JPH11170004A - Sand mold for casting of deformed products - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the development of shrinkage in a boss hole by demarcating a hollow part in a pocket part of a sand mold corresponding to the boss hole and forming the sand thickness of the pocket part as a thin-walled part. SOLUTION: When the solidification starts after filling a cavity in the mold with molten metal, molten metal pressure pushing a part formed as the thin- walled part 5A of the pocket part 5 is developed in the molten metal by precipitating graphite in the molten metal, and since the thin-walled part 5A is formed as the hollow part 19 at the back surface, this thin-walled part is easily pushed in the direction of the arrow and deformed. In this result, the stretching pressure 4A of the molten metal is developed in the casting side. When the solidification progresses and the casting temp. becomes <= 100 deg.C, the vol. shrinkage caused by cooling of the casting itself is developed and the last solidified part is shrunk in the direction of the arrow and the stretching pressure 4A originally developed is returned back to the original target dimension 4B in the end. Therefore, the portion, at which the shrinkage at the time of solidifying is large and the developing amount of the shrinkage cavity is large, is secured in the shrinkage allowance by forming the thin-walled 5A part large and the original stretching pressure large to secure the precision of the target dimension 4B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sand for casting a modified product having a cylindrical boss hole at the center and a thick portion around the boss hole, such as a knuckle steering or a rear spindle. Regarding the mold.

[0002]

2. Description of the Related Art Conventionally, when a ductile casting is cast by a sand mold, it is common to provide a hot water at a necessary portion of the sand mold in order to prevent shrinkage of a thick portion. For example, the knuckle steering product W as shown in FIG. 1 has a cylindrical boss hole 4 at the center and a strut arm seat 1 which is a thick portion around the boss hole, so that the final solidified portion is the boss hole 4. Become a department. For this reason, a large feeder 2 is provided via a weir 3 at a portion of the strut arm seat 1 where shrinkage is likely to occur, and casting is performed.

[0003]

However, in the above solution, as shown in FIG. 2, the molten metal replenishment around the island portion 5 is not sufficient, and as a result, a slight external shrinkage occurs at the boss hole 4 which is the final solidified portion. Occur. (The dotted line 6 in FIG. 2 has the original shape, but is actually cast as a solid line 7.) The amount of shrinkage differs depending on the part, and the larger the thickness outside the boss hole 4, the larger the amount. For this reason, the occurrence of slight shrinkage cannot be prevented, so that the machining allowance for the portion of the boss hole 4 is large, and the reality is that machining is performed by machining. The present invention has been made in view of the above-described problem, and has a cylindrical boss hole in the center and has a thick portion around the boss hole. An object of the present invention is to provide a sand mold for casting a deformed product that does not generate.

[0004]

In order to achieve the above object, a sand mold for casting a deformed product according to the present invention has a cylindrical boss hole at the center and a thick boss hole around the cylindrical boss hole. A sand mold for casting a deformed product having a meat portion, wherein an island portion (projection) of the sand mold corresponding to the boss hole.
A hollow portion is formed, and the sand thickness of the island portion of the sand mold corresponding to the boss hole is reduced to a thin portion.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to FIGS. FIG. 1 shows upper and lower sand molds 11 and 12 for casting the same knuckle steering product W as described above.
A hollow portion 13 is defined in an island portion (projection portion) 5 of the sand mold corresponding to the boss hole 4, and the sand thickness of the island portion 5 is reduced to a thin portion. 5A.

When casting is performed using the sand molds 11 and 12 configured as described above, when solidification starts after the mold cavity is filled with the molten metal, graphite precipitates in the molten metal as shown in the left half of FIG. In the molten metal, there is generated molten metal pressure that presses the thinned portion 5A of the island portion 5 of the sand molds 11 and 12.
Here, the thin portion 5A is easily pushed in the direction of the arrow and deformed because the back surface is the hollow portion 13.
As a result, tension 4A is generated on the casting side. Thereafter, when the solidification proceeds and the temperature of the casting is cooled from a high temperature state to a temperature of 100 ° C. or less, the casting itself undergoes volume shrinkage due to cooling, and as shown in the right half of FIG. The solidification 4A generated during the graphite precipitation eventually returns to the original target dimension 4B (dashed line). The amount of deformation of the casting can be controlled by the thickness of the thin portion 5A of the island portion 5. Therefore, the portion having a large shrinkage at the time of solidification and having a large amount of shrinkage is made thinner by thinning the thin portion 5A to increase the initial tension, and the shrinkage margin is secured. The target dimension 4B accuracy is ensured by thickening the 5A portion and generating almost no initial tension.

[0007]

As is apparent from the above description, according to the present invention, a hollow portion is formed in an island portion of a sand mold corresponding to a boss hole in which shrinkage is likely to occur, and the sand thickness of the island portion is reduced. The boss is intentionally generated in the early stage of pouring, and this tension is restored during solidification and shrinkage. It has an excellent effect that it does not work.

[Brief description of the drawings]

FIG. 1 is a plan view showing a product to be cast.

FIG. 2 is a longitudinal sectional view showing a main part of a conventional sand mold for casting the product of FIG.

FIG. 3 is a longitudinal sectional view showing a main part of the sand mold of the present invention.

FIG. 4 is an enlarged explanatory view showing a state of an initial stage of pouring and a final stage of solidification in a portion A of FIG. 3;

[Explanation of symbols]

 2 Hot water 4 Boss hole 4A Tension 5 Island part 5A Thin part 13 Hollow part

Claims (1)

[Claims] 1. A sand mold for forming a cylindrical boss hole 4 in a central portion and casting a deformed product having a thick portion around the cylindrical boss hole 4. A hollow part 13 is defined in the corresponding island part (projection part) 5 of the sand mold,
A sand mold for casting a deformed product, characterized in that the sand thickness of the island portion 5 of the sand mold corresponding to the boss hole 4 is made thinner 5A.