Aluminum alloy for contact network and gravity casting and heat treatment method thereof

Abstract

The present invention relates to an aluminum alloy for contact network and a gravity casting and heat treatment method thereof, comprising smelting aluminum material, wherein the smelting aluminum material comprises: (1) melting aluminum material; (2) refining and deslagging: refining and deslagging once every 2 hours, adding a refining agent and a deslagging agent according to 0.8% to 1.5% of the weight of the aluminum alloy liquid each time, and removing slag from a degassing chamber and a soup outlet at least once every 1 hour, and each refining and deslagging time is 10 to 15 minutes, and the temperature is ≥725°C; (3) modification treatment: adding Sr, Ti and Mg to the aluminum alloy liquid and stirring for 10 to 15 minutes; (4) degassing and refining to obtain a final aluminum liquid; the degassing process parameters are: nitrogen purity 99.999%, graphite rotor speed 400 to 600 r / min, nitrogen pressure 0.4 to 0.6 MPa, nitrogen flow rate 0.6 to 1 m 3 / h. The present invention can completely remove slag and impurity elements in the aluminum liquid to reduce casting defects of parts.

Description

Technical Field

[0001] The invention relates to the field of gravity casting and heat treatment, and in particular to an aluminum alloy for contact network and a gravity casting and heat treatment method thereof. Background Art

[0002] The overhead contact network is a high-voltage transmission line that is erected in a zigzag shape above the rails in an electrified railway and is used by the pantograph to draw current. Therefore, very high requirements are placed on the various properties of the aluminum alloy used for the overhead contact network. During the casting process of existing aluminum alloys, there are no clear regulations or limitations on the various process parameters in the refining and slag removal process, resulting in the inability to completely remove the slag and impurity elements in the aluminum alloy liquid, causing the cast parts to have more casting defects. Summary of the invention

[0003] The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide a gravity casting and heat treatment method of aluminum alloy for contact network, which can completely remove slag and impurity elements in aluminum liquid to reduce casting defects of parts.

[0004] In order to solve the above technical problems, the technical solution of the present invention is: an aluminum alloy for contact network, the mass percentages of its components are respectively:

[0005] Mn≤0.1%; Cu≤0.05%; Zn≤0.07%; Fe≤0.19%; 6.5%≤Si≤7.5%, 0.2%≤Mg≤0.7%; total impurity amount≤1%; the balance is aluminum; among which, single impurity≤0.03%.

[0006] Preferably, the mass percentages of its components are:

[0007] Mn≤0.1%; Cu≤0.03%; Zn≤0.07%; Fe≤0.15%; 6.5%≤Si≤7.5%, 0.2%≤Mg≤0.3%; total impurity amount≤1%; the balance is aluminum; among which, single impurity≤0.03%.

[0008] The present invention also provides a gravity casting and heat treatment method of an aluminum alloy for a contact network, comprising smelting an aluminum material, wherein the smelting aluminum material comprises:

[0009] (1) Melting aluminum material;

[0010] The aluminum material includes A356.2 aluminum ingots and recycled materials, the weight of the A356.2 aluminum ingots is ≥60%, and the recycled materials are the risers and / or shrinkage parts of the parts cast with the final aluminum liquid. The aluminum material must be dry, clean, and free of foreign matter, and mixed or added in layers during charging. The use of recycled materials should comply with the relevant requirements of the "Technical Specifications for the Safe Use of Aluminum Casting Reflux Materials".

[0011] (2) Refining and slag removal: Refining and slag removal is performed once every 2 hours. Refining agent and slag removal agent are added at 0.8% to 1.5% of the weight of the aluminum alloy liquid each time. Slag is removed from the degassing chamber and the soup outlet at least once every hour. The refining and slag removal time for each time is 10 to 15 minutes, and the temperature is ≥ 725°C;

[0012] During refining and slag removal, special tools are required to press the refining agent and slag removal agent into the lower middle part of the aluminum liquid for sufficient stirring. When the weather is humid or the amount of recycled materials is large, the upper limit of the amount of refining agent and slag removal agent should be added. After refining and slag removal, special tools are used to scrape the slag out of the furnace into a special slag bucket.

[0013] When the aluminum liquid temperature is higher than 735℃, it is necessary to stop heating with high fire to slow down the oxidation reaction and reduce the oxide content. When the aluminum liquid temperature is lower than 715℃, it is necessary to heat with high fire to achieve the refining and slag removal effect.

[0014] If there are too few refining agents and slag removal agents, the refining time is too short and the interval time is too long, the slag removal will not be thorough and defects such as slag inclusions will appear. If there are too many, the time is too long and the interval time is too short, the alloy elements will be burned too much, and finally the alloy element content will be too little, reducing the strengthening effect of the alloy and the strength. If the temperature is too high, the casting will be overheated or overburned, the structure will be coarse and the mechanical properties will be reduced. If the temperature is too low, the refining agent and the aluminum alloy liquid will not react fully, the slag removal will not be thorough and the refining agent, a new impurity, will be introduced.

[0015] (3) Modification treatment: Add Sr, Ti and Mg to the aluminum alloy liquid and stir for 10 to 15 minutes;

[0016] The order of adding the three alloy elements is: adding aluminum-strontium alloy rods, aluminum-titanium-boron alloy rods and aluminum-magnesium alloy blocks in sequence. After the alloy elements are added, the aluminum-strontium alloy rods, aluminum-titanium-boron alloy rods and aluminum-magnesium alloy blocks are pressed into the lower part of the aluminum liquid using a tool coated with an oily coating agent and preheated, and are fully stirred.

[0017] After modification, in mass percentage:

[0018] Sr: 0.005%~0.015%;

[0019] Ti: 0.1%~0.20%;

[0020] Mg(AlSi7Mg0.3):0.25%~0.45% or Mg(AlSi7Mg0.6):0.45%~0.75%.

[0021] Preferably,

[0022] Sr: 0.008%~0.015%;

[0023] Ti: 0.12%~0.20%;

[0024] Mg(AlSi7Mg0.3):0.30%~0.45% or Mg(AlSi7Mg0.6):0.55%~0.75%.

[0025] Wherein, Mg(AlSi7Mg0.3) refers to the mass percentage of Mg in the aluminum alloy liquid after being treated in step (3) after Mg is added by adding AlSi7Mg0.3 in step (3);

[0026] Mg(AlSi7Mg0.6) refers to the mass percentage of Mg in the aluminum alloy liquid after being treated in step (3) after Mg is added by adding AlSi7Mg0.6.

[0027] (4) Degassing and refining to obtain the final aluminum liquid; before degassing, a layer of refining agent is evenly covered on the surface of the aluminum alloy liquid in the degassing chamber, and it is properly stirred to isolate the air and prevent the aluminum alloy liquid from oxidation; during the degassing process, it is appropriate for bubbles of soybean size to float evenly on the surface of the aluminum alloy liquid, and the rolling height of the aluminum liquid is less than 15mm; the graphite stirring rod needs to be coated with an oily coating agent before entering the aluminum liquid, and preheated above the furnace degassing chamber for 5 to 10 minutes. At the same time, the operation and wear of the graphite rod need to be frequently observed during the degassing process, and it needs to be replaced in time if the wear is serious; the degassing process parameters are: nitrogen purity 99.999%, graphite rotor speed 400 to 600r / min, nitrogen pressure 0.4 to 0.6Mpa, nitrogen flow rate 0.6 to 1m3 / h.

[0028] During normal operation, check the nitrogen pressure, nitrogen flow and degassing effect every 30 minutes, clean the slag on the surface of the aluminum liquid in the degassing chamber, and then pour a small amount of slag remover and stir it evenly to cover the surface of the aluminum liquid. When abnormal conditions such as nitrogen pressure alarm and equipment shutdown occur, the cause should be investigated and properly handled. The main parameters for stirring are nitrogen purity, pressure, flow, and graphite rod speed. Appropriate pressure, flow and speed can take away impurities such as H in the aluminum liquid. If the above parameters are too high, not only can H not be taken away, but other gases in the air will be introduced, resulting in defects such as pores in the casting production; if the parameter value is too low, it will lead to insufficient grain refinement and hydrogen storage, and there will also be defects in the casting, and the fine grain strengthening effect is not good, and the mechanical properties are reduced. In addition, the purpose of using graphite rods for stirring instead of other tools is not to introduce other impurity elements. The graphite introduced by stirring will float to the surface of the liquid along with the slag and be cleaned up.

[0029] Step (1) is carried out in the dissolving chamber, steps (2) and (3) are carried out in the holding chamber, and step (4) is carried out in the degassing chamber. The temperature of the melting chamber is 900°C ± 20°C, the temperature of the holding chamber is 880°C ± 20°C, and the temperature of the degassing chamber is 725°C ± 10°C. During the smelting process, if an abnormal furnace temperature alarm is found, the cause should be found out in time and handled properly; when the aluminum liquid reaches the maximum capacity, the heating of the material is stopped; when the aluminum liquid temperature exceeds the temperature, high-temperature heating is stopped to prevent overburning of the aluminum liquid alloy elements.

[0030] The composition of the molten aluminum after smelting should meet the provisions and requirements of the chemical composition of aluminum alloy castings in EN 1706-2010, and the aluminum liquid capacity of each furnace should be controlled between 800kg and 1000kg.

[0031] During the smelting process, all tools that come into contact with the aluminum alloy liquid, especially iron utensils, need to be coated with an oily coating agent and preheated to avoid gas explosions that may cause personal injury and equipment damage, and to prevent the aluminum alloy from absorbing too many other elements.

[0032] The above smelting is carried out in a gravity casting continuous melting furnace. If the gravity casting continuous melting furnace is shut down for more than 2 days, it can only be used after being dried for more than 3 days. The drying time is set according to the length of the shutdown time and the air humidity at that time. Generally, the drying cycle is set to 4 to 7 days. After the drying is completed, the furnace temperature must be maintained above 750℃ before it can be used.

[0033] The final aluminum liquid has a hydrogen content of ≤0.2ccm / 100g and a density of ≥2.6g / cm 3 .

[0034] Hydrogen content determination:

[0035] The sampling mold must be fully preheated in advance, painted with special paint, and the cavity must be smooth, clean and free of oil stains.

[0036] The hydrogen content in the final aluminum liquid is tested by a hydrogen meter or by using a density equivalent meter to calculate the density. The sampling frequency is 1 time / 2h, the quantity is 2 pieces, and when the hydrogen content is ≤0.2ccm / 100g, it is judged to be qualified; the final aluminum liquid density calculated by measurement is ≥2.6g / cm 3 , it is judged as qualified.

[0037] When the final hydrogen content in the aluminum liquid is not up to standard, the pouring must be stopped immediately to find out the reasons, such as whether the nitrogen pressure and flow are normal, whether the holes in the graphite rod and the exhaust holes in the graphite rotor are blocked, and whether the equipment is running normally. At the same time, the products of the previous 2 hours must be isolated and can only be circulated after passing the test.

[0038] The final aluminum liquid has a grain refinement factor of ≥6.5 and a modification factor of 4 to 8.

[0039] When the grain refinement factor is lower than 6.5, aluminum strontium and aluminum titanium boron alloy need to be added to re-modify the aluminum alloy liquid. When the modification factor is lower than 4, the modification effect is insufficient, and aluminum strontium and aluminum titanium boron alloy need to be added to re-modify the aluminum liquid; when the modification factor is higher than 8, the modification effect is excessive, and aluminum ingots need to be added to stir and dilute the aluminum liquid.

[0040] Preferably, the gravity casting and heat treatment method of aluminum alloy for contact network further comprises:

[0041] S1, mold preheating: After installation and commissioning, the mold needs to be further preheated before pouring. Use a gas-fired mold baking rack to fully bake and preheat the mold. The flame size must be controlled during preheating to prevent the generation of a large amount of black smoke or damage to the equipment and mold. If the air pipe and joints are leaking or damaged, they should be promptly handled and replaced. The preheating temperature control range is 300℃~450℃, the preheating time is 1h~2h, and the normal working temperature control range is 350℃~500℃;

[0042] S2, casting: using gravity casting method, the final aluminum liquid is cast into the mold by a robot to obtain the required part shape, the casting speed is 6 to 12 seconds, the mold closing time after casting is 120 to 160 seconds, and the mold is naturally cooled after opening;

[0043] S3, solution quenching: heating temperature is 535±5℃, holding time is 12h, quenching transfer time is ≤15s, cooling method is 60~90℃ hot water, and the parts stay in the quenching liquid for ≥2min;

[0044] This step has the following requirements: The solution treatment heating of aluminum alloy parts requires hot furnace loading, and the furnace temperature should not exceed 100℃ / h; when using an elevated resistance furnace for heating, the parts should be placed in a special loading basket to ensure air flow; during the quenching process, the parts are not allowed to be exposed to the quenching liquid surface.

[0045] S4, aging treatment: heating temperature 160±5℃, holding time 5.5~6.5h, cooling method, air cooling to room temperature.

[0046] Before step S1, the method further includes:

[0047] Sand core preparation: Before starting the machine, you need to prepare the corresponding sand core according to the product you are making, and make sure that the sand core can fit well with the mold.

[0048] Mold preparation: To ensure that the coating adheres well to the mold surface, the mold needs to be preheated before spraying the coating. The temperature setting requirement of the electric heating furnace is 420℃±20℃, and the insulation time requirement of the electric heating furnace is 3h~4h; the coating thickness is controlled according to actual needs, but must comply with the principle of sequential solidification. Be careful and pay attention to safety during mold assembly to avoid burns and mold damage.

[0049] Mould installation:

[0050] a. Install the assembled mold on the gravity tilting machine, then adjust the travel limit switch and ensure that the mold opens and closes and all parts operate normally.

[0051] b. Before starting the machine, the moving parts of the gravity tilting machine and the mold should be lubricated and run dry. Production can only begin after confirming that there are no abnormalities.

[0052] c. After the mold is placed on the machine, use special tools to press the wire filter mesh to ensure that the shape and size match the support frame.

[0053] Pouring parameter setting: According to the specifications of the installed mold and the pouring amount of the product, the corresponding program is input and slowly tested to ensure that the pouring process is stable, smooth and accurate.

[0054] After adopting the above technical solution, the present invention has the following beneficial effects:

[0055] 1. The present invention clearly stipulates the amount of refining agent and slag removal agent added, refining time, temperature, and refining and slag removal interval time. This refining and slag removal method can completely remove slag and impurity elements in the aluminum alloy liquid, reducing casting defects of parts;

[0056] 2. During the modification process of the present invention, aluminum strontium alloy rods, aluminum titanium boron alloy rods and aluminum magnesium alloy blocks are added, and the stirring time is strictly controlled, which can ensure sufficient mixing and avoid too long stirring time. Too long stirring time will reduce the effect of the modifier and the alloy grains will grow again. The modification method of the present invention can greatly refine the grains of the aluminum alloy and improve the plasticity, toughness and strength of the parts;

[0057] 3. The stirring process used in the present invention can keep the grain size of the product consistent, the grain size is basically equal, and no long strip grains will appear, ensuring that the material has good properties and ultimately ensuring the uniformity of the performance of the material at all locations;

[0058] 4. The present invention analyzes the hydrogen content separately to ensure that there is no high hydrogen element in the alloy, thus preventing hydrogen embrittlement of parts during service;

[0059] 5. The thermal analysis used in the present invention ensures that all parts have the same grain size and microstructure, further reducing casting defects;.

[0060] 6. In the present invention, during aging treatment, the casting is heated up along with the furnace, thereby reducing the generation of thermal stress.

[0061] 7. In the present invention, the water quenching time after solution treatment is no more than 15 seconds to ensure that the structure after water quenching is a supersaturated solid solution and the material strength will not be reduced. DETAILED DESCRIPTION

[0062] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments.

[0063] Embodiment 1

[0064] An aluminum alloy for contact network, the mass percentages of its components are:

[0065] Mn: 0.1%; Cu: 0.03%; Zn: 0.07%; Fe: 0.19%; Si: 7.5%; Mg: 0.3%; total impurities: 0.8%; the balance is aluminum; among which, a single impurity is ≤0.03%.

[0066] The three impurities are: P≤0.03%, Sb≤0.01%, Pb≤0.02%.

[0067] A gravity casting and heat treatment method for an aluminum alloy for a contact network includes smelting aluminum material, wherein the smelting aluminum material includes:

[0068] (1) Melting aluminum material, with a melting chamber temperature of 900° C., a holding chamber temperature of 890° C., and a degassing chamber temperature of 730° C.; the aluminum material comprises A356.2 aluminum ingots and recycled materials, the weight of the A356.2 aluminum ingots is 60%, the weight of the recycled materials is 40%, and the recycled materials are risers and / or shrinkage parts of parts cast with the final aluminum liquid.

[0069] (2) Refining and slag removal: Refining and slag removal is performed once every 2 hours. Refining agent and slag removal agent are added at 0.8% of the weight of the aluminum alloy liquid each time. Slag is removed from the degassing chamber and the soup outlet once every hour. The refining and slag removal time is 10 to 15 minutes each time, and the temperature is ≥725°C;

[0070] (3) Modification treatment: add aluminum-strontium alloy rods, aluminum-titanium-boron alloy rods and aluminum-magnesium alloy blocks in sequence, and then press the aluminum-strontium alloy rods, aluminum-titanium-boron alloy rods and aluminum-magnesium alloy blocks into the lower part of the aluminum liquid through a tool coated with an oily coating agent and preheated, and stir for 10 to 15 minutes;

[0071] In the aluminum alloy liquid after the treatment in step (3), in terms of mass percentage:

[0072] Sr: 0.005%;

[0073] Ti: 0.1%;

[0074] Mg(AlSi7Mg0.3):0.25%.

[0075] (4) Degassing and refining to obtain the final aluminum liquid; before degassing, a layer of refining agent is evenly covered on the surface of the aluminum alloy liquid in the degassing chamber and stirred; the degassing process parameters are: nitrogen purity 99.999%, graphite rotor speed 400r / min, nitrogen pressure 0.5Mpa, nitrogen flow rate 0.8m 3 / h.

[0076] The final aluminum liquid has a hydrogen content of 0.15ccm / 100g and a density of ≥2.6g / cm 3 .

[0077] According to the "Specifications for Grain Size Inspection of Aluminum-Silicon-Magnesium Alloys", the final aluminum liquid was subjected to thermal analysis. The ambient temperature control range of the thermal analyzer was 25°C±5°C. The temperature of the final aluminum liquid was ≥680°C, the grain refinement factor was 7, and the metamorphism factor was 5.

[0078] Wherein, step (1) is carried out in a dissolving chamber, steps (2) and (3) are carried out in a holding chamber, and step (4) is carried out in a degassing chamber. The temperature of the melting chamber is 900°C, the temperature of the holding chamber is 890°C, and the temperature of the degassing chamber is 730°C.

[0079] The gravity casting and heat treatment method of the aluminum alloy for contact network in this embodiment also includes:

[0080] S1, mold preheating: preheating temperature control range is 300℃, preheating time is 1h, normal working temperature control range is 400℃;

[0081] S2, casting: using gravity casting method to cast the final aluminum liquid into the mold to obtain the required part shape, the casting speed is 8s, the mold closing time after casting is 130s, and the mold is naturally cooled after opening;

[0082] S3, solution quenching: heating temperature is 535℃, holding time is 12h, quenching transfer time is ≤15s, cooling method is 70℃ hot water, and the part stays in the quenching liquid for ≥2min;

[0083] S4, aging treatment: heating temperature 160℃, holding time 6.5h, cooling method, air cooling to room temperature.

[0084] The inspection items of cast parts are carried out according to the standard GB / T9438, and the inspection results are:

[0085] X-ray flaw detector looseness and shrinkage defect level ≤ level 2;

[0086] X-ray flaw detector slag eye and pore defect level ≤ level 2;

[0087] The casting will not crack;

[0088] No orange peel-like floral flow marks appear on the non-machined surface;

[0089] The tensile strength is measured according to the standard GB / T1173, and the tensile strength is:

[0090] The tensile strength exceeds 225MPa and the elongation exceeds 1%.

[0091] Embodiment 2

[0092] An aluminum alloy for contact network, the mass percentages of its components are:

[0093] Mn: 0.1%; Cu: 0.03%; Zn: 0.07%; Fe: 0.19%; Si: 7.5%; Mg: 0.6%; Total impurities: 0.8%; The balance is aluminum; Among them, a single impurity ≤ 0.03%;

[0094] The three impurities are: P≤0.03%, Sb≤0.01%, Pb≤0.02%.

[0095] A gravity casting and heat treatment method for an aluminum alloy for a contact network includes smelting aluminum material, wherein the smelting aluminum material includes:

[0096] (1) Melting aluminum material; the aluminum material includes A356.2 aluminum ingots and recycled materials, the weight of the A356.2 aluminum ingots is 60%, the weight of the recycled materials is 40%, and the recycled materials are risers and / or shrinkage parts of parts cast with the final aluminum liquid.

[0097] (2) Refining and slag removal: Refining and slag removal is performed once every 2 hours. Refining agent and slag removal agent are added at 0.8% of the weight of the aluminum alloy liquid each time. Slag is removed from the degassing chamber and the soup outlet once every hour. The refining and slag removal time is 10-15 minutes each time, and the temperature is ≥725°C;

[0098] (3) Modification treatment: add aluminum-strontium alloy rods, aluminum-titanium-boron alloy rods and aluminum-magnesium alloy blocks in sequence, and then press the aluminum-strontium alloy rods, aluminum-titanium-boron alloy rods and aluminum-magnesium alloy blocks into the lower part of the aluminum liquid through a tool coated with an oily coating agent and preheated, and stir for 10 to 15 minutes;

[0099] In the aluminum alloy liquid after the treatment in step (3), in terms of mass percentage:

[0100] Sr: 0.008%;

[0101] Ti: 0.15%;

[0102] Mg(AlSi7Mg0.6):0.55%.

[0103] (4) Degassing and refining to obtain the final aluminum liquid; before degassing, a layer of refining agent is evenly covered on the surface of the aluminum alloy liquid in the degassing chamber and stirred; the degassing process parameters are: nitrogen purity 99.999%, graphite rotor speed 400r / min, nitrogen pressure 0.5Mpa, nitrogen flow rate 0.8m 3 / h.

[0104] The final aluminum liquid has a hydrogen content of 0.15ccm / 100g and a density of ≥2.6g / cm 3 .

[0105] According to the "Specifications for Grain Size Inspection of Aluminum-Silicon-Magnesium Alloys", the final aluminum liquid was subjected to thermal analysis. The ambient temperature control range of the thermal analyzer was 25°C±5°C. The temperature of the final aluminum liquid was ≥680°C, the grain refinement factor was 7, and the metamorphism factor was 5.

[0106] Wherein, step (1) is carried out in a dissolving chamber, steps (2) and (3) are carried out in a holding chamber, and step (4) is carried out in a degassing chamber. The temperature of the melting chamber is 900°C, the temperature of the holding chamber is 890°C, and the temperature of the degassing chamber is 730°C.

[0107] The gravity casting and heat treatment method of the aluminum alloy for contact network in this embodiment also includes:

[0108] S1, mold preheating: preheating temperature control range is 300℃, preheating time is 1h, normal working temperature control range is 400℃;

[0109] S2, casting: using gravity casting method to cast the final aluminum liquid into the mold to obtain the required part shape, the casting speed is 8s, the mold closing time after casting is 130s, and the mold is naturally cooled after opening;

[0110] S3, solution quenching: heating temperature is 535℃, holding time is 12h, quenching transfer time is ≤15s, cooling method is 70℃ hot water, and the parts stay in the quenching liquid for ≥2min;

[0111] S4, aging treatment: heating temperature 160℃, holding time 6.5h, cooling method, air cooling to room temperature.

[0112] The inspection items of cast parts are carried out according to the standard GB / T9438, and the inspection results are:

[0113] X-ray flaw detector looseness and shrinkage defect level ≤ level 2;

[0114] X-ray flaw detector slag eye and pore defect level ≤ level 2;

[0115] The casting will not crack;

[0116] No orange peel-like floral flow marks appear on the non-machined surface;

[0117] The tensile strength is measured according to the standard GB / T1173, and the tensile strength is:

[0118] Tensile strength ≥230MPa, elongation exceeds 1%.

[0119] Embodiment 3

[0120] An aluminum alloy for contact network, the mass percentages of its components are:

[0121] Mn: 0.1%; Cu: 0.03%; Zn: 0.07%; Fe: 0.19%; Si: 7.5%; Mg: 0.6%; Total impurities: 0.8%; The balance is aluminum; Among them, a single impurity ≤ 0.03%;

[0122] The three impurities are: P≤0.03%, Sb≤0.01%, Pb≤0.02%.

[0123] A gravity casting and heat treatment method for an aluminum alloy for a contact network includes smelting aluminum material, wherein the smelting aluminum material includes:

[0124] (1) Melting aluminum material, with a melting chamber temperature of 880° C., a holding chamber temperature of 860° C., and a degassing chamber temperature of 720° C.; the aluminum material comprises A356.2 aluminum ingots and recycled materials, the weight of the A356.2 aluminum ingots is 60%, the weight of the recycled materials is 40%, and the recycled materials are risers and / or shrinkage parts of parts cast with the final aluminum liquid.

[0125] (2) Refining and slag removal: Refining and slag removal is performed once every 2 hours. Refining agent and slag removal agent are added at 0.8% of the weight of the aluminum alloy liquid each time. Slag is removed from the degassing chamber and the soup outlet once every hour. The refining and slag removal time is 10-15 minutes each time, and the temperature is ≥725°C;

[0126] (3) Modification treatment: add aluminum-strontium alloy rods, aluminum-titanium-boron alloy rods and aluminum-magnesium alloy blocks in sequence, and then press the aluminum-strontium alloy rods, aluminum-titanium-boron alloy rods and aluminum-magnesium alloy blocks into the lower part of the aluminum liquid through a tool coated with an oily coating agent and preheated, and stir for 10 to 15 minutes;

[0127] In the aluminum alloy liquid after the treatment in step (3), in terms of mass percentage:

[0128] Sr: 0.010%;

[0129] Ti: 0.18%;

[0130] Mg(AlSi7Mg0.6):0.65%.

[0131] (4) Degassing and refining to obtain the final aluminum liquid; before degassing, a layer of refining agent is evenly covered on the surface of the aluminum alloy liquid in the degassing chamber and stirred; the degassing process parameters are: nitrogen purity 99.999%, graphite rotor speed 400r / min, nitrogen pressure 0.5Mpa, nitrogen flow rate 0.8m 3 / h.

[0132] The final aluminum liquid has a hydrogen content of 0.15ccm / 100g and a density of ≥2.6g / cm 3 .

[0133] According to the "Specifications for Grain Size Inspection of Aluminum-Silicon-Magnesium Alloys", the final aluminum liquid was subjected to thermal analysis. The ambient temperature control range of the thermal analyzer was 25°C±5°C. The temperature of the final aluminum liquid was ≥680°C, the grain refinement factor was 7, and the metamorphism factor was 5.

[0134] Wherein, step (1) is carried out in a dissolving chamber, steps (2) and (3) are carried out in a holding chamber, and step (4) is carried out in a degassing chamber. The temperature of the melting chamber is 880°C, the temperature of the holding chamber is 860°C, and the temperature of the degassing chamber is 720°C.

[0135] The gravity casting and heat treatment method of the aluminum alloy for contact network in this embodiment also includes:

[0136] S1, mold preheating: preheating temperature control range is 300℃, preheating time is 1h, normal working temperature control range is 400℃;

[0137] S2, casting: using gravity casting method to cast the final aluminum liquid into the mold to obtain the required part shape, the casting speed is 8s, the mold closing time after casting is 130s, and the mold is naturally cooled after opening;

[0138] S3, solution quenching: heating temperature is 535℃, holding time is 12h, quenching transfer time is ≤15s, cooling method is 70℃ hot water, and the parts stay in the quenching liquid for ≥2min;

[0139] S4, aging treatment: heating temperature 160℃, holding time 6.5h, cooling method, air cooling to room temperature.

[0140] The inspection items of cast parts are carried out according to the standard GB / T9438, and the inspection results are:

[0141] X-ray flaw detector looseness and shrinkage defect level ≤ level 2;

[0142] X-ray flaw detector slag eye and pore defect level ≤ level 2;

[0143] The casting will not crack;

[0144] No orange peel-like floral flow marks appear on the non-machined surface;

[0145] The tensile strength is measured according to the standard GB / T1173, and the tensile strength is:

[0146] Tensile strength ≥ 230MPa, elongation exceeds 1%;

[0147] Comparative Example 1

[0148] An aluminum alloy for contact network, the mass percentages of its components are:

[0149] Mn: 0.1%; Cu: 0.03%; Zn: 0.07%; Fe: 0.19%; Si: 7.5%; Mg: 0.3%; total impurities: 0.8%; the balance is aluminum; among which, a single impurity is ≤0.03%.

[0150] A gravity casting and heat treatment method for an aluminum alloy for a contact network includes smelting aluminum material, wherein the smelting aluminum material includes:

[0151] (1) Melting aluminum material, with a melting chamber temperature of 900° C., a holding chamber temperature of 890° C., and a degassing chamber temperature of 730° C.; the aluminum material comprises A356.2 aluminum ingots and recycled materials, the weight of the A356.2 aluminum ingots is 60%, the weight of the recycled materials is 40%, and the recycled materials are risers and / or shrinkage parts of parts cast with the final aluminum liquid.

[0152] (2) Refining and slag removal: Refining and slag removal is performed once every 3 hours. Refining agent and slag removal agent are added at 0.6% of the weight of the aluminum alloy liquid each time. Slag is removed from the degassing chamber and the soup outlet once every hour. The refining and slag removal time is 20 minutes each time, and the temperature is ≥725°C;

[0153] (3) Modification treatment: add aluminum-strontium alloy rods, aluminum-titanium-boron alloy rods and aluminum-magnesium alloy blocks in sequence, and then press the aluminum-strontium alloy rods, aluminum-titanium-boron alloy rods and aluminum-magnesium alloy blocks into the lower part of the aluminum liquid through a tool coated with an oily coating agent and preheated, and stir for 10 to 15 minutes;

[0154] In the aluminum alloy liquid after the treatment in step (3), in terms of mass percentage:

[0155] Sr: 0.005%;

[0156] Ti: 0.1%;

[0157] Mg(AlSi7Mg0.3):0.40%.

[0158] (4) Degassing and refining outside the furnace to obtain the final aluminum liquid; before degassing, a layer of refining agent is evenly covered on the surface of the aluminum alloy liquid in the degassing chamber and stirred; the degassing process parameters are: nitrogen purity 99.999%, graphite rotor speed 400r / min, nitrogen pressure 0.5Mpa, nitrogen flow rate 0.8m 3 / h.

[0159] The final aluminum liquid has a hydrogen content of 0.15ccm / 100g and a density of ≥2.6g / cm 3 .

[0160] According to the "Specifications for Grain Size Inspection of Aluminum-Silicon-Magnesium Alloys", the final aluminum liquid was subjected to thermal analysis. The ambient temperature control range of the thermal analyzer was 25°C±5°C. The temperature of the final aluminum liquid was ≥680°C, the grain refinement factor was 7, and the metamorphism factor was 5.

[0161] The gravity casting and heat treatment method of the aluminum alloy for contact network in this embodiment also includes:

[0162] S1, mold preheating: preheating temperature control range is 300℃, preheating time is 1h, normal working temperature control range is 400℃;

[0163] S2, casting: using gravity casting method to cast the final aluminum liquid into the mold to obtain the required part shape, the casting speed is 8s, the mold closing time after casting is 130s, and the mold is naturally cooled after opening;

[0164] S3, solution quenching: heating temperature is 535℃, holding time is 12h, quenching transfer time is ≤15s, cooling method is 70℃ hot water, and the part stays in the quenching liquid for ≥2min;

[0165] S4, aging treatment: heating temperature 160℃, holding time 6.5h, cooling method, air cooling to room temperature.

[0166] The inspection items of cast parts are carried out according to the standard GB / T9438, and the inspection results are:

[0167] X-ray flaw detector looseness and shrinkage defect level ≤ level 2;

[0168] There are many defects such as slag eyes and pores in the X-ray flaw detector, and the defect level does not reach level 2;

[0169] The casting will not crack;

[0170] No orange peel-like floral flow marks appear on the non-machined surface;

[0171] The tensile strength is measured according to the standard GB / T1173, and the tensile strength is:

[0172] The tensile strength is less than 200MPa.

[0173] In this comparative example, because the refining and slag removal interval is relatively long, the amount of refining agent and slag removal added is relatively small, and the refining and slag removal time is relatively long, resulting in incomplete removal of slag and impurity elements and more part defects.

[0174] Comparative Example 2

[0175] An aluminum alloy for contact network, the mass percentages of its components are:

[0176] Mn: 0.1%; Cu: 0.03%; Zn: 0.07%; Fe: 0.19%; Si: 7.5%; Mg: 0.3%; total impurities: 0.8%; the balance is aluminum; among which, a single impurity is ≤0.03%.

[0177] A gravity casting and heat treatment method for an aluminum alloy for a contact network includes smelting aluminum material, wherein the smelting aluminum material includes:

[0178] (1) Melting aluminum material, with a melting chamber temperature of 900° C., a holding chamber temperature of 890° C., and a degassing chamber temperature of 730° C.; the aluminum material comprises A356.2 aluminum ingots and recycled materials, the weight of the A356.2 aluminum ingots is 60%, the weight of the recycled materials is 40%, and the recycled materials are risers and / or shrinkage parts of parts cast with the final aluminum liquid.

[0179] (2) Refining and slag removal in the furnace: Refining and slag removal is performed once every 2 hours. Refining agent and slag removal agent are added at 0.8% of the weight of the aluminum alloy liquid each time. Slag is removed from the degassing chamber and the soup outlet once every hour. The refining and slag removal time for each time is 10-15 minutes, and the temperature is ≥725°C;

[0180] (3) Modification treatment: Add aluminum-titanium-boron alloy rods and aluminum-magnesium alloy blocks, and then press the aluminum-titanium-boron alloy rods and aluminum-magnesium alloy blocks into the lower part of the aluminum liquid through a tool coated with an oily coating agent and preheated, and stir for 10 to 15 minutes;

[0181] In the aluminum alloy liquid after the treatment in step (3), in terms of mass percentage:

[0182] Ti: 0.1%;

[0183] Mg(AlSi7Mg0.3):0.25%.

[0184] (4) Degassing and refining outside the furnace to obtain the final aluminum liquid; before degassing, a layer of refining agent is evenly covered on the surface of the aluminum alloy liquid in the degassing chamber and stirred; the degassing process parameters are: nitrogen purity 99.999%, graphite rotor speed 400r / min, nitrogen pressure 0.5Mpa, nitrogen flow rate 0.8m 3 / h.

[0185] The final aluminum liquid has a hydrogen content of 0.15ccm / 100g and a density of ≥2.6g / cm 3 .

[0186] According to the "Specifications for Grain Size Inspection of Aluminum-Silicon-Magnesium Alloys", a thermal analysis is performed on the final aluminum liquid. The ambient temperature control range of the thermal analyzer is 25°C±5°C. The temperature of the final aluminum liquid is ≥680°C. The grain refinement factor is less than level 6, and the metamorphism factor is 3 or 4.

[0187] The gravity casting and heat treatment method of the aluminum alloy for contact network in this embodiment also includes:

[0188] S1, mold preheating: preheating temperature control range is 300℃, preheating time is 1h, normal working temperature control range is 400℃;

[0189] S2, casting: using gravity casting method to cast the final aluminum liquid into the mold to obtain the required part shape, the casting speed is 8s, the mold closing time after casting is 130s, and the mold is naturally cooled after opening;

[0190] S3, solution quenching: heating temperature is 535℃, holding time is 12h, quenching transfer time is ≤15s, cooling method is 70℃ hot water, and the part stays in the quenching liquid for ≥2min;

[0191] S4, aging treatment: heating temperature 160℃, holding time 6.5h, cooling method, air cooling to room temperature.

[0192] The inspection items of cast parts are carried out according to the standard GB / T9438, and the inspection results are:

[0193] X-ray flaw detector looseness and shrinkage defect level ≤ level 2;

[0194] X-ray flaw detector slag eye and pore defect level ≤ level 2;

[0195] The casting will not crack;

[0196] The tensile strength is measured according to the standard GB / T1173, and the tensile strength is:

[0197] The tensile strength is about 180MPa.

[0198] In this embodiment, no aluminum-strontium master alloy is added during the modification process, resulting in insufficient modification of the alloy, coarse grains, and low tensile strength.

[0199] Based on the above ideal embodiments of the present invention, the relevant staff can make various changes and modifications without departing from the technical concept of the present invention through the above description. The technical scope of the present invention is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A gravity casting and heat treatment method of aluminum alloy for contact network, characterized in that , The invention comprises a smelting aluminum material, wherein the smelting aluminum material comprises: (1) Melting aluminum material; (2) Refining and slag removal: Refining and slag removal is performed once every 2 hours. Refining agent and slag removal agent are added at 0.8% to 1.5% of the weight of the aluminum alloy liquid each time. Slag is removed from the degassing chamber and the soup outlet at least once every hour. The refining and slag removal time for each time is 10 to 15 minutes, and the temperature is ≥ 725°C; (3) Modification treatment: Add Sr, Ti and Mg to the aluminum alloy liquid and stir for 10 to 15 minutes; (4) degassing and refining to obtain the final aluminum liquid; before degassing, a layer of refining agent is evenly covered on the surface of the aluminum alloy liquid in the degassing chamber and stirred; the degassing process parameters are: nitrogen purity 99.999%, graphite rotor speed 400-600r / min, nitrogen pressure 0.4-0.6Mpa, nitrogen flow rate 0.6-1m 3 / h; Wherein, step (1) is carried out in a dissolving chamber, steps (2) and (3) are carried out in a holding chamber, and step (4) is carried out in a degassing chamber. The temperature of the melting chamber is 900°C ± 20°C, the temperature of the holding chamber is 880°C ± 20°C, and the temperature of the degassing chamber is 725°C ± 10°C. In step (3), the modification treatment comprises: An aluminum-strontium alloy rod, an aluminum-titanium-boron alloy rod and an aluminum-magnesium alloy block are added in sequence, and then the aluminum-strontium alloy rod, the aluminum-titanium-boron alloy rod and the aluminum-magnesium alloy block are pressed into the lower part of the aluminum liquid through a tool coated with an oily coating agent and preheated, and are fully stirred; In the aluminum alloy liquid after the treatment in step (3), in terms of mass percentage: Sr：0.005％～0.015％； Ti: 0.1%~0.20%; Mg (AlSi7Mg0.3): 0.25% to 0.45% or Mg (AlSi7Mg0.6): 0.45% to 0.75%; Wherein, Mg(AlSi7Mg0.3) refers to the mass percentage of Mg in the aluminum alloy liquid after being treated in step (3) after Mg is added by adding AlSi7Mg0.3 in step (3); Mg(AlSi7Mg0.6) refers to the mass percentage of Mg in the aluminum alloy liquid after the treatment in step (3) after Mg is added by adding AlSi7Mg0.6; The mass percentages of the components of the contact network aluminum alloy obtained after the final aluminum liquid gravity casting and heat treatment are: Mn≤0.1%; Cu≤0.05%; Zn≤0.07%; Fe≤0.19%; 6.5%≤Si≤7.5%; 0.2%≤Mg≤0.7%; total impurity amount≤1%; the balance is aluminum; among which, single impurity≤0.03%.

2. The gravity casting and heat treatment method of aluminum alloy for contact network according to claim 1, characterized in that: The mass percentages of the components of the contact network aluminum alloy obtained after gravity casting and heat treatment of the final aluminum liquid are: Mn≤0.1%; Cu≤0.03%; Zn≤0.07%; Fe≤0.15%; 6.5%≤Si≤7.5%; 0.2%≤Mg≤0.3%; total impurity amount≤1%; the balance is aluminum; among which, single impurity≤0.03%.

3. The gravity casting and heat treatment method of aluminum alloy for contact network according to claim 1, characterized in that , The final aluminum liquid has a hydrogen content of ≤0.2ccm / 100g and a density of ≥2.6g / cm3.

4. The gravity casting and heat treatment method of aluminum alloy for contact network according to claim 1, characterized in that , The final aluminum liquid has a grain refinement factor of ≥6.5 and a modification factor of 4 to 8.

5. The gravity casting and heat treatment method of aluminum alloy for contact network according to claim 1, characterized in that: The aluminum material includes A356.2 aluminum ingots and recycled materials, the weight of the A356.2 aluminum ingots is ≥60%, and the recycled materials are risers and / or shrinkage parts of parts cast with the final aluminum liquid.

6. The gravity casting and heat treatment method of aluminum alloy for contact network according to claim 1, characterized in that , In the aluminum alloy liquid after the treatment in step (3), in terms of mass percentage: Sr：0.008％～0.015％； Ti: 0.12%~0.20%; Mg(AlSi7Mg0.3):0.30%~0.45% or Mg(AlSi7Mg0.6):0.55%~0.75%.

7. The gravity casting and heat treatment method of aluminum alloy for contact network according to claim 1, characterized in that , Also includes: S1, mold preheating: preheating temperature control range is 300℃~450℃, preheating time is 1h~2h, normal working temperature control range is 350℃~500℃; S2, casting: using gravity casting method to cast the final aluminum liquid into the mold to obtain the required part shape, the casting speed is 6 to 12 seconds, the mold closing time after casting is 120 to 160 seconds, and the mold is naturally cooled after opening; S3, solution quenching: heating temperature is 535±5℃, holding time is 12h, quenching transfer time is ≤15s, cooling method is 60~90℃ hot water, and the parts stay in the quenching liquid for ≥2min; S4, aging treatment: heating temperature 160±5℃, holding time 5.5~6.5h, cooling method, air cooling to room temperature.