A kind of cake-shaped grain deep-drawing dual-phase steel plate and preparation method thereof

Abstract

The invention discloses a cake-shaped crystal grain deep-draw double-phase steel plate and a preparation method thereof, belonging to the field of a metal material rolling technology. The cake-shaped crystal grain deep-draw double-phase steel plate comprises the chemical components by weight percent: 0.01-0.05% of C, 0.1-0.4% of Si, 1.2-1.7% of Mn, 0.1-0.4% of Cr, 0.03-0.07% of Als, 0.003-0.006% of N, less than or equal to 0.02% of P, less than or equal to 0.01% of S and the balance of Fe and unavoidable trace impurities. The preparation method of the steel plate comprises the steps of firstly, smelting raw material and refining the raw material in a heating steel ladle; casting the refined raw material into a plate blank by continuous casting, and then carrying out hot rolling on the plate blank; carrying out acid pickling and then rolling the plate blank into a sheet by cold rolling; carrying out cover annealing, cooling to the room temperature and then carrying out continuous annealing; finally, carrying out overaging treatment and cooling the product to the room temperature to obtain the cake-shaped crystal grain deep-draw double-phase steel plate. Compared with a piece of equiaxed grain double-phase steel with the same performances, the cake-shaped crystal grain deep-draw double-phase steel plate has better stamping forming property. Compared with the existing deep-draw double-phase steel, the cake-shaped crystal grain deep-draw double-phase steel plate is low in production cost, higher in practicability and better in plate shape and surface quality.

Description

Technical field: [0001] The invention belongs to the technical field of metal material rolling, and relates to a cold-rolled deep-drawing dual-phase steel for automobiles, in particular to a cold-rolled high-strength, pie-shaped grain ferrite-martensitic dual-phase steel plate for deep drawing and its preparation method. Background technique: [0002] The development of cars with higher safety and lower fuel consumption has become a common task that the world's auto industry needs to solve urgently to cope with global climate warming and energy crisis. Studies have shown that if the weight of the vehicle is reduced by 10%, the fuel efficiency can be increased by 6% to 8%, and the emissions will be reduced accordingly. Automotive lightweight materials mainly include two categories, one is low-density lightweight materials, such as aluminum alloys, magnesium alloys, titanium alloys, and carbon fiber reinforced plastics; the other is high-strength steel and advanced high-stren...

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Problems solved by technology

[0004] Chinese patent CN102286696A discloses a method for preparing ultra-deep drawing dual-phase steel with high plastic strain ratio. The tensile grade of the cold-rolled dual-phase steel is 400-500 MPa. Higher Al, Mo, etc. are added in this method. Precious metal alloy elements increase the production cost; due to the high annealing temperature required, it is difficult to ensure the heating temperature of thick specifications in the existing continuous annealing production line, and it is not easy to produce thick specifications products

[0005] Chinese patent CN102517492A discloses a dual-phase steel plate and its manufacturing method. In this method, more noble metal elements such as Al, Mo, and Nb are added, and the production cost is relatively high; among them, C and N elements are relatively high, and B is added. During the casting process, B is easily combined with N to form coarse BN particles. During the stamping process, this particle is likely to become the source of crack nucleation and propagation, deteriorating its deep drawing performance; the C and N elements in the steel are relatively high, and its solid solution content It also increases correspondingly, thereby affecting the development of {111} favorable texture, and further affecting the r-value and deep-drawing properties of the steel; in addition, the continuous annealing process implements an overaging treatment for 100-200s at a temperature of 460-540°C. Overaging treatment at relatively high temperature and relatively long time, prone to bainite transformation, difficult to obtain martensite structure

[0006] Chinese patent CN102517492A discloses a method for preparing vanadium-containing ultra-deep drawing dual-phase steel after sub-temperature annealing. This method adds a relatively high content of Si and P, which is prone to rolling cracking during cold rolling and continuous annealing There is a danger of broken bands at the weld. During the annealing process, the high Si content is easy to enrich and form oxides on the surface, thereby affecting the surface quality of the steel strip. At the same time, Si and P are both ferrite strengthening elements, and their strengthening effect is strong. , the higher content of Si and P makes the yield ratio of the produced dual-phase steel higher

In addition, the sub-temperature pretreatment temperature is relatively high, and the steel strip is prone to bonding when the bell annealing process is used, which affects the shape and surface quality of the steel strip.

[0007] Chinese patent CN102162073A discloses a method for preparing low-carbon and low-silicon cold-rolled hot-dip galvanized dual-phase steel for ultra-deep drawing. In this method, higher precious metal alloy elements such as Cr and Mo are added, which increases production costs; The pretreatment temperature of the structure is relatively high, and the steel strip is prone to bonding when the bell annealing process is used, which affects the shape and surface quality of the steel strip

Due to the existence of a certain amount of interstitial atoms C and N in the traditional cold-rolled dual-phase steel, and the use of conventional hot-rolling and continuous annealing processes, it will be partially dissolved in ferrite before recrystallization after cold-rolling, hindering The development of recrystallization texture is prevented, and fine equiaxed ferrite is obtained, which seriously reduces its deep drawing performance

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