Kia has made some major modern breakthroughs for the new Optima and has used hot stamping to provide greater safety in the event of collisions. It also serves to cut the vehicle's carbon footprint with lowered emissions and improved fuel efficiency.
Hot stamping is used to make 150kgf ultra high tensile steel sheets. High tensile steel is heated to over 900 degrees Celsius (1,652 degrees Fahrenheit).
The steel is stamped and then simultaneously cooled. Ultra high strength body parts that are made with this new stamping method include the center filler, which supports the car body during a side impact, and the roof side rail that links the sides of the roof.
120 kgf ultra high tensile strength steel is used to make the side sill, for a larger cross section. Meanwhile, 45 kgf steel sheets are added to the inside of the center filler as reinforcement.
High tensile steel sheets were used in different areas of the car's body, boosting its strength and cutting weight. High tensile sheets of over 35 kgf account for more than 60% of the car body, while ultra high tensile steel sheets of over 60kgf are utilized in 20% of the car's body.