Disclosure of Invention
The invention aims to overcome the defects and provide a preparation method of a high-strength soluble magnesium alloy material.
Through a large amount of experimental research, we find that the cause of the problem of uneven dissolution of the bridge plug material is as follows: the preparation method comprises the steps of preparing a high-strength soluble magnesium alloy material, adding nickel into the magnesium alloy material, controlling the dissolution rate of a well completion tool under a specific condition by controlling the content of nickel and other alloy elements in the magnesium alloy bridge plug material; the melting point of nickel is 1455 ℃, the density is 8.9g/cm3, the melting point of magnesium is 648.8 ℃, the density is 1.748.9g/cm3, and the boiling point is only 1107 ℃; the melting point of nickel is high and the density is high, the temperature of a magnesium alloy smelting furnace is normal and is not higher than 800 ℃, so that great difficulty is brought to smelting if metal nickel is directly added into a magnesium melt in the smelting process of the magnesium alloy material; firstly, the smelting speed is very slow, secondly, because the density is over five times of that of magnesium, the metal nickel added into the magnesium melt is quickly settled at the bottom of the crucible, and an Mg2Ni alloying structure is difficult to form, so that the material is not uniformly dissolved in a specified time, and the construction is influenced.
In order to solve the problem of smelting difficulty, two magnesium-nickel intermediate alloys 1 and Mg25Ni are developed and produced by people, namely the Ni content is (23-27)%; 2. mg30Ni, namely Ni content is (27-32)%; the two magnesium-nickel intermediate alloys are close to a magnesium-nickel eutectic structure, form an MgNi phase, have low melting points and are convenient to add, so that the difficulty in smelting the magnesium alloy product needing to add the nickel element is solved; and the tensile strength and ductility of the magnesium alloy are improved by adding other intermediate alloys and the like.
The invention adopts the following technical scheme:
a preparation method of a high-strength soluble magnesium alloy material comprises the following steps:
(1) making Mg25Ni or Mg30Ni magnesium-nickel master alloy.
(1-1) charging: firstly, starting a power supply of the intermediate frequency furnace or the power frequency furnace, and slowly heating the crucible to dark red; and (3) filling a nickel material around the crucible, filling a magnesium ingot in the middle, and continuously heating the magnesium ingot and the nickel material in an intermediate frequency furnace or a power frequency furnace until the magnesium ingot and the nickel material are melted and stirring.
(1-2) starting to heat and melt after the charging is finished, wherein the melting temperature of the magnesium-nickel intermediate alloy is 920 ℃, and the nickel content is controlled between 23% and 35%.
(1-3) when the metal nickel is melted 2/3, adjusting the heating power to be small, continuously stirring the Mg-Ni alloy melt, observing and monitoring the change condition of the alloy melt temperature, and when the melt temperature reaches 860 ℃, turning off the heating power supply, and controlling the alloy melt temperature to continuously rise as much as possible; when the temperature of the melt is as high as about 900 ℃, the standby cooling material can be properly added until the metal nickel is completely melted into the magnesium melt.
(1-4) when the temperature of the alloy melt is basically stable and does not have a rising trend any more, and the bottom of the crucible is not sensed to have infusible substances when the alloy melt is stirred, the rest cold materials can be gradually added; and adjusting the pouring temperature to 680-760 ℃, pouring into an ingot mold of an ingot casting machine, and cooling for later use.
(2) Preparing a raw magnesium ingot, a zinc ingot, Mg30Gd master alloy, Mg30Y master alloy, Mg30Zr master alloy, Mg30Cu master alloy and Mg30Ni master alloy; sequential loading was started with the crucible pre-heated to a dark red color (about 500 ℃).
(3) Heating to melt and alloying.
(3-1) after the materials are charged, heating and melting are started, when the materials in the crucible are completely melted and the temperature of the melt reaches 700 +/-20 ℃, argon is used for fully stirring the alloy melt, a proper amount of RJ-5 solvent is sprayed, the mixture is made for 10-15 minutes, and then the mixture is kept stand for 15-20 minutes; sampling for the first stokehole component analysis, and removing slag at the bottom of the crucible.
(3-2) preparing and adding alloy elements Zn, Gd, Y, Cu, Ni and Zr according to the analysis result of the components before the first furnace and the total amount of ingredients; except that Zn is directly added with metal zinc; the rest is added with Mg30Gd master alloy, Mg30Y master alloy, Mg30Zr master alloy, Mg30Cu master alloy and Mg30Ni master alloy; all intermediate alloys were preheated to 250-300 ℃ before addition.
(4) Refining; refining the fully alloyed magnesium melt at 750 +/-20 ℃, wherein the refining solvent is RJ-6, refining for about 5 minutes, and then standing for about 10 minutes.
(5) Standing; after refining, cleaning slag around the crucible and slag on the liquid level of the magnesium melt, and spraying a covering agent.
(6) Casting; low-pressure injection and electromagnetic stirring crystallizer are adopted for forming.
(7) And carrying out extrusion forming after homogenizing heat treatment on the cast rod.
At the moment, the tensile strength of the manufactured magnesium alloy is 409 MPa; the dissolution rate is 52.63-58.16mg/cm 2/hr.
Preferably, the step (1-1) is charging: drying moisture in nickel powder particles, starting a power supply of an intermediate frequency furnace or a power frequency furnace, slowly heating a crucible to dark red, putting a magnesium ingot into the middle, continuously heating the crucible by the intermediate frequency furnace or the power frequency furnace until the magnesium ingot is melted, slowly adding nickel powder when the temperature of a magnesium melt is above 700 ℃, and stirring while adding.
Preferably, the cooled cold material in the step (1-3) is magnesium ingot.
Preferably, the adding sequence in the step (3-2) is as follows: zn, Mg30Cu, Mg30Gd, Mg30Ni, Mg30Y, Mg30 Zr; addition temperature: zn is 720-740 ℃; mg30Cu 720-740 ℃; mg30Gd 720-740 ℃; mg30Ni 740-760 ℃; mg30Y 740-760 ℃; mg30Zr 780-800 ℃.
The invention has the beneficial effects that: the magnesium alloy material prepared by the method solves the difficulty of adding nickel element into a magnesium alloy product during smelting, ensures that nickel is uniformly distributed in the magnesium alloy and the magnesium alloy can be uniformly dissolved, and improves the tensile strength and the ductility of the magnesium alloy product by adding metals with different components; the bridge plug for plugging an oil-gas well is manufactured, so that the bridge plug has good tensile strength, keeps the sealing performance, can be uniformly dissolved in a special solution at the later stage, can be completely dissolved in a specified time under the conditions of different geological temperatures and different geological mineralization degrees, and keeps good characteristics.
Detailed Description
In order to make the purpose and technical solution of the present invention clearer, the present invention is further illustrated by the following examples:
a preparation method of a high-strength soluble magnesium alloy material comprises the following steps:
firstly, a Mg25Ni or Mg30Ni Mg-Ni intermediate alloy is prepared.
1.1, charging: firstly, starting a power supply of the intermediate frequency or industrial frequency furnace, and slowly heating the crucible to dark red; if the nickel sheet is used for preheating, the moisture in the nickel powder particles must be dried firstly if the nickel powder particles are used; the heated or unheated nickel plate is arranged around the crucible, the magnesium ingot is arranged in the middle, and the medium-frequency heating furnace and the power-frequency heating furnace can be mixed with magnesium and nickel for charging, so that the nickel plate can be rapidly heated and melted; if the nickel powder particles are selected, the original magnesium ingot can be loaded firstly, after the magnesium ingot is completely melted, the nickel powder is slowly added into the magnesium melt at the temperature of more than 700 ℃, and the nickel powder is stirred while the nickel powder is added.
1.2, starting temperature rise and melting after charging, wherein the metal nickel has high melting point and can be melted only by absorbing a large amount of heat, the magnesium has low melting point, the two alloy elements which are simultaneously loaded into the crucible are melted, the magnesium is melted firstly, and the nickel needs a longer heat absorption process and is slowly melted into the magnesium melt to form an alloy structure, according to the alloy phase diagram theory, the atomic structure theory and the thermodynamic kinetics theory, when the internal temperature of the Mg-Ni system is 512 ℃ and 1082 ℃, two eutectic type non-variable transformations are generated, when 768 ℃, the included crystal type non-variable transformation is generated, and the solid-liquid different component melting property of the compound Mg2Ni at 768 ℃ is determined. And the boiling point of magnesium is 1090 ℃, so the smelting temperature of the magnesium-nickel intermediate alloy is not too high, the highest smelting temperature cannot exceed 920 ℃, and the nickel content is generally controlled to be below 35 percent, thereby being beneficial to adding in the subsequent alloying process.
1.3, after the magnesium is completely melted, the nickel plate in the crucible absorbs a large amount of heat energy and starts to melt slowly, at the moment, the magnesium melt is stirred properly, the melting of the nickel plate is accelerated, a MgNi phase (I is approximately equal to Mg + Mg2Ni) is gradually formed in the Mg-Ni alloy melt along with the heat absorption and melting of the nickel plate, a large amount of heat is released, the temperature of the alloy melt is continuously increased, and the melting speed of the metallic nickel in the magnesium melt is accelerated; when the metallic nickel is melted above 2/3, the heating power supply can be turned off or the heating power can be reduced, the Mg-Ni alloy melt is continuously stirred, the change condition of the alloy melt temperature is observed and monitored, when the melt temperature reaches about 860 ℃, the heating power supply is turned off, and the alloy melt temperature is controlled to continuously rise as much as possible; when the temperature of the melt is as high as about 900 ℃, a standby cooling cold material (magnesium ingot) can be properly added, the temperature of the melt is controlled to continuously rise, the cold material is not required to be added too much at one time, and the supercooling of the alloy melt is not beneficial to the formation of an Mg2Ni phase structure until all the metal nickel is melted into the magnesium melt; the alloy melt is continuously stirred in the whole process, so that the alloying structure of the magnesium-nickel intermediate alloy is uniformly reduced and segregation is gradually reduced; the key control process in the process of melting the Mg-Ni intermediate alloy is that metal nickel absorbs a large amount of heat in the melting process, is gradually melted into a magnesium melt and forms an Mg2Ni phase, and releases a large amount of heat in the process of forming an Mg2Ni structure, so that the temperature of the alloy melt is quickly increased, and a part of magnesium ingots are reserved before charging to be used as cold materials to control the quick increase of the temperature of the alloy melt.
1.4, when the temperature of the alloy melt is basically stable and does not have a rising trend any more, and the bottom of the crucible is not sensed to have infusible substances when the alloy melt is stirred, the rest cold materials can be gradually added; and adjusting the pouring temperature to 680-760 ℃, adjusting the temperature to be too low, ensuring poor fluidity, too high alloy melt to absorb gas seriously and ensuring poor pouring forming, and pouring the alloy melt into an ingot mould of an ingot casting machine and then cooling for later use.
Preparing an original magnesium ingot, a zinc ingot, Mg30Gd master alloy, Mg30Y master alloy, Mg30Zr master alloy, Mg30Cu master alloy and Mg30Ni master alloy; starting to charge in sequence when the crucible is preheated to dark red (about 500 ℃); before charging, firstly, spraying a proper amount of dissolving agent at the bottom and the periphery of a crucible, and loading a large block of foundry returns and magnesium ingots at the upper part; the bridging phenomenon cannot occur; spraying a proper amount of solvent while installing; if the residual materials cannot be completely filled at one time, the residual materials can be gradually added in the process of heating and melting.
Thirdly, heating, melting and alloying.
3.1, starting to heat and melt after the materials are charged, fully stirring the alloy melt by using argon when the temperature of the melt reaches 700 +/-20 ℃, and spraying a proper amount of RJ-5 solvent, wherein the magnesium liquid is prevented from burning, and the alloy melt is refined for the first time and is kept stand for 15-20 minutes after about 10-15 minutes; sampling for the first stokehole component analysis, and removing slag at the bottom of the crucible.
And 3.2, preparing and adding alloy elements Zn, Gd, Y, Cu, Ni and Zr according to the analysis result of the first stokehole component analysis and the total ingredient number. Except that Zn is directly added with metal zinc; the balance of the alloy is added with Mg30Gd master alloy, Mg30Y master alloy, Mg30Zr master alloy, Mg30Cu master alloy and Mg30Ni master alloy; the adding sequence is as follows: zn, Mg30Cu, Mg30Gd, Mg30Ni, Mg30Y, Mg30 Zr; addition temperature: zn is 720-740 ℃; mg30Cu 720-740 ℃; 720-740 ℃ of Mg30 Gd; mg30Ni 740-760 ℃; mg30Y 740-760 ℃; mg30Zr 780-800 ℃; before adding, preheating all alloy elements to 250-300 ℃; the addition process must be carried out slowly with stirring. In the process of adding alloy elements, a proper amount of RJ-5 solvent can be sprayed to prevent the combustion of magnesium liquid; after each alloy element is added, fully stirring for 5 minutes, then adding another alloy element, and after all the alloy elements are added, continuously stirring for fully 10-15 minutes to gradually fully alloy the alloy elements; then adjusting the temperature of the alloy melt to 750 +/-20 ℃ to start refining.
Fourthly, refining; refining the fully alloyed magnesium melt at 750 +/-20 ℃, wherein the refining solvent is RJ-6, the magnesium alloy melt is fully stirred in the refining process without dead corners, a certain amount of refining agent is scattered on wave peaks, and the stirring amplitude is proper so as not to enable magnesium liquid to splash; refining for about 5 minutes, standing for about 10 minutes, and sampling for second stokehole component analysis. If the analysis result does not meet the requirement of the chemical components of the brand, alloy elements are required to be added for the second time until the components meet the requirement. And (4) adding alloy elements for at most 3 times, otherwise re-dissolving after casting. If the alloy reaches the middle limit of the range of the chemical component requirement of the alloy grade through detection, the middle limit and the upper limit of the descending elements during the cooling pouring are taken out to represent the qualification. And (4) continuously refining for 15-20 minutes, wherein the change state of the alloy melt in the refining process is determined to be appropriate if the change state is observed, and if the magnesium melt is observed to turn up and down to be in a mirror surface state, the refining is qualified.
Fifthly, standing; after refining, cleaning slag around the crucible and slag on the liquid level of the magnesium melt, and spraying a covering agent; setting the alloy melt temperature to 750 +/-20 ℃, standing for 20 minutes at high temperature, setting the alloy melt temperature to 730 +/-20 ℃, and standing for 40-60 minutes. And taking a furnace front sample, and performing furnace front component analysis. And unqualified, removing slag at the bottom of the crucible, supplementing alloy elements, alloying, refining and the like, and repeating according to the specification. And if the detection result is qualified, adjusting the alloy melt to the casting temperature of 710 +/-20 ℃ and preparing for casting.
Sixthly, casting; low-pressure injection and electromagnetic stirring crystallizer forming are adopted; the technological parameters are reasonably regulated and controlled in the casting process: alloy melt temperature, pouring speed, water cooling strength, distribution funnel and the like; prevent the cast rod from generating bad defects such as hot crack, cold shut and the like.
Seventhly, carrying out extrusion forming after homogenizing heat treatment on the cast rod; because the cast rod can generate component segregation and shrinkage stress in the rapid solidification process, the machinability of the subsequent process of the cast rod is improved in order to eliminate component area segregation and internal stress existing in the cast rod. Carrying out homogenization heat treatment on the cast rod at the temperature of 410 +/-20 ℃ for 16 hours, then opening a furnace door, cooling the cast rod along with the furnace for 30 minutes, and then withdrawing the furnace chamber for air cooling; and (4) heating the equipment and the bar stock in sections according to the extrusion process requirement to extrude and mold.
The produced magnesium alloy material contains Cu: 0.5-2.5% (by weight), Ni: 0.5-1.5% (by weight), Gd: 8.0-10.0% (by weight), Y: 2.0-4.0% (by weight), Zn: 0.5-2.0% (weight ratio).
The tensile strength properties of the prepared magnesium alloy material samples are as follows:
|
sample number
|
Sample number
|
Tensile strength Rm
|
Rp0.2
|
Elongation after fracture A
|
Unit of
|
|
|
MPa
|
MPa
|
%
|
Sample No. 1
|
1-1
|
φ93-1
|
397.8558
|
336.1346
|
4.56
|
Sample No. 2
|
1-2
|
φ93-2
|
409.3806
|
327.7214
|
5.40
|
Sample No. 3
|
1-3
|
φ93-3
|
405.0152
|
322.1891
|
5.60 |
The dissolution rate of the prepared magnesium alloy material sample is 52.63-58.16mg/cm 2/hr; see the following table for details:
the invention has the beneficial effects that: the magnesium alloy material prepared by the method solves the difficulty of adding nickel element into a magnesium alloy product during smelting, ensures that nickel is uniformly distributed in the magnesium alloy and the magnesium alloy can be uniformly dissolved, and improves the tensile strength and the ductility of the magnesium alloy product by adding metals with different components; the bridge plug for plugging an oil-gas well is manufactured, so that the bridge plug has good tensile strength, keeps the sealing performance, can be uniformly dissolved in a special solution at the later stage, can be completely dissolved in a specified time under the conditions of different geological temperatures and different geological mineralization degrees, and keeps good characteristics.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the technical scope of the present invention, so that any minor modifications, equivalent changes and modifications made to the above embodiment according to the technical spirit of the present invention still belong to the protection scope of the present invention.