US20160273075A1

US20160273075A1 - Aluminium alloy refiner and preparation method and application thereof

Info

Publication number: US20160273075A1
Application number: US15/070,777
Authority: US
Inventors: Yongning Wang; Zhihua Zhu; Chunhai LIU; Changhai Li; Lateng A; Lisheng Wang; Zhendong ZHANG; Bangwei BAI; Zheng Fang; Weimin Zhao
Original assignee: Hebei University of Technology; Citic Dicastal Co Ltd
Current assignee: Hebei University of Technology; Citic Dicastal Co Ltd
Priority date: 2015-03-19
Filing date: 2016-03-15
Publication date: 2016-09-22
Also published as: CN105671350A

Abstract

The present invention provides an aluminium alloy refiner. The aluminium alloy refiner is characterized by comprising 7 to 10 parts of Ti, 2 to 3 parts of B and the balance of Al by weight, for example, 8 parts of Ti, 3 parts of B and 89 parts of Al by weight. The aluminium alloy refiner is prepared by rapid solidification. After the refiner is added to A356.2 aluminium alloy, the grain size of the alloy is significantly reduced than that of the aluminium alloy treated by a conventional refiner. Moreover, the solubility of metals in liquid may be increased due to rapid solidification, such that the refiner is more easily absorbed by the aluminium alloy melt after being added to the aluminium alloy.

Description

FIELD OF THE INVENTION

The present invention relates to the field of aluminium alloy smelting, and particularly relates to an aluminium alloy refiner and a preparation method and application thereof.

BACKGROUND OF THE INVENTION

A356.2 aluminium alloy has excellent characteristics such as good fluidity, no thermal cracking tendency, low linear shrinkage, small specific gravity and good corrosion resistance, and is a main material used in automobile hubs. However, the as-cast structure of the A356.2 aluminium alloy which is not subjected to refinement and modification treatment is a thickly platy or needle-shaped eutectic silicon and alpha-Al dendritic structure with relatively low mechanical properties. Therefore, it is necessary to add modification elements and grain refining elements, such that morphologies of eutectoid silicon are transformed from thickly flaky shapes or needle shapes into finely spherical shapes or rod shapes, and simultaneously, alpha-Al grains are refined, thereby the usability of the A356.2 alloy can be improved, and the application range of the A356.2 aluminum alloy is expanded. At present, refiners commonly used for the A356.2 aluminium alloy in the industrial production are Al—Ti—B, Al—Ti—C, Al—Ti—B—C, etc.
In the prior art, CN102886511A discloses a method of preparing an Al—Ti—C grain refiner. The refiner is prepared by adding TiC to aluminium melt. As the related TiC is nanoparticles, the material cost is high, and a preparation process is complicated. It is necessary to use argon or nitrogen for dispersing the nanopowder to the melt, which increases the complexity of the process, prolongs the cycle of the whole process and does not facilitate industrial production.
In the prior art, CN103667759A discloses an Al—Mg—Si series alloy alpha-Al grain refiner and a preparation method thereof. According to the method, Ti powder, Bi powder and Cr powder need to be mixed, and then the obtained mixture is ground into 200-400 mesh powder, which prolongs the process duration. The powder may be used only after the powder is tightly packaged by using aluminum foil and baked for 30 minutes at the temperature of 200-250 degrees Celsius, which increases the complexity of the process and does not facilitate industrial production.
In the prior art, CN103589916A discloses an Al—Ti—B—Sc intermediate alloy refiner obtained by rapid solidification and a preparation method thereof. Intermediate alloy related in the method comprises 3.75% to 5% of Ti and 0.75% to 1% of B, and the two elements are relatively low in content and have limited refining effects. Moreover, the intermediate alloy related in method also comprises 0.1% to 0.5% of noble metal Sc element, and therefore, the manufacturing cost of the Al—Ti—B—Sc intermediate alloy refiner is high.
In summary, the aluminium alloy refiner in the prior art is less likely to be widely applied due to relatively high cost, or the application of the aluminum alloy refiner in production is limited due to complicated using steps and processes.

SUMMARY OF THE INVENTION

Therefore, the present invention aims at providing an aluminium alloy refiner which is relatively low in cost and simple in a use technology.
The following embodiments are provided in order to achieve the aim of the invention.
In one aspect of the present invention, the aluminium alloy refiner is provided and comprises 7 to 10 parts of Ti, 2 to 3 parts of B and 87 to 91 parts of Al by weight, for example, 8 parts of Ti, 3 parts of B and 89 parts of Al by weight. Preferably, the aluminium alloy refiner comprises 7.5 to 9 parts of Ti, 2.5 to 3 parts of B and 88 to 90 parts of Al by weight; further preferably, the aluminium alloy refiner comprises 8 to 8.5 parts of Ti, 2.5 to 3 parts of B and 89 to 90 parts of Al by weight; and for example, (1) the aluminium alloy refiner comprises 8 parts of Ti, 3 parts of B and 89 parts of Al by weight, (2) the aluminium alloy refiner comprises 7 parts of Ti, 2 parts of B and 91 parts of Al by weight, (3) the aluminium alloy refiner comprises 7.5 parts of Ti, 2.5 parts of B and 90 parts of Al by weight, (4) the aluminium alloy refiner comprises 8.5 parts of Ti, 2.5 parts of B and 89 parts of Al by weight, (5) the aluminium alloy refiner comprises 9 parts of Ti, 3 parts of B and 88 parts of Al by weight, and (6) the aluminium alloy refiner comprises 10 parts of Ti, 3 parts of B and 87 parts of Al by weight.
In a preferred aspect of the present invention, the aluminium alloy refiner is composed of alpha-Al phases, granulous TiAl₃phases and TiB₂particle phases.
In a preferred aspect of the present invention, the particle size of the granulous TiAl₃phases of the aluminium alloy refiner is less than 1.0 micrometer, and preferably is 0.6 to 1.0 micrometer.
In a preferred aspect of the present invention, the particle size of the TiB₂particle phases of the aluminium alloy refiner is less than 60 nm, and preferably is 30 to 60 nm.
In a preferred aspect of the present invention, the aluminium alloy refiner is prepared by rapid solidification.
In another aspect of the present invention, a method of preparing the aluminium alloy refiner mentioned above is provided and comprises the following steps:
(1) mixing raw materials in proportion, and placing them into a quartz tube with an opening at the lower end, and heating the quartz tube until test blocks in the quartz tube are completely melted, wherein preferably, the diameter of a small space of the opening at the lower end of the quartz tube is 0.3 to 0.6 mm, and most preferably is 0.4 mm;
(2) injecting melt in the quartz tube onto a rotating copper roller, wherein preferably, the copper roller rotates at a rotation speed of 50 to 65 revolutions per second, and most preferably at a rotation speed of 60 revolutions per second.
In a preferred aspect of the present invention, the raw materials are industrial Al—Ti—B intermediate alloy, elemental Ti particles and elemental B particles.
In another aspect of the present invention, a method of refining an aluminium alloy by using the aluminium alloy refiner mentioned above or the aluminium alloy refiner prepared according to the method mentioned above is provided and characterized by comprising the following steps: (1) heating and melting aluminium alloy ingot castings, then stirring at a low speed, keeping still and skimming surface dross; (2) adding the aluminium alloy refiner of any one of claims 1 to 5 or the aluminium alloy refiner prepared according to the method of one of claims 6 to 7 to the aluminium alloy melt, wherein the addition quantity of the aluminium alloy refiner accounts for 0.15% to 0.30% of the mass fraction of the aluminium alloy melt, and skimming the surface dross after the refiner is completely melted and heat preservation is carried out on the melt for 10 minutes; slowly introducing high-purity argon into the melt for refining, wherein the refining temperature is 720 degrees Celsius, stirring slowly during introduction of the gas, and removing the surface dross again after ending refining; and (3) keeping the melt with the temperature of 720 degrees Celsius still, and slowly pouring the melt into a preheated cast iron mould, wherein preferably, the aluminium alloy is the A356.2 aluminium alloy, and preferably, the addition quantity accounts for 0.20% of the mass fraction of the aluminium alloy melt.
In another aspect of the present invention, a method of refining the aluminium alloy by using the aluminium alloy refiner mentioned above or the aluminium alloy refiner prepared according to the method mentioned above is provided and characterized by comprising the following steps: (1) heating the A356.2 aluminium alloy ingot castings with a furnace to 740 degrees Celsius, stirring the melt manually at a low speed for 0.5 minute after the alloy is melted, then keeping the melt still for 1 minute and skimming the surface dross; (2) adding the Al—Ti—B refiner of the present invention obtained by rapid solidification to the aluminium alloy melt, wherein the addition quantity of the Al—Ti—B refiner accounts for 0.2% of the mass fraction of the A356.2 aluminium alloy melt; skimming the surface dross after the refiner is completely melted and heat preservation is carried out on the melt for 10 minutes; slowly introducing high-purity argon (with the purity of 99.99%) into the melt for refining, wherein the refining temperature is 720 degrees Celsius, stirring slowly for 5 minutes during introduction of the gas, and removing the surface dross again after ending the refining; and (3) keeping the melt with the temperature of 720 degrees Celsius still for 1 minute, and slowly pouring the melt into the cast iron mould with the preheating temperature of 150 degrees Celsius.
In another aspect of the present invention, the aluminium alloy which is refined according to the method mentioned above is provided.
In another aspect of the present invention, the application of the aluminium alloy obtained by treatment according to the method mentioned above or the aluminium alloy mentioned above in wheel casting is provided.
In other aspects of the present invention, the following technical solution is provided:
The Al—Ti—B refiner obtained by rapid solidification is composed of 8% of Ti, 3% of B and 89% of Al by mass and mainly comprises alpha-Al phases, granulous TiAl₃phases with the size of less than 1.0 micrometer and TiB₂particle phases with the size of less than 60 nm.
The method of preparing the Al—Ti—B refiner mentioned above by rapid solidification comprises the following steps:
Step one, preparing refiner strips by rapid solidification.
Making small industrial Al—Ti—B intermediate alloy blocks (the length, width and height of each alloy block is not more than 6 mm, and each alloy block comprises 5.0% of Ti, 1.0% of B, less than 0.15% of Fe, Cu, Mg and Mn and the balance of Al by mass and is purchased from KBM Affilips Company), Ti particles (the diameter of the Ti particles is not more than 2 mm and the purity of the Ti particles is 99.99%) and B particles (the diameter of the B particles is not more than 2 mm and the purity of the B particles is 99.99%) into an Al-8Ti-3B component, mixing the above materials and placing them into the quartz tube provided with a small opening having the diameter of 0.4 mm at the lower end; heating an induction coil of a WK-IIB vacuum strip-spun machine until the test blocks in the quartz tube are completely melted, and injecting the molten intermediate alloy onto the copper roller with a rotation speed of 60 revolutions per second, thus obtaining the Al-8Ti-3B refiner strips with the thickness of 8 micrometers and the width of 1.2 mm by rapid solidification.
Step two, pressing the strips into the test blocks.
A briquetting machine is used for pressing the strips at the pressure of 500 MPa for 5 minutes so as to form the cylindrical test blocks with the size of phi 20 mm*10 mm for the convenience of subsequent use.
Compared with the prior art, the present invention has the following remarkable advantages:
(1) the method and equipment for preparation are simple, the alloy smelting and the strip-spun process are smoothly completed, the operation process is simple, the productivity is high, and the disadvantages such as complicated smelting and preparation processes, long process time, limited refining effect and high cost of the raw materials are overcome;
(2) the content of Ti and B in the Al—Ti—B alloy prepared by the present invention is higher than that of Ti and B in conventional alloy, the distribution of Ti and B in the Al—Ti—B alloy is more uniform than that of Ti and B in the conventional alloy, the size of Ti and B in the Al—Ti—B alloy is smaller than that of Ti and B in the conventional alloy, and therefore, the quantity of nucleation particles is greatly increased, and the refining effect on the aluminium alloy is relatively good.
(3) The present invention does not contain precious metal elements, thus saving the cost of raw materials.
(4) The aluminium alloy refiner in the present invention is prepared by a rapid solidification method. Precipitated phase particles are smaller and more evenly dispersed due to rapid solidification. After the refiner is added to the A356.2 aluminium alloy, the grain size of the alloy is significantly reduced than that of the aluminium alloy treated by the conventional refiner. Moreover, the solubility of metals in liquid may be increased due to rapid solidification, such that the refiner is more easily absorbed by the aluminium alloy melt after being added to the aluminium alloy.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments of the present invention are described in details below with reference to the drawings, wherein,

FIG. 1 is a metallographic structure photograph of the as-cast Al—Ti—B refiner;

FIG. 2 is a scanning electron microscope photograph of the Al—Ti—B refiner strips prepared by rapid solidification;

FIG. 3 is a transmission electron microscope photograph of the Al—Ti—B refiner strips prepared by rapid solidification;

FIG. 4 is a metallographic microstructure photograph of the A356.2 alloy which is subjected to thermal treatment;

FIG. 5 is a metallographic structure photograph of the A356.2 alloy which is treated by a conventional Al—Ti—B refiner and then subjected to thermal treatment;

FIG. 6 is a metallurgical structure photograph of the A356.2 alloy in embodiment 1 which is treated by Al—Ti—B refiner strips prepared by rapid solidification and then subjected to thermal treatment.

DETAILED DESCRIPTION OF THE INVENTION

Step one, preparing the refiner strips by rapid solidification.
Making small industrial Al—Ti—B intermediate alloy blocks (the length, width and height of each alloy block are not more than 6 mm, and each alloy block comprises 5.0% of Ti, 1.0% of B, less than 0.15% of Fe, Cu, Mg, Mn and the balance of Al by mass and is purchased from KBM Affilips Company), Ti particles (the diameter of the Ti particles is not more than 2 mm and the purity of the Ti particles is 99.99%) and B particles (the diameter of the B particles is not more than 2 mm and the purity of the B particles is 99.99%) into the A1-8Ti-3B component, mixing the above materials (ensuring that the parts by weight of Ti, B and Al elements are as shown in the tablet) and placing them into the quartz tube provided with a small opening having the diameter of 0.4 mm at the lower end; heating the induction coil of the WK-IIB vacuum strip-spun machine until the test blocks in the quartz tube are completely melted, and injecting the molten intermediate alloy onto the copper roller with a rotation speed of 60 revolutions per second, thus obtaining the A1-8Ti-3B refiner strips with the thickness of 8 micrometers and the width of 1.2 mm by rapid solidification.

Table 1

Parts by weight of Ti, B and Al elements

group	parts by weight of	parts by weight of	parts by weight of
number	Ti element	B element	Al element

1	8	3	89
2	7	2	91
3	7.5	2.5	90
4	8.5	2.5	89
5	9	3	88
6	10	3	87

Step two, pressing the strips into test blocks.
A briquetting machine is used for pressing the strips at the pressure of 500 MPa for 5 minutes so as to form the cylindrical test blocks with the size of phi 20 mm*10 mm for the convenience of subsequent use.
FIG. 1 is a metallographic structure photograph of the as-cast A1-5Ti-1B refiner, as seen from the figure, the as-cast A1-5Ti-1B refiner comprises alpha-Al phases, blocky TiAl₃phases with the size of less than 40 micrometers and TiB₂phases with the dispersed distribution size of less than 9 micrometers.
The first group of microstructures of the A1-8Ti-3B refiner strips prepared by rapid solidification in the embodiment is as shown in FIG. 2 and FIG. 3, and the morphologies and sizes of the formed TiAl₃phases and TiB₂phases are respectively shown. As seen from the figures, the A1-8Ti-3B refiner strips prepared by rapid solidification are composed of the alpha-Al phases, the granulous TiAl₃phases with the size of less than 1.0 micrometer and the granulous TiB₂phases with the size of less than 60 nm, and it can be seen that the particles precipitated out from the alloy are more evenly dispersed after rapid solidification treatment, the size of the precipitated phases is greatly reduced, and the nucleation particles are greatly improved. Samples of the group 2 to the group 6 are also subjected to microstructure observation, and observation results also show that the A1-8Ti-3B refiner strips prepared by rapid solidification are composed of the alpha-Al phases, the granulous TiAl₃phases with the size of less than 1.0 micrometer and the TiB₂phases with the size of less than 60 nm (not shown in experimental results).
FIG. 4 is the metallographic microstructure of the A356.2 aluminium alloy (the A356.2 aluminium alloy comprises 6.83% of Si, 0.34% of Mg, 0.07% of Fe, 0.11% of Ti, 0.024% of Sr, 0.0008% of B and the balance of Al and is purchased from Binzhou Mengwei Lianxin New Material Co., Ltd.) which is subjected to thermal treatment; the thermal treatment process is 540 degrees Celsius*2 h+150 degrees Celsius*12 h. As seen from FIG. 4, the alpha-Al grains are relatively thick after the A356.2 aluminium alloy is subjected to thermal treatment, and the average size of the alpha-Al grains is 136.5 micrometers.
FIG. 5 is the metallographic microstructure of the alloy obtained after a conventional as-cast A1-5Ti-1B refiner with 0.1% of Ti by mass (by the addition quantity of Ti) to the A356.2 aluminium alloy and the thermal treatment is carried out, and the thermal treatment process is 540 degrees Celsius*2 h+150 degrees Celsius*12 h; and as seen from FIG. 5, after such treatment, the alpha-Al grains are refined, the average size of the alpha-Al grains is 98.4 micrometers.
FIG. 6 is the metallographic microstructure of the alloy obtained after the A1-8Ti-3B refiner cylindrical strip test blocks in the first group of the embodiment which comprise 0.1% of Ti by mass (by the addition quantity of Ti) are added to the A356.2 aluminium alloy and the thermal treatment is carried out, and the thermal treatment process is 540 degrees Celsius*2 h+150 degrees Celsius*12 h. As seen from FIG. 6, after such treatment, the alpha-Al grains are further refined, the average size of the alpha-Al grains is 56.8 micrometers, and the refining effect of the A1-8Ti-3B refiner cylindrical strip test blocks is remarkably improved as compared with that of the conventional refiner. It can be seen that the refining effect achieved after the refiner cylindrical strip test blocks prepared by rapid solidification in the embodiment are added to the A356.2 alloy is better than the refining effect achieved by using the conventional as-cast refiner in the case of the same addition quantity of Ti. Samples in the group 2 to the group 6 are also subjected to the above testing, the results show that after such treatment, the alpha-Al grains are further refined, the average size of the alpha-Al grains is below 65 micrometers, and the refining effect of the A1-8Ti-3B refiner cylindrical strip test blocks is remarkably improved as compared with that of the conventional refiner.
The raw materials and equipments used in the above embodiments are obtained by commonly known approaches, and the used operation process is mastered by those skilled in the art.

Claims

1. An aluminium alloy refiner, characterized in that the aluminium alloy refiner comprises 7 to 10 parts of Ti, 2 to 3 parts of B and 87 to 91 parts of Al by weight;

preferably, the aluminium alloy refiner comprises 7.5 to 9 parts of Ti, 2.5 to 3 parts of B and 88 to 90 parts of Al by weight;

further preferably, the aluminium alloy refiner comprises 8 to 8.5 parts of Ti, 2.5 to 3 parts of B and 89 to 90 parts of Al by weight;

for example,

(1) the aluminium alloy refiner comprises 8 parts of Ti, 3 parts of B and 89 parts of Al by weight;

(2) the aluminium alloy refiner comprises 7 parts of Ti, 2 parts of B and 91 parts of Al by weight;

(3) the aluminium alloy refiner comprises 7.5 parts of Ti, 2.5 parts of B and 90 parts of Al by weight;

(4) the aluminium alloy refiner comprises 8.5 parts of Ti, 2.5 parts of B and 89 parts of Al by weight;

(5) the aluminium alloy refiner comprises 9 parts of Ti, 3 parts of B and 88 parts of Al by weight; and

(6) the aluminium alloy refiner comprises 10 parts of Ti, 3 parts of B and 87 parts of Al by weight.

2. The aluminium alloy refiner according to claim 1, characterized in that the aluminium alloy refiner is composed of alpha-Al phases, granulous TiAl₃phases and TiB₂particle phases.

3. The aluminium alloy refiner according to claim 1, characterized in that the size of the granulous TiAl₃phases of the aluminium alloy refiner is less than 1.0 micrometer, and preferably is 0.6 to 1.0 micrometer.

4. The aluminium alloy refiner according to claim 1, characterized in that the size of the TiB₂particle phases of the aluminium alloy refiner is less than 60 nm, and preferably is 30 to 60 nm.

5. The aluminium alloy refiner according to claim 1, characterized in that the aluminium alloy refiner is prepared by rapid solidification.

6. The method of preparing the aluminium alloy refiner according to claim 1, characterized in that the method comprises the following steps:

(1) mixing raw materials in proportion, and placing them into a quartz tube with an opening at the lower end, and heating the quartz tube until test blocks in the quartz tube are completely melted, preferably, the diameter of a small space of the opening at the lower end of the quartz tube being 0.3 to 0.6 mm, and most preferably is 0.4 mm;

(2) injecting melt in the quartz tube onto a rotating copper roller, preferably the copper roller rotating at a rotation speed of 50 to 65 revolutions per second, and most preferably at a rotation speed of 60 revolutions per second.

7. The method according to claim 6, characterized in that the raw materials are industrial Al—Ti—B intermediate alloy, elemental Ti particles and elemental B particles.

8. The method of refining the aluminium alloy by using the aluminium alloy refiner of claim 1, characterized by comprising the following steps:

(1) heating and melting aluminium alloy ingot castings, then stirring at a low speed, keeping still and skimming surface dross;

(2) adding the aluminium alloy refiner of any one of claims 1 to 5 or the aluminium alloy refiner prepared according to the method of any one of claims 6 to 7 to aluminium alloy melt, wherein the addition quantity of the aluminium alloy refiner accounts for 0.15% to 0.30% of the mass fraction of the aluminium alloy melt, and skimming the surface dross after the refiner is completely melted and heat preservation is carried out on the melt for 10 minutes; slowly introducing high-purity argon into the melt for refining, wherein the refining temperature is 720 degrees Celsius, stirring slowly during introduction of the gas, and removing the surface dross again after ending refining;

(3) keeping the melt with the temperature of 720 degrees Celsius still, and then slowly pouring the melt into a preheated cast iron mould;

preferably, the aluminium alloy is A356.2 aluminium alloy;

preferably, the addition quantity accounts for 0.20% of the mass fraction of the aluminium alloy melt.

9. The aluminium alloy refined according to the method of claim 8.

10. The application of the aluminium alloy obtained by treatment according to the method of claim 8 in aluminium wheel casting.