JP3324024B2 - Manufacturing method of malleable cast iron products - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing a malleable cast iron product.

[0002]

2. Description of the Related Art As a threaded joint used for connecting pipes for water supply or hot water supply, there is an elbow 100 of J1S standard as shown in FIG. The elbow 100 has a resin body 300 formed by injection molding inside a joint body 200 made of malleable cast iron.
The resin core 300 is formed by injection molding in the inside.

Incidentally, in the case of a threaded joint such as this elbow 100 having a resin core 300 provided inside, a joint body 2
Since the coefficient of thermal expansion of the resin core 300 differs from that of the resin core 300, there is a possibility that the joint body 200 and the resin core 300 may be separated when hot water having a temperature difference is repeatedly flowed. Therefore, an attempt has been made to form a protruding portion on the inner wall surface of the joint main body 200 and to provide an anchor effect by this protruding portion to solve the problem of peeling. There are the following problems when integrally provided by casting.

[0004] That is, as a general casting technique, in order to compensate for heat shrinkage when the cast iron is solidified and to prevent the occurrence of a cavity (most commonly referred to as a "sink cavity"), it is called a feeder and has a high pouring hole. An extra pool is provided at the position to provide a structure in which pouring pressure is applied toward the end. However, if there is a thicker part at the center of the casting than at the pouring port side, since the pouring port (weir) side of the casting is thinner after pouring, cooling and solidification is faster than at the center, This leads to a situation where the effect of the hot water cannot be obtained.

[0005] As a result, when the thick part at the center of the casting is cooled and solidified, it is affected by heat shrinkage, which causes a phenomenon that cavities are generated and the casting is deformed.

[0006]

SUMMARY OF THE INVENTION In view of such circumstances, the present invention causes the occurrence of nests even in a cast product having a thick inner wall surface and a protruding portion provided on the inner wall surface. It is an object of the present invention to provide a method of manufacturing a malleable cast iron product which can be manufactured without a high yield.

[0007]

SUMMARY OF THE INVENTION A method for producing a malleable cast iron product according to the present invention is intended to achieve such an object.
In the method for manufacturing a malleable cast iron product having a protruding portion having a thicker wall and protruding on the inner wall surface of the intermediate portion, at least a portion of the protruding portion from an end on a pouring port side to a forming portion of the protruding portion is provided. After forming a cast product having a thickened portion having a width substantially equal to the thickness of the projected portion, the thickened portion of the cast product was cut and removed so as to leave the projected portion.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below.
This will be described in detail with reference to the drawings. First, as shown in FIG. 1, an elbow with a resin core is a pouring port (weir) of a casting mold 1.
2, molten malleable iron is poured into the casting mold 1 and increased from the end 31 on the side of the pouring port 2 toward the forming portion of the protrusion 32 provided at the inner corner of the L-shape as shown in FIG. 2. A casting 3a having a meat portion 33 and having a thickened portion 34 also formed on a portion facing the thickened portion 33 is cast.

Then, the thickened portion 33,
34, and after manufacturing the joint body 5 which is a malleable cast iron product as shown in FIG. 3, the resin core 6 is molded into the joint body 5 by injection molding, so that the elbow 7 with the resin core is formed. You can get it.

That is, according to this manufacturing method, the thickened portions 33, 34 are provided at the portions to be finally machined, and the solidified portions 33, 34 delay cooling and solidification from the center of the casting 3a. During cooling and solidification, the influence of the heat shrinkage of the casting 3a sequentially shifts to the upstream side of the molten metal, and finally, a molten metal part (not shown) is filled as a margin. Therefore, there is no generation of cavities or distortion during casting, and a malleable cast iron product can be manufactured accurately and with good yield.

[0011]

【Example】

(Example 1) 3000 castings 3a shown in Fig. 2 were cast and the number of burrs generated was examined. (Embodiment 2) As shown in FIG. 4, a cast product 3b provided with a thickened portion 33 only on the side where a protruding portion is provided is similarly 3000
Individual casting was performed, and the number of nests generated was examined.

(Embodiment 3) As shown in FIG. 5, a cast product 3c provided with a thickened portion 36 over the entire surface from the end 31 on the pouring gate side to the portion where the protruding portion 32 is formed is formed in the same manner as in FIG.
00 pieces were cast and the number of nests generated was examined. (Comparative Example 1) 3000 pieces of a cast product having a joint body in which the protruding portion 32 was formed were directly cast into 3000 pieces, and the number of burrs generated was examined.

Table 1 shows the number and rate of occurrence of nests examined in Examples 1 to 3 and Comparative Example 1.

[0014]

[Table 1]

From Table 1, it is clear that the production method of the present invention can produce elbows with little nesting and very good yield. Further, when the joint body 5 was manufactured by cutting and threading the cast products 3a, 3b, and 3c obtained in Examples 1 to 3, the cast product 3a of Example 1 was most after cutting and thread cutting. Workability was good.

The method for producing a malleable cast iron product according to the present invention can produce not only an elbow-shaped product as described above, but also a straight pipe joint, a tee-shaped joint, and other cast products.

[0017]

As described above, the method for producing a malleable cast iron product according to the present invention is a cast product having a protruding portion provided with a thick wall inside. Even without the occurrence of nests or distortion, it can be manufactured accurately and with good yield.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing one embodiment of a mold used in a method for manufacturing a malleable cast iron product according to the present invention.

FIG. 2 shows an example of a cast product manufactured by the method for manufacturing a malleable cast iron product according to the present invention, wherein FIG. 2 (a) is a longitudinal sectional view thereof, and FIG. FIG. 3 is a sectional view taken along line AA.

FIG. 3 is a sectional view of an elbow obtained from the casting of FIG. 3;

FIG. 4 shows another example of a cast product manufactured by the method for manufacturing a malleable cast iron product according to the present invention, and FIG.
Is a longitudinal sectional view, and FIG. 4B is a sectional view taken along line BB of FIG.

FIG. 5 shows another example of a cast product manufactured by the method for manufacturing a malleable cast iron product according to the present invention, and FIG.
Is a longitudinal sectional view, and FIG. 4B is a sectional view taken along line CC of FIG.

FIG. 6 is a sectional view of a conventional JIS-standard elbow with a resin core.

[Explanation of symbols]

 3a Casting Product 3b Casting Product 3c Casting Product 31 End 32 Projection 33 Thickening 34 Thickening 36 Thickening 5 Joint body (Machinable cast iron product)

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Tamotsu Takada 8-22 Kikusuicho, Kawachinagano-shi, Osaka Pref. Higashio Mec Co., Ltd. (56) References JP-A-5-123857 (JP, A) JP-A Heisei 6-71419 (JP, A) JP-A-8-42783 (JP, A) JP-A-7-2933781 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B22D 29/00 B22D 25/02 B22D 31/00 F16L 43/00

Claims (1)

(57) [Claims] 1. A method for manufacturing a malleable cast iron product having a projection on an inner wall surface of an intermediate portion, the projection having a thicker wall.
In the part from the pouring port side end to the formation part of the protrusion,
After forming a cast product having a thickened portion having a thickness substantially equal to the thickness of the protruded portion at least in the width of the protruded portion, cutting and removing the thickened portion of the cast product so as to leave the protruded portion. A method for producing a malleable cast iron product characterized by the following.