JPH04100667A - Die for aluminum die casting and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a die having high durability scarcely generating elution and detachment by forming the thermal spraying layer of at least one metal selected from among Nb, Mo and W on at least a part of the die cavity and the inner surface of the runner part. CONSTITUTION:On the surface parts 3a, 5a of the upper die 3 and lower die 5 from the whole runner 11 to the die cavity 17, the thermal spraying layers 19, 21 cross hatched regions as shown in the figure, is formed. In the lower die 5, the thermal spraying layer 21 covers up to a divided flowing part 9. The material for the thermal spraying layers 19, 21 formed is selected from among Nb, Mo and W and the may be used with single or the combination of plural elements. Among them, the utilization of W is the most effective.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a mold with improved corrosion resistance used for die casting of aluminum or its alloy, and a method for manufacturing the same.

[Conventional technology] Aluminum die casting (Yo) By press-fitting aluminum or the same alloy into a mold at high speed and high pressure and rapidly solidifying it,
This is a method for obtaining molded products of aluminum or its alloy.

However, due to its activity, aluminum forms an iron-aluminum alloy with the hot work tool steel (SKD series) that makes up the mold in the runners and die cavities, preventing the elution of steel components into the aluminum. invite

Further, the alloy layer formed on the surface of the die cavity partially peels off, reducing the precision of the die cavity and causing dimensional defects in the molded product.

In order to reduce or prevent such melting phenomena such as elution and peeling due to alloying, the following measures have been adopted in the past. , try to prevent corrosion caused by alloying by pasting ceramics or overlaying cemented carbide, stellite, etc. on areas where corrosion is severe, such as a part of the surface of the core. [Problems to be Solved by the Invention] However, the molds according to the above technology were still insufficient.

That is, the technique of partially pasting ceramics requires a specially molded ceramic molded product to match the internal shape of each side of the mold, which increases manufacturing costs.

Furthermore, this ceramic molded product is relatively weak against thermal shock;
It was necessary to re-upholster frequently (twice), leading to higher costs.

Furthermore, when coating with carbide, stellite, etc., only a less dense coating could be obtained, and significant elution and peeling occurred at 800'C.

Therefore, there has been a need to realize an aluminum die casting mold that is relatively easy to manufacture and has high durability against melting phenomena [Means for solving the problem] Namely, the aluminum die casting mold of the first invention The mold includes Nb, Mo, or W in at least a part of the die cavity of the mold body and the inner peripheral surface of the runner leading to the die cavity.
It is characterized by being provided with a sprayed layer of at least one metal selected from the following.

In the method for manufacturing an aluminum die casting mold according to the second aspect of the invention, at least one selected from Nb, Mo or W is applied to the runner of the mold body and the inner surface of the cavity or the core surface adjacent to or opposite to the runner. It is characterized by spraying one metal using a plasma spraying method.

[Function] When Nb, Mo or W is thermally sprayed, it easily forms a dense and tough layer. This layer is difficult to alloy with aluminum even when exposed to high temperature molten aluminum. Therefore,
In particular, at least a part of the die cavity and the inner surface of the runner, which are exposed to high-temperature molten metal or a large amount of molten metal, are made of Nb, Mo.
Alternatively, if a thermal spray layer of at least one metal selected from W is formed, elution and peeling will hardly occur, resulting in a highly durable mold.

When the above-mentioned sprayed layer is formed by a plasma spraying method, a particularly dense sprayed layer is formed among the sprayed layers. Therefore,
In particular, if a thermal spray layer is formed by plasma spraying on the runner of the mold body that is exposed to high-temperature molten metal or a large amount of molten metal, and on the inner surface of the cavity adjacent to or facing the runner, or on the similar surface of the core, It is possible to manufacture extremely durable molds.

[Example] Hereinafter, specific examples of the present invention will be described in detail based on the drawings.

FIG. 1 shows a cross-sectional view of a die-casting mold 1 according to a first embodiment. This mold 1 basically consists of an upper mold 3 and a lower mold 5 made of hot work tool steel.

The molten metal press-fitted from the casting lower is divided by the flow divider 9, and a portion thereof enters the illustrated runner 11. Furthermore, the molten metal flows into the die cavity 17 through the feed section] 3 and the land section] 5, which are part of the runner 1, and fills the inside. After this, when the molten metal cools and solidifies, the upper mold 3
By separating the die cavity 1 and the lower mold 5,
A molded article corresponding to the shape of No. 7 is obtained.

FIG. 2 is an enlarged end view of a portion of FIG. 1.

In this figure, the runner 11 is centered, and the flow direction of the molten metal is indicated by an arrow. Thermal sprayed layers 19 and 21 (in the figure, present on the surface of the area where the hatching overlaps) are formed on the surface portions 3a and 5a of the upper mold 3 and the lower mold 5 from the entire surface area to the inside of the die cavity 17. It is formed.

Regarding the lower mold 5, the sprayed layer 21 reaches up to the separator 9.

When the molten metal is supplied to this runner [1], the relatively high temperature molten metal flows through the runner 11 at high speed and high pressure, and also in a part of the corner of the die cavity 17 that is closer to the runner [1]. 17a and 17b and its course is bent. This thing 1, hot water path 1] and corner part 17a, 17b
means being exposed to particularly severe conditions of high temperature, high pressure, and high speed. Therefore, in this embodiment, a thermal spray layer 1 is applied to that part.
9.2] to prevent elution and peeling of the mold 1.

The sprayed layers 19 and 2111 are made of Nb as a sprayed material.

The material is selected from Mo or W, and these materials may be used alone or in combination. Among these, the use of W is the most effective.

Thermal spray layer 19, 2Ni is formed by a general thermal spraying method such as an electric thermal spraying method or a gas thermal spraying method. Among these electric spraying methods, plasma spraying can form a particularly dense and durable sprayed layer.

As a second example, an example of a mold 33 using a core 3 will be shown. In this embodiment, a die cavity 39 is formed with a core 31 sandwiched between two partial molds 35 and 37. Partial mold 35 forming the runner 41.
Sprayed layers 35a and 37a (in the figure, present on the surface of the area where the hatching is overlapped) are formed from the inner wall surface of the die cavity 39 to the inner surface of the die cavity 39 adjacent to the runner 4. Furthermore, a sprayed layer 31a (present on the surface of the hatched area in the figure) is also formed on the surface of the core 31 facing the runner 4.

When the molten metal is supplied to the second mold 33, the relatively high temperature molten metal flows through the runner 4 at high speed and high pressure, and hits the facing surface of the core 31 in the first die cavity 39. Its course will be bent. Therefore, the runner 41, the inner wall surface of the die cavity 39 adjacent thereto, and the surface of the core 3 facing the runner 4 are exposed to especially severe conditions of high temperature, high pressure, and high speed. For this reason, in this embodiment, thermal sprayed layers 31a, 35a, and 37a are formed in those portions to prevent the mold 33 from being eluted and peeled off.

Next, we will discuss the erosion test of bar-shaped hot work tool steel with a sprayed layer formed by plasma spraying.

As a test piece, a rod-shaped hot work tool steel (SKD6) shown in Fig. 5 was used.
1) Prepare 43. A notch 43a is provided at one end of the bar-shaped hot work tool steel 43 for fixing it to the erosion testing device 45 shown in FIG. 4, and a sprayed layer 43b is formed on the private end by plasma spraying.

This sprayed layer 43b is formed by a low pressure plasma spraying method under the following conditions, and as shown in FIG.
After an undercoat 43c made of aluminum alloy (Fly) is sprayed, one of Mo, W, and Nb is sprayed to form a sprayed layer 43b. The undercoat 43C is for preventing peeling between the bar-shaped hot work tool steel 43 and the sprayed layer 43b due to a difference in thermal expansion.

Transfer type arc current = 3OA Plasma gas: Ar-He Spraying distance: 300-400mm Atmospheric pressure 30Torr Five rod-shaped hot work tool steels 43 were manufactured for each composition of the sprayed layer, and tested as shown in Fig. 4. Attach a pair to the rotating machine 47 of the device 45.
The sample was immersed in a molten aluminum ADC12 alloy at ℃ and rotated for 20 minutes at a rotation speed of 100 rpm or 200 rpm to measure the amount of erosion (volume reduction here). A similar erosion test was conducted using test specimens of rod-shaped hot work tool steel with no carbon dioxide, and rod-shaped hot work tool steel with carbide or stellite formed as a sprayed layer.

The results are shown in FIG. As can be seen from this figure, in the test piece based on the present invention, the amount of erosion loss is extremely small even at 800°C. On the other hand, in comparative examples coated with carbide or stellite by thermal spraying, the amount of erosion was extremely large even at 750°C,
At 00°C, the amount of melting loss increases significantly, and the difference from the case where there is no sprayed layer at all is small.

In the first and second embodiments, if an undercoat as in the erosion test is formed, the peeling prevention effect can be further improved.

[Effects of the Invention] The aluminum die-casting mold and the manufacturing method thereof of the present invention prevent the runners, the inner surface of the cavity, or the surface of the core from being placed under severe conditions due to the press-fitting of high-temperature molten aluminum. Elution and peeling can be sufficiently reduced or prevented.

Therefore, the shape and dimensional accuracy of the cavity can be maintained.
High quality die-cast molded products can be obtained.

Furthermore, even in continuous use, the number of mold exchanges is reduced, which is efficient in improving productivity.

Furthermore, this mold can be easily realized by forming a thermally sprayed layer, improving the durability of the mold and reducing maintenance, thereby reducing manufacturing costs. Furthermore, it can be used not only for new models but also for repairing existing models.

[Brief explanation of drawings]

Fig. 1 is a sectional view of the first embodiment of the aluminum die casting mold of the present invention, Fig. 2 is a partially enlarged end view thereof, Fig. 3 is a sectional view of the second embodiment using a core, and Fig. 4 is a sectional view of the second embodiment using a core. The figure is an explanatory diagram of the erosion test, Figure 5 is a perspective view of the bar-shaped hot work tool steel used in the erosion test, Figure 6 is a cross-sectional view showing its surface structure, and Figure 7 is the results of the erosion test. It is a bar graph showing. 17.39...Die cavity 19.21, 31a, 35a, 37a. ... thermal sprayed layer, 3] ... core, 43 ... bar-shaped hot work tool steel,

Claims (1)

[Claims] 1. At least a part of the die cavity of the mold body;
Nb, M
An aluminum die-casting mold, characterized in that it is provided with a sprayed layer of at least one metal selected from O or W. 2 Nb, Mo is applied to the runner of the mold body and the inner surface of the cavity adjacent to or opposite to the runner, or the surface of the core.
A method for manufacturing an aluminum die-casting mold, comprising spraying at least one metal selected from or W by a plasma spraying method. 3. The aluminum die casting mold according to claim 1, wherein the thermal spray layer is provided on the inner peripheral surface of the die cavity or the runner through an undercoat.