KR101961285B1 - Method for manufacturing stick-resistant and wear-resistant aluminum die-casting sleeve and apparatus thereof - Google Patents

Abstract

A method of manufacturing a wear resistant sleeve for aluminum die casting according to the present invention comprises the steps of: fabricating a hollow mold so as to form an outer circumferential surface of an aluminum die casting sleeve; Mounting the mold on a rotor rotated in a vertical axis direction while sealing a lower end of the mold; Applying a releasing agent to the inner wall of the mold; Preheating the mold; Rotating the mold and injecting a separately prepared molten metal into the mold; Cooling the injected molten metal and releasing the cooled sleeve from the mold; Heat treating the deformed sleeve; Processing the heat-treated sleeve first; And ion-nitriding the inner peripheral surface of the sleeve in a vacuum state.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method of manufacturing a wear-resisting abrasion sleeve for aluminum die casting,

The present invention relates to a method for manufacturing a wear resistant sleeve for aluminum die casting and a manufacturing apparatus therefor.

Die casting is a method of casting a molten alloy into a precise die to obtain a casting with excellent surface properties. In general, die casting is a mass production method in a short time using a die-cast machine. Diecast castings are used in various industries because of their high dimensional accuracy and smooth casting surfaces.

The die casting operation can be classified into a cold pressurizing type die casting method and a heat pressurizing type die casting method according to a pressurizing chamber method. The former is mainly used for alloys with high melting points such as aluminum alloys, magnesium alloys and copper alloys, and the latter is used for alloy die casts with low melting points such as zinc, lead, tin and alloys. The double cold pressurized type die cast is called this name because the pressurizing chamber is not in the molten metal and is not heated.

Since the molten metal of the cold pressurized type die casting is manually cast into the pressurizing chamber by a small ladle, the supply of the molten metal must be performed promptly. For supplying the molten metal, the die casting machine is provided with a sleeve, which is a component to be supplied with the molten metal from the ladle, and a plunger that slides in the sleeve to push the molten metal filled in the sleeve into the mold. The inner wall of the sleeve is required to have abrasion resistance and thermal shock resistance as a portion where the molten metal and the plunger come into contact with each other. The phenomenon of molten metal sticking to the inner wall of the sleeve is referred to as burning, which causes shortening of the life of the sleeve.

There is a method of making a die through a machining process on a cylinder type material, but the casting method is proposed as an alternative because the waste of the material is excessive. Nevertheless, a treatment is performed to increase the wear resistance of a portion where the molten metal contacts or a thermal shock is applied. The centrifugal casting method is one of such methods, and a method of coating the inner surface of the hollow cylindrical body by using centrifugal casting is also proposed.

* Related Prior Art:

Japanese Unexamined Patent Publication No. 2006-315007 (published on November 24, 2006)

Japanese Patent Application Laid-Open No. 2006-272361 (published on October 12, 2006)

Korean Patent Publication No. 2014-0142350 (Dec. 11, 2014)

Korean Registered Patent No. 1031259 (Notice of April 29, 2011)

Japanese Laid-Open Patent Publication No. 2012-219340 (2012.11.12. Disclosed)

It is an object of the present invention to provide a method and an apparatus for manufacturing an aluminum die casting sleeve capable of improving the yield while improving the abrasion resistance and the anti-seizure property.

According to an aspect of the present invention, there is provided a method of manufacturing a wear resistant sleeve for an aluminum die casting, comprising: fabricating a hollow mold so as to form an outer circumferential surface of an aluminum die casting sleeve; Mounting the mold on a rotor rotated in a vertical axis direction while sealing a lower end of the mold; Applying a releasing agent to the inner wall of the mold; Preheating the mold; Rotating the mold and injecting a separately prepared molten metal into the mold; Cooling the injected molten metal and releasing the cooled sleeve from the mold; Heat treating the deformed sleeve; Processing the heat-treated sleeve first; And ion-nitriding the inner peripheral surface of the sleeve in a vacuum state.

In one embodiment of the present invention, the molten metal may include 0.32 to 0.42 weight percent of carbon (C), 0.80 to 1.20 weight percent of silicon (Si), 4.50 to 5.50 weight percent of chromium (Cr), 1.00 to 1.50 weight percent of tungsten 0.80 to 1.20 percent by weight of vanadium (V), 1.20 to 1.60 percent by weight of molybdenum (Mo), and micro impurities.

As an example related to the present invention, the method of manufacturing the wear resistant sleeve for aluminum die casting may further include a step of secondary processing the sleeve after the step of processing the heat-treated sleeve.

As an example related to the present invention, a spraying treatment may be further carried out between the step of primary processing the sleeve and the step of secondary processing the sleeve, at the concentrated region of wear of the sleeve.

As an example related to the present invention, the step of primary processing the sleeve may include machining on the part to be sprayed.

As an example related to the present invention, there is further included a step of performing masking on a portion excluding the portion to be nitrided by vacuum ionization, between the secondary processing step and the step of ion-nitriding the inner circumferential surface of the sleeve in a vacuum state .

As an example related to the present invention, in the step of performing ion nitridation in a vacuum state on the inner peripheral surface of the heat-treated sleeve, the ion nitridation may be performed in a vacuum plasma state.

As an example related to the present invention, the depth of the vacuum ion nitridation may be 50 to 200 탆.

An apparatus for manufacturing a wear resistant sleeve for aluminum die casting according to the present invention comprises: a hollow mold for forming an outer circumferential surface of an aluminum die casting sleeve; A rotor formed to be rotatable in a vertical axis direction with the lower end of the mold sealed; A releasing agent applied to the inner wall of the mold; A preheating portion of the mold; A rotational speed of the mold and a supply amount of the molten metal; A heat treatment portion of the sleeve released from the mold; A primary machining portion of the sleeve; A spray coating part formed so as to be carried out at a wear concentration area of the sleeve; A secondary machining portion of the sleeve; And an ion nitriding portion formed on the inner peripheral surface of the sleeve so as to perform ion nitridation in a vacuum state.

According to the method and apparatus for manufacturing the wear resistant sleeve for aluminum die casting according to the present invention, unnecessary waste of materials can be drastically reduced as compared with the Gunnedor method by applying the vertical centrifugal casting method, and compared with the horizontal centrifugal casting, Homogeneity can be ensured.

According to an embodiment of the present invention, by applying vacuum ion nitridation, the depth of nitriding can be precisely controlled as compared with the case of using conventional gas nitriding, and process control can be facilitated.

1 is a process flow diagram of a method of manufacturing an anti-seizure wear sleeve for aluminum die casting according to a first embodiment related to the present invention.
Fig. 2 is a process flow chart of a method of manufacturing an anti-seizure wear sleeve for aluminum die casting according to a second embodiment related to the present invention.
3 is a process flow diagram of a method of manufacturing an anti-seizure wear sleeve for aluminum die casting according to a third embodiment related to the present invention.
4 is a process flow diagram of a method of manufacturing an anti-seizure wear sleeve for aluminum die casting according to a fourth embodiment related to the present invention.
5 is a cross-sectional view conceptually showing a sleeve for aluminum die casting according to the present invention manufactured by vertical centrifugal casting.
Figures 6 to 8 are micrographic micrographs of the sections of the sleeve after centrifugal casting in connection with the present invention.
FIG. 9 is micrographic micrographs of the sleeve after heat treatment in accordance with the present invention. FIG.
10 is a conceptual cross-sectional view of an aluminum die casting sleeve that has undergone ion nitridation diffusion in connection with the present invention.
11 is a photograph showing a sleeve for aluminum diecasting subjected to ion nitriding in connection with the present invention.
12 is a photograph of a microstructure in which an ion nitriding diffusion layer of an ion-nitrided aluminum die casting sleeve is formed in connection with the present invention.
13 is a microstructure photograph of a spray-coated aluminum die casting sleeve in connection with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method and apparatus for manufacturing a wear resistant sleeve for aluminum die casting according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a process flow diagram of a method of manufacturing an anti-seizure wear sleeve for aluminum die casting according to a first embodiment related to the present invention.

The method for manufacturing an aluminum die casting sleeve according to the present invention comprises the steps of: fabricating a die 110, vertical centrifugal castings 121, 122, 123, 124 and 125, heat treatment 130, (Step 150).

In the step of fabricating mold 110, a hollow mold is formed to form the outer circumferential surface of the sleeve for aluminum die casting. It is designed in consideration of cooling shrinkage ratio, subtracting gradient and machining allowance according to product drawings.

5 is a cross-sectional view conceptually showing a sleeve for aluminum die casting according to the present invention manufactured by vertical centrifugal casting. 1 and 5, the vertical centrifugal casting processes 121, 122, 123, 124, and 125 will now be described.

The vertical centrifugal casting process includes a step 121 of mounting a mold 106 to a rotor 107 rotated in a vertical axis direction while sealing the lower end of the mold 106 and a step 121 of applying a release agent to the inner wall of the mold 106 A step 124 of pre-heating the mold 106, a step 124 of injecting the separately prepared molten metal M into the mold 106 by rotating the mold 106, M and releasing the cooled sleeve 101 from the mold 106. [

In the centrifugal casting method, the pressure due to the centrifugal force is applied to the molten metal, the metal oxide and the nonmetal inclusion are centrifuged by the density difference, and the directional solidification can be carried out, whereby the cast product having excellent characteristics can be manufactured. In the centrifugal casting, the rotational speed of the mold has a decisive influence on the characteristics of the casting product, and when the rotational speed of the mold 106 is low, burn-through occurs or impurities are not removed. On the other hand, if the rotation speed of the mold 106 is too high, stress in the circumferential direction due to the centrifugal force is largely generated and cracks are generated in the solidification layer, so that the appropriate rotation speed of the mold 106 is determined. In contrast to the case of using the horizontal centrifugal casting method, axial vertical tissue homogeneity can be ensured when the vertical centrifugal casting method of this embodiment is used.

For the production of the melt (M), a dissolving step (190) of the material is included. In connection with the present invention, the material of the molten metal (M) may be STD61 alloy steel for hot-mold. Specifically, the material is selected from the group consisting of 0.32 to 0.42 weight percent of carbon (C), 0.80 to 1.20 weight percent of silicon (Si), 4.50 to 5.50 weight percent of chromium (Cr), 1.00 to 1.50 weight percent of tungsten (W) 0.80 to 1.20 weight percent, molybdenum (Mo) 1.20 to 1.60 weight percent, and micro impurities. The sleeve 101 is manufactured through vertical centrifugal casting by using the alloy steel for hot metal as a direct material. In this respect, there is a difference from the technique of previously forming a cylindrical body and forming a separate casting layer on the inner wall of the cylindrical body by the centrifugal casting method. According to the method of the present embodiment, since most of the shape of the sleeve 101 is formed by the vertical centrifugal casting, it is possible to drastically reduce loss of material during the machining process such as a gun drill.

5, the apparatus for manufacturing the wear resistant sleeve for aluminum die casting according to the present invention is characterized in that the molten metal M supplied from the ladle exits in the direction of the inner wall of the mold 106 in the proper position and direction in the mold 106 A vertically movable nozzle inlet 108 may be provided. A controller for controlling the apparatus for preheating the mold 106 and the rotational speed of the mold 106 and the supply amount of the molten metal M may be provided. The mold 106 preheating device may be an electrical heater or an induction heating device. A controller of the rotor 107 is provided to control the rotation speed of the mold 106 and an automatic calculation device such as a computer for controlling the supply amount of the molten metal M may be included.

Vertical Centrifugal Casting Depending on the use of the molten metal (M), if the cast steel has a thin cross-sectional thickness, cast steel having a low carbon equivalent is more likely to form carbide, and the effect of chilling due to the difference in cooling rate may be increased have. Accordingly, the molten metal is injected at a slightly higher carbon equivalent within the required composition ratio, and the centrifugal injection is performed from a thinner product. In addition, molybdenum, nickel, copper, or tin alloying elements may be added to the casting of residual molten cast iron to increase the degree of fluidity. Such an alloying element is added to the ladle to completely dissolve and uniformly disperse the molten metal (M), and a small amount of graphitizing inoculant is added to allow sufficient nucleation to ensure proper solidification .

The results of microscopic observation of each part in the centrifugal casting state (as-cast) are shown in FIGS. 6 to 8. FIG. The overall microstructure shows a dendrite shape as a solidified casting structure, and the outer diameter is a contact surface of the mold, which has a cooling rate faster than that of the inner diameter portion, and becomes coarser from the fine structure to the inner portion.

As a result of hardness distribution test in the as-cast state, the inner-outer side showed a uniform hardness of about 55 HRC irrespective of the microstructure, and thus the degree of partialization of the alloy component by centrifugal casting was found to be almost zero.

When the shape of the sleeve 101 is completed through the vertical centrifugal casting processes 121, 122, 123, 124 and 125, the sleeve 101 is heat-treated (130). Full annealing can be performed to improve and soften the steel structure, remove internal stresses, spheroidize the carbide, and homogenize the internal structure. It is heated up to a point immediately below the Ac 1 point and taken out to perform air cooling or water cooling. With this method, the steel is sufficiently softened to improve machinability and workability.

Microscopic microphotographs of the sleeve 101 after the heat treatment are shown in FIG. That is, unlike the microstructure of a general steel STD61 steel forgings, the resin phase does not disappear even after the heat treatment, and the microstructure of the martensite is exhibited due to the reformation and transformation of the alloy component.

When the heat treatment is completed, primary processing (140) is performed on the sleeve (101). The outer diameter of the sleeve 101 is machined through an operation such as turning.

After the primary machining 140 is performed, the inner circumferential surface of the sleeve 101 is ionized in a vacuum state (150). FIG. 11 is a photograph showing an ion-nitrided sleeve for aluminum die casting according to the present invention, and FIG. 12 is a photograph showing a sleeve for aluminum diecasting according to the present invention. And the ion nitriding diffusion layer of the aluminum diecasting sleeve subjected to the ion nitriding process is formed. Ion nitration can be conducted in a vacuum plasma state. The ion nitriding diffusion layer 102 is formed on the inner peripheral surface of the sleeve 101, and the depth may be 50 to 200 占 퐉. The compound layer formed on the surface of the steel by the ion nitriding process is composed of? Phases (Fe _{2 -3} N) and? 'Phases (Fe ₄ N). Since the normal nitrided layer is weak in resistance, it is desirable to avoid a mixed layer of epsilon + gamma 'phase and to generate only a single phase of only epsilon or gamma phase in order to avoid three dimensional stress. Ion nitration is an alternative to the salt bath nitriding method. In addition, it can shorten the nitriding treatment time remarkably, and can utilize advantages of low pollution, easy control of the nitrided layer, and high nitriding efficiency by using electric energy.

As a result of observing the surface layer of the test piece subjected to the ion nitriding treatment 150, it was confirmed that the compound layer was formed to about 6 to 7 mu m and the diffusion layer was formed to be about 150 mu m or more, as shown in Fig.

Fig. 2 is a process flow chart of a method of manufacturing an anti-seizure wear sleeve for aluminum die casting according to a second embodiment related to the present invention.

In this example as well, the mold preparation 210, the mold vertical mounting 221, the mold release agent application 222, the preheating 223, the centrifugal injection control 224, the cooling and release mold 225, the heat treatment 230, 240, vacuum ion nitridation 260, and the like, and is similar to the first embodiment. However, there is added a step 250 of secondary machining of the sleeve after the step of first operating the sleeve.

The secondary machining step 250 performs internal and external grinding to compensate for the minor deformation dimensions of the sleeve subjected to the heat treatment 230 and the primary machining 240 and to ensure final surface roughness.

3 is a process flow diagram of a method of manufacturing an anti-seizure wear sleeve for aluminum die casting according to a third embodiment related to the present invention. In this example as well, the mold production 310, the vertical mold mounting 321, the mold release agent application 322, the preheating 323, the centrifugal injection control 324, the cooling and release 325, the heat treatment 330, 340, secondary processing 360, vacuum ion nitridation 370, and the like, and is similar to the second embodiment. (350) spraying the sleeve between the primary machining step (340) and the secondary machining step (360) on the wear concentrate of the sleeve. The thermal spraying step 350 is a step of melting the carbide and oxide-based material having excellent mechanical and physical properties but having a high melting point and poor machinability with a hot flame or a plasma to rapidly melt the molten particles, A thick film layer having a thickness of 0.1 to 1 mm is formed on the base material. In this example, a mixed form of tungsten carbide (WC) is applied to a nickel field-usable alloy. Table 1 below shows the components of the spray coating in connection with the present invention.

Ingredient / material C Si B Fe Cr Ni WC-Co ratio 0.5 2.5 2.5 2.5 11 46 35

A post-heat treatment may be performed to reduce porosity after spray coating of the virgin alloy. Fig. 13 shows the result of microscopic observation before and after the heat treatment to confirm the porosity. That is, it can be seen that a large amount of pores are generated in the coating layer when the flame spraying is performed, and when the heat treatment is performed, the pores are almost extinguished and the coating structure is dense. The thickness of the spray coating layer can be freely adjusted according to the purpose, and in this embodiment, it is 700 ± 100 μm.

4 is a process flow diagram of a method of manufacturing an anti-seizure wear sleeve for aluminum die casting according to a fourth embodiment related to the present invention.

In this example as well, the mold making 410, the mold vertical mounting 421, the releasing agent application 422, the preheating 423, the centrifugal injection control 424, the cooling and releasing 425, the heat treatment 430, 440, a spraying process 450, a secondary process 460, and a vacuum ion nitriding process 470, and is similar to the third embodiment. However, masking is performed on the portion excluding the portion subjected to vacuum ion nitriding (Step 470) between the secondary processing step 460 and the step 470 of performing ionization in vacuum on the inner circumferential surface of the sleeve have. In this masking step 470, in particular, in the case of the spray coating layer, since the hardness is secured by itself, it is not necessary to perform the ion nitriding diffusion treatment, so that it is excluded from the formation of the ion nitriding diffusion layer and waste of material can be reduced.

The method and apparatus for manufacturing the wear resistant sleeve for aluminum die casting described above are not limited in the construction and the method of the described embodiments. The embodiments may be configured so that all or some of the embodiments may be selectively combined so that various modifications may be made.

101: Sleeve 102: Nitrided layer
106: mold 107: rotor
108: Up and down movable nozzle inlet

Claims (9)

Fabricating a hollow mold to form an outer circumferential surface of an aluminum die casting sleeve;
Mounting the mold on a rotor rotated in a vertical axis direction while sealing a lower end of the mold;
Applying a releasing agent to the inner wall of the mold;
Preheating the mold;
Rotating the mold and injecting a molten metal made of an alloy steel for hot mold separately prepared by moving a nozzle injection port in a vertical direction inside the mold;
Cooling the injected molten metal and releasing the cooled sleeve from the mold;
Heat treating the deformed sleeve;
Processing the heat-treated sleeve first;
Performing a spraying process on a wear-concentrated portion of the sleeve;
Performing a post-heat treatment so as to reduce pores in the sleeve subjected to spraying treatment;
Secondary processing the sleeve;
Masking the sprayed area of the sleeve; And
And ion-nitriding the inner peripheral surface of the sleeve in a vacuum plasma state.
delete delete delete The method according to claim 1,
The step of first machining the sleeve comprises:
And processing the portion to be sprayed. ≪ RTI ID = 0.0 > 11. < / RTI >
delete delete The method according to claim 1,
Wherein the depth of the vacuum ion nitriding is 50 to 200 占 퐉.
delete

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