Plunger tip for die casting and die casting device

Abstract

To suppress slidability deterioration of a plunger tip for die casting.SOLUTION: A plunger chip for die casting is used by reciprocating while sliding in an injection sleeve to which a powder lubricant is applied, and includes a chip body and a cast iron ring mounted on the outer periphery of the chip body to form a sliding surface with respect to the injection sleeve. The average grain size of graphite contained in the cast iron composing the cast iron ring is larger than the average grain size of the powder lubricant.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a plunger tip for die casting and a die casting apparatus.

Background Art

[0002] Conventionally, in a die casting apparatus, in order to extrude molten metal at high speed and high pressure, it is necessary to move a plunger tip at high speed within an injection sleeve. When the plunger tip is moved at high speed, the supply of lubricant to the sliding surface between the plunger tip and the injection sleeve may be insufficient, resulting in an increase in sliding resistance and possible stoppage of operation. The plunger tip described in Patent Document 1 suppresses a decrease in slidability by providing a layer made of molybdenum as a solid lubricant on a part of the outer peripheral surface of the plunger tip.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the plunger tip described in Patent Document 1, since the heat resistance of molybdenum is low, there is a problem that the slidability decreases in a high-temperature environment in contact with molten metal.

Means for Solving the Problems

[0005] The present disclosure can be realized in the following forms. According to one embodiment of the present disclosure, there is provided a plunger tip for die casting that is used reciprocally while sliding within an injection sleeve to which a powder lubricant containing graphite is applied. This plunger tip includes a tip body and a cast iron ring that is mounted on the outer periphery of the tip body, has an outer diameter larger than the outer diameter of the tip body, and forms a sliding surface with the injection sleeve. The average particle diameter of the graphite contained in the spheroidal graphite cast iron forming the cast iron ring is larger than the average particle diameter of the powder lubricant. The cast iron ring has a groove on its outer peripheral surface. The groove is formed linearly, and the longitudinal direction of the groove is formed to be in a twisted position with respect to the central axis of the cast iron ring. One end of the groove reaches the end face on the side far from the cavity in the reciprocating direction of the plunger tip among the both end faces in the central axis direction of the cast iron ring, and the other end does not reach any end face of the cast iron ring.

[0006] (1) According to one embodiment of the present disclosure, a plunger tip for die casting is provided. This plunger tip is a plunger tip for die casting that is used reciprocally while sliding in an injection sleeve provided with a powder lubricant, and includes a tip body and a cast iron ring attached to the outer periphery of the tip body and forming a sliding surface with the injection sleeve. The average particle size of graphite contained in the cast iron forming the cast iron ring is larger than the average particle size of the powder lubricant. According to the plunger tip of this embodiment, since the cast iron ring is formed of cast iron, a decrease in heat resistance can be suppressed. Further, since the average particle size of graphite contained in the cast iron forming the cast iron ring is larger than the average particle size of the powder lubricant applied in the injection sleeve, when graphite falls off from the surface of the cast iron ring, the powder lubricant enters the voids generated, so that the powder lubricant is easily retained on the surface of the cast iron ring, and a decrease in the slidability of the plunger tip can be suppressed. (2) In the above embodiment, the cast iron ring may be provided with a groove on its outer peripheral surface. According to the plunger tip of this embodiment, since the outer peripheral surface of the cast iron ring is provided with a groove, in the return path (the path away from the cavity), the powder lubricant is easily supplied to the sliding surface along the groove, so that a decrease in the slidability of the plunger tip can be more suppressed. (3) In the above embodiment, the groove may be formed linearly, and the longitudinal direction of the groove may be formed to be twisted with respect to the central axis of the cast iron ring. According to the plunger tip of this embodiment, since the longitudinal direction of the groove is twisted with respect to the central axis of the cast iron ring, in the forward path (the path approaching the cavity), the outflow of the powder lubricant held in the groove from the groove can be suppressed. As a result, the powder lubricant is easily supplied continuously to the sliding surface, so that a decrease in the slidability of the plunger tip can be more suppressed. (4) In the above embodiment, the groove is formed linearly, and one end of the groove reaches the end face on the side far from the cavity in the reciprocating direction of the plunger tip among both end faces in the central axis direction of the cast iron ring, and the other end may not reach any end face of the cast iron ring. According to the plunger tip of this form, since one end of the groove reaches the end face of the cast iron ring on the side far from the cavity, and the other end does not reach any end face of the cast iron ring, even if the powder lubricant is supplied to the groove from one end of the groove during the return path, it is possible to suppress the powder lubricant supplied to the groove from passing through the groove and mixing into the molten metal. Thereby, it is possible to suppress the deterioration of the quality of the die-cast product. (5) In the above embodiment, a plurality of the cast iron rings arranged side by side in the reciprocating direction of the plunger tip may be provided. According to the plunger tip of this form, among the plurality of cast iron rings, only the worn part (mainly the ring on the side close to the cavity) can be exchanged and the use can be continued, so that the component replacement cost due to the wear of the plunger tip can be suppressed. (6) In the above embodiment, the plurality of cast iron rings may be formed of the same material as each other. According to the plunger tip of this form, since the plurality of cast iron rings are formed of the same material as each other, the coefficient of thermal expansion is the same, and the difference in dimensional change due to temperature rise for each cast iron ring can be suppressed, and the decrease in the slidability of the plunger tip due to the difference in dimensional change for each cast iron ring can be suppressed. (7) In the above embodiment, a plurality of the cast iron rings arranged side by side in the reciprocating direction of the plunger tip are provided, and among the plurality of cast iron rings, the cast iron ring closest to the cavity in the reciprocating direction of the plunger tip may have the groove on the outer peripheral surface. According to the plunger tip of this form, among the plurality of cast iron rings, it becomes easier to supply the powder lubricant to the sliding surface of the cast iron ring closest to the cavity in the reciprocating direction of the plunger tip, where the sliding resistance tends to be high, so that the decrease in the slidability of the plunger tip can be suppressed. (8) In the above embodiment, the average particle size of the graphite contained in the cast iron forming the cast iron ring may be 1.5 times or more the average particle size of the powder lubricant. According to the plunger tip of this form, since the average particle size of the graphite contained in the cast iron forming the cast iron ring is 1.5 times or more the average particle size of the powder lubricant applied in the injection sleeve, the powder lubricant is more likely to be retained by the surface of the cast iron ring, and a decrease in the slidability of the plunger tip can be further suppressed. (9) In the above embodiment, the average particle size of the graphite contained in the cast iron forming the cast iron ring may be 30 μm or more. According to the plunger tip of this form, since the average particle size of the graphite contained in the cast iron forming the cast iron ring is 30 μm or more, a powder lubricant having an average particle shape smaller than 30 μm is more likely to be retained by the surface of the cast iron ring, and a decrease in the slidability of the plunger tip can be suppressed.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0008] A. Embodiment: FIG. 1 is an explanatory diagram showing a die-casting apparatus 1000 to which a plunger tip 100 for die-casting according to the present embodiment is applied. The die-casting apparatus 1000 transmits the driving force generated by a driving apparatus (not shown) to the plunger tip 100 via a plunger rod 200, and reciprocates the plunger tip 100 within an injection sleeve 300. During the reciprocating motion, a sliding resistance occurs between the plunger tip 100 and the injection sleeve 300. A highly heat-resistant powder lubricant is applied to the inner peripheral surface of the injection sleeve 300, and the sliding resistance is suppressed by supplying the powder lubricant between the plunger tip 100 and the injection sleeve 300. In the present embodiment, a powder lubricant mainly composed of graphite is used. The die-casting apparatus 1000 drives the plunger tip 100 in this way to extrude the molten metal filled inside the injection sleeve 300 and fill the molten metal into a cavity 10 formed by a fixed mold 400 and a movable mold 500. In the following description, the path along which the plunger tip 100 approaches the cavity 10 in the reciprocating motion is also referred to as the "forward path", and the path along which the plunger tip 100 moves away from the cavity 10 is also referred to as the "return path".

[0009] FIG. 2 is an exploded view of the plunger tip 100 according to the present embodiment. The plunger tip 100 includes a tip body 110 and cast iron rings 121 and 122. The tip body 110, the cast iron ring 121, and the cast iron ring 122 are combined such that their respective central axes coincide to form the central axis L of the plunger tip 100. The tip body 110 is formed of body members 111 to 113. In the present embodiment, the body members 111 to 113 are formed of SKD61 material. The body members 111 to 113 each include a screwing portion C and are formed to be screwable with each other. Also, the outer diameter at the screwing portion C is formed smaller than the outer diameter of other portions.

[0010] The cast iron rings 121 and 122 have a ring shape and are respectively mounted on the outer periphery of the screwed portions C of the main body members 112 and 113. The cast iron rings 121 and 122 are held by the chip body 110 by the fastening force when the main body members 111 to 113 are screwed together. The outer diameters of the cast iron rings 121 and 122 are larger than the outer diameter of the chip body 110. When the cast iron rings 121 and 122 are combined with the chip body 110, the outer peripheral surfaces of the cast iron rings 121 and 122 protrude from the outer peripheral surface of the chip body 110 when viewed in the direction of the central axis L of the plunger tip 100. Therefore, when the plunger tip 100 slides in the injection sleeve 300, the outer peripheral surfaces of the cast iron ring 121 and the cast iron ring 122 form a sliding surface with the injection sleeve 300.

[0011] In this embodiment, the cast iron rings 121 and 122 are formed of cast iron having a graphite nodulization rate of 80%. The average particle diameter of the spherical graphite contained in the cast iron is controlled by changing manufacturing conditions such as the cooling rate so as to be larger than the average particle diameter of the powder lubricant used. The average particle diameter of the spherical graphite contained in the cast iron is preferably about 1.5 to 2 times the average particle diameter of the powder lubricant used. In this embodiment, the average particle diameter of the spherical graphite contained in the cast iron forming the cast iron rings 121 and 122 is 30 μm. The spherical graphite contained in the cast iron falls off from the surfaces of the cast iron rings 121 and 122 due to the sliding resistance with the injection sleeve 300, forming voids on the surfaces of the cast iron rings 121 and 122. By allowing the powder lubricant smaller than the voids to enter the voids thus formed, the powder lubricant is more easily held on the surfaces of the cast iron rings 121 and 122, and a decrease in the slidability of the plunger tip 100 can be suppressed.

[0012] FIG. 3 is an external perspective view of the cast iron ring 121. Among the cast iron rings 121 and 122, the cast iron ring 121, which is the cast iron ring arranged closer to the cavity 10 in the reciprocating direction of the plunger tip 100, has a plurality of grooves G on its outer peripheral surface. The grooves G are linearly formed such that the longitudinal direction is twisted with respect to the central axis M of the cast iron ring 121. By forming the grooves G in this way, in the return path, the powder lubricant is easily supplied to the sliding surface between the injection sleeve 300 and the cast iron ring 121 along the grooves G, so that a decrease in the slidability of the plunger tip 100 can be suppressed. In addition, in the forward path, the outflow of the powder lubricant held in the grooves G from the grooves G is suppressed, and the powder lubricant is easily supplied continuously to the sliding surface, so that a decrease in the slidability of the plunger tip 100 can also be suppressed.

[0013] One end of the groove G reaches one of the both end faces in the direction of the central axis L of the cast iron ring 121, but the other end of the groove G does not reach any of the end faces of the cast iron ring 121. When the cast iron ring 121 is combined with the chip body 110, the end face on the side where the end of the groove G reaches is combined with the chip body 110 so as to be the end face far from the cavity 10 in the reciprocating direction of the plunger tip 100. By combining the chip body 110 and the cast iron ring 121 in this way, in the return path, even if the powder lubricant is supplied to the groove G from one end of the groove G, the other end does not reach any of the end faces of the cast iron ring 121, so that the powder lubricant supplied to the groove G can be prevented from passing through the groove G and mixing into the molten metal, and a decrease in the quality of the die-cast product can be suppressed.

[0014] Figure 4 is a diagram showing samples for the performance evaluation test. As shown in Figure 4, plunger tips of Samples 1 to 4 were created for the performance evaluation test. The ring that forms the sliding surface with the injection sleeve 300 provided in the plunger tip of Sample 1 is formed of SKD61 material, which is the same material as the chip body 110 of the present embodiment. The ring provided in the plunger tip of Sample 2 is formed of cast iron in which the average grain size of the contained spherical graphite is 10 μm. The ring provided in the plunger tip of Sample 3 is formed of cast iron in which the average grain size of the contained spherical graphite is 30 μm. The ring provided in the plunger tip 100 of Sample 4 is formed of cast iron in which the average grain size of the contained spherical graphite is 30 μm, and a groove G is formed on the outer peripheral surface of the ring. Note that the spheroidization rate of the graphite in the cast iron forming the ring provided in each sample is 80% in all cases.

[0015] Figure 5 is a diagram showing the results of the performance evaluation test. Note that the average grain size of the powder lubricant used in the performance evaluation test is larger than 10 μm and smaller than 30 μm. In Figure 5, the horizontal axis represents the number of reciprocations of the plunger tip, and the vertical axis represents the sliding resistance between the plunger tip and the injection sleeve 300. Figure 5 shows the change in the sliding resistance with the increase in the number of reciprocations for each sample.

[0016] In Figure 5, for Sample 1, the sliding resistance increases rapidly at a smaller number of reciprocations compared to other samples. Sample 2, which has a ring formed of cast iron in which the average grain size of the contained spherical graphite is 10 μm, which is smaller than the average grain size of the powder lubricant, has an increased number of reciprocations until the sliding resistance starts to increase compared to Sample 1. Sample 3, which has a ring formed of cast iron in which the average grain size of the contained spherical graphite is 30 μm, which is larger than the average grain size of the powder lubricant, has an even further increased number of reciprocations until the sliding resistance starts to increase compared to Sample 2. Furthermore, Sample 4, which has a groove G on the outer peripheral surface, has a suppressed rate of increase in the sliding resistance with the increase in the number of reciprocations compared to Sample 3.

[0017] According to the plunger tip 100 in the embodiment described above, since the cast iron rings 121 and 122 are formed of cast iron, a decrease in heat resistance can be suppressed. Further, since the average particle size of graphite contained in the cast iron forming the cast iron rings 121 and 122 is larger than the average particle size of the powder lubricant, when graphite falls off from the surface of the cast iron ring 121, the powder lubricant enters the pores generated, making it easier for the powder lubricant to be retained on the surfaces of the cast iron rings 121 and 122, and a decrease in the slidability of the plunger tip 100 can be suppressed.

[0018] Further, since the plunger tip 100 is provided with the groove G on the outer peripheral surface of the cast iron ring 121, in the return path, the powder lubricant is easily supplied to the sliding surface along the groove G, so that a decrease in the slidability of the plunger tip 100 can be more suppressed.

[0019] Also, since the longitudinal direction of the groove G is in a twisted position with respect to the central axis L of the cast iron ring 121, in the forward path, the outflow of the powder lubricant held in the groove G from the groove G can be suppressed. For this reason, the powder lubricant is easily supplied continuously to the sliding surface, so that a decrease in the slidability of the plunger tip 100 can be more suppressed.

[0020] Also, since one end of the groove G reaches the end face of the cast iron ring 121 on the side far from the cavity 10 and the other end does not reach any end face of the cast iron ring 121, in the return path, even if the powder lubricant is supplied to the groove G from one end of the groove G, it is possible to suppress the powder lubricant supplied to the groove G from passing through the groove G and mixing into the molten metal. For this reason, a deterioration in the quality of the die-cast product can be suppressed.

[0021] Further, since the plunger tip 100 can continue to be used by replacing only the worn ring among the cast iron rings 121 and 122, the component replacement cost due to the wear of the plunger tip 100 can be suppressed.

[0022] In addition, since the cast iron rings 121 and 122 are formed of the same material, they have the same coefficient of thermal expansion, which can suppress the difference in dimensional changes due to temperature rise for each of the plurality of cast iron rings 121, and can suppress the decrease in the slidability of the plunger tip 100 due to the difference in dimensional changes.

[0023] In addition, the plunger tip 100 can easily supply a powder lubricant to the sliding surface of the cast iron ring 121, which is likely to have a high sliding resistance, among the cast iron rings 121 and 122, so that the decrease in the slidability of the plunger tip 100 can be suppressed.

[0024] B. Other Embodiments (B1) In the above embodiment, the plunger tip 100 includes the cast iron rings 121 and 122 having a ring shape, but the present disclosure is not limited thereto. The plunger tip 100 may include a cast iron ring having a C shape with a part of the outer periphery cut out. According to such a configuration, even if the chip body 110 is formed as an integral member, the cast iron ring 121 can be assembled, so that the structure of the plunger tip 100 can be simplified and the manufacturing cost can be suppressed.

[0025] (B2) In the above embodiment, the plunger tip 100 includes two cast iron rings 121 and 122, but the present disclosure is not limited thereto. The plunger tip 100 may include three or more cast iron rings.

[0026] (B3) In the above embodiment, the cast iron ring 121 includes the groove G, but the present disclosure is not limited thereto. The cast iron ring 121 may not include the groove G.

[0027] (B4) In the above embodiment, the groove G is formed such that the longitudinal direction of the groove G is twisted with respect to the central axis M of the cast iron ring 121, but the present disclosure is not limited thereto. The groove G may be formed such that the longitudinal direction of the groove G is parallel to the central axis M of the cast iron ring 121.

[0028] (B5) In the above embodiment, the plunger tip 100 includes two cast iron rings 121 and 122, but the present disclosure is not limited thereto. The plunger tip 100 may include only the cast iron ring 121. Alternatively, an integral sleeve member that covers the entire outer peripheral surface of the chip body 110 may be provided as the cast iron ring.

[0029] (B6) In the above embodiment, the cast iron rings 121 and 122 are made of the same material as each other, but the present disclosure is not limited thereto. The cast iron rings 121 and 122 may be made of different materials from each other. According to such a configuration, the cast iron ring 122 that is less likely to wear compared to the cast iron ring 121 is formed of a material that is less expensive than the material forming the cast iron ring 121, whereby the manufacturing cost of the plunger tip 100 can be suppressed.

[0030] The present disclosure is not limited to the above-described embodiments, and can be realized in various configurations without departing from the gist thereof. For example, the technical features in the embodiments corresponding to the technical features in each form described in the summary of the invention can be appropriately replaced or combined in order to solve some or all of the above-described problems, or to achieve some or all of the above-described effects. Further, if the technical feature is not described as essential in this specification, it can be appropriately deleted.

Explanation of Reference Numerals

[0031] 10... cavity, 100... plunger tip, 110... chip body, 111... body member, 112... body member, 121, 122... cast iron rings, 200... plunger rod, 300... injection sleeve, 400... fixed mold, 500... movable mold, 1000... die casting device, C... screwing portion, G... groove, L, M... central axis

Claims

A plunger tip for die casting, which is used reciprocally while sliding inside an injection sleeve provided with a powder lubricant containing graphite, comprising: a tip body; a cast iron ring mounted on the outer periphery of the tip body, having an outer diameter larger than the outer diameter of the tip body, and forming a sliding surface with the injection sleeve; and; the average particle diameter of the graphite contained in the spheroidal graphite cast iron forming the cast iron ring is larger than the average particle diameter of the powder lubricant; the cast iron ring is provided with a groove on its outer peripheral surface; the groove is formed linearly; the longitudinal direction of the groove is formed to be in a twisted position with respect to the central axis of the cast iron ring; one end of the groove reaches the end face on the side far from the cavity in the reciprocating direction of the plunger tip among the both end faces in the central axis direction of the cast iron ring, and the other end does not reach any end face of the cast iron ring; a plunger tip.

2. The plunger tip according to claim 1, comprising: a plurality of the cast iron rings arranged side by side in the reciprocating direction of the plunger tip. a plunger tip.

3. The plunger tip according to claim 2, wherein: the plurality of cast iron rings are formed of the same material. a plunger tip.

4. The plunger tip according to claim 1, comprising: a plurality of the cast iron rings arranged side by side in the reciprocating direction of the plunger tip; among the plurality of cast iron rings, the cast iron ring closest to the cavity in the reciprocating direction of the plunger tip is provided with the groove on its outer peripheral surface. a plunger tip.

5. The plunger tip according to claim 1 or claim 2, wherein: the average particle diameter of the graphite is 1.5 times or more the average particle diameter of the powder lubricant. a plunger tip.

6. The plunger tip according to claim 5, wherein: the average particle diameter of the graphite is 30 μm or more. a plunger tip.

7. A die casting apparatus, comprising: an injection sleeve; a plunger tip for die casting, which is used reciprocally while sliding inside the injection sleeve; and a powder lubricant containing graphite provided between the injection sleeve and the plunger tip; and; the plunger tip comprises: a tip body; It has a cast iron ring that is mounted on the outer periphery of the chip body, has an outer diameter larger than the outer diameter of the chip body, and forms a sliding surface with the injection sleeve. The average particle size of the graphite contained in the spheroidal graphite cast iron forming the cast iron ring is larger than the average particle size of the powder lubricant. The cast iron ring is provided with a groove on its outer peripheral surface. The groove is formed linearly. The longitudinal direction of the groove is formed so as to be in a twisted position with respect to the central axis of the cast iron ring. One end of the groove reaches the end face on the side far from the cavity in the reciprocating direction of the plunger chip among the both end faces in the central axis direction of the cast iron ring, and the other end does not reach any end face of the cast iron ring. Die casting device.

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