CN110195181B - Die-casting magnesium alloy with high-temperature heat resistance and manufacturing method thereof - Google Patents
Die-casting magnesium alloy with high-temperature heat resistance and manufacturing method thereof Download PDFInfo
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- CN110195181B CN110195181B CN201810158747.8A CN201810158747A CN110195181B CN 110195181 B CN110195181 B CN 110195181B CN 201810158747 A CN201810158747 A CN 201810158747A CN 110195181 B CN110195181 B CN 110195181B
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- 229910000861 Mg alloy Inorganic materials 0.000 title claims abstract description 133
- 238000004512 die casting Methods 0.000 title claims abstract description 60
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 24
- 239000011777 magnesium Substances 0.000 claims abstract description 30
- 239000012535 impurity Substances 0.000 claims abstract description 9
- 229910052729 chemical element Inorganic materials 0.000 claims abstract description 6
- 229910045601 alloy Inorganic materials 0.000 claims description 60
- 239000000956 alloy Substances 0.000 claims description 60
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 claims description 25
- 229910052749 magnesium Inorganic materials 0.000 claims description 25
- 238000001816 cooling Methods 0.000 claims description 12
- 238000002844 melting Methods 0.000 claims description 12
- 230000008018 melting Effects 0.000 claims description 11
- 238000005266 casting Methods 0.000 claims description 9
- 238000010438 heat treatment Methods 0.000 claims description 9
- 229910052782 aluminium Inorganic materials 0.000 claims description 7
- 238000000034 method Methods 0.000 claims description 7
- 239000003795 chemical substances by application Substances 0.000 claims description 5
- 239000007789 gas Substances 0.000 claims description 5
- 238000003756 stirring Methods 0.000 claims description 5
- 238000002156 mixing Methods 0.000 claims description 4
- 229910052688 Gadolinium Inorganic materials 0.000 claims description 3
- 238000002347 injection Methods 0.000 claims description 3
- 239000007924 injection Substances 0.000 claims description 3
- 239000011159 matrix material Substances 0.000 claims description 3
- 238000005507 spraying Methods 0.000 claims description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 3
- 229910052727 yttrium Inorganic materials 0.000 claims description 3
- 229910018131 Al-Mn Inorganic materials 0.000 claims description 2
- 229910018461 Al—Mn Inorganic materials 0.000 claims description 2
- 229910052746 lanthanum Inorganic materials 0.000 claims description 2
- 239000000463 material Substances 0.000 claims description 2
- 239000002893 slag Substances 0.000 claims description 2
- 239000007921 spray Substances 0.000 claims description 2
- 229910052761 rare earth metal Inorganic materials 0.000 description 24
- 230000000694 effects Effects 0.000 description 11
- 230000000052 comparative effect Effects 0.000 description 10
- 229910052791 calcium Inorganic materials 0.000 description 7
- 238000005275 alloying Methods 0.000 description 5
- 150000002910 rare earth metals Chemical class 0.000 description 5
- 229910052712 strontium Inorganic materials 0.000 description 5
- 229910052784 alkaline earth metal Inorganic materials 0.000 description 4
- 150000001342 alkaline earth metals Chemical class 0.000 description 4
- 238000013461 design Methods 0.000 description 4
- 239000006104 solid solution Substances 0.000 description 4
- 238000005728 strengthening Methods 0.000 description 4
- 238000011161 development Methods 0.000 description 3
- 230000018109 developmental process Effects 0.000 description 3
- 238000007670 refining Methods 0.000 description 3
- RNFJDJUURJAICM-UHFFFAOYSA-N 2,2,4,4,6,6-hexaphenoxy-1,3,5-triaza-2$l^{5},4$l^{5},6$l^{5}-triphosphacyclohexa-1,3,5-triene Chemical compound N=1P(OC=2C=CC=CC=2)(OC=2C=CC=CC=2)=NP(OC=2C=CC=CC=2)(OC=2C=CC=CC=2)=NP=1(OC=1C=CC=CC=1)OC1=CC=CC=C1 RNFJDJUURJAICM-UHFFFAOYSA-N 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 238000005336 cracking Methods 0.000 description 2
- 239000003063 flame retardant Substances 0.000 description 2
- 239000002086 nanomaterial Substances 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 239000002244 precipitate Substances 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 239000002356 single layer Substances 0.000 description 2
- 229910000838 Al alloy Inorganic materials 0.000 description 1
- 229910052684 Cerium Inorganic materials 0.000 description 1
- 229910002551 Fe-Mn Inorganic materials 0.000 description 1
- 229910003023 Mg-Al Inorganic materials 0.000 description 1
- 229910001122 Mischmetal Inorganic materials 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- SNAAJJQQZSMGQD-UHFFFAOYSA-N aluminum magnesium Chemical compound [Mg].[Al] SNAAJJQQZSMGQD-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 230000008094 contradictory effect Effects 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 229910001325 element alloy Inorganic materials 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
- UIWYJDYFSGRHKR-UHFFFAOYSA-N gadolinium atom Chemical compound [Gd] UIWYJDYFSGRHKR-UHFFFAOYSA-N 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 239000000155 melt Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 230000002093 peripheral effect Effects 0.000 description 1
- 230000001376 precipitating effect Effects 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 238000001953 recrystallisation Methods 0.000 description 1
- 238000007711 solidification Methods 0.000 description 1
- 230000008023 solidification Effects 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- VWQVUPCCIRVNHF-UHFFFAOYSA-N yttrium atom Chemical compound [Y] VWQVUPCCIRVNHF-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D17/00—Pressure die casting or injection die casting, i.e. casting in which the metal is forced into a mould under high pressure
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C1/00—Making non-ferrous alloys
- C22C1/02—Making non-ferrous alloys by melting
- C22C1/03—Making non-ferrous alloys by melting using master alloys
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C23/00—Alloys based on magnesium
- C22C23/02—Alloys based on magnesium with aluminium as the next major constituent
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Molds, Cores, And Manufacturing Methods Thereof (AREA)
- Forging (AREA)
Abstract
The invention discloses a die-casting magnesium alloy with high-temperature heat resistance, which comprises the following chemical elements in percentage by mass: 1-4 wt% of Ca, 5-9 wt% of Al, 0.5-3 wt% of RE, 2-5 wt% of Sr, 0.1-0.5 wt% of Mn, and the balance of Mg and other inevitable impurities. In addition, the invention also discloses a manufacturing method of the die-casting magnesium alloy with high-temperature heat resistance. The die-casting magnesium alloy has high-temperature heat resistance, high strength and good heat conductivity, and well solves the problems of insufficient heat conductivity, low strength, low heat resistance and poor die-casting castability of the existing magnesium alloy.
Description
Technical Field
The invention relates to an alloy and a manufacturing method thereof, in particular to a magnesium alloy and a manufacturing method thereof.
Background
The Mg-Al-RE magnesium alloy has excellent casting performance and mechanical performance, and high melting point Al generated by combining RE and Al11RE3The phase is beneficial to improving the room-temperature and high-temperature mechanical properties of the alloy, so that the alloy has good room-temperature toughness and high-temperature heat resistance. On the other hand, generatedAl11RE3The aluminum content in the alloy can be obviously reduced, and the thermal conductivity of the alloy is improved. Therefore, the AE magnesium alloy is a potential high thermal conductivity cast magnesium alloy. However, the thermal conductivity of the currently developed Mg-Al-RE casting alloy is lower than 100W/m.K, and the room temperature strength is also to be improved. Therefore, the development of a novel high-heat-conductivity high-strength cast magnesium alloy with good casting performance has great significance for meeting the requirements of electronic products on light high-heat-conductivity radiators. At present, rare earth added into Mg-Al-RE magnesium alloy is mainly cerium-rich light mixed rare earth.
The addition of alkaline earth elements to the Mg-Al-based alloy can precipitate Al-Ca or Al-Sr phases with very high melting points in the matrix. The high-melting-point phases are stable at high temperature, have good pinning effect on crystal boundaries, and can effectively improve the high-temperature mechanical property, particularly the creep resistance, of the magnesium alloy. Therefore, the development of the heat-resistant magnesium alloy containing alkaline earth elements such as Sr and Ca at low cost has great significance for popularizing the application of the magnesium alloy in heat-resistant parts around automobile engines. Based on the limitation of AZ, AS and other heat-resistant magnesium alloys applied to automobile power systems, the Canadian Nonida company develops AJ (Mg-Al-Sr) series of heat-resistant magnesium alloys, such AS AJ50x, AJ51x, AJ52x, AJ62x, AJ62Lx and other brands of alloys, wherein AJ62x is successfully used for producing thin-wall magnesium alloy parts such AS oil pans, valve covers and the like. The maximum working temperature of the AJ62x heat-resistant magnesium alloy can reach 175 ℃, and the room-temperature tensile strength and creep property of the heat-resistant magnesium alloy are obviously superior to those of AZ91 die-casting magnesium alloy. In recent years, peripheral parts of automobile engines have made higher demands on the heat resistance of heat-resistant magnesium alloys, and high-strength heat-resistant die-cast magnesium alloys having a heat resistance temperature of 200 ℃ have been developed.
While pure magnesium has a relatively high thermal conductivity of about 157W/m.K, but the strength is too low and the as-cast tensile yield strength is about 21 MPa. The mechanical properties of magnesium can be improved significantly by the addition of alloying elements, but the thermal conductivity is usually significantly reduced by the addition of alloying elements. Therefore, in recent years, some high-thermal-conductivity, high-strength and heat-resistant magnesium alloys have been developed in China, but these alloys are basically wrought alloys and are not suitable for die casting.
For example: the patent document is a Chinese patent document with the publication number of CN1804083 and the publication date of 2006, 7 and 19 and the name of 'high-strength heat-resistant rare earth magnesium alloy', and the technical scheme disclosed by the patent document relates to a high-strength heat-resistant rare earth magnesium alloy, but the high-strength heat-resistant rare earth magnesium alloy is not suitable for being used as die-casting magnesium alloy. In addition, the alloy contains: 2-10 mass% of gadolinium element and 3-12 mass% of yttrium element, wherein the total mass of the two elements is 13-14 mass%, and the balance is magnesium and inevitable impurities, namely the alloy is expensive in component and large in specific gravity, so that the thermal conductivity of the alloy is low.
Another example is: the technical scheme is that the alloy is characterized in that 0.3-1.0 mass percent of Ca, 0.2-0.8 mass percent of RE and 0.05-0.15 mass percent of Sr are added on the basis of AZ 91D; wherein RE is general La-rich mischmetal. The mechanical properties of the alloy at room temperature, 150 ℃ and 200 ℃ are obviously improved; but the strength level is not high enough, especially the high-temperature performance (the alloy strength at 150 ℃ is less than 185MPa), and the heat conducting performance is low, so that the practical application requirements under the working environment of a gear box and the like cannot be met.
Based on the above, it can be seen that at present, few reports on the component design of the high-thermal-conductivity high-strength heat-resistant die-casting magnesium alloy are reported at home and abroad, the research on the influence rule and mechanism of alloy elements on the thermal conductivity and the thermal resistance of the magnesium alloy is lacked, the novel high-thermal-conductivity high-strength heat-resistant magnesium alloy and the related preparation technology thereof are late in development, and the urgent requirements of the user market on the high-thermal-conductivity high-strength heat-resistant die-casting magnesium alloy cannot be met, so that the magnesium alloy with the high-temperature heat resistance is expected to be obtained, and the problems of insufficient thermal conductivity, low strength, low heat resistance and poor die-casting performance of the existing magnesium alloy are well solved.
Disclosure of Invention
One of the purposes of the invention is to provide a die-casting magnesium alloy with high-temperature heat resistance, which has high-temperature heat resistance, high strength and good heat conductivity, and well solves the problems of insufficient heat conductivity, low strength, low heat resistance and poor die-casting performance of the existing magnesium alloy.
In order to achieve the purpose, the invention provides a die-casting magnesium alloy with high-temperature heat resistance, which comprises the following chemical elements in percentage by mass:
Ca 1～4wt％，
Al 5～9wt％，
RE 0.5～3wt％，
Sr 2～5wt％，
Mn 0.1～0.5wt％，
the balance being Mg and other unavoidable impurities.
For the technical scheme of the invention, the inventor obtains a die-casting magnesium alloy with high-temperature heat resistance through reasonable optimization of alloy elements, and according to the influence of the addition of the alloy elements of the die-casting alloy on the final performance of the alloy and the requirement of high-heat-conductivity alloying of the magnesium alloy, the inventor researches the influence rule of the effects of various alloy elements in magnesium and various factors on the die-casting formability of the alloy through a large number of experiments, and finds that when alkaline earth metals (such as Sr and Ca) and rare earth elements are added into the magnesium alloy, the die-casting magnesium alloy has excellent room-temperature strength and high-temperature creep resistance, good die-casting performance and higher heat conductivity. In addition, because the die-casting magnesium alloy is added with alkaline earth metal and rare earth elements, a plurality of second phases with high melting point and small size are generated, thereby improving the strength and heat resistance of the die-casting magnesium alloy and further improving the die-casting performance of the die-casting magnesium alloy.
In addition, aiming at the characteristics of the die-casting alloy, the die-casting alloy generally has lower melting point, the melt of the die-casting alloy has good fluidity, the crystallization temperature range is small, the tendency of quick cooling and hot cracking is small, so that the requirements of extremely high filling speed and high cooling speed in die-casting and the die-casting of a thin-wall casting with a complex shape can be met, and a complex die cavity can be filled.
Based on the above, the inventor proposes a die-casting alloy with high-temperature heat resistance, which comprises the following chemical elements in percentage by mass: 1-4 wt% of Ca, 5-9 wt% of Al, 0.5-3 wt% of RE, 2-5 wt% of Sr, 0.1-0.5 wt% of Mn and the balance of Mg and other inevitable impurities, and the design principle of each chemical element in the die-cast magnesium alloy is as follows:
ca: one of the alkaline earth elements, in cooperation with Sr, can produce grain refining effect in magnesium, can inhibit oxidation of molten magnesium, has flame retardant effect, can increase ignition temperature of alloy melt, and can improve creep property of alloy. The element can form a second phase with other elements in magnesium, particularly can obtain an ordered monolayer nanostructure with high strengthening effect, and has obvious effect on improving the mechanical property of the magnesium alloy. In order to control the amount and type of the second phase to maintain good thermal conductivity, the mass percentage of Ca in the die-cast magnesium alloy with high-temperature heat resistance is controlled to be 1-4 wt%.
Al: al is the most commonly used alloying element of magnesium alloy, has smaller density, and Al can form a limited solid solution with magnesium, and can improve the casting performance while improving the alloy strength and hardness of the die-casting magnesium alloy. In addition, Al can also produce aging strengthening through heat treatment, and Al can widen a solidification zone, improve the casting performance, particularly improve the flow performance of the die-casting magnesium alloy and optimize the die-casting performance. According to the findings of the inventor, the thermal conductivity of the magnesium-aluminum alloy is reduced along with the increase of the number of solid solution atoms, so that the content of the aluminum element needs to be controlled to maintain good thermal conductivity so as to avoid that the Al element seriously reduces the thermal conductivity of the magnesium alloy. In order to obtain a magnesium alloy with high thermal conductivity, it is not possible to add too much Al as an alloying element, and when the mass percentage of Al is increased to 9%, the thermal conductivity of the obtained pressed magnesium alloy is reduced to one third of that of pure magnesium. Therefore, in the die-cast magnesium alloy with high-temperature heat resistance, the mass percent of Al is controlled to be 5-9 wt%.
RE: the rare earth element (RE) is an important alloy element and has the effects of purifying an alloy solution, refining an alloy structure, improving the mechanical properties of the alloy at room temperature and high temperature and the like. However, rare earth elements are expensive, and the amount of rare earth elements added cannot be too large to control the alloy cost. The rare earth element has poor atomic diffusion capability, can improve the recrystallization temperature of the magnesium alloy and can precipitate a stable second phase, thereby greatly improving the high-temperature strength and the heat resistance of the magnesium alloy. In order to further optimize the alloy performance, 0.5-3 wt% of rare earth elements are further added on the basis that the die-casting magnesium alloy is Mg-Al-Sr-Ca-Mn multi-element alloy, so that the fluidity of the alloy is improved, the hot cracking tendency of the alloy is reduced, and meanwhile, a proper amount of nanoscale strengthening phases are generated in the alloy, so that the die-casting magnesium alloy with high-temperature heat resistance has good die-casting performance and excellent mechanical properties of high heat conductivity and high toughness, particularly high-temperature mechanical properties.
Sr: one of the alkaline earth elements, in cooperation with Ca, can produce grain refining effect in magnesium, can also inhibit the oxidation of molten magnesium, has flame retardant effect, can increase the ignition temperature of alloy melt, and can improve the creep property of the alloy. The element can form a second phase with other elements in magnesium, particularly can obtain an ordered monolayer nanostructure with high strengthening effect, and has obvious effect on improving the mechanical property of the magnesium alloy. In order to control the amount and type of the second phase to keep better heat conductivity, the mass percent of Sr of the die-cast magnesium alloy with high-temperature heat resistance is controlled to be 2-5 wt%.
Mn: for the die-casting magnesium alloy, because Fe element impurities exist in the process of adding alloy elements, and the Fe element impurities are the main reason for poor corrosion resistance of the magnesium alloy, the content of the Fe impurities is controlled by precipitating Fe-Mn compounds by adding Mn elements, so that the corrosion resistance of the magnesium alloy is improved; meanwhile, Mn element can increase heat resistance in magnesium, refine grain structure of magnesium alloy and strengthen alloy. After the Mn element with the mass percentage of 0.1-0.5% is added into the die-cast magnesium alloy with the high-temperature heat resistance, the creep resistance of the die-cast magnesium alloy is obviously increased, and the heat resistance is improved.
Further, in the die-cast magnesium alloy having high-temperature heat resistance according to the present invention, the microstructure thereof includes a magnesium matrix and precipitated second phases including an Al-Ca phase, an Al-Sr phase, an Al-RE phase, and an Al-Mn phase.
In the technical scheme of the invention, the heat conductivity of the magnesium alloy is closely related to the number and the type of solid solution atoms and second phases in the magnesium alloy, so that in order to obtain the die-cast magnesium alloy with high-temperature heat resistance and improve the heat conductivity of the die-cast magnesium alloy, the number of the solid solution atoms in the magnesium alloy is properly controlled, and meanwhile, the size and the number of precipitated phases cannot be too large and too large.
In this case, the Al — Ca phase, the Al — Sr phase, the Al — RE phase, and the Al — Mn phase are represented by the elements included in the second phase, but the representation does not mean that the atomic ratio of the elements included in the second phase is 1:1, and specifically, the Al — Ca phase is exemplified as the Al — Ca phase, and the Al — Ca phase represents that the second phase includes Al and Ca elements, but does not mean that the atoms of Al and Ca are necessarily 1: 1.
Further, in the die-cast magnesium alloy having high-temperature heat resistance according to the present invention, the Al — Ca phase includes at least Al2Ca。
Further, in the die-cast magnesium alloy having high-temperature heat resistance according to the present invention, the RE element includes at least one of La, Gd, and Y.
Further, in the die-cast magnesium alloy with high-temperature heat resistance, the content of the Al element is 6-9 wt%.
Furthermore, in the die-casting magnesium alloy with high-temperature heat resistance, Sr and Ca are more than or equal to 4wt percent.
Furthermore, in the die-casting magnesium alloy with high-temperature heat resistance, the content of RE element is 0.9-3 wt%.
Further, in the die-cast magnesium alloy with high-temperature heat resistance of the invention, the creep rate at 200 ℃ and 70MPa is less than or equal to 9.1 multiplied by 10-9s-1。
Further, in the die-cast magnesium alloy having high-temperature heat resistance according to the present invention, the thermal conductivity thereof at room temperature is more than 85W/m · K.
Furthermore, in the die-cast magnesium alloy with high-temperature heat resistance, the yield strength at room temperature is more than or equal to 158MPa, the tensile strength is more than or equal to 248MPa, and the elongation is more than or equal to 4.5%.
Furthermore, in the die-cast magnesium alloy with high-temperature heat resistance, the yield strength at 150 ℃ is more than or equal to 138MPa, the tensile strength is more than or equal to 200MPa, and the elongation is more than or equal to 10%.
Furthermore, in the die-cast magnesium alloy with high-temperature heat resistance, the yield strength at 200 ℃ is more than or equal to 130MPa, the tensile strength is more than or equal to 188MPa, and the elongation is more than or equal to 13%.
Accordingly, another object of the present invention is to provide a method for manufacturing a die-cast magnesium alloy having high-temperature heat resistance, which can obtain a die-cast magnesium alloy having high strength and good thermal conductivity.
In order to achieve the above object, the present invention provides a method for manufacturing the die-cast magnesium alloy having high-temperature heat resistance, including the steps of:
(1) placing the crucible into a heating furnace for preheating, and then spraying a release agent on the inner wall of the crucible;
(2) putting a pure magnesium ingot into a crucible and introducing SF6And CO2Heating the mixed gas to completely melt pure magnesium, preserving heat for a period of time, then cooling to 750 +/-5 ℃, and adding pure Al, Mg-Mn intermediate alloy, Mg-RE intermediate alloy, Mg-Ca intermediate alloy and Mg-Sr intermediate alloy;
(3) after the materials are completely melted, reducing the temperature to 730 +/-5 ℃, stirring, removing slag and standing;
(4) cooling the crucible, and taking out a magnesium alloy ingot;
(5) and melting the magnesium alloy ingot in a melting furnace of a die casting machine, preserving heat, and then injecting the molten magnesium alloy into a die casting die to obtain the high-strength high-heat-conductivity heat-resistant die casting magnesium alloy.
In the manufacturing method of the present invention, in order to obtain a die-cast magnesium alloy having high-temperature heat resistance, it is important to set process conditions, especially temperature conditions, in addition to reasonable design of alloy elements, and the inventors of the present invention found through experimental studies that desired properties of the die-cast magnesium alloy can be obtained under the above temperature conditions.
Further, in the manufacturing method of the present invention, in the step (1), the crucible is preheated to 300 ℃ ± 5 ℃, and then the release agent is sprayed on the inner wall of the crucible.
Further, in the manufacturing method of the present invention, in the step (2), when the crucible temperature reaches 500 ℃. + -. 5 ℃, a pure magnesium ingot is put into the crucible and SF is introduced into the crucible6And CO2Mixing the gases, heating to 770 +/-5 ℃, and preserving heat for 10-20min after pure magnesium is completely melted.
Further, in the manufacturing method of the invention, in the step (3), stirring is carried out for 10-20min, and standing is carried out for 25-35min after deslagging.
Further, in the manufacturing method according to the present invention, in the step (4), the crucible is cooled by using a ring-shaped spray cooling system, and the crucible is completely immersed in water after the surface of the magnesium alloy is solidified, so that the magnesium alloy ingot is separated from the crucible.
Further, in the manufacturing method of the present invention, in the step (5), the temperature is maintained at 710 ℃ ± 5 ℃, the molten magnesium alloy is injected into the die casting mold at an injection speed of 55-65m/s, the temperature of the die casting mold is 250 ℃ ± 5 ℃, and the casting pressure is 60 ± 5 MPa.
The die-casting magnesium alloy with high-temperature heat resistance optimizes alloy components by adding alkaline earth metal and rare earth elements, realizes excellent room-temperature strength and high-temperature creep resistance, and also has good die-casting performance and higher heat conductivity.
In addition, the die-casting magnesium alloy with high-temperature heat resistance of the invention is added with alkaline earth metal and rare earth elements, so that a plurality of high-melting point and small-size second phases are generated, the strength and the heat resistance of the alloy are improved, and the die-casting performance of the alloy is further improved.
The die-casting magnesium alloy which has high mechanical property, good heat resistance, high thermal conductivity and good die-casting performance and can be obtained by the manufacturing method of the invention.
Detailed Description
The die-cast magnesium alloy having high-temperature heat resistance and the method for manufacturing the same according to the present invention will be further explained and illustrated with reference to specific examples, which, however, should not be construed to unduly limit the technical scope of the present invention.
Examples 1 to 6 and comparative example 1
Table 1 shows the mass percentages of the respective chemical elements in the die-cast magnesium alloys having high-temperature heat resistance properties of examples 1 to 6 and the comparative magnesium alloy of comparative example 1.
TABLE 1 (wt%, balance Mg and other unavoidable impurities)
The manufacturing methods of the die-cast magnesium alloys of examples 1 to 6 having high-temperature heat resistance and the comparative magnesium alloy of comparative example 1 were manufactured by the following steps:
(1) preheating the crucible in a heating furnace to 300 +/-5 ℃, and then spraying a release agent on the inner wall of the crucible;
(2) when the temperature of the crucible reaches 500 +/-5 ℃, putting a pure magnesium ingot into the crucible and introducing SF6And CO2Mixing the gases, heating to 770 +/-5 ℃, preserving the temperature for 10-20min when pure magnesium is completely melted, cooling to 750 +/-5 ℃, and adding pure Al, Mg-Mn intermediate alloy, Mg-RE intermediate alloy, Mg-Ca intermediate alloy and Mg-Sr intermediate alloy;
(3) cooling to 730 + -5 deg.C after completely melting, stirring for 10-20min, removing residue, and standing for 25-35 min;
(4) adopting an annular jet cooling system to carry out treatment on the crucible, completely immersing the crucible in water after the surface of the magnesium alloy is solidified so as to separate the magnesium alloy ingot from the crucible for cooling, and finally taking out the magnesium alloy ingot;
(5) and melting a magnesium alloy ingot in a melting furnace of a die casting machine, keeping the temperature at 710 +/-5 ℃, and then injecting the molten magnesium alloy into a die casting die at the injection speed of 55-65m/s, wherein the temperature of the die casting die is 250 +/-5 ℃, and the casting pressure is 60 +/-5 MPa, so as to obtain the high-strength high-heat-conductivity heat-resistant die casting magnesium alloy.
Table 2 lists specific process parameters of the manufacturing methods of the die-cast magnesium alloys having high-temperature heat resistance properties of examples 1 to 6 and the comparative magnesium alloy of comparative example 1.
Table 2.
The die-cast magnesium alloys of the respective examples and the comparative magnesium alloy of comparative example 1 were subjected to performance tests, and the test results are shown in table 3.
Table 3.
As can be seen from tables 1 to 3, the die-cast magnesium alloys of the examples of the present invention are manufactured by proper alloy composition design and proper manufacturing method, so the die-cast magnesium alloys of the examples have excellent mechanical properties, good heat resistance, high thermal conductivity, and a creep rate at 200 ℃ and 70MPa of 9.1 × 10 or less-9s-1The thermal conductivity at room temperature is more than 85W/m.K, the yield strength at room temperature is more than or equal to 158MPa, the tensile strength is more than or equal to 248MPa, and the elongation is more than or equal to 4.5%.
Meanwhile, the performance of the die-casting magnesium alloy of each embodiment at high temperature is far better than that of the comparative example 1, the yield strength of each embodiment at 150 ℃ is more than or equal to 138MPa, the tensile strength is more than or equal to 200MPa, the elongation is more than or equal to 10%, the yield strength at 200 ℃ is more than or equal to 130MPa, the tensile strength is more than or equal to 188MPa, and the elongation is more than or equal to 13%.
It should be noted that the prior art in the protection scope of the present invention is not limited to the examples given in the present application, and all the prior art which is not inconsistent with the technical scheme of the present invention, including but not limited to the prior patent documents, the prior publications and the like, can be included in the protection scope of the present invention.
In addition, the combination of the features in the present application is not limited to the combination described in the claims of the present application or the combination described in the embodiments, and all the features described in the present application may be freely combined or combined in any manner unless contradictory to each other.
It should also be noted that the above-mentioned embodiments are only specific embodiments of the present invention. It is apparent that the present invention is not limited to the above embodiments and similar changes or modifications can be easily made by those skilled in the art from the disclosure of the present invention and shall fall within the scope of the present invention.
Claims (14)
1. The die-cast magnesium alloy with high-temperature heat resistance is characterized by comprising the following chemical elements in percentage by mass:
Ca 1～4wt％，
Al 5～9wt％，
RE 0.5～3wt％，
Sr 2～5wt％，
Mn 0.1～0.5wt％，
the balance being Mg and other unavoidable impurities;
the microstructure of the die-cast magnesium alloy comprises a magnesium matrix and a precipitated second phase, wherein the second phase comprises an Al-Ca phase, an Al-Sr phase, an Al-RE phase and an Al-Mn phase, and the Al-Ca phase at least comprises Al2Ca; the thermal conductivity of the die-cast magnesium alloy at room temperature is more than 85W/m.K, the yield strength at room temperature is more than or equal to 158MPa, the tensile strength is more than or equal to 248MPa, and the elongation is more than or equal to 4.5%.
2. The die-cast magnesium alloy having high-temperature heat resistance according to claim 1, wherein the RE element includes at least one of La, Gd, and Y.
3. The die-cast magnesium alloy with high-temperature heat resistance according to claim 1, wherein the content of Al element is 6 to 9 wt%.
4. The die-cast magnesium alloy having high-temperature heat resistance according to claim 1, wherein Sr + Ca is not less than 4 wt%.
5. The die-cast magnesium alloy having high-temperature heat resistance according to claim 1, wherein the content of the RE element is 0.9 to 3 wt%.
6. The die-cast magnesium alloy having high-temperature heat resistance according to claim 1, wherein the creep rate at 200 ℃ and 70MPa is 9.1X 10 or less-9s-1。
7. The die-cast magnesium alloy with high-temperature heat resistance according to claim 1, wherein the yield strength at 150 ℃ is 138MPa or more, the tensile strength is 200MPa or more, and the elongation is 10% or more.
8. The die-cast magnesium alloy with high-temperature heat resistance according to claim 1, wherein the yield strength at 200 ℃ is not less than 130MPa, the tensile strength is not less than 188MPa, and the elongation is not less than 13%.
9. The method for manufacturing a die-cast magnesium alloy having high-temperature heat resistance according to any one of claims 1 to 8, comprising the steps of:
(1) placing the crucible into a heating furnace for preheating, and then spraying a release agent on the inner wall of the crucible;
(2) putting a pure magnesium ingot into a crucible and introducing SF6And CO2Mixing the gas, heating to completely melt pure magnesium, holding the temperature for a period of time, and then cooling to 7 deg.CAdding pure Al, Mg-Mn intermediate alloy, Mg-RE intermediate alloy, Mg-Ca intermediate alloy and Mg-Sr intermediate alloy at 50 +/-5 ℃;
(3) after the materials are completely melted, reducing the temperature to 730 +/-5 ℃, stirring, removing slag and standing;
(4) cooling the crucible, and taking out a magnesium alloy ingot;
(5) and melting the magnesium alloy ingot in a melting furnace of a die casting machine, preserving heat, and then injecting the molten magnesium alloy into a die casting die to obtain the high-strength high-heat-conductivity heat-resistant die casting magnesium alloy.
10. The manufacturing method according to claim 9, wherein in the step (1), the crucible is preheated to 300 ℃ ± 5 ℃, and then a release agent is sprayed on the inner wall of the crucible.
11. The manufacturing method according to claim 9, wherein in the step (2), when the crucible temperature reaches 500 ℃ ± 5 ℃, a pure magnesium ingot is put into the crucible and SF is introduced thereto6And CO2Mixing the gases, heating to 770 +/-5 ℃, and preserving heat for 10-20min after pure magnesium is completely melted.
12. The manufacturing method according to claim 9, wherein in the step (3), stirring is performed for 10 to 20min, and standing is performed for 25 to 35min after deslagging.
13. The manufacturing method according to claim 9, wherein in the step (4), the crucible is cooled by using a ring-shaped spray cooling system, and after the surface of the magnesium alloy is solidified, the crucible is completely immersed in water to separate the magnesium alloy ingot from the crucible.
14. The manufacturing method as set forth in claim 10, wherein in said step (5), the holding temperature is 710 ℃ ± 5 ℃, and the molten magnesium alloy is injected into the die casting mold at an injection speed of 55-65m/s, the temperature of the die casting mold being 250 ℃ ± 5 ℃, and the casting pressure being 60 ± 5 MPa.
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| CN113136511A (en) * | 2020-01-20 | 2021-07-20 | 宝山钢铁股份有限公司 | Magnesium alloy for hub, hub and manufacturing method of hub |
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