JP2002178131A - Seal joining method with insert casting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a seal fused joining method, especially, suitable to parts, such as valve, with which a seal fused joining can be applied and working of a base material for screwing and calking, is unnecessitated and man-hour is reduced with the joining method with insert casting. SOLUTION: In a method for integrally joining a insert casting main material 1 and a material 2 by pouring molten metal into a mold disposing the material 2, this seal joining method, is characterized, in that both materials are integrally joined under the state of seal-fused joining at least a part of the material 2 and the main material 1 by regulating calorie supplied into the material 2 from the molten metal to not less than a calculated calorie when the molten metal is poured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a seal joining method by cast-in, and more particularly to a cast-in seal joining method in which a joint portion of a valve body and a seat ring is cast and melt-sealed.

[0002]

2. Description of the Related Art Valve seat rings of this type are formed by welding and dissimilar metals and then processed and finished to form a valve seat. This valve seat secures sealing properties, prevents galling, and loosens during use. Is an important condition, and loosening can cause leakage from behind the valve seat.

[0003] The body and the seat ring can be fixed to each other by screwing, caulking, or welding. The method of fixing the parts by fastening the components, such as the screwing or caulking, involves using a valve. Depending on the conditions, sheet leakage may occur, and the material must be machined with screws or the like, which increases man-hours and increases costs. On the other hand, in the case of the welding type, although the sealing property was good, the workability was extremely poor because the welding was performed in a narrow space.

[0004] In addition, various cast-in methods using different metals have been conventionally proposed, but none of these techniques can be said to be seal fusion joining of the valve body and the seat ring at the time of joining. For example, JP-A-11-19035
The technique described in Japanese Patent Application Publication No. 0 is a manufacturing method in which the volume ratio between the volume of the molten cast iron and the volume of the wrapping material is set to 18 or more. This is a technique for improving the strength by integrally joining the two and simplifying the manufacturing process.

[0005] The body of the valve, which is a pressure vessel, is formed of a thin body main body and a thick flange used for connection with piping and bonnet parts. A seat ring is provided on the thin body main body. Be placed. The wall thickness of the body body is determined in advance according to official standards, etc., and the thickness of the seat ring placement space is set to the minimum necessary thickness while securing the specified pressure resistance and strength in accordance with this. ing. The size of the space into which the molten metal flows directly affects only the vicinity of the seat ring arrangement space of the body main body, and the volume of the molten metal supplied to the space has a direct effect on the seal fusion bonding property between the seat ring and the valve body. Is only about 2-3 times the seat ring volume. Therefore, the technique disclosed in this publication cannot be applied to seal fusion joining in which the wall thickness is fixed and the space for disposing the seat ring is limited, such as a valve body that is a pressure vessel.

[0006]

SUMMARY OF THE INVENTION Accordingly, the present inventors have developed the present invention as a result of intensive studies in order to solve the conventional problems. Can be melt-bonded, and requires no material processing for screwing and caulking.
An object of the present invention is to provide a seal fusion joining method suitable for parts such as valves, in which the number of steps is reduced.

[0007]

In order to achieve the above object, the invention according to claim 1 is directed to a method in which a molten metal is poured into a mold provided with a body to be cast and a body to be cast and a body to be cast. In the method of integrally joining, at the time of pouring, at least the amount of the to-be-cast body and the said to-be-cast body by making the amount of heat supplied from the molten metal to the to-be-cast body equal to or more than the calorific value according to the following formula This is a seal joining method by cast-in in which both parts are integrally joined in a state where a part is melt-sealed. Heat amount = c × ρ × v × t / η c: Specific heat of the object to be cast ρ: Density of the object to be cast v: Volume of the object to be cast t: Solid phase temperature of the molten metal in the body of the object to be cast η: Thermal efficiency

[0008] The invention according to claim 2 is that the cast-in body is made of ductile cast iron and the cast-in body is made of a steel material such as stainless steel. This is a joining method in which both are integrally joined by supplying a heat amount of 15.0 × 10 ³ [J] or less to form a seal fusion joining portion.

According to a third aspect of the present invention, the seal joining portion of the object to be cast is a fin portion formed on the outer diameter of the ring-shaped object to be cast. The invention according to claim 4 is a seal joining method for preheating the body to be cast and supplementing the supply of heat to the body to be cast.

According to a fifth aspect of the present invention, there is provided a cast-in package wherein the cast-in body is a valve body, the cast-in body is a seat ring, and the seat ring and the valve body are joined by the above-mentioned seal joining method. Is a sealing joining method.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a seal joining method by cast-in in the present invention will be described in detail. FIG. 1 is a sectional view of a cast-in mold of the present invention, and FIG. 1 shows a sand mold (lower) in a mold for integrally joining a body 1 (a cast-in body) of a gate valve and a seat ring 2 (a cast-in body). The sand core 4 is set on the mold 3, and a pair of seat rings 2, 2 are provided on the guide mounting portions 5, 5 of the sand core 4.
And a sand core 4 to form a casting space 6. FIG.
Is a body 1 of the gate valve cast by the cast-in mold shown in FIG.

[0012] The cast body, which is the seat ring 2,
Stainless steel (SUS403, etc.) and structural alloy steel (SS
400 etc.) Other materials are used. In this example, ductile cast iron (spheroidal graphite cast iron) is used as the molten metal for molding the cast-in main body 1.

The molten cast iron, which is the cast-in body 1, is poured from a gate (not shown) and poured into the casting space 6 to form a mold. As shown in FIG. 5, a fin portion 7 having a triangular cross section is formed over the entire circumference of the seat ring 2 at an outer diameter position of the seat ring 2 opposite to the seat side 2a. The amount of heat can be reduced and the seat ring 2 can be securely sealed and welded by cast-in even in the shape of a thin valve body. When the seat rings 20, 30 having the shapes shown in FIGS. 3 and 4 are cast-in, the hatched portions 20a, 30a in FIG. In addition, the molten metal at the interface has already solidified and cannot be joined.

Therefore, the amount of heat required to heat the joint of the seat ring to the solidus temperature of ductile cast iron of 1150 ° C. or higher in the case of FIG. 3 was examined (the seat ring in FIGS. 3 to 5 has a valve nominal diameter size). Is 100A). First, the required heat amount Q1 of Comparative Example 1 in the seat ring 20 shown in FIG. 3 was calculated. Since Q1 = specific heat of stainless steel × work equivalent of heat × density of stainless steel × volume of hatched portion × solid phase temperature / heat efficiency, Q1 = 0.11 [ca
1 / g · ° C.] × 4.19 [J / cal] × 7.8 [g /
cm ³ ] × 26 [cm ³ ] (shaded portion 2 of seat ring 20)
0a volume) × 1150 ° C./0.9=119×10
³ [J]. When cast-in casting was performed under these conditions, a gap was formed between the hatched portion 20a of the seat ring 20 and the molten metal, and it was confirmed that seal fusion was not performed.

Next, when the required heat quantity Q2 of Comparative Example 2 in the seat ring 30 shown in FIG. 4 was calculated, Q2 =
0.11 [cal / g · ° C.] × 4.19 [J / cal]
× 7.8 [g / cm ³ ] × 8.7 [cm ³ ] (volume of hatched portion 30a of seat ring 30) × 1150 ° C / 0.9 =
It was 40 × 10 ³ [J]. As a result of cast-in-casting under these conditions, a gap was found between the hatched portion 30a of the seat ring 30 and the molten metal as a whole, and it was confirmed that seal fusion bonding was not performed. That is, the above two comparative examples show that the required amount of heat is not supplied to the seat ring 30 during casting.

FIG. 5 shows the case of the seat ring 2 according to the present invention, and the heat quantity Q3 is Q3 = 0.
11 [cal / g · ° C.] × 4.19 [J / cal] ×
7.8 [g / cm ³ ] × 2.9 [cm ³ ] (volume of hatched portion 7 of seat ring 2) × 1150 ° C./0.9=13.
It was 3 × 10 ³ [J]. As a result of cast-in-casting under these conditions, it was confirmed that the hatched portion 7 of the seat ring 2 and the molten metal were seal-welded. The above is an example in which the nominal size of the valve is set to 100 mm (100 A). When the required heat quantity in the case of the minimum valve size of 25 A is calculated, it is 4.2 × 10 ³ [J]. Is the maximum, the amount of heat required for the seat ring 2 for seal fusion joining is 4.0 × 10 ³ to
The range is 15.0 × 10 ³ [J]. Therefore, the seal fusion welding can be performed by setting the thickness of the hatched portion 7 so that the required amount of heat can be obtained from the ductile cast iron melt that is the cast-in main body 1 without using a special casting device. . More specifically, the shape of the hatched portion 7 is a fin shape having a triangular cross section, from the viewpoint of increasing the surface area to secure the above-mentioned heat amount, and also from the viewpoint of making the molten metal flow easily and performing casting without defects. Optimal. In addition, when the above calorie cannot be secured from the molten ductile cast iron,
By preheating at least the hatched portion 7 of the seat ring 2 in advance, seal fusion bonding can be performed. A plurality of fins 7 may be formed on the outer periphery of the seat ring 2 at positions shifted in the axial direction. However, the fins 7 are formed with a sufficient space between the fins so that the molten metal can easily enter. I do.

As described above, the fin portion 7 is locally heated by the heat of the molten metal, the solid-liquid coexistence time is sufficiently maintained until the molten metal solidifies, and the diffusion of the element of the surface of the seat ring 2 and the ductile cast iron is prevented. Both are sealed and fusion-bonded by forming a diffusion bonding layer. Therefore, the amount of heat supplied to the seat ring 2 from the molten metal at the time of pouring is
It is indispensable that the calorific value should be equal to or greater than the following formula. Heat amount = c × ρ × v × t / η c: Specific heat of the object to be cast ρ: Density of the object to be cast v: Volume of the object to be cast t: Solid phase temperature of the molten metal in the body of the object to be cast η: Thermal efficiency

The solid phase temperature mentioned above refers to the temperature at which the molten metal melts, and in this example, the temperature at which the molten metal and the cast body cause element diffusion in each other's metal and seal fusion bonding is performed. Say. Conversely, if the temperature falls below this temperature, solidification of the molten metal starts, and the cast body also starts to solidify.

FIGS. 6 and 7 show the effect of temperature change due to the amount of heat supplied to the seat ring.
The former is an example in which the seat ring is not preheated, and the latter is an example in which the preheating of 400 ° C. is performed. In this case, the nominal diameter of the valve is 100A, and the temperature of the molten metal at the time of pouring into the casting mold is about 1450 ° C. At this time, the fin portion 7 of the seat ring 2
A heat quantity of × 10 ³ [J] is supplied, and the fin portion is seal-welded. On the other hand, only a maximum amount of heat of about 13 × 10 ³ [J] is supplied to the sheet portion other than the fin portion, and a heat amount of 13.3 × 10 3 necessary for seal joining is provided.
³ Not enough [J]. Therefore, the seat ring 2 and the body 1 portion are not sealed and joined. In FIG. 6, the unbonded portion is lower than the solid phase temperature (1150 ° C.)
This shows that the molten metal hardens before the seat ring 2 is welded. As described above, the time for continuously supplying the heat quantity is not so problematic, and it is confirmed that it is necessary to supply the heat quantity necessary for seal fusion bonding at the time of pouring.

FIG. 7 shows the effect of a temperature change due to the ring temperature, and shows an example in which a seat ring is preheat-treated at 400.degree. In FIG.
A calorie of 4.6 × 10 ³ [J] was added and then poured. The seat ring 2 exceeded a heat of 13.3 × 10 ³ [J] required for seal fusion bonding. Total 1
A heat amount of 4.2 × 10 ³ [J] is applied, and the fin portion 7 is seal-welded.

As described above, by heating the seat ring 2, the seat ring temperature is higher than the solid phase temperature of 1150 ° C., whereby the seat ring 2 becomes hot before the molten metal solidifies, and the seal fusion bonding is performed. Was confirmed to have been promoted.

Further, the present invention can be applied to a seat ring of a gate valve, a globe valve, a check valve and other valves or a seat ring of a disc in addition to the above examples. It is also possible to cast-wrap a sheet ring made of ductile cast iron with a SUS material, and in this case, it is cost effective. Furthermore, not only can it be applied to the bonnet ring of the valve,
In addition to valve parts, it can be widely applied to machine parts, automobile parts, and the like.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a seal joining method by cast-in according to the present invention will be described with reference to drawings together with an experimental example. (Experimental Example 1) The seat ring 2 shown in FIG. 5 was placed at the valve seat position of the body 1 of the gate valve as shown in FIG. The size of the valve in the sample is 100A. The material of the seat ring 2 in the test sample is a steel material (SS400) plated with tin, and the seat surface is plated with stellite. The material of the body 1 is ductile cast iron (FCD-S). is there. After casting the seat ring 2 at a ductile cast iron melt temperature of 1400 ° C. to 1450 ° C., the sample was cut and polished after sufficiently air-cooled, and the metal structure of the seat ring joint surface was observed. FIG. 8 shows a metallographic photograph of a radial cross section of the seat ring 2.
FIG. 9 shows a photograph of the metal structure of the seat ring 2 in the circumferential direction.

According to the results of the experiment, in the metallographic photograph (25 magnifications) shown in FIG. 8, it was confirmed that the fin portion 7 of the seat ring 2 and the body 1 were seal-welded by casting. In this case, the range of fusion bonding is
It is about 2 mm. In FIGS. 8 and 9, it can be determined from the black portions in the photograph that the pearlite phase is rich in both the seat ring 2 (SS400) and the body 1 (FCD-S) in the fusion-bonded portion. . This indicates that diffusion of component elements by the seat ring material (SS400) and the body material (FCD-S) is performed at the bonding interface by seal fusion bonding. On the other hand, in the portion where the seal fusion bonding was not performed, both were ferrite phases. The fin portion 7 of the seat ring 2
9, the entire surface is melt-sealed along the circumferential direction in the state shown in FIG. 9, and the gap between the seat ring 2 and the body 1 that are not melt-sealed is the seat side 2 a of the seat ring 2. It gets wider as you go.

Further, in order to confirm that the seal fusion bonding was performed reliably, the surface structure analysis of the seat ring bonding surface was performed by an energy dispersive X-ray analyzer (EDX). The results are shown in Table 1 and FIGS.
At the fusion joint, diffusion of carbon (C) from the body 1 to the seat ring 2 is confirmed, and tin (Sn), which is a plating component of the seat ring 2, also diffuses to the body 1 and spreads throughout the fusion joint. It was confirmed that they were uniformly diffused.
Therefore, it was also confirmed from the result of the surface structure analysis by EDX that the seal fusion bonding was reliably performed.

(Experimental Example 2) An experiment was conducted by changing the material of the seat ring 2 in the test sample to stainless steel (SUS403). The size of the valve in the specimen is 25
A. The seat ring 8 shown in FIG.
a fin portion 9 on the opposite side 8b of the sheet,
And a thin-walled groove 8c is provided at the center. Cast-in was performed under the same pouring conditions as in Experimental Example 1, and the metal structure of the joint surface of the seat ring 8 was observed. FIG. 13 shows a photograph of a metal structure of a radial section of the fin portion 9 of the seat ring 8, and FIG. 14 shows a photograph of a metal structure of a radial section of the groove portion 8 c of the seat ring 8.

Also in this experimental result, as is apparent from the metallographic photograph (100 times) of FIG. 13, the sheet ring 8 is carburized, and the metallic structure on the body 1 side is a needle-like crystal. From the results, it was confirmed that the fin portion 9 of the seat ring 8 and the body 1 were seal-welded.
In addition, as apparent from the metallographic photograph (100 times) of FIG. 14, it was confirmed that the groove 8c and the body 1 were also seal-fused.

[0028]

[Table 1] Further, in order to confirm that the seal fusion bonding was performed reliably, the surface structure analysis of the seat ring bonding surface by EDX was performed as in Experimental Example 1. Table 1 and FIG.
5 and FIG. At the fusion joint, diffusion of carbon (C) from the body 1 to the seat ring 8 was confirmed, and chromium (Cr)
Was confirmed. Of these, C diffused into the carburized portion seen in the optically observed metallographic photograph,
In the seat ring 8, the concentration of C is highest at the joint interface, and the concentration gradually decreases toward the inside of the seat ring 8. On the other hand, Cr is present in the acicular crystal grains seen in the metallographic photograph, and the concentration gradually decreases toward the inside of the body 1. Therefore, it was also confirmed from the result of the surface structure analysis by EDX that the seal fusion bonding was reliably performed.

A pressure resistance test was performed using a gate valve in which the SS400 seat ring of Experimental Example 1 was cast. Table 2 shows the results.

[Table 2] First, as a pressure resistance test, the water pressure 47 was measured with the valve fully opened.
When [kgf / cm ² ] was added for 10 minutes, no fluid leakage outside the valve was confirmed. As an internal pressure test, a water pressure of 33 [kgf / cm ² ] was set to 1 when the valve was fully closed.
When 0 minute was added, no fluid leakage between the seat ring 2 and the body 1 was confirmed. Therefore, it was confirmed that the seal joining method by cast-in of the present invention, in particular, the fusion of the fin portion 7 has a sealing property that can withstand actual use.

[0030]

As is apparent from the above description, according to the present invention, the cast body and the cast body can be fusion-seal-bonded to each other. For example, it is most suitable for cast-in which enables seal joining such as valve parts.

Further, the number of steps can be remarkably reduced as compared with the conventional method in which valve parts and the like are joined by means such as screwing or caulking, thereby contributing to cost reduction.

[Brief description of the drawings]

FIG. 1 is a sectional view of a cast-in mold according to the present invention.

FIG. 2 is a cross-sectional view of the body of the gate valve cast and cast according to FIG. 1;

FIG. 3 is a partial explanatory view showing a conventional example of a seat ring.

FIG. 4 is a partial explanatory view showing another conventional example of a seat ring.

FIG. 5 is a partial explanatory view showing an example of a seat ring in the present invention.

FIG. 6 is an example of a graph showing an influence of a temperature change due to a seat ring temperature in the present invention.

FIG. 7 is another example of a graph showing an influence of a temperature change due to a seat ring temperature in the present invention.

FIG. 8 is a metallographic photograph (× 25) showing a joint portion between the fin portion and the body from a radial cross section of the seat ring in Example 1.

FIG. 9 is a metallographic photograph (× 100) showing a joint portion between a fin portion and a body from a circumferential section of a seat ring in Experimental Example 1.

FIG. 10 shows the results of EDX analysis (linear analysis) of the carbon content of the joint between the fin portion of the seat ring and the body in Experimental Example 1.

FIG. 11 is a result of an EDX analysis (linear analysis) of a tin amount in a joint portion between a fin portion and a body of a seat ring in Experimental Example 1.

FIG. 12 is a partial explanatory view showing an example of a seat ring in a second embodiment.

FIG. 13 is a metallographic photograph (× 100) showing a joint portion between the fin portion and the body from a radial cross section of the seat ring in Experimental Example 2.

FIG. 14 is a metallographic photograph (× 100) showing the center of the groove of the seat ring shown in FIG. 12;

FIG. 15 shows the results of EDX analysis (linear analysis) of the carbon content at the joint between the fin portion of the seat ring and the body in Experimental Example 2.

FIG. 16 shows the result of EDX analysis (linear analysis) of the amount of chromium at the joint between the fin portion of the seat ring and the body in Experimental Example 2.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 Cast-in body (body) 2 Cast-in body (seat ring) 3 Sand mold 4 Sand core 6 Casting space 7 Fin part 8 Seat ring

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasushi Shimizu 2040 Nagasaka Kamijo, Nagasaka Town, Kita-Koma County, Yamanashi Prefecture Inside the Kitz Nagasaka Plant (72) Inventor Yasuhide Maruyama 2040 Nagasaka Kamijo, Nagasaka Town, Kita Koma County, Yamanashi Prefecture Kitz Corporation Inside the Nagasaka Plant (72) Inventor Takashi Yamashino 1802 Higashi Takashino, Manano-machi, Nakatado-gun, Kagawa Prefecture Sanuki Casting Ironworks Co., Ltd.

Claims (5)

[Claims] 1. A method for pouring a molten metal into a casting mold provided with a body to be cast and integrally joining the body with the body to be cast and a body to be cast, wherein the molten metal is cast from the molten metal at the time of pouring. The heat quantity supplied to the wrapping body is set to be equal to or more than the heat quantity according to the following calculation formula, and at least a part of the cast body and the cast wrapping body are integrally joined in a state where they are fusion-sealed. Seal joining method by casting. Heat amount = c × ρ × v × t / η c: Specific heat of the object to be cast ρ: Density of the object to be cast v: Volume of the object to be cast t: Solid phase temperature of the molten metal in the body of the object to be cast η: Thermal efficiency 2. The cast-in body is made of ductile cast iron, and the cast-in body is made of a steel material such as stainless steel, and when pouring the cast-in body, from the molten ductile cast iron to the cast-in body,
2. The seal joining method according to claim 1, wherein the two parts are integrally joined by supplying a heat amount of 5.0 × 10 ³ [J] or less to form a seal fusion joint. 3. The seal joining method according to claim 1, wherein the seal joining portion of the cast-in body is a fin formed on an outer diameter of the ring-shaped cast-in body. 4. The seal joining method according to claim 1, wherein the object to be cast is preheated to supplement the supply of heat to the object to be cast. 5. The casting body according to claim 1, wherein the body is a valve body, the body to be cast is a seat ring, and the seat ring and the valve body are melt-bonded by the bonding method. A seal joining method using cast-in as described in Crab.