Classification of automotive steel

Automotive steel is classified in many different ways. One is a metallurgical naming method that can reflect process information. Commonly used nomenclatures include low-strength steels (interstitial-free steels and mild steels), conventional high-strength steels (HSS, such as bake-hardened steels, low-alloy high-strength steels), advanced high-strength steels (AHSS, such as dual-phase steels, phase change-induced plastic steel). There are also higher-strength steel grades, including press-hardened steels, and steel grades designed for specific applications with improved edge elongation and tensile-bending properties. The second classification method is more important for component designers, that is, naming according to the strength of the steel. The main difference between conventional high-strength steel (HSLA) and advanced high-strength steel (AHSS) is the microstructure. Traditional high-strength steels are ferritic single-phase steels, and a small amount of pearlite may also exist in carbon-manganese steels. The essential characteristic of advanced high-strength steel is that it contains a multi-phase microstructure, that is, usually in addition to ferrite, pearlite or cementite, it also contains a certain amount of one or more other phases, such as martensite, bainite, austenite and/or retained austenite, resulting in unique mechanical properties. Certain types of advanced high-strength steels have higher strain-hardening properties and therefore have a better strength-ductility balance than conventional steel grades. Some other steel types have extremely high yield and tensile strengths and exhibit bake hardening behavior. Advanced high-strength steels include all martensitic steels and multi-phase steels, with a minimum specified tensile strength of 440MPa. These steel grades with very high minimum specified tensile strengths are sometimes called ultra-high-strength steels (UHSS). Some companies choose 980MPa as the threshold starting point for "ultra" high intensity, while other companies use higher thresholds such as 1180MPa and 1270MPa. There is no universal definition for automotive steel producers and users, and the difference between advanced high-strength steel and ultra-high-strength steel exists only at the level of terminology - as they are not two unrelated products. A fabricator's choice of forming, joining or machining methods is essentially a function of variables such as steel grade, thickness and mechanical properties. These steel grades are called "advanced" or "ultra" high-strength steels. For technology Coping has no impact.