**2. Main requirements in the automotive industry as the driving forces of development**

Considering the major requirements for the automotive industry in the recent decades, the main driving forces of material developments can be clearly defined, too.

The competition in car manufacturing is extremely strong, and the requirements are often contradictory: for example, from the customers' side, more economical, safer, and higher comfort together with better performance are the most important issues. These are further increased by legal requirements as the ever-increasing rigorous environment restrictions as the reduction of harmful emissions and higher safety requirements. Some of the legal requirements are in accordance with the customers' demands; some imposes further requirements on car manufacturing. Due to the worldwide competition in car manufacturing, the automotive industry has to find the appropriate answers for these challenges. To meet all these requirements is impossible with conventional materials and conventional manufacturing methods. This is one of the main reasons that the development needs in the automotive industry are the main driving forces in material development, too.

In the fulfillment of these manifold requirements, the weight reduction has an important role: reducing the overall weight of vehicles results in lower consumption and thus less harmful emissions together with more economical vehicles and increased environmental protection. If we analyze the potential weight reduction in various parts of a regular automobile [2], it can be seen that about 45% of the total weight is covered by the body parts, chassis, and suspension elements (**Figure 1**); thus we have to focus on these components. These parts are mainly produced by sheet metal forming: this is why the sheet metal forming as a key technology has a critical role in the weight reduction of automobiles and why lightweight design principles are in the forefront of research and development in the automotive industry.

Applying lightweight design principles in the body-in-white production necessitates the application of thinner sheets; however, both the customers' demand and the legal prescriptions require higher safety. To solve these contradictory requirements, higher strength materials are needed. However, applying higher strength materials, it leads to further contradictions: increasing the strength results in the decrease of the formability. It is well known that strength and ductility (formability) have a hyperbolic relationship. Therefore, it is important to find a good compromise between strength and formability properties. This is a great challenge in material developments that will be analyzed in the next sections.

**Figure 1.** *Weight ratio of various vehicle components [2].*


**103**

their generation.

*Development of Lightweight Steels for Automotive Applications*

**3. Material development tendencies in sheet metal forming with regard** 

In the last 40–45 years, the reduction of fuel consumption led to the intensive development of new materials. These developments resulted in the widespread application of various grades of high strength steels. The origin of these developments can be traced back to the mid-seventieth, when the first micro-alloyed steels arrived to the industrial application. Since then, due to the continuous pressure on material development, several new high strength steel grades appeared and reached already the everyday industrial application. Systematic analysis of these developments can be found in several papers from various authors in the literature [3–7]. In the next sections, a systematic classification of these developments will be

Steel developments—in general and particularly for the automotive industry—may be classified in several different ways. One usual way of classification is done according to the metallurgical designation. These may be grouped into low strength steels (including mild steels, interstitial free (IF) steels), conventional high strength steels like carbon-manganese (C-Mn) steels, bake-hardenable (BH) steels, high strength low alloyed (HSLA) steels, and the newer types of Advanced High Strength Steels (AHSS), e.g., Dual Phase (DP) steels, Transformation Induced Plasticity (TRIP) steels, Twinning Induced lasticity (TWIP) steels, Complex Phase (CP) steels, martensitic (MS) steels. In recent years, new AHSS grades have been developed, for example, Extra Advanced High Strength Steels (X-AHSS) and Ultra Advanced High Strength Steels (U-AHSS), and various types of the so-called thirdgeneration AHSS steels, e.g., TRIP-aided bainitic ferrite (TBF) and Quenching & Partitioning (Q&P) or different types of NanoSteels: all these with the primary aim to provide even higher strength parameters with significantly increased formability. Another classification introduces various mechanical properties—mainly strength and formability parameters as the Ultimate Tensile Strength (UTS) and Total Elongation (TE). This type of classification is often used together with the designation of development steel generations, as well. In **Figure 2**, the well-known relationship between strength and ductility parameters is shown applying the abovementioned classification method with a graphical representation. From **Figure 2**, it may be also seen that the product of the ultimate tensile strength and the total elongation (UTS × TE) follows a hyperbolic function. The constant (C = UTS × TE) provides further possibility to classify the steel developments by

In **Figure 2**, the material group shown by gray color includes the conventional mild steels (IF and mild steels) formerly widely applied in Body in White (BiW) production in the automotive industry. The group of conventional high strength steels (colored by light blue) includes bake hardening (BH), isotropic (IS), high strength interstitial free (HS IF), carbon-manganese (C-Mn), and high strength low alloyed (HSLA) steels. Following the conventional high strength steels, an intensive development started in the steel industry in close cooperation with the automotive industry to develop different types of Advanced High Strength Steels

The development of first generation of Advanced High Strength Steels for automotive application may be regarded as the first step in this development process. DP steels, Complex Phase (CP) steels, certain types of TRIP steels, and martensitic steels (MART) belong particularly to this group. For these steels, the C constant

(AHSS) to meet the needs of lightweight automotive structures.

*DOI: http://dx.doi.org/10.5772/intechopen.91024*

**3.1 Classification of steel developments**

**to the automotive industry**

summarized.

*Engineering Steels and High Entropy-Alloys*

**development**

defined, too.

industry.

**2. Main requirements in the automotive industry as the driving forces of** 

The competition in car manufacturing is extremely strong, and the requirements are often contradictory: for example, from the customers' side, more economical, safer, and higher comfort together with better performance are the most important issues. These are further increased by legal requirements as the ever-increasing rigorous environment restrictions as the reduction of harmful emissions and higher safety requirements. Some of the legal requirements are in accordance with the customers' demands; some imposes further requirements on car manufacturing. Due to the worldwide competition in car manufacturing, the automotive industry has to find the appropriate answers for these challenges. To meet all these requirements is impossible with conventional materials and conventional manufacturing methods. This is one of the main reasons that the development needs in the automo-

Considering the major requirements for the automotive industry in the recent decades, the main driving forces of material developments can be clearly

tive industry are the main driving forces in material development, too.

in material developments that will be analyzed in the next sections.

In the fulfillment of these manifold requirements, the weight reduction has an important role: reducing the overall weight of vehicles results in lower consumption and thus less harmful emissions together with more economical vehicles and increased environmental protection. If we analyze the potential weight reduction in various parts of a regular automobile [2], it can be seen that about 45% of the total weight is covered by the body parts, chassis, and suspension elements (**Figure 1**); thus we have to focus on these components. These parts are mainly produced by sheet metal forming: this is why the sheet metal forming as a key technology has a critical role in the weight reduction of automobiles and why lightweight design principles are in the forefront of research and development in the automotive

Applying lightweight design principles in the body-in-white production necessitates the application of thinner sheets; however, both the customers' demand and the legal prescriptions require higher safety. To solve these contradictory requirements, higher strength materials are needed. However, applying higher strength materials, it leads to further contradictions: increasing the strength results in the decrease of the formability. It is well known that strength and ductility (formability) have a hyperbolic relationship. Therefore, it is important to find a good compromise between strength and formability properties. This is a great challenge

**102**

**Figure 1.**

*Weight ratio of various vehicle components [2].*
