Valve body and method of manufacturing a valve body
By creating weir marks and staggering the pouring gates during the casting process of the valve body, the directional solidification of the molten metal at the neck root is promoted, the shrinkage cavity problem is solved, high-precision casting is achieved, and processing costs are reduced.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- KITZ CORP
- Filing Date
- 2021-06-30
- Publication Date
- 2026-07-10
AI Technical Summary
Shrinkage cavities are prone to occur at the neck root of valve bodies, especially ball valves or butterfly valves, during casting, resulting in a decrease in yield and additional processing time and costs due to existing technologies.
By forming a weir mark on the cylindrical surface of the valve body during casting, making the first region between it and the neck root thicker, and gradually narrowing its width from the neck root, and by staggering the pouring gate and neck position during casting, the height of the molten metal channel is gradually reduced to promote directional solidification.
It effectively suppressed the formation of shrinkage cavities at the neck root, reduced casting defects, simplified subsequent processing steps, and lowered manufacturing costs.
Smart Images
Figure CN113864501B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a valve body capable of suppressing the generation of casting defects and a method for manufacturing the valve body. Background Technology
[0002] The valve body is a pressure vessel, so it is mainly manufactured by casting metal.
[0003] In particular, when the main body of a valve, such as a ball valve or butterfly valve, is manufactured by casting (where the neck protrudes from the generally cylindrical body to form a shaft-mounted part, and packing or a handle is placed on the shaft-mounted part to enable the valve body to open and close), a casting defect called shrinkage cavity is easily generated at the root of the neck, which is the cause of a decrease in yield when casting the main body.
[0004] In casting, when molten metal poured into a mold cools and begins to solidify, its volume shrinks. The molten metal fills the shrinking area from the surrounding area, but at the final solidified portion (the last part to solidify), it cannot be filled from the surrounding area. Therefore, the shrunken portion remains as a void, becoming a shrinkage cavity. In valve bodies where a shank is provided, with the neck protruding from the generally cylindrical body, the upper part of the body and the root of the neck form an L-shaped intersection. Because this intersection is difficult to cool and solidify, it easily becomes the final solidified portion, resulting in shrinkage cavities easily forming at this intersection.
[0005] No matter what kind of metal material is used to cast the main body, it is difficult to completely prevent the formation of shrinkage cavities. In the main body of stainless steel cast steel products (SCS) made of stainless steel, there is almost no volume expansion caused by graphite crystallization when stainless steel is cooled and solidified, so it is particularly prone to shrinkage cavities.
[0006] As a technique for preventing casting defects such as shrinkage cavities, a main body body with a neck protruding from a generally cylindrical main body and a shaft mounting portion is cast. For example, Patent Document 1 discloses a ball valve box casting with the following: a gate is directly provided in the shaft mounting portion located approximately in the center of the main body, and the wall thickness of the shaft mounting portion is maintained at or above the minimum wall thickness of the main body to allow the molten metal to solidify in a directional manner, thereby preventing the formation of shrinkage cavities at the intersection formed by the upper part of the main body and the root part of the shaft mounting portion.
[0007] [Existing Technical Documents]
[0008] [Patent Documents]
[0009] [Patent Document 1] Japanese Patent Application Publication No. 5-50209. Summary of the Invention
[0010] [The problem the invention aims to solve]
[0011] However, the ball valve box casting disclosed in Patent Document 1 has a gate directly provided in the shaft mounting part located approximately in the center of the main body. Therefore, when the ball valve is removed from the mold (in the as-cast state), a gate portion remains in the upper part of the shaft mounting part, and the shaft mounting part is formed in a solid state.
[0012] Therefore, after being removed from the mold, not only is the gate portion directly provided on the shaft assembly cut off, but also, if machining is not performed to form an insertion through hole for inserting the through valve stem into the shaft assembly, or a step portion or groove portion for assembling seals, a usable main body cannot be obtained. As a result, the manufacturing cost increases due to the corresponding increase in machining time.
[0013] The present invention was developed to address the aforementioned issues, and its purpose is to provide a valve body with excellent castability by appropriately controlling the solidification process from the gate used for casting to the neck in a valve body manufactured by casting, suppressing the formation of shrinkage cavities.
[0014] [Methods for solving problems]
[0015] To achieve the above objectives, the invention involved in technical solution 1 is a valve body, which is a main body having a shaft-mounted portion that causes the neck to protrude in a cross direction relative to the cylindrical body. The invention is characterized in that: the trace of the weir portion, which serves as the pouring gate during casting, is formed in a raised state on the cylindrical surface of the main body, and the wall thickness of the first region, which extends from the trace of the weir portion to the neck, is formed to be thicker than the wall thickness of other regions of the main body. Furthermore, the wall thickness of the first region, which is formed to be thicker, gradually thins from the trace of the weir portion toward the root portion of the neck.
[0016] The invention involved in technical solution 2 is a valve body formed in which the wall thickness of the main body of the first region is at least thicker than that of the root region of the neck.
[0017] The invention involved in technical solution 3 is a valve body in which the width of the first region is formed as gradually narrowing from the trace of the weir towards the root of the neck.
[0018] The invention involved in technical solution 4 is that the traces of the weir are formed into a valve body that is wider than the root part of the neck.
[0019] The invention involved in technical solution 5 is a method for manufacturing a valve body, which is a method for manufacturing a valve body having a shaft-mounted portion that causes the neck to protrude in a cross direction relative to the cylindrical body. The method is characterized in that: the pouring gate formed when forming a casting mold is offset from the position that becomes the neck, and the height of the molten metal channel in the first region from the pouring gate to the position that becomes the root of the neck is formed to be higher than the height of other regions. The height of the molten metal channel gradually decreases from the pouring gate toward the position that becomes the root of the neck, thereby suppressing shrinkage cavities generated in the valve body when casting using a mold.
[0020] [The effects of the invention]
[0021] According to the invention involved in technical solution 1, the wall thickness of the first region, which is the area between the weir mark and the neck, is formed to be thicker than the wall thickness of other regions of the main body. Furthermore, the wall thickness of the first region, which is formed to be thicker, gradually thins from the weir mark toward the root of the neck. Therefore, the root of the neck becomes less likely to become the final solidification point during casting, thereby suppressing the generation of casting defects such as shrinkage cavities that were previously prone to occur at the root of the neck of the main body.
[0022] In addition, the wall thickness of the first region is made thicker than that of the surrounding cylindrical surface, which promotes the directional solidification of the molten metal from the root of the neck toward the weir mark (pour gate) during casting and suppresses the generation of casting defects such as shrinkage cavities at the root of the neck.
[0023] According to the invention involved in technical solution 2, the wall thickness of the main body of the first region is formed to be at least thicker than the wall thickness of the root region of the neck. Therefore, during casting, the solidification of the molten metal at the root region of the neck is generated faster than that of the molten metal in the first region. Thus, the root region of the neck will not become the final solidification point, thereby suppressing the generation of casting defects such as shrinkage cavities at the root region of the neck.
[0024] According to the invention involved in technical solution 3, the width of the first region is formed to gradually narrow from the mark of the weir toward the root of the neck, thus making it easier to promote the directional solidification of the molten metal from the root of the neck toward the weir during casting, and more effectively suppressing the generation of casting defects such as shrinkage cavities at the root of the neck.
[0025] According to the invention involved in technical solution 4, the trace of the weir is formed to be wider than the root part of the neck. Therefore, the solidification of the molten metal in the weir is later than that in the main body, making it easier to generate the final solidified part of the molten metal in the weir. Thus, casting defects such as shrinkage cavities are difficult to generate not only in the root part of the neck but also in the entire main body. In addition, molten metal can be efficiently fed from the weir into the mold of the valve body during casting.
[0026] According to the invention described in technical solution 5, casting is performed using a mold formed as follows: the pouring gate (weir) is offset from the neck position, and the height of the molten metal channel in the first region from the pouring gate to the root of the neck is higher than the height of other regions; the height of the molten metal channel gradually decreases from the pouring gate towards the root of the neck. Therefore, it is easier to directionally solidify the molten metal from the root of the neck towards the weir, and the formation of shrinkage cavities at the root of the neck can be more effectively suppressed.
[0027] Furthermore, if the valve body is cast using this manufacturing method, a flawless body can be obtained by applying only minimal processing to the main body after separation casting at the weir, without increasing processing time. Attached Figure Description
[0028] Figure 1 This is a perspective view showing an embodiment of the valve body of the present invention.
[0029] Figure 2 Is with Figure 1 The flow path of the valve body is at a right angle in the cross-section.
[0030] Figure 3 This demonstrates casting via the lost-wax casting method. Figure 1 An example diagram of a wax tree (wax tree) for the valve body.
[0031] Figure 4 (a) is a diagram of the body mold used in the previous valve body casting method. Figure 4 (b) is a diagram of the body mold used in the casting method of the valve body of the present invention.
[0032] Figure 5 This is a schematic diagram illustrating the solidification process of the molten metal poured into the body mold in the casting method of the valve body of the present invention. Detailed Implementation
[0033] The following describes in detail, based on the accompanying drawings, one embodiment of the valve body of the present invention and its manufacturing method. Figure 1 This is a perspective view showing the appearance of the main body of a ball valve, which is one embodiment of the valve body in this invention. Figure 2 Is with Figure 1 The flow path of the main body of the ball valve is perpendicular to the cross-section.
[0034] in accordance with Figure 1The main body 1 has a shaft-mounted portion 4 that makes the cylindrical neck 3 protrude in a cross direction relative to the cylindrical body 2. On the cylindrical surface 5 of the main body 2, the weir 6, which serves as a trace of the pouring gate during casting (hereinafter referred to as "weir 6" for convenience), is formed in a raised state, and a first region 7 that is raised from the cylindrical surface 5 is formed between the weir 6 and the neck 3.
[0035] In addition, the weir 6 is wider than the root portion 8 of the neck 3, and the width of the first region 7 gradually increases from the root portion 8 of the neck 3 toward the weir 6.
[0036] Furthermore, based on Figure 2 The wall thickness of the main body 2 of the first region 7 between the weir 6 and the neck 3 is formed to be at least thicker than the wall thickness of the root portion 8 of the neck 3, that is, thicker than the wall thickness of other regions of the main body 2. The wall thickness of the main body of the first region 7 in the state of being thicker is formed to gradually thicken from the root portion 8 of the neck 3 toward the weir 6.
[0037] Additionally, by setting the first region 7, thus achieving... Figure 2 As shown, the wall thickness of the main body 2 in the first region 7 is thicker than the wall thickness of other regions of the main body 2, and gradually increases from the root portion 8 of the neck 3 towards the weir portion 6, and as... Figure 1 As shown, the width of the first region 7 also gradually increases from the root part 8 of the neck 3 toward the weir part 6.
[0038] Therefore, the wall thickness of the first region 7 gradually increases from the root portion 8 of the neck 3 towards the weir 6, and the width of the first region 7 gradually increases from the root portion 8 of the neck 3 towards the weir 6. Furthermore, Figure 2 The weir 6 is the part that remains after casting when the main body 1 is separated from the flow channel at the weir part. Therefore, the thickness of the weir 6 during casting is thicker than the wall thickness of the first region 7.
[0039] Thus, in the valve body of the present invention, as Figure 2 The wall thickness of the main body of the first region 7 shown is thicker than that of the root portion 8 of the neck 3. As a result, the main body of the first region 7 becomes more difficult to cool during casting than other parts. Therefore, at least the root portion 8 of the neck 3 cools faster than the main body of the first region 7, thus preventing the root portion 8 of the neck 3 from becoming the final solidified part and producing shrinkage cavities.
[0040] Furthermore, the first region 7 is connected to the weir 6 in a state where the wall thickness and width gradually increase from the root portion 8 of the neck 3 toward the weir 6. Therefore, when cooling the molten metal, directional solidification from the root portion 8 of the neck 3 toward the weir 6 is promoted, and it becomes easier to generate the final solidified portion of the molten metal in the weir 6. Thus, the generation of shrinkage cavities can be suppressed not only at the root portion 8 of the neck 3, but also throughout the entire body 1.
[0041] Next, regarding the manufacturing method of the valve body of the present invention, the method of casting the main body of the ball valve described above using the lost-wax casting method will be described with reference to the accompanying drawings.
[0042] In the valve body manufacturing method of the present invention, a body casting mold for body casting is used in such a way that the pouring gate during casting is offset from the position that becomes the neck, and the height of the molten metal channel in the first region from the pouring gate to the position that becomes the root of the neck is formed to be higher than the height of other regions, and the height of the molten metal channel gradually decreases from the pouring gate toward the position that becomes the root of the neck.
[0043] When manufacturing the valve body using such a main body mold by the lost-wax casting method, a wax prototype 14 of the main body is first manufactured. The wax prototype 14 has the same shape as the main body to be manufactured, except for the weir that is provided on the surface of the main body to serve as the pouring gate during casting. It is manufactured using a predetermined mold and core and using wax pattern.
[0044] After manufacturing the required number of the wax prototypes 14, manufacture as shown in Figure 3 The wax tree 11 is illustrated in the example. Regarding the wax tree 11, the part 12 that will become the gate and the part 13 that will become the runner are prepared in advance using molding wax. The wax prototype 14 is joined to the part 13 that will become the runner by a weir (not shown) using a soldering iron or adhesive wax to form a tree shape.
[0045] Next, a material (such as ceramic) to serve as a mold is attached to the surface of the wax tree 11. After coating treatment and drying, the wax tree inside is melted at high temperature to remove the wax, forming a mold with an internal space having the same shape as the wax tree. Subsequently, the mold is fired as needed to complete the casting process. The same number of main body molds as the wax prototype 14 used are formed in this casting mold.
[0046] The resulting casting mold is filled with molten metal from the gate, containing the raw materials for the main body (stainless steel, cast iron, brass alloy, etc.). The molten metal flows through the runner and weir into each of the multiple main body molds. After the molten metal cools and solidifies, the casting mold is broken by vibration, impact, or other means to remove the internal casting. A casting with the same shape as the wax tree can be obtained. If the cast main body is separated from this casting at the weir, the main body of the ball valve, cast in a predetermined shape, can be obtained.
[0047] In the above-described casting of the main body using the lost-wax casting method, molten metal is introduced from the gating point into the runner within the casting mold, and then poured into the main body mold via the weir. Figure 4 In the previous main body mold 15 shown in (a), a casting space 16 is formed with a cylindrical main body having a substantially constant wall thickness, and a casting space 17 is formed with a cylindrical shaft mounting portion having a substantially constant wall thickness. The connection between the casting space 16 and the casting space 17 is an L-shaped intersection 18. In addition, the weir 19 is provided at a position 90° rotated circumferentially from the position 20 that becomes the neck root.
[0048] As mentioned earlier, in casting, such intersections 18 are difficult to cool and solidify, and tend to become the final solidified part, thus tending to produce casting defects such as shrinkage cavities 21 in the final solidified part. This is because if the molten metal is cooled and begins to solidify, its volume shrinks, and the shrunken part is filled by the surrounding molten metal. The same phenomenon occurs sequentially as the molten metal solidifies. Therefore, the final solidified part cannot be filled by the surrounding molten metal, and the shrunken part remains as a void.
[0049] In this regard, in the manufacturing method of the valve body of the present invention, as follows: Figure 4 As shown in (b), the main body mold 25 is formed in such a way that the pouring gate (weir 26) during casting is offset from the root portion 27 of the neck, and the height of the pouring channel (pouring space) 31 of the first region 30 from the pouring gate to the root portion 27 of the neck is formed higher than the height of the pouring space of other regions, and the height of the molten metal channel 31 gradually decreases from the pouring gate toward the root portion 27 of the neck.
[0050] Therefore, when molten metal is poured from the weir 26 into the casting space within the main mold 25, and then as the molten metal is cooled and solidified sequentially, directional solidification of the molten metal can be promoted from the root portion 27 of the neck towards the weir 26. As a result, the intersection that would previously easily become the final solidification point will not become the final solidification point, thus suppressing the generation of casting defects such as shrinkage cavities that are prone to occur in that part.
[0051] Furthermore, in the main body mold 25 used in the valve body manufacturing method of the present invention, the weir 26 is positioned closer to the root portion 27 of the neck than a position rotated 90° in the circumferential direction of the main body cylinder from the root portion 27 of the neck. By positioning the weir 26 close to the root portion 27 of the neck, molten metal can be rapidly fed into the casting space from the pouring port of the main body mold 25, i.e., the weir 26, to the root portion 27 of the neck. This allows the molten metal to solidify earlier than other parts, and facilitates the replenishment of molten metal from the weir 26 to the neck during solidification shrinkage. Consequently, it is easier to suppress the formation of shrinkage cavities at the root portion 27 of the neck.
[0052] In particular, regarding the main body mold 25 used in the manufacturing method of the valve body of the present invention, there is no obvious intersection except for the root portion 27 of the neck. Therefore, the thickest weir portion 26 is prone to become the final solidification portion, which can cause casting defects such as shrinkage cavities to occur in the weir portion 26. Therefore, after the molten metal has completely solidified, when separating the main body from the casting after removing it from the casting mold, if the separation is performed at the weir portion in a manner that no shrinkage cavities remain in the weir portion of the main body, a high-precision cast main body can be obtained.
[0053] In the lost-wax casting process, the same molds are used to make wax prototypes. Therefore, the weir of all wax prototypes is set closer to the root of the neck than the position where the main body cylinder is rotated 90° in the circumferential direction from the position that becomes the root of the neck. This allows the molten metal to be quickly fed into the root of the neck of all the main bodies to be cast, so that the molten metal solidifies earlier than other parts, thus making it easier to suppress the formation of shrinkage cavities at the root of the neck.
[0054] The following is based on Figure 5 (a) through (e) illustrate in more detail the solidification process of the molten metal poured into the main mold 25. In the figures, the shaded areas marked by diagonal lines from the upper right to the lower left represent the molten metal that has not yet solidified, and the shaded areas marked by diagonal lines from the upper left to the lower right represent the molten metal that has cooled and solidified.
[0055] As shown in (a), if molten metal is poured into the main mold 25 via the flow channel of the casting mold (not shown) to the pouring port, i.e. the weir 26, of the main mold 25 as indicated by arrow 32, the molten metal flows into the bottom side of the main mold 25 through the molten metal channels 31 and 33 within the main mold 25 as indicated by arrows 34 and 35.
[0056] Next, as shown in (b), the molten metal 37 flowing into the bottom side of the main mold 25 is cooled and solidified, and thus shrinks sequentially toward the bottom side of the mold as schematically shown by arrow 38.
[0057] As shown in (c), when the casting space and weir 26 within the main mold 25 are filled with molten metal, the height of the molten metal channel 31 within the main mold 25 is higher than the height of other areas, and the height of the molten metal channel 31 gradually decreases from the weir 26, which serves as the pouring port, toward the root portion 27 of the neck. As a result, the directional solidification of the molten metal poured within the main mold 25 from the root portion 27 of the neck toward the weir 26 is promoted.
[0058] Furthermore, specifically, when viewed in the thickness direction, the molten metal solidifies from near the surface and back (the contact surface with the mold), with the area near the center in the thickness direction solidifying last. Therefore, sometimes solidification occurs from the outside at the intersection of the root portion 27 of the neck, sealing off the area near the center. This prevents the replenishment of molten metal from the weir 26 to the area near the center, resulting in shrinkage cavities. In contrast, in this invention, the height of the molten metal channel 31 gradually increases from the root portion 27 of the neck towards the weir 26, making it less likely for the area near the center of the intersection to be sealed off by the solidified region, thus making it easier to suppress the formation of shrinkage cavities.
[0059] As a result, unsolidified molten metal 40 remains in the casting space above the main mold 25, which includes the weir 26, while the molten metal 41 in the casting space below it solidifies sequentially, as schematically shown by arrow 43, shrinking towards the bottom of the mold. Thus, the molten metal in the weir 26 solidifies last and becomes the final solidified portion, causing the molten metal 40 within the weir 26 to move from the weir 26 into the solidified portion within the main mold 25 to fill the shrinkage portion.
[0060] As shown in (d), when the molten metal in the main mold 25 is cooled and completely solidified, the weir 26, which becomes the final solidified part, cannot be filled with molten metal from the surrounding area, resulting in casting defects such as shrinkage cavities 45 and porosity 46 in the upper part of the weir 26.
[0061] However, by separating the cast main body at the weir 26 along the cutting line 47, the main body does not contain the parts that have cast defects, and thus, as shown in (e), a flawless main body without casting defects can be obtained.
[0062] Thus, according to the valve body manufacturing method of the present invention, a first region promoting directional solidification is provided on the cylindrical surface of the body from the root of the neck toward the weir, thereby solving the problem that casting defects such as shrinkage cavities are easily generated at the root of the neck (cross section) because the solidification of the molten metal during casting is later than that of the surrounding area. Therefore, a high-precision cast body can be obtained simply by separating the cast body at the weir without applying any additional processing.
[0063] There are no particular restrictions on the metal material used to manufacture the valve body of the present invention, as long as it is a castable metal material. In particular, stainless steel is a metal material that is easy to cool and solidify immediately in the mold because it needs to be cast at high temperature. In addition, there is almost no volume expansion caused by graphite crystallization during cooling and solidification. Therefore, it is a metal material that is easy to produce shrinkage cavities in the final solidified part. Therefore, stainless steel is particularly effective as a metal material suitable for the valve body and manufacturing method of the present invention.
[0064] Furthermore, while the description of the manufacturing method of the present invention exemplifies casting by the lost-wax casting method, the manufacturing method of the present invention is equally effective in preventing shrinkage cavities at the root of the neck when the valve body is manufactured by casting methods other than the lost-wax casting method.
[0065] In addition, the main body shape of the valve is not limited to a single-piece type as in this embodiment. In molds with two or more pieces, the thickness is gradually reduced from the gate to the intersection so that the intersection does not become the final solidification part, thereby suppressing the formation of shrinkage cavities.
[0066] Furthermore, in the above example, in the first region, an example is given where the wall thickness gradually decreases and the width gradually narrows from the weir towards the root of the neck. However, it is not necessary to satisfy both conditions; either the wall thickness or the width may gradually decrease. Alternatively, if the condition that the cross-sectional area of the first region gradually decreases from the weir towards the neck is met, even if the wall thickness and width of the first region do not gradually decrease, it may sometimes be possible to suppress the formation of shrinkage cavities at the root of the neck.
[0067] [Symbol Explanation]
[0068] 1 Main body
[0069] 2. Main Body
[0070] 3. Neck
[0071] 4. Shaft mounting section
[0072] 5. Cylindrical surface
[0073] 6. Traces of the weir
[0074] 7. First Area
[0075] 8. The base of the neck.
Claims
1. A valve body comprising a main body having a axially mounted portion such that its neck protrudes in a cross direction relative to the cylindrical main body, characterized in that: When casting the main body, the weir mark, which serves as the pouring gate during casting, is positioned closer to the root of the neck than the position 90° around the circumference of the main body cylinder from the root of the neck. This results in the weir mark being formed in a raised state on the surface of the main body cylinder. Furthermore, the wall thickness of the first region, from the weir mark to the neck, is thicker than the wall thickness of other regions of the main body. This thicker first region is formed such that the wall thickness gradually decreases from the weir mark towards the root of the neck.
2. The valve body according to claim 1, wherein, The wall thickness of the main body of the first region is formed to be at least thicker than that of the root portion of the neck.
3. A valve body comprising a main body having a axially mounted portion such that its neck protrudes in a cross direction relative to the cylindrical main body, characterized in that: When casting the main body, the trace of the weir, which serves as the pouring gate during casting, is formed in a raised state on the cylindrical surface of the main body. The wall thickness of the first region, which extends from the trace of the weir to the neck, is thicker than the wall thickness of other regions of the main body. The wall thickness of the first region, which is thicker, gradually decreases from the trace of the weir toward the root of the neck. Consequently, the width of the first region gradually decreases from the trace of the weir toward the root of the neck.
4. A valve body comprising a main body having a axially mounted portion such that its neck protrudes in a cross direction relative to the cylindrical main body, characterized in that: When casting the main body, the trace of the weir, which serves as the pouring gate during casting, is formed in a raised state on the cylindrical surface of the main body. The wall thickness of the first region, from the trace of the weir to the neck, is thicker than the wall thickness of other regions of the main body. The wall thickness of the first region, which is thicker, gradually thins from the trace of the weir toward the root of the neck, and the trace of the weir is wider than the root of the neck.
5. A method for manufacturing a valve body, comprising a valve body having a spool-mounted portion wherein the neck protrudes in a cross direction relative to the cylindrical body, characterized in that: The gating gate, when forming a casting mold, is located closer to the root of the neck than a position rotated 90° circumferentially from the root of the neck in the direction of the main body cylinder, and is offset from the position that becomes the neck. Thus, the gating gate is formed in a raised state on the surface of the main body cylinder, and the height of the molten metal channel from the gating gate to the position that becomes the root of the neck is higher than the height of other regions. The height of the molten metal channel gradually decreases from the gating gate toward the root of the neck, thereby suppressing shrinkage cavities in the valve body when casting using the mold.