1. Deep drawn steel plate
Deep drawing steel plates are mainly used to meet the deep drawing performance requirements of automotive steel.
In order to meet the higher requirements for deep drawing performance of automotive steel, interstitial-free steel (IF steel) has been developed and applied in recent years. It is added with a certain amount of ultra-low carbon steel (C＜0.005%, N＜0.003%). The Ti and Nb in the steel fix the C and N atoms into carbides and nitrides, and there are no interstitial atoms in the steel. This steel has excellent formability, that is, high plastic strain ratio r value (r>2.0), high work hardening index n value (n>0.25), high elongation δ (δ>50%) and non-aging ( AI=0), this steel type can be widely used in various automotive parts that have special requirements for deep drawing properties, such as oil pans or outer panels, etc. At present, Nippon Steel uses IF steel plates and adopts continuous annealing process to produce and develop special ultra-deep drawing grade S-EDDQ steel plates. Its r value can be as high as 2.5. GNEE Steel successfully developed and produced r for the first time in the world in 1999. The steel plate has an ultra-high r-value of more than 2.9 and has been industrialized.
2. High strength steel plate
The specification range of cold-rolled high-strength automobile sheets is usually 0.5~1.2mm×800~1850mm, and the strength level is 340~1470MPa. The main varieties include bake-hardened BH steel, dual-phase DP steel and phase transformation-induced plasticity TRIP steel.
Bake-hardened BH steel is used for various covering components such as automobile door outer panels, engine hood panels, trunk outer panels and ceilings. It is an automobile panel with ideal comprehensive properties. Domestic bake-hardened BH steel plates can be divided into categories according to yield strength. For: 180 MPa, 210 MPa, 240 MPa, 270 MPa and 300 MPa and other strength levels. Bake-hardened BH steel can be divided into three categories: cold-rolled plain plate, electro-galvanized steel and hot-dip galvanized steel according to different production processes. At present, the outer panels of the new generation of domestic cars mostly use electro-galvanized bake-hardened steel sheets, and the yield strength levels are mainly 180 MPa and 220 MPa. Dual-phase DP steel is generally used for automotive parts with high strength, high anti-collision absorption capacity and strict forming requirements, such as wheels, bumpers, suspension systems and their reinforcements. With the advancement of steel performance and forming technology, Dual-phase DP steel is also used in interior and exterior panels of automobiles. TRIP high-strength steel has good formability and strong ability to absorb collision impact energy due to the phase transformation plasticity induced by the transformation of residual austenite in its structure to martensite under the action of stress and strain. It is mainly used in requirements High strength automotive parts that must be drawn and formed, such as door frames, side pillars, etc. In the practical application of cold-rolled high-strength steel plates, Japan has the fastest development. Among them, automobile outer panels σb ≥ 400 MPa, car doors and roofs σb = 340~370 MPa, automobile inner panels σb = 400~600 MPa, and automobile components σb =350~510 MPa, car door frame σb≥800 MPa.
3. Coated steel plate
In order to achieve excellent corrosion resistance, galvanized sheets are widely used in automotive panels. The production processes of galvanized sheets mainly include hot-dip galvanized sheets (GI) and electro-galvanized sheets (EG). In the application of galvanized steel sheets, different regions and manufacturers have their own usage habits. For automobile exterior panels, Japan mainly uses GA panels (zinc-iron alloy coated panels), the United States mainly uses EG panels and GA panels, and countries such as France, Italy, Sweden, and Belgium mainly use GI panels. For automobile interior panels, Japan mainly uses GA boards, Europe mainly uses GI and EG boards, and the United States mainly uses GA boards. In recent years, with the development of hot-dip galvanizing technology, the quality of hot-dip galvanized products (especially surface quality) has been continuously improved. Hot-dip galvanized products are more widely used in the automotive field, and due to the cost advantages of hot-dip galvanized products (compared to electroplating Zinc products are 10% to 20% cheaper), and there is a trend to replace electroplated zinc products in some occasions.
4. Special steel plate vibration damping steel plate is a composite steel plate composed of steel plate/resin/steel plate. The thickness of the surface steel plate is usually 0.3~1.6mm, and the middle polymer resin is viscoelastic soft resin with a thickness of 0.03~0.15mm. Vibration-damping steel plates can reduce vibration and noise caused by mechanical movement. The types include: thermoplastic resin composite vibration-damping steel plates, thermosetting resin composite vibration-damping steel plates, weldable conductive resin composite vibration-damping steel plates, and high heat-resistant vibration-damping steel plates. . Vibration-absorbing steel plates were first used in the automotive industry to manufacture engine oil pans. The oil pans not only require the plates to have good formability, but also have good vibration-absorbing properties and fatigue resistance in a usage environment of 80 to 100°C. Depending on the requirements, the surface quality of automobile sheets can be divided into surface-free steel sheets (O5) and inner sheets (O3). Cold-rolled sheets and galvanized sheets for cars have extremely strict surface quality requirements, and internal parts require Class A surfaces. (New European standard, equivalent to O3 or X level surface), the outer surface covering requires a B level surface (equivalent to O5 level or Z level surface); at the same time, there are also strict requirements for the surface roughness of the steel plate, the roughness is average It is required to control the outer surface parts to 0.6~1.2µm and the inner surface parts to 0.8~2.0µm.
