Method for preparing AZ31B magnesium alloy pressing sheet material

Technical Field

The invention belongs to the technical field of preparation of sheet material, in particular to a AZ31B magnesium alloy stamping board preparation method.

Background Art

Magnesium alloy has the advantages of light weight, specific stiffness, high specific strength, good electromagnetic shielding property and recycled by the excellent performance of a series is, in the broad attention at home and abroad, is regarded as 21 century of green metal material. As the material of the more light than the aluminum, without the magnesium is far the use value of the play its proper, has a great potential for development. The magnesium alloy plate mainly applied to aerospace and military field, the former Soviet union, Germany and the United States earlier study, is more remarkable results, mainly in the thick plate. As the automotive industry, computer, such as the instrument 3C rise of the product, adaptive light, portable and other development trends, sudden demand of the magnesium alloy. In order to improve the yield of the magnesium alloy plate, quality, research to improve the characteristic in the range set in the world. On the magnesium alloy sheet stamping and shaping process technology, no systematic study of domestic also, foreign countries also the only a small amount of research. AZ31B Sugamata the test such as cupping test of magnesium alloy, the magnesium alloy at room temperature has a lower deep-drawing ratio and Erichen value, as the temperature rises, these two parameters is accordingly increased. In 110 the when [...] , the maximum deep-drawing ratio is 1.67, the temperature rise of the 180 [...] , the maximum deep-drawing ratio can be increased to 2.2. In such studies K.Droder 200 to 250 the when [...] , AZ13B magnesium alloy deep-drawing ratio can reach to 2.52, can realize a punch forming of magnesium alloy, the magnesium alloy plate in the stamping possible for application in the industry. The Taiwan research chen Fuguo AZ31B plate forming limit, forming property value CCV, but only limited to forming property of research, no reports of the formed product. The German acedemic E.Doege AZ31B research such as hot forming performance of the plate. 200-250 the when [...] , limit drawing ratio βmax= 2.52. At the same time pointed out that, during the stamping process of magnesium alloy plate, to the heating of the mold, and provide the analog part of the stamping photos. Chongqing University research of the magnesium alloy plate, and anisotropic texture, texture rolling magnesium alloy plate mainly plane texture-based plate texture. Cold-rolled after, the base is inclined in the rolling direction, the direction of the plastic is obviously improved. In the electronic industry, the magnesium alloy plate punching technology to produce the cell phone, television, computer and compared with the corresponding die casting product, the higher advantage of a quite thin and productivity. The pressing member therefore magnesium alloy has good application prospect, development magnesium alloy plate punching and its associated technology has important theoretical significance and social benefit. However, because the magnesium alloy crystal structure is hexagonal close-packed (Hcp), plastic is poor, forming difficulties, low yield, the magnesium alloy adds the people flammable, such as no corrosion resistance of erroneous understanding of the disadvantages of the, lead to deformation of the stamping magnesium alloy plate has not been large-scale applications, deformation magnesium alloy and forming process research also is not full. Deformation of the plate of the magnesium alloy, and the profile of the forging in aviation, space and military fields, there is no universal to the civil field. In saving resources and reduce pollution of the social requirement, deformation magnesium alloy is requested of the sustainable development strategy, there is an urgent need of changing concepts, expedite the study, the application in the civil field.

The magnesium alloy stamping plate at the time of rolling the problem to be solved:

(1) magnesium alloy has a close-packed hexagonal structure, less than 225 the when [...] , plastic deformation of the plane {0001} is limited to <1120>{1012} slip and the conical surface <1011>Gemella. Its low-temperature deformation only three geometric sliding system and two independent sliding system. The cold-rolling of the magnesium alloy poor performance, easy to crack.

(2) conventional magnesium alloy in the stamping process of the pressing sheet material are often prone to cracking, fold, collapse and other phenomenon, the scrap product is caused. These stamping process factors, it is more, the situation is more complicated, need for in-depth research.

Content of the invention

In order to solve the above-mentioned defect of the prior art, the purpose of this invention is to provide a good formability at room temperature, when the cold is not easy to crack, AZ31B high yield method for preparing magnesium alloy punching plate.

To achieve the above object, this invention adopts the technical proposal that the AZ31B magnesium alloy stamping board preparation method is realized according to the following steps: 1, the stamping plate preparation: adopt AZ31B magnesium alloy flat spindle, flat spindle in the box-type electric resistance furnace for homogenization treatment, the treatment temperature is the 420-450 [...] , thermal insulation 18 hours; 2, plate rolling: rolling process is of the plate: flat spindle → face milling → grinding → heating → hot-rolled → cold-rolled → annealing → performance detecting → finished product, wherein (1) the temperature of the hot rolling the 450-460 [...] , hot-rolling pass for deflection 15-20%, the finishing temperature is 300 ± 10 the [...] , the heating temperature is the 430-450 [...] , the holding time is 1-1.5 hours, repeated, until the plate thickness is 1-2mm ; (2) cold-rolled utilizes a plurality of small deformation amount is rolling, passes the deformation amount is about 5%, of the total cold-rolled deformation quantity is controlled in a 25% the following, the thickness of the finished sheet material 1.0-1.5 mm ; (3) annealing process: in 260-300 the recrystallization annealing [...] , control the heat preservation time 60-90 minutes.

The beneficial effects of the above technical scheme: AZ31B magnesium alloy the deformation is mainly is gemella, sliding of the two forms. Deformation temperature of less than 300 a when [...] , gemella in the plastic deformation plays a certain role in, as the temperature rises, the proportion of water is increased, and to provide the dynamic re-crystallization nucleation conditions. In 250-450 the deformation temperature range [...] , magnesium alloy deformation of the dynamic re-crystallization occurs. According to this, the best of the magnesium alloy in the deformation temperature 300-350 the range [...] , low deformation resistance, good plasticity, is easy to shape. AZ31B magnesium alloy in mid-temperature deformation, form a local dynamic re-crystallization organization-the organization "necklace" shape, as the distortion temperature raise, "necklace" shape organization less or disappears gradually. The deformation under high temperature, dynamic re-crystallization is homogeneous. When the heat deformation temperature is higher than 450 the when [...] , deformed grain obviously grows up. The AZ31B magnesium alloy flat spindle to homogenization treatment, eliminate component segregation, even organizations, improves the forming property of the magnesium alloy flat ingot, its metallographs organizations see Figure 1, is improved in terms of the source AZ31B the forming performance of the magnesium alloy plate. Rolling the plate in the temperature in the 300 or more of rolling [...] , has very good plastic, is able to be used in the deformation amount of the rolling pass. When the rolling temperature lower than the 300 after [...] , plastic drop of the plate, when in the cold-rolled, the first deformation of the 5% left and right, the total deformation should be 25% within, edge cracking can be avoided. AZ31B plate of cold-rolled after microhistological memory in a large number of dislocation and twin crystal organization, so that its strength is improved, but plastic but significantly reduced. In order to obtain the best overall mechanical properties, need to adopt the appropriate annealing process for processing, of eliminating deformation organizations, comprehensive mechanical property improvement. Table 1 annealing AZ31B the mechanical property of the plate

Table 1   annealing AZ31B the mechanical property of the plate

As can be seen from the table, the cold-rolled after annealing comprehensive mechanical performance is remarkably improved.

As shown in Figure 2, 3 respectively of the magnesium alloy plate after being cold-rolled after the 260 [...] and 350 the annealing treatment [...] , are respectively heat preservation time for 10, 30, 60, 90,120 min, its typical microhistological. Through the method of the invention rolling AZ31B magnesium alloy plate, the elongation rate can be up to 18% the above, strength can be up to 270 MPa, yield strength than (σ_s / σ_b) relatively high; plastic strain ratio r value up to 1.56, high r value conducive to press forming; AZ31B strain-hardening index n of the deviation value of the, horizontal and oblique difference was not significant, in 0.163 and 0.181 between, stamping forming performance is improved. The strain-hardening index n value is improved after the cross rolling, stamping forming performance is improved.

Table 3 is AZ31B stamping property of the sheet material after rolling

Table 3     AZ31B stamping property of the sheet material after rolling

Note: in the sampling direction of the said rolling direction of the 0 °, perpendicular to the rolling direction of the said 90 °, 45° to the rolling direction of the 45°.

From table 3 it can be seen in, AZ31B different state of the mechanical performance of the plate there is a large difference. Hot rolling condition is far lower than the tensile strength of the cold-rolled state of the corresponding index, however its elongation and the corresponding means than the elevation of the cold-rolled state. Note the warm rolling state of the cold-rolled state microstructure relatively close to the microscopic structure. The hot rolling condition on the difference between the direction of the tensile strength is not large, but the transverse elongation only 7-10%, far lower than the rolling direction and oblique elongation, note AZ31B magnesium alloy hot-rolled sheet has a large plastic anisotropic. Cold-rolling the hot-rolled state than high tensile strength index close to 70 MPa, but its elongation than the hot rolling condition indicators low, the main reason is that after the cold rolled sheet material, the organization of the deformation is formed in a large number of twin crystal, the dislocation density is very large, the strength index is greatly improved, but plastic index is reduced many. To improve the mechanical property of cold-rolled sheet annealing must be carried out, in the annealing process the tissue deformation of the return or re-crystallization, reduce the dislocation density, improving the overall mechanical performance, improve the plate punching performance. Through this method of rolling the AZ31B board cupping, reaming, drawing and bending simulation forming performance test, the thickness is 1-2mm plate limit bulging height is 4.90 mm; limit of the average motoring pilothouse 5.70% ; 1st time limit deep-drawn coefficient is 0.788, drawing ratio of 1.268, the minimum relative bending radius r_min/t is about 5.0. So AZ31B magnesium alloy pressing sheet material of good formability at room temperature, when the cold is not easy to crack, the yield is high.