Magnesium alloy plate and temperature-controlled hot rolling preparation method thereof

Abstract

A temperature-controlled hot rolling preparation method of a magnesium alloy plate is characterized in that temperature-controlled hot rolling is carried out between a homogenizing heat treatment step and a hot extrusion step, the temperature-controlled hot rolling preparation method is specifically divided into three stages, the rolling temperature in the first stage is 360-385 DEG C, the rolling deformation is 50-60%, the rolling temperature in the second stage is 340-360 DEG C, the rolling deformation is 30-40% of that after first deformation, the rolling temperature in the third stage is 320-350 DEG C, and the rolling deformation is 30-40% of that after first deformation. The rolling deformation amount is 20% of the rolling deformation amount after the secondary deformation. According to the method, the mechanical property and chemical stability of the alloy are effectively adjusted, the comprehensive mechanical property of the magnesium alloy plate is effectively adjusted by adding the hot rolling treatment step, the corrosion rate uniformity of the alloy in the high-temperature environment is further improved, and the corrosion stability and controllability of the alloy in different high-temperature environments are improved; the corrosion rate is regulated and controlled to be 30-40 mg.cm <-2 >. H <-1 >.

Description

Technical Field

[0001] The present invention relates to the technical field of preparing alloy sheets by controlled-temperature hot rolling, and particularly relates to a magnesium alloy sheet and a method for preparing the same by controlled-temperature hot rolling. Background Art

[0002] Fossil fuels such as petroleum, natural gas, and coal are the main sources of energy supply in the world today, and their extraction technologies are constantly advancing. When extracting low-permeability shale resources, traditional extraction methods have problems such as high operation risks, low efficiency, and high costs. Soluble magnesium alloys are widely used in the extraction of such resources due to their excellent corrosion rate and performance.

[0003] Volume fracturing technology is a new technology developed at home and abroad in recent years for the development of unconventional oil and gas reservoirs. This technology can shorten the seepage distance of fluids, improve the reverse flow capacity of reservoirs, and effectively achieve the stimulation and transformation of ultra-low permeability oil and gas reservoirs. Soluble magnesium alloys can be used to make fracturing balls. In the horizontal well staged fracturing technology, the fracturing balls made of soluble magnesium alloys are key components. During the fracturing operation, the fracturing balls are used to block specific channels to achieve staged fracturing. After the operation is completed, the soluble magnesium alloy fracturing balls can dissolve by themselves in the electrolyte liquid in the wellbore, avoiding the situation of being stuck in the channel like traditional fracturing balls, and eliminating the need for subsequent complex operations such as downhole milling, improving the operation efficiency and reducing the cost. Soluble magnesium alloys can also be used to manufacture bridge plugs, which are used to form effective blockages and separations in the wellbore to achieve the purpose of staged fracturing. After the fracturing task is completed, the bridge plugs dissolve and do not hinder subsequent operations. In addition, soluble magnesium alloys can also be used to manufacture other downhole fracturing tools such as soluble ball valves. Similarly, by utilizing their soluble characteristics, they can gradually dissolve in the downhole environment after the corresponding fracturing operations are completed, reducing the impact on the downhole environment and providing convenience for subsequent extraction operations.

[0004] Generally, in some conventional oil and gas well fracturing operations, the downhole temperature is generally in the range of several tens of degrees Celsius to about 100 °C. Soluble magnesium alloys can better adapt to such a temperature environment and play a role. However, with the development of deep oil and gas resources, the downhole temperature of some ultra-high temperature oil and gas wells may exceed 150 °C or even higher, which poses a challenge to the high-temperature resistance performance of soluble magnesium alloys. It is necessary to improve their stability at high temperatures by methods such as improving alloy composition and preparation processes. And soluble magnesium alloys need to have sufficient strength and toughness to ensure that they do not deform or rupture under high pressure, ensuring the smooth progress of the fracturing operation. And the specific dissolution rate at a certain temperature determines the time that the soluble material can withstand pressure, directly affecting the fracturing production time and the time for the pipeline to return to smoothness. Summary of the Invention

[0005] The object of the present invention is to provide a high-temperature resistant soluble magnesium alloy with adjustable and narrow corrosion rate at high temperatures.

[0006] Another object of the present invention is to provide a preparation method of the above-mentioned soluble magnesium alloy sheet.

[0007] The object of the present invention is achieved by the following technical solutions: A temperature-controlled hot rolling preparation method for a magnesium alloy sheet, which successively performs melting, casting, homogenization heat treatment, and hot extrusion steps. It is characterized in that: a hot rolling step is also carried out between the homogenization heat treatment step and the hot extrusion step, which is specifically divided into three stages. The temperature in the first stage is 360 - 385 °C, and the rolling deformation amount is 50 - 60%. The rolling temperature in the second stage is 340 - 360 °C, and the rolling deformation amount is 30 - 40% after the first deformation. In the third stage, the rolling temperature is 320 - 350 °C, and the rolling deformation amount is 20% after the second deformation.

[0008] In addition to alloy design, by adding Ca, Mn, and Si to the Mg-Zn-Ni alloy, and also performing hot rolling between the homogenization heat treatment step and the hot extrusion step, the comprehensive mechanical properties of the magnesium alloy are effectively adjusted, and at the same time, the plasticity of the material is improved. Secondly, the corrosion rate uniformity of the alloy in a high-temperature environment is effectively adjusted, and the corrosion stability and controllability of the alloy in different high-temperature environments are improved, thereby preparing a soluble magnesium alloy with a controllable narrow corrosion rate at high temperatures.

[0009] Furthermore, a post-treatment is carried out after the hot extrusion step. Specifically, the extruded magnesium alloy material is kept at 380 - 420 °C for 6 - 8 h, and then air-cooled to room temperature.

[0010] In the present invention, by performing post-treatment after hot extrusion, the corrosion rate of the magnesium alloy at high temperatures is effectively reduced and controlled within a stable target range.

[0011] Furthermore, in the magnesium alloy sheet, by mass percentage, Zn is 0.5 - 3.5%, Ni is 0.8 - 2%, Ca is 0.01 - 0.05%, Mn is 0.35 - 0.55%, Si is 0.1 - 0.3%, and the rest is Mg.

[0012] Further preferably, in the alloy, by mass percentage, Zn is 2.0%, Ni is 1.0%, Ca is 0.03%, Mn is 0.4%, Si is 0.2%, and the rest is Mg.

[0013] Further, for the smelting, in accordance with the component design, the raw materials of magnesium ingots, zinc ingots, magnesium-nickel master alloy, magnesium-calcium master alloy, anhydrous manganese chloride, and magnesium-silicon master alloy that have been weighed according to the composition design are preheated in a preheating furnace at 120 - 200°C. Then, first, the magnesium ingots are fed into the crucible of the magnesium alloy melting furnace and heated to melt. After all the magnesium liquid has melted and the temperature has risen to the range of 700 - 720°C, the zinc ingots, magnesium-nickel master alloy, magnesium-calcium master alloy, anhydrous manganese chloride, and magnesium-silicon master alloy are added in sequence, and kept warm for 30 - 50 min to melt them. The alloy melt composition is made uniform by stirring with argon gas blowing. After that, it is heated to 720 - 750°C, a refining agent is added, and argon gas is blown and stirred for 20 - 30 min. After the refining is completed, it is kept static and warm at 720 - 750°C for 20 - 40 min, and the slag and liquid are separated to obtain a pure magnesium alloy melt.

[0014] Further, for the casting, the alloy melt is cast into a copper mold, and blank preparation is carried out by a semi-continuous casting method. The casting blank speed is 300 mm / min, and the cooling water flow rate is 2 m 3 / h.

[0015] Further, for the homogenization heat treatment, the blank obtained by casting is covered with aluminum silicate heat preservation cotton and subjected to homogenization heat treatment at 390°C for 3 h, and then water quenched to obtain a billet in a soaking state.

[0016] Further, for the hot extrusion, the billet after hot rolling is cut and peeled, and then extruded at 310 - 340°C. The extrusion ratio is 22 - 28, and the extrusion speed is 12 - 16 mm / s.

[0017] Most specifically, a method for preparing a magnesium alloy sheet by temperature-controlled hot rolling is characterized by being prepared according to the following steps: (1) Smelting: The raw materials of magnesium ingots, zinc ingots, magnesium-nickel master alloy, magnesium-calcium master alloy, anhydrous manganese chloride, and magnesium-silicon master alloy that have been weighed according to the composition design are preheated in a preheating furnace at 120 - 200°C. Then, first, the magnesium ingots are fed into the crucible of the magnesium alloy melting furnace and heated to melt. After all the magnesium liquid has melted and the temperature has risen to the range of 700 - 720°C, the zinc ingots, magnesium-nickel master alloy, magnesium-calcium master alloy, anhydrous manganese chloride, and magnesium-silicon master alloy are added in sequence, and kept warm for 30 - 50 min to melt them. The alloy melt composition is made uniform by stirring with argon gas blowing. After that, it is heated to 720 - 750°C, a refining agent is added, and argon gas is blown and stirred for 20 - 30 min. After the refining is completed, it is kept static and warm at 720 - 750°C for 20 - 40 min, and the slag and liquid are separated to obtain a pure magnesium alloy melt.

[0018] (2) Casting: The alloy melt is cast into a copper mold, and blank preparation is carried out by a semi-continuous casting method. The casting blank speed is 300 mm / min, and the cooling water flow rate is 2 m3 / h; (3)Homogenization heat treatment: Cover the blank obtained by casting with aluminosilicate insulation wool, conduct homogenization heat treatment at 390 °C for 3 h, and then perform water quenching to obtain a billet in a soaking state; (4)Hot rolling: The billet in the soaking state is hot-rolled in three stages. The temperature in the first stage is 360 - 385 °C, and the rolling deformation is 50 - 60%. The rolling temperature in the second stage is 340 - 360 °C, and the rolling deformation is 30 - 40% after the first deformation. In the third stage, the rolling temperature is 320 - 350 °C, and the rolling deformation is 20% after the second deformation; (5)Hot extrusion: Cut and peel the hot-rolled billet, and then perform extrusion at 280 - 310 °C. The extrusion ratio is 22 - 28, and the extrusion speed is 12 - 16 mm / s; (6)Post-extrusion treatment: Keep the hot-extruded magnesium alloy at 380 - 420 °C for 6 - 8 h, and then air-cool it to room temperature.

[0019] A soluble magnesium alloy with a high-temperature controllable narrow corrosion rate, characterized in that: the magnesium alloy is mainly composed of Mg, Zn, and Ni, and is composed of Ca, Mn, and Si as trace elements.

[0020] Further, in the alloy, each component is calculated by mass percentage as Zn is 0.5 - 3.5%, Ni is 0.8 - 2%, Ca is 0.01 - 0.05%, Mn is 0.35 - 0.55%, Si is 0.1 - 0.3%, and the rest is Mg.

[0021] Further preferably, in the alloy, each component is calculated by mass percentage as Zn is 2.0%, Ni is 1.0%, Ca is 0.03%, Mn is 0.4%, Si is 0.2%, and the rest is Mg.

[0022] The main use of the soluble magnesium alloy of the present invention is a soluble bridge plug for volume fracturing in oil exploitation. During use, the solubility requirement for the soluble bridge plug is relatively strict. It is required to maintain a certain strength at a deeper formation and a higher temperature above 80 °C or even 200 °C, and fracture the formation by holding pressure to improve the exploitation efficiency. In such a complex working condition environment with high temperature, high pressure, and chemical conditions, the soluble magnesium alloy, on the one hand, needs to maintain a certain stability during the fracturing operation to maintain the performance of the tool; on the other hand, after the operation is completed, it should be able to dissolve in this electrolyte solution at a designed speed. If the corrosion rate is too fast during this process, the pressure holding time will not be sufficient and fracturing exploitation cannot be achieved. If the corrosion rate is too slow, it will affect the production efficiency.

[0023] In the present invention, Zn and Ni are alloyed with Mg, and then trace amounts of Ca, Mn, and Si are added. The addition of Ca alone is to prevent the oxidation of the alloy during melting, and it has little effect on the mechanical properties and corrosion rate of the alloy. The introduction of Si and Mn can both adjust the mechanical properties of the alloy, and Mn can also reduce the corrosion rate of the alloy at high temperatures. During the composite addition process, the grain refinement effect of Ca provides more nucleation sites for the strengthening phases of Mn and Si, making the distribution of the strengthening phases more uniform. The three cooperate with each other to improve the high-temperature strength of the alloy from multiple aspects. And Mn promotes the enrichment of Si and Ca on the surface, enhancing the content and stability of SiO 2 and calcium-containing compounds in the surface film, and improving the compactness, integrity, and chemical stability of the surface film. The combined action of the three optimizes the microstructure of the alloy, reduces impurities and defects, and reduces the possibility of forming corrosion micro-cells, thereby effectively controlling the corrosion rate of the magnesium alloy at high temperatures.

[0024] The above-mentioned high-temperature resistant soluble magnesium alloy with a controllable narrow corrosion rate is prepared by the steps of melting, casting, homogenization heat treatment, hot rolling, hot extrusion, and post-treatment after hot extrusion. After the hot extrusion step, post-treatment is also carried out. Specifically, the extruded magnesium alloy material is kept at 380 - 420 °C for 6 - 8 h, and then air-cooled to room temperature.

[0025] Furthermore, the hot rolling is specifically divided into three stages. The temperature of the first stage is 360 - 385 °C, and the rolling deformation is 50 - 60%. The rolling temperature of the second stage is 340 - 360 °C, and the rolling deformation is 30 - 40% of that after the first deformation. In the third stage, the rolling temperature is 320 - 350 °C, and the rolling deformation is 20% of that after the second deformation.

[0026] The present invention has the following technical effects: In the present invention, Ca, Mn, and Si are added to the Mg-Zn-Ni alloy, effectively adjusting the mechanical properties and chemical stability of the alloy. Combining with the post-treatment step after extrusion, it has ideal tensile strength and elongation in a high-temperature environment, and at the same time, the corrosion rate is controlled at 30 - 40 mg·cm -2 ·h -1 . Secondly, by adding the hot rolling step, the comprehensive mechanical properties of the magnesium alloy sheet are effectively adjusted, the corrosion rate uniformity of the alloy in a high-temperature environment is improved, and the corrosion stability and controllability of the alloy in different high-temperature environments are improved. Description of the Drawings

[0027] Figure 1 : SEM image of Mg-2Zn-Ni-0.03Ca-0.4Mn-0.2Si prepared by the present invention.

[0028] Figure 2: Energy spectrum diagram of Mg-2Zn-Ni-0.03Ca-0.4Mn-0.2Si prepared by the present invention.

[0029] Figure 3 : Stress-strain curve of Mg-2Zn-Ni-0.03Ca-0.4Mn-0.2Si prepared by the present invention.

[0030] Figure 4 : Stress-strain curve of Mg-3.5Zn-0.8Ni-0.01Ca-0.35Mn-0.3Si prepared by the present invention. Detailed implementation manners

[0031] The present invention will be specifically described below through embodiments. It is necessary to point out here that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the protection scope of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention according to the above content of the present invention.

[0032] Under high temperature, high pressure, and in the presence of electrolytes (such as sodium chloride, calcium chloride, etc., and may also contain some acidic or alkaline substances), it is required that the soluble bridge plug maintains a relatively high strength within a certain time (the first 3 days) to facilitate fracturing, and then completely dissolves within a certain time (on the 4th - 5th day). To achieve the above effects, the soluble magnesium alloy needs to have an appropriate corrosion rate. After continuous testing, the corrosion rate of the soluble magnesium alloy at high temperature needs to be controlled within 30 - 40 mg·cm -2 ·h -1 , which not only ensures sufficient pressure holding time to achieve fracturing production but also does not affect production efficiency due to a slow corrosion rate. On the premise of ensuring the stability of the corrosion rate of the magnesium alloy at high temperature, the magnesium alloy also needs to have excellent mechanical properties at high temperature and be able to resist the plastic stability performance under high temperature and high pressure during fracturing.

[0033] Example 1 A soluble magnesium alloy with a controllable narrow corrosion rate at high temperature. In the alloy, the components are in mass percentages as follows: Zn is 2.0%, Ni is 1.0%, Ca is 0.03%, Mn is 0.4%, Si is 0.2%, and the rest is Mg.

[0034] According to the above alloy design, soluble magnesium alloy sheets are prepared based on controlled-temperature hot rolling. The specific steps are as follows: (1)Melting: The magnesium ingots, zinc ingots, Mg-Ni master alloy, Mg-Ca master alloy, anhydrous manganese chloride, and Mg-Si master alloy raw materials weighed according to the composition design are preheated in a preheating furnace at 150 °C. Then, the magnesium ingots are first charged into the crucible of the magnesium alloy melting furnace and heated to melt. When all the magnesium liquid is melted and heated to the range of 710 °C, the zinc ingots, Mg-Ni master alloy, Mg-Ca master alloy, anhydrous manganese chloride, and Mg-Si master alloy are added in sequence, and kept warm for 40 min to melt them. The alloy melt is stirred by blowing argon gas to make the composition of the alloy melt uniform. Then, it is heated to 720 - 750 °C, a refining agent is added, and it is stirred by blowing argon gas for 25 min. After refining, it is kept static and warm at 740 °C for 30 min, and the slag and liquid are separated to obtain a pure magnesium alloy melt; (2)Casting: The alloy melt is cast into a copper mold, and blank preparation is carried out by semi-continuous casting. The casting speed of the blank is 300 mm / min, and the cooling water flow rate is 2 m 3 / h; (3)Homogenization heat treatment: The blank obtained by casting is covered with aluminosilicate insulation wool and subjected to homogenization heat treatment at 390 °C for 3 h, and then water quenched to obtain a billet in the soaked state; (4)Hot rolling: The billet in the soaked state is hot rolled in three stages. The rolling temperature in the first stage is 370 °C, and the rolling reduction is 55%. The rolling temperature in the second stage is 350 °C, and the rolling reduction is 35% after the first deformation. In the third stage, the rolling temperature is 340 °C, and the rolling reduction is 20% after the second deformation; (5)Hot extrusion: The hot-rolled billet is cut and peeled, and then extruded at 300 °C. The extrusion ratio is 25, and the extrusion speed is 15 mm / s to obtain a hot-extruded magnesium alloy; The hot-extruded magnesium alloy is subjected to a tensile test. At room temperature, the tensile strength of the alloy is 294 Mpa, and the elongation is 11.2%. The specimen is placed in a solution of 3 wt.% KCl, and the corrosion rate of the alloy at room temperature is measured to be 9.5 mg·cm -2 ·h -1 −1, and the corrosion rate at 93 °C is 90.7 mg·cm -2 ·h -1 −1; (6)Post-extrusion treatment: The hot-extruded magnesium alloy is kept warm at 400 °C for 8 h, and then air-cooled to room temperature. The obtained magnesium alloy sheet is denoted as Mg-2Zn-Ni-0.03Ca-0.4Mn-0.2Si.

[0035] The tensile strength of the magnesium alloy sheet Mg-2Zn-Ni-0.03Ca-0.4Mn-0.2Si obtained by post-extrusion treatment at room temperature is 292 Mpa, and the elongation is 11.8%. The specimen is placed in a solution of 3 wt.% KCl, and the corrosion rate of the alloy at room temperature is measured to be 3.5 mg·cm-2 ·h -1 and the corrosion rate at 93 °C is 36.4 mg·cm -2 ·h -1 . That is, the extrusion post-treatment step effectively reduces the corrosion rate of the alloy at high temperature on the premise of ensuring its excellent mechanical properties, enabling it to be completely dissolved within the target time.

[0036] According to the preparation process of Example 1, the composition of each component in the magnesium alloy was adjusted, specifically as follows in each comparative example: Comparative Example 1 According to the preparation process of Example 1, the composition of the alloy was adjusted to Zn 2.0%, Ni 1.0%, and the rest was Mg. The prepared alloy material was denoted as Mg-2Zn-Ni.

[0037] The Mg-2Zn-Ni magnesium alloy sheet without post-treatment after hot extrusion was subjected to a tensile test. At room temperature, the tensile strength of the alloy was 247 Mpa and the elongation was 10.8%. The specimen was placed in a 3 wt.% KCl solution, and the measured corrosion rate of the alloy at room temperature was 26.5 mg·cm -2 ·h -1 and the corrosion rate at 93 °C was 107.7 mg·cm -2 ·h -1 ; for the Mg-2Zn-Ni magnesium alloy sheet with extrusion post-treatment, the tensile strength at room temperature was 241 Mpa, the elongation was 10.1%, and the corrosion rate was 18.6 mg·cm -2 ·h -1 and the corrosion rate at 93 °C was 84.8 mg·cm -2 ·h -1 .

[0038] Without the addition of trace amounts of Ca, Mn, and Si, the mechanical properties of the magnesium alloy without post-treatment after extrusion were relatively low at room temperature. For the magnesium alloy Mg-2Zn-Ni with extrusion post-treatment, the corrosion rates at room temperature and high temperature decreased significantly, and the mechanical properties also decreased to a certain extent.

[0039] Comparative Example 2 According to the preparation process of Example 1, the composition of the alloy was adjusted to Zn 2.0%, Ni 1.0%, Ca 0.03%, and the rest was Mg. The prepared alloy sheet was denoted as Mg-2Zn-Ni-0.03Ca.

[0040] In the Mg-2Zn-Ni-0.03Ca alloy sheet, adding a trace amount of Ca is to prevent the oxidation of Mg and other alloy elements during melting. After tensile testing of the as-extruded Mg-2Zn-Ni-0.03Ca magnesium alloy without post-treatment, the tensile strength of the alloy at room temperature is 246 Mpa, and the elongation is 10.5%. When the specimen is placed in a 3 wt.% KCl solution, the corrosion rate of the alloy at room temperature is measured to be 26.6 mg·cm -2 ·h -1 , and the corrosion rate at 93 °C is 106.2 mg·cm -2 ·h -1 ; The tensile strength of the extruded and post-treated Mg-2Zn-Ni-0.03Ca magnesium alloy sheet at room temperature is 243 Mpa, the elongation is 10.2%, and the corrosion rate is 18.3 mg·cm -2 ·h -1 , and the corrosion rate at 93 °C is 83.5 mg·cm -2 ·h -1 . That is, the influence of this addition amount of Ca on the mechanical properties and corrosion properties of the alloy is almost negligible.

[0041] At the same time, we prepared Mg-2Zn-Ni-0.4Mn and Mg-2Zn-Ni-0.2Si by separately adding 0.4% Mn and 0.2% Si on the basis of Mg-2Zn-Ni. Among them, the tensile strength of the as-extruded Mg-2Zn-Ni-0.4Mn without post-treatment is 265 Mpa, and the elongation is 11.1%. When the specimen is placed in a 3 wt.% KCl solution, the corrosion rate of the alloy at room temperature is measured to be 23.2 mg·cm -2 ·h -1 , and the corrosion rate at 93 °C is 99.4 mg·cm -2 ·h -1 ; The tensile strength of the extruded and post-treated magnesium alloy sheet Mg-2Zn-Ni-0.4Mn at room temperature is 264 Mpa, the elongation is 11.2%, and the corrosion rate is 4.7 mg·cm -2 ·h -1 , and the corrosion rate at 93 °C is 14.1 mg·cm -2 ·h -1 .

[0042] The tensile strength of the as-extruded Mg-2Zn-Ni-0.2Si without post-treatment is 269 Mpa, and the elongation is 11.7%. When the specimen is placed in a 3 wt.% KCl solution, the corrosion rate of the alloy at room temperature is measured to be 17.2 mg·cm -2 ·h -1 , and the corrosion rate at 93 °C is 109.1 mg·cm-2 ·h -1 ; The tensile strength of the extruded and post-treated magnesium alloy sheet Mg-2Zn-Ni-0.2Si at room temperature is 266 Mpa, the elongation is 11.5%, and the corrosion rate is 14.3 mg·cm -2 ·h -1 , and the corrosion rate at 93 °C is 88.6 mg·cm -2 ·h -1 .

[0043] Comparative Example 3 According to the preparation process of Example 1, the composition of the alloy was adjusted to Zn 2.0%, Ni 1.0%, Ca 0.03%, Mn 0.4%, and the rest was Mg. The prepared alloy sheet was denoted as Mg-2Zn-Ni-0.03Ca-0.4Mn.

[0044] The tensile strength of the extruded but not post-treated Mg-2Zn-Ni-0.03Ca-0.4Mn was 281 Mpa, the elongation was 11.9%. The sample was placed in a 3 wt.% KCl solution, and the measured corrosion rate of the alloy at room temperature was 17.2 mg·cm -2 ·h -1 , and the corrosion rate at 93 °C was 79.1 mg·cm -2 ·h -1 ; The tensile strength of the extruded and post-treated magnesium alloy sheet Mg-2Zn-Ni-0.03Ca-0.4Mn at room temperature was 275 Mpa, the elongation was 11.5%, and the corrosion rate was 10.3 mg·cm -2 ·h -1 , and the corrosion rate at 93 °C was 21.8 mg·cm -2 ·h -1 . Compared with Mg-2Zn-Ni-0.4Mn, the addition of Ca increased the corrosion rate of the extruded and post-treated alloy at high temperature.

[0045] Comparative Example 4 According to the preparation process of Example 1, the composition of the alloy was adjusted to Zn 2.0%, Ni 1.0%, Ca 0.03%, Si 0.2%, and the rest was Mg. The prepared alloy sheet was denoted as Mg-2Zn-Ni-0.03Ca-0.2Si.

[0046] The tensile strength of the hot-extruded but not post-treated Mg-2Zn-Ni-0.03Ca-0.2Si was 288 Mpa, the elongation was 11.1%. The sample was placed in a 3 wt.% KCl solution, and the measured corrosion rate of the alloy at room temperature was 25.2 mg·cm -2 ·h -1, the corrosion rate at 93 °C is 102.3 mg·cm -2 ·h -1 ; The tensile strength of the extruded and post-treated magnesium alloy sheet Mg-2Zn-Ni-0.03Ca-0.2Si at room temperature is 286 Mpa, the elongation is 11.5%, and the corrosion rate is 17.9 mg·cm -2 ·h -1 , and the corrosion rate at 93 °C is 81.6 mg·cm -2 ·h -1 . Although the mechanical properties of the final alloy are excellent and the corrosion rate at room temperature is also similar to that of Example 1, the corrosion rate of the magnesium alloy at high temperature is rapid, significantly higher than the expected 30 - 40 mg·cm -2 ·h -1 , which will cause problems such as too fast dissolution, reduced output, and increased mining costs.

[0047] Comparative Example 5 According to the preparation process of Example 1, the alloy composition was adjusted to 2.0% Zn, 1.0% Ni, 0.2% Si, 0.4% Mn, and the rest was Mg. The prepared alloy sheet was denoted as Mg-2Zn-Ni-0.2Si-0.4Mn.

[0048] The tensile strength of the extruded Mg-2Zn-Ni-0.2Si-0.4Mn without post-treatment is 308 Mpa, the elongation is 12.4%, and the specimen was placed in a 3 wt.% KCl solution, and the measured corrosion rate of the alloy at room temperature is 11.2 mg·cm -2 ·h -1 , and the corrosion rate at 93 °C is 90.8 mg·cm -2 ·h -1 ; The tensile strength of the extruded and post-treated magnesium alloy sheet Mg-2Zn-Ni-0.2Si-0.4Mn at room temperature is 304 Mpa, the elongation is 11.5%, and the corrosion rate is 7.9 mg·cm -2 ·h -1 , and the corrosion rate at 93 °C is 61.6 mg·cm -2 ·h -1 .

[0049] Comparative Example 6 Compared with Example 1, hot rolling was not carried out between homogenization heat treatment and hot extrusion, and the overall process flow was melting - casting - homogenization heat treatment - hot extrusion - extrusion post-treatment. The specific processes of each step were the same as those of Example 1. After hot extrusion, the magnesium alloy was subjected to a tensile test. The tensile strength of the alloy at room temperature was 285 Mpa, the elongation was 10.4%, and the specimen was placed in a 3 wt.% KCl solution, and the measured corrosion rate of the alloy at room temperature was 11.6 mg·cm-2 ·h -1 and the corrosion rate at 93 °C is 104.8 mg·cm -2 ·h -1 ; The tensile strength of the alloy sheet Mg-2Zn-Ni-0.03Ca-0.4Mn-0.2Si obtained by extrusion post-treatment at room temperature is 280 Mpa, and the elongation is 10.8%. When the specimen is placed in a solution of 3 wt.% KCl, the measured corrosion rate of the alloy at room temperature is 3.5 mg·cm -2 ·h -1 and the corrosion rate at 93 °C is 47.2 mg·cm -2 ·h -1 .

[0050] Taking the alloy Mg-2Zn-Ni without the addition of Ca, Mn and Si, and prepared without hot rolling between homogenization heat treatment and hot extrusion as the blank group for comparison, the changes in the corrosion rate of the finally prepared Mg-2Zn-Ni-0.03Ca-0.4Mn-0.2Si in the blank group, Example 1 and Comparative Example 6 with temperature changes are shown in Table 1.

[0051] Table 1:

[0052] It can be seen that for the alloy Mg-2Zn-Ni-0.03Ca-0.4Mn-0.2Si prepared in Example 1 at high temperature, as the temperature increases, the corrosion rate of the alloy increases, but the range of the increase rate is relatively narrow, and the corrosion rate of the alloy does not change significantly in different temperature environments, with excellent corrosion stability, making the alloy suitable for applications in different temperature environments. For the alloy sheet Mg-2Zn-Ni-0.03Ca-0.4Mn-0.2Si prepared in Comparative Example 6 at high temperature, as the temperature increases, the corrosion rate of the alloy shows an obvious change, the rate change range is large, and the controllability decreases.

[0053] Example 2 A soluble magnesium alloy with a controllable narrow corrosion rate at high temperature. In the alloy, the components are in mass percentages: Zn is 2.0%, Ni is 1.0%, Ca is 0.03%, Mn is 0.4%, Si is 0.2%, and the rest is Mg.

[0054] According to the above alloy design, a soluble magnesium alloy sheet is prepared based on controlled-temperature hot rolling. The specific steps are as follows: (1)Melting: The raw materials of magnesium ingots, zinc ingots, Mg-Ni master alloy, Mg-Ca master alloy, anhydrous manganese chloride, and Mg-Si master alloy weighed according to the composition design are preheated in a preheating furnace at 120 °C. Then, the magnesium ingots are first charged into the crucible of the magnesium alloy melting furnace and heated to melt. When the magnesium liquid is completely melted and heated to the range of 700 °C, zinc ingots, Mg-Ni master alloy, Mg-Ca master alloy, anhydrous manganese chloride, and Mg-Si master alloy are added in sequence, and kept warm for 30 min to melt them. The alloy melt is stirred by blowing argon gas to make the composition uniform. Then, it is heated to 750 °C, a refining agent is added, and argon gas is blown and stirred for 20 min. After refining, it is kept warm and static at 750 °C for 20 min, and the slag and liquid are separated to obtain a pure magnesium alloy melt; (2)Casting: The alloy melt is cast into a copper mold, and blank preparation is carried out by semi-continuous casting. The casting blank speed is 300 mm / min, and the cooling water flow rate is 2 m 3 / h; (3)Homogenization heat treatment: The blank obtained by casting is covered with aluminum silicate insulation wool and subjected to homogenization heat treatment at 390 °C for 3 h, and then water quenched to obtain a billet in the soaking state; (4)Hot rolling: The cast billet is hot rolled in three stages. The rolling temperature in the first stage is 385 °C, and the rolling deformation is 50%. The rolling temperature in the second stage is 360 °C, and the rolling deformation is 40% of that after the first deformation. In the third stage, the rolling temperature is 350 °C, and the rolling deformation is 20% of that after the second deformation; (5)Hot extrusion: The hot-rolled billet is cut and peeled, and then extruded at 310 °C. The extrusion ratio is 28, and the extrusion speed is 12 mm / s to obtain a hot-extruded magnesium alloy; (6)Post-extrusion treatment: The hot-extruded magnesium alloy is kept warm at 380 °C for 7 h, and then air-cooled to room temperature.

[0055] The tensile strength of the magnesium alloy Mg-2Zn-Ni-0.03Ca-0.4Mn-0.2Si obtained by post-extrusion treatment at room temperature is 290 Mpa, and the elongation is 11.6%. The specimen is placed in a solution of 3 wt.% KCl, and the corrosion rate of the alloy at room temperature is measured to be 3.8 mg·cm -2 ·h -1 , and the corrosion rate at 93 °C is 36.1 mg·cm -2 ·h -1 .

[0056] Example 3 A soluble magnesium alloy with high-temperature controllable narrow corrosion rate. In the alloy, the components are 2.0% Zn, 1.0% Ni, 0.03% Ca, 0.4% Mn, 0.2% Si by mass percentage, and the rest is Mg.

[0057] Based on the above alloy design, soluble magnesium alloy sheets are prepared by controlled-temperature hot rolling, and the specific steps are as follows: (1) Melting: The raw materials of magnesium ingots, zinc ingots, Mg-Ni master alloy, Mg-Ca master alloy, anhydrous manganese chloride, and Mg-Si master alloy weighed according to the composition design are preheated in a preheating furnace at 200 °C. Then, the magnesium ingots are first fed into the crucible of the magnesium alloy melting furnace and heated to melt. When all the magnesium liquid is melted and the temperature is raised to the range of 720 °C, zinc ingots, Mg-Ni master alloy, Mg-Ca master alloy, anhydrous manganese chloride, and Mg-Si master alloy are added in sequence, and they are kept warm for 50 min to melt. The alloy melt composition is made uniform by stirring with argon gas. After that, it is heated to 720 °C again, a refining agent is added, and it is stirred with argon gas for 30 min. After refining, it is kept still and warm at 720 °C for 40 min, and the slag and liquid are separated to obtain a pure magnesium alloy melt; (2) Casting: The alloy melt is cast into a copper mold, and blank preparation is carried out by semi-continuous casting. The casting blank speed is 300 mm / min, and the cooling water flow rate is 2 m 3 / h; (3) Homogenization heat treatment: The blank obtained by casting is covered with aluminosilicate insulating wool and subjected to homogenization heat treatment at 390 °C for 3 h, and then water quenched to obtain a homogenized blank; (4) Hot rolling: The cast blank is hot rolled in three stages. The rolling temperature in the first stage is 385 °C, and the rolling deformation is 60%. The rolling temperature in the second stage is 340 °C, and the rolling deformation is 30% of that after the first deformation. In the third stage, the rolling temperature is 320 °C, and the rolling deformation is 20% of that after the second deformation; (5) Hot extrusion: The hot-rolled blank is cut and peeled, and then extruded at 280 °C. The extrusion ratio is 22, and the extrusion speed is 16 mm / s to obtain a hot-extruded magnesium alloy; (6) Post-extrusion treatment: The hot-extruded magnesium alloy is kept warm at 420 °C for 6 h, and then air-cooled to room temperature.

[0058] The tensile strength of the alloy Mg-2Zn-Ni-0.03Ca-0.4Mn-0.2Si obtained by post-extrusion treatment at room temperature is 289 Mpa, and the elongation is 11.7%. When the specimen is placed in a solution of 3 wt.% KCl, the corrosion rate of the alloy at room temperature is measured to be 4.7 mg·cm -2 ·h -1 , and the corrosion rate at 93 °C is 38.6 mg·cm -2 ·h -1 .

[0059] Example 4 A soluble magnesium alloy with a controllable narrow corrosion rate at high temperature. In the alloy, the components are, by mass percentage, 3.5% Zn, 0.8% Ni, 0.01% Ca, 0.35% Mn, 0.3% Si, and the balance is Mg. The preparation process is the same as that of Example 3, and the prepared alloy is denoted as Mg-3.5Zn-0.8Ni-0.01Ca-0.35Mn-0.3Si.

[0060] After the tensile test of the magnesium alloy without post-treatment after hot extrusion, the tensile strength of the alloy at room temperature is 315 Mpa, and the elongation is 12.0%. The specimen is placed in a solution of 3 wt.% KCl, and the corrosion rate of the alloy at room temperature is measured to be 7.5 mg·cm -2 ·h -1 , and the corrosion rate at 93 °C is 83.5 mg·cm -2 ·h -1 ; For the alloy Mg-3.5Zn-0.8Ni-0.01Ca-0.35Mn-0.3Si after extrusion post-treatment, the tensile strength at room temperature is 310 Mpa, and the elongation is 11.8%. The specimen is placed in a solution of 3 wt.% KCl, and the corrosion rate of the alloy at room temperature is measured to be 3.9 mg·cm -2 ·h -1 , and the corrosion rate at 93 °C is 32.7 mg·cm -2 ·h -1 .

[0061] Example 5 A soluble magnesium alloy with a controllable narrow corrosion rate at high temperature. In the alloy, the components are, by mass percentage, 0.5% Zn, 2.0% Ni, 0.05% Ca, 0.55% Mn, 0.1% Si, and the balance is Mg. The preparation process is the same as that of Example 3, and the prepared alloy is denoted as Mg-0.5Zn-2Ni-0.05Ca-0.55Mn-0.1Si.

[0062] After the tensile test of Mg-0.5Zn-2Ni-0.05Ca-0.55Mn-0.1Si without post-treatment after hot extrusion, the tensile strength of the alloy at room temperature is 278 Mpa, and the elongation is 12.3%. The specimen is placed in a solution of 3 wt.% KCl, and the corrosion rate of the alloy at room temperature is measured to be 9.1 mg·cm -2 ·h -1 , and the corrosion rate at 93 °C is 104.2 mg·cm -2 ·h -1; The tensile strength of the extruded and post-treated alloy Mg-0.5Zn-2Ni-0.05Ca-0.55Mn-0.1Si at room temperature is 274 Mpa, and the elongation is 11.9%. When the specimen is placed in a solution of 3 wt.% KCl, the corrosion rate of the alloy at room temperature is measured to be 5.1 mg·cm -2 ·h -1 , and the corrosion rate at 93 °C is 38.2 mg·cm -2 ·h -1 .

Claims

1. A method for preparing a magnesium alloy sheet by temperature-controlled hot rolling, which sequentially carries out alloy melting, casting, homogenization heat treatment, and hot extrusion steps, characterized in that: Hot rolling is also carried out between the homogenization heat treatment step and the hot extrusion step, which is specifically divided into three stages. The rolling temperature in the first stage is 360~385℃, and the rolling deformation is 50~60%. The rolling temperature in the second stage is 340~360℃, and the rolling deformation is 30~40% of that after the first deformation. In the third stage, the rolling temperature is 320~350℃, and the rolling deformation is 20% of that after the second deformation.

2. The method for preparing a magnesium alloy sheet by temperature-controlled hot rolling according to claim 1, characterized in that: The hot extrusion step is followed by post-treatment, specifically, the extruded magnesium alloy material is kept at 380-420° C. for 6-8 hours, and then air-cooled to room temperature.

3. The method for preparing a magnesium alloy sheet by temperature-controlled hot rolling according to claim 1 or 2, characterized in that: In the alloy, the components by mass percentage are: Zn is 0.5-3.5%, Ni is 0.8-2%, Ca is 0.01-0.05%, Mn is 0.35-0.55%, Si is 0.1-0.3%, and the rest is Mg.

4. The method for preparing a magnesium alloy sheet by temperature-controlled hot rolling according to any one of claims 1 to 3, characterized in that: The smelting is designed according to the components, and the raw materials of magnesium ingot, zinc ingot, magnesium-nickel master alloy, magnesium-calcium master alloy, anhydrous manganese chloride and magnesium-silicon master alloy are weighed and dried and preheated in a preheating furnace at 120-200° C. Then, the magnesium ingot is first fed into the crucible of the magnesium alloy smelting furnace, and the temperature is increased to melt. After the magnesium liquid is completely melted and the temperature is increased to 700-720° C., the zinc ingot, magnesium-nickel master alloy, magnesium-calcium master alloy, anhydrous manganese chloride and magnesium-silicon master alloy are added in sequence, and the temperature is kept for 30-50 minutes to melt them, and the alloy melt is stirred by blowing argon to make the composition uniform, and then heated to 720-750° C., a refining agent is added, and argon is blown and stirred for 20-30 min. After the refining is completed, it is kept at 720-750° C. for 20-40 min, and the slag and liquid are separated to obtain a pure magnesium alloy melt.

5. The method for preparing a magnesium alloy sheet by temperature-controlled hot rolling according to claim 4, characterized in that: The casting is to cast the alloy melt into a copper mold, and the billet is prepared by semi-continuous casting. The billet casting speed is 300mm / min, and the cooling water flow speed is 2m 3 / h.

6. The method for preparing a magnesium alloy sheet by temperature-controlled hot rolling according to claim 5, characterized in that: The homogenization heat treatment is to cover the blank obtained by casting with aluminum silicate insulation cotton, perform homogenization heat treatment at 390° C. for 3 h, and then water quench to obtain a uniformly heated blank.

7. The method for preparing a magnesium alloy sheet by temperature-controlled hot rolling according to claim 6, characterized in that: The hot extrusion is to cut and peel the hot billet, and then extrude it at 310-340° C., with an extrusion ratio of 22-28 and an extrusion speed of 12-16 mm / s.

8. A method for preparing a magnesium alloy sheet by temperature-controlled hot rolling, characterized in that: Prepared according to the following steps: (1) Melting: According to the composition design, weigh the raw materials of magnesium ingot, zinc ingot, magnesium-nickel master alloy, magnesium-calcium master alloy, anhydrous manganese chloride, and magnesium-silicon master alloy and dry and preheat them in a preheating furnace at 120~200℃. Then, first put the magnesium ingot into the crucible of the magnesium alloy melting furnace and heat it to melt. After the magnesium liquid is completely melted and the temperature is raised to 700~720℃, add the zinc ingot, magnesium-nickel master alloy, magnesium-calcium master alloy, anhydrous manganese chloride, and magnesium-silicon master alloy in turn, keep it warm for 30~50 minutes to melt it, and stir it by blowing argon to make the alloy melt uniform. Then heat it to 720~750℃, add the refining agent, blow argon and stir for 20~30 minutes. After the refining is completed, keep it warm at 720~750℃ for 20~40 minutes. min, slag-liquid separation to obtain a pure magnesium alloy melt, wherein the alloy design comprises the following components by mass percentage: Zn is 0.5-3.5%, Ni is 0.8-2%, Ca is 0.01-0.05%, Mn is 0.35-0.55%, Si is 0.1-0.3%, and the rest is Mg; (2) Casting: The alloy melt is cast into a copper mold and the billet is prepared by semi-continuous casting. The billet casting speed is 300 mm / min and the cooling water flow speed is 2 m / min. 3 / h; (3) Homogenization heat treatment: The billet obtained by casting is covered with aluminum silicate insulation cotton, subjected to homogenization heat treatment at 390 °C for 3 h, and then water quenched to obtain a uniformly heated billet; (4) Hot rolling: The uniformly heated billet is hot rolled in three stages. The rolling temperature in the first stage is 360-385°C, the rolling deformation is 50-60%, the rolling temperature in the second stage is 340-360°C, the rolling deformation is 30-40% of the first deformation, and the third stage is 320-350°C, the rolling deformation is 20% of the second deformation. (5) Hot extrusion: the hot-rolled billet is cut and peeled, and then extruded at 310-340 °C, with an extrusion ratio of 22-28 and an extrusion speed of 12-16 mm / s; (6) Post-extrusion treatment: The hot-extruded magnesium alloy is kept at 380-420 °C for 6-8 h and then air-cooled to room temperature.

9. A soluble magnesium alloy with a high temperature controllable narrow corrosion rate prepared by the method of claim 1 or 2, characterized in that: The magnesium alloy is composed of Mg, Zn and Ni as main elements and Ca, Mn and Si as trace elements.

10. A high temperature resistant soluble magnesium alloy with controllable narrow corrosion rate as claimed in claim 9, characterized in that: In the alloy, the components by mass percentage are: Zn is 0.5-3.5%, Ni is 0.8-2%, Ca is 0.01-0.05%, Mn is 0.35-0.55%, Si is 0.1-0.3%, and the rest is Mg.

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