There is a new term floating around the automotive industry these days: 3rd Generation Advanced High Strength Steel (AHSS). Increasingly, it is being called the future material of the automotive industry, however, many are unsure of what it really is and how it will make an impact. To answer this, we have to take a step back in time.
It all began in the 80s with so-called 1st Generation AHSS. The driving force behind their development was safety and these new steels provided automotive manufacturers and OEMs with superior strength compared to conventional steel. Today, Dual Phase steel, Martensitic steel and Complex Phase steel are the backbone of the body-in-white and those grades are still further developed and optimized by continuous improvements.
Next up was 2nd Generation AHSS. These steels, introduced roughly a decade ago, targeted a superior combination of strength and ductility. Yet, in the end, high cost and difficulties in the workshop resulted in no real commercial value today.
Now, 3rd Generation AHSS has emerged. These steels, which are still early in development, secure a substantial part of retained austenite that is transformed to martensite during forming. For instance, QP (Quenching and Partitioning) and Medium Manganese steels are considered 3rd Generation AHSS.
So, what sets these new steels apart? In a few words, ductility and improved usability compared to 2nd Generation AHSS. 3rd Generation AHSS shows an excellent combination of strength and ductility. Ductility refers to that these steels can be cold formed to more complex geometries compared to 1st Generation AHSS and they can have more ductility left in the material for the crash performance after forming. In addition, 3rd Generation AHSS could be a game changer for structural components in the body-in-white by offering the possibility for even superior strength to weight ratios as well as lower cost if they can replace more expensive solutions like aluminum profiles or hot stamped boron steels. However, the increased ductility is obtained by increasing the alloying content in the steels compared to 1st generation AHSS which is causing some challenges regarding for instance weldability, hydrogen embrittlement and liquid metal embrittlement which the steel producers are working on to solve together with the automotive OEMs.
Currently, 3rd Generation AHSS is still in the early stages of development. While some companies have already launched specific products under this classification, others, like SSAB are working to develop them further. It is important to note that, currently, it is unknown which concepts and grades will end up being the backbone of 3rd Generation AHSS. However, as the iterative work between steel mills and automotive OEMs continues to mature, common grades will emerge. In order to secure its proud history and knowledge of high strength steels, SSAB has chosen to take a market driven approach to the development. This ensures that when 3rd Generation products are launched in 2018, they will work in a robust way that truly add value to the customer.
The rise of 3rd Generation AHSS also proves something else. After thousands of years of iron solutions and hundreds of years with steel, it is still possible to develop new and innovative grades. Steel is by no means an outdated material. On the contrary, it is one that is continually being improved upon. This means that one day, 4th Generation AHSS will arise.