. Typically, conventional mild steels offer superior elongation with less strength, whereas previous AHSS offered superior strength with more elongation and ductility.

The third generation of AHSS is bridging that gap, producing steel that is both incredibly strong and ductile at the same time. Typical mild steels have a tensile strength of around 300 MPa, which means it can withstand up to 67 pounds per force per square millimeter. On the other hand, new third-generation AHSS typically have a tensile strength of 800-1500 MPa (up to 300 pounds per force per square millimeter) with a similar amount of ductility.

In tensile strength measurements, 1,000 megapascals equals 1 gigapascal. Steel that has a tensile strength over 1,000 MPa is often referred to as GigaPascal steel. This type of AHSS is both super strong and also lightweight.

AHSS provides car makers with a lightweight, strong material solution.

GigaPascal Steel and the Future of Auto Manufacturing

GigaPascal steel represents the cutting edge of steel technology and the future of auto manufacturing. Its high strength and lightweight properties make it safe and efficient. It provides car makers the material they need to meet efficiency and safety standards, with significantly fewer production emissions.

Two weeks ago SsangYong Motor unveiled their new G4 Rexton SUV at the Seoul Motor Show. They partnered with POSCO to develop the core body frame parts using its new POSCO GIGA STEEL. The SUV was designed so that 63% of the body contains POSCO GIGA STEEL – a first for the auto industry, but not the last.

SsangYong Motor’s G4 Rexton is unveiled at the Seoul Motor Show in March 2017. It is the first vehicle to be made with up to 63% giga steel.

As the auto industry seeks to build more efficient and safe vehicles, advancements in steel technology have emerged to meet their needs. Balancing efficiency, strength, weight, and price – steel continues to be the preferred material in auto manufacturing.

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