CN109439976B - A compound modification method of cast aluminum-silicon alloy - Google Patents

Abstract

The invention discloses a method for compound modification of cast aluminum-silicon alloy, and relates to the technical field of modification of cast aluminum alloy. The method mainly utilizes composite modifiers for modification; wherein, the composite modifiers include Al-Ti-B master alloys, Al-Sr master alloys and Al-RE master alloys, and the addition ratio of Al-Ti-B master alloys is cast aluminum-silicon 0.01% to 0.04% of the mass of the melt of the alloy; the addition of Sr to the Al‑Sr master alloy is 0.01 to 0.05% of the mass of the melt; the addition of RE to the Al‑RE master alloy is 0.01% to 0.1% of the mass of the melt %. The method is low in cost and easy to operate, and through compound modification, the purpose of simultaneously refining α-Al grains and modifying eutectic silicon can be achieved, and the addition of Sr and Al-Ti-B can be reduced, thereby improving the tensile strength of the alloy and elongation, while improving the strength and toughness of cast aluminum alloy.

Description

A compound modification method of cast aluminum-silicon alloy

technical field

The invention relates to the technical field of modification of cast aluminum alloys, and in particular to a compound modification method of cast aluminum-silicon alloys.

Background technique

Al-Si series cast aluminum alloys have the advantages of excellent casting fluidity and air tightness, small thermal expansion coefficient, good weldability and machining properties, and are widely used in the fields of automobiles and motorcycles, aerospace, communications and electronic appliances. According to statistics, in 2017, the output of aluminum alloy castings in my country reached 7.92 million tons, of which aluminum-silicon alloy castings accounted for about 85% to 90%. Among the automotive product castings, aluminum-silicon alloy castings also account for more than 80% of the total automotive castings, becoming one of the most important lightweight materials for automotive lightweighting. With the gradual increase in the lightweight requirements of new energy vehicles and the communication industry, the requirements for the strength and toughness of cast aluminum alloys are also getting higher and higher.

Refining the alloy structure is one of the effective means of strengthening and toughening metals, among which modification treatment has the characteristics of low cost, simple method and remarkable effect, and has become one of the most effective ways to improve the structure and properties of aluminum alloys. At present, the refiners commonly used for α-Al refinement include Al-Ti-B, Al-Ti, Al-Ti-C, RE, etc., among which Al-Ti-B is the most commonly used, but for cast aluminum alloys containing Zr Not applicable, and there are also problems of segregation and sedimentation; Sr is recognized as the best eutectic silicon modifier in the industry, but Sr is chemically active, easy to burn and absorb gas, and damage the mechanical properties of the alloy. In order to refine α-Al and eutectic silicon at the same time, a composite modification process is usually used, but simply adding Sr and Al-Ti-B in combination still cannot solve the problems of Sr gettering and burning. RE is a kind of surface active element, which can not only inhibit the grain growth in aluminum alloy, but also form compounds with [H], which has the function of degassing and purifying the melt. Zhang Jiahong【Zhang Jiahong, Xing Shuming.Al-Si alloy modification elements and their interaction[J].Materials Herald, 2018,32(11):1870-1877.】reviewed the effective refinement of Sr, La and Sr, Y compound modification Secondary dendrite spacing and eutectic silicon structure; Lan Yefeng [Lan Yefeng, Guo Peng, Zhang Jijun. Effect of rare earths on the refining properties of Al-Ti-B-RE master alloys [J]. Casting Technology, 2005( 09): 774-775.] confirmed that the addition of RE has greatly improved the refinement ability and timeliness of Al-Ti-B. It can be seen that although RE can improve the modification and refinement ability of Sr and Al-Ti-B to a certain extent, it cannot realize the synchronous refinement of eutectic silicon and α-Al grains, and improve the alloy's alloy to a greater extent. toughness.

Contents of the invention

The object of the present invention is to provide a composite modifier for composite modification of hypoeutectic or eutectic Al-Si alloys, and the composite modifier can simultaneously refine α-Al grains and modify eutectic silicon, Thereby increasing the tensile strength and elongation of the alloy.

Another object of the present invention is to provide a method for composite modification of cast aluminum-silicon alloy, which method mainly uses the above-mentioned composite modification agent for composite modification. Therefore, this method is low in cost and easy to operate, and the purpose of simultaneously refining α-Al grains and modifying eutectic silicon can be achieved through compound modification, and the addition of Sr and Al-Ti-B can be reduced, thereby improving the alloy’s resistance to corrosion. Tensile strength and elongation, while improving the strength and toughness of cast aluminum alloy.

The present invention solves its technical problems by adopting the following technical solutions.

The present invention proposes a composite modifier for composite modification of hypoeutectic or eutectic aluminum-silicon alloys. The composite modifier includes:

Al-Ti-B master alloy, Al-Sr master alloy and Al-RE master alloy, wherein the addition ratio of Al-Ti-B master alloy is 0.01%~ 0.04%; the amount of Sr added in the Al-Sr master alloy is 0.01-0.05% of the mass of the melt; the amount of RE added in the Al-RE master alloy is 0.01%-0.1% of the mass of the melt.

The present invention proposes a method for compound modification of cast aluminum-silicon alloy, which mainly utilizes the above-mentioned compound modification agent for modification;

Among them, the composite modifier includes Al-Ti-B master alloy, Al-Sr master alloy and Al-RE master alloy, and the addition ratio of Al-Ti-B master alloy is 0.01% to 0.04% of the melt mass of the cast aluminum-silicon alloy. %; the amount of Sr added in the Al-Sr master alloy is 0.01% to 0.05% of the melt mass; the amount of RE added in the Al-RE master alloy is 0.01% to 0.1% of the melt mass.

The beneficial effect of the compound modification method of cast aluminum-silicon alloy of the embodiment of the present invention is:

The composite modification method of the cast aluminum-silicon alloy provided by the embodiment of the present invention mainly uses a composite modification agent for modification;

Among them, the composite modifier includes Al-Ti-B master alloy, Al-Sr master alloy and Al-RE master alloy, and the addition ratio of Al-Ti-B master alloy is 0.01% to 0.04% of the melt mass of the cast aluminum-silicon alloy. %; the amount of Sr added in the Al-Sr master alloy is 0.01% to 0.05% of the melt mass; the amount of RE added in the Al-RE master alloy is 0.01% to 0.1% of the melt mass.

In this method, Al-Ti-B mainly plays the role of refining the α-Al matrix, while Sr mainly plays the role of modifying the eutectic silicon. Since the Sr element is easy to burn and absorb gas, the timing and temperature of addition are very important. Importantly, the present invention chooses to add after degassing and impurity removal during refining, and the temperature is also the casting temperature, the purpose is to reduce burning loss and gas absorption caused by refining. Due to the strong surface chemical activity of RE, on the one hand, RE reacts with [H] in the melt to form high-temperature particles, which not only provides a large number of nucleation particles for α-Al, refines the grains, but also reduces the Because of the getter effect brought by adding Sr, the melt is purified; on the other hand, RE is easily adsorbed on the growth surface of α-Al and Si, which inhibits the growth of grains and further refines the grains. However, the addition amount of RE needs to be strictly controlled. When the content is too high, it is easy to form Al-Ti-RE compound with Al and Ti, poisoning the modificator. In addition, since both Sr and RE elements are easy to be burned, the present invention chooses to add them after refining, and slowly stir them with tools to make them evenly distributed in the melt. The purpose is to reduce the burning caused by violent stirring and uneven temperature of the melt Loss and suction, while using the degassing function of RE to reduce the suction caused by adding modifiers. Therefore, the composite modifier of the present invention can not only refine the α-Al matrix and refine the eutectic silicon structure, but also achieve the purpose of degassing and purifying the melt, and greatly improve the strength and toughness of the alloy.

Description of drawings

In order to illustrate the technical solutions of the embodiments of the present invention more clearly, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention, and thus It should be regarded as a limitation on the scope, and those skilled in the art can also obtain other related drawings based on these drawings without creative work.

Fig. 1 is the metallographic structure map of the unmodified ZL101 alloy under low magnification;

Fig. 2 is the metallographic structure diagram of the unmodified ZL101 alloy under a high-power lens;

Fig. 3 is the metallographic spectrum of the modified ZL101 alloy provided by Example 1 of the present invention under a low-magnification lens;

Fig. 4 is the metallographic spectrum of the modified ZL101 alloy provided by Example 1 of the present invention under a high-power lens;

Fig. 5 is the metallographic spectrum of the modified ZL101 alloy provided by Example 2 of the present invention under a low magnification lens;

Fig. 6 is a metallographic spectrum of the modified ZL101 alloy provided in Example 2 of the present invention under a high-power microscope.

Detailed ways

In order to make the purpose, 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. Those who do not indicate the specific conditions in the examples are carried out according to the conventional conditions or the conditions suggested by the manufacturer. The reagents or instruments used were not indicated by the manufacturer, and they were all conventional products that could be purchased from the market.

The compound modification method of the cast aluminum-silicon alloy according to the embodiment of the present invention will be described in detail below.

Embodiments of the present invention provide a composite modifier for composite modification of hypoeutectic or eutectic aluminum-silicon alloys. The composite modifier includes:

Al-Ti-B master alloy, Al-Sr master alloy and Al-RE master alloy, wherein the addition ratio of Al-Ti-B master alloy is 0.01%~ 0.04%; the amount of Sr added in the Al-Sr master alloy is 0.01-0.05% of the mass of the melt; the amount of RE added in the Al-RE master alloy is 0.01%-0.1% of the mass of the melt.

Specifically, RE uses relatively cheap light rare earth elements. Among the three components, Al-Ti-B mainly plays the role of refining the α-Al matrix, while Sr mainly plays the role of 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 method for compound modification of cast aluminum-silicon alloy, which mainly uses the above-mentioned compound modification agent for modification;

Among them, the composite modifier includes Al-Ti-B master alloy, Al-Sr master alloy and Al-RE master alloy, and the addition ratio of Al-Ti-B master alloy is 0.01% to 0.04% of the melt mass of the cast aluminum-silicon alloy. %; the amount of Sr added in the Al-Sr master alloy is 0.01% to 0.05% of the melt mass; the amount of RE added in the Al-RE master alloy is 0.01% to 0.1% of the melt mass.

Further, in a preferred embodiment of the present invention, the method for compound modification of cast aluminum-silicon alloy includes:

Melting the cast aluminum-silicon alloy to obtain a melt;

On-line refining of the melt;

Remove slag after keeping warm for a period of time;

Add the preheated composite modifier wrapped in aluminum foil, press it into the melt with a titanium tool, and stir slowly after melting so that the composite modifier can be evenly distributed in the melt;

After standing for a period of time, it is cast into ingots or tundishes to prepare cast aluminum-silicon alloy ingots or castings.

In detail, in this method, Al-Ti-B mainly plays the role of refining the α-Al matrix, while Sr mainly plays the role of modifying eutectic silicon. Since Sr element is easy to burn out and get gas, the timing and timing of adding The temperature is very important. The present invention chooses to add it after refining and degassing and removing impurities. The temperature is also the casting temperature. The purpose is to reduce the burning loss and gas absorption caused by refining. Due to the strong surface chemical activity of RE, on the one hand, RE reacts with [H] in the melt to form high-temperature particles, which not only provides a large number of nucleation particles for α-Al, refines the grains, but also reduces the Because of the getter effect brought by adding Sr, the melt is purified; on the other hand, RE is easily adsorbed on the growth surface of α-Al and Si, which inhibits the growth of grains and further refines the grains. However, the addition amount of RE needs to be strictly controlled. When the content is too high, it is easy to form Al-Ti-RE compound with Al and Ti, poisoning the modificator. In addition, since both Sr and RE elements are easy to be burned, the present invention chooses to add them after refining, and slowly stir them with tools to make them evenly distributed in the melt. The purpose is to reduce the burning caused by violent stirring and uneven temperature of the melt Loss and suction, while using the degassing function of RE to reduce the suction caused by adding modifiers. Therefore, the composite modifier of the present invention can not only refine the α-Al matrix and refine the eutectic silicon structure, but also achieve the purpose of degassing and purifying the melt, and greatly improve the strength and toughness of the alloy.

Further, in a preferred embodiment of the present invention, the melt obtained after melting all the cast aluminum-silicon alloy specifically includes:

Put the prepared raw materials of cast aluminum-silicon alloy into the melting furnace;

Heat the raw material to 500°C and keep it warm for 30 minutes, then raise the temperature to 750-800°C. Further, in a preferred embodiment of the present invention, the temperature of the melt is lowered to 700-720°C before online refining. ℃. The burning loss and gas absorption caused by refining can be further reduced by controlling the temperature and time. Of course, in other embodiments of the present invention, the temperature and time can also be adjusted accordingly according to requirements, which are not limited in this embodiment of the present invention.

Further, in a preferred embodiment of the present invention, in the step of removing slag after holding for a period of time, the period of time is 15-30 minutes.

Further, in a preferred embodiment of the present invention, in the step of preparing cast aluminum-silicon alloy ingots or castings by casting into ingots or tundishes after standing for a period of time, the period of time is 30-60 minutes.

The characteristics and performance of the present invention will be described in further detail below in conjunction with the examples.

In the embodiment of the present invention, a commercial ZL101 hypoeutectic aluminum-silicon cast aluminum alloy is selected. The chemical composition is shown in Table 1. The metallographic structure of the alloy before modification is shown in FIG. 1 and FIG. 2 .

The chemical composition (wt.%) of the selected material of table 1 embodiment

Alloy grade Si Fe Mg mn Cu Ti other Al ZL101 7.28 0.12 0.38 0.02 0.013 0.02 ≤0.15 margin

Example 1

This embodiment provides a method for compound modification of cast aluminum-silicon alloy, which includes the following steps:

S1: Put the prepared alloy raw materials into the melting furnace, heat the raw materials to 500°C, keep them warm for 30 minutes, and then raise the temperature to 750°C;

S2: After all the raw materials are melted, the melt temperature is lowered to 700°C. The aluminum melt is subsequently refined in-line.

S3: Remove slag after 15 minutes of heat preservation, add Al-Ti-B and Al-Sr master alloys wrapped in aluminum foil, and the amount of Al-Ti-B and Sr added is 0.02% of the mass of the melt respectively , 0.04%, and then press it into the melt with a titanium tool, and slowly stir the melt after melting to make it evenly distributed.

S4: The melt was left to stand for 60 minutes and then cast into an ingot to prepare a cast 1# aluminum alloy ingot.

After the modification treatment, the chemical composition of the alloy was tested, and the low-magnification and high-magnification structures of the alloy were observed with a microscope. The metallographic structure is shown in Figure 3 and Figure 3. At the same time, the tensile mechanical properties of the alloy were tested with a universal mechanical testing machine after T5 heat treatment on the ingot.

Example 2

This embodiment provides a method for compound modification of cast aluminum-silicon alloy, which includes the following steps:

S1: Put the prepared alloy raw materials into the melting furnace, heat the raw materials to 500°C, keep them warm for 30 minutes, and then raise the temperature to 800°C;

S2: After all the raw materials are melted, the temperature of the melt is lowered to 710°C. The aluminum melt is subsequently refined in-line.

S3: After 30 minutes of heat preservation, remove the slag, add the preheated Al-Ti-B, Al-Sr, Al-RE master alloys wrapped in aluminum foil, and the addition amounts of Al-Ti-B, Sr, and RE are respectively 0.02%, 0.04%, and 0.05% of the mass of the melt are pressed into the interior of the melt with titanium tools, and after melting, the melt is slowly stirred to make it evenly distributed.

S4: The melt was left to stand for 60 minutes and then cast into an ingot to prepare a cast aluminum alloy ingot.

The chemical composition of the alloy was tested after the modification treatment, and the low-magnification and high-magnification structures of the alloy were observed with a microscope. The metallographic structure is shown in Figure 5 and Figure 6. At the same time, the ingot was subjected to T5 heat treatment and the alloy was tested with a universal mechanical testing machine. Tensile mechanical properties.

Example 3

This embodiment provides a method for compound modification of cast aluminum-silicon alloy, which includes the following steps:

S1: Put the prepared alloy raw materials into the melting furnace, heat the raw materials to 500°C, keep them warm for 30 minutes, and then raise the temperature to 760°C;

S2: After all the raw materials are melted, the temperature of the melt is lowered to 720°C. The aluminum melt is subsequently refined in-line.

S3: After keeping warm for 20 minutes, remove the slag, add the preheated Al-Ti-B, Al-Sr, Al-RE master alloys wrapped in aluminum foil, and the addition amounts of Al-Ti-B, Sr, and RE are respectively 0.04%, 0.03%, and 0.05% of the mass of the melt are pressed into the interior of the melt with a titanium tool, and after melting, the melt is slowly stirred to make it evenly distributed.

S4: The melt was left to stand for 40 minutes and then cast into an ingot to prepare a cast aluminum alloy ingot.

After the modification treatment, the chemical composition of the alloy was tested, the low-magnification and high-magnification structures of the alloy were observed with a microscope, and the tensile mechanical properties of the alloy were tested with a universal mechanical testing machine after T5 heat treatment on the ingot.

Example 4

This embodiment provides a method for compound modification of cast aluminum-silicon alloy, which includes the following steps:

S1: Put the prepared alloy raw materials into the melting furnace, heat the raw materials to 500°C, keep them warm for 30 minutes, and then raise the temperature to 780°C;

S2: After all the raw materials are melted, the temperature of the melt is lowered to 720°C. The aluminum melt is subsequently refined in-line.

S3: After 30 minutes of heat preservation, remove the slag, add the preheated Al-Ti-B, Al-Sr, Al-RE master alloys wrapped in aluminum foil, and the addition amounts of Al-Ti-B, Sr, and RE are respectively 0.01%, 0.02%, and 0.1% of the mass of the melt are pressed into the interior of the melt with titanium tools, and after melting, the melt is slowly stirred to make it evenly distributed.

S4: After the melt is left to stand for 30 minutes, it is transferred to a tundish to prepare an Al-Si alloy casting.

After the modification treatment, the chemical composition of the alloy is tested, the low-magnification and high-magnification structures of the alloy are observed with a microscope, and the tensile mechanical properties of the alloy are tested with a universal mechanical testing machine after T5 heat treatment of the casting.

See Table 2 for the chemical composition of the cast aluminum alloys in Examples 1-4 after composite modification.

Table 2 Composition of Alloys After Composite Modification in Examples 1 to 4

Example Si Fe Mg mn Cu Ti other Al 1 7.28 0.12 0.38 0.02 0.013 0.02 ≤0.15 margin 2 7.09 0.14 0.35 0.02 0.011 0.03 ≤0.15 margin 3 7.17 0.15 0.33 0.03 0.008 0.03 ≤0.15 margin 4 7.24 0.13 0.36 0.02 0.01 0.03 ≤0.15 margin

Table 3 Statistical data of as-cast microstructure characteristics before and after composite modification of cast aluminum alloys in Examples 1 to 4.

Table 3 Statistics of tissue characteristics data before and after composite metamorphism of Examples 1 to 4

Example Secondary dendrite spacing (μm) Average area of eutectic silicon (μm²) Eutectic silicon roundness before spoilage 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

Table 4 shows the mechanical properties of the T5 state before and after composite modification of the cast aluminum alloys of Examples 1-4.

Table 4 T5 state mechanical properties of the alloy after composite modification of Examples 1 to 4

Example Tensile strength (MPa) Yield strength (MPa) Elongation (%) before spoilage 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, according to the data in Table 1 to Table 4 and Figures 1 to 5 in the embodiments of the present invention, it can be known that the composite modifier provided by the embodiments of the present invention is used for composite modification of hypoeutectic or eutectic Al-Si alloys , and the compound modifier can achieve the purpose of refining α-Al grains and modifying eutectic silicon at the same time, thereby improving the tensile strength and elongation of the alloy. The embodiment of the present invention provides a method for composite modification of cast aluminum-silicon alloy, which mainly uses the above-mentioned composite modification agent for composite modification. Therefore, this method is low in cost and easy to operate, and the purpose of simultaneously refining α-Al grains and modifying eutectic silicon can be achieved through compound modification, and the addition of Sr and Al-Ti-B can be reduced, thereby improving the alloy’s resistance to corrosion. Tensile strength and elongation, while improving the strength and toughness of cast aluminum alloy.

The embodiments described above are some, not all, embodiments of the present invention. The detailed description of the embodiments of the invention is not intended to limit the scope of the claimed invention but to represent only selected embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

Claims (5)

1. A composite metamorphic method of cast aluminum-silicon alloy, characterized in that: The composite modification method of the cast aluminum-silicon alloy mainly utilizes a composite modification agent for modification; Wherein, the composite modifier is used to simultaneously refine α-Al grains and modify eutectic silicon, and the composite modifier is composed of Al-Ti-B master alloy, Al-Sr master alloy and Al-RE master alloy, The addition ratio of the Al-Ti-B master alloy is 0.01%~0.04% of the melt mass of the cast aluminum-silicon alloy; the addition amount of Sr in the Al-Sr master alloy is 0.01~0.05% of the melt mass %; the amount of RE added in the Al-RE master alloy is 0.01%~0.1% of the melt quality; The RE in the Al-RE master alloy is one or both of La or Ce; Wherein, the composite modification method of the cast aluminum-silicon alloy includes: Melting the cast aluminum-silicon alloy to obtain a melt; performing on-line refining of the melt; Remove slag after keeping warm for a period of time; Add the preheated composite modifier wrapped in aluminum foil, press it into the melt with a titanium tool, and stir slowly after melting to distribute the composite modifier evenly in the melt middle; After standing for a period of time, it is cast into an ingot to prepare a cast aluminum-silicon alloy ingot. 2. The compound modification method of cast aluminum-silicon alloy according to claim 1, characterized in that, obtaining the melt after all the cast aluminum-silicon alloy is melted specifically comprises: Put the prepared raw materials of cast aluminum-silicon alloy into the melting furnace; The raw material is heated to 500° C., then kept for 30 minutes, and then heated to 750-800° C., so that the raw material is melted to obtain the melt. 3. the compound metamorphic method of cast aluminum-silicon alloy according to claim 1, is characterized in that: Before the on-line refining of the melt, it also includes reducing the temperature of the melt to 700-720°C. 4. the composite modification method of cast aluminum-silicon alloy according to claim 1, is characterized in that: In the step of removing slag after a period of heat preservation, the period of time is 15 to 30 minutes. 5. the composite modification method of cast aluminum-silicon alloy according to claim 1, is characterized in that: In the step of preparing cast aluminum-silicon alloy ingots by casting them into ingots after standing for a period of time, the period of time is 30-60 minutes.