CN103331432A - Vacuum die casting method of rare earth-magnesium alloy - Google Patents

Abstract

The invention discloses a vacuum die-casting method for a rare earth magnesium alloy. First melt and mix pure magnesium ingots, Mg-90%Gd, Mg-25%Y, Mg-30%Zr master alloys; then use Toyo 250-ton cold chamber horizontal die-casting machine to die-cast the molten metal. The steps are as follows: mold pre-casting Heat to 150-180°C, add metal alloy melt at 680-720°C, press the punch in at a low speed of 200-300mm/s, when the punch advances to 120mm, the die-casting machine is vacuumed to 6-15kPa, punch The head keeps moving. When the punch travels to 255-260mm, it starts to press in at a high speed of 4-6m/s. The boost pressure is set at 12-13MPa. After the die-casting is completed, the metal is cooled and taken out. The pores and shrinkage cavities of the casting obtained by the invention are reduced, and the tensile strength, yield strength and elongation are improved.

Description

A kind of vacuum die-casting method of rare earth magnesium alloy

technical field

The invention relates to a preparation method of a metal alloy material, in particular to a vacuum die-casting method of a rare earth magnesium alloy.

Background technique

Magnesium alloys have the advantages of low density, light weight, high specific strength, and good machinability, and are widely used in the fields of aerospace, transportation, and electronic products. At this stage, most magnesium alloy materials are formed by die-casting method, which is a forming method in which liquid metal fills the mold cavity at a very high speed under high pressure, and is cooled and solidified under pressure to obtain a casting. .

In the above-mentioned conventional die-casting method, because the molten metal fills the mold cavity in a high-speed spray state, most of the gas in the cavity is too late to be discharged and inevitably involved in the molten metal, and remains in the casting in the form of pores, so ordinary die-casting Parts inevitably have porosity defects. According to research by Lee Soon Gi and others, the pores formed during the solidification process of die castings will affect the heat transfer of the surrounding molten metal, thus making it easy to form shrinkage porosity around the pores. Moreover, the existence of pores makes it difficult for conventional die castings to be heat treated, welded or used in parts with high air tightness requirements, and the mechanical properties of die castings cannot be further improved, which limits the use of die castings in important or large and complex applications. Application on stress-bearing parts such as car and motorcycle security parts.

For a long time, in order to improve the performance of conventional die castings and broaden the application range of die castings, people have conducted research on conventional die casting methods, especially the relationship between die casting methods and the performance and defects of die castings. However, in the conventional die-casting process, porosity defects and the resulting performance problems can hardly be well resolved. At the same time, people have also developed some new special die-casting methods, such as laminar flow filling method or ultra-low speed die-casting method, oxygen-filled die-casting method, etc. The main purpose of the above-mentioned methods is to reduce the amount of entrained gas in the process of filling the molten metal, thereby improving the mechanical properties of the casting. Due to the low production efficiency of the laminar flow filling method, the complex operation process of the oxygen-filled die-casting method, and the difficulty in controlling the parameters of the method, these two methods are rarely used in actual production.

The vacuum die casting method is to extract the gas in the cavity, and the molten metal fills the cavity in a vacuum state, so less gas is involved and the mechanical properties of the casting are high. And vacuum die-casting is the same as ordinary die-casting method, which is easy to operate and does not reduce production efficiency. Therefore, vacuum die-casting method has shown strong vitality since its appearance. With the improvement of related technologies, its application is becoming more and more extensive. However, the research on the die-casting method of rare earth magnesium alloy, especially the research on the vacuum die-casting method is still immature.

For rare earth magnesium alloys, heat treatment strengthening is crucial to the improvement of its performance, so the present invention is committed to developing a vacuum die-casting method for rare earth magnesium alloys. Under the method conditions, compared with conventional die-casting, the prepared sample has The performance is improved, and after heat treatment, the performance is further improved, thereby broadening the application of magnesium alloys.

Contents of the invention

The object of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a vacuum die-casting method for rare earth magnesium alloys.

The purpose of the invention can be achieved through the following technical solutions:

A vacuum die-casting method for a rare earth magnesium alloy, comprising the following steps:

Step 1, mixing and melting pure magnesium ingots and magnesium-rare earth master alloys to form rare earth magnesium alloy molten metal, and keeping the molten metal at 680-720°C;

Step 2. Die-cast the above-mentioned rare earth magnesium alloy metal liquid in a die-casting machine. The die-casting parameters are set as follows: the low-speed speed is 0.2-0.3m/s, the high-speed speed is 4-6m/s, and the high-low speed switching position is 255-260mm; The vacuum position is 120mm, and the vacuum degree is 5-15kPa; the boost position is 280-290mm, and the boost pressure is 12-13MPa.

A vacuum die-casting method for rare earth magnesium alloys, the further technical solution is that the die-casting machine adopts Toyo 250-ton cold chamber horizontal die-casting machine.

A vacuum die-casting method for a rare earth magnesium alloy, the further technical solution is that the rare earth magnesium alloy metal liquid is Mg-8Gd-3Y-0.5Zr or Mg-6Gd-3Y-0.5Zr.

A vacuum die-casting method of a rare earth magnesium alloy, the further technical proposal is that the metal liquid of the rare earth magnesium alloy is protected by a mixed gas of SF ₆ and N ₂ .

The aforementioned magnesium-rare earth master alloys specifically refer to: Mg-90%Gd, Mg-25%Y, Mg-30%Zr master alloys.

The preparation of the rare earth magnesium alloy molten metal is carried out according to the following steps: first, preheat the pure magnesium ingot and Mg-90%Gd, Mg-25%Y, Mg-30%Zr master alloy to 150 ℃ ~ 250 ℃; secondly, the pure magnesium ingot Put it into the melting furnace, after the magnesium ingot is melted, raise the temperature of the melt to 680℃～700℃, then put the preheated Mg-90%Gd and Mg-25%Y master alloy into the melting furnace, wait for melting After completion, raise the temperature to 740-760°C, put Mg-30%Zr into the smelting furnace, and when the temperature returns to 740-760°C, continue the power supply for refining, stir to make it evenly mixed, and let it stand. Then lower the temperature to 680-720°C, scrape off the scum on the surface, and carry out vacuum die-casting.

According to different proportions of pure magnesium ingots and Mg-90%Gd, Mg-25%Y, Mg-30%Zr master alloys, rare earth magnesium alloys with different components can be obtained. The chemical composition of the rare earth magnesium alloy used in the present invention is: 5.5-8.5% Gd, 2.5-3.5% Y, 0-0.5% Zr, and the balance is Mg.

The beneficial technical effects of the present invention are: adopting the method provided by the present invention, the pores of the sample obtained by die casting are significantly reduced, and the mechanical properties are improved, wherein the room temperature tensile strength of the vacuum die cast sample of the Mg-6Gd-3Y-0.5Zr alloy is , yield strength, and elongation were 249.9MPa, 163.8MPa, and 19.5% respectively; the room temperature tensile strength, yield strength, and elongation of Mg-8Gd-3Y-0.5Zr alloy vacuum die-casting samples were 249.7MPa, 198.9MPa, and 7.61% respectively. %.

Description of drawings

Fig. 1 is the as-cast metallographic diagram of Mg-8Gd-3Y-0.5Zr alloy under the vacuum die-casting condition of embodiment 1;

Fig. 2 is the as-cast metallographic diagram of the Mg-8Gd-3Y-0.5Zr alloy under the normal pressure die-casting method of Example 4.

Detailed ways

The embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings. This embodiment is implemented on the premise of the technical solution of the present invention, and detailed implementation methods and specific operating procedures are provided, but the scope of protection of the present invention is not limited to the following the described embodiment.

Example 1: Mg-8Gd-3Y-0.5Zr alloy 6kPa vacuum die casting

First, preheat 39.56kg of pure magnesium ingot, 4.44kg of Mg-90%Gd master alloy, 6kg of Mg-25%Y master alloy, and 0.5kg of Mg-30%Zr master alloy to 150℃～ ₂₅₀ ℃; Put the pure magnesium ingot into the melting furnace under the protection of the mixed gas of _N2 . After the magnesium ingot is melted, the temperature of the melt is raised to 680℃～700℃; then the preheated Mg-90%Gd and Mg-25% Put the Y intermediate alloy into the melting furnace, and after the melting is complete, raise the temperature to 740°C~760°C; put Mg-30%Zr into the melting furnace, drop the temperature, and wait until the temperature rises to 740°C~760°C again Finally, continue to refine with electricity, stir to make it evenly mixed, let it stand, and then lower the temperature to 680°C, continue to keep warm, and remove the scum on the surface.

Toyo 250-ton cold chamber horizontal die-casting machine is used to die-cast the above molten metal. The specific steps are as follows: preheat the mold to 150°C, add the above-mentioned molten metal at 680°C, and press the punch in at a low speed of 200mm/s; When the head travels to 120mm, the die-casting machine is evacuated to 6kPa, and the punch keeps moving; when the punch travels to 260mm, it starts to press in at a high speed of 4m/s; when the punch travels to 280mm, the boost pressure is set to 12MPa, the die-casting is completed, and the metal is taken out after cooling.

Composition analysis of the above rare earth magnesium alloy shows that it contains Gd7.97%, Y2.56%, Zr0.29%, and the rest is Mg. The above-mentioned rare earth magnesium alloy was tested for mechanical properties, and the test results were as follows: the tensile strength was 249.7 MPa; the yield strength was 198.9 MPa; and the elongation was 7.61%. Figure 1 is the as-cast metallographic diagram of the alloy obtained in this embodiment. It can be seen from the figure that under the vacuum die-casting method, the pores and shrinkage pores in the casting are significantly reduced.

Example 2: Mg-8Gd-3Y-0.5Zr alloy 10kPa vacuum die casting

First, preheat 39.56kg of pure magnesium ingot, 4.44kg of Mg-90%Gd master alloy, 6kg of Mg-25%Y master alloy, and 0.5kg of Mg-30%Zr master alloy to 150℃～ ₂₅₀ ℃; Put the pure magnesium ingot into the melting furnace under the protection of the mixed gas of _N2 . After the magnesium ingot is melted, the temperature of the melt is raised to 680℃～700℃; then the preheated Mg-90%Gd and Mg-25% Put the Y intermediate alloy into the melting furnace, and after the melting is complete, raise the temperature to 740°C~760°C; put Mg-30%Zr into the melting furnace, drop the temperature, and wait until the temperature rises to 740°C~760°C again Finally, continue to refine with electricity, stir to make it evenly mixed, let it stand, and then cool down to 700°C, continue to keep warm, and remove the scum on the surface.

Toyo 250-ton cold chamber horizontal die-casting machine is used to die-cast the above molten metal. The specific steps are as follows: preheat the mold to 150°C, add the above-mentioned molten metal at 700°C, and press the punch in at a low speed of 300mm/s; When the head travels to 120mm, the die-casting machine is vacuumed to 10kPa, and the punch keeps moving; when the punch travels to 255mm, it starts to press in at a high speed of 6m/s; when the punch travels to 290mm, the boost pressure is set to 13MPa, the die-casting is completed, and the metal is taken out after cooling.

Composition analysis of the above rare earth magnesium alloy shows that it contains Gd7.97%, Y2.56%, Zr0.29%, and the rest is Mg. The above-mentioned rare earth magnesium alloy was tested for mechanical properties, and the test results were as follows: the tensile strength was 240.4 MPa; the yield strength was 197.6 MPa; and the elongation was 7.58%.

Example 3: Mg-8Gd-3Y-0.5Zr alloy 15kPa vacuum die casting

First, preheat 39.56kg of pure magnesium ingot, 4.44kg of Mg-90%Gd master alloy, 6kg of Mg-25%Y master alloy, and 0.5kg of Mg-30%Zr master alloy to 150℃～ ₂₅₀ ℃; Put the pure magnesium ingot into the melting furnace under the protection of the mixed gas of _N2 . After the magnesium ingot is melted, the temperature of the melt is raised to 680℃～700℃; then the preheated Mg-90%Gd and Mg-25% Put the Y intermediate alloy into the melting furnace, and after the melting is complete, raise the temperature to 740°C~760°C; put Mg-30%Zr into the melting furnace, drop the temperature, and wait until the temperature rises to 740°C~760°C again Finally, uninterrupted electricity for refining, stirring to make it evenly mixed, standing still, then cooling down to 720°C, continuing to keep warm, and removing the scum on the surface.

Toyo 250-ton cold chamber horizontal die-casting machine is used to die-cast the above molten metal. The specific steps are as follows: preheat the mold to 180°C, add the above-mentioned molten metal at 720°C, and press the punch in at a low speed of 300mm/s; When the head travels to 120mm, the die-casting machine is evacuated to 15kPa, and the punch keeps moving; when the punch travels to 255mm, it starts to press in at a high speed of 6m/s; when the punch travels to 290mm, the boost pressure is set to 13MPa, the die-casting is completed, and the metal is taken out after cooling.

Composition analysis of the above rare earth magnesium alloy shows that it contains Gd7.97%, Y2.56%, Zr0.29%, and the rest is Mg. The above-mentioned rare earth magnesium alloy was tested for mechanical properties, and the test results were as follows: the tensile strength was 239.1 MPa; the yield strength was 191.1 MPa; and the elongation was 7.14%.

Example 4: Mg-8Gd-3Y-0.5Zr alloy die-casting under normal pressure; this example is a comparative example of Example 1, and the normal pressure is 101.3 kPa at one atmosphere.

First, preheat 39.56kg of pure magnesium ingot, 4.44kg of Mg-90%Gd master alloy, 6kg of Mg-25%Y master alloy, and 0.5kg of Mg-30%Zr master alloy to 150℃～ ₂₅₀ ℃; Put the pure magnesium ingot into the melting furnace under the protection of the mixed gas of _N2 . After the magnesium ingot is melted, the temperature of the melt is raised to 680℃～700℃; then the preheated Mg-90%Gd and Mg-25% Put the Y intermediate alloy into the melting furnace, and after the melting is complete, raise the temperature to 740°C~760°C; put Mg-30%Zr into the melting furnace, drop the temperature, and wait until the temperature rises to 740°C~760°C again Finally, continue to refine with electricity, stir to make it evenly mixed, let it stand, and then lower the temperature to 680°C, continue to keep warm, and remove the scum on the surface.

Toyo 250-ton cold chamber horizontal die-casting machine is used to die-cast the above molten metal. The specific steps are as follows: preheat the mold to 150°C, add the above-mentioned molten metal at 680°C, and press the punch in at a low speed of 200mm/s; When the head travels to 260mm, it starts to press in at a high speed of 4m/s; when the punch travels to 280mm, the boost pressure is set to 12MPa, the die casting is completed, and the metal is taken out after cooling.

Composition analysis of the above rare earth magnesium alloy shows that it contains Gd7.97%, Y2.56%, Zr0.29%, and the rest is Mg. The above-mentioned rare earth magnesium alloy was tested for mechanical properties, and the test results were as follows: the tensile strength was 233.2 MPa; the yield strength was 185.3 MPa; and the elongation was 4.10%. Figure 2 is the as-cast metallographic diagram of the alloy obtained in this embodiment. It can be seen from the figure that compared with the casting obtained by the vacuum die casting method, the air hole and shrinkage cavity in the casting obtained by the normal pressure die casting method are more.

Example 5: Mg-6Gd-3Y-0.5Zr alloy 6kPa vacuum die casting

First, preheat 40.67kg of pure magnesium ingot, 3.33kg of Mg-90%Gd master alloy, 6kg of Mg-25%Y master alloy, and 0.5kg of Mg-30%Zr master alloy to 150℃～ ₂₅₀ ℃; Put the pure magnesium ingot into the melting furnace under the protection of the mixed gas of _N2 . After the magnesium ingot is melted, the temperature of the melt is raised to 680℃～700℃; then the preheated Mg-90%Gd and Mg-25% Put the Y intermediate alloy into the melting furnace, and after the melting is complete, raise the temperature to 740°C~760°C; put Mg-30%Zr into the melting furnace, drop the temperature, and wait until the temperature rises to 740°C~760°C again Finally, continue to refine with electricity, stir to make it evenly mixed, let it stand, and then lower the temperature to 680°C, continue to keep warm, and remove the scum on the surface.

Toyo 250-ton cold chamber horizontal die-casting machine is used to die-cast the above molten metal. The specific steps are as follows: preheat the mold to 150°C, add the above-mentioned molten metal at 680°C, and press the punch in at a low speed of 200mm/s; When the head travels to 120mm, the die-casting machine is evacuated to 6kPa, and the punch keeps moving; when the punch travels to 260mm, it starts to press in at a high speed of 4m/s; when the punch travels to 280mm, the boost pressure is set to 12MPa, the die-casting is completed, and the metal is taken out after cooling.

Composition analysis of the above-mentioned rare earth magnesium alloy shows that it contains Gd6.30%, Y2.57%, Zr0.90%, and the rest is Mg. The above rare earth magnesium alloy was tested for mechanical properties, and the test results were as follows: tensile strength 249.9 MPa; yield strength 163.8 MPa; elongation 19.50%.

Example 6: Mg-6Gd-3Y-0.5Zr alloy 10kPa vacuum die casting

First, preheat 40.67kg of pure magnesium ingot, 3.33kg of Mg-90%Gd master alloy, 6kg of Mg-25%Y master alloy, and 0.5kg of Mg-30%Zr master alloy to 150℃～ ₂₅₀ ℃; Put the pure magnesium ingot into the melting furnace under the protection of the mixed gas of _N2 . After the magnesium ingot is melted, the temperature of the melt is raised to 680℃～700℃; then the preheated Mg-90%Gd and Mg-25% Put the Y intermediate alloy into the melting furnace, and after the melting is complete, raise the temperature to 740°C~760°C; put Mg-30%Zr into the melting furnace, drop the temperature, and wait until the temperature rises to 740°C~760°C again Finally, continue to refine with electricity, stir to make it evenly mixed, let it stand, and then cool down to 700°C, continue to keep warm, and remove the scum on the surface.

Toyo 250-ton cold chamber horizontal die-casting machine is used to die-cast the above molten metal. The specific steps are as follows: preheat the mold to 150°C, add the above-mentioned molten metal at 700°C, and press the punch in at a low speed of 300mm/s; When the head travels to 120mm, the die-casting machine is vacuumed to 10kPa, and the punch keeps moving; when the punch travels to 255mm, it starts to press in at a high speed of 6m/s; when the punch travels to 290mm, the boost pressure is set to 13MPa, the die-casting is completed, and the metal is taken out after cooling.

Composition analysis of the above-mentioned rare earth magnesium alloy shows that it contains Gd6.30%, Y2.57%, Zr0.90%, and the rest is Mg. The above rare earth magnesium alloy was tested for mechanical properties, and the test results were as follows: tensile strength 248.2 MPa; yield strength 161.0 MPa; elongation 17.54%.

Example 7: Mg-6Gd-3Y-0.5Zr alloy 15kPa vacuum die casting

First, preheat 40.67kg of pure magnesium ingot, 3.33kg of Mg-90%Gd master alloy, 6kg of Mg-25%Y master alloy, and 0.5kg of Mg-30%Zr master alloy to 150℃～ ₂₅₀ ℃; Put the pure magnesium ingot into the melting furnace under the protection of the mixed gas of _N2 . After the magnesium ingot is melted, the temperature of the melt is raised to 680℃～700℃; then the preheated Mg-90%Gd and Mg-25% Put the Y intermediate alloy into the melting furnace, and after the melting is complete, raise the temperature to 740°C~760°C; put Mg-30%Zr into the melting furnace, drop the temperature, and wait until the temperature rises to 740°C~760°C again Finally, uninterrupted electricity for refining, stirring to make it evenly mixed, standing still, then cooling down to 720°C, continuing to keep warm, and removing the scum on the surface.

Toyo 250-ton cold chamber horizontal die-casting machine is used to die-cast the above molten metal. The specific steps are as follows: preheat the mold to 180°C, add the above-mentioned molten metal at 720°C, and press the punch in at a low speed of 300mm/s; When the head travels to 120mm, the die-casting machine is evacuated to 15kPa, and the punch keeps moving; when the punch travels to 255mm, it starts to press in at a high speed of 6m/s; when the punch travels to 290mm, the boost pressure is set to 13MPa, the die-casting is completed, and the metal is taken out after cooling.

Composition analysis of the above-mentioned rare earth magnesium alloy shows that it contains Gd6.30%, Y2.57%, Zr0.90%, and the rest is Mg. The above-mentioned rare earth magnesium alloy was tested for mechanical properties, and the test results were as follows: the tensile strength was 228.1 MPa; the yield strength was 159.5 MPa; and the elongation was 12.84%.

Example 8: Die-casting of Mg-6Gd-3Y-0.5Zr alloy at normal pressure; this example is a comparative example of Example 5, and normal pressure refers to one atmospheric pressure, that is, 101.3 kPa.

First, preheat 40.67kg of pure magnesium ingot, 3.33kg of Mg-90%Gd master alloy, 6kg of Mg-25%Y master alloy, and 0.5kg of Mg-30%Zr master alloy to 150℃～ ₂₅₀ ℃; Put the pure magnesium ingot into the melting furnace under the protection of the mixed gas of _N2 . After the magnesium ingot is melted, the temperature of the melt is raised to 680℃～700℃; then the preheated Mg-90%Gd and Mg-25% Put the Y intermediate alloy into the melting furnace, and after the melting is complete, raise the temperature to 740°C~760°C; put Mg-30%Zr into the melting furnace, drop the temperature, and wait until the temperature rises to 740°C~760°C again Finally, continue to refine with electricity, stir to make it evenly mixed, let it stand, and then lower the temperature to 680°C, continue to keep warm, and remove the scum on the surface.

Toyo 250-ton cold chamber horizontal die-casting machine is used to die-cast the above molten metal. The specific steps are as follows: preheat the mold to 150°C, add the above-mentioned molten metal at 680°C, and press the punch in at a low speed of 200mm/s; When the head travels to 255mm, it starts to press in at a high speed of 4m/s; when the punch travels to 290mm, the boost pressure is set to 12MPa, the die casting is completed, and the metal is taken out after cooling.

Composition analysis of the above-mentioned rare earth magnesium alloy shows that it contains Gd6.30%, Y2.57%, Zr0.90%, and the rest is Mg. The above-mentioned rare earth magnesium alloy was tested for mechanical properties, and the test results were as follows: the tensile strength was 221.5 MPa; the yield strength was 158.3 MPa; and the elongation was 7.71%.

The preferred specific embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make many modifications and changes according to the concept of the present invention without creative efforts. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning or limited experiments on the basis of the prior art shall be within the scope of protection defined by the claims.

Claims (4)

1. the evacuated die-casting process method of a magnesium-rare earth is characterized in that, may further comprise the steps:

Step 1, pure magnesium ingot and magnesium-rare earth intermediate alloy mixed melting is formed the magnesium-rare earth molten metal, with described molten metal 680～720 ℃ of insulations;

Step 2, with the die casting in die casting machine of above-mentioned magnesium-rare earth molten metal, the die casting parameter arranges as follows: low speed speed is 0.2～0.3m/s, high speed speed is 4～6m/s, high low speed dislocation is 255～260mm; Vacuumize position 120mm, vacuum is 5～15kPa; Pressurization position is 280～290mm, and boost pressure is 12～13MPa.

2. the evacuated die-casting process method of a kind of magnesium-rare earth described in claim 1 is characterized in that, described die casting machine adopts 250 tons of cold house's horizontal plunger die casting machines of Japan.

3. the evacuated die-casting process method of a kind of magnesium-rare earth described in claim 1 is characterized in that, described magnesium-rare earth molten metal is Mg-8Gd-3Y-0.5Zr or Mg-6Gd-3Y-0.5Zr.

4. the evacuated die-casting process method of a kind of magnesium-rare earth described in claim 1 is characterized in that, whole fusing and press casting procedure, and described magnesium-rare earth molten metal is by SF ₆And N ₂Mixed gas protected.

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