CN1974807A - Prepn process of high performance magnesium alloy - Google Patents
Prepn process of high performance magnesium alloy Download PDFInfo
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- CN1974807A CN1974807A CNA2006101021689A CN200610102168A CN1974807A CN 1974807 A CN1974807 A CN 1974807A CN A2006101021689 A CNA2006101021689 A CN A2006101021689A CN 200610102168 A CN200610102168 A CN 200610102168A CN 1974807 A CN1974807 A CN 1974807A
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Abstract
The present invention relates to preparation process of high performance magnesium alloy. By using Mg, Al, Zn and Mn as materials and RE element La as grain fining additive, and through vacuum smelting and chemical reaction under Ar protection to form Mg-Al-Zn-Mn-La alloy liquid, stilling at 720+/-5 deg.c for 5-10 min, casting at 680+/-5 deg.c to form high performance alloy rod, cutting, turning and polishing, high performance magnesium alloy rod is made. The high performance magnesium alloy has less harmful impurity, compact and homogeneous metallurgical structure, fine crystal grains not greater than 40 micron and high mechanical performance.
Description
Technical Field
The invention relates to a preparation method of a high-performance magnesium alloy, belonging to the technical field of non-ferrous metal alloy production process and preparation method.
Background
In the non-ferrous metal alloy, magnesium alloy is one of the lightest metal alloys, the magnesium alloy has many advantages of chemical composition, tissue structure and mechanical property, low density, small specific gravity, high specific strength and specific rigidity, good damping property, electric and thermal conductivity and cutting processability, strong electromagnetic shielding capability, easy processing and forming and easy recovery, and the magnesium alloy with the same volume is 36 percent lighter than the aluminum alloy and 73 percent lighter than the zinc alloy and is widely applied to the technical fields of aviation, electronics, machinery,automobiles, telecommunication and the like.
Although magnesium alloys have many excellent properties, in practical applications, some defects and performance deficiencies, such as low strength, poor plasticity, poor corrosion resistance, etc., are exposed, and thus magnesium and magnesium alloys, as structural metal materials, are limited in many technical fields, for example, cannot replace steel materials having high strength and hardness, and in order to expand the application range of magnesium alloys, it is necessary to improve the strength, toughness and corrosion resistance of magnesium alloys.
Because of the unique chemical and physical properties of magnesium and magnesium alloy, magnesium element is easy to burn and evaporate and easy to oxidize in the preparation and smelting process, under the common smelting condition, a large number of inclusions such as oxycarbide exist in the magnesium alloy matrix, the crystal grain size is large, the yield strength is low, the toughness is poor, the smelting preparation of high-performance magnesium alloy is difficult, and the physical and chemical properties and mechanical properties of the magnesium alloy are greatly influenced.
Disclosure of Invention
Object of the Invention
The invention aims to overcome the defects of the background technology, and adopts a novel smelting technology and a preparation method to inhibit the combustion and evaporation of magnesium elements in the smelting process, remove impurities in the magnesium alloy during smelting, reduce the grain size, greatly improve the physical and mechanical properties of the magnesium alloy and enhance the strength and toughness of the magnesium alloy.
Technical scheme
The magnesium alloy is refined by the following metal elements according to the proportioning requirement of magnesium alloy, and the material composition is as follows: in grams, milliliters and centimeters3As a unit of measure
Magnesium: mg 2650g + -100 g solid block
Aluminum: 280g +/-10 g of Al solid block
Zinc: zn 21g +/-5 g solid block
Manganese: mn 4g +/-1 g solid powder
Lanthanum: la 30g +/-3 g solid powder
Acetone: 1000ml +/-5 ml of liquid
Argon gas: ar 100000cm3±1000cm3Gaseous gas
The preparation process method of the invention comprises the following steps:
(1) selecting chemical feedstock
The raw materials and auxiliary materials of the chemical substances required by the preparation are selected, and the purity and content are controlled as follows:
magnesium: 99.9 percent of Mg
Aluminum: 99.9 percent of Al
Zinc: 99.9 percent of Zn
Manganese: 99.9 percent of Mn
Lanthanum: la 99.9%
Acetone: 99.1 percent
Argon gas: 99.2 percent
(2) Precutting of block material
The block materials of magnesium, aluminum and zinc used for preparation are pre-cut into small blocks which are easy to add, and the size of each block is as follows: less than or equal to 35 x 65mm
(3) Prefabricated forming die
Prefabricating a forming die required by refining and casting
The shape of the die is as follows: the mold body is made of stainless steel;
(4) refined magnesium alloy
① refining magnesium alloy is carried out in a magnesium alloy smelting furnace, which is of vertical structure and mainly comprises a workbench, a furnace body, a furnace frame, a heater, a charging hole, an observation window, a vacuum pump, an argon gas input mechanism, a water circulation cooling mechanism, a resistance cabinet, an electric control cabinet, a smelting crucible, a mold disc, a furnace cover lifting mechanism and a stirrer;
②, cleaning and washing the smelting furnace chamber;
opening the smelting furnace, and sucking dust and harmful substances in the furnace cavity by using a dust collector for 5min +/-1 min;
scrubbing the sealing positions of the furnace cover, the edge of the furnace body, the observation window and the feeding bin opening by using 1000ml +/-5 ml of acetone to ensure that the furnace cover is clean and well sealed;
③ cleaning and washing smelting crucible
Sucking dust and harmful substances in the crucible by using a dust collector, wherein the sucking time is 3min +/-1 min;
removing residues in the crucible by using a special metal brush shovel to enable the inner surface of the crucible to be smooth;
④ preheating mould
Preheating the opening-closing type E-shaped die at the preheating temperature of 300 +/-10 ℃ for 30 +/-5 min;
⑤ charging
2650g of magnesium, 260g of aluminum, 21g of zinc block and 4g of manganese powder are placed in a melting crucible; placing 30g of lanthanum powder into a lanthanum-added aluminum shell weighing 20g, and placing the lanthanum powder into a feeding bin opening of a smelting furnace;
⑥ opening water circulation cooling mechanism
Closing the furnace body and the furnace cover, opening connecting valves of the rotary vane pump, the roots pump, the oil diffusion pump and the water flow pipeline, and starting water flow circulation cooling;
⑦ vacuumizing smelting furnace
Closing the smelting furnace to seal the smelting furnace;
starting the rotary vane pump, the Roots pump and the low vacuum valve to pump out air in the furnace, closing the Roots pump and the low vacuum valve when the pressure value in the furnace reaches below 10Pa, opening the oil diffusion pump and the high vacuum valve to continuously pump high vacuum, and when the pressure value in the furnace reaches 10Pa-3When Pa, the rotary vane pump, the oil diffusion pump and the high vacuum valve are closed;
⑧ argon gas is input into the smelting furnace
Starting an argon pump, an argon valve and an argon flowmeter, and inputting inert gas-argon into the smelting furnace at the input speed of 10000cm3Min, wherein the input time is 6min +/-1 min, and when the pressure value in the smelting furnace reaches 150Pa, the argon pump is closed;
⑨ melting Start
Starting a heater to raise the temperature of the crucible to 720 +/-5 ℃, wherein the temperature raising speed is 10 ℃/min, and the temperature raising time is 70min +/-15 min;
melting magnesium, aluminum, zinc and manganese in the crucible, and converting the solid state into the liquid state;
⑩ adding intermediate alloy of rare earth element lanthanum
Rapidly adding 30g of lanthanum powder and 20g of lanthanum-added aluminum shell into a melting crucible through a feeding bin opening, wherein the adding time is 0.5min +/-0.2 min;
after adding, stirring the melt in the crucible by using a stirrer for 1min +/-0.5 min; melting the mixture to form a magnesium-aluminum-zinc-manganese-lanthanum alloy melt;
observing the smelting condition and the condition of the mixed molten liquid after lanthanum is added through an observation window;
_. standing the molten Mg-Al-Zn-Mn-La alloy
After the rare earth element lanthanum is added, standing for 5-10min at the temperature of 720 +/-5 ℃;
the magnesium-aluminum-zinc-manganese-lanthanum alloy melt generates chemical reaction in the smelting process, and the reaction formula is as follows:
mn can reduce the solid solubility of harmful element Fe in the alloy, so that Mn is precipitated at the bottom of the crucible and does not participate in chemical reaction;
in the formula, MgO-magnesia
La2O3Lanthanum sesquioxide
Fe-iron
_. temperature reduction
Cooling the molten magnesium-aluminum-zinc-manganese-lanthanum alloy after standing, and adjusting the input power of the resistance furnace to reduce the temperature of the molten magnesium-aluminum-zinc-manganese-lanthanum alloy from 720 +/-5 ℃ to 680 +/-5 ℃;
_. casting alloy
Aligning a smelting crucible to a casting opening of the mold, and inclining the smelting crucible, wherein the crucible is gradually inclined from a vertical state to a horizontal state;
the alloy melt in the crucible is slowly poured into a die casting port provided with a ceramic zirconia filter screen, and when the die cavity is filled with the alloy melt, the casting is stopped;
observing the casting state through an observation window;
_. naturally cooling with the furnace
After the casting is finished, the heater is turned off, and the heating is stopped;
the temperature in the smelting furnace is gradually cooled from 720 +/-5 ℃, the cooling speed is 15 ℃/min, and the temperature is cooled to 100 +/-5 ℃;
_. taking out the casting
When the temperature in the furnace is reduced to be less than or equal to 100 +/-5 ℃, closing the water circulating cooling mechanism;
taking out the casting mold and the casting;
_. casting cooling and demoulding
After the casting is taken out, the casting is buried in fine sand and continuously and naturally cooled to 30 +/-3 ℃;
after the casting is cooled by thermal expansion, opening the die carrier, demoulding the casting, and taking out the casting;
(5) cutting and forming
Cutting the casting after the precision casting and demolding to form three cylindrical rod-shaped branches with the diameter of 35 multiplied by 200 mm;
(6) finish turning cylindrical rod
Respectively carrying out finish turning on three precision-cast and cut cylindrical rods with the diameter of 35 multiplied by 200mm, wherein the roughness of the excircle and the end face is Ra0.032-0.064 mu m;
(7) polishing cylindrical rod
Placing the magnesium alloy rod on a polishing machine, and respectively and mechanically polishing the excircle and the end face of the magnesium alloy, wherein the surface roughness Ra of the excircle and the end face is 0.016-0.032 mu m;
(8) detection, analysis, characterization
①, detecting the appearance, color, appearance, size, air hole, crack, cold shut, slag and spot of the magnesium alloy rod formed by refining;
②, detecting the chemical components and the content of magnesium, aluminum, zinc, manganese and lanthanum in the magnesium alloy rod;
③, detecting the mechanical properties of the magnesium alloy bar, such as tensile strength, yield strength, toughness, impact energy, elongation, etc.;
④, detecting internal impurities and inclusion carbon and oxygen elements of the magnesium alloy rod;
⑤, detecting the internal crystal grain size of the magnesium alloy bar and analyzing the diffraction intensity;
⑥, metallographic analysis is carried out on the longitudinal and transverse sections of the magnesium alloy rod;
(9) packing and storing
Packaging the prepared and molded magnesium alloy rod by using a soft material to prevent collision and impact damage;
storing in a cool and dry environment at 20 + -3 deg.C and relative humidity less than or equal to 40%, and preventing water, moisture and alkali.
The refining preparation of the high-performance magnesium alloy is carried out in a smelting furnace under the condition of water circulation cooling, the smelting temperature is increased from 20 +/-3 ℃, the temperature increasing speed is 10 ℃/min, the temperature increasing time is 70 +/-15 min, the temperature is increased to 720 +/-5 ℃, the temperature is kept constant, standing is carried out for 5-10min, rare earth element lanthanum is added at the temperature, then the temperature is reduced to 680 +/-5 ℃, the temperature is the casting temperature, the temperature is reduced after the casting is finished, the temperature reducing speed is 15 ℃/min, the temperature is reduced to 100 +/-5 ℃, the smelting furnace is started, the water circulation cooling is closed, a casting is taken out, and the casting is naturally cooled to 20 +/-3 ℃ after being buried in fine sand.
The smelting of the high-performance magnesium alloy takes magnesium, aluminum, zinc and manganese as raw materials, takes rare earth element-lanthanum as an additive, takes acetone as a smelting furnace cleaning agent, takes inert gas-argon as protective gas, and takes circulating water as a coolant during smelting.
The smelting of the high-performance magnesium alloy is carried out under the protection of inert gas-argon in the whole process, and the input speed of the argon is 10000cm3Min, input time of 6min + -1 min, total input amount of 60000cm3±1000cm3After argon is input, the pressure value in the smelting furnace is constant at 150Pa +/-10 Pa.
The smelting of the high-performance magnesium alloy is carried out in a crucible of a smelting furnace,the casting is carried out after the smelting, the filtering is carried out, a ceramic zirconia filter screen is placed on a casting gate of a casting die, the porosity of the filter screen is more than or equal to 85%, and the filtering is finished in the process of casting the magnesium alloy melt.
The casting mould is of an open-close type Chinese character 'shan', a casting opening 41 is formed in the middle of the casting mould 40, a ceramic zirconia filter screen 37 is arranged on the casting opening 41, a magnesium rod core cavity 42 is formed in the left side of the casting opening 41, a magnesium rod core cavity 43 is formed in the right side of the casting mould 40, open- close frames 44 and 45 are arranged on the outer left side of the casting mould 40 and are opened and closed and fixed through bolts 48 and 49, open-close frames 46 and 47 are arranged on the right side of the casting mould 40 and are respectively opened and closed and fixed through bolts 50 and 51, and the bottoms of the casting opening 41 and the magnesium rod core cavities.
The rare earth element lanthanum powder is added after being sealed by a lanthanum-added aluminum shell weighing 20g, the lanthanum powder is quickly added into a feeding bin opening of a smelting furnace, the adding time is 0.5min +/-0.2 min, the added aluminum shell and the lanthanum powder are melted in a crucible together, and the melted aluminum shell and the lanthanum powder are mixed and smelted with magnesium, aluminum, zinc and manganese in the crucible to form magnesium, aluminum, zinc, manganese and lanthanum alloy melt.
Advantageous effects
Compared with the background technology, the invention has obvious advancement, which takes magnesium, aluminum, zinc and manganese as raw materials and takes rare earth element-lanthanum as a grain refining additive, refining and casting the magnesium alloy rod in a vacuum smelting furnace under the protection of argon in the whole process and under the cooling of water circulation, and preparing the high-performance magnesium alloy rod through cutting forming, mechanical polishing and tissue refining, thereby removing harmful substances in the magnesium alloy, greatly improving the strength and toughness of the magnesium alloy, the tensile strength can be improved by 62.5 percent, the elongation can be improved by 8 times, the compactness of the internal structure of the alloy is enhanced, the mechanical property is stable and excellent, the preparation method has short process flow, little environmental pollution and high mechanical property, under the gravity casting condition, the tensile strength can be improved to 260MPa, the metallographic structure is compact and uniform, and the average grain size is less than or equal to 40 mu m, so that the preparation method is an ideal high-performance magnesium alloy.
Drawings
FIG. 1 is a flow chart of a preparation process
FIG. 2 is a front view of a refining furnace
FIG. 3 is a top view of a refining furnace
FIG. 4 is a side view of a finer
FIG. 5 is a top view of the furnace with the lid removed
FIG. 6 is a view showing the position of the crucible and the mold turntable
FIG. 7 is a front view of a casting mold
FIG. 8 is a plan view of a casting mold
FIG. 9 is a side view of a casting mold
FIG. 10 is a cross-sectional view taken along line A-A of FIG. 8
FIG. 11 is a view showing the structure of a lanthanum-added aluminum case
FIG. 12 is a cross-sectional view taken along line C-C of FIG. 11
FIG. 13 is a diagram of the relation between the melting temperature and the time coordinate
FIG. 14 is a front view of a magnesium alloy rod
FIG. 15 is a cross-sectional view taken along line B-B of FIG. 12
FIG. 16 is a diffraction intensity state diagram of a magnesium alloy structure
FIG. 17 is a gold phase diagram of a magnesium alloy rod with a cross section magnified by 200 times
FIG. 18 is a table showing the effect of different addition amounts of rare earth element-lanthanum on the performance index change of magnesium alloy
As shown in the figure, the list of codes is as follows:
1 furnace body, 2 furnace covers, 3 electric control cabinets, 4 resistance cabinets, 5 instrument panels, 6 stirrers, 7 furnace cover stretching rods, 8 observation windows, 9 observation windows, 10 crucibles, 11 tilting pull rods, 12 crucible tilting motors, 13 mould discs, 14 high vacuum oil diffusion pumps, 15 roots pumps, 16 rotary vane pumps, 17 water circulation mechanisms, 18 argon gas bottles, 19 argon gas pipes, 20 feeding bin ports, 21 working tables, 22 ladders, 23 mould motors, 24 water cooling pipes, 25 water cooling pipes, 26 outer furnace walls, 27 inner furnace walls, 28 water circulation cooling boxes, 29 crucible bases, 30 crucible gates, 31 water cooling pipes, 32 furnace chambers, 33 crucible gates, 34 lanthanum aluminum shells, 35 lanthanum aluminum shell plugs, 36 lanthanum aluminum shell chambers, 37 ceramic zirconium oxide filter screens, 38, 39 high vacuum valves, 40 casting moulds, 41 casting mould ports, 42 magnesium rod core chambers, 43 magnesium rod chambers, 44 opening and closing frames, 45 opening and 46 opening and closing frames, 47 open and close frame, 48 bolts, 49 bolts, 50 bolts, 51 bolts and 52 low vacuum valves.
Detailed description of the preferred embodiments
The invention is further described below with reference to the accompanying drawings:
FIG. 1 shows a flow chart of a preparation process, which is carried out strictly according to the preparation process and is operated sequentially.
The chemical substance proportion required by the preparation is set by scientific calculation in grams, milliliters and centimeters3The magnesium alloy is a metering unit, and can be adjusted and determined according to the requirements of the magnesium alloy when industrially prepared.
The purity and the element content of the required chemical substances are strictly controlled so as to avoid influencing the performance of the magnesium alloy and prevent the generation of byproducts, and the block material is pre-cut according to the size of a crucible when being smelted, so that the smelting addition is convenient.
The electric resistance furnace for smelting magnesium alloy is cleaned, and the sealed part is cleaned by suction of a dust collector and acetone cleaning.
The furnace chamber is firstly vacuumized, then argon is input, and the high vacuum oil diffusion pump 14, the roots pump 15 and the rotary vane pump 16 are used for sequentially vacuuming from high to low to ensure that the pressure value in the furnace chamber is 10-3When Pa is needed, vacuumizing is stopped, then argon gas is started to be input, and the argon gas is input through an argon gas bottle 18 and an argon gas pipe 19 at the input speed of 10000cm3Min, input time 6min,total argon input of 60000cm3When the pressure value in the furnace rises to 150Pa, the argon is closedAnd (5) stopping argon conveying in the gas cylinder.
The raw materials in the crucible are required to be loaded into blocks according to the amount and are strictly controlled.
Lanthanum powder is filled into a lanthanum-added aluminum shell made of pure aluminum to facilitate rapid addition during smelting, a lanthanum-added aluminum shell cavity 36 is arranged inside the lanthanum-added aluminum shell 34, a lanthanum-added aluminum shell plug 35 is arranged outside the lanthanum-added aluminum shell, the sum of the weight of the lanthanum-added aluminum shell 34 and the weight of the lanthanum-added aluminum shell plug 35 is 20g, the sum is contained in the total weight of aluminum elements, and the lanthanum powder are melted together in a crucible after lanthanum is added.
The temperature in the smelting furnace is controlled by a resistance cabinet 4, the temperature is raised from 20 +/-3 ℃, the temperature raising speed is 10 ℃/min, when the temperature is raised to 720 ℃, the raw material block is completely melted, a lanthanum-added aluminum shell 34 containing 30g of lanthanum powder is added from a feeding bin opening 20, and then a stirrer 6 is used for stirring.
Standing at 720 +/-5 ℃ for 5-10min after stirring, and carrying out chemical reaction on chemical substances of magnesium, aluminum, zinc, manganese and lanthanum in the furnace under the protection of inert gas argon at high temperature.
The chemical material used for smelting the high-performance magnesium alloy can also use a magnesium alloy ingot with the mark of AZ91 as the raw material, the AZ91 magnesium alloy ingot contains 90 percent of magnesium, 9 percent of aluminum, 0.7 percent of zinc and 0.3 percent of other elements, and the element ratio of AZ91 is fixed, so the amount of the magnesium element must be adjusted according to the evaporation rate of the magnesium, and the chemical material is used when being specially needed.
Smelting and standing for 5-10min, then cooling, when the temperature is reduced from 720 +/-5 ℃ to 680 +/-5 ℃, casting, starting a crucible tilting motor 12, pulling a crucible 10 to tilt towards the direction of a mold by a tilting pull rod 11, tilting the crucible from a vertical state to a horizontal state, aligning a mold gate 41 of a mold 40 on a mold disc 13 and a ceramic zirconia filter screen 37, and starting casting magnesium alloy melt, wherein the ceramic zirconia filter screen 37 filters the melt in the casting process, and in the casting process, a mold rotating motor 23 is started to drive the mold disc 13 and the mold 40 to rotate, so that the melt is uniform in the mold, element precipitation is prevented from generating bubbles, and the rotation speed is 10 r/min.
After casting, the heater is closed, the mixture is naturally cooled under the protection of argon gas under the condition of water circulation cooling, and the mixture is cooled to 100 +/-5 ℃ from 680 +/-5 ℃.
The water circulation cooling is completed by a water circulation cooling mechanism 17 and a water-cooling pipe 31, the furnace body 1, the furnace cover 2 and the furnace bottom 38 are of a double-layer inner and outer wall structure, the middle part is a water-cooling cavity 28, and the water-cooling pipe 31 is connected with the water-cooling cavity 28, so that the furnace body 1, the furnace cover 2 and the furnace bottom 38 are under the water circulation cooling in the whole process.
And when the temperature is naturally cooled to 100 +/-5 ℃ along with the furnace, closing the water cooling mechanism 17, opening the furnace cover 2, taking out the mold 40, burying the whole mold 40 into fine sand, and continuously and naturally cooling. And when the temperature is cooled to 30 +/-3 ℃, taking out the mold, opening the opening and closing frames 44, 45, 46 and 47 of the mold 40, demolding the casting, and taking out the cast ingot, wherein the cast ingot is in a Chinese character 'shan'.
The V-shaped ingot is mechanically cut into three magnesium alloy rods with the diameter of 35 multiplied by 200mm, and harmful elements are precipitated at the lower part of the casting opening 41, so that the V-shaped ingot is not used because the internal structure is not uniform.
The cut magnesium alloy rod is finely turned into a cylindrical rod shape and then polished, and the surface roughness is Ra0.016-0.032 mu m.
The magnesium alloy rod after refining and finish machining needs to be tested for appearance, color, appearance, air hole, crack, cold shut, slag, spot mark and component content, and mechanical properties such as tensile strength, toughness, elongation, impact energy and the like, and the internal structure and the grain size are analyzed and measured, and the cross section and the longitudinal section are analyzed in a metallographic mode.
The packaging and storage are carried out carefully, moisture protection and oxidation resistance are required, the storage temperature is 20 +/-3 ℃, and the relative humidity is less than or equal to 40%.
Fig. 2, 3, 4, 5 and 6 show a structure diagram of a smelting furnace, wherein a furnace body 1 is in a round pot shape, the upper part of the furnace body 1 is a furnace cover 2, and a feeding bin port 20, observation windows 8 and 9, a stirrer 6 and a stirrer lifting rod 7 are arranged on the furnace cover 2; the middle part of the interior of the furnace body 1 is provided with a crucible 10, the side part is provided with a mould disc 13, and the lower part is provided with a crucible tilting motor 12 and a mould rotating motor 23; the left side of the furnace body 1 is provided with a crucible tilting pull rod 11 and an argon pipe 19 which are connected with an argon bottle 18; high vacuum oil diffusion pump 14, high vacuum valve 39, lobe pump 15, low vacuum valve 52, rotary vane pump 16 are connected gradually to the right side of furnace body 1, water circulative cooling mechanism is established at rotary vane pump 16 rear portion, preceding workstation 21, the platform ladder 22 of being equipped with of furnace body 1, the left part of furnace body 1 is equipped with automatically controlled cabinet 3, resistance cabinet 4, be equipped with panel board 5 on the automatically controlled cabinet 3, furnace body 1, bell 2 are bilayer structure, be circulating water cooling chamber 28 between outer oven 26, the interior oven 27, circulating water cooling chamber 28 passes through pipeline 31 and water circulative mechanism 17 UNICOM.
A crucible 10 is arranged in the middle of a furnace chamber 32 in the furnace body 1, the left side of the crucible 10 is pulled by a crucible pull rod 11, a crucible sprue 33 is arranged on the side part of the crucible 10 and is aligned with a mould 40 placed on a mould disc 13, a crucible tilting motor 12 is arranged at the lower part of the crucible 10, and a mould rotating motor 23 is arranged at the lower part of the mould disc 13.
Fig. 7, 8, 9 and 10 are structural diagrams of a casting mold, wherein the casting mold is specially manufactured according to the requirement of magnesium alloy, can be in an open-close type Chinese character 'shan' shape, can also be in other shapes so as to facilitate casting and demolding, and is manufactured by selecting stainless steel or mold steel with high strength, high hardness and high temperature resistance and is subjected to preheating treatment.
The open-close type E-shaped mould 40 is internally provided with a ceramic zirconia filter screen 37, is sequentially provided with a magnesium rod core cavity 42, a pouring gate 41 and a magnesium rod core cavity 43 in the middle and communicated with each other, is open-close type outside and is two shells with the same shape, is combined to form a complete mould structure, and is connected and fastened by left, right, upper and lower open- close frames 44, 45, 46 and 47 and bolts 48, 49, 50 and 51.
Fig. 11 and 12 show the structure of the lanthanum-added aluminum shell, in which a lanthanum-added aluminum shell cavity 36 is arranged inside the lanthanum-added aluminum shell 34, and a lanthanum-added aluminum shell plug 35 is arranged outside the lanthanum-added aluminum shell.
FIG. 13 is a graph showing the relationship between the melting temperature and the time, wherein the ordinate is the temperature, the abscissa is the time min, the temperature is raised from 20 ℃. + -. 3 ℃ to the point A, namely 720 ℃, kept at a constant temperature, kept for 5-10min, namely an A-B section, then cooled, lowered from the point B to the point C, namely a point 680 ℃, then cooled to the point D, namely a point 100 ℃, and cooled in fine sand to the point E, namely a point 30 ℃.
FIGS. 14 and 15 show magnesium alloy bars, which have outer circle and end surface roughness of Ra0.016-0.032 μm.
FIG. 16 is a diffraction chart showing the crystal grains of a magnesium alloy structure, in which △ represents Mg and ○ represents Mg, with the ordinate being a relative intensity index and the abscissa being a diffraction angle 2. theta17Al12And □ represents Al11La3And ◇ represents Mg2Zn11The diffraction intensity index of magnesium is the highest, the diffraction intensity index of magnesium-aluminum is the second order, the diffraction intensity index of magnesium-zinc is lower, and the diffraction intensity index of aluminum-lanthanum is the lowest.
FIG. 17 is a metallographic analysis chart showing a magnesium alloy rod cross section magnified by 200 times, in which: the internal structure has uniform crystal grains, the size of the crystal grains is obviously reduced to be less than or equal to 40 mu m, no air bubbles exist, and the unit of a scale is 50 mu m.
FIG. 18 is a table showing the performance index variation of different addition amounts of rare earth element-lanthanum, which shows that the addition amount of lanthanum directly affects the performance of the magnesium alloy, the tensile strength MPa, the hardness HV, the impact energy J are proportional to the content of lanthanum, the elongation is highest in percentage of the lanthanum content, and the grain size is inversely proportional to the lanthanum content.
Claims (7)
1. A preparation method of high-performance magnesium alloy is characterized by comprising the following steps: the magnesium alloy is refined by the following metal elements according to the proportioning requirement of magnesium alloy, and the material composition is as follows: taking g, ml and cm 3 as measurement units
Magnesium: mg 2650g + -100 g solid block
Aluminum: 280g +/-10 g of Al solid block
Zinc: zn 21g +/-5 g solid block
Manganese: mn 4g +/-1 g solid powder
Lanthanum: la 30g +/-3 g solid powder
Acetone: 1000ml +/-5 ml of liquid
Argon gas: ar 100000em3±1000cm3Gaseous gas
The preparation process method of the invention comprises the following steps:
(1) selecting chemical feedstock
The raw materials and auxiliary materials of the chemical substances required by the preparation are selected, and the purity and content are controlled as follows:
magnesium: 99.9 percent of Mg
Aluminum: 99.9 percent of Al
Zinc: 99.9 percent of Zn
Manganese: 99.9 percent of Mn
Lanthanum: la 99.9%
Acetone: 99.1 percent
Argon gas: 99.2 percent
(2) Precutting of block material
The block materials of magnesium, aluminum and zinc used for preparation are pre-cut into small blocks which are easy to add, and the size of each block is as follows: less than or equal to 35 x 65mm
(3) Prefabricated forming die
Prefabricating a forming die required by refining and casting
The shape of the die is as follows: the mold body is made of stainless steel;
(4) refined magnesium alloy
① refining magnesium alloy is carried out in a magnesium alloy smelting furnace, which is of vertical structure and mainly comprises a workbench, a furnace body, a furnace frame, a heater, a charging hole, an observation window, a vacuum pump, an argon gas input mechanism, a water circulation cooling mechanism, a resistance cabinet, an electric control cabinet, a smelting crucible, a mold disc, a furnace cover lifting mechanism and a stirrer;
②, cleaning and washing the smelting furnace chamber;
opening the smelting furnace, and sucking dust and harmful substances in the furnace cavity by using a dust collector for 5min +/-1 min;
scrubbing the sealing positions of the furnace cover, the edge of the furnace body, the observation window and the feeding bin opening by using 1000ml +/-5 ml of acetone to ensure that the furnace cover is clean and well sealed;
③ cleaning and washing smelting crucible
Sucking dust and harmful substances in the crucible by using a dust collector, wherein the sucking time is 3min +/-1 min;
removing residues in the crucible by using a special metal brush shovel to enable the inner surface of the crucible to be smooth;
④ preheating mould
Preheating the opening-closing type E-shaped die at the preheating temperature of 300 +/-10 ℃ for 30 +/-5 min;
⑤ charging
2650g of magnesium, 260g of aluminum, 21g of zinc block and 4g of manganese powder are placed in a melting crucible; placing 30g of lanthanum powder into a lanthanum-added aluminum shell weighing 20g, and placing the lanthanum powder into a feeding bin opening of a smelting furnace;
⑥ opening water circulation cooling mechanism
Closing the furnace body and the furnace cover, opening connecting valves of the rotary vane pump, the roots pump, the oil diffusion pump and the water flow pipeline, and starting water flow circulation cooling;
⑦ vacuumizing smelting furnace
Closing the smelting furnace to seal the smelting furnace;
starting the rotary vane pump, the Roots pump and the low vacuum valve to pump out air in the furnace, closing the Roots pump and the low vacuum valve when the pressure value in the furnace reaches below 10Pa, opening the oil diffusion pump and the high vacuum valve to continuously pump high vacuum, and when the pressure value in the furnace reachesUp to 10-3When Pa, the rotary vane pump, the oil diffusion pump and the high vacuum valve are closed;
⑧ argon gas is input into the smelting furnace
Starting an argon pump, an argon valve and an argon flowmeter, and inputting inert gas-argon into the smelting furnace at the input speed of 10000cm3Min, wherein the input time is 6min +/-1 min, and when the pressure value in the smelting furnace reaches 150Pa, the argon pump is closed;
⑨ melting Start
Starting a heater to raise the temperature of the crucible to 720 +/-5 ℃, wherein the temperature raising speed is 10 ℃/min, and the temperature raising time is 70min +/-15 min;
melting magnesium, aluminum, zinc and manganese in the crucible, and converting the solid state into the liquid state;
⑩ adding intermediate alloy of rare earth element lanthanum
Rapidly adding 30g of lanthanum powder and 20g of lanthanum-added aluminum shell into a melting crucible through a feeding bin opening, wherein the adding time is 0.5min +/-0.2 min;
after adding, stirring the melt in the crucible by using a stirrer for 1min +/-0.5 min; melting the mixture to form a magnesium-aluminum-zinc-manganese-lanthanum alloy melt;
observing the smelting condition and the condition of the mixed molten liquid after lanthanum is added through an observation window;
_. standing the molten Mg-Al-Zn-Mn-La alloy
After the rare earth element lanthanum is added, standing for 5-10min at the temperature of 720 +/-5 ℃;
the magnesium-aluminum-zinc-manganese-lanthanum alloy melt generates chemical reaction in the smelting process, and the reaction formula is as follows:
mn can reduce the solid solubility of harmful element Fe in the alloy, so that Mn is precipitated at the bottom of the crucible and does not participate in chemical reaction;
in the formula, MgO-magnesia
La2O3Lanthanum sesquioxide
Fe-iron
_. temperature reduction
Cooling the molten magnesium-aluminum-zinc-manganese-lanthanum alloy after standing, and adjusting the input power of the resistance furnace to reduce the temperature of the molten magnesium-aluminum-zinc-manganese-lanthanum alloy from 720 +/-5 ℃ to 680 +/-5 ℃;
_. casting alloy
Aligning a smelting crucible to a casting opening of the mold, and inclining the smelting crucible, wherein the crucible is gradually inclined from a vertical state to a horizontal state;
the alloy melt in the crucible is slowly poured into a die casting port provided with a ceramic zirconia filter screen, and when the die cavity is filled with the alloy melt, the casting is stopped;
observing the casting state through an observation window;
_. naturally cooling with the furnace
After the casting is finished, the heater is turned off, and the heating is stopped;
the temperature in the smelting furnace is gradually cooled from 720 +/-5 ℃, the cooling speed is 15 ℃/min, and the temperature is cooled to 100 +/-5 ℃;
_. taking out the casting
When the temperature in the furnace is reduced to be less than or equal to 100 +/-5 ℃, closing the water circulating cooling mechanism;
taking out the casting mold and the casting;
_. casting cooling and demoulding
After the casting is taken out, the casting is buried in fine sand and continuously and naturally cooled to 30 +/-3 ℃;
after the casting is cooled by thermal expansion, opening the die carrier, demoulding the casting, and taking out the casting;
(5) cutting and forming
Cutting the casting after the precision casting and demoulding into three cylindrical rod-shaped pieces with phi of 35 multiplied by 200 mm;
(6) finish turning cylindrical rod
Finely turning three precision-cast and cut cylindrical rods with the diameter of 35 multiplied by 200mm respectively, wherein the roughness of the excircle and the end face is Ra0.032-0.064 mu m;
(7) polishing cylindrical rod
Placing the magnesium alloy rod on a polishing machine, and respectively and mechanically polishing the excircle and the end face of the magnesium alloy, wherein the surface roughness Ra of the excircle and the end face is 0.016-0.032 mu m;
(8) detection, analysis, characterization
①, detecting the appearance, color, appearance, size, air hole, crack, cold shut, slag and spot of the magnesium alloy rod formed by refining;
②, detecting the chemical components and the content of magnesium, aluminum, zinc, manganese and lanthanum in the magnesium alloy rod;
③, detecting the mechanical properties of the magnesium alloy bar, such as tensile strength, yield strength, toughness, impact energy, elongation, etc.;
④, detecting internal impurities and inclusion carbon and oxygen elements of the magnesium alloy rod;
⑤, detecting the internal crystal grain size of the magnesium alloy bar and analyzing the diffraction intensity;
⑥, metallographic analysis is carried out on the longitudinal and transverse sections of the magnesium alloy rod;
(9) packing and storing
Packaging the prepared and molded magnesium alloy rod by using a soft material to prevent collision and impact damage;
storing in a cool and dry environment at 20 + -3 deg.C and relative humidity less than or equal to 40%, and preventing water, moisture and alkali.
2. The method for preparing the high-performance magnesium alloy according to claim 1, wherein the method comprises the following steps: the refining preparation of the high-performance magnesium alloy is carried out in a smelting furnace under the condition of water circulation cooling, the smelting temperature is increased from 20 +/-3 ℃, the temperature increasing speed is 10 ℃/min, the temperature increasing time is 70 +/-15 min, the temperature is increased to 720 +/-5 ℃, the temperature is kept constant, standing is carried out for 5-10min, rare earth element lanthanum is added at the temperature, then the temperature is reduced to 680 +/-5 ℃, the temperature is the casting temperature, the temperature is reduced after the casting is finished, the temperature reducing speed is 15 ℃/min, the temperature is reduced to 100 +/-5 ℃, the smelting furnace is started, the water circulation cooling is closed, a casting is taken out, and the casting is naturally cooled to 20 +/-3 ℃ after being buried in fine sand.
3. The method for preparing the high-performance magnesium alloy according to claim 1, wherein the method comprises the following steps: the smelting of the high-performance magnesium alloy takes magnesium, aluminum, zinc and manganese as raw materials, takes rare earth element-lanthanum as an additive, takes acetone as a smelting furnace cleaning agent, takes inert gas-argon as protective gas, and takes circulating water as a coolant during smelting.
4. The method for preparing the high-performance magnesium alloy according to claim 1, wherein the method comprises the following steps: the smelting of the high-performance magnesium alloy is carried out under the protection of inert gas-argon in the whole process, and the input speed of the argon is 10000cm3Min, input time of 6min + -1 min, total input amount of 60000cm3±1000cm3After argon is input, the pressure value in the smelting furnace is constant at 150Pa +/-10 Pa.
5. The method for preparing the high-performance magnesium alloy according to claim 1, wherein the method comprises the following steps: the smelting of the high-performance magnesium alloy is carried out in a crucible of a smelting furnace, the casting is carried out after the smelting, the filtering is carried out, a ceramic zirconia filter screen is placed on a casting gate of a casting die, the porosity of the filter screen is more than or equal to 85%, and the filtering is finished in the process of casting the magnesium alloy melt.
6. The method for preparing the high-performance magnesium alloy according to claim 1, wherein the method comprises the following steps: the casting mould be open-close type chevron, casting die utensil (40) middle inside is casting gate (41), be equipped with ceramic zirconia filter screen (37) on casting gate (41), casting gate (41) left side is magnesium rod core chamber (42), the right side is magnesium rod core chamber (43), the outer left side of casting die utensil (40) is for opening and shutting frame (44), (45), and open and shut fixedly by bolt (48), (49), casting die utensil (40) right side is for opening and shutting frame (46), (47), open and shut fixedly by bolt (50), (51) respectively, casting gate (41), magnesium rod core chamber (42), (43) bottom communicate mutually.
7. The method for preparing the high-performance magnesium alloy according to claim 1, wherein the method comprises the following steps: the rare earth element lanthanum powder is added after being sealed by a lanthanum-added aluminum shell weighing 20g, the lanthanum powder is quickly added into a feeding bin opening of a smelting furnace, the adding time is 0.5min +/-0.2 min, the added aluminum shell and the lanthanum powder are melted in a crucible together, and the melted aluminum shell and the lanthanum powder are mixed and smelted with magnesium, aluminum, zinc and manganese in the crucible to form magnesium, aluminum, zinc, manganese and lanthanum alloy melt.
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| CN103184358A (en) * | 2013-04-01 | 2013-07-03 | 太原理工大学 | Reinforcing and toughening method for magnesium aluminium intermetallic compound |
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| CN106480346A (en) * | 2016-11-18 | 2017-03-08 | 扶绥县科学技术情报研究所 | The preparation method of magnesium alloy |
| CN106498250A (en) * | 2016-11-18 | 2017-03-15 | 扶绥县科学技术情报研究所 | The processing method of magnesium alloy |
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| CN113134595A (en) * | 2021-04-08 | 2021-07-20 | 西北工业大学 | Smelting furnace and smelting method for making chemical components and microstructure of magnesium alloy uniform |
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