CN104046855A - Manufacturing method of bending-resistant high-strength aluminum-magnesium alloy - Google Patents

Abstract

The invention relates to a manufacturing method of a bending-resistant high-strength aluminum magnesium alloy, which comprises the following steps: performing an aluminum blank casting step, melting and casting 4 to 4.9 wt% of magnesium, less than 0.2 wt% of silicon, less than 0.35 wt% of iron, less than 0.15 wt% of copper, 0.2 to 0.5 wt% of manganese, less than 0.1 wt% of chromium, less than 0.25 wt% of zinc, less than 0.1 wt% of titanium, less than 0.15 wt% of unavoidable impurities and the rest of aluminum into an aluminum blank; (b) preheating the aluminum blank; (c) hot rolling the aluminum billet; (d) carrying out primary cold rolling on the aluminum blank; (e) performing intermediate annealing heat treatment on the aluminum blank to completely recrystallize and soften the aluminum blank; (f) performing secondary cold rolling on the aluminum blank; and (g) carrying out final annealing heat treatment on the aluminum blank to form the bending-resistant high-strength aluminum-magnesium alloy.

Description

Bending-resistant high-strength aluminum-magnesium alloy manufacturing method

【Technical field】

The invention relates to an alloy manufacturing method, in particular to a bending-resistant high-strength aluminum-magnesium alloy manufacturing method.

【current technology】

It is known that the work-hardening aluminum-magnesium (Al-Mg) alloy is widely used in the 3C industry that requires light, thin and small size due to its good strength and anodic treatment performance. It is known that when manufacturing aluminum-magnesium alloys, the method of increasing the amount of magnesium (Mg) is generally adopted to make the aluminum material produce processing strengthening effect during the cold rolling process, so as to increase the strength of the aluminum material. However, although the above-mentioned cold-rolled aluminum alloy (commercially called H1n, including H12, H14, H16, H18 and H19) has high strength, due to the yield strength (Y.S.) and The high ratio of Tensile Strength (T.S.) makes it easy to exceed the T.S. point and cause necking ( Necking phenomenon occurs early, that is, the aluminum-magnesium alloy will break rapidly due to lack of ductility (or elongation).

Therefore, in order to increase the ductility of high-strength aluminum-magnesium alloys, general aluminum factories usually use H3n and H2n two quenching and tempering processes. The process is briefly described as follows:

(1) H3n process: For the aluminum-magnesium alloy after cold rolling, annealing heat treatment at 150 to 180°C is applied, and this recovery (Recovery) annealing process is used to reduce the dislocation density in the aluminum-magnesium alloy to reduce Y.S./T.S. ratio, to achieve the purpose of increasing the elongation and processing performance of aluminum alloy.

(2) H2n process: Compared with the H3n process, the H2n process has no intermediate annealing process and is a direct cold rolling method, which has the advantages of accelerating the production process and saving manufacturing costs. It also uses the final annealing heat treatment to reduce the dislocation (Dislocation) density in the aluminum-magnesium alloy, so as to reduce the Y.S./T.S. ratio, and achieve the purpose of increasing the elongation and processing performance of the aluminum alloy.

In addition, it has been known from the above process that aluminum-magnesium alloys with a magnesium content exceeding 3% by weight (such as 5086, 5083, 5456, and 5182 types of aluminum-magnesium alloys), if exposed to room temperature for a long time or at 66 to 180°C Under any environment, the β(Mg2A13) phase will be precipitated on the grain boundary, and the longer the exposure time, the greater the amount of precipitation. Since β is more anodic than aluminum-magnesium alloys, once the β phase appears at the grain boundary, the aluminum-magnesium alloy will be easily damaged by corrosion. In addition, when there are fine precipitates at the grain boundaries, it is easier to cause the separation of the grain boundaries and reduce the ductility of the aluminum-magnesium alloy. Because the hardness of the precipitates is often higher than the alloy material itself, and the adhesion with the alloy material is not good, so in the forming process , micro-cracks are most likely to start at the periphery of the grain boundary precipitates, and then propagate along the grain boundaries, resulting in the failure of the alloy material to form and fracture.

In addition, it can be seen from the H3n process that recovery annealing heat treatment at 150 to 180°C will promote the precipitation of β phase on the grain boundaries of aluminum-magnesium alloys, which cannot completely solve the formability of aluminum-magnesium alloys with high magnesium content (greater than 4% by weight). Even improper annealing heat treatment will reduce the corrosion resistance of alloy materials.

In view of this, it is necessary to provide an innovative and progressive method for manufacturing high-strength aluminum-magnesium alloys with bending resistance to solve the above problems.

【Content of invention】

The invention provides a method for manufacturing a high-strength aluminum-magnesium alloy with bending resistance, which includes the following steps: (a) performing an aluminum blank casting step, adding 4 to 4.9% by weight of magnesium, less than 0.2% by weight of silicon, and less than 0.35% by weight of silicon Iron, less than 0.15% by weight of copper, 0.2 to 0.5% by weight of manganese, less than 0.1% by weight of chromium, less than 0.25% by weight of zinc, less than 0.1% by weight of titanium, less than 0.15% by weight of unavoidable impurities and the rest Aluminum and other elements are melted and cast into an aluminum blank; (b) preheating the aluminum blank; (c) hot rolling the aluminum blank; (d) carrying out the first cold rolling of the aluminum blank; (e) the aluminum blank performing an intermediate annealing heat treatment on the aluminum billet to completely recrystallize and soften the aluminum billet; (f) performing a second cold rolling on the aluminum billet; and (g) performing a final annealing heat treatment on the aluminum billet to form the bending-resistant High-strength aluminum-magnesium alloy.

The present invention uses a low cold rolling process to make the aluminum-magnesium alloy with a magnesium content of more than 4% by weight have appropriate strain energy inside. Therefore, in the subsequent annealing heat treatment process, the change in the strength of the aluminum blank is less sensitive to the annealing temperature. Therefore, When batch production is adopted, aluminum coils with a weight of 20 to 30 tons in the whole furnace can not only obtain more uniform mechanical properties, but also because the final annealing temperature is higher than the range where the β-Mg2A13 phase is most likely to precipitate at the grain boundary (66 to 180 ℃), so it is not easy to occur similar to the bending cracking or corrosion in the traditional H3n process.

【Description of drawings】

Fig. 1 shows the flow chart of the manufacturing method of the bending-resistant high-strength aluminum-magnesium alloy of the present invention.

【Implementation】

Fig. 1 shows the flow chart of the manufacturing method of the bending-resistant high-strength aluminum-magnesium alloy of the present invention. Please refer to step S11 of Fig. 1, carry out an aluminum billet casting step, the magnesium of 4 to 4.9 weight%, the silicon of less than 0.2 weight%, the iron of less than 0.35 weight%, the copper of less than 0.15 weight%, the copper of 0.2 to 0.5 weight% Manganese, less than 0.1% by weight of chromium, less than 0.25% by weight of zinc, less than 0.1% by weight of titanium, less than 0.15% by weight of unavoidable impurities and other elements such as aluminum are melted at a high temperature above 700°C, and after degassing , After removing slag and filtering and adding a fine crystal agent, it is cast into an aluminum billet with half of the continuous casting (Direct Chill Casting) equipment.

Please refer to step S12, preheating the aluminum blank, in this step, the preheating temperature is not less than 480°C.

Please refer to step S13, hot-rolling the aluminum billet. In this step, since the aluminum-magnesium alloy with a magnesium content of more than 4% by weight is a high-strength aluminum alloy, the hot-rolling temperature must be between 300 and 480°C , otherwise the too low hot rolling temperature will lead to serious edge cracking of the aluminum billet during the hot rolling process.

Referring to step S14, the first cold rolling is performed on the aluminum billet.

Please refer to step S15, performing an intermediate annealing heat treatment on the aluminum billet, so as to completely recrystallize and soften the aluminum billet. This intermediate annealing heat treatment is mainly to make the aluminum sheet reach the softened state of complete annealing (commonly known as O temper). Therefore, there is no special requirement for the annealing temperature. Generally, the aluminum alloy production factory will depend on the heat treatment of the aluminum alloy of the heat. Depending on the amount of alloy, usually the intermediate annealing heat treatment temperature will exceed 280 °C.

Please refer to step S16, to carry out the second cold rolling of the aluminum billet. In this step, the thickness reduction (Reduction) of the aluminum billet must be strictly controlled between 25 and 40%, which can be intervened inside the aluminum material Appropriate cold working dislocation (Dislocation), so that the aluminum-magnesium alloy has high strength properties. In addition, the amount of cold working dislocation within the above range is less sensitive to the change of annealing temperature. Therefore, the subsequent final annealing heat treatment temperature can have a wide range of implementation.

Please refer to step S17, performing a final annealing heat treatment on the aluminum blank to form the bending-resistant high-strength aluminum-magnesium alloy. In this step, the annealing heat treatment time is between 2 and 5 hours, and the annealing heat treatment temperature is between 210 and 250°C, so as to avoid the range where the grain boundary β-Mg2A13 phase is most likely to precipitate between 66 and 180°C, so , so that the formed aluminum-magnesium alloy has the advantages of bending resistance (high elongation), high strength, wide range of final annealing temperature and resistance to corrosion, etc., wherein the elongation of the bending-resistant high-strength aluminum-magnesium alloy is not less than 10% , while the yield strength is not less than 210MPa.

The present invention is described in detail with the following examples, but the present invention is not limited to the content disclosed in these examples.

Table 1 shows the chemical composition of the aluminum-magnesium alloy of the present invention. The main purpose of adding magnesium is to increase the processing strengthening and strength requirements of the material. The amount of magnesium added is 4.6% by weight, which is much higher than 3% by weight. Therefore, the annealing heat treatment process It is very sensitive to the precipitation of β-Mg2A13 phase at the grain boundary, and a little carelessness can easily lead to forming failure.

Table 1. The chemical composition (weight %) of aluminum-magnesium alloy embodiment of the present invention

Silicon (Si) Iron (Fe) Copper (Cu) Manganese (Mn) Magnesium (Mg) Chromium (Cr) Zinc (Zn) titanium (Ti) aluminum (Al) 0.12 0.24 0.02 0.23 4.4 0.03 0.004 0.011 the remaining

Table 2 is the test result of each quality property of embodiment. Test piece 1 shows that after the second 35% cold rolling of aluminum-magnesium alloy without any final annealing heat treatment, its yield strength (Y.S.) and tensile strength (T.S.) both exceed 400MPa, and due to Y.S./T.S. The ratio is as high as 0.95, but the elongation is only 6.5%, which does not meet the requirement of 10% lower limit of material elongation for general bending forming, so the bending forming breaks. Test piece 2 was manufactured completely according to the procedure of the present invention. After adding another final annealing heat treatment step at 240°C to test piece 1, it can be observed that the Y.S./T.S. Reduced to 0.70, so it has good bending forming performance. Test piece 3 shows that although the second cold rolling amount is within the range of the present invention, if the final annealing heat treatment is not selected properly, for example, 180°C is selected, the Y.S./T.S. ratio is still as high as 0.80, and the elongation is still lower than 10%. In addition, due to the heat treatment in the range where the β-Mg2A13 phase is most likely to precipitate at the grain boundary (240 ° C), it will lead to the formation and rapid propagation of cracks in the bending forming process and fracture.

Table 2. The test results of each quality performance of the embodiment

Note: The bending test is 90 degrees 0t

In order to prove that the present invention has broader practicability, the amount of cold rolling for the second time is reduced from 35% to 27%, and the final annealing temperature has excellent strength and Flexural properties. Comparing the test piece 2, test piece 4 and test piece 5 from the data in Table 2, it can be found that the three are very close in strength, elongation, Y.S./T.S. ratio or bending test results, confirming this The invention has the advantages of a considerable operating range and quality uniformity in the production and application of aluminum alloys. However, if the second cold rolling amount exceeds 40%, for example, a high cold rolling amount of 67% is used. From the perspective of material metallurgy, the higher the cold rolling amount, the more the material is deformed by external force, so the material has more internal deformation. High strain energy will more easily stimulate the material to undergo instantaneous recrystallization and softening during the annealing heat treatment process. This phenomenon can be observed from the comparison of the test data of test piece 6 and test piece 7 in Table 2.

Test piece 6 shows that the 67% cold-rolled aluminum-magnesium alloy has a Y.S. value of 279MPa and a high Y.S./T.S. ratio when the final annealing heat treatment is performed at 230°C, resulting in bending cracks. Test piece 7 slightly raised the final annealing heat treatment condition of test piece 6 to 240°C. Although it could pass the bending forming test, the Y.S. value dropped rapidly to 189MPa due to instantaneous softening, which could not meet the requirement that the Y.S. value be higher than 210MPa. , for aluminum alloy production plants, this 67% cold rolling process is similar to the H18 or H2n quenching and tempering process most commonly used by aluminum alloy production plants. Due to the limitation that the strength of aluminum sheets is quite sensitive to the final annealing temperature, it is impossible to produce aluminum alloys with uniform quality. The above examples prove that the method parameters of the present invention must be met in order to produce aluminum-magnesium alloys with uniform quality.

The above-mentioned embodiments are only for illustrating the principles and effects of the present invention, and do not limit the present invention. Therefore, those skilled in the art can modify and change the above-mentioned embodiments without departing from the spirit of the present invention. The scope of rights of the present invention should be listed in the claims.

Claims (8)

1. a resistance to bending high-strength aluminium-magnesium alloy manufacture method, comprises the following steps:

(a) carry out an aluminium embryo casting step, by the manganese of the magnesium of 4 to 4.9 % by weight, the silicon that is less than 0.2 % by weight, the iron that is less than 0.35 % by weight, the copper that is less than 0.15 % by weight, 0.2 to 0.5 % by weight, be less than 0.1 % by weight chromium, be less than 0.25 % by weight zinc, be less than 0.1 % by weight titanium, be less than the element melting such as unavoidable impurity and the aluminium of all the other of 0.15 % by weight and be cast into an aluminium embryo;

(b) this aluminium embryo of preheating;

(c) this aluminium embryo is prolonged in hot rolling;

(d) this aluminium embryo is carried out to cold rolling prolonging for the first time;

(e) this aluminium embryo is carried out to process annealing thermal treatment, so that this aluminium embryo perfect recrystallization and softening;

(f) this aluminium embryo is carried out to cold rolling prolonging for the second time; And

(g) this aluminium embryo is carried out to final annealing thermal treatment, to form this resistance to bending high-strength aluminium-magnesium alloy.

2. the process of claim 1 wherein that the preheating temperature of step (b) is not less than 480 DEG C.

3. the process of claim 1 wherein that the hot rolling of step (c) prolongs temperature between 300 to 480 DEG C.

4. the process of claim 1 wherein that the aluminium embryo reduced thickness amount of step (f) is between 25 to 40%.

5. the process of claim 1 wherein that the annealing thermal treatment temp of step (g) is between 210 to 250 DEG C.

6. the process of claim 1 wherein that the annealing heat treatment time of step (g) is between 2 to 5 hours.

7. the process of claim 1 wherein that the yield strength of this resistance to bending high-strength aluminium-magnesium alloy of being formed is not less than 210MPa.

8. the process of claim 1 wherein that the elongation of this resistance to bending high-strength aluminium-magnesium alloy of being formed is not less than 10%.