JPH0780596A - Formation of casting plan by utilizing solidification analysis - Google Patents

Abstract

PURPOSE:To enable optimum casting to obtain defectless castings by determining a heat constant necessary for a solidification analysis with a simple shape casting mold of simple shape with high accuracy and calculating by fitting the constant to the actual casting mold, then exactly predicting a casting defect. CONSTITUTION:1. The simple shape casting is cast by the same method and alloy as the method and alloy of the casting to be subjected to the solidification analysis and the measurement data on time and temp. is inputted to a calculator. 2. The shape of the simple casting is divided to microelements to form the simple model and the heat constants including thermal conductivity is initially set. 3. The conditions for optimization decision of a difference between the data of the simple casting and the calculated values of the simple model are set. 4. The time and temp. of the simple casting are calculated from the solidification analysis of the simple model. 5. The difference between the data of the simple casting and the calculated values of the simple model are compared with the conditions for optimization decision. 6. The heat constants of the simple model are repetitively searched until the entry to the conditions for optimization decision. 7. The shape of the actual casting is divided to the microelements and a model is formed. 8. The solidification analysis of the actual model is effected by using the heat constants. 9. The calculation is repeated until the defect is decided to be permissible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a casting having few casting defects by numerically analyzing solidification of a casting and utilizing the solidification analysis.

[0002]

2. Description of the Related Art In order to carry out solidification analysis by numerical calculation, first, calculation conditions are set. In the case of solidification analysis of castings, the density and specific heat, thermal conductivity, solidification characteristics (for example, solidification start and end temperatures, latent heat of solidification) of castings and molds, between castings / molds, and between molds / atmosphere, etc. It is necessary to set a large number of thermal constants such as the heat transfer coefficient of, and the accuracy of analysis greatly depends on the setting of these values. When a general commercial program is used, it is often calculated using the values prepared by the program for a general-purpose casting method and casting alloy.

[0003]

However, in reality, the heat transfer coefficient between the casting / mold and the physical property value of the mold are largely different due to the difference in the casting method and the molding method, and the composition of the same alloy varies. The solidification characteristics often change due to the above, and in order to perform accurate solidification analysis, it is necessary to find the optimum value of each thermal constant for each casting method and casting alloy to be applied.

That is, in order to obtain useful analysis results, it is important to carefully examine and set these thermal constants, and considerable experience is required for that purpose. Also, in the case of casting methods and casting alloys that have little application record, it is necessary to study the optimum value each time. In order to solve this problem, casting analysis database and expert system are being studied, but there are various casting methods and casting alloys for castings, and it is thought that it will take a lot of man-hours and time to deal with them one by one. To be

An object of the present invention is to solve the above problems and to provide a method for producing a sound casting by performing a solidification analysis by easily and highly accurately obtaining a thermal constant.

[0006]

In order to solve the above problems, the present invention relates to a method for producing a casting plan utilizing solidification analysis, which comprises (1) producing a casting mold for a simple shape casting, and main parts of the casting mold. The temperature detection means is provided in, and casting is performed using the same casting method and casting alloy as the casting for actually making the plan, and the experimental data of the temperature and time at the time of solidifying the main portion is obtained,
(2) On the other hand, the simple shape casting and / or the mold is represented as a simple model including minute elements, and a thermal constant including at least the heat transfer coefficient between the casting and the mold is initially set in the simple model, and (3) the simple The optimization judgment condition of the difference between the temperature / time data of the shape casting and the calculated temperature / time values of the main parts of the simple model is set, and (4) solidification analysis is performed on the simple model with the initially set thermal constant. Then, calculate the temperature and time for the main parts,
(5) The difference between the temperature / time data of the simple shape casting and the temperature / time calculation value of the simple model is calculated and compared with the optimization determination condition. (6) Outside the range for the optimization determination condition. If so, the thermal constant of the simple model is searched for until it is within the range, and the above (4) to (6) are repeated, and (7) On the other hand, the plan shape of the casting to be actually manufactured is composed of minute elements. Expressed as a real model, (8) solidification analysis of the real model is performed using the thermal constants obtained by the simple model, and (9) solidification is performed until a defect in the real model is determined to be within an allowable range. It is characterized by comprising a combination of the steps (1) to (9), in which the calculation is performed and the plan is examined by repeating (7) to (9).

[0007]

EXAMPLES The present invention will be described in detail below with reference to examples. (Embodiment 1) FIG. 1 is a flow chart showing steps of an embodiment of a method for making a casting plan using solidification analysis of the present invention.

A description will be given according to the flowchart of FIG. (1) Input of experimental data A casting having a simple shape is actually cast by the same casting method and casting alloy as the casting to be prepared by solidification analysis. At this time, a thermocouple is provided as a temperature detecting means at a main part of the casting, and the temperature T (x _i , t) at each position is calculated.
_j ) is measured and this data is input to the calculator. In FIG. 1, a sand mold is used for casting, and a stepped casting riser x ₁ and weir x
_2, measures the 4 points of a product key thick portion x _3, x _4.

(2) Initial setting of heat constant The shape of the above-mentioned simple shape casting is input and divided into minute elements to form a simple model.

Then, a thermal constant having a great influence on the analysis accuracy (including at least the heat transfer coefficient between the casting and the mold) is selected, and a temporary value is set as an initial value. In addition, input calculation conditions (time step width, calculation end time, other physical property values, etc.). In Fig. 1, the heat transfer coefficient h ₁ between the casting and the mold, and the thermal conductivity of the solidified portion and the unsolidified portion of the casting are respectively shown. Parameters for optimizing the four thermal constants of λ ₁ , λ ₂ and latent heat of solidification L of the casting are p ₀ , p ₁ , p ₂ and p ₃ , p ₄ (that is, p ₀ = λ
₁ , p ₁ = λ ₂ , p ₃ = h ₁ , p ₄ = L). Other thermal constants also need to be optimized depending on the casting method and casting alloy.

(3) Optimization determination condition setting The optimization determination condition Q _x of the difference between the temperature / time data of the simple shape casting and the calculated temperature / time values of the main parts of the simple model is set.

The optimization judgment condition Q _{x in} this case is the difference between the temperature / time data of the simple shape casting of (1) above and the calculated temperature / time value of the simple model of (4) below, as will be described later. It is a value for the sum of squares.

(4) Simple model solidification calculation Solidification analysis is performed for the simple model of (2) above,
The temperature T '(x _i , t _j ) of each element corresponding to the experimental data in which the temperature and time of the simple casting of (1) are recorded is calculated.

(5) Optimization judgment Temperature and time experimental data of the simple shape casting of the above (1),
The sum of squares Q ₂ of the difference between the temperature and time calculated values of the simple model in (4) is calculated by the following formula 1, and the sum of squares Q ₂ and the above (3)
Is compared with the optimization determination condition Q _x, and if Q ₂ ≦ Q _x , it is determined to be the optimum thermal constant.

[0015]

[Equation 1]

[0016] (6) Search for Optimal Parameter Next, the above-mentioned temperature / time data and temperature / time calculated values are calculated.
Sum of squared difference Q₂But Q₂≤Q_xUntil Q₂Is the smallest
Search for a thermal constant such that That is, the sum of squares Q₂But
Q that minimizes₂Parameter p₀, P₁, P₂,
p₃Find the value of. In the example_PowellLeast squares of
The method is used for optimization.

(7) Input of actual model shape The shape of the casting for which the plan is to be manufactured is input, and the model is created by dividing it into minute elements.

(8) Solidification Calculation Next, solidification calculation is performed on the actual model with the thermal constant optimized in (5).

(9) Evaluation of solidification analysis The method is changed until it is determined that there is no defect based on the result of solidification calculation in the above (8), and the above (7) to (9) are repeated.

The above steps (1) to (9) may be carried out in series or in parallel, except that they need to be carried out in succession to the previous step, and the combinations can be freely carried out.

(Embodiment 2) An embodiment in which the method for producing a casting method using the solidification analysis of the present invention is applied to a black-core malleable cast iron casting will be described with reference to FIG.

(1) First, a mold having a staircase-shaped mold part is prepared, thermocouples are provided at four main parts of the mold, and black core malleable cast iron molten metal is poured by gravity casting. Experimental data of temperature and time when four points solidified were obtained. Casting conditions such as molding and melting were matched to the actual gravity casting method as much as possible. Fig. 2 shows the experimental data of temperature and time by □.

(2) Next, the step-shaped casting and the mold are represented as a simple model consisting of minute elements, and a thermal constant including the heat transfer coefficient of the casting and the mold is initialized to this model,

(3) to (6) Next, (3) to (6)
The solidification calculation of the stepwise simple model was performed using the thermal constants within the optimized range by proceeding to step. ● in Figure 2
The mark shows the calculation result.

From FIG. 2, comparing the temperature / time experimental data with the temperature / time calculated values, it can be seen that the temperature curve during solidification, the solidification end time at each location, and the order are in good agreement.

On the other hand, using the same thermal constant within the above-mentioned optimized range, the feeder diameter 20 mm was changed to 30 mm and 40 mm with the same black-core malleable cast iron casting of different steps and the gravity casting method. The results of the coagulation calculation carried out in Fig. 3 are shown in Figs. From FIGS. 3 and 4, it can be seen that the temperature / time experimental data and the temperature / time calculated values are in good agreement.

(7) to (9) Next, the plan shape of the casting to be actually manufactured is expressed as an actual model consisting of minute elements, and solidification analysis of the actual model is performed using the thermal constants obtained by the simple model. Until the defect in the actual model was judged to be within the allowable range, solidification calculation was performed and the plan was examined. The result is shown in FIG. The calculation result here shows the solidification progress pattern in the unsolidified region where the solid fraction is 1.0 or less.

In FIGS. 5 (A) and 5 (B), hot spots were generated in the casting product part. As a result of solidification calculation by examining the casting method, as shown in FIG. The casting could be free of defects. Since the hot spot and the actual casting defect generation position coincide with each other, it can be seen that it is extremely useful for producing a casting method for preventing casting defects.

[0029]

As described above in detail, according to the method for producing a casting plan utilizing the solidification analysis of the present invention, the thermal constant required for the solidification analysis can be easily and increased by the simple shape mold and the simple model. Since it is possible to accurately predict the casting defects by accurately calculating the heat constant and applying it to the casting model to be actually cast, it is possible to produce an optimal casting plan for obtaining a sound casting.

[Brief description of drawings]

FIG. 1 is a flowchart showing the steps of an embodiment of a method for producing a casting plan using solidification analysis of the present invention.

FIG. 2 shows an example in which the method for producing a casting using the solidification analysis of the present invention is applied to a black-core malleable cast iron casting.

FIG. 3 shows the results of solidification calculation by the gravity casting method with a feeder diameter of 30 mm in the same black-core malleable cast iron castings of different steps using the same thermal constant within the optimized range. .

FIG. 4 shows the results of solidification calculation by the gravity casting method with a feeder diameter of 20 mm in the same black-core malleable cast iron castings of different steps using the same thermal constant within the optimized range. .

FIG. 5 is a diagram in which a solidification calculation is performed and a plan is examined until it is determined that a defect in the real model is within an allowable range.

Claims (1)

[Claims] 1. A method for producing a casting plan using solidification analysis, comprising: (1) casting a casting of a simple shape casting, and providing temperature detecting means at a main portion of the casting to actually produce the casting. Cast with the same casting method and casting alloy as
Obtaining experimental data of temperature and time during solidification of the main parts,
(2) On the other hand, the simple shape casting and / or the mold is represented as a simple model including minute elements, and a thermal constant including at least the heat transfer coefficient between the casting and the mold is initially set in the simple model, and (3) the simple The optimization judgment condition of the difference between the temperature / time data of the shape casting and the calculated temperature / time values of the main parts of the simple model is set, and (4) solidification analysis is performed on the simple model with the initially set thermal constant. Then, calculate the temperature and time for the main parts,
(5) The difference between the temperature / time data of the simple shape casting and the temperature / time calculation value of the simple model is calculated and compared with the optimization determination condition. (6) Outside the range for the optimization determination condition. If so, the thermal constant of the simple model is searched for until it is within the range, and the above (4) to (6) are repeated, and (7) On the other hand, the plan shape of the casting to be actually manufactured is composed of minute elements. Expressed as a real model, (8) solidification analysis of the real model is performed using the thermal constants obtained by the simple model, and (9) solidification is performed until a defect in the real model is determined to be within an allowable range. Making a calculation and repeating (7) to (9) to examine the plan, which is characterized by the combination of the steps (1) to (9) above Method.