A low-cost high-strength fast-degradable magnesium alloy and a preparation method thereof

Abstract

The application belongs to the technical field of metal materials, and provides a low-cost high-strength fast-degradable magnesium alloy and a preparation method thereof.The magnesium alloy is composed of the following components according to the mass percentage: 1-15% of zinc, 0.1-1% of calcium, 0.5-7% of nickel, and the balance of magnesium, and unavoidable impurities ≤0.02%.The preparation method of the magnesium alloy comprises the following steps: batching, smelting, homogenization, artificial aging or annealing-rolling-annealing.Compared with the magnesium alloy obtained by the prior art, the magnesium alloy is prepared by synergistic regulation of alloy components, proportioning, process and process parameters, the composition, size and distribution of the second phase of the magnesium alloy are changed, and the grains are refined, so that the galvanic corrosion is strengthened, the corrosion shielding effect of the second phase is weakened, the high mechanical properties and the degradation rate are realized, and finally the low-cost high-strength fast-degradable magnesium alloy is obtained.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of high-performance metal material synthesis, and particularly relates to a low-cost high-strength fast-degradable magnesium alloy and a preparation method thereof. BACKGROUND

[0002] With the gradual decrease of oil and gas resources in China, in order to improve the production of oil resources, the oil field exploitation turns to the difficult-to-exploit rock oil and gas reservoir. Multistage fracturing technology is widely used in the exploitation of rock oil and gas, and in the process of oil and gas fracturing, it is necessary to block the horizontal well pipe to improve the pressure of the horizontal well, and the fracturing ball and the bridge plug are the key downhole tools. As a key tool, the fracturing ball needs to have high strength to meet the blocking requirement. After oil and gas exploitation, the fracturing tools are usually removed by the pressure difference in the well or by mechanical drilling, which is time-consuming and laborious, and is not suitable for all horizontal wells. The debris generated in the process of mechanical removal also pollutes the oil and gas layer and affects the quality of oil and gas exploitation. Therefore, the fracturing material needs to have high degradation rate and environmental friendliness, so that it can dissolve in the flowback fluid after the construction is completed. Therefore, how to save raw material cost, simplify process conditions, and obtain an environmentally friendly alloy with high liquid pressure resistance, high strength, high temperature resistance and high rate of solubility (degradability) in the process of mechanical removal is a technical problem to be solved at present. SUMMARY

[0003] In order to solve the above technical problems, the present application provides a low-cost high-strength fast-degradable magnesium alloy, which is composed of the following components in mass percentage: zinc 1-15%, calcium 0.1-1%, additive elements, unavoidable impurities ≤0.02%, and the balance of magnesium. The additive element is nickel, and the nickel is 0.5-7%. The preparation method thereof comprises the following steps:

[0004] (1) The required metal raw materials are weighed according to the mass percentage, and the surface oxidation products are removed for use. SF6 and CO2 are mixed in a volume ratio of 0.2-1.5:98.5-99.8 to serve as a protective gas, pure magnesium is added, and then the temperature is raised to 400-460℃ for 10-30min, then the temperature is raised to 500-560℃ for 0.5-2h, then the temperature is raised to 650-710℃ for 0.5-2h, then pure zinc, magnesium-calcium intermediate alloy and magnesium-nickel intermediate alloy are added, and then the temperature is raised to 675-700℃ for 5-15min under argon protection, stirring for 1-5min, refining and slagging for 1-5min, and then pouring to obtain a magnesium alloy ingot;

[0005] (2) The magnesium alloy ingot obtained in step (1) is subjected to gradient homogenization heat treatment under argon protection, and then quenched in water to room temperature to obtain a homogenized magnesium alloy ingot;

[0006] The gradient homogenization heat treatment is: holding at 250-320 DEG C for 1-4h, then holding at 310-360 DEG C for 5-7h, and then holding at 330-410 DEG C for 3-6h.

[0007] (3) the homogenized magnesium alloy ingot obtained in step (2) is subjected to artificial aging or annealing-rolling-annealing treatment, and then is air-cooled to room temperature to obtain a low-cost high-strength fast-degradable magnesium alloy;

[0008] The artificial aging is: holding at 140-210 DEG C for 3-7h;

[0009] The annealing-rolling-annealing treatment is: annealing at 220-320 DEG C for 10-40min, then rolling at 100-200 DEG C for 5-12 passes, holding at 220-320 DEG C for 10-40min after each pass, rolling speed is 10-25r / min, total rolling reduction is 70-90%, and then annealing at 220-320 DEG C for 20-60min.

[0010] Further, the zinc is 1.5-12%, and the calcium is 0.2-0.5%.

[0011] Further, the nickel is 1-5%.

[0012] Further, the gradient homogenization heat treatment in step (2) is: holding at 280-300 DEG C for 2-3h, then holding at 325-350 DEG C for 5.5-6.5h, and then holding at 345-400 DEG C for 4-5h.

[0013] Further, the artificial aging in step (3) is: holding at 150-200 DEG C for 5-6h.

[0014] Further, the annealing-rolling-annealing treatment in step (3) is: annealing at 250-300 DEG C for 15-30min, then rolling at 120-180 DEG C for 6-11 passes, holding at 250-300 DEG C for 15-30min after each pass, rolling speed is 15-20r / min, total rolling reduction is 75-85%, and then annealing at 250-300 DEG C for 30-50min.

[0015] Compared with the prior art, the present application has the following advantages through the synergistic regulation of the interaction, ratio, process and process parameters of alloy components:

[0016] (1) The prior art has the problems that: the prior art improves the strength and corrosion resistance by adding rare earth elements or increasing the alloy addition amount or complex process, that is, when the alloy strength is improved, the corrosion resistance will also be improved, which will lead to a decrease in the degradation rate, that is, it is difficult to simultaneously improve the alloy strength and the degradation rate. However, in the case of reducing the cost and simplifying the process by not adding rare earth elements and reducing the alloy addition amount, the present application effectively controls the composition and proportion of low-cost elements, and cooperatively optimizes the process and process parameters, so that good mechanical properties and high-temperature resistance are obtained, and the degradation rate of the magnesium alloy is significantly improved, and the magnesium alloy has good environmental protection, and is suitable for the field of fracturing magnesium alloy.

[0017] (2) The present application forms second phases such as Mg2Ni and τ(MgZnNi), increases the voltage difference between the second phase and the α-Mg matrix, increases the galvanic couple, and enhances the cathode hydrogen evolution reaction, thereby realizing the effect of strengthening the galvanic corrosion and reducing the corrosion resistance of the magnesium alloy, thereby increasing the corrosion rate and the degradation rate. The problem of the prior art is that the types of second phases in the obtained alloy are complex, and the low-melting-point second phases are not uniformly melted in the solid solution process. However, the present application solves the above problems and effectively realizes the solid solution of alloy elements into the matrix, the continuous distribution of the second phase in the grain is crushed into broken second phase, the original network structure of the second phase is destroyed, the corrosion barrier effect of the second phase is weakened, and the degradation rate is improved. At the same time, the grain is refined, the organizational uniformity is improved, and finally the mechanical properties, high-temperature resistance and degradation rate of the alloy are improved.

[0018] (3) Compared with the prior art, the present application uses different preparation processes under the condition of reducing the types and mass of alloy additions and simplifying the process. The mechanical properties and high-temperature resistance of the alloy obtained by the present application are better than those of the alloy obtained by the prior art. In addition, the high degradation rate of the alloy obtained by the present application at room temperature and high temperature is significantly better than that of the alloy obtained by the prior art, that is, the alloy obtained by the present application simultaneously realizes high mechanical properties, high-temperature resistance, and high degradation rate at room temperature and high temperature.

[0019] In summary: the optimal mechanical properties, high-temperature resistance, and high degradation rate at room temperature and high temperature of the alloy obtained by the present application are realized by the synergistic control effect of the interaction between the components of the alloy, the ratio, the process and the process parameters. DETAILED DESCRIPTION

[0020] Example 1

[0021] Taking Mg-12Zn-0.5Ca-3Ni alloy as an example (the component mass percentage is: Zn: 12%, Ca: 0.5%, Ni: 3%, the total content of unavoidable impurities is ≤0.02%, and the balance is magnesium), the preparation method of the alloy is as follows:

[0022] (1) Take the required metal raw materials by mass percentage, remove the surface oxidation products for standby, mix SF6 and CO2 as protective gas according to the volume ratio of 0.5:99.5, add pure magnesium, heat to 450℃ for 15 min, then heat to 550℃ for 1 h, then heat to 695℃ for 1 h, then add pure zinc, magnesium-calcium intermediate alloy, magnesium-nickel intermediate alloy, heat for 8 min, then stir for 2 min under the condition of 695℃ and argon protection, refine and slag for 2 min, then pour to obtain magnesium alloy ingot;

[0023] (2) The magnesium alloy ingot obtained in step (1) is subjected to gradient homogenization heat treatment under argon protection, and then water quenched to room temperature to obtain a homogenized magnesium alloy ingot;

[0024] The gradient homogenization heat treatment is: heat at 280℃ for 3h, then heat at 325℃ for 6.5h, and then heat at 345℃ for 5h;

[0025] (3) The homogenized magnesium alloy ingot obtained in step (2) is subjected to artificial aging treatment, and then air cooled to room temperature to obtain a low-cost high-strength rapid degradation Mg-12Zn-0.5Ca-3Ni magnesium alloy;

[0026] The artificial aging is: heat at 175℃ for 5.5h.

[0027] Example 2

[0028] Taking Mg-1.5Zn-0.2Ca-1Ni alloy as an example (the component mass percentage is: Zn: 1.5%, Ca: 0.2%, Ni: 1%, unavoidable impurities total content ≤0.02%, and the balance is magnesium), the preparation method of the alloy is as follows:

[0029] (1) Take the required metal raw materials by mass percentage, remove the surface oxidation products for standby, mix SF6 and CO2 as protective gas according to the volume ratio of 0.6:99.4, add pure magnesium, then heat to 440℃ for 16 min, then heat to 540℃ for 1.1h, then heat to 690℃ for 1.4h, then add pure zinc, magnesium-calcium intermediate alloy, magnesium-nickel intermediate alloy, heat for 9 min, then stir for 3 min under the condition of 690℃ and argon protection, refine and slag for 3 min, then pour to obtain magnesium alloy ingot;

[0030] (2) The magnesium alloy ingot obtained in step (1) is subjected to gradient homogenization heat treatment under argon protection, and then water quenched to room temperature to obtain a homogenized magnesium alloy ingot;

[0031] The gradient homogenization heat treatment is: holding at 290 DEG C for 2.5h, then holding at 345 DEG C for 6.1h, and then holding at 365 DEG C for 4.5h;

[0032] (3) annealing-rolling-annealing treatment is carried out on the homogenized magnesium alloy ingot obtained in step (2), and then air cooling to room temperature to obtain a low-cost high-strength fast-degradable Mg-1.5Zn-0.2Ca-1Ni magnesium alloy;

[0033] The annealing-rolling-annealing treatment is: annealing at 280 DEG C for 15 min, then rolling at 180 DEG C for 10 passes, holding at 280 DEG C for 15 min after each pass, rolling speed is 20r / min, total rolling reduction is 85%, and then annealing at 300 DEG C for 20 min.

[0034] Example 3

[0035] Taking Mg-1.5Zn-0.2Ca-3Ni alloy as an example (the component mass percentage is: Zn: 1.5%, Ca: 0.2%, Ni: 3%, unavoidable impurities total content ≤0.02%, and the balance is magnesium), the preparation method of the alloy is as follows:

[0036] (1) The required metal raw materials are weighed according to the mass percentage, and the surface oxidation products are removed for use. SF6 and CO2 are mixed according to a volume ratio of 0.7:99.3 to serve as a protective gas. Pure magnesium is added, and then the temperature is raised to 430 DEG C and held for 17 min, then raised to 530 DEG C and held for 1.2h, then raised to 680 DEG C and held for 1.5h. Then pure zinc, magnesium-calcium intermediate alloy, and magnesium-nickel intermediate alloy are added. After holding for 10 min, stirring is carried out at 685 DEG C under argon protection for 4 min, and then refining and slagging for 3 min. Then pouring is carried out to obtain a magnesium alloy ingot;

[0037] (2) The magnesium alloy ingot obtained in step (1) is subjected to gradient homogenization heat treatment under argon protection, and then water quenched to room temperature to obtain a homogenized magnesium alloy ingot;

[0038] The gradient homogenization heat treatment is: holding at 300 DEG C for 2h, then holding at 350 DEG C for 5.5h, and then holding at 400 DEG C for 4h;

[0039] (3) annealing-rolling-annealing treatment is carried out on the homogenized magnesium alloy ingot obtained in step (2), and then air cooling to room temperature to obtain a low-cost high-strength fast-degradable Mg-1.5Zn-0.2Ca-1Ni magnesium alloy;

[0040] The annealing-rolling-annealing treatment is: annealing at 250℃ for 30min, then 8 passes of rolling at 150℃, after each pass of rolling, heat preservation at 250℃ for 30min, rolling speed is 15r / min, total reduction is 80%, and annealing at 270℃ for 20min after rolling.

[0041] Example 4

[0042] Taking Mg-1.5Zn-0.2Ca-5Ni alloy as an example (the component mass percentage is: Zn: 1.5%, Ca: 0.2%, Ni: 5%, unavoidable impurities total content ≤0.02%, and the balance is magnesium), the preparation method of the alloy is as follows:

[0043] (1) The required metal raw materials are weighed according to the mass percentage, and the surface oxidation products are removed for use. SF6 and CO2 are mixed according to a volume ratio of 1:99 to serve as a protective gas. Pure magnesium is added, and then the temperature is raised to 410℃ for 20min, then to 510℃ for 1.5h, and then to 700℃ for 1h. Then, pure zinc, magnesium-calcium intermediate alloy, and magnesium-nickel intermediate alloy are added. After heat preservation for 6min, stirring is carried out at 695℃ under argon gas protection for 3min, and then refining and slagging for 2min. Then, pouring is carried out to obtain a magnesium alloy ingot;

[0044] (2) The magnesium alloy ingot obtained in step (1) is subjected to gradient homogenization heat treatment under argon gas protection, and then water quenched to room temperature to obtain a homogenized magnesium alloy ingot;

[0045] The gradient homogenization heat treatment is: heat preservation at 285℃ for 2.5h, then at 335℃ for 6.4h, and then at 355℃ for 4.8h;

[0046] (3) The homogenized magnesium alloy ingot obtained in step (2) is subjected to annealing-rolling-annealing treatment, and then air cooled to room temperature to obtain a low-cost high-strength rapid degradation Mg-1.5Zn-0.2Ca-5Ni magnesium alloy;

[0047] The annealing-rolling-annealing treatment is: annealing at 275℃ for 20min, then 6 passes of rolling at 125℃, after each pass of rolling, heat preservation at 275℃ for 20min, rolling speed is 18r / min, total reduction is 75%, and annealing at 295℃ for 40min after rolling.

[0048] Comparative Example 1

[0049] Patent CN 109161768 B discloses a copper-containing, high-strength, and rapidly degradable magnesium alloy, as well as its preparation method and use. Wang Jingfeng and his colleagues employed a resistance furnace or industrial frequency induction furnace under argon protection to melt the alloy. The alloy was heated to 750°C and held for 80 minutes, and then stirred using electromagnetic induction to homogenize the composition. After the raw materials were completely melted, the alloy was cooled to 650°C and held for 80 minutes. The alloy was then removed from the furnace and water-cooled in a salt bath to obtain a Mg-6.5Cu-2.5Y-0.8Zr alloy ingot (wt%). The ingot was then homogenized at 400°C for 20 hours, followed by extrusion deformation at 380°C and an extrusion ratio of 11. The ingot was then held at 200°C for 35 hours, and then air-cooled to room temperature.

[0050] Comparative Example 2

[0051] Patent CN 113025857 B discloses a soluble magnesium alloy material for an all-metal bridge plug and its preparation method. Li Hongxiang et al. obtained a Mg-9Li-0.8Al-0.1Zr-1.5Cu alloy (wt%) by smelting in a vacuum induction furnace under argon protection. The ingot was heat treated at 250°C for 10 hours and then extruded at 250°C with an extrusion ratio of 21.

[0052] Comparative Example 3

[0053] Metals, Mechanical and Corrosion Properties of Mg–Gd–Cu–Zr Alloy for Degradable Fracturing Ball Applications, Jiang et al. prepared a Mg-6.0Gd-1.2Cu-1.2Zr alloy (wt%) by gravity casting. The cast alloy was homogenized at 400°C for 24 hours and then hot-extruded at 400°C into 20 mm diameter rods with an extrusion ratio of 9:1.

[0054] Table 1 Alloy performance test results obtained in Examples and Comparative Examples

[0055]

[0056] The degradation rates of the alloys obtained in Examples 1-4 of the present invention at 90°C were 116 mg / cm 2 / h, 524mg / cm 2 / h, 834mg / cm 2 / h and 942mg / cm 2 / h, and the degradation rate of the alloy obtained by the present application is significantly increased with the increase of temperature. According to the data in Table 1, compared with the prior art, the alloy raw material cost and the total alloy addition amount of the prior art are higher than those of the alloy obtained by the present application, and the prior art and the present application adopt different preparation processes, and the result is that the mechanical properties of the alloy obtained by the present application are better than those of the alloy obtained by the prior art, and at the same time, the room temperature and high temperature degradation rates of the alloy obtained by the present application are significantly higher than those of the alloy obtained by the prior art, that is, the alloy obtained by the present application simultaneously realizes high mechanical properties, high room temperature and high temperature degradation rates. In addition, it can be seen from all the examples of the present application that: the raw materials, raw material ratio, process and process parameters used in each example are different, and the mechanical properties and degradation rates of the alloy finally obtained in each example are different, among which the component content of example 3 or 4 is not the highest in all examples, but higher mechanical properties and degradation rates are obtained. In summary: the optimal mechanical properties, high temperature resistance, high room temperature and high temperature degradation rates of the alloy obtained by the present application are realized by the synergistic regulation of the components, ratio, process and process parameters of the alloy, and only within the scope of protection of the present application, the mechanical properties, high temperature resistance, high room temperature and high temperature degradation rates of the alloy can be simultaneously improved.

Claims

1. A low-cost, high-strength, fast-degrading magnesium alloy, characterized by: The alloy is composed of the following components by mass percentage: 1-15% zinc, 0.1-1% calcium, additional elements, unavoidable impurities ≤ 0.02%, and the balance is magnesium. The additional element is nickel, and the nickel is 0.5-7%. The preparation method thereof comprises the following steps: (1) Weighing the required metal raw materials according to mass percentage, removing the surface oxidation products for later use, mixing SF6 and CO2 in a volume ratio of 0.2-1.5:98.5-99.8 as a protective gas, adding pure magnesium, then heating to 400-460 ° C and keeping warm for 10-30 minutes, then heating to 500-560 ° C and keeping warm for 0.5-2 hours, then heating to 650-710 ° C and keeping warm for 0.5-2 hours, adding pure zinc, magnesium-calcium master alloy, magnesium-nickel master alloy, keeping warm for 5-15 minutes, stirring for 1-5 minutes at 675-700 ° C under argon protection conditions, refining and slagging for 1-5 minutes, and then pouring to obtain a magnesium alloy ingot; (2) subjecting the magnesium alloy ingot obtained in step (1) to a gradient homogenization heat treatment under argon protection, and then quenching the ingot with water to room temperature to obtain a homogenized magnesium alloy ingot; The gradient homogenization heat treatment is as follows: keeping the temperature at 250-320°C for 1-4 hours, keeping the temperature at 310-360°C for 5-7 hours, and keeping the temperature at 330-410°C for 3-6 hours; (3) subjecting the homogenized magnesium alloy ingot obtained in step (2) to artificial aging or annealing-rolling-annealing treatment, and then air-cooling it to room temperature to obtain a low-cost, high-strength, fast-degrading magnesium alloy; The artificial aging is as follows: keeping the temperature at 140-210℃ for 3-7h; The annealing-rolling-annealing treatment comprises: annealing at 220-320°C for 10-40 minutes, then rolling at 100-200°C for 5-12 passes, keeping at 220-320°C for 10-40 minutes after each rolling pass, rolling at a speed of 10-25 r / min, a total rolling reduction of 70-90%, and annealing at 220-320°C for 20-60 minutes after rolling.

2. The low-cost, high-strength, fast-degrading magnesium alloy according to claim 1, characterized in that: The zinc content is 1.5-12%, and the calcium content is 0.2-0.5%.

3. The low-cost, high-strength, fast-degrading magnesium alloy according to claim 1, characterized in that: The nickel content is 1-5%.

4. A low-cost, high-strength, fast-degrading magnesium alloy according to any one of claims 1 to 3, characterized in that: The gradient homogenization heat treatment described in step (2) is: keeping warm at 280-300°C for 2-3 hours, then keeping warm at 325-350°C for 5.5-6.5 hours, and then keeping warm at 345-400°C for 4-5 hours.

5. The low-cost, high-strength, fast-degrading magnesium alloy according to claim 4, characterized in that: The artificial aging treatment in step (3) is: keeping the temperature at 150-200° C. for 5-6 hours.

6. The low-cost, high-strength, fast-degrading magnesium alloy according to claim 4, characterized in that: The annealing-rolling-annealing treatment described in step (3) is: annealing at 250-300°C for 15-30 minutes, then rolling at 120-180°C for 6-11 times, keeping at 250-300°C for 15-30 minutes after each rolling, rolling speed of 15-20 r / min, total rolling reduction of 75-85%, and annealing at 250-300°C for 30-50 minutes after rolling.

Images