Millions of motorists depend on a manufacturer’s use of high-performance automotive steel in engines, transmissions and the driveline components of their vehicles. Reliable steel is also required for automotive applications such as crankshafts, gears, bearings, hubs, axles, shafts, sleeves, torque converters and constant velocity joints.
Automotive steel can be classified in various ways. Since the terminology used to classify steel products varies throughout the world, for the sake of simplicity, we refer to the WorldAutoSteel format.
Each grade of steel is identified by metallurgical type, minimum yield strength (in MPa) and minimum tensile strength (in MPa). For example, DP 500/800 means a dual phase steel with 500 MPa minimum yield strength and 800 MPa minimum tensile strength.
Steels with yield strength levels in excess of 550 MPa are generally referred to as AHSS and sometimes also referred to as “ultra-high strength steels”, for tensile strengths exceeding 780 MPa. AHSS with a tensile strength of 1000 MPa is called “GigaPascal steel”.
Austenitic stainless steels have excellent strength combined with ductility and meet many functional vehicle requirements, but are a more expensive choice due to the alloying content and can make joining a challenge.
Recently there has been increased research for the development of a 3rd generation of AHSS, which has improved strength-ductility combinations compared to present grades. It also has the potential for more efficient joining capabilities at a significantly lower cost.
Automotive Steel Basics
Low-strength steels – Interstitial-free and Mild steels
Conventional HSS steel – Carbon-manganese, Bake hardened and High-strength low-alloy steels.
Conventional HSS steels are single-phase ferritic steels with the potential for some pearlite in C-Mn steels.
AHSS steel – Dual phase (DP), Complex-Phase (CP), Ferritic-Bainitic (FB), Martensitic (MS or MART), Transformation-induced plasticity (TRIP), Hot formed (HF) and Twining-induced plasticity (TWIP).
Uniquely lightweight and engineered to meet the challenges of stringent safety regulations, Advanced High-Strength Steels (AHSS) are sophisticated materials with carefully selected chemical compositions and multiphase microstructures resulting from precisely controlled heating and cooling processes. Various mechanisms achieve a range of strength, ductility and fatigue properties. AHSS offers a solid performance at an affordable cost.
Some types of AHSS have a higher strain hardening capacity resulting in a strength-ductility balance superior to conventional steels. Other types have ultra-high yield and tensile strengths and show bake hardening behaviour.
DP and TRIP steels have high energy absorption and are an excellent choice of automotive steel to use in the cash zones of a car. For the structural elements of the passenger compartment, extremely high-strength steels, such as Martensitic and boron-based Press Hardened Steels (PHS) improve safety performance.
Higher strength steels – Hot-formed, post-forming heat treated steels and steels designed for unique applications which include improved edge stretch and stretch bending.
Steelmor is the leading supplier and manufacturer of stainless steel in South Africa and is dedicated to supplying cost effective quality products on time. Give us a call to find out how we can help you when it comes to selecting automotive steel.