Cooling effect stability evaluation method of aluminum alloy wheel hub low-pressure casting cooling system

Abstract

The invention discloses a cooling effect stability evaluation method for an aluminum alloy wheel hub low-pressure casting cooling system, and relates to the technical field of automobile wheel hub low-pressure casting. Comprises: selecting a mold object; arranging a thermocouple, and collecting temperature data; changing the initial temperature of the temperature measuring point of the thermocouple, and further acquiring real-time temperature data; feature temperature data are extracted, and linear regression of initial temperature-feature temperature values is carried out; and carrying out temperature data fluctuation analysis, and quantitatively measuring the cooling effect stability of the cooling system according to the maximum value and minimum value indexes of the discrete point deviation fitting curve. The stability of the cooling effect of the cooling system can be visually reflected, the problem that testing cannot be achieved under the condition that the initial temperature of the mold is consistent is solved, and by analyzing the relation between the initial mold temperature and the characteristic temperature value and selecting the temperature value on the temperature curve before mold opening as the characteristic temperature value, the testing accuracy is improved. The complexity of curve analysis is avoided, and the method is worthy of industrial popularization and application.

Description

Technical Field

[0001] The invention relates to the technical field of low-pressure casting of automobile wheel hubs, and in particular to a cooling effect stability evaluation method of a low-pressure casting cooling system of an aluminum alloy wheel hub. Background Art

[0002] The whole cast aluminum alloy wheel hub integrates the hub, spoke plate and rim. It has high strength, high dimensional accuracy, easy assembly and beautiful appearance. It is widely used in high-end motorcycles and cars. Low-pressure casting is widely used in the production process of aluminum alloy wheel hub castings due to its advantages such as stable filling, high crystallization pressure (0.1-0.15MPa) and easy full automation.

[0003] In order to further improve production efficiency and mechanical properties of aluminum alloy wheel hubs, it is often necessary to cool the metal molds used in low-pressure casting. Common cooling methods include full air cooling, partial water cooling, full water cooling, water mist mixing, and other cooling methods, and different manufacturers have been exploring cooling methods and cooling processes suitable for their own factories. Since shrinkage cavities, shrinkage, insufficient pouring, and coarse grains of castings will significantly affect the mechanical properties of wheel hub castings, and this series of defects are greatly affected by the temperature field, it is crucial to stably control the temperature of the mold during the production process for the stability of aluminum alloy wheel hub castings.

[0004] In the low-pressure casting batch production process of aluminum alloy wheel hub castings, due to the influence of many factors such as fluctuations in cooling medium flow rate and inconsistent production cycle length, even with the same cooling process settings, the same temperature collection point will show different temperature curves at different cycles. At the same time, since the metal molds used for low-pressure casting of aluminum alloy wheel hubs often have a large number of temperature collection points, these temperature collection points affect each other. On the other hand, when the mold contains a cooling system, the stability of the cooling effect of the cooling system is crucial to the control of mold temperature and the stability of the quality of aluminum alloy wheel hubs. However, the production cycle of each aluminum alloy wheel hub casting has differences in the initial mold temperature, cooling medium flow rate, temperature curve, cycle length and other series of states, which makes it difficult to meet the harsh conditions required by the single-factor control variable method in the process of measuring the stability of the cooling effect of the cooling system. Therefore, how to evaluate the stability of the cooling system is an important issue faced in further improving the stability of casting quality.

[0005] Therefore, in view of the problems existing in the prior art, the designers of this case, relying on their many years of experience in this industry, actively researched and improved the cooling effect stability evaluation method of the low-pressure casting cooling system of the aluminum alloy wheel hub of the present invention. Summary of the invention

[0006] The purpose of the present invention is to provide a method for evaluating the cooling effect stability of a low-pressure casting cooling system for an aluminum alloy wheel hub in view of the defects in the prior art, such as the difference in the initial mold temperature, cooling medium flow, temperature curve, cycle duration and other series of states of the production cycle of each aluminum alloy wheel hub casting, which makes it difficult to meet the harsh conditions required by the single-factor control variable method in the process of measuring the cooling effect stability of the cooling system.

[0007] To achieve the purpose of the present invention, the present invention provides a method for evaluating the stability of cooling effect of a low-pressure casting cooling system of an aluminum alloy wheel hub, the method comprising:

[0008] Execute step S1: select a mold object that can be used to evaluate the cooling effect stability of the cooling system;

[0009] Execute step S2: arrange thermocouples and collect temperature data;

[0010] Execute step S3: change the initial temperature at the thermocouple temperature measuring point, and further collect real-time temperature data;

[0011] Execute step S4: extract characteristic temperature data and perform linear regression of initial temperature-characteristic temperature value;

[0012] Execute step S5: perform temperature data fluctuation analysis, and use the maximum and minimum values ​​of the discrete points deviating from the fitting curve to quantitatively measure the stability of the cooling effect of the cooling system.

[0013] Optionally, in step S1, a mold corresponding to an aluminum alloy wheel hub casting that has been stably produced is selected as a mold object for evaluating the stability of the cooling effect of the cooling system.

[0014] Optionally, during the cooling system cooling effect stability evaluation test, the cooling process parameters are maintained unchanged.

[0015] Optionally, the opening time, closing time, and cooling medium flow rate of each cooling pipeline are set to remain unchanged during the production cycle of the aluminum alloy wheel hub.

[0016] Optionally, in step S3, the initial temperature at the thermocouple temperature measuring point is changed by closing one of the cooling pipelines and collecting temperature data at a preset rhythm.

[0017] Optionally, there is no specific limit on the number of production cycles that each single cooling pipeline is closed and reopened.

[0018] Optionally, each single cooling pipeline is closed for an equal number of production cycles, and each single cooling pipeline is reopened for an equal number of production cycles.

[0019] Optionally, in step S4, a characteristic temperature value on the temperature curve before mold opening is selected for analysis.

[0020] Optionally, in step S5, the smaller the span between the maximum value and the minimum value of the discrete point deviation is, the more stable the cooling system is.

[0021] In summary, the cooling effect stability evaluation method of the low-pressure casting cooling system of the aluminum alloy wheel hub of the present invention has the following outstanding substantial features and significant progress:

[0022] (1) Analysis based on temperature data can directly reflect the stability of the cooling effect of the cooling system. Compared with analyzing the stability of the cooling medium flow rate, it avoids the complex mapping relationship between flow stability and cooling effect stability;

[0023] (2) The difficulty of testing under the condition that the initial temperature of the mold cannot be consistent is overcome, and the temperature data collection and analysis are performed under the same cooling process settings and different initial temperatures of the mold. The test method is easy to implement;

[0024] (3) By analyzing the relationship between the initial mold temperature and the characteristic temperature value under the beat, and selecting the temperature value on the temperature curve before the low-pressure casting mold opening of the aluminum alloy wheel hub casting as the characteristic temperature value, the complexity of the curve analysis is avoided, and the influence of non-mold cooling process factors such as mold opening on the cooling effect stability analysis results is also excluded. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The figure is a flow chart of the cooling effect stability evaluation method of the low-pressure casting cooling system of the aluminum alloy wheel hub of the present invention;

[0026] FIG. 2( a ) is a schematic diagram of a cooling pipeline of a top mold of a low-pressure casting cooling system for an aluminum alloy wheel hub according to the present invention;

[0027] FIG2( b ) is a schematic diagram of the cooling pipeline of the bottom mold of the low-pressure casting cooling system of the aluminum alloy wheel hub of the present invention;

[0028] FIG2( c ) is a schematic diagram of the cooling pipe of the side mold of the low-pressure casting cooling system of the aluminum alloy wheel hub of the present invention;

[0029] Figure 3 Shown is a schematic diagram of the beat of the thermocouple of the present invention for collecting temperature data;

[0030] Figure 4 The figure shows the low-pressure casting process of aluminum alloy wheel hub and its pressure curve;

[0031] FIG5( a ) shows a graph showing the relationship between the characteristic temperature value (maximum temperature value) and the initial temperature value at a temperature measurement point on the mold;

[0032] Figure 5(b) shows the relationship between the characteristic temperature value (temperature value at 180s) and the initial temperature value at a certain temperature measurement point on the mold. Specific embodiments

[0033] The technical scheme in the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described embodiment is only a part of the embodiment of the present invention, not all of the embodiments. Based on the embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0034] See also Figure 1 , Figure 1 The figure shows a flow chart of the cooling effect stability evaluation method of the low-pressure casting cooling system of the aluminum alloy wheel hub of the present invention. The cooling effect stability evaluation method of the low-pressure casting cooling system of the aluminum alloy wheel hub comprises:

[0035] Execute step S1: select a mold object that can be used to evaluate the cooling effect stability of the cooling system;

[0036] See also Figure 2(a) to 2(c) , FIG2(a) is a schematic diagram of the cooling pipeline of the top mold of the low-pressure casting cooling system of the aluminum alloy wheel hub of the present invention. FIG2(b) is a schematic diagram of the cooling pipeline of the bottom mold of the low-pressure casting cooling system of the aluminum alloy wheel hub of the present invention. FIG2(c) is a schematic diagram of the cooling pipeline of the side mold of the low-pressure casting cooling system of the aluminum alloy wheel hub of the present invention. As a specific implementation method, according to actual conditions, the corresponding mold of the aluminum alloy wheel hub casting that has been stably produced is selected as the research object. A number of cooling pipelines 1 and thermocouple temperature measuring points (not shown) are arranged on the mold. The number and distribution of the cooling pipelines 1 and the thermocouple temperature measuring points are based on the structure of the aluminum alloy wheel hub casting and the corresponding mold, so as to meet the production needs. During the cooling system cooling effect stability evaluation test, the cooling process parameters are maintained unchanged. That is, the opening time, closing time, and cooling medium flow rate of each cooling pipeline 1 are maintained unchanged in the production rhythm of the aluminum alloy wheel hub.

[0037] Execute step S2: arrange thermocouples and collect temperature data;

[0038] The mold is installed on the low-pressure casting machine, and the thermocouple is installed on the mold. The other end of the thermocouple is connected to the computer, and the cooling pipeline 1 is connected to the joint arranged on the mold. After the connection, the hot mold operation is started, and after stable production, the thermocouple performs data collection.

[0039] Execute step S3: change the initial temperature at the thermocouple temperature measuring point, and further collect real-time temperature data;

[0040] See also Figure 3 , Figure 3 The figure shows a schematic diagram of the temperature data acquisition of the thermocouple of the present invention. In the stable production process, since the temperature change of each thermocouple temperature measuring point is small, it is difficult to use it as a data set for cooling effect stability analysis, and it is necessary to further expand the data set for analysis. Based on this, in the present invention, the initial temperature value of the mold at the thermocouple temperature measuring point under the production rhythm is changed, and then the temperature data under the rhythm is collected for analysis. Specifically, the way to change the initial temperature of the mold is to close one of the cooling pipes 1 and collect temperature data according to the preset rhythm.

[0041] Non-limiting examples, for example, 17 cooling lines 1 are arranged in the selected mold. After the production is stable, only one of the cooling lines 1 is closed first, and 5 production cycles are continued in the state, and then the closed cooling line 1 is reopened, and 3 production cycles are continued in the state. Subsequently, the remaining 16 cooling lines 1 are sequentially performed the above operations. As a person skilled in the art, it is easy to know that under the cooling effect stability evaluation test of the cooling system, there are 51 production cycles with the same cooling process parameters, and there are 85 production cycles with only one pipeline closed. The temperature data of the 51 production cycles with the same cooling process parameters are selected as the data for cooling effect stability analysis. Obviously, there is no specific restriction on the number of production cycles that each single cooling line is closed and the number of production cycles that are reopened. The number of production cycles that each single cooling line is closed and the number of production cycles that are reopened are equal. Taking into account the temperature change and the efficiency of the test, preferably, the number of production cycles that each single cooling line is closed and the number of production cycles that are reopened are 3 to 5 cycles.

[0042] Execute step S4: extract characteristic temperature data, and perform linear regression of initial temperature-characteristic temperature value.

[0043] See also Figure 4 , Figure 4 The figure shows the low-pressure casting process of an aluminum alloy wheel hub and its pressure curve. According to steps S1 to S3, the temperature data at each thermocouple temperature measuring point of the mold with different initial mold temperatures under the same cooling process are obtained to further extract characteristic temperature points from the collected temperature data. Since the low-pressure casting process can be divided into the stages of liquid raising, mold filling, pressurization, pressure holding, pressure relief, and mold opening in chronological order, in order to eliminate the influence of environmental factors on mold temperature fluctuations, the characteristic temperature value on the temperature curve before mold opening is selected for analysis.

[0044] Depend on Figure 4It can be seen that in the production process of aluminum alloy wheel hub castings, the pressure relief operation starts at 170s, and all cooling pipes 1 are closed at 180s. The highest value of the temperature curve and the temperature value at 180s can be selected as the characteristic temperature value. It should be noted that the temperature value at a certain moment from the start of the beat is used as the characteristic temperature value, and this moment may have different values ​​according to the actual production process (that is, it is not necessarily 180s). Preferably, the temperature value at a certain moment from the start of the beat is distinguished from the moment corresponding to the highest temperature value.

[0045] See also Figure 4 , and refer to Figure 5(a) to 5(b) , Figure 5(a) shows the relationship between the characteristic temperature value (maximum temperature value) and the initial temperature value at a certain temperature measurement point on the mold. Figure 5(b) shows the relationship between the characteristic temperature value (temperature value at 180s) and the initial temperature value at a certain temperature measurement point on the mold. According to the extracted characteristic temperature value data, a data scatter plot of the characteristic temperature value-initial temperature value at different positions is drawn, and a linear regression is performed on the scatter plot.

[0046] Execute step S5: perform temperature data fluctuation analysis, and use the maximum and minimum values ​​of the discrete points deviating from the fitting curve to quantitatively measure the stability of the cooling effect of the cooling system.

[0047] For a stable cooling system, under the same cooling process conditions, the initial temperature is the same and the corresponding characteristic temperature value is the same. Figure 5(a) to 5(b) It can be seen that due to the instability of the cooling system, the characteristic temperature value deviates from the theoretical value. Obviously, taking the maximum and minimum values ​​of the discrete points deviating from the fitting curve is a quantitative reflection of the fluctuation of the cooling effect due to the instability of the cooling system. This indicator is used to quantitatively measure the stability of the cooling effect of the cooling system. The smaller the span between the maximum and minimum values ​​of the discrete points deviating from the linear regression curve, the more stable the cooling system.

[0048] More intuitively, for example Figure 5(a) to 5(b) In the figure, for the thermocouple temperature measurement point, the maximum temperature - initial temperature value deviates from the fitting curve in the interval range (-5.1°C, 8.3°C), and the temperature value at 180s - initial temperature value deviates from the fitting curve in the interval range (-4.6°C, 8.4°C), indicating that when the initial temperature is the same, the cooling system can ensure that the deviation of the characteristic temperature value at this location is controlled within the range. The smaller the span of this interval, the more stable the cooling system.

[0049] In summary, the cooling effect stability evaluation method of the low-pressure casting cooling system of the aluminum alloy wheel hub of the present invention has the following outstanding substantial features and significant progress:

[0050] (1) Analysis based on temperature data can directly reflect the stability of the cooling effect of the cooling system. Compared with analyzing the stability of the cooling medium flow rate, it avoids the complex mapping relationship between flow stability and cooling effect stability;

[0051] (2) The difficulty of testing under the condition that the initial temperature of the mold cannot be consistent is overcome, and the temperature data collection and analysis are performed under the same cooling process settings and different initial temperatures of the mold. The test method is easy to implement;

[0052] (3) By analyzing the relationship between the initial mold temperature and the characteristic temperature value under the beat, and selecting the temperature value on the temperature curve before the low-pressure casting mold opening of the aluminum alloy wheel hub casting as the characteristic temperature value, the complexity of the curve analysis is avoided, and the influence of non-mold cooling process factors such as mold opening on the cooling effect stability analysis results is also excluded.

[0053] Those skilled in the art will appreciate that various modifications and variations may be made to the present invention without departing from the spirit or scope of the present invention. Therefore, if any modification or variation falls within the scope of protection of the appended claims and equivalents, it is considered that the present invention covers these modifications and variations.

Claims

1. A method for evaluating the cooling effect stability of a low-pressure casting cooling system of an aluminum alloy wheel hub, characterized in that: The cooling effect stability evaluation method of the low-pressure casting cooling system of the aluminum alloy wheel hub comprises: Execute step S1: select a mold object that can be used to evaluate the cooling effect stability of the cooling system; Execute step S2: arrange thermocouples and collect temperature data; Execute step S3: change the initial temperature at the thermocouple temperature measuring point, and further collect real-time temperature data; Execute step S4: extract characteristic temperature data and perform linear regression of initial temperature-characteristic temperature value; Execute step S5: perform temperature data fluctuation analysis, and use the maximum and minimum values ​​of the discrete points deviating from the fitting curve to quantitatively measure the stability of the cooling effect of the cooling system.

2. The cooling effect stability evaluation method of the low-pressure casting cooling system of the aluminum alloy wheel hub according to claim 1 is characterized in that: In step S1, a mold corresponding to an aluminum alloy wheel hub casting that has been stably produced is selected as a mold object for evaluating the cooling effect stability of a cooling system.

3. The cooling effect stability evaluation method of the low-pressure casting cooling system of an aluminum alloy wheel hub as claimed in claim 2 is characterized in that: During the cooling system cooling effect stability evaluation test, the cooling process parameters are maintained unchanged.

4. The cooling effect stability evaluation method of the low-pressure casting cooling system of the aluminum alloy wheel hub according to claim 3, characterized in that: The opening and closing times and cooling medium flow rates of the cooling pipelines are maintained unchanged during the production cycle of the aluminum alloy wheel hub.

5. The cooling effect stability evaluation method of the low-pressure casting cooling system of the aluminum alloy wheel hub according to claim 1, characterized in that: In step S3, the initial temperature at the thermocouple temperature measuring point is changed by closing one of the cooling pipelines and collecting temperature data at a preset rhythm.

6. The cooling effect stability evaluation method of the low-pressure casting cooling system of an aluminum alloy wheel hub as claimed in claim 5, characterized in that: There is no specific limit on the number of production cycles that each single cooling pipeline can be closed and reopened.

7. The cooling effect stability evaluation method of the low-pressure casting cooling system of an aluminum alloy wheel hub as claimed in claim 6, characterized in that: The number of production cycles that each single cooling pipeline is closed and lasts is equal, and the number of production cycles that each single cooling pipeline is reopened and lasts is equal.

8. The cooling effect stability evaluation method of the low-pressure casting cooling system of an aluminum alloy wheel hub as claimed in claim 1, characterized in that: In step S4, a characteristic temperature value on the temperature curve before mold opening is selected for analysis.

9. The cooling effect stability evaluation method of the low-pressure casting cooling system of an aluminum alloy wheel hub as claimed in claim 1, characterized in that: In step S5, the smaller the span between the maximum value and the minimum value of the discrete point deviation from the linear regression curve is, the more stable the cooling system is.

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