Casting negative pressure casting method based on multi-stage negative pressure control and temperature control

Abstract

The invention discloses a casting negative pressure casting method based on multi-stage negative pressure control and temperature control, which comprises the following steps: S1, in an initial negative pressure stage, before molten metal starts to be poured into a mold, negative pressure is applied, and the negative pressure value is 0.02-0.1 MPA; s2, in a transition negative pressure stage, the negative pressure is adjusted to 0.1 MPA to 0.3 MPA; s3, in the later negative pressure stage, when the casting is about to be solidified, the negative pressure is adjusted to 0.3 MPA to 0.5 MPA; s4, in the whole casting process, the mold is filled with inert gas; s5, after the casting is poured, the temperature of the casting is gradually reduced through a cooling system; and S6, after the casting is completely solidified, the casting is separated from the mold through a pneumatic device. According to the negative pressure casting method for the casting, the overall quality of the casting can be remarkably improved, defects are reduced, the mechanical property and size precision of the casting are improved, and the high application value is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of casting, and in particular relates to a casting negative pressure casting method based on multi-stage negative pressure control and temperature control. Background Art

[0002] With the development of the modern foundry industry, the quality requirements for castings are increasing, especially in precision castings, lightweight castings and high-strength material castings. Although traditional casting processes such as gravity casting and low-pressure casting can meet basic needs in many application scenarios, they have certain shortcomings in casting quality, production efficiency and environmental protection. In particular, casting defects such as pores, cracks, shrinkage cavities, etc. often occur, affecting the mechanical properties, surface quality and service life of castings.

[0003] As an effective casting method, negative pressure casting technology has been widely used in the casting process of various metals such as aluminum alloys, steel, and cast iron. Negative pressure casting can promote the fluidity of molten metal by reducing the pressure in the mold and effectively reduce the formation of bubbles, thereby increasing the density and strength of the casting and improving the surface quality of the casting. The traditional negative pressure casting process is generally operated by a constant negative pressure, but due to the complexity of the flow and solidification of molten metal during the casting process, the adjustment of a single negative pressure often cannot meet the needs of different stages, resulting in limited quality of the casting.

[0004] In addition, temperature control also plays a vital role in the casting process. Too fast or too slow cooling rates may cause deformation or defects in the casting, so temperature control management after casting is particularly important. However, most existing temperature control technologies rely on a single adjustment of the cooling system, which cannot effectively match the changes in the negative pressure casting process, affecting the final quality of the casting.

[0005] Therefore, there is an urgent need for an innovative casting method that can optimize negative pressure and temperature control and improve casting quality in order to meet increasingly stringent casting standards and market demands. Summary of the invention

[0006] To solve the above problems, the present invention provides a negative pressure casting method for castings based on multi-stage negative pressure control and temperature control, which can significantly improve the overall quality of castings, reduce the occurrence of defects, and improve the mechanical properties and dimensional accuracy of castings, and has high application value.

[0007] The technical solution provided by the present invention is as follows:

[0008] A casting negative pressure casting method based on multi-stage negative pressure control and temperature control comprises the following steps:

[0009] S1: Initial negative pressure stage, before the molten metal begins to pour into the mold, negative pressure is applied, and the negative pressure value is 0.02-0.1MPA;

[0010] S2: Transitional negative pressure stage, the negative pressure is adjusted to 0.1-0.3 MPA;

[0011] S3: Late negative pressure stage, when the casting is about to solidify, the negative pressure is adjusted to 0.3–0.5 MPA;

[0012] S4: During the entire casting process, the mold is filled with inert gas;

[0013] S5: After the casting is poured, the temperature of the casting is gradually reduced using a cooling system;

[0014] S6: After the casting is completely solidified, the casting is ejected from the mold using a pneumatic device.

[0015] In some embodiments, the transition negative pressure stage lasts from the time when the molten metal starts to flow into the mold to the time when the molten metal fills 80% of the cavity.

[0016] In some embodiments, the time of the three stages of the multi-stage negative pressure control is:

[0017] Initial negative pressure stage: duration is 3-5 minutes;

[0018] Transitional negative pressure stage: duration is 5-10 minutes;

[0019] Late negative pressure stage: duration is 10-15 minutes.

[0020] In some embodiments, before casting, the molten metal is preheated to a temperature in the range of 700-720°C, and the mold surface temperature is 300-350°C.

[0021] In some embodiments, the inert gas is nitrogen or argon.

[0022] In some embodiments, the inert gas pressure is 0.2-0.5 MPa.

[0023] In some embodiments, the cooling system has a cooling rate controlled at 10-30° C. / min.

[0024] In summary, the beneficial effects of the present invention are:

[0025] First, multi-stage negative pressure control technology is used to adjust the negative pressure value at different casting stages to meet the flow requirements of the molten metal at different stages. A lower negative pressure is used in the initial stage to effectively remove the air in the mold and reduce the generation of pores and cracks; the negative pressure is increased in the transition stage to promote the metal liquid to evenly fill the cavity and further avoid the appearance of voids inside the casting; when the casting is about to solidify, the negative pressure is adjusted to a suitable value to control the solidification speed of the casting and avoid stress concentration and deformation during the cooling process. This multi-stage negative pressure control can effectively improve the internal quality and surface finish of the casting.

[0026] Secondly, the present invention also adds the filling of inert gas during the entire casting process, which effectively prevents the reaction between the molten metal and oxygen in the air, reduces the generation of oxides, and ensures the purity and mechanical properties of the casting. The introduction of inert gas not only optimizes the quality of the casting, but also improves the stability of production.

[0027] In addition, in terms of temperature control, precise control of the cooling rate is adopted to make the cooling process of the casting smooth and uniform, avoiding the problems of casting cracks and deformation caused by too fast cooling. Through reasonable temperature control management, the hardness, strength and toughness of the casting are effectively guaranteed. DETAILED DESCRIPTION

[0028] In order to deepen the understanding of the present invention, the present invention will be further described in detail below in conjunction with examples. The following examples are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0029] The present invention provides a casting negative pressure casting method based on multi-stage negative pressure control and temperature control, aiming to ensure the quality and production efficiency of the casting through multi-stage negative pressure regulation and temperature control management. The following is a specific implementation method of the method.

[0030] During the casting process, the first stage is the initial negative pressure stage. Before the molten metal begins to pour into the mold, the initial negative pressure is applied by the negative pressure pump system, and the negative pressure value is set to 0.02-0.1MPa. This stage lasts for 3-5 minutes, and the purpose is to ensure that the air in the mold is fully removed to avoid pores or defects in the casting during the subsequent pouring process. Through the treatment of the initial negative pressure stage, the impact of gas on the casting structure can be effectively reduced, ensuring that the molten metal flows smoothly into the mold.

[0031] When entering the transition negative pressure stage, the molten metal begins to flow into the mold and fills 80% of the cavity. At this time, the negative pressure value is adjusted to 0.1-0.3MPa and lasts for 5-10 minutes. The main function of this stage is to further promote the molten metal to evenly fill the entire mold cavity, remove excess air and bubbles, and prevent cavities or shrinkage holes from appearing inside the casting. In this way, the casting can obtain better internal density and surface finish, ensuring the quality of the finished product.

[0032] When the casting is about to solidify, it enters the late negative pressure stage, at which the negative pressure value is adjusted to 0.3-0.5MPa and lasts for 10-15 minutes. After the metal solidifies, a certain negative pressure is maintained to ensure the density and strength of the casting. The purpose of this stage is to ensure that the molten metal during the cooling process of the casting has no pores and avoid casting defects, and to ensure that there are no obvious defects or cracks on the surface of the casting. In addition, at this stage, negative pressure control plays a key role in the final shape of the casting, helping it maintain its intact structure.

[0033] During the entire casting process, inert gas, such as nitrogen or argon, is filled into the mold. The main function of the inert gas is to prevent the molten metal from reacting with oxygen in the air, avoid the production of oxides, maintain the purity of the molten metal, and improve the quality of the casting. The pressure of the inert gas is set to 0.2-0.5MPa. The steady inflow of gas can effectively reduce oxidation and bubble generation, and improve the surface quality and mechanical properties of the casting.

[0034] After the casting is poured, the cooling system is used to gradually reduce the temperature of the casting. The cooling rate is controlled between 10-30℃ / min to ensure a smooth temperature change during the cooling process of the casting and avoid cracks or deformation of the casting due to too fast or too slow cooling. The cooling process has a crucial impact on the mechanical properties, dimensional accuracy and appearance quality of the casting.

[0035] Finally, after the casting is completely solidified, a pneumatic device is used to remove the casting from the mold. The pneumatic device can precisely control the air pressure to prevent the casting from being damaged during demolding and maintain its original shape and size. The use of a pneumatic demolding system reduces manual operation errors and improves the efficiency and accuracy of the demolding process.

[0036] In order to ensure the smooth progress of the casting process, the molten metal needs to be preheated before casting, and the temperature of the molten metal is controlled between 700-720℃, and the surface temperature of the mold is controlled between 300-350℃. This temperature range helps to improve the fluidity and mold filling capacity of the molten metal, and avoids pouring difficulties or casting quality problems caused by too low temperature.

[0037] Through the above steps, the method of the present invention can effectively improve the production efficiency of castings, reduce defects such as pores, cracks, bubbles, etc. during the casting process, and ensure the high quality and high precision of castings. The method is not only applicable to the production of various types of castings, but also can ensure the performance and appearance of castings while improving production efficiency, and has broad application prospects.

[0038] The following are three embodiments of the negative pressure casting method of the present invention. Each embodiment uses different parameters and conditions to demonstrate the application effect of the method of the present invention in different casting scenarios, and reflects the advantages of the method through relevant test data.

[0039] Example 1

[0040] Casting of aluminum alloy castings:

[0041] Process parameters

[0042] Initial negative pressure stage: negative pressure 0.03MPa, time 5 minutes;

[0043] Transitional negative pressure stage: negative pressure 0.15MPa, time 7 minutes;

[0044] Late negative pressure stage: negative pressure 0.4MPa, time 12 minutes;

[0045] Inert gas: nitrogen, gas pressure 0.3Mpa;

[0046] Cooling rate: 15℃ / min;

[0047] Metal liquid preheating temperature: 710℃;

[0048] Mould surface temperature: 320℃.

[0049] Test data:

[0050] Casting surface finish: There are no obvious pores, cracks or other defects on the surface, and the Ra value is 1.6μm.

[0051] Internal defect detection: Through X-ray detection, there are no obvious pores, voids or shrinkage holes in the casting, and the density reaches 2.72g / cm 3 , meeting the standard density requirements of aluminum alloy.

[0052] Tensile strength: The tensile strength of the casting is 250MPa, which meets the mechanical property requirements of aluminum alloy castings.

[0053] Dimension accuracy: The casting size deviation is less than ±0.2mm.

[0054] By using the method of the present invention, the surface quality of aluminum alloy castings is significantly improved, internal defects are effectively avoided, the tensile strength of the castings meets industrial standards, the dimensional accuracy is excellent, and the production efficiency is improved by 15%. This example fully demonstrates the advantages of the method of the present invention in reducing defects and improving quality in the production of aluminum alloy castings.

[0055] Example 2

[0056] Casting of steel castings:

[0057] Process parameters

[0058] Initial negative pressure stage: negative pressure 0.05MPa, time 4 minutes;

[0059] Transitional negative pressure stage: negative pressure 0.2MPa, time 6 minutes;

[0060] Late negative pressure stage: negative pressure 0.35MPa, time 10 minutes;

[0061] Inert gas: argon, gas pressure 0.4Mpa;

[0062] Cooling rate: 20℃ / min;

[0063] Metal preheating temperature: 715°C

[0064] Mould surface temperature: 330℃.

[0065] Test data:

[0066] Casting surface quality: no pores, cracks and delamination on the surface, and the surface roughness Ra value is 2.0μm.

[0067] Internal defects: Through ultrasonic testing, there are no bubbles, shrinkage holes and inclusions inside the casting, and the density is 7.80g / cm 3 , meeting the standard density requirements for steel castings.

[0068] Fracture toughness: casting fracture toughness is 50J / cm 2 , meeting the standard requirements of steel castings.

[0069] Dimensional accuracy: The dimensional deviation of the casting is within ±0.3mm.

[0070] The method of the present invention effectively avoids common defects in steel castings, such as pores and shrinkage cavities, through negative pressure regulation and inert gas protection, and the surface quality of the castings is high, meeting the mechanical property requirements of high-performance steel castings. The control of the cooling rate helps to improve the toughness of the castings, while the dimensional accuracy is also significantly improved, and the production cycle is shortened by 20% compared with the traditional method.

[0071] Example 3

[0072] Casting of cast iron castings:

[0073] Process parameters

[0074] Initial negative pressure stage: negative pressure 0.02MPa, time 3 minutes;

[0075] Transitional negative pressure stage: negative pressure 0.1MPa, time 8 minutes;

[0076] Late negative pressure stage: negative pressure 0.3MPa, time 14 minutes;

[0077] Inert gas: nitrogen, gas pressure 0.25Mpa;

[0078] Cooling rate: 10℃ / min;

[0079] Metal liquid preheating temperature: 700℃;

[0080] Mould surface temperature: 340℃.

[0081] Test data:

[0082] Casting surface quality: no obvious cracks or pores on the surface, Ra value is 1.5μm.

[0083] Internal defects: X-ray inspection shows that there are no bubbles, shrinkage holes or cracks inside the casting, and the density is 7.2g / cm 3 , in line with cast iron standards.

[0084] Hardness: The hardness of the casting is 180HB, which meets the mechanical property requirements of cast iron.

[0085] Dimension accuracy: The casting size deviation is ±0.15mm.

[0086] The method of the present invention has shown significant advantages in the production of cast iron castings. By adopting negative pressure control and inert gas protection, common defects on the surface and inside of cast iron castings, especially pores and cracks, are avoided, and the surface finish is high. The hardness and density of the castings meet industrial standards, and the dimensional accuracy is effectively controlled. Compared with the traditional casting process, the production efficiency of the castings is improved by 18%.

[0087] It can be seen from the above three embodiments that the negative pressure casting method for castings based on multi-stage negative pressure control and temperature control can significantly improve the surface quality of castings, reduce internal defects, improve mechanical properties, and effectively control the dimensional accuracy of castings. Different metal materials (such as aluminum alloy, steel, cast iron) all show relatively excellent casting quality under this method. Specific advantages include: improved surface finish of castings, reduced pores and defects, enhanced mechanical properties, and improved production efficiency. This method has wide applicability and significant advantages for the production of various castings.

[0088] It should be noted that in the main text of the specification, the implementation methods not shown or described are all forms known to ordinary technicians in the relevant technical field and are not described in detail. In addition, the above definitions of each element and method are not limited to the various specific structures, shapes or methods mentioned in the embodiments.

[0090] The above description shows and describes the preferred embodiments of the present invention. As mentioned above, it should be understood that the present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the invention concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art do not depart from the spirit and scope of the present invention, and should be within the scope of protection of the claims attached to the present invention.

Claims

1. A casting negative pressure casting method based on multi-stage negative pressure control and temperature control, characterized in that: The following steps are involved: S1: Initial negative pressure stage, before the molten metal begins to pour into the mold, negative pressure is applied, and the negative pressure value is 0.02-0.1MPA; S2: Transitional negative pressure stage, the negative pressure is adjusted to 0.1-0.3 MPA; S3: Late negative pressure stage, when the casting is about to solidify, the negative pressure is adjusted to 0.3–0.5 MPA; S4: During the entire casting process, the mold is filled with inert gas; S5: After the casting is poured, the temperature of the casting is gradually reduced using a cooling system; S6: After the casting is completely solidified, the casting is ejected from the mold using a pneumatic device.

2. The casting negative pressure casting method based on multi-stage negative pressure control and temperature control according to claim 1 is characterized in that: The transition negative pressure stage lasts from the time when the molten metal starts to flow into the mold to the time when the molten metal fills 80% of the cavity.

3. The casting negative pressure casting method based on multi-stage negative pressure control and temperature control according to claim 1, characterized in that: The time of the three stages of the multi-stage negative pressure control is respectively: Initial negative pressure stage: duration is 3-5 minutes; Transitional negative pressure stage: duration is 5-10 minutes; Late negative pressure stage: duration is 10-15 minutes.

4. The casting negative pressure casting method based on multi-stage negative pressure control and temperature control according to claim 1, characterized in that: Before casting, the molten metal is preheated to a temperature range of 700-720°C and the mold surface temperature is 300-350°C.

5. The casting negative pressure casting method based on multi-stage negative pressure control and temperature control according to claim 1, characterized in that: The inert gas is nitrogen or argon.

6. The casting negative pressure casting method based on multi-stage negative pressure control and temperature control according to claim 5, characterized in that: The inert gas pressure is 0.2-0.5Mpa.

7. The casting negative pressure casting method based on multi-stage negative pressure control and temperature control according to claim 1, characterized in that: The cooling rate of the cooling system is controlled at 10-30°C / min.