Steels for car-body applications: state of the art and future trends

In the recent years, the Automotive field is focusing on developing materials that can provide high strength with reduced weight and can be shaped to complex shapes, in order to increase the passenger comfort, safety and reduce the weight of the vehicle, since the increased weight of the vehicle leads to consume more fuel which means more emissions, this point is so important since there are regulations that are setting targets, if these targets are not met it means that the car maker will pay a fine depends on the emissions of his fleet for example the allowable CO2 emission for passenger cars is 95 g CO2/km in 2020 while in 2025 it shall be 80 g CO2/km and in 2030 it will be 65 g CO2/km in EU and the sine of each g CO2/km is 95 Euros. Due to the previously mentioned reasons there were new materials that has been introduced also the car makers starting focusing on using a combinations of material in the vehicle structure by putting the true material in the true place since the price is playing a main role so they add the materials that has a high strength in the critical places from the point of view of the safety. In this thesis a brief introduction of the steel phases and the main alloys that are used in the steel shall be covered then we will take an overview on the process route of the steel making we will discuss it in detail covering basic oxygen process, continuous casting, hot rolling, cold rolling and heat treatment. Steel performance chapter will cover some important measurements like tensile strength, r-value, , bending, hole expansion and formability limits. Then a detailed review on the Automotive steel families shall be focused on, considering their microstructure, processing and application, then we will see a detailed analyses of the material evolution to see what is the trend of each segment, carmaker and year and knowing which material is used more and we will focus also on some critical areas from the safety point of view and see which materials where used.