Method for improving homogeneity of casting in all directions based on resonance pouring

Abstract

The invention relates to the technical field of resonant pouring castings, in particular to a method for improving the homogeneity of castings in all directions based on resonant pouring, which comprises the following steps: preparing a mold / casting mold, setting resonant parameters, pouring molten metal, maintaining resonance and solidifying, and detecting the homogeneity. Through the resonance effect, molten metal mold filling is uniform, the size qualification rate is increased, meanwhile, grain refinement can be promoted, the isotropic performance uniformity and stability of a casting are remarkably improved, the internal defect rate is greatly reduced, the comprehensive yield is increased, and energy consumption and cost are reduced.

Description

Technical Field

[0001] This invention relates to the field of resonant casting technology, specifically a method for improving the anisotropic uniformity of castings based on resonant casting. Background Technology

[0002] In casting production, the pouring process, as the initial step in transforming liquid metal into a solid part, is a crucial stage that determines the internal quality, dimensional accuracy, and even the final performance of the casting. Its process stability and advancement directly affect the uniformity of casting quality, that is, the uniformity of performance among products in the same batch.

[0003] Currently, the traditional casting method widely used in industrial production mainly relies on the gravity of the molten metal to complete the filling process. While this natural filling process is simple and easy to implement on equipment, its inherently passive and uncontrollable nature leads to numerous defects affecting the uniformity of casting quality.

[0004] (1) The fluid behavior and defect generation in the mold cavity are highly random: Under the action of gravity alone, the flow state of the molten metal flowing into the mold cavity is difficult to control precisely, and it is easy to produce phenomena such as splashing and eddies. This will not only cause secondary oxidation and slag inclusions, but also carry a large amount of gas and hinder the smooth discharge of the original air and molding material in the mold cavity. The direct consequence is that the casting is very easy to form casting defects such as porosity and looseness inside the casting. Due to the slight difference in the liquid flow during each pouring and the slight fluctuation in the permeability of the mold coating or sand mold, the location, size and number of these defects have significant randomness. This randomness is directly manifested in the large fluctuation of the non-conforming rate of the same batch of castings under X-ray inspection. Even castings that pass the macroscopic inspection have different distributions of internal micro-defects, resulting in huge dispersion in mechanical properties such as tensile strength and elongation. The deviation can usually reach 10%-15%, which seriously affects the reliability and service life of the product.

[0005] (2) Poor controllability of solidification process and difficulty in ensuring uniformity of structure: After the molten metal is filled into the mold, it enters the solidification stage. Under static conditions, each part of the casting solidifies sequentially according to its modulus and heat dissipation conditions. The growth of grains presents a coarse dendritic morphology. From thin wall to thick wall and from surface to core, there are significant differences in grain size and morphology. This disordered grain growth leads to poor uniformity of microstructure in different areas of the casting. The non-uniformity of structure will inevitably lead to non-uniformity of mechanical and physical properties. For example, the hardness, wear resistance and even corrosion resistance of different parts of the casting may be significantly different. This further exacerbates the dispersion of performance of products in the same batch, which brings severe challenges to subsequent assembly, use and quality traceability.

[0006] To overcome the drawbacks of traditional gravity casting, there are two existing improvement schemes, as follows:

[0007] (1) Pressure casting (such as low-pressure casting, differential pressure casting): By applying external pressure, the molten metal is pushed to fill the mold smoothly and solidify under pressure, which has a good effect on reducing porosity and increasing density.

[0008] (2) Vacuum casting: Casting is carried out in a negative pressure environment, which can effectively remove the gas in the cavity and reduce the phenomenon of air entrapment.

[0009] However, existing improvement solutions suffer from limitations such as huge equipment investment, system complexity, and high maintenance costs. They typically require sealed cavities, vacuum systems, or sophisticated pneumatic control systems, which not only increases the difficulty of the process but also limits their flexibility and economy in the production of multi-variety, small-batch castings, making them difficult to widely apply in small and medium-sized enterprises. No solutions have yet been proposed to address these technical problems. Summary of the Invention

[0010] To address the problems in related technologies, this invention proposes a method for improving the anisotropic uniformity of castings based on resonant casting, thereby overcoming the aforementioned technical problems in existing related technologies. The purpose of this invention is to achieve uniform filling of the molten metal mold through the effect of resonance, improve the dimensional qualification rate, and promote grain refinement, thereby significantly improving the anisotropic performance uniformity and stability of the castings, greatly reducing the internal defect rate, improving the overall yield, and having a simple structure while reducing energy consumption and cost.

[0011] To achieve the above objectives, the present invention provides the following technical solution: a method for improving the anisotropic uniformity of castings based on resonant casting, comprising the following steps:

[0012] S1. Mold / Casting Preparation: Preparation is divided into two categories based on the casting material and the type of mold / casting mold used. One category is metal molds, suitable for die-casting aluminum alloys. The pre-made metal mold is installed onto the fixed mechanism of the casting equipment using adjustable clamps. The positioning components of the equipment are used to finely adjust the metal mold, ensuring that the gate centerline of the metal mold is strictly aligned with the outlet centerline of the insulating ladle, with a coaxiality deviation controlled within ≤0.5mm. Depending on the material of the casting to be poured, the metal mold is preheated. The preheating temperature should be set within the range of 200-400℃, depending on the alloy type and casting structure. The other category is sand molds, suitable for cast iron. The prepared sand mold is installed onto the fixed mechanism using adjustable clamps. The positioning components are used to finely adjust the spatial position of the sand mold, ensuring that the coaxiality deviation between its gate centerline and the outlet centerline of the insulating ladle is strictly controlled within ≤0.5mm. Preheating is not required.

[0013] S2, based on the casting material and wall thickness, sets the resonance frequency, amplitude and resonance time through the central controller;

[0014] S3, Molten Metal Pouring: Since the molten metal pouring methods for metal molds and sand molds differ, they need to be divided into two categories. One category involves pouring the molten metal, which has been melted and allowed to settle, into an insulated pouring ladle when using a metal mold. First, the resonance generating mechanism is activated, causing the metal mold and its fixed platform to vibrate stably at a set frequency and amplitude, entering a resonance state. Once the mold reaches the set resonance state, the flow control valve is opened via the central controller, and pouring is performed at a stable pouring speed of 5-15 kg / s. Simultaneously, acoustic emission sensors collect the acoustic wave signals generated by the molten metal flowing within the cavity in real time. The central controller uses the characteristics of the acoustic emission signals to determine in real time whether the filling is smooth, whether there is turbulence or air entrapment risk, and to monitor the overall process. The vibration frequency is dynamically fine-tuned, with a fine-tuning range of ±5Hz from the set value; another type is when using a sand mold, the molten metal that has been melted and allowed to stand is poured into an insulating ladle. After the molten metal completely fills the cavity, the resonance generating mechanism is activated, so that the sand mold and its fixed platform vibrate stably at the set frequency and amplitude, entering the resonance state. After the sand mold reaches the set resonance state, the flow control valve is opened through the central controller. At the same time, the acoustic emission sensor collects the acoustic wave signal generated by the flow of molten metal in the cavity in real time. The central controller judges whether the filling is stable and whether there is any turbulence or air entrapment risk in real time based on the characteristics of the acoustic emission signal, and dynamically fine-tunes the resonance frequency, with a fine-tuning range of ±5Hz from the set value.

[0015] S4, Resonance Maintenance and Solidification: After the molten metal completely fills the cavity, maintain the resonance state for 5 minutes to promote the discharge of gas in the cavity and the refinement of grains; then turn off the resonance generating mechanism, and after the surface layer of the casting solidifies to form a shell of sufficient strength, turn off the resonance generating mechanism and allow the casting to cool naturally to room temperature in the mold before demolding.

[0016] S5, Uniformity Detection: After demolding, the casting is tested for dimensional deviation using a displacement sensor to ensure that the deviation is ≤ ±0.2mm; samples are taken from the same batch of castings and the mechanical properties of the castings are tested to ensure that the tensile strength, hardness and other properties of the same batch of castings are ≤3%; the test results are fed back to the central controller.

[0017] Preferably, in step S1, the preheating temperature can be set to 200-300℃ for aluminum alloys and 250-350℃ for cast iron.

[0018] Preferably, in step S2, for aluminum alloy parts, the resonant frequency is set to 50-200Hz, the amplitude to 0.01-1mm, the vibration time to 5-20min, and the vibration acceleration range to 20-25s / m. 2 For gray cast iron parts, the resonant frequency is set to 60-150Hz, the vibration time to 5-20min, the amplitude to 0.1-0.9mm, and the vibration acceleration range to 15-20s / m.2 .

[0019] Preferably, in step S3, the resonance generating mechanism is an electromagnetic structure, the frequency adjustment range of the resonance generating mechanism is 1-150Hz, and the amplitude control range is 0.01-0.9mm.

[0020] Preferably, in step S1, the clamping force of the adjustable fixture is adjusted within the range of 5-50kN according to the weight of the mold.

[0021] Preferably, in step S3, the pouring speed of the molten metal during the pouring process is adjusted by a central controller, with an adjustment range of 5-20 kg / s.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] (1) This invention is a method for improving the anisotropic uniformity of castings based on resonance casting. The resonance generating mechanism causes the mold to vibrate stably. This vibration is transmitted to the molten metal, which fundamentally improves its filling fluidity and spreading properties. Combined with the precise positioning of the mold fixing mechanism and the precise flow control of the casting, it ensures that the molten metal fills all parts of the cavity smoothly and evenly. This reduces the dimensional deviation of the casting from ±0.5-1mm in the traditional process to ≤±0.2mm, and the dimensional qualification rate is stable at over 95%. This effectively reduces the machining allowance and lowers subsequent costs.

[0024] (2) This invention is a method for improving the anisotropic uniformity of castings based on resonance casting. By maintaining the resonance state for 5 minutes after casting, the continuous mechanical vibration effectively refines the solidified grains, breaks up the dendritic network, and promotes the formation of equiaxed crystals, making the overall microstructure of the casting more uniform and dense. As a result, the batch deviation of its key mechanical properties is significantly reduced from the traditional level of 10%-15% to ≤3%, greatly improving the stability and reliability of product performance.

[0025] (3) This invention is a method for improving the anisotropic uniformity of castings based on resonance casting. The acoustic emission sensor can monitor the filling status in real time and dynamically fine-tune the frequency to optimize the flow and prevent air entrapment from the source. At the same time, the resonance effect accelerates the escape of gas in the cavity and enhances the feeding ability of the molten metal at the end of solidification. Under the synergistic effect of the two, the internal defect rate of castings such as porosity and looseness can be reduced by 60%-80%, and the overall yield of castings can be increased by 15%-25%, resulting in significant economic benefits. Detailed Implementation

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention.

[0027] Example 1

[0028] This invention proposes a technical solution for improving the anisotropic uniformity of castings based on resonant casting: A method for improving the anisotropic uniformity of castings based on resonant casting includes the following steps:

[0029] S1, Mold / Casting Preparation: Preparation is divided into two categories based on the casting material and the mold / casting mold used. One category is metal molds, suitable for die-casting aluminum alloys. The prefabricated metal mold is installed onto the fixing mechanism of the casting equipment using adjustable clamps. The positioning components of the equipment are used to finely adjust the metal mold, ensuring that the gate centerline of the metal mold is strictly aligned with the outlet centerline of the insulating ladle, with a coaxiality deviation controlled within ≤0.5mm. The metal mold is preheated according to the material of the casting to be poured. The preheating temperature should be determined based on the alloy type and... The casting structure is set within the range of 200-400℃; another type is the sand mold, which is suitable for cast iron. The prepared sand mold is installed on the fixed mechanism through an adjustable clamp. The spatial position of the sand mold is finely adjusted using positioning components to ensure that the coaxiality deviation between its gate centerline and the outlet centerline of the heat preservation ladle is strictly controlled within ≤0.5mm, without the need for preheating; specifically, it ensures that the molten metal is injected smoothly and accurately; the purpose of preheating is to reduce the temperature difference between the molten metal and the mold, avoid defects such as cold shuts and incomplete pouring in the casting, and help the filling and venting of the molten metal;

[0030] S2, based on the casting material and wall thickness, sets the resonance frequency, amplitude and resonance time through the central controller;

[0031] S3, Molten Metal Pouring: Due to the different molten metal pouring methods for metal molds and sand molds, it needs to be divided into two categories. One category involves pouring qualified, statically treated molten metal into an insulated pouring ladle when using a metal mold. First, the resonance generating mechanism is activated, causing the metal mold and its fixed platform to vibrate stably at a set frequency and amplitude, entering a resonance state. Once the mold reaches the set resonance state, the flow control valve is opened via the central controller, and pouring is carried out at a stable pouring speed of 5-15 kg / s. Simultaneously, the acoustic emission sensor collects the acoustic wave signals generated by the molten metal flowing within the cavity in real time. The central controller judges in real time whether the filling is smooth, whether there is turbulence or air entrapment risk, based on the characteristics of the acoustic emission signal, and dynamically fine-tunes the resonance frequency within ±5 Hz of the set value. Specifically, activating the resonance generating mechanism in advance helps refine grains, promote venting, and reduce shrinkage porosity, thereby improving the internal quality of the casting. The other category involves using a sand mold... During mold making, the qualified molten metal, after being allowed to settle, is poured into the heat-insulating ladle. After the molten metal completely fills the cavity, the resonance generating mechanism is activated, causing the sand mold and its fixed platform to vibrate stably at the set frequency and amplitude, entering a resonance state. Once the sand mold reaches the set resonance state, the flow control valve is opened via the central controller. Simultaneously, the acoustic emission sensor collects the acoustic wave signals generated by the molten metal flowing within the cavity in real time. The central controller judges in real time whether the filling is smooth, whether there is turbulence or air entrapment risk, based on the characteristics of the acoustic emission signal, and dynamically fine-tunes the resonance frequency within ±5Hz of the set value. Specifically, resonance must be initiated only after the molten metal completely fills the cavity. If vibration occurs prematurely, the strong vibration force will cause sand particles on the cavity surface to peel off (i.e., "loose sand"). These detached sand particles will flow with the molten metal and eventually form sand hole defects in the casting, leading to product scrap. Specifically, the resonance parameters are adjusted according to the weight and type of molten metal.

[0032] S4, Resonance Maintenance and Solidification: After the molten metal completely fills the cavity, maintain the resonance state for 5 minutes to promote the discharge of gas in the cavity and the refinement of grains; then turn off the resonance generating mechanism, and after the surface layer of the casting solidifies to form a shell of sufficient strength, turn off the resonance generating mechanism and allow the casting to cool naturally to room temperature in the mold before demolding.

[0033] S5, Uniformity Detection: After demolding, the casting is tested for dimensional deviation using a displacement sensor to ensure that the deviation is ≤ ±0.2mm; samples are taken from the same batch of castings and the mechanical properties of the castings are tested to ensure that the tensile strength, hardness and other properties of the same batch of castings are ≤3%; the test results are fed back to the central controller.

[0034] In this embodiment, both the resonance generating mechanism and the mold fixing mechanism adopt existing technologies. The resonance generating mechanism consists of an electromagnetic vibration generator, a frequency regulator (5-100Hz), and an amplitude controller (0.05-0.5mm). The mold fixing mechanism includes an adjustable clamp and a horizontal / vertical positioning assembly to ensure that the mold vibrates at the same frequency as the resonance generating mechanism. The clamping force of the clamp can be adjusted according to the weight of the mold (5-50kN). The displacement sensor monitors the dimensional deviation of the casting, and the acoustic emission sensor monitors the flow state of the molten metal. The resonance parameters, molten metal temperature, and filling speed are collected in real time to form a closed-loop control.

[0035] Furthermore, in step S1, the preheating temperature can be set to 200-300℃ for aluminum alloys and 250-350℃ for gray cast iron.

[0036] Furthermore, for aluminum alloy parts, the resonant frequency is set to 50-200Hz, the amplitude to 0.01-1mm, the vibration time to 5-20min, and the vibration acceleration range to 20-25s / m. 2 For gray cast iron parts, the resonant frequency is set to 60-150Hz, the vibration time to 5-20min, the amplitude to 0.1-0.9mm, and the vibration acceleration range to 15-20s / m. 2 .

[0037] Furthermore, in step S3, the resonance generating mechanism is an electromagnetic structure, the frequency adjustment range of the resonance generating mechanism is 1-150Hz, and the amplitude control range is 0.01-0.9mm.

[0038] Furthermore, in step S1, the clamping force of the adjustable fixture is adjusted within the range of 5-50kN according to the weight of the mold.

[0039] Furthermore, in step S3, the pouring speed of the molten metal during the pouring process is adjusted by a central controller, with an adjustment range of 5-20 kg / s.

[0040] A summary and comparison of the processes for metal molds and sand molds is shown in Table 1 below:

[0041]

[0042]

[0043] Table 1 compares the uniformity parameters of traditional casting processes and the resonant casting method of this invention, as shown in Table 2 below:

[0044]

[0045]

[0046] Table 2

[0047] Alloy automotive parts were prepared according to the method of Example 1.

[0048] Material: A356-T6

[0049] The process parameters of this invention are: mold preheating 250℃, resonance frequency 50Hz, amplitude 0.12mm, pouring speed 12kg / s, and resonance maintenance time 5min;

[0050] Achieved effect:

[0051] Dimensional tolerance: ±0.15mm

[0052] Tensile strength of the same batch: average 285 MPa, standard deviation 4.3 MPa (approximately 1.5%).

[0053] Radiographic testing pass rate: 98%.

[0054] Gray cast iron automotive parts were prepared according to the method in Example 1.

[0055] Material: HT250

[0056] The process parameters of this invention are: mold preheating 300℃, resonance frequency 35Hz, amplitude 0.25mm, pouring speed 15kg / s, and resonance maintenance time 6min.

[0057] Achieved effect:

[0058] Dimensional tolerance: ±0.18mm

[0059] Tensile strength of the same batch: average 210 MPa, standard deviation 4.2 MPa (approximately 2.0%).

[0060] Tensile strength deviation of the test bar: ≤2.5%.

[0061] According to the above-mentioned actual operating parameters, the resonance casting method provided by the present invention generates stable vibration in the mold through the resonance generating mechanism. This vibration is transmitted to the molten metal, which fundamentally improves its filling fluidity and spreading properties. Combined with the precise positioning of the mold fixing mechanism and the precise flow control of the pouring, it ensures that the molten metal fills all parts of the cavity smoothly and evenly, which greatly reduces the dimensional deviation of the casting from ±0.5-1mm in the traditional process to ≤±0.2mm. The dimensional qualification rate is stable at over 95%, which effectively reduces the machining allowance and lowers subsequent costs.

[0062] By maintaining the resonance state for 5 minutes after pouring, the continuous mechanical vibration effectively refines the solidified grains, breaks up the dendritic network, and promotes the formation of equiaxed crystals, making the overall microstructure of the casting more uniform and dense. As a result, the batch deviation of its key mechanical properties is significantly reduced from the traditional level of 10%-15% to ≤3%, greatly improving the stability and reliability of product performance.

[0063] The acoustic emission sensor can monitor the filling status in real time and dynamically fine-tune the frequency to optimize the flow and prevent air entrapment from the source. At the same time, the resonance effect accelerates the escape of gas in the cavity and enhances the feeding ability of the molten metal at the end of solidification. With the synergistic effect of the two, the internal defect rate of castings such as porosity and looseness can be reduced by 60%-80%, and the overall yield of castings can be increased by 15%-25%, with significant economic benefits that are significantly better than traditional casting processes.

[0064] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for improving the isotropy of a casting based on resonant pouring, characterized in that, The method comprises the following steps: S1, mold / mold preparation: according to the casting material and the used mold / mold, the preparation work is divided into two categories; One is a metal mold, suitable for die-casting aluminum alloy, the prefabricated metal mold is installed on the fixed mechanism of the casting equipment through an adjustable clamp, the positioning assembly of the equipment is used for fine adjustment of the metal mold, so that the center line of the sprue of the metal mold is strictly aligned with the center line of the outlet of the holding ladle, the coaxiality deviation is controlled within ≤0.5 mm, according to the casting material to be poured, the metal mold is preheated, the preheating temperature should be set in the range of 200-400℃ according to the alloy type and the casting structure; the other is a sand mold, suitable for cast iron, the prepared sand mold is installed on the fixed mechanism through an adjustable clamp, the spatial position of the sand mold is finely adjusted using the positioning assembly, so that the coaxiality deviation of the center line of the sprue of the sand mold and the center line of the outlet of the holding ladle is strictly controlled within ≤0.5 mm, and preheating is not required; S2, resonance parameter setting: according to the casting material and the wall thickness, the resonance frequency, amplitude and resonance time are set through the central controller; S3, metal liquid pouring: since the metal liquid pouring methods of the metal mold and the sand mold are different, they need to be divided into two categories; one is when using a metal mold, the molten metal liquid that meets the requirements and has been treated by standing is poured into a holding ladle, the resonance generating mechanism is first started, so that the metal mold and its fixed table stably vibrate at the set frequency and amplitude, enter the resonance state, after the mold reaches the set resonance state, the flow control valve is opened through the central controller, and the pouring is carried out at a stable pouring speed of 5-15 kg / s, at the same time, the acoustic emission sensor is used to collect the acoustic signals generated by the metal liquid flowing in the mold cavity in real time, the central controller judges whether the filling is smooth, whether there is turbulent flow or gas trapping risk according to the characteristics of the acoustic emission signals in real time, and dynamically adjusts the resonance frequency, the adjustment range is ±5 Hz of the set value; the other is when using a sand mold, the molten metal liquid that meets the requirements and has been treated by standing is poured into a holding ladle, the resonance generating mechanism is started after the metal liquid completely fills the mold cavity, so that the sand mold and its fixed table stably vibrate at the set frequency and amplitude, enter the resonance state, after the sand mold reaches the set resonance state, the flow control valve is opened through the central controller, at the same time, the acoustic emission sensor is used to collect the acoustic signals generated by the metal liquid flowing in the mold cavity in real time, the central controller judges whether the filling is smooth, whether there is turbulent flow or gas trapping risk according to the characteristics of the acoustic emission signals in real time, and dynamically adjusts the resonance frequency, the adjustment range is ±5 Hz of the set value; S4, resonance maintenance and solidification: after the metal liquid completely fills the mold cavity, the resonance state is maintained for 5 min to promote the discharge of gas in the mold cavity and grain refinement; then the resonance generating mechanism is turned off, and after the shell layer with sufficient strength is formed on the surface of the casting after the casting is naturally cooled to room temperature in the mold, the casting is demolded; S5, uniformity detection: after the casting is demolded, a displacement sensor is used to detect the size deviation of the casting, to ensure that the deviation is ≤±0.2mm; samples are taken from the same batch of castings, and the mechanical properties of the castings are detected, to ensure that the performance deviation of the same batch of castings, such as tensile strength and hardness, is ≤3%; the detection results are fed back to the central controller.

2. The method for improving the uniformity of a cast in all directions based on resonance pouring according to claim 1, characterized in that, In step S1, for aluminum alloy, the preheating temperature can be set to 200-300℃; for cast iron, the preheating temperature can be set to 250-350℃.

3. The method of claim 1, wherein the method is characterized by: In step S2, for the aluminum alloy piece, the resonance frequency is set to 50-200 Hz, the amplitude is set to 0.01-1 mm, the vibration time is set to 5-20 min, and the vibration acceleration range is set to 20-25 s / m 2 ; for the gray cast iron piece, the resonance frequency is set to 60-150 Hz, the vibration time is set to 5-20 min, the amplitude is set to 0.1-0.9 mm, and the vibration acceleration range is set to 15-20 s / m 2 .

4. The method of claim 1, wherein the method is characterized by: In step S3, the resonance generating mechanism is of an electromagnetic structure, the frequency adjustment range of the resonance generating mechanism is 1-150Hz, and the amplitude control range is 0.01-0.9mm.

5. The method of claim 1, wherein the method is characterized by: In step S1, the clamping force of the adjustable clamp is adjusted in the range of 5-50kN according to the weight of the mold.

6. The method of claim 1, wherein the method is characterized by: In step S3, the pouring speed of the molten metal during the pouring process is adjusted by the central controller, and the adjustment range is 5-20kg / s.

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