JP2589569B2 - Molding method for raw sand core - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method suitable for molding a core having a complicated shape using green sand.

(Prior art and its problems) Conventionally, as a method of molding a raw sand core, a raw material filled in a core box is inserted with a rod member having a substantially inverted pyramid shape, and the raw sand is formed. A method of compression hardening is used. However, when a core having a complicated shape is formed by such a method, there is a disadvantage that the fine sand is not sufficiently filled in the cavity details. The method of molding a child was limited to molding a core of a simple shape.

(Purpose) The present invention has been made in view of the above problems, and has as its object to provide a method capable of molding a core having a complicated shape with green sand.

(Means for Solving the Problems) The present invention introduces green sand into the additional frame cavities of each of the divided core boxes in which a filling frame is added to the mold mating surface, and fills the filling frame into which the green sand has been introduced. On the other hand, the compression member whose outer peripheral shape is similar to the inner surface shape of the filling frame and whose bottom surface is concave is formed, and the lowermost end surface of the compression member is at the same level as the mating surface of the divided core box. The green sand is subjected to primary pressure hardening, and the compressed member and the filling frame are extracted and separated to form a half-broken raw sand core having a convex mating surface into divided core boxes. The divided core boxes holding the sand cores are pressed together with the mold, and the convex portions of the half-split raw sand cores are compression-bonded, whereby a pair of half-split raw sand cores are integrated and at the same time secondary compression hardening. It is characterized by the following.

(Operation) In the present invention, by adopting the solution as described above, the green sand is sufficiently filled up to the details of the cavity of each divided core box, and then compressed toward the cavity surface. The primary compression hardening is performed to form a half-broken green sand core having a mating surface that is convex, and then, the divided core boxes are molded and pressed to integrate the green sand core that has been separately molded. At the same time, it is subjected to secondary compression hardening to form a green sand core.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

In FIG. 2, the divided core boxes (1A) and (1B), which can be divided into upper and lower parts, are combined to define a cavity that forms a complex cavity surface (1a) (1b) on the inner peripheral surface. It is configured to be.

A filling frame (2) having the same cross-sectional shape as the shape of the mating surface (1C) of the divided core box (1A) is placed on the upper part of the divided core box (1A) thus configured.

Next, a predetermined amount of green sand is poured into the additional cavity of the filling frame defined by the divided core box (1A) and the filling frame (2).
At this time, the green sand is charged from the side opposite to the cavity surface (1a), so that it is filled over the details of the cavity surface (1a).

Next, the compression member (3) whose outer shape is similar to the inner shape of the filling frame (2) and whose bottom shape is concave (3a) is divided by the lowermost end surface (3b) of the compression member (3) during the division. Child box (1
Insert it until it is at the same level as the mating surface (1C) of A) and apply pressure to the green sand toward the cavity surface (1a) to make the green sand primary compression hardened. (FIG. 1 (a)) Next, the compression member (3) is extracted from the filling frame (2), and the filling frame (2) is separated from the divided core box (1A). From this, the split core box (1A) has the outer peripheral edge at the same level as the mold mating surface (1C) of the split core box (1A) and the remaining inner part protrudes upward (MC). The half-broken raw sand core (Ma) having the part is held.

The above operation is similarly performed for the split core box (1B), so that the split core boxes (1A) and (1B) hold the half-broken raw sand core (Ma) (Mb).

Next, after the split core boxes (1A) (1B) holding the half-broken raw sand cores (Ma) (Mb) are matched as shown in Fig. 2 (a),
Press the split core boxes (1A) and (1B) and compress the half-broken raw sand cores (Ma) (Mb) until the mating surfaces (1C) abut each other as shown in Fig. 2 (b) . At this time, half-broken raw sand core (Ma)
In the case of (Mb), the convex (Mc) portion is once collapsed and compressed again, so that the two are integrated and simultaneously subjected to secondary compression hardening.

Next, the divided core boxes (1A) and (1B) are divided by conventional means, and the integrated green sand core (M) is taken out to complete the molding of the green sand core.

It was confirmed that the green sand core (M) molded in this way had a sufficient hardness, even when the surface shape was complicated, the mold shape was accurately transferred and the whole was integrated. Was done.

In the above embodiment, the bottom surface of the compression member (3) has a concave shape (3a) which is long in the lateral direction. However, as shown in FIG. Good.

(Confirmation Experiment) A confirmation experiment was performed on the state of adhesion of the green sand core formed by the present invention, and this will be described with reference to FIGS. 3 (a) and 3 (b).

A cylindrical body (11) (11A) having an inner diameter of 50mmφ and a height of 25mm is mounted on a surface plate (12) (12A), and a half-broken raw sand core (13) (13A) is formed in the same manner as in the above embodiment. Fig. 3 (a) shows a combination of the two. In Fig. 3 (a), a product was formed in which the dimension A was changed in two steps and the dimension B was changed in four steps. Fig. 3 (b) shows the half-broken green sand cores (13) and (13A) integrated by pressing the molded product. In the drawing, (14) is a lifting pin attached to the cylindrical body (11A), (15) is a lifting device, and the lifting device (15)
Is connected to a tensile load cell (not shown) at the upper part, and the lower end is locked to the pin (14).

With such a structure, the cylindrical body (11) is fixed and the pulling-up force is increased, so that the green sand core (M) bonded and integrated at a certain point is torn off at the bonded portion. The tensile force at this time was measured with a load cell, and at the same time, the convex (13 ° C) portion of the raw sand core collapsed and the mold mating surface (11C) (11
Table 1 shows the results of observation of the state protruding into C). The density of the raw sand core was adjusted to 1.5 g / cm ³ finally.

Here, the adhesive force is a value obtained by dividing a value obtained by measuring the tensile force by a load meter by a cross-sectional area of a cylinder having an inner diameter of 50 mm to obtain an adhesive force per unit area. The evaluation of the run-out of the green sand on the mating surface was as follows.

：: no protrusion △: slightly protruded, no problem in practical use ×: large amount of protrusion, impractical From the above results, the larger the A dimension of the convex (13 ° C) part of the raw sand core, the higher the adhesive strength, and the matching of the mold The protrusion to the surface also tends to increase.

As the B dimension decreases, that is, as the initial contact area of the half-broken raw sand core increases, the adhesive force increases, and the protrusion to the mating surface also increases.

If the adhesive strength of the raw sand core is 0.05 kg / cm ² or more, it can sufficiently handle the handling of the raw sand core.

It can be seen from the amount of the protruding green sand protruding from the mold-matching surface that the relationship of A and B of the protruding (11C) portion of the half-broken green sand core should satisfy A ≦ B.

(Effects) As is clear from the above description, the present invention provides a split core box in a state in which filling is easy, fills green sand, and first-compresses and hardens it to form a half-broken green sand core. Further, the core is molded by pressing the half-broken green sand core to perform secondary compression and hardening to form a core by integrating and secondary compressing the half-broken green sand. Raw sand is filled over the details of the cavity of the box and compressed, and even for cores with complex shapes, the mold shape is accurately transferred and molded, and a core with high strength is molded. Has an excellent effect.

[Brief description of the drawings]

FIGS. 1 and 2 show the process of the present invention. FIG. 1 (a) is a sectional view showing a molding state of a half-split raw sand core, and FIG. 1 (b) is another compression. FIG. 2 (a) is a cross-sectional view showing a molding state of a half-split raw sand core using a member, FIG. 2 (a) is a cross-sectional view showing a mold-matching state of a half-split raw sand core, and FIG. Sectional view showing the compressed state of the sand core, FIG. 3 (a) is a sectional view showing the matching state of the half-broken raw sand core by the confirmation experiment, and FIG. 3 (b) is the tensile force measurement state by the confirmation experiment FIG. (1A) (1B): Split core box, (1C): Molding surface (2): Filling frame, (3): Compressed member (3a): Concave, (Ma) (Mb): Half cracked green sand Child (M): Raw sand core, (Mc): Convex

Claims (1)

(57) [Claims] 1. A fresh sand is introduced into a filling frame addition cavity of each divided core box having a filling frame added to a molding surface, and an outer peripheral shape of the filling frame into which the green sand is introduced is the same as that of the filling frame. Primary compression of green sand by inserting a compression member similar to the inner surface shape and having a concave bottom shape until the lowermost surface of the compression member is at the same level as the mating surface of the split core box. After curing, the compression member and the filling frame are extracted and separated, and a half-split raw sand core having a mating surface formed in a convex shape is formed into a split core box, and a split core holding each half-split raw sand core. A box which is molded and pressed to compressively bond the convex portions of the half-broken green sand core to unite a pair of half-broken green sand cores and to simultaneously perform secondary compression hardening. Molding method.