KR101202363B1 - Mold for testing the defect of casting and testing method using the same - Google Patents

Abstract

TECHNICAL FIELD The present invention relates to a casting defect testing die and a test apparatus thereof, and more particularly, to a casting defect testing die and a test method thereof for investigating casting defects generated during metal die casting.
The present invention, the upper mold is formed at least one or more thickness forming grooves and plate portions connected to the thickness forming grooves; And a lower mold in combination with the upper mold to form a cavity, and characterized by determining whether cracks are generated according to a difference in solidification time of the casting after injection of the molten metal.

Description

Mold for casting defect test and test method {MOLD FOR TESTING THE DEFECT OF CASTING AND TESTING METHOD USING THE SAME}

TECHNICAL FIELD The present invention relates to a casting defect testing die and a test apparatus thereof, and more particularly, to a casting defect testing die and a test method thereof for investigating casting defects generated during metal die casting.

In general, mold casting is one of various methods of forming a metal, and injects molten metal into a mold space of a mold and solidifies it to make a metal product having a desired shape. The metal products produced by this mold casting are widely used in various fields such as automobile parts, electrical equipment, optical equipment, construction, etc., which are precise mechanical component castings because of their relatively accurate dimensions and excellent mechanical properties. Mass production is possible. As the metal material used to form the metal mold, alloy steel, cast steel, cast iron, copper, copper alloy and the like are usually used.

The die casting method has many features compared to other casting methods because it uses a die as a casting material. High productivity, good working environment, small molding area and low equipment cost. In addition, the dimensions of the castings are precise and the surface is beautiful, the castings have good mechanical properties, the castings are sound and less defective. Particularly, the good mechanical properties of the castings are due to the effects of miniaturization of crystal grains obtained by quenching the castings, reduction of pinholes and pressure resistance due to forced employment of absorbed gas, and reduction of fine shrinkage pores due to directional solidification.

Recently, most of brass and aluminum castings such as faucets and valves have been produced by mold casting, and internationally, technology is being developed in the direction of making the thickness as thin as possible in terms of cost reduction due to the rise in cost of brass. Accordingly, in the process of solidifying the casting, cracks are generated according to the difference in thickness and solidification speed according to the shape of the casting, and casting defects such as hot water and dog mixing are generated. Accordingly, there is a need for an apparatus and method that can investigate the risk of casting defects prior to fabricating a casting.

The present invention relates to a mold for casting defect testing and a test apparatus thereof, and more particularly, to a casting defect testing mold and a test method thereof for investigating casting defects of cracks, spouts, and dog incorporation during metal mold casting. It is done.

The present invention, the upper mold is formed at least one or more thickness forming grooves and plate portions connected to the thickness forming grooves; And a lower mold in combination with the upper mold to form a cavity, and characterized by determining whether cracks are generated according to a difference in solidification time of the casting after injection of the molten metal.

In addition, the present invention is characterized in that it comprises a thickness control plate that can be spaced apart from each other formed between the upper mold and the lower mold forming portion of the upper mold and the lower mold.

In addition, the present invention is characterized in that the flat plate portion is located between the thickness forming grooves.

Further, the present invention is characterized in that the cross sections of the respective thickness forming grooves are different from each other.

In addition, the present invention, the combination of the upper mold and the lower mold to form a test piece that may have a difference in relative thickness, and preheating the mold; Injecting molten metal through the spouts of the upper mold and the lower mold: dismantling the mold and separating the casting from the mold: and solidifying the casting separated from the mold, and cracking the casting by the difference in the solidification speed according to the thickness It characterized in that it comprises the step of determining the occurrence of.

Casting defect test mold according to the present invention is configured as described above in order to determine the risk of cracking in the production of castings according to the metal mold in advance to change the alloy composition to the optimum conditions to make a sound casting casting quality castings Make it available.

In addition, it investigates casting defects such as cracks, spouts, and inclusions that occur during metal mold casting, and changes casting parameters such as melt temperature, casting thickness, mold preheating temperature, and release material coating. By investigating casting defects according to variables, optimal working conditions can be derived economically and in a short time.

In addition, as the value of the raw material increases, the casting can be formed in a thin and complicated manner, thereby reducing the production cost of the casting.

1 is a view showing the bottom and cross-section of the upper mold for casting bonding test according to the present invention.
Figure 2 is a view showing the top and cross-section of the lower mold for casting bonding test according to the present invention.
3 is a view showing a thickness control plate according to the present invention.
4 is a view showing the assembled mold according to an embodiment of the present invention.
5 shows a test casting made in accordance with the present invention.
6a, 6b and 6c is a view showing the surface shape of the casting according to the mold temperature after the coating of the graphite-based figure according to the invention.
Figure 7a and 7b is a view showing the surface shape of the casting according to the mold temperature after coating the zirconia figure according to the invention.
8a and 8b is a view showing the surface shape of the casting according to the mold temperature after coating the Boron Nitride figure according to the invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a view showing an upper mold of a casting defect test mold according to the present invention.

Mold casting is a method in which a molten metal is injected into a metal mold by gravity to make a casting. The mold mold at this time is called a permanent mold. The diecast method is also called the pressure diecast method and is also called the gravity diecast method. Die casting is now widely used in the manufacture of non-ferrous alloys such as Al, Mg and Cu, pistons, sleeves, crankcases, cylinders and bearings made of cast iron and steel.

Referring to Figure 1, Figure 1 (a) is a view showing the bottom surface of the upper mold 110 and Figure 1 (b) is a view showing a cross section. First, the upper mold 110 is formed with a molten iron 111 is injected into the molten metal, a plurality of grooves 112 and 113 connected to the molten metal in the longitudinal direction may be formed. In FIG. 1, two grooves are formed, and the first thickness forming groove 112 is a rhombic shape, and the second thickness forming groove 113 is a semicircular shape. This is to allow the test piece to be cast 140 (shown in FIG. 5) to have various shapes. Between the two grooves is a flat plate forming portion 114 is connected to each of the grooves so that the casting can be integrally manufactured, and when the molten metal is injected after combining with the lower mold 120 to be described later, the first thickness forming groove The molten metal is filled in the 112, the second thickness forming grooves 113, and the flat plate forming unit 114, thereby forming a casting. The flat plate forming unit 114 is manufactured to a predetermined depth on the bottom surface of the upper mold 110, the flat plate unit 144 of the test piece 140 corresponding to the flat plate forming unit 114 is formed in the thick portion (142, 143) Since it is formed thin compared to it can be seen whether the crack occurs according to the compressive and tensile stress. On the other hand, the upper mold 110 is formed with a fastening hole 115 and a guide hole 116 that can be combined with the lower mold 120.

2 is a view showing a lower mold according to the present invention.

Figure 2 (a) shows the upper surface of the lower mold, Figure 2 (b) shows the cross section. The lower mold 120 also has a fastening hole 125 and a guide hole 126 are formed to be coupled to the upper mold 110, the spout 121 to inject molten metal after the coupling with the upper mold 110 Is formed. The pouring port 121 is preferably formed to be inclined so that the molten metal can be easily guided to the cavity formed by the mold. In addition, it is connected to the spout 121, the flat groove 124 is positioned in the longitudinal direction to form the bottom surface of the test piece 140. The flat groove 124 is formed to correspond to the forming portion of the upper mold 110, and forms the cavity and the upper mold 110 to form a casting. After the lower mold 120 and the upper mold 110 are combined, and when molten metal such as iron, brass, or metal alloy is injected through the molten metal through the molten metal, the first thickness forming groove 112 and the second thickness of the upper mold 110 are formed. The first thickness portion 142 and the second thickness portion 143 of the test piece 140 formed by the forming groove 113 by the flat groove 124 and the flat plate forming portion 114 of the lower mold 120 It is connected to the plate portion 144 is formed.

Figure 3 is a view showing a thickness control plate that can adjust the thickness of the plate portion of the casting according to the present invention.

By placing a thickness control plate 130 between the upper mold 110 and the lower mold 120 it is possible to adjust the thickness of the flat portion 144 of the test piece 140. That is, the thickness control plate 130 may be inserted between the upper mold 110 and the lower mold 120 to adjust the thickness of the flat plate of the casting. At this time, the thickness control plate 130 has a 'c' shape to form a cavity, the opening 133 is formed to correspond to the flat groove 124 of the lower mold 120, the upper mold 110 and the lower mold ( Fastening between 120 is preferred. That is, when the thickness control plate 130 is fastened between the upper mold 110 and the lower mold 120 and molten metal is injected, the upper mold 110 and the lower mold 120 are spaced apart by the thickness control plate 130. Since the portion 114 and the flat groove 124 is far away, it is possible to form a test piece 140 of the desired thickness, it may be laminated a plurality of thickness control plate 130. For example, in order to precisely measure the presence or absence of cracking of the test piece which is a cast product, the thickness adjusting plate 130 is preferably set to 1 mm. Accordingly, at least one or more thickness control plates 130 may be fastened between the upper mold 110 and the lower mold 120, and the flat plate portion 144 of the test piece 140 having a constant component ratio may be formed at any thickness t. It is possible to determine whether the crack does not occur, and apply it to the product to be formed based on this. Meanwhile, the thickness control plate 130 includes fastening holes 135 and guide holes 136 corresponding to the fastening holes 115 and 125 and the guide holes 116 and 126 of the upper mold 110 and the lower mold 120. Is formed.

Figure 4 is a view from the top of the assembled mold according to the present invention.

Referring to FIG. 4, two thickness control plates 130 are coupled between the upper mold 110 and the lower mold 120. The mouths 111 and 121 of the upper mold 110 and the lower mold 120 are formed to be inclined toward the cavity so that the molten metal can easily flow when the molten metal is injected. As described above, by placing the thickness control plate 130 between the upper mold 110 and the lower mold 120, it is possible to form a test piece 140 of a desired thickness. Therefore, the molten metal having a constant composition ratio is injected, and it is possible to know whether cracks are generated depending on the thickness t of the flat plate portion 144 of the test piece during solidification. In addition, by changing the components of the metal solution at the desired thickness it is possible to find a component ratio that does not cause cracks. In addition, by grasping the casting environment under various conditions, for example, the temperature of the molten metal, the component ratio of the molten metal, and the preheating temperature of the mold, a crack-free test piece may be made and applied to a desired product.

5 is a view showing a test piece formed in accordance with the present invention.

The first thickness portion 142 and the second thickness portion 143 are positioned on both sides of the flat plate portion 144 of the test piece 140. At this time, since the thickness t of the flat plate portion 144 is smaller than the thicknesses of the first thickness portion 142 and the second thickness portion 143, the solidification speed is different depending on the thickness of the casting after the molten metal is injected. Will occur. Therefore, since the solidification speed of the first thickness portion 142 and the second thickness portion 143 is lower than that of the flat plate portion 144, tensile and compressive stresses are generated at the connection portions thereof, and cracks may occur. In recent years, the thickness of the casting is dominant for the purpose of reducing the cost of the material, and the present invention can investigate the occurrence of cracks due to the difference in thickness and solve the problem.

At this time, the experimental variables and levels to determine the occurrence of casting defects and the optimum mold casting conditions according to the type of mold molding material, the preheating temperature for the graphite, zirconia and Boron Nitride currently in use as the shape material The surface condition of the casting and the occurrence of defects were examined while increasing the test temperature to 200 ° C and changing the test piece thickness from 1 mm to 5 mm.

Table 1 and Table 2 show the defects and the optimum conditions occurring in the brass alloy according to the experimental conditions.

Experimental conditions Experiment result Experimental alloy M.T [℃] Thickness [mm] coating bottom middle Top A alloy Room temperature One G.P Misrun, Coldshut Misrun, Coldshut Misrun, Coldshut 3 Misrun, Coldshut Misrun, Coldshut Misrun, Coldshut 100 2 Misrun, Coldshut Misrun, Coldshut Misrun, Coldshut 3 Misrun Misrun 150 2 Misrun, Coldshut Misrun, Coldshut Misrun, Coldshut 3 Coldshut, Crack Coldshut, Crack Coldshut, Crack 200 2 Misrun, Coldshut Misrun, Coldshut Misrun, Coldshut 3 Misrun Room temperature 2 B.N Coldshut, Crack Coldshut, Crack 3 Crack, SolidInclusion SolidInclusion 100 2 Shrinkage Misrun Shrinkage 3 SolidInclusion Crack 150 2 SolidInclusion 3 SolidInclusion 200 2 Shrinkage 3 pin hole Room temperature 2 Z.C Coldshut, Crack Misrun 3 Shrinkage 100 2 Crack, Misrun Misrun Shrinkage 3 Crack Shrinkage 200 2 misrun 3

Experimental conditions  Experiment result alloy M.T [℃] Thickness [mm] coating bottom middle Top C alloy Room temperature One G.P Misrun Misrun Misrun 3 SolidInclusion SolidInclusion, Shrinkage Blowhole 100 One Misrun Misrun Misrun 2 Misrun, ColdShut Misrun, ColdShut Misrun, ColdShut 3 ColdShut, Shrinkage Coldshut Coldshut 150 One Misrun, ColdShut Misrun, ColdShut Misrun, ColdShut 2 Misrun, ColdShut Misrun, ColdShut Shrinkage 3 Crack Crack, Shrinkage Crack 200 One Misrun, ColdShut Misrun, ColdShut Misrun, ColdShut 2 Crack Crack, Shrinkage 3 Blowhole Room temperature 2 B.N Misrun Crack Crack 3 Crack Crack Crack 100 2 Crack, BlowHole Crack, BlowHole Shrinkage 3 SolidInclusion, Crack SolidInclusion SolidInclusion 150 2 Crack Misrun Shrinkage 3  Blow Hole, Shrinkage  Blow Hole, Shrinkage Crack 200 2 SolidInclusion Shrinkage, Crack Blowhole 3 SolidInclusion Shrinkage Room temperature 2 Z.C Coldshut Crack Blowhole 3 Crack Crack Blowhole 100 2 SolidInclusion, Crack Blowhole 3 BlowHole, Crack 200 2 Shrinkage Misrun, Crack, BlowHole Crack, BlowHole 3 Blowhole

At this time, the graphite coating is a load knowledge, the coating of zirconia and Boron Nitride was carried out by spraying. In the case of the graphite coating, misrun occurred even if the preheating temperature of the mold was increased to 200 ° C. In the case of zirconia coating, cracking and misrun did not occur even at the casting thickness of 3mm from the preheating temperature of 200 ° C. However, in the case of Boron Nitride, it was not possible to produce sound castings of less than 3mm due to the rapid solidification speed at the mold preheating temperature of 200 ℃ or less. In the case of castings, there were almost no casting defects in the zirconia figure, but a sound casting of 2 mm or less could not be obtained from any figure.

Figures 6a, 6b and 6c is a view showing the surface of the cast after coating the graphite-based figure, Figures 7a and 7b is a view showing the casting after coating of the zirconia figure, Figures 8a and 8b of the Boron Nitride figure The figure shows the casting after coating.

First of all, through the study for the optimum condition and control method of mold temperature, the fluidity according to mold preheating temperature increased steadily as the mold preheating temperature increased.In the case of alloy A, the mold preheating temperature did not increase any more than 200 ℃. Was maintained. On the other hand, the density of the initial solidification test specimen was higher than the end of the solidification, and the higher the mold preheating temperature, the higher the density. Therefore, it was confirmed that the higher the preheating temperature of the mold, the higher the possibility of removing impurities by separating impurities. When the preheating temperature of the mold was higher than 200 ℃, there were almost no defects such as pores or foreign matters in the microstructure of the initial solidification specimens through macroscopic and microstructure observation. This was not observed. Therefore, the optimum mold preheating temperature is considered to be 250 ± 25 ℃. Through experiments to derive the optimum conditions for mold shapes according to the types and casting conditions of mold shapes, firstly, cracks and misruns did not occur in the casting thickness of 3mm from the preheating temperature of 200 ℃. In any figure, it was found that a sound casting of less than 2mm could not be obtained, and that the casting preheating temperature should be maintained at 200 ° C or higher for castings of 3mm or less.

As shown in Figure 6 to 8, in the case of alloy A, when the minimum thickness of the cast product is 3mm or less, it is possible to obtain a healthy cast product by maintaining the mold preheating temperature of 200 ℃ or more even if any of the graphite, Boron Nitride and zirconia If the minimum thickness is less than 2mm, it is judged that the optimal mold casting condition is to use zirconia shape material or to maintain the mold preheating temperature above 200 ℃.

On the other hand, in the case of C alloy, it is important to keep the mold preheating temperature above 200 ℃ even if the zirconia shape material is used when the minimum thickness is 2mm or less, and it is important to use the zirconia shape material when the minimum thickness of the cast product is 3mm or less. desirable. In addition to the conditions investigated above, the mold location and size of the mold should be considered in the mold design, and the mold casting method should be established considering the minimum thickness of the casting product and how far apart from the injection position. If so, a cast of 2 mm in thickness can be produced soundly without defects.

Table 3 briefly shows the causes and preventive measures of defects that occur during the casting of brass.

flaw cause Measures Crack ㆍ Direct change of thickness does not cause directional solidification.
ㆍ Casting plan to create restraint
ㆍ Inappropriate material, increase of impurities ㆍ Change shape, balance thickness and add pressure
ㆍ Material change, adjustment of composition Misrun or Cold Shut Mold temperature
ㆍ Insufficient gas emission
ㆍ Improper casting method ㆍ Increasing mold temperature
ㆍ Reduce back pressure, increase gas emission
ㆍ Change of ball system Shrinkage ㆍ lack of pressure
ㆍ slowness of solidification
ㆍ Increasing Impurities ㆍ Adjust thickness to increase the melt temperature to facilitate directional solidification
ㆍ Adjustment of composition Blow Hole ㆍ The turbulent flow of molten metal
ㆍ Lack of gas emission
ㆍ Lack of shape ㆍ Low injection speed.
Improve gas emissions.
ㆍ To thicken the shape thickness. gnaw ㆍ lack of vent gradient
ㆍ Lack of shape
ㆍ Abrasion Damage of Mold Increased vent gradient.
Thickening of the shape.
ㆍ grinding mold surface. Solid Inclusion ㆍ The turbulent flow of the molten metal
ㆍ Lack of molten metal ㆍ Changed design of pouring system with slow injection speed
ㆍ refining and fluxing treatment Core fracture ㆍ High water pressure
ㆍ Lack of clearance of middle and mold ㆍ Slow injection speed.
ㆍ Increases the strength of the core.

As such, the present invention is a device for investigating casting defects such as cracks, spouts, and inclusions generated during metal die casting, and various casting parameters such as melt temperature, thickness of casting, preheating temperature of mold, and release coating method. It is easy to investigate the casting defects according to the casting process variable while changing them, and the optimum working conditions can be derived economically and in a short time. That is, the thickness of the casting can be controlled by inserting any number of thickness control plates 1mm thick, in the case of the upper mold 110, thick castings are formed on both sides, and a thin layer is formed in the middle, thereby shrinking according to the solidification rate. By providing conditions in which cracks are intentionally generated, information can be obtained economically and in a short period of time about the limit of castability of the material and the lowest thickness of a sound manufacturable casting.

In the above, the present invention has been described in detail with reference to the embodiments of the present invention and the accompanying drawings. However, the scope of the present invention is not limited by the above embodiments and drawings, and the scope of the present invention will be limited only by the contents described in the claims below.

110: upper mold 112, 113: thickness forming groove
114: plate forming portion 120: lower mold
130: thickness control plate 140: test piece

Claims (5)

An upper mold having at least one thickness forming groove and a flat plate portion connected to the thickness forming groove; And
And a lower mold coupled to the upper mold to form a cavity, and determining whether or not cracks are generated according to a difference in solidification time of the casting after injection of the molten metal.
The method of claim 1,
The mold for testing defect casting, characterized in that it comprises a thickness control plate which is disposed between the upper mold and the lower mold and spaced apart from the forming portion of the upper mold and the forming portion of the lower mold.
The method according to claim 1 or 2,
Mold for defect testing, characterized in that the flat plate is located between the thickness forming grooves.
The method of claim 3,
Molds for casting defect test, characterized in that the cross-section of each thickness forming groove is different from each other.
Preheating the mold and combining the upper mold and the lower mold to form a test piece that may have a difference in relative thickness;
Injecting molten metal through the spouts of the upper mold and the lower mold:
Dismantling the mold and separating the casting from the mold:
And solidifying the casting separated from the mold, and determining the occurrence of cracks in the casting by the difference in the solidification speed according to the thickness.

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