JP6029444B2 - Mold for casting - Google Patents

Description

  The present invention relates to a casting mold particularly suitable for casting a light metal such as an aluminum alloy by a gravity casting method or a low pressure casting method.

  When a cast product such as a cylinder of an engine is formed from an aluminum alloy, for example, a gravity casting method or a low pressure casting method is generally employed. For example, when a relatively large casting such as the above cylinder is manufactured by the gravity casting method, the molten metal from the hot water supply port is divided and supplied to a branch path branched into a plurality from the branch point in the runner. Then, it is injected into the cavity from a plurality of inlets. As a result, the molten metal is supplied to the cavity and the solidification in the cavity is facilitated.

  As a material of the casting mold used in the above-described gravity casting method, an SKD material (steel for hot working) is generally used. However, a casting mold made of this SKD material is a molten high temperature. Because of its chemical affinity with molten aluminum, it is easy to cause melting damage. Conventionally, as a countermeasure, tungsten is used for a metal forming mold (see Patent Document 1) in which a mold material is formed of a tungsten-based metal sintered body containing 85 to 98% by weight of tungsten, or for a pouring gate for pouring molten metal into a cavity. A casting apparatus (see Patent Document 2) equipped with a sprue bush formed of an alloy has been proposed.

JP-A-5-354 Japanese Utility Model Publication No. 62-155950

  However, in the casting mold provided with the above-described runners having a plurality of branch paths, the upstream side of the branch point flows into a plurality of branch paths and the amount of melt that can be supplied is flowing. The large amount of molten metal rebounds at the branching point and directly hits the upstream side thereof, so that the upstream side of the branching point easily receives the heat from the high-temperature molten aluminum and is present at this point. There is a tendency for solidification of the molten metal to be delayed. For this reason, when the mold is opened after molding, welding that is not sufficiently solid existing upstream of the branch point in the runner adheres to the sliding surface of the mold, galling, etc., and smooth mold opening occurs. Hinder.

  As a countermeasure against the above-mentioned problems, the technique of Patent Document 1 can prevent welding and caulking of runners. However, tungsten is expensive and has low toughness and is liable to be cracked or chipped. Since it is difficult to replace the entire mold even if it is partially damaged, it is not preferable in terms of cost to apply it to a casting mold for a relatively large casting such as an engine cylinder. On the other hand, the sprue bush for low-pressure casting in Patent Document 2 can be effectively used as a sprue bush for flowing molten metal from the runner into the cavity, but eliminates the influence of heat from the melt on the upstream side of the branch point in the runner. I can't do it.

  Therefore, the present invention provides a casting mold capable of improving the heat resistance of the upstream side of the branch point in the runway and sufficiently suppressing the occurrence of melting damage due to welding or galling. Objective.

  In order to achieve the above object, a casting mold according to the present invention includes a cavity and a runner that supplies a molten metal to the cavity, and the runway has a plurality of molten metals from a hot water inlet toward the cavity. A branch point that branches into the branch path is formed, and the upstream side of the branch point is formed by a branch portion forming body made of a tungsten alloy separately from the mold body.

  According to this casting mold, the tungsten alloy, which is a mold material of the branch portion forming body that is provided separately from the mold body and forms the upstream side of the branch point in the runner, is strong and hard to heat. Since it has good heat conductivity and low wettability with respect to molten aluminum, the heat resistance is improved, so that the occurrence of melting damage due to welding or galling can be suppressed. In addition, tungsten alloys that have low toughness and are expensive are used only in the branch formation body that forms the upstream side of the branch point of the runway. Since it can be made, the toughness of the entire mold is not lowered, and an increase in cost can be suppressed, so that it can be applied to a casting mold of a large cast product.

  In the present invention, the mold body includes a fixed mold and a pair of movable molds, and the branch portion forming body includes a pair of divided pieces, and the divided pieces face the split surfaces of the pair of movable molds. It is preferable that it is mounted on a movable mold. As a result, when the pair of movable molds is closed, the upstream side of the branch point that is a part of the runner can be easily formed by the pair of divided pieces that are mounted facing the split surfaces of the pair of movable molds. Is done. The split surface referred to here is a split surface between the movable molds, and is a surface that is brought into close contact with each other when the mold is closed.

  When the split pieces are attached to the movable molds facing the pair of movable mold split surfaces, the downstream end surface of the split pieces is in contact with the slide surface of the fixed mold for sliding the movable mold. Is preferred. As a result, the split piece that contacts the slide surface of the fixed mold is formed of a tungsten alloy having excellent heat resistance, so that the molten surface does not adhere to the split piece and the slide surface is not melted. Can be opened and closed.

  In the present invention, the branch portion forming body has an inlet through which the molten metal from the hot water inlet flows in one side, a molten metal outlet at the lower end, and degass the molten metal at the upper end. It is preferable to have a gas vent. As a result, the molten metal flows in from the hot water supply port on one side surface of the branch portion forming body and flows toward the outlet of the lower end portion, and at that time, the gas contained in the molten metal is transferred to the upper end portion of the branch portion forming body. Since the gas is smoothly discharged to the outside through the gas vent provided in the gas vent, gas can be smoothly vented particularly when casting by the gravity casting method.

  According to the present invention, the tungsten alloy, which is a mold material of a split piece that is provided separately from the mold body and forms the upstream side of the branch point in the runner, is strong and hard to heat, and has good thermal conductivity. In addition, since it has low wettability with respect to molten aluminum, heat resistance is improved, so that occurrence of melting damage due to welding or galling can be suppressed. In addition, because the tungsten alloy with low toughness and high price is used only for the split pieces that form the upstream side of the runoff point of the runner, the toughness of the entire mold is not lowered and the increase in cost can be suppressed. The present invention can also be applied to a casting mold for large castings.

(A), (b) is a schematic longitudinal cross-sectional view at the time of mold closing and mold opening of a casting mold according to an embodiment of the present invention. It is a top view except the upper mold of the casting mold same as the above. FIG. 3 is a view taken along line III-III in FIG. 2. It is a perspective view which shows the division | segmentation piece in the metal mold | die for casting same as the above.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. 1 (a) and 1 (b) are schematic longitudinal sectional views respectively showing a state when the casting mold according to an embodiment of the present invention is closed and when the mold is opened. It has a mold body 1 and a branch portion forming body 2. The mold body 1 includes a fixed mold 3 fixed on a base base 8 and a pair of movable molds 4A and 4B provided on the upper surface of the fixed mold 3 so as to be slidable. The branch portion forming body 2 is composed of a pair of divided pieces 2A and 2B. An upper mold 9 is connected to the upper surfaces of the pair of movable molds 4A and 4B.

  The pair of movable molds 4A and 4B of the mold body 1 is formed of an SKD material as in the conventional case. The pair of divided pieces 2A and 2B are formed of tungsten alloy separately from the movable molds 4A and 4B of the mold body 1, and are attached to the mounting recesses formed on the split surfaces 14a and 14b of the pair of movable molds 4A and 4B. 24a and 24b are fitted and fixed to the movable molds 4A and 4B by fixing means described later. In this state, the opposing inner surfaces of the pair of split pieces 2A and 2B are flush with the split surfaces 14a and 14b. In this case, in the pair of divided pieces 2A and 2B, the downstream end surfaces 25a and 25b which are the bottom surfaces thereof are in contact with the slide surface 3a on the fixed die 3 together with the movable dies 4A and 4B.

  FIG. 2 is a plan view of the casting mold with the upper mold 9 removed, which shows a relatively large cast product, for example, a mold for casting a motorcycle engine cylinder with aluminum. Has been. A cavity CA for casting a cast product and a molten aluminum in the mold body 1 from above are provided on both sides of the closely-fitting split surfaces 14a and 14b of the pair of movable molds 4A and 4B which are closed. A hot water supply port 10 to be supplied and a runner 11 to supply molten aluminum from the hot water supply port 10 to the cavity CA are formed.

  The runner 11 has an inlet passage 110 that extends downward from the hot water inlet 10, and runner branch passages 111 and 112 that branch from the inlet passage 110 in two directions in the horizontal direction. The molten metal is injected into the cavity CA from the runner branch paths 111 and 112 through the respective gates 12a and 12b. The inlet passage 110 is formed between the movable molds 4A and 4B, and the runner branch paths 111 and 112 are formed between the movable molds 4A and 4B and the fixed mold 3.

  As shown in FIG. 1, a branch point 13 for branching the runner 11 into two runner branch paths 111 and 122 is formed by a groove-like recess formed in the fixed mold 3, and the upstream side of the branch point 13. The portion is formed by a pair of divided pieces 2A and 2B attached to the movable molds 4A and 4B constituting the branch portion forming portion 2. The divided pieces 2A and 2B are substantially symmetrical with respect to the split surfaces 14a and 14b of the movable dies 4A and 4B, and are formed into a rectangular plate as a whole by a tungsten alloy as shown in FIG. This tungsten alloy is, for example, a tungsten-based metal sintered body containing 97% by weight of tungsten. The split pieces 2A and 2B have inlet half portions 18a and 18b for forming an inlet 18 which will be described later on one side (the right side in the figure), and an outlet 19 which will be described later at the lower end. It has outlet half portions 19a and 19b for forming, and further has communication passage half portions 20a and 20b that form a communication passage 20 that communicates the inlet 18 with the outlet 19, and a gas vent at the upper end. Degassing port halves 21 a and 21 b for forming 21 are provided.

  As shown in FIG. 2, when the pair of movable molds 4 </ b> A, 4 </ b> B are closed, the inlets 18 through which the inlet halves 18 a, 18 b are combined to flow in the molten aluminum from the hot water inlet 10. The outlet half portions 19a and 19b are combined to form the outlet 19 for discharging the molten metal toward the branch point 13, and the communication passage halves 20a and 20b are combined to flow through the inlet 18. A communication passage 20 that communicates with the outlet 19 is formed, and the gas vent ports 21 that degas the molten metal are formed by combining the gas vent half halves 21a and 21b.

  The pair of divided pieces 2A and 2B are bolts 29 which are a kind of fastening members inserted into the insertion holes 54a and 54b of the movable molds 4A and 4B in a state of being positioned with respect to the movable molds 4A and 4B by the positioning pins 28. Are mounted on the movable molds 4A and 4B by being screwed into the female screw holes 22a and 22b formed in the divided pieces 2A and 2B.

  FIG. 3 shows an arrow view taken along line III-III in FIG. 2, that is, an arrow view of the movable mold 4A viewed from the crack surface 14a side. As shown in FIG. 2, a positioning hole 23a into which the positioning pin 28 shown in FIG. 2 is fitted is formed on the back surface of the one split piece 2A opposite to the split surface 14a. Four of the illustrated female screw holes 22a are formed. Similarly, one positioning hole 23b shown in FIG. 2 and four female screw holes 22b shown in FIG. 2 are formed on the back surface of the other divided piece 2B.

  The fixed mold 3 is fixed on the base table 8 by a plurality of bolts 30. A center pin 31 is fixed to the fixed mold 3 and a push pin 33 is disposed so as to freely advance and retract. A cavity CA is formed around the center pin 31 in the mold body 1. The upper die 9 is inserted with a gas vent pin 35 for venting a core (not shown) during casting from the upper die 9 to the upper part of the cavity CA.

  In this casting mold, when molten aluminum is introduced into the hot water supply port 10 in a closed state, the molten metal is introduced into the inlet 18 formed in the branch passage formation body 2 from the inlet passage 110, the communication passage 20, and After flowing out to the branch point 13 through the outlet 19, the two runner branches 111, 112 flow separately, and are filled into the cavity CA from the gates 12 a, 12 b of the runner branches 111, 112. . After the molten metal filled in the cavity CA solidifies, the upper mold 9 is pulled up, and then the pair of movable molds 4A and 4B are slid open as shown in FIG. The casting product (cylinder) is pushed up by the advance of the arranged push pin 33 and is taken out from the mold body 1. When the mold is opened and closed, the lower surface of the movable mold 4A (4B) and the end face 25a (25b) on the downstream side of the split piece 2A (2B) slide on the slide surface 3a on the fixed mold 3.

  In this casting mold, the upstream side of the branch point 13 in the runner 11 of FIG. 3 is formed by the branch portion forming body 2 provided separately from the mold body 1, and the material of the branch portion forming body 2 is formed. Tungsten alloy is strong against heat and hard, and also has good thermal conductivity and low wettability to molten aluminum, so heat resistance is improved, so melting damage caused by welding and galling Can be suppressed. Tungsten alloys are expensive, have low toughness, are prone to cracking and chipping, and are difficult to repair, so if the entire mold is made of tungsten alloy, the entire mold will be damaged even if it is partially damaged. Since replacement is necessary, it is not preferable in terms of cost. On the other hand, in the said embodiment, the tungsten alloy is only used as a raw material of the branch part formation body 2 which forms the upstream of the branch point 13 of the runner 11, and the branch part formation body in a metal mold | die Most of the parts except 2 are made of SKD material, which is steel with high toughness, so the toughness of the entire mold is not lowered and the increase in cost can be suppressed. It can also be applied to.

  Moreover, the branch part formation body 2 consists of a pair of division | segmentation piece 2A, 2B shown to Fig.1 (a), and division | segmentation piece 2A, 2B faces each split surface 14a, 14b of a pair of movable mold | type 2A, 2B, respectively. Since the molds 4A and 4B are mounted, when the pair of movable molds 4A and 4B is closed, the pair of divided pieces 2A mounted facing the split surfaces 14a and 14b of the movable molds 4A and 4B. , 2B, the upstream side of the branch point 13 which is a part of the runner 11 is easily formed.

  Furthermore, the end faces 25a and 25b on the downstream side of the split pieces 2A and 2B of the branch portion forming body 2 slide in contact with the slide surface 3a in the fixed mold 3 on which the movable molds 4A and 4B are slid. Since the branch portion forming body 2 that forms the upstream side of the branch point 13 is made of a tungsten alloy that has low wettability with aluminum and excellent heat resistance, the downstream side in contact with the slide surface 3a of the fixed mold 3 Since galling or molten metal hardly occurs on the end faces 25a and 25b, the movable molds 4A and 4B can be opened and closed smoothly.

  Also, the pair of split pieces 2A and 2B shown in FIG. 3 are combined with each other when the mold is closed, so that an inlet 18 into which the molten metal from the hot water inlet 10 flows is formed on one side, and the molten metal outlet 19 Is formed at the lower end, and a melt vent 21a is formed at the upper end. Therefore, the molten metal from the hot water supply port 10 is included in the molten metal in the process of flowing into the inlet 18 formed by one side of each of the pair of split pieces 2A and 2B and flowing toward the outlet 19 at the lower end. Since the gas to be discharged is smoothly discharged to the outside from the gas vent 21 formed at the upper end portion of the branch portion forming body 2, in particular, casting by the gravity casting method in which the molten metal is injected into the cavity CA from the lower portion is performed. In this case, the gas can be smoothly vented.

  In addition, although the case where the runway 11 has the two runner branch branches 111 and 112 was illustrated in the said embodiment, you may have three or more runner branch branches. The present invention is not limited to the above-described embodiment, and various additions, modifications, or deletions are possible without departing from the spirit of the present invention, and such modifications are also included in the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Mold main body 2 Branch part formation body 2A, 2B Split piece 3 Fixed mold | type 3a Slide surface 4A, 4B Movable type 10 Hot water inlet 11 Runway 13 Branch point 14a, 14b Split surface 18 Inlet 19 Outlet 21 Gas vent 25a , 25b End face 33 on the downstream side Extrusion pin 33
111, 112 Branch CA cavity

Claims (3)

A cavity and a runner for supplying molten metal to the cavity,
The runway has a branch point that branches the molten metal from the hot water supply port into a plurality of branch paths toward the cavity,
The upstream side of the branch point is formed by a branch portion forming body made of a tungsten alloy separately from the mold body,
The mold body includes a fixed mold and a pair of movable molds, and the branch portion forming body includes a pair of divided pieces, and the divided pieces are attached to the movable molds so as to face the split surfaces of the pair of movable molds. The casting mold. 2. The casting mold according to claim 1 , wherein an end face on the downstream side of the divided piece is in contact with a slide surface that slides the movable mold in the fixed mold. 3. A cavity and a runner for supplying molten metal to the cavity,
The runway has a branch point that branches the molten metal from the hot water supply port into a plurality of branch paths toward the cavity,
The upstream side of the branch point is formed by a branch portion forming body made of a tungsten alloy separately from the mold body,
The branch portion forming body has an inlet through which the molten metal from the hot water inlet flows on one side, a molten metal outlet at the lower end, and a gas vent for venting the molten metal at the upper end. Has a casting mold.

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