Composite modification method for casting aluminum-silicon alloy
Technical Field
The invention relates to the technical field of modification of cast aluminum alloy, in particular to a composite modification method of cast aluminum-silicon alloy.
Background
The Al-Si series cast aluminum alloy has the advantages of excellent casting fluidity and air tightness, small thermal expansion coefficient, good weldability, mechanical processing characteristics and the like, and is widely applied to the fields of automobiles and motorcycles, aerospace, communication, electronic and electric appliances and the like. According to statistics, the output of aluminum alloy castings in 2017 in China reaches 792 ten thousand tons, wherein the aluminum-silicon alloy castings account for about 85% -90% of the aluminum-silicon alloy castings. In automobile product castings, aluminum-silicon alloy castings account for more than 80% of the total amount of the whole automobile castings, and become one of the most important light materials for automobile light weight. With the gradual increase of the requirements of new energy automobiles and communication industries on light weight, the requirements on the toughness of cast aluminum alloy are higher and higher.
The refinement of the alloy structure is one of the effective means for strengthening and toughening the metal, wherein the modification treatment has the characteristics of low cost, simple method, obvious effect and the like, and becomes one of the most effective ways for improving the structure and the performance of the aluminum alloy. At present, Al-Ti-B, Al-Ti, Al-Ti-C, RE and the like are commonly used as refiner for refining alpha-Al, wherein Al-Ti-B is most commonly used, but is not suitable for casting aluminum alloy containing Zr and has the problems of segregation and sedimentation; sr is an eutectic silicon modifier with the best effect, which is acknowledged in the industry, but Sr has active chemical activity, is easy to burn and absorb gas, and damages the mechanical property of the alloy. In order to refine alpha-Al and eutectic silicon simultaneously, a composite modification process is generally adopted, but the problems of Sr gettering and burning loss cannot be solved by simply adding Sr and Al-Ti-B in a combined manner. RE is a surface active element, can inhibit the growth of crystal grains in the aluminum alloy, and can generate a compound with [ H ], thereby having the functions of degassing and purifying a melt. Zhang Jia hong (Zhang Jia hong, Shichen Shuming. Al-Si alloy metamorphic elements and their interaction [ J ] material guide, 2018,32(11): 1870-; influence of rare earth on Al-Ti-B-RE intermediate alloy refining performance [ J ] casting technology, 2005(09): 774-. Therefore, RE can improve the modification and refinement capability of Sr and Al-Ti-B to a certain degree, but cannot realize the synchronous refinement of eutectic silicon and alpha-Al grains, so that the toughness of the alloy is improved to a greater degree.
Disclosure of Invention
The invention aims to provide a composite modifier for composite modification of hypoeutectic or eutectic aluminum-silicon alloy, and the composite modifier can achieve the purpose of simultaneously refining alpha-Al crystal grains and modifying eutectic silicon, thereby improving the tensile strength and the elongation of the alloy.
The invention also aims to provide a composite modification method for casting aluminum-silicon alloy, which mainly utilizes the composite modifier to perform composite modification. Therefore, the method has low cost and easy operation, can achieve the aim of simultaneously refining alpha-Al crystal grains and modifying eutectic silicon through composite modification, and reduces the addition amount of Sr and Al-Ti-B, thereby improving the tensile strength and the elongation of the alloy and simultaneously improving the toughness of the cast aluminum alloy.
The technical problem to be solved by the invention is realized by adopting the following technical scheme.
The invention provides a composite modifier for composite modification of hypoeutectic or eutectic aluminum-silicon alloy, which comprises the following components in part by weight:
Al-Ti-B intermediate alloy, Al-Sr intermediate alloy and Al-RE intermediate alloy, wherein the addition proportion of the Al-Ti-B intermediate alloy is 0.01-0.04% of the melt mass of the hypoeutectic or eutectic aluminum-silicon alloy; the addition amount of Sr in the Al-Sr intermediate alloy is 0.01-0.05% of the mass of the melt; the addition amount of RE in the Al-RE intermediate alloy is 0.01-0.1% of the melt mass.
The invention provides a composite modification method for casting aluminum-silicon alloy, which mainly utilizes the composite modifier to modify;
wherein the composite modifier comprises Al-Ti-B intermediate alloy, Al-Sr intermediate alloy and Al-RE intermediate alloy, and the adding proportion of the Al-Ti-B intermediate alloy is 0.01-0.04% of the mass of the melt of the cast aluminum-silicon alloy; the addition amount of Sr in the Al-Sr intermediate alloy is 0.01-0.05% of the mass of the melt; the addition amount of RE in the Al-RE intermediate alloy is 0.01-0.1% of the melt mass.
The composite modification method for casting the aluminum-silicon alloy has the beneficial effects that:
the composite modification method for the cast aluminum-silicon alloy provided by the embodiment of the invention mainly utilizes a composite modifier to modify;
wherein the composite modifier comprises Al-Ti-B intermediate alloy, Al-Sr intermediate alloy and Al-RE intermediate alloy, and the adding proportion of the Al-Ti-B intermediate alloy is 0.01-0.04% of the mass of the melt of the cast aluminum-silicon alloy; the addition amount of Sr in the Al-Sr intermediate alloy is 0.01-0.05% of the mass of the melt; the addition amount of RE in the Al-RE intermediate alloy is 0.01-0.1% of the melt mass.
In the method, Al-Ti-B mainly plays a role in refining an alpha-Al matrix, Sr mainly plays a role in modifying eutectic silicon, Sr element is easy to burn and absorb gas, and the adding time and temperature are very important. Because the surface chemical activity of RE is very strong, on one hand, RE forms high-temperature particles through chemical reaction with [ H ] in the melt, which not only provides a large amount of nucleation particles for alpha-Al and refines crystal grains, but also reduces the air suction effect brought by adding Sr and purifies the melt; on the other hand, RE is easy to be adsorbed on the growth surfaces of alpha-Al and Si, the growth of crystal grains is inhibited, and the crystal grains are further refined. However, the addition amount of RE needs to be strictly controlled, and when the content is too high, Al-Ti-RE compounds are easily formed with Al and Ti, and the modifier is poisoned. In addition, as both Sr and RE elements are easy to burn out, the Sr and RE elements are added after refining and are slowly stirred by a tool to be uniformly distributed in the melt, so that the invention aims to reduce burning out and air suction caused by intense stirring and nonuniform temperature of the melt, and simultaneously, the air suction caused by adding the alterant is reduced by utilizing the degassing function of RE. Therefore, the composite modifier can not only simultaneously refine the eutectic silicon tissue and the alpha-Al matrix, but also achieve the purpose of degassing and purifying the melt, thereby greatly improving the toughness of the alloy.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.
FIG. 1 is a metallographic structure map of a ZL101 alloy under a macroscopic view without deterioration;
FIG. 2 is a metallographic structure map of a ZL101 alloy under a high power microscope without deterioration;
FIG. 3 is a metallographic graph of a ZL101 alloy under a macroscopic view after modification treatment according to example 1 of the invention;
FIG. 4 is a metallographic graph of a ZL101 alloy under a high power lens after modification treatment provided in example 1 of the invention;
FIG. 5 is a metallographic graph of a ZL101 alloy subjected to modification treatment under a low power microscope according to example 2 of the invention;
fig. 6 is a metallographic graph of the ZL101 alloy under a high power mirror after the modification treatment provided in example 2 of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.
The method of compositely modifying a cast aluminum-silicon alloy according to the embodiment of the present invention will be described in detail below.
The embodiment of the invention provides a composite modifier for composite modification of hypoeutectic or eutectic aluminum-silicon alloy, which comprises the following components in part by weight:
Al-Ti-B intermediate alloy, Al-Sr intermediate alloy and Al-RE intermediate alloy, wherein the addition proportion of the Al-Ti-B intermediate alloy is 0.01-0.04% of the melt mass of the hypoeutectic or eutectic aluminum-silicon alloy; the addition amount of Sr in the Al-Sr intermediate alloy is 0.01-0.05% of the mass of the melt; the addition amount of RE in the Al-RE intermediate alloy is 0.01-0.1% of the melt mass.
In detail, RE is a light rare earth element with relatively low price. Of the three components, Al-Ti-B mainly plays a role in refining an alpha-Al matrix, and Sr mainly plays a role in modifying eutectic silicon.
Further, in a preferred embodiment of the present invention, RE in the Al-RE master alloy is one or both of La and Ce.
A composite modification method for casting aluminum-silicon alloy mainly utilizes the composite modifier to modify;
wherein the composite modifier comprises Al-Ti-B intermediate alloy, Al-Sr intermediate alloy and Al-RE intermediate alloy, and the adding proportion of the Al-Ti-B intermediate alloy is 0.01-0.04% of the mass of the melt of the cast aluminum-silicon alloy; the addition amount of Sr in the Al-Sr intermediate alloy is 0.01-0.05% of the mass of the melt; the addition amount of RE in the Al-RE intermediate alloy is 0.01-0.1% of the melt mass.
Further, in a preferred embodiment of the present invention, a method for compositely modifying cast aluminum-silicon alloy comprises:
completely melting the cast aluminum-silicon alloy to obtain a melt;
carrying out on-line refining on the melt;
keeping the temperature for a period of time and then slagging off;
adding the preheated composite modifier wrapped by aluminum foil, pressing the preheated composite modifier into the melt by a titanium tool, and slowly stirring after melting to ensure that the composite modifier can be uniformly distributed in the melt;
standing for a period of time, and then casting into ingots or pouring baskets to prepare cast aluminum-silicon alloy ingots or castings.
In detail, in the method, Al-Ti-B mainly plays a role of refining an alpha-Al matrix, Sr mainly plays a role of modifying eutectic silicon, Sr element is easy to burn and absorb gas, and the adding time and temperature are very important. Because the surface chemical activity of RE is very strong, on one hand, RE forms high-temperature particles through chemical reaction with [ H ] in the melt, which not only provides a large amount of nucleation particles for alpha-Al and refines crystal grains, but also reduces the air suction effect brought by adding Sr and purifies the melt; on the other hand, RE is easy to be adsorbed on the growth surfaces of alpha-Al and Si, the growth of crystal grains is inhibited, and the crystal grains are further refined. However, the addition amount of RE needs to be strictly controlled, and when the content is too high, Al-Ti-RE compounds are easily formed with Al and Ti, and the modifier is poisoned. In addition, as both Sr and RE elements are easy to burn out, the Sr and RE elements are added after refining and are slowly stirred by a tool to be uniformly distributed in the melt, so that the invention aims to reduce burning out and air suction caused by intense stirring and nonuniform temperature of the melt, and simultaneously, the air suction caused by adding the alterant is reduced by utilizing the degassing function of RE. Therefore, the composite modifier can not only simultaneously refine the eutectic silicon tissue and the alpha-Al matrix, but also achieve the purpose of degassing and purifying the melt, thereby greatly improving the toughness of the alloy.
Further, in a preferred embodiment of the present invention, the melt obtained by completely melting the cast aluminum-silicon alloy specifically comprises:
putting the prepared raw materials for casting the aluminum-silicon alloy into a smelting furnace;
heating the raw material to 500 ℃, then preserving heat for 30min, then raising the temperature to 750-800 ℃, further, in the preferred embodiment of the invention, before the melt is refined on line, the temperature of the melt is reduced to 700-720 ℃. The burning loss and the suction gas caused by refining can be further reduced by controlling the temperature and the time. Of course, in other embodiments of the present invention, the temperature and the time may also be adjusted accordingly according to requirements, and the embodiments of the present invention are not limited.
Further, in a preferred embodiment of the present invention, the step of removing the slag after the step of maintaining the temperature for a period of time is performed for a period of time of 15-30 min.
Further, in a preferred embodiment of the invention, in the step of preparing the cast aluminum-silicon alloy ingot or casting by casting the ingot or the tundish after standing for a period of time, the period of time is 30-60 min.
The features and properties of the present invention are described in further detail below with reference to examples.
The chemical components of commercial ZL101 hypoeutectic aluminum-silicon casting aluminum alloy selected in the embodiment of the invention are shown in the table 1, and the metallographic structure atlas of the alloy before modification is shown in figures 1 and 2.
Table 1 chemical composition (wt.%) of the materials selected for use in the examples
Alloy brand
|
Si
|
Fe
|
Mg
|
Mn
|
Cu
|
Ti
|
Others
|
Al
|
ZL101
|
7.28
|
0.12
|
0.38
|
0.02
|
0.013
|
0.02
|
≤0.15
|
Balance of |
Example 1
The embodiment provides a composite modification method for casting aluminum-silicon alloy, which comprises the following steps:
s1: adding the prepared alloy raw materials into a smelting furnace, heating the raw materials to 500 ℃, preserving heat for 30 minutes, and then heating to 750 ℃;
s2: after the raw materials were completely melted, the melt temperature was lowered to 700 ℃. The aluminium melt is subsequently refined on-line.
S3: keeping the temperature for 15 minutes, removing slag, adding preheated Al-Ti-B, Al-Sr intermediate alloy which is wrapped by aluminum foil, wherein the adding amount of Al-Ti-B, Sr is 0.02 percent and 0.04 percent of the mass of the melt respectively, then pressing the intermediate alloy into the melt by a titanium tool, and slowly stirring the melt after melting to ensure that the intermediate alloy is uniformly distributed.
S4: and (4) standing the melt for 60 minutes, and then casting the melt into ingots to prepare cast 1# aluminum alloy ingots.
After the modification treatment, the chemical compositions of the alloy are tested, and the microstructure of the alloy is observed by a microscope, and the metallographic structure of the alloy is shown in figures 3 and 3. Meanwhile, the tensile mechanical property of the alloy is tested by using a universal mechanical testing machine after the cast ingot is subjected to T5 heat treatment.
Example 2
The embodiment provides a composite modification method for casting aluminum-silicon alloy, which comprises the following steps:
s1: adding the prepared alloy raw materials into a smelting furnace, heating the raw materials to 500 ℃, preserving heat for 30 minutes, and then heating to 800 ℃;
s2: after the raw materials were completely melted, the melt temperature was lowered to 710 ℃. The aluminium melt is subsequently refined on-line.
S3: and after the temperature is kept for 30 minutes, slagging off, adding Al-Ti-B, Al-Sr and Al-RE intermediate alloy which are well wrapped by aluminum foil and preheated, wherein the adding amounts of Al-Ti-B, Sr and RE are respectively 0.02 percent, 0.04 percent and 0.05 percent of the mass of the melt, pressing the intermediate alloy into the melt by using a titanium tool, and slowly stirring the melt after melting to uniformly distribute the intermediate alloy.
S4: and standing the melt for 60 minutes, and then casting the melt into ingots to prepare cast aluminum alloy ingots.
The chemical components of the alloy are tested after modification, the microstructure of the alloy is observed by a microscope, the metallographic structure of the alloy is shown in figures 5 and 6, and the tensile mechanical property of the alloy is tested by a universal mechanical testing machine after T5 heat treatment is carried out on the cast ingot.
Example 3
The embodiment provides a composite modification method for casting aluminum-silicon alloy, which comprises the following steps:
s1: adding the prepared alloy raw materials into a smelting furnace, heating the raw materials to 500 ℃, preserving heat for 30 minutes, and then heating to 760 ℃;
s2: after the raw materials were completely melted, the melt temperature was lowered to 720 ℃. The aluminium melt is subsequently refined on-line.
S3: and after the temperature is kept for 20 minutes, slagging off, adding Al-Ti-B, Al-Sr and Al-RE intermediate alloy which are wrapped by aluminum foil and preheated, wherein the adding amounts of Al-Ti-B, Sr and RE are respectively 0.04 percent, 0.03 percent and 0.05 percent of the mass of the melt, pressing the intermediate alloy into the melt by using a titanium tool, and slowly stirring the melt after melting to uniformly distribute the intermediate alloy.
S4: and standing the melt for 40 minutes, and then casting the melt into ingots to prepare cast aluminum alloy ingots.
After modification, the chemical components of the alloy are tested, the macroscopic and macroscopic structures of the alloy are observed by a microscope, and after T5 heat treatment is carried out on the cast ingot, the tensile mechanical property of the alloy is tested by a universal mechanical testing machine.
Example 4
The embodiment provides a composite modification method for casting aluminum-silicon alloy, which comprises the following steps:
s1: adding the prepared alloy raw materials into a smelting furnace, heating the raw materials to 500 ℃, preserving heat for 30 minutes, and then heating to 780 ℃;
s2: after the raw materials were completely melted, the melt temperature was lowered to 720 ℃. The aluminium melt is subsequently refined on-line.
S3: and after the temperature is kept for 30 minutes, slagging off, adding preheated Al-Ti-B, Al-Sr and Al-RE intermediate alloy which are wrapped by aluminum foil, wherein the adding amount of Al-Ti-B, Sr and RE is respectively 0.01 percent, 0.02 percent and 0.1 percent of the mass of the melt, pressing the melt into the melt by using a titanium tool, and slowly stirring the melt after melting to uniformly distribute the melt.
S4: and standing the melt for 30 minutes, transferring the melt to a tundish, and preparing a cast Al-Si alloy casting.
After modification, the chemical components of the alloy are tested, the macroscopic and macroscopic structures of the alloy are observed by a microscope, and after T5 heat treatment is carried out on the casting, the tensile mechanical property of the alloy is tested by a universal mechanical testing machine.
The chemical compositions of the cast aluminum alloys of examples 1 to 4 after the composite modification are shown in Table 2.
TABLE 2 compositions of alloys after compound modification in examples 1 to 4
Examples
|
Si
|
Fe
|
Mg
|
Mn
|
Cu
|
Ti
|
Others
|
Al
|
1
|
7.28
|
0.12
|
0.38
|
0.02
|
0.013
|
0.02
|
≤0.15
|
Balance of
|
2
|
7.09
|
0.14
|
0.35
|
0.02
|
0.011
|
0.03
|
≤0.15
|
Balance of
|
3
|
7.17
|
0.15
|
0.33
|
0.03
|
0.008
|
0.03
|
≤0.15
|
Balance of
|
4
|
7.24
|
0.13
|
0.36
|
0.02
|
0.01
|
0.03
|
≤0.15
|
Balance of |
In examples 1 to 4, statistics of as-cast structure characteristic data before and after composite modification of cast aluminum alloys are shown in Table 3.
TABLE 3 statistics of tissue characterization data before and after compound modification in examples 1-4
Examples
|
Second order dendrite spacing (mum)
|
Average area of eutectic silicon (mum)2)
|
Eutectic silicon roundness
|
Before deterioration
|
50
|
38.2
|
4.43
|
1
|
40
|
7.9
|
2.43
|
2
|
32
|
7.2
|
2.41
|
3
|
34
|
6.4
|
2.37
|
4
|
33
|
6.9
|
2.39 |
The mechanical properties in the T5 state before and after the composite modification of the cast aluminum alloy of examples 1-4 are shown in Table 4.
TABLE 4 mechanical properties in the T5 state of the alloys after composite modification in examples 1-4
Examples
|
Tensile strength (MPa)
|
Yield strength (MPa)
|
Elongation (%)
|
Before deterioration
|
255
|
170
|
8.0
|
1
|
250
|
155
|
13.9
|
2
|
255
|
170
|
16.9
|
3
|
265
|
165
|
19.0
|
4
|
255
|
155
|
16.1 |
In summary, it can be seen from the data in tables 1 to 4 and fig. 1 to 5 of the embodiments of the present invention that the composite modifier provided in the embodiments of the present invention is used for composite modification of hypoeutectic or eutectic aluminum-silicon alloy, and the composite modifier can achieve the purpose of simultaneously refining α -Al crystal grains and modifying eutectic silicon, thereby improving the tensile strength and elongation of the alloy. The composite modification method for the cast aluminum-silicon alloy provided by the embodiment of the invention mainly utilizes the composite modifier to perform composite modification. Therefore, the method has low cost and easy operation, can achieve the aim of simultaneously refining alpha-Al crystal grains and modifying eutectic silicon through composite modification, and reduces the addition amount of Sr and Al-Ti-B, thereby improving the tensile strength and the elongation of the alloy and simultaneously improving the toughness of the cast aluminum alloy.
The embodiments described above are some, but not all embodiments of the invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.