1. Types and Application of Ultra – high Strength Steel for Automobile
Ultra-high strength steel sheet for automotive body is mainly refers to AHSS steel, including: dual phase steel (DP), phase change induced plastic steel (TRIP), composite steel (CP) and martensitic steel (MS) and so on. This type of steel mainly through the corresponding phase change to strengthen the organizational structure, to achieve the relative ultra-high strength (intensity range of 500 to 1500MPa), and has the advantages of high fatigue strength, forming plasticity, collision absorption performance, high damping weight loss potential and low plane anisotropy.
DP Steel Advantage and Applications: No yield extension, no room temperature aging, low yield strength ratio, high work hardening index and high bake hardening value. Application for car cross-section, rail, bumper, wheel hub, suspension system and reinforced structural parts, the car inside and outside the board and other parts.
CP Steel Advantage and Applications: Fine grain, high tensile strength. Has good bending performance, high hole expansion performance, high energy absorption capacity and excellent flanging forming performance. Applied for Chassis hanger, B-pillar, bumper, seat rail, door and bumper.
TRIP Steel Advantage and Applications: The organization contains retained austenite, with good forming properties. In the process of forming the austenite will gradually change into hard martensite, which is conducive to uniform deformation. TRIP steel also has high collision absorption energy, high strength plastic product and high n value characteristics. Application for car B-pillar reinforcement plate, front stringers, bumper, car chassis, automotive structural parts and their reinforcements, as well as deep drawing of automotive parts, such as oil pan, doors, hood and so on.
MS Steel Advantage and Applications: with High yield strength ratio, high tensile strength, elongation is relatively low, need to pay attention to the tendency of delayed cracking. With high collision absorption energy, high strength plastic product and high n value characteristics. Application for Simple parts of the cold stamping and cross-section relative to a single roll forming parts of the body parts. Such as bumper, the threshold reinforcement plate and the side door of the anti-collision rod and so on.
QP steel Advantage and Applications: The martensite as the matrix phase, the use of residual austenite in the deformation process TRIP effect, can achieve a high work hardening ability. So more than the same level of super steel has a higher plasticity and forming performance. Applications as the shape of the more complex car safety parts and structural parts, such as A, B column.
Cold Rolled High Strength Auto Steel
TWIP steel advantage and applications: TWIP steel is a high austenitic steel with high C, high Mn and high Al composition. Through the twin crystal induced dynamic refinement, can achieve a high work hardening ability. TWIP steel has the ultra-high strength and high plasticity, the strength of plastic products up to 50GPa% or more. Application for Complex shape of the car safety parts and structural parts.
PH Steel advantage and appliations: Ultra-high strength (tensile strength of 1500Mpa or more), effectively improve the collision performance, body weight; Parts of complex shape, good formability, high dimensional accuracy. Applications for Safety structure, such as front bumper, A pillar, B pillar, the channel and the like.
2. Processing Technology of Ultra-high Strength Steel for Automobiles
At present, the automotive ultra-high strength steel plate production has the following special processing technology.
(1.) Custom sheet metal technology: Steel Sheet→Laser welding steel plate→Stamping sheet blank→Stamping→Stamping woks.
(2.) Stamping intelligent technology: Detects the physical quantity of the feature→Identify performance parameters→Guess the optimal process parameters→Automatically select the optimal parameters→Molding→Sample→Post-processing.
(3.) Hydro-forming technology: Hydraulic expansion of sheet metal parts are internal high pressure hydraulic molding. Sheet blank→Put the upper and lower mold edge→Hydraulic preform→Cut along the edge→Welding molding.
3. Laser molding and laser technology: The surface of the sheet is heated to a high temperature by means of a laser, while the thermal expansion of the heating zone causes the sheet to be bent in the opposite direction to the laser source, after cooling, or stamping during laser heating. Therefore, the laser molding technology is suitable for structural constraints when the tool can not be close to the case of smaller punching pressure.
4. Variable Blanking Force Technology: Different deformation characteristics of the molding stage to set a different blank holder force, you can use the material forming performance, improve the quality of parts molding, thereby improving the product pass rate.
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