MICROALLOYED STEELS FOR THE AUTOMOTIVE INDUSTRY
Two major drivers for the use of newer steels in the automotive industry are fuel efficiency and increased safety performance. Fuel efficiency is mainly a function of weight of steel parts, which in turn, is controlled by gauge and design. Safety is determined by the energy absorbing capacity of t...
| Main Author: | |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Associação Brasileira de Metalurgia, Materiais e Mineração
2014-12-01
|
| Series: | Tecnologia em Metalurgia, Materiais e Mineração |
| Subjects: | |
| Online Access: | http://www.tecnologiammm.com.br/files/v11n4/v11n4a13.pdf |
| Summary: | Two major drivers for the use of newer steels in the automotive industry are fuel efficiency and increased safety
performance. Fuel efficiency is mainly a function of weight of steel parts, which in turn, is controlled by gauge and design.
Safety is determined by the energy absorbing capacity of the steel used to make the part. All of these factors are incentives
for the U.S. automakers to use both Highly Formable and Advanced High Strength Steels (AHSS) to replace the conventional
steels used to manufacture automotive parts in the past. AHSS is a general term used to describe various families of
steels. The most common AHSS is the dual-phase steel that consists of a ferrite-martensite microstructure. These steels
are characterized by high strength, good ductility, low tensile to yield strength ratio and high bake hardenability. Another
class of AHSS is the complex-phase or multi-phase steel which has a complex microstructure consisting of various phase
constituents and a high yield to tensile strength ratio. Transformation Induced Plasticity (TRIP) steels is another class of
AHSS steels finding interest among the U.S. automakers. These steels consist of a ferrite-bainite microstructure with
significant amount of retained austenite phase and show the highest combination of strength and elongation, so far, among
the AHSS in use. High level of energy absorbing capacity combined with a sustained level of high n value up to the limit
of uniform elongation as well as high bake hardenability make these steels particularly attractive for safety critical parts
and parts needing complex forming. A relatively new class of AHSS is the Quenching and Partitioning (Q&P) steels. These
steels seem to offer higher ductility than the dual-phase steels of similar strengths or similar ductility as the TRIP steels
at higher strengths. Finally, martensitic steels with very high strengths are also in use for certain parts. The most recent
initiative in the area of AHSS is the so-called “3rd Generation” AHSS. These steels are designed to fill the region between
the dual-phase/TRIP and the Twin Induced Plasticity (TWIP) steels with very high ductility at strength levels comparable to
the conventional AHSS. Enhanced Q&P steels may be one method to achieve this target. Other ideas include TRIP assisted
dual phase steels, high manganese steels and carbide-free bainitic (CFB) steels. Finally the post hardened steels (PHS) are
an important component of the strategy of future vehicles. In this paper, some of the above families of advanced formable
and high strength steels with micro-alloying additions, utilized in the automotive industry will be discussed. |
|---|---|
| ISSN: | 2176-1515 2176-1523 |