CN116944420A - Casting method of large thick-wall casting - Google Patents

Abstract

The application relates to a casting method of a large thick-wall casting, which comprises the following steps: the parting design is adopted, the parting is carried out on a large plane at the bottom of the casting, the whole casting is arranged on the cope flask, and the pouring system is arranged on the drag flask; the cope flask is designed along with the shape of the sand box; molding, namely sleeving the cope flask on a pattern, and molding by using sand, wherein a sand layer is formed between the cope flask and the pattern; forming and closing the mould, wherein the sand layer forms a cavity for accommodating the casting; pouring, namely pouring molten metal into the cavity, and sequentially solidifying the molten metal in the cavity from the first end to the second end. According to the scheme, the molten metal in the control cavity is solidified in the sequence from the first end to the second end, liquid-phase island cannot be generated in the casting in the solidification process, shrinkage porosity defect is effectively prevented, the cooling assembly is used as a sand box, only a thin sand layer is needed to be added in the molding process, and the sand-iron ratio is effectively reduced.

Description

Casting method of large thick-wall casting

Technical Field

The application relates to the technical field of casting, in particular to a casting method of a large thick-wall casting.

Background

The material of the turret casting used for the machine tool part is mainly gray cast iron, the casting is polygonal, the top is provided with two layers of steps, the bottom is provided with independent steps uniformly distributed, and the turret casting belongs to a large thick-wall casting. During finish machining, through holes with different sizes such as threading holes, oil filling holes and the like are required to be machined on the casting. Therefore, the turret type castings cannot have shrinkage porosity defects, otherwise leakage occurs during the machining and pressing stage, and the castings are scrapped.

For turret castings, the traditional casting mode is that the parting surface is arranged at a two-layer step position on the top surface of the casting, the casting is integrally designed in a lower box for facilitating mold lifting, and a pouring system adopts a side pouring mode to flow in and is matched with a riser for feeding. However, due to the fact that the thickness of the casting wall is too large, shrinkage porosity defects can be generated even if direct cooling irons are uniformly distributed along the periphery by adopting the casting mode, and the surface structure of the casting and the graphite morphology can be changed by using a large amount of direct cooling irons for chilling, so that chromatic aberration, local hardness is too high and the like are caused, and the appearance and the use requirements of the casting are not met.

Disclosure of Invention

In view of the above, it is desirable to provide a casting method for large thick castings that controls the solidification sequence.

In order to solve the problems, the application adopts the following technical scheme:

the embodiment of the application discloses a casting method of a large thick-wall casting, which comprises the following steps of:

the parting design is adopted, the parting is carried out on a large plane at the bottom of the casting, the whole casting is arranged on the cope flask, and the pouring system is arranged on the drag flask; the cope flask is designed along with the shape of the sand box;

molding, namely sleeving the cope flask on a pattern, and molding by using sand, wherein a sand layer is formed between the cope flask and the pattern;

forming and closing the mould, wherein the sand layer forms a cavity for accommodating the casting;

pouring, namely pouring molten metal into the cavity, and sequentially solidifying the molten metal from the first end to the second end.

In one embodiment, the cope flask comprises a flask body and a cooling assembly disposed within the flask body, the cooling assembly comprising an outer shell and an inner shell, the outer shell being circumferentially disposed on the outside of the pattern and the inner shell being circumferentially disposed on the inside of the pattern; and in the molding step, molding an outer sand layer by using the sand flow between the outer shell and the pattern, and molding an inner sand layer by using the sand flow between the inner shell and the pattern.

In one embodiment, the housing includes a first portion disposed outside the first end, a third portion disposed outside the second end, and a second portion connected between the first portion and the second portion; a direct cooling chiller is arranged between the first part and the first end; the second part comprises a thick end connected with the first part and a thin end connected with the third part, and the thickness of the second part gradually decreases from the thick end to the thin end; the thickness of the third portion is equal to the thickness of the thin end.

In one embodiment, the thickness of the sand layer between the third portion and the pattern is greater than the thickness of the sand layer between the second portion and the pattern.

In one embodiment, the thick end has a thickness of 3/4 of the casting wall thickness.

In one embodiment, two ends of the first portion are symmetrically provided with a second portion.

In one embodiment, a plurality of sand hanging pieces are arranged on the inner side of the outer shell and/or the outer side of the inner shell.

In one embodiment, the cooling assembly is fixedly connected to the flask body through a plurality of connecting ribs.

In one embodiment, a plurality of sets of cooling assemblies are disposed within the flask body for one-box, multi-piece casting.

The technical scheme adopted by the application can achieve the following beneficial effects:

according to the casting method of the large thick-wall casting, disclosed by the embodiment of the application, the molten metal in the cavity is controlled to be solidified in the sequence from the first end to the second end, no liquid-phase island is generated in the casting in the solidification process, and the shrinkage porosity defect is effectively prevented.

According to the casting method of the large thick-wall casting, disclosed by the embodiment of the application, on one hand, the cooling assembly can control the solidification sequence of the molten metal, so that the shrinkage porosity defect is effectively prevented from being generated, a large number of direct cooling chiller is not needed, and the quality and the appearance of the casting are improved; on the other hand, the cooling component is used as a follow-up sand box, and the molding process only needs to mold a thin sand layer by using the quicksand, so that the sand-iron ratio is effectively reduced.

Drawings

FIG. 1 is a schematic view of the structure of a turret casting;

FIG. 2 is a schematic view of the structure of the cope flask before molding;

FIG. 3 is a cross-sectional view A-A of FIG. 2;

FIG. 4 is a schematic view of the structure of the cope flask after molding;

reference numerals illustrate:

110-a sand box main body, 111-a box mouth plate, 112-a box lug, 113-a hanging shaft and 114-a connecting rib;

120-outer shell, 121-first portion, 122-second portion, 1221-thick end, 1222-thin end, 123-third portion, 130-inner shell; 140-a receiving cavity;

200-direct cooling chiller;

310-an outer sand layer, 311-a first end, 312-a second end; 320-an inner sand layer;

400-pattern.

Detailed Description

In order that the application may be readily understood, a more complete description of the application will be rendered by reference to the appended drawings. The drawings illustrate preferred embodiments of the application. This application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

In the description of the present application, it should be noted that the directions or positional relationships indicated by the terms "upper", "lower", "inner", "outer", "front end", "rear end", "both ends", "one end", "the other end", etc. are based on the directions or positional relationships shown in the drawings, are merely for convenience of describing the present application and simplifying the description, and do not indicate or imply that the apparatus or element to be referred to must have a specific direction, be configured and operated in the specific direction, and thus should not be construed as limiting the present application. Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the description of the present application, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "provided," "connected," and the like are to be construed broadly, and may be fixedly connected, detachably connected, or integrally connected, for example; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be the interior of two original elements together. The specific meaning of the above terms in the present application will be understood in specific cases by those of ordinary skill in the art.

The embodiment of the application discloses a casting method of a large thick-wall casting, taking a turret for a machine tool as shown in fig. 1 as an example, so as to facilitate understanding of the technical concept of the application. The turret is a gray cast iron casting, the outer side of the casting is integrally polygonal, two layers of ladder steps are arranged at the top of the casting, and a hole-shaped structure is arranged at the inner side of the casting. The application adopts a casting method of sequential solidification to effectively eliminate shrinkage porosity defect, and concretely, the casting method can comprise the following steps:

s1, parting design, namely parting a large plane at the bottom of a turret casting, wherein the turret casting is integrally arranged on a cope flask;

s2, designing a pouring system, wherein the pouring system is arranged on a drag flask by adopting a bottom pouring type pouring system;

s3, modeling, namely sleeving the cope flask on the model to enable sand to flow, compacting, modeling and lifting; arranging a pouring system in a drag flask for sand flowing and compacting molding;

s4, closing the box, namely placing the cope flask on the drag flask and fixing the cope flask;

s5, pouring, namely, pouring molten metal into a casting cavity through a pouring system, sequentially solidifying the molten metal in the cavity according to a preset temperature gradient, namely, the solidification sequence from a first end to a second end, and feeding by adopting a riser at the tail end of a liquid phase of the casting in cooperation with the sequential solidification.

In the embodiment disclosed by the application, the temperature gradient of the molten metal in the cavity can be controlled by adopting the structure of the special cope flask so as to realize sequential solidification of the molten metal, and the molten metal is matched with the feeding head arranged at the tail end of the liquid phase of the casting, so that liquid-phase island cannot be generated in the casting, and the shrinkage porosity defect of the casting is thoroughly eliminated.

Specifically, as shown in fig. 2 to 4, the special cope flask may include a flask main body 110, and as in the conventional flask, a flask mouth plate 111 is provided at an opening of the flask main body 110, and a plurality of lugs 112 are provided at intervals on the flask mouth plate 111 for positioning and limiting a mold close between the cope flask and the drag flask; the opposite outer sides of the flask body 110 are provided with hanging shafts 113 for hanging the cope flask. Unlike conventional flasks, a cooling assembly is fixedly provided in the flask body 110 for controlling the temperature gradient of the molten metal in the cavity. The cooling assembly is configured to follow the casting, and the overall structure of the cooling assembly is in the shape of a pagoda, and may include an outer shell 120 configured to follow the casting outer wall and top wall, and an inner shell 130 configured to follow the casting (hole-like structure) inner wall. The cooling assembly is fixedly arranged in the sand box main body 110 through a plurality of connecting ribs 114, and the connecting ribs 114 are used for connecting the sand box main body 110 and the cooling assembly on one hand and strengthening the cope flask on the other hand.

The housing 120 may have a polygonal, stepped structure corresponding to the polygonal, stepped structure of the turret; the inner case 130 may be cylindrical and fixedly provided at the center of the outer case 120 corresponding to the hole structure of the turret; the inner wall of the outer shell 120 and the outer wall of the inner shell 130 form a receiving cavity 140 for receiving the pattern 400 and the sand mold. In the molding step, the pattern 400 may be placed in the accommodating cavity 140, and the sand may be flowed into the accommodating cavity 140 and compacted, and the sand mold may be formed after the sand is solidified. Compared with the traditional casting method, the embodiment only fills sand in the accommodating cavity 140, but not the whole cope flask, so that the sand amount for casting is reduced, the casting cost is saved, the weight of the flask is reduced, and the sand-iron ratio of the cope flask is effectively reduced. Specifically, the outer sand layer 310 may be formed by filling sand between the pattern 400 and the outer shell 120, the inner sand layer 320 may be formed by filling sand between the pattern 400 and the inner shell 130, and the outer sand layer 310 and the inner sand layer 320 may together form a casting cavity after the pattern is drawn.

The sand layer thickness of sand mould is far less than traditional casting in this embodiment, and cooling module can be the iron material, and it accelerates the cooling rate of molten metal in the die cavity to through the combined action of inner shell 130 and shell 120, all accelerate the cooling from the inner wall and the outer wall of die cavity, improve the whole cooling rate of foundry goods, further promote foundry goods quality. In this embodiment, the thickness of the inner shell 130 is the same throughout, and the cooling gradient of the molten metal in the cavity can be controlled by the change of the wall thickness of the outer shell 120.

Specifically, the housing 120 may include a first portion 121, two second portions 122 respectively fixed to two ends of the first portion 121, a third portion 123 disposed opposite to the first portion 121, and two second portions 122 respectively fixed to two ends of the third portion 123. The direct chill 200 may be provided inside the first portion 121 such that a first end 311 having the greatest cooling rate is formed therein; the third portion 123 is the thinnest wall thickness of the three portions of the housing 120 and is spaced from the cavity by an outer sand layer 310, where a second end 312 with the minimum cooling rate is formed; the second portion 122 includes a thick end 1221 and a thin end 1222, and the thickness thereof decreases gradually from the thick end 1221 to the thin end 1222, the thick end 1221 is connected to the first portion 121, the thin end 1222 is connected to the third portion 123, and the outer sand layer 310 is also spaced between the second portion 122 and the cavity, so that a decreasing area is formed between the cooling rate corresponding to the thick end 1221 and the thin end 1222. In this embodiment, by means of the direct cooling iron 200 and the sand-insulation gradual-change shell 120, a temperature gradient is formed from the first end 311 to the second end 312, i.e. the solidification sequence is controlled from the first end 311 to the second end 312; and, the liquid phase tail end of the casting is fed by matching with the riser arranged near the second end 312, so that the shrinkage porosity defect of the casting is thoroughly eliminated, and the casting quality is improved.

Further, the inner shell 130 corresponding to the uniform wall thickness, and the inner sand layer 320 is also equal in thickness everywhere; the thickness of the outer sand layer 310 increases gradually from its corresponding thick end 1221 to its corresponding thin end 1222, and the thickness of the outer sand layer 310 at its corresponding third portion 123 is greater than its corresponding second portion 122, so that the cooling gradient from the first end 311 to the second end 312 is further increased by controlling the combination of the positive thickness gradient of the outer shell 120 and the negative thickness gradient of the outer sand layer 310.

Preferably, the thickness of thick end 1221 may be 3/4 of the maximum wall thickness of the casting, and the wall thickness of thin end 1222, first portion 121, third portion 123, and/or inner shell 130 may be 20mm; the thickness of the inner sand layer 320 was 20mm and the thickness of the outer sand layer 310 at the thinnest point was 20mm.

Of course, to further increase the cooling gradient from the first end 311 to the second end 312, the inner shell 130 may be configured with a positive wall thickness gradient and/or the inner sand layer 320 configured with a negative sand layer thickness gradient.

In the embodiment disclosed in the present application, the direct cooling chiller may not be used, as long as the wall thickness of the first portion 121 is increased to be greater than the wall thickness of the second portion 122 or/and the thickness of the outer sand layer 310 corresponding to the first portion 121 is reduced to be smaller than the thickness of the outer sand layer 310 corresponding to the second portion 122.

In the disclosed embodiment, the outer side of the inner shell 130 and/or the inner side of the outer shell 120 may be provided with a plurality of sand hanging members (not shown) to enhance the connection effect of the cooling assembly and the sand mold.

In the embodiment disclosed in the present application, a plurality of sets of cooling assemblies may be disposed in one cope flask for casting a plurality of products in one box, and the plurality of products may share one set of pouring system, or a plurality of sets of pouring systems may be used, which is not particularly limited in this embodiment. The rest of the structure of this embodiment may be the same as any of the above embodiments, and this embodiment will not be repeated.

The above examples illustrate only a few embodiments of the application, which are described in detail and are not to be construed as limiting the scope of the application. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the application, which are all within the scope of the application. Accordingly, the scope of protection of the present application is to be determined by the appended claims.

Claims (9)

1. The casting method of the large thick-wall casting is characterized by comprising the following steps of:

the parting design is adopted, the parting is carried out on a large plane at the bottom of the casting, the whole casting is arranged on the cope flask, and the pouring system is arranged on the drag flask; the cope flask is designed along with the shape of the sand box;

molding, namely sleeving the cope flask on a pattern, and molding by using sand, wherein a sand layer is formed between the cope flask and the pattern;

forming and closing the mould, wherein the sand layer forms a cavity for accommodating the casting;

pouring, namely pouring molten metal into the cavity, and sequentially solidifying the molten metal in the cavity from the first end to the second end.

2. The method of casting a large, thick-walled casting according to claim 1, wherein the cope flask comprises a flask body and a cooling assembly disposed within the flask body, the cooling assembly comprising an outer shell disposed circumferentially and concomitantly to the outside of the pattern and an inner shell disposed circumferentially and concomitantly to the inside of the pattern;

and in the molding step, molding an outer sand layer by using the sand flow between the outer shell and the pattern, and molding an inner sand layer by using the sand flow between the inner shell and the pattern.

3. The method of casting a large, thick-walled casting of claim 2 wherein the housing comprises a first portion disposed outside the first end, a third portion disposed outside the second end, and a second portion connected between the first portion and the third portion;

a direct cooling chiller is arranged between the first part and the first end; the second part comprises a thick end connected with the first part and a thin end connected with the third part, and the thickness of the second part gradually decreases from the thick end to the thin end; the thickness of the third portion is equal to the thickness of the thin end.

4. A method of casting a large, thick-walled casting according to claim 3 wherein the sand layer thickness between the third portion and the pattern is greater than the sand layer thickness between the second portion and the pattern.

5. A method of casting a large, thick-walled casting according to claim 3 wherein the thick end has a thickness of 3/4 of the casting wall thickness.

6. A method of casting a large, thick-walled casting according to claim 3 wherein the first portion has a second portion symmetrically disposed at each end.

7. The method for casting a large thick-wall casting according to claim 2, wherein the inner side of the outer shell and/or the outer side of the inner shell is provided with a plurality of sand hanging pieces.

8. The method of casting large, thick-walled castings according to claim 2, wherein the cooling assembly is fixedly secured within the flask body by a plurality of connecting bars.

9. A method of casting large thick-wall castings according to any of claims 2 to 8, wherein a plurality of sets of cooling assemblies are provided within said flask body for one-box multi-piece casting.