JPH0234266A - Pin for hole as cast - Google Patents

Abstract

PURPOSE:To prevent galling with molten metal, to extend the service life and also to obtain an excellent casting product by using titanium or titanium alloy at least at end part, where is brought into contact with the molten metal, of a pin for hole as cast used in a mold and forming hardened layer on the surface. CONSTITUTION:The material of the pin 42 for hole as cast for casting is constituted with the titanium or titanium alloy having excellent heat resistance and mechanical strength and further, the hardened layer composing of nitriding layer is formed on the surface with nitriding treatment. By this method, as wetting property with the molten metal is lowered by the formation of the nitriding layer besides the heat resistance, which is the characteristic of the titanium, the growth of alloy layer with aluminum is avoided, and the galling with the molten metal is prevented. By this method, the service life can be drastically extended and also the excellent casting product can be obtd.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a cast-out pin used in metal mold casting, and more specifically, the cast-out pin is made of titanium or titanium at least in the portion inserted into the molten metal. This invention relates to a cast pin that has improved heat resistance and durability by using a titanium alloy, and which also makes it possible to obtain a cast product of excellent quality.

[Background of the invention Kodie casting method, for example, when a product is cast using a mold as in the low-pressure casting method, holes such as bolt holes in the product are directly cast out using a punching pin. There are many.

On the other hand, cast pins have come to be used constantly for the purpose of reducing the weight of products or preventing casting defects.

Conventionally, such cast-out pins are manufactured using hot tool steel (for example, JIS 5KD61) among steel materials, and are then subjected to heat treatment such as quenching and tempering, followed by soft nitriding treatment (tuftride treatment). ) for heat resistance,
Provides wear resistance. This is because the casting pin is immersed in high-temperature molten metal in the mold and is directly exposed to the high heat of the molten metal.

However, when casting cycles are continuously performed using molten aluminum alloy, it is inevitable that an alloy layer with aluminum will be formed on the surface of the cast pin. This is because hot work tool steel has good affinity with molten metal. The growth of this alloy layer leads to erosion of the cast pin.

Therefore, eventually the molten metal insertion portion of the casting pin will be damaged, or the releasability from the cast product will deteriorate, so-called galling, which will make the pin unusable.

In order to alleviate these inconveniences, various improvements have been made so far, such as using ceramics as the material for the cast pin (for example, see Japanese Patent Application Laid-Open No. 59-202136), and applying forced cooling to the cast pin. However, the service life of cast-out pins remains on the order of several thousand shots, and problems such as the fact that the desired effect cannot be expected from the viewpoint of durability are still being pointed out.

[Purpose of the Invention] The present invention has been made to overcome the above-mentioned disadvantages. A cast pin is constructed, and its surface is nitrided to form a hardened layer on the part that comes into direct contact with the molten metal.
The object of the present invention is to provide a cast-out pin which has a longer service life and which also makes it possible to obtain a product with excellent casting quality.

[Means for Achieving the Object] In order to achieve the above-mentioned object, the present invention provides a cast-out pin that is attached to a mold, and includes at least a tip portion of the constituent members of the cast-out pin that directly contacts the molten metal. It is characterized in that titanium or a titanium alloy is used as the material of the member, and that a surface hardening layer is formed by subjecting the surface of the member made of titanium material to nitriding treatment or the like.

[Embodiments] Next, preferred embodiments of the cast-out pin according to the present invention will be listed, and will be described in detail below with reference to the attached drawings in relation to the casting mold in which the cast-out pin is used. explain.

In FIG. 1, reference numeral 10 indicates a casting mold into which a cast pin according to the present invention is installed. This casting mold 10
A fixed mold 12, a movable mold 14 that is freely displaceable so as to face the fixed mold 12, and a pair of sliding molds 16a and 16b that are slidably fitted to the fixed mold 12 and the movable mold 14. It basically consists of

In this case, the fixed mold 12, the movable mold 14, and the sliding mold 16a
, 16b define a product cavity 18 corresponding to the shape of the cylinder block.

First, the stationary mold 12 includes a stationary mold body 20 and a cavity mold 22 attached to the stationary mold body 20 and defining a portion of the product cavity 18 . A hole 24 is formed at one end of the fixed main body 20, and one end of an injection sleeve 26 is fitted into the hole 24. This injection sleeve 26 is provided with an injection plunger 28 that is slidably fitted into the injection sleeve 26 under the driving action of an actuator (not shown). Further, a hot water supply hole 30 for replenishing molten metal is defined at a predetermined position of the injection sleeve 26.

On the other hand, a plurality of service holes 32 are bored in the cavity mold 22 so as to face positions corresponding to the bolt holes of the cylinder block in the product cavity 18, and cast-out pins are installed in the service holes 32. Details of this cast pin will be described later. Note that a cylinder sleeve 34 of a cylinder head is installed at the tip of the cavity mold 22 that bulges toward the product cavity 18 side.

Next, the sliding molds 16a and 16b are connected to an actuator (not shown), and are configured to be able to move forward and backward under the driving action of this actuator. in this case,
The sliding mold 16 a and the cavity mold 22 of the fixed mold 12 define a runner 36 that communicates between the product cavity 18 and the inside of the injection sleeve 26 .

On the other hand, the movable mold 14 includes a movable mold main body 38 and a cavity mold 40 attached to the movable mold main body 38 and defining a part of the product cavity 18 . The movable main body 38 is connected to an actuator (not shown) and is configured to be freely displaceable.

Here, FIG. 2 shows details of the cast-out pin according to the present invention. This cast pin 42 is made of titanium alloy. In this embodiment, Ti-6AI-4V shown in Table 1 was used among the titanium alloys. The cast pin 42 also includes a large diameter portion 44 that engages with a stepped hole 32 formed in the cavity mold 22 of the fixed mold 12, and a tapered tip portion 4 formed on the opposite side of the large diameter portion 44.
6, and a cylindrical portion 45 intermediate between a large diameter portion 44 and a tip portion 46, and this tip portion 46 fits into the molten metal filling the product cavity 18. For reference, the dimensions of this cast pin 42 are as follows: the outer diameter of the cylindrical portion 45 is 3 mm, the outer diameter of the end of the tip portion 46 is 7 mm, and the total length is 30 mm.

In addition, when manufacturing the cast-out pin 42, after forming a titanium alloy into the shape shown in the figure, a nitriding treatment is further performed in a nitriding furnace at a temperature of 850°C to 900°C for 48 hours to produce the cast-out pin 420. A nitride layer (titanium nitride) having a Vickers hardness of 2000 or more and a thickness of 5 to 6 μm is formed on the surface.

In addition, the material of the cast-out pin 42 is titanium alloy, Ti-6AI-6V-4 in addition to Ti-6AI-4V.
3n may be used, or pure titanium may also be used.

Table 1 Physical Properties of Various Metal Materials The cast pin for casting according to the present invention is basically constructed as described above, and its functions and effects will be explained next.

In FIG. 1, before pressurizing and filling the product cavity 18 of the casting mold 10 with a molten metal made of aluminum alloy by die casting, a cast pin 42 is first drilled into the cavity mold 22 of the stationary mold 12. They are attached to the provided stepped holes 32 respectively. Since the back surface of the large diameter portion 44 of the cast pin 42 is regulated by the fixed mold body 20, the cast pin 42 is engaged with the service hole portion 32 and fixed. At this time, the tip 46 of the cast pin 42 is in the state of entering into the cavity 18. Therefore, molten metal is supplied from a molten metal supply hole 30 formed in the injection sleeve 26, and the injection plunger 28 is displaced under the driving action of an actuator (not shown), so that the molten metal is filled into the product cavity 18 via the runner 36. At this time, the casting conditions are such that the temperature of the molten aluminum alloy is 660° C., and the pressure applied by the injection plunger 28 is 900 kg/am 2 .

As a result of continuous casting cycles under such casting conditions, the cast pin 4 according to the present invention using titanium alloy was obtained.
In the case of No. 2, no abnormality was observed up to 1.20,000 shots. On the other hand, hot tools! ! I (SKD61, Table 1
A cast-out pin manufactured in the same shape and using the same material as the above-mentioned pin was galled during a continuous casting cycle of 2,000 shots under the same casting conditions, and became unusable.

Thus, it can be seen that by employing a titanium-based metal material as the material of the cast pin, its seizure resistance and durability are significantly improved.

In addition to the excellent heat resistance, which is an inherent property of titanium, it also has a nitride layer formed on its surface by nitriding (
This is because titanium (titanium nitride) has poor affinity with molten metal and therefore has low molten metal wettability, making it difficult to grow an alloy layer of titanium and aluminum. Furthermore, as understood from Table 1, titanium alloy (Ti-6
AI-4V) has a thermal conductivity of about 174 compared to S K D61 and a low coefficient of thermal expansion, so it is difficult for sudden temperature changes to occur inside the casting bottle 42 due to the casting cycle, and the coefficient of thermal expansion is low. The low temperature suppresses the generation of thermal stress, which contributes to improved durability.

Here, another embodiment of the cast-out pin 42 is shown in FIG. 3. In this case, the same reference numerals will be given to the constituent elements described in the above embodiment, and detailed explanation thereof will be omitted. In the cast pin 48 according to the second embodiment, only the tip end 50, which is the part that fits into the molten metal, is made of titanium or a titanium alloy, and the other part, that is, the tail end including the large diameter part. 52 is made of a general SDK type hot work tool steel material, and the tip end 50 and the tail end 52 are joined by a joining method such as friction welding. As in the second embodiment, by using titanium or titanium alloy only for the parts that are directly immersed in the molten metal and require the most heat resistance, durability equivalent to that of the cast pin 42 of the first embodiment is improved. It is possible to achieve this. In this case, since titanium is an expensive metal material, by configuring only the tip portion with a titanium-based material, the manufacturing cost can be reduced, which is very economical.

[Effects of the Invention] As described above, according to the present invention, the material of the casting pin body is made of titanium or titanium alloy, which has excellent heat resistance and mechanical strength, and the surface is further treated with nitriding. A hardened layer made of a nitrided layer is formed.

For this reason, in addition to titanium's inherent heat resistance,
Since the wettability of the molten metal is lowered by forming the nitrided layer, the growth of an alloy layer with aluminum is avoided and galling with the molten metal is prevented. For this reason, compared to the conventional cast pins made of hot work tool steel materials, it is possible to achieve a much longer service life, and at the same time, it is possible to obtain cast products with excellent quality. It is something that plays.

Although the present invention has been described above with reference to preferred embodiments, the present invention is not limited to these embodiments.
Of course, various improvements and changes in design are possible without departing from the gist of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing a schematic configuration of a casting mold in which a casting pin according to the present invention is used, FIG. 2 is a perspective view showing the shape of a casting pin according to the present invention, and FIG. The figure is a longitudinal sectional view showing another embodiment of the cast pin according to the present invention. 10... Casting mold 12... Fixed mold 14
... Movable mold 18 ... Product cavity 28 ... Injection plunger 44 ... Large diameter part 46 ... Tip parts 15a, 16b - Sliding mold 26 ... Injection sleeve 42 ... Casting pin 45...Cylindrical part 48...Cast pin

Claims (1)

[Claims] (1) A cast-out pin that is attached to a mold, in which at least the tip part that directly contacts the molten metal is made of titanium or a titanium alloy, and is further made of titanium material. A cast-out pin characterized by forming a hardened surface layer by subjecting the surface of the member to nitriding treatment or the like.