CN1921969B - Process for producing cast item - Google Patents

Abstract

A process for producing a cast item with the use of a mold capable of easily crumbling. There is provided a process comprising the step of mixing together a granular aggregate, at least one type of water-soluble binder and water to thereby obtain an aggregate mixture and agitating the aggregate mixture to thereby effect foaming. This aggregate mixture is capable of suppressing undesirable gas generation at the time of mold formation or melt casting. Further, there is provided a process comprising the step of filling a space for mold formation with the foamed aggregate mixture and evaporating water from the charged aggregate mixture to thereby solidify the aggregate mixture, thus accomplishing mold formation; the step of assembling the mold with another mold into a final mold; the step of casting a melt in the final mold; the step of, during the period of cooling of cast item after melt solidification, removing the mold from the cast item; and the step of performing heat treatment of the cast item.

Description

Manufacturing methods of castings

technical field

The present invention relates to a casting manufacturing method, in particular to a casting manufacturing method which replaces the existing Joule Monte method and can easily remove the casting mold.

Background technique

The Joule Monte method is known as a conventional light alloy casting production method, for example, the production method described in Japanese Patent Office Publication No. 5-261478. The binder of the Joule Monte method is phenolic resin. The molding sand covered with the binder is blown into and filled in a mold for molding, and the binder covering the molding sand is hardened by the heat of the mold.

In this Joule-Monte method, however, the core mold after pouring is relatively hard, and to break the core mold and remove it from the casting requires a demoulding process in which a large impact force is applied to the core mold. In order to carry out this demolding process, the casting needs to be sufficiently cooled before heat treating the casting. In addition, even if a large impact force of 1Mpa or more is given at 10Hz or more and 10sec or more, there is only about 70%-80% of sand falling out. During and after heat treatment, the damaged core mold still has residues, such as core sand residue and core fragments. Therefore it must be removed again. Even to remove core fragments from castings and regenerate them, firing is often performed.

In addition, in the Joule Monte method, when the binder is hardened by the heat of the metal mold, volatile gas is generated along with it. This kind of volatile gas is accompanied by unpleasant smell, especially phenol, aldehyde, ammonia, etc. are harmful to human body.

Therefore, it is necessary to provide a casting manufacturing method that preferably replaces the existing Joule Monte method, and is easy to remove the casting mold and suppresses the generation of volatile gases.

Contents of the invention

The "granular aggregate" mentioned in this specification is composed of one or more of silica sand, zircon sand, olivine ore sand, chromite sand, aluminum sand, mullite sand and artificial sand.

"After the molten metal has solidified" in this specification means that the molten metal has solidified and hardened. This temperature varies with the process and the material of the molten metal.

The "casting cooling period" in this specification refers to a period during which the casting is cooled to a temperature lower than the temperature at which it is taken out from the finished mold without deformation. For example, when aluminum alloy is subjected to T6 treatment, the "casting cooling period" is about lower than 520°C but higher than the usual cooling temperature of 70°C or even 111°C, for example, during the cooling of the casting to 300°C.

According to a kind of casting method provided in one situation of the present invention, it comprises:

Containing at least one type of granular aggregate, at least one type of water-soluble binder, and the process of forming an aggregate mixture by adding water and mixing it, stirring the aggregate mixture and making it foam;

The process of filling the foamed aggregate mixture into the molding space of the mold, evaporating the water in the filled aggregate mixture to solidify the aggregate, and using the above aggregate mixture to shape the mold;

the process of mounting at least one pair of molds molded using the aggregate mixture to the mating molds to complete the mold;

The process of pouring molten metal into the above-mentioned completed mold;

The process of removing the above-mentioned mold from the above-mentioned casting during the cooling of the casting after the solidification of the above-mentioned molten metal;

The process of heat treating the above castings.

Core casting is preferred for molds molded using aggregate mixtures. In this case, the mating mold (master mold) can be a metal mold or a sand mold.

The "completed mold" in this specification is a mold in which molten metal can be poured, which is a combination of a main mold and at least one mold (core mold) molded from an aggregate mixture. And complete the constituent parts of casting mold except main casting mold and core casting mold, also can comprise the parts needed when other pouring.

In the production method of the present invention, a process of recovering the particulate aggregate and a process of regenerating the recovered particulate aggregate may be included. It is better to recycle the recovered and regenerated granular aggregates into the mold.

According to an embodiment of the present invention, the recovery and regeneration process of granular aggregate is mechanical regeneration.

The castings may be aluminum alloy castings, magnesium alloy castings, or copper alloy castings.

The heat treatment can be T6 or T7 treatment.

In one embodiment of the present invention, the casting mold removal process is a process of applying vibration to the casting mold. For example, the process of applying vibration to the above-mentioned casting mold is the process of applying an impact force of less than 1 MPa, less than 30 Hz, and less than 30 sec to the above-mentioned casting mold within 5 minutes to 20 minutes after pouring.

A casting manufacturing method in another aspect of the present invention, which includes:

Containing at least one type of granular aggregate, at least one type of water-soluble binder, and the process of forming an aggregate mixture by adding water and mixing it, stirring the aggregate mixture and making it foam;

Stir the aggregate mixture and make it foam, fill the foamed aggregate mixture into the molding space of the mold, evaporate the water in the filled aggregate mixture to solidify the aggregate, and use the above aggregate mixture to The process of molding the core mold;

the process of assembling at least one of the aforementioned core molds and metal molds into a complete mold;

The process of pouring molten aluminum alloy into the above-mentioned finished mold;

The process of removing the above-mentioned core mold from the above-mentioned casting during the cooling of the casting after the solidification of the above-mentioned molten metal;

The process of performing T6 or T7 heat treatment on the above-mentioned aluminum alloy castings.

The above-mentioned at least one type of water-soluble binder is at least one of polyvinyl alcohol or its derivatives, or at least one of starch or its derivatives.

Description of drawings

Fig. 1 is the flowchart of the manufacturing method of casting among the present invention.

FIG. 2 is a flow chart of a conventional casting method using the Joule Monte method.

Fig. 3 is a graph showing the relationship between temperature and time of the casting during removal of the mold and heat treatment in this example.

FIG. 4 is the same diagram as FIG. 3 showing the process in the prior art using the Joule Monte method corresponding to FIG. 3 .

Detailed ways

The preferred embodiments of the present invention are given below in conjunction with the accompanying drawings to describe the technical solution of the present invention in detail.

Flowchart Fig. 1 schematically shows each process in the casting method of the present invention.

Firstly, the principle of the casting manufacturing method of the present invention is introduced according to the flow chart.

In Fig. 1, at least one granular aggregate, at least one water-soluble binder and water phase are mixed in the first step to form an aggregate mixture, which is foamed by stirring (the first (conditioning) process 1).

In the second step, the aggregate mixture foamed in the previous process is used to fill and solidify the molding space of the mold, and the mold made of granular aggregate is molded (second (molding) process 2).

In the third step, at least one shaped casting mold (core casting mold) is assembled to the matching casting mold (main casting mold) to complete the casting mold (third (assembly) process 3).

In a fourth step, molten metal is poured into the finished mold (fourth (pouring) process 4).

In the fifth step, during the cooling of the casting after the molten metal has solidified, the core mold is detached from the casting and drawn from the casting (fifth (drawing) process 5).

In the sixth step, by subjecting the casting to heat treatment (sixth (heat treatment) process 6), a finished product of the casting is produced.

Each process in Fig. 1 is described in more detail.

As the granular aggregate in the first (preparation) process 1, at least one of silica sand, zircon sand, olivine ore sand, ferrochrome sand, aluminum sand, mullite sand, and artificial sand is used.

The water-soluble binder is preferably a material soluble in water at normal temperature. A water-soluble binder that is soluble in water at room temperature and can form aggregate mixtures without heating. Saves time and energy for heating the binder and granular aggregate. This is an advantage compared to the coated sand production in the existing Joule Monte method. Although the water-soluble binder used in the present invention is preferably any one of polyvinyl alcohol or its derivatives, starch or its derivatives, or both of them are used as water-soluble binders, it is not limited to this . Because this water-soluble binding agent is easy to volatilize and can be dissolved, in the process 5 thereafter (pull die) process 5, it is easy to remove the core mold from the solidified casting of molten metal. And it is better to add 0.1-0.5 parts by weight of water-soluble binder to the granular aggregate.

The aggregate mixture formed by mixing at least one water-soluble binder, at least one granular aggregate and water. The aggregate mixture is whipped creamy by stirring it to foam.

In the second (molding) process 2, the water in the aggregate mixture filled in the molding space is evaporated, the aggregate mixture is solidified, and the hollow core made of granular aggregate is formed by the foaming process of the previous process. A mold (core mold) is molded. The porosity of the hollow mold is 3%-60%. And, for example, when the thickness of the hollow mold is about 40mm, more than 50% of the water-soluble binder accumulates on the surface layer of the mold between the surface of the mold and a depth of 10mm from the surface of the mold. That is to say, in the hollow mold made of foamed aggregate mixture, the air bubbles dispersed in the aggregate mixture and the moisture contained in the binder gather at the center of the mold, and the bone in the center of the mold is destroyed by the evaporation of the moisture. The packing density of the material is reduced.

In the third (assembly) process 3, at least one core mold made of granular aggregate is assembled on the main mold (counter mold) to constitute the finished mold. The main casting mold may be a metal mold, or may be, for example, molding sand composed of granular aggregates. In this embodiment, a metal mold is used as the main casting mold, and low-pressure casting is adopted. However, when metal molds are used, the method of the present invention is not limited to low-pressure casting, and processing methods such as back pressure casting, die-casting, and gravity casting of metal molds can also be used.

In the fourth (pouring) process 4, the material of the molten metal poured into the mold is aluminum alloy in this embodiment, but it is not limited thereto, other light metal alloys or non-ferrous alloys (such as magnesium alloys or copper alloys) are also OK. It is also possible to use cast iron, cast steel or ferrous metal alloys. However, in the case of using iron-based metals, it is preferable to apply a layer of mold coating on the core mold.

The fifth (drawing) process 5 will be during the cooling period (the time to cool the casting so that the casting reaches a lower temperature than when the casting is cooled to such an extent that it will not deform even if the casting is taken out of the completed mold) The core mold is removed from the casting. Here, the "cooling period" in the fourth process 4 when the molten metal material is aluminum alloy refers to cooling the casting to a temperature lower than the solution treatment temperature of about 520°C for the aluminum alloy T6, but lower than the usual The cooling temperature is 70-111°C to a higher temperature, such as 300°C.

In the sixth (heat treatment) step 6, when the molten metal is an aluminum alloy, the heat treatment is heat treatment such as T6 treatment and T7 treatment.

As a water-soluble binder, by using polyvinyl alcohol or its derivatives, or starch or its derivatives, even in the first (preparation) process of kneading and adjusting the granular aggregate mixture containing the binder And in the second (molding) process 2 of molding the core casting mold, also can not produce, emit the gas of unpleasant smell.

And in the fourth (pouring) process 4 of pouring molten metal into the core mold, even if the molten metal heats the binder, no unpleasant-smelling gas and undesirable volatile gas.

In the casting manufacturing method of the present invention shown in FIG. 1 , after the sixth (heat treatment) process 6, the following processes may be added as needed. That is, the seventh (recycling) process 7 of recycling the granular aggregate (core sand) and core fragments of the core mold, the eighth (crushing) process 8 of crushing the core fragments, and the recovery of particle The ninth (regeneration) process 9 for mechanically regenerating aggregates. The regenerated granular aggregate can be used again in the molding of the core casting mold.

A specific example of the casting manufacturing method of the present invention will be described with reference to the flowchart of FIG. 1 . However, the materials shown here are by way of example only and are not intended to limit the invention.

The first (modulation) process 1 in this example resulted in the two aggregate mixtures A and B shown below.

Table 1 Aggregate Mixture A

Granular aggregate: silica sand (flattery sand) 100 parts by weight

Water-soluble binder: polyvinyl alcohol (JP-05) (manufactured by Japan VAM & Poval Company) 0.8 parts by weight

Cross-linking agent: 0.2 parts by weight of butane tetracarboxylic acid (manufactured by BT-W Japan's new physics and chemistry)

100 parts by weight of the aggregate mixture of the composition shown in Table 1 and 6 parts by weight of water were mixed, stirred and kneaded to make it foam, and the whipped cream-like aggregate mixture A could be obtained.

Table 2 Aggregate Mixture B

Granular aggregate: silica sand (flattery sand) 100 parts by weight

Water-soluble binder: 0.2 parts by weight of polyvinyl alcohol (JL-05) (manufactured by VAM & Poval Corporation in Japan), 1.0 parts by weight of starch (manufactured by Nichiden Chemical) and 0.4 parts by weight of citric acid (manufactured by Fuso Chemical)

100 parts by weight of the dried aggregate mixture of the components shown in Table 2 and 6 parts by weight of water were mixed, stirred and kneaded to obtain whipped cream-like aggregate mixture B.

However, in the first (modulation) process 1 in this embodiment, the necessary heating device in the production process of the resin-coated sand of the existing Joule Monte method, and the deodorizing device for removing the harmful gas generated due to the heating of the resin are also required. become unnecessary.

Next, in the cavity (not shown) of the metal mold (not shown) kept at 250°C, pressurize and fill the two kinds of whipped cream-like aggregate mixtures A and B obtained in the first (preparation) process 1, respectively. , keeping for 1 minute, the moisture in the aggregate mixture is vaporized, and after the aggregate mixture solidifies, the core casting mold is taken out from the cavity of the metal mold (second (molding) process 2).

For further illustration, this mold is assembled on other molds to form a finished mold (third (assembly) process 3). In the third (assembly) process 3 in this embodiment, the core casting mold is assembled on the main metal mold of the low-pressure casting device to form a completed casting mold and ready for pouring.

Molten metal is poured into the finished mold (fourth (pouring) process 4). In this embodiment, molten metal of aluminum alloy AC4C (at a temperature of 720° C.) is used for casting from below a low-pressure casting device (not shown). The temperature of the molten metal is 720°C, the binder can volatilize or dissolve, and the core mold removal process in the next process is easier to carry out.

During the cooling of the casting after the molten metal has solidified, the core mold is removed from the casting (fifth (draft) process 5). In the conventional Joulemont method, in order to break the core mold and remove it from the casting, a large impact force is applied to the mold after the casting is sufficiently cooled. In the method used in the present invention, the use of highly destructive core molds makes cooling and subsequent high impact forces unnecessary. The core mold can be removed using a simple method, by means of slight vibration as explained below. In the fifth (draft) process 5 in this embodiment, about 10 minutes after pouring, the casting of solidified molten metal is removed from the finished mold. Afterwards, an impact force of 20Hz, less than 20sec, and less than 1Mpa is applied to the casting at a temperature of 350°C to achieve sand shakeout, thereby completely removing the core mold. Through experiments, in the fifth (drawing) process 5, in the time within 5 minutes to 10 minutes after pouring, the impact force of 30Hz, 30sec, less than 1Mpa can also achieve sand falling so as to completely remove the core mold.

After removing the sprue and casting burrs of this casting, the sixth (heat treatment) process 6 of heat treatment is carried out to this casting. In this embodiment, the gate of the casting and the removal of casting burrs may be performed before or after the heat treatment of the casting. Even in this embodiment, after the sixth (heat treatment) process 6, it is also possible to add the core sand recovery process seven 7, crushing process eight 8 and mechanical regeneration process 110 as shown in Figure 1 .

In the casting method using metal molds, only the granular aggregate and core fragments are recovered from the core mold, and the recovered and regenerated particulate aggregate can be easily reused for molding the mold.

For ease of comparison, FIG. 2 (Prior Art) is shown as a flowchart for manufacturing castings using the Joule Montess method described in the above-mentioned Japanese Patent Office Publication No. 5-261478.

In the prior art method shown in Fig. 2, resin-coated sand is used. Usually, the resin-coated sand is purchased by the casting manufacturer from other manufacturers, and the manufacturing process 11 of the resin-coated sand is carried out at a site other than the manufacturing site of the casting. Therefore, even if the resin-coated sand is recovered and regenerated, it is difficult to reuse it for molding in contrast to the present invention.

By the method shown in Fig. 2, the casting manufacturer heats the resin-coated sand bought from the market, molds the core mold 12, the molded core mold is assembled with other molds, and the mold 13 is manufactured. Finish pouring 14 in the mold. Afterwards, the core casting mold is pulled out 15 through a shakeout furnace, and after the casting is fully cooled 16, the molding sand is completely removed 17 by demoulding, and the casting is subjected to heat treatment 18 . The demoulding process 17, the heat treatment process 18 and the process 19 of recovering the core sand containing the core fragments from the subsequent process. Of the recovered core sand, the core fragments are crushed 20 , calcined 21 and mechanically regenerated 22 at a site different from the recovery process 19 .

Compared with the conventional method shown in FIG. 2, the casting manufacturing method of the present invention shown in FIG. 1 obviously reduces the number of manufacturing processes. For example, in the fifth (casting mold removal) process 5 in the method of the present invention (Fig. 1), the destruction of the casting mold is easy to carry out, and the purpose of sand falling can be realized by a simple process, such as slight vibration. However, in the existing method ( FIG. 2 ) that is difficult to destroy the casting mold, in order to remove the casting mold, it is necessary to go through several processes of removing 15 , sufficiently cooling 16 of the casting, and demolding 17 through a shakeout furnace. And in the method of the present invention, there is no necessity of roasting 21 in the recovery and regeneration of the existing method. Fig. 3 is a graph showing the relationship between temperature and time in the fifth (mold removal) process 5 and the sixth (heat treatment) process 6 in the embodiment of the present invention. For comparison, Fig. 4 (Prior Art) similar to Fig. 3 is provided, which shows a diagram of the prior art versus the mold removal and heat treatment process in the method of the present invention.

In the prior art, after the casting is sufficiently cooled (process 16 of FIG. 2 ), shakeout is realized by demoulding (process 17 of FIG. 2 ), and then the temperature is raised again for T6 treatment. Therefore, not only the cooling time shown in FIG. 4 but also heating time and energy are required for heat treatment.

In the embodiment of the present invention shown in FIG. 3, after pouring at 720° C., during the mold removal process 5, the core mold is taken out of the casting after the molten metal has solidified and the casting is taken out. Afterwards, it is not necessary to perform solution treatment (heat treatment) directly after cooling the cast product sufficiently to give a large impact in order to remove the core mold. Therefore, not only the cooling time, reheating time for heat treatment is shortened, but also the consumed energy is saved and the number of processes is reduced. Castings do not have to be cooled to 100°C, cooling to 300°C also has the effect of saving energy.

The above-described embodiments are illustrative rather than limiting of the present invention, and various changes and modifications can be made by those skilled in the art without departing from the purpose and gist described in the claims.

Claims (12)

1. a manufacture method for foundry goods, is characterized in that, it comprises:

Particle shape aggregate at least containing a type, water-soluble binder at least containing a type, and be mixed to form aggregate mixture by adding water, this aggregate mixture is stirred and make it foam process, wherein, described water-soluble binder is starch, and the consumption of described water-soluble binder is the 0.1-5.0wt% of particle shape aggregate;

Aggregate mixture after foaming is filled in casting mold space, aggregate is solidified the moisture evaporation in the aggregate mixture after filling, use above-mentioned aggregate mixture to carry out the process of moulding to mold, wherein make the moisture accumulation heart portion in the mould contained in the bubble that disperses in aggregate mixture and binding agent;

The process of mold made by the mold being mounted to pairing by using the mold of at least one that goes out of this aggregate mixture moulding;

To the above-mentioned process completing casting molten metal in mold;

Solidify in later foundry goods cooling period at above-mentioned motlten metal, by the process that above-mentioned mold removes from above-mentioned foundry goods, wherein, above-mentioned mold removing process is the process imposing vibration to above-mentioned mold, and the process imposing vibration to above-mentioned mold is apply with below 1Mpa less than 30Hz, process less than the impulsive force of 30sec to above-mentioned mold in the time after being cast within 5 minutes and even 20 minutes;

To the process that above-mentioned foundry goods is heat-treated.

2. the manufacture method of foundry goods according to claim 1, is characterized in that, the mold of at least one gone out by above-mentioned aggregate mixture moulding is core mold, and above-mentioned pairing mold is main mold.

3. the manufacture method of foundry goods according to claim 2, is characterized in that, above-mentioned main mold is metal mold.

4. the manufacture method of foundry goods according to claim 2, is characterized in that, above-mentioned main mold is sand mold.

5. the manufacture method of foundry goods according to claim 1, is characterized in that, also includes the process that process and being carried out by the particle shape aggregate after this recovery that above-mentioned particle shape aggregate reclaims regenerates.

6. the manufacture method of foundry goods according to claim 5, is characterized in that, above-mentioned recovery and regeneration particle shape aggregate reuse in casting mold.

7. the manufacture method of the foundry goods according to claim 5 or 6, is characterized in that, the reclaiming process of above-mentioned particle shape aggregate is mechanical regeneration.

8. the manufacture method of foundry goods according to claim 1, is characterized in that, above-mentioned foundry goods is aluminium alloy castings or Mg alloy castings.

9. the manufacture method of foundry goods according to claim 8, is characterized in that, above-mentioned heat treatment is T6 process or T7 process.

10. the manufacture method of foundry goods according to claim 1, is characterized in that, above-mentioned foundry goods is the foundry goods of cast iron or cast steel or Ferrious material alloy.

The manufacture method of 11. foundry goods according to claim 1, is characterized in that, above-mentioned foundry goods is copper-alloy casting.

The manufacture method of 12. 1 kinds of foundry goods, is characterized in that, it comprises:

Particle shape aggregate at least containing a type, water-soluble binder at least containing a type, and be mixed to form aggregate mixture by adding water, this aggregate mixture is stirred and make it foam process, wherein, described water-soluble binder is starch, and the consumption of described water-soluble binder is the 0.1-5.0wt% of particle shape aggregate;

This aggregate mixture is stirred and makes it foaming, aggregate mixture after foaming is filled in casting mold space, and aggregate is solidified the moisture evaporation in the aggregate mixture after filling, above-mentioned aggregate mixture is used to carry out the process of moulding to core mold, wherein, the moisture accumulation heart portion in the mould contained in the bubble that disperses in aggregate mixture and binding agent is made;

At least one above-mentioned core mold and metal mold are carried out the process being assembled into mold;

To the above-mentioned process completing the motlten metal of cast aluminum alloy in mold;

In foundry goods cooling period after above-mentioned motlten metal solidifies, by the process of above-mentioned core mold removing from above-mentioned foundry goods, wherein, above-mentioned mold removing process is the process imposing vibration to above-mentioned mold, and the process imposing vibration to above-mentioned mold is apply with below 1Mpa less than 30Hz, process less than the impulsive force of 30sec to above-mentioned mold in the time after being cast within 5 minutes and even 20 minutes;

The heat treated process of T6 or T7 is carried out to above-mentioned aluminium alloy castings.

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