WO2014048066A1

WO2014048066A1 - New pouring process for a core/mold package of automobile engine castings

Info

Publication number: WO2014048066A1
Application number: PCT/CN2013/001135
Authority: WO
Inventors: Bingxiang HE
Original assignee: He Bingxiang
Priority date: 2012-09-27
Filing date: 2013-09-25
Publication date: 2014-04-03
Also published as: CN102921897B; CN102921897A

Abstract

A pouring process of a cold box core/mold package (1) of automobile engine iron castings inside a flask (3) filled with dry sand (4) includes following steps. By using such dry sand (4) and some other filling material (5), the flask (3) which is designed with a vacuum suction structure is filled to bury the core/mold package (1) inside. After compaction, such dry sand (4) and such other filling material (5) hold and squeeze the core/mold package (1). The vacuum suction structure increases the hardness of such dry sand (4) and such other filling material so as to give support on the back of core/molds of the core/mold package (1). Cooling-in-flask is also realized with such pouring process.

Description

NEW POURING PROCESS FOR A CORE/MOLD PACKAGE OF AUTOMOBILE

ENGINE CASTINGS

Technical Field

This invention relates to the foundry technology, specifically, is a new pouring process for the cold box core/mold package of the automobile engine iron castings .

Technical Background

The automobile engine casting is one of the most difficult kinds of the castings due to its complex structure and the high requirement on the dimensions accuracy, surface quality and the material strength. So, its research and development were made extensively by the professional person in the foundry area during the past many years. And the fruitful results were achieved, which have made the considerable progress in the foundry technology of the automobile engine castings. However, with the new development and progress of the engine itself, the foundry industry has to face the new requirements and challenge.

The process of the core/mold package of the automobile engine castings was developed in the case of the traditional technology can not satisfy the new requirements any more. Among the traditional technology, the green sand process is the most popular process to produce the automobile engine iron castings. In this process the internal cavity and some part of the external shape of the casting was formed by the cores, and the other most external shape will be formed by the green sand mold. The pouring system(including also feeder, filter and so on) is formed by the mold mainly with the assist of the cores. But in the process of the core/mold package of the automobile engine casting, all the shape of the casting will be formed by the cores. That is to say, the external cores which will form the external shape of the casting actually play the role of the traditional green sand mold. So, this kind of cores are also called the external mold cores, or the core/molds. The design of the pouring system(including also feeder, filter and so on) will depend on the selection of the pouring process of the core/mold package. For the introduction of the core/mold package and its preparation methods may see the reference as the patent documents 200720187589.6(Patent application number).

After the introduction of the core/mold package process for the automobile engine castings, the external mold cores may not be made too thick to be very strong due to the expensive cost of the core process. Normally the external core/molds are not strong enough as the traditional green sand mold to satisfy the strength need of the casting during the pouring and solidification. So, normally the core/mold package may not be poured directly and independendy. There are several pouring process as follows are in the practice for the core/mold package: 1. As the regular core package, the core/mold package will be set in the green sand mold in the flask, the flask to be closed, then to be poured. 2. As the regular core package, the core/mold package will be set in the no-bake sand mold in the flask, the flask to be closed, then to be poured. 3. As described in the documents 99114622.0(Patent application no.) the cast process of the automobile engine block, by using the clamping metal hoop around the core/mold package to clamp the core/mold package and put it on the workshop floor, which will be surrounded by the sand on the floor, then to be poured. 4. As described in the documents 201020199311.2(Patent application no.) the pouring fixture for the core/mold package of the automobile engine block castings, the bottom part of the core/mold package will be set in the customized pouring fixture, and also by using the clamping metal hoop to clamp the core/mold package, then to be poured.

The pouring process No.l above-mentioned has many advantages, such as: plenty of the experience and high reliability on the process design after so many years development, possibility to realize the automatic system to make the big serious production, flexibility for the different product kinds and also for the different material, possibility to realize the cooling-in-flask to instead of the separate stress-relief aging treatment. But it has its own big shortage: the investment on the equipment and the operating cost are both very high. Comparing the pouring process No.l, the pouring process No.2 above-mentioned will reduce significantly the investment cost of the equipment, but the operating cost will be increased greatly. So, normally it's only possible to be used for the low-volume product, not for the big serious production. The pouring process No.3 and No.4 have their similarities: to use the metal hoop to clamp the core/mold package to avoid the double molding (i.e. in the case of the external shape of the casting has been prepared by the core/mold package, to mold again, and then to set the core/mold package to this mold for the pouring) in the process No.l and No.2, which will save the cost of the equipment investment and the operation. But meanwhile it brings some common shortages or limits for the production: to increase the production cost of the core/mold package due to the thickness of the external mold core has to be increased in order to enhance its strength for the pouring, weak flexibility for the different material, lower practice ability on the process measures, less safety for the pouring operator due to the less protection for the leak-out or splash of the liquid iron, lower flexibility for the different products, difficult to realize the standard automatic system for the production, no possibility to realize the cooling-in-flask. Besides these common shortages or limits, they also have their own disadvantage: the pouring process no.3 is the primary process. The quality and accuracy of the produced casting are poor. The operation environment is bad. And the human elements play the important role on the production. Comparing with the pouring process No.3, the pouring process No.4 has had the improvements. But it's limited to produce always 2 pieces of the casting and to produce the different castings with big difference on the size, they have to use the different bottom fixture, which will bring the new difficulty for the production of the different product.

So, from the above-mentioned the technical background it can be seen: all the existing pouring process for the core/mold package of the automobile engine iron casting have their own shortages or limits. There is still no one sound process which could convenient to solve the technical and technology problem and to realize the automatic system for the serious production, and meanwhile could reduce the equipment investment cost and save the operating cost, also could avoid the double preparation and waste by taking advantage of the character of the core/mold package.

Detailed Description of the Invention

In order to solve the problems from the shortages or limits of the existing pouring process, this invention take into its account the following technology needs or process objective:

1. Reduce the cost of the equipment investment and the operating

Due to the core/mold package has already prepared the external shape and the internal cavity of the automobile engine casting completely, it brings the possibility to avoid the waste from the double preparation on the mold, and reduce the general cost of the equipment investment and the operation.

2. To realize the standardized automatic system, which will be able to guarantee the repeatability of the product quality with the efficient operation

The market need of the most automobile engine iron castings are in large volume, and also the requirements on the repeatability of the process and the product quality are very high. The standardized automatic system will be needed for the efficient production with the good repeatability of the process and the product.

3. High flexibility on the different products and the different materials.

There are many different kinds of engine due to the different capacity and the different emission standard. Also even in the same engine manufacturer, there will be some different kinds of iron material to be applied for the engine. So, there will be many kinds of the different engine iron casting. As the new process for the automobile engine casting, it shall have a very high flexibility on the different kinds of the products and also the different kinds of the material.

4. Good practice ability on the process measures

The engine iron casting is one kind of the most complicated castings. It need always the certain long period to make the development and test. The different process measures will be taken to solve the various technical or technology problems. As the new process for the automobile engine casting, it shall have the sufficient possibility to practice the process measures to solve the related problems to ensure the stable production of the good quality casting.

5. Possible to realize the cooling-in-flask to instead of the stress-relief aging treatment in order to save the general manufacture cost.

After the analysis on the shortage or the limits of the existing pouring process and the full consideration on the different technology needs of the core/mold package, this invention will invent the new pouring process for the core/mold package of the automobile engine iron casting, which will make it possible to realize all the process objective of the package.

For the convenience and the exactness of the description of the process, some related terms will be explained as follows first:

Automobile engine iron casting: refers to the cylinder block, cylinder head and crankcase frame of the automobile engine which will be produced in iron material.

Core/mold package: refers to the core/mold packages to be used to product the automobile engine iron casting, which will be assembled by the cold box cores completely or mainly by the cold box cores with some cores by hot box or even the other process.

Dry sand: refers to the original sand without any binders or additives, which are used normally as the mold sand or the core sand in the foundry. It will be used as the main filling material.

Second filling material: refers to the filling grains with the much higher density than the dry sand, such as the iron or steel shot. The general process steps of the invention is as follows:

Step No.l: to discharge the dry sand to the bottom of the flask with vacuum structure as bottom sand. It will be called the first filling.

Step No.2: to set the prepared core/mold package(with the gating system) to the top of the bottom sand for the relatively centralized position and to use the specialized fixture to adjust and fix its position inside the flask.

Step No.3: to make the second filling by discharging the dry sand around the core/mold package. It depends on the technology need of the products whether the second filling material will be used for the second filling.

Step No.4: to compact the filling material

Step No.5: to remove the fixture and add some more dry sand to the flask.

After step No.5, the steps will be the different groups of type A and type B

Type A. For the products to be poured without the vacuum suction application

Step No.6: to make the pouring

Step No.7: to make the cooling-in-flask

Type B. For the products to be poured with the vacuum suction application

Step No.6: to film and cover the top open of the flask by the plastic film.

Step No.7: to start the vacuum suction on the flask to make the filling material to get hard enough to be ready for the pouring. Step No.8: to make the pouring

Step No.9: to keep the vacuum suction for the certain minutes before its stop

Step No.10: to make the cooling-in-flask

Remark: After the cooling-in-flask, the castings will be turned into the next operation.

Generally, this invention is a new pouring process for the core/mold package of the automobile engine iron castings. In the standardized flasks with the vacuum suction structure, by using the dry sand(and second filling material) to fill and surround the core/mold package and its gating system. The filling material will be compacted after the filling in order that the core/mold package and its gating system will be hold and squeezed by the filling material, and will get the good supports on their back from the filling material. If this support is strong enough to satisfy the technology need of the casting during their pouring and solidification, the prepared flasks could be poured directly. Otherwise the operation for the vacuum suction application will be needed for the flasks. By the vacuum suction with the film on the top of the open of the flask, the filling material will get harder and make the more strong support on the back of the core/molds of the core/mold package and also for the gating system. After the filling material are hard enough to make the enough strong support on the core/mold package, the flask will be poured. And depending on the technology need of the casting, the vacuum suction will be kept for the certain minutes for the sound solidification of the casting. After the stop of the vacuum suction, the flasks will keep the casting inside for the cooling of the casting for certain hours as the technology requirement. Then the flasks with the casting will be moved to the next operation.

The characteristics of the invention: to use the standardized flask with the structure for the vacuum suction; to use the dry sand and some other second filling material to fill the flask for the core/mold package, which are very easy to be reused by recycling; possible to use the vacuum suction to increase the hardness of the filling materials; the external mold core doesn't need to be made specifically thick to enhance its own strength, because it will be supported by the filling material and provide the support as strong as it need for the pouring and solidification; depending on the size of the casting, it's possible to arrange the core/mold package for the single or multiple casting in the same flask, and also possible to chose horizontal or vertical pouring process as they need; the dry sand as the filling material may be chosen the same sand as used for the preparation of the core/mold package, which will bring the convenience for the sand separation, reclaim and reuse; to realize the cooling-in-flask of the casting too.

Effect of the invention

]. Instead of the molding of the green sand or no-bake sand, by using the dry sand(and the secondary filling material) to fill the flask to hold and squeeze the core/mold package. It doesn't need the huge molding system and the complicated sand preparation system. This will reduce evidently the cost of the equipment investment, and avoid the waste from the double molding to save the operation cost.

2. By means of using standardized flask with the same dimension, it could realize the automatic production system needed by the serious production of the automobile engine castings, which could also ensure the quality stability and the process repeatability.

3. By using the dry sand as the main filling material , the operation for the pouring of the core/mold package will be prepared inside the flask. The process will have the common characters with the green sand process, which has been used to produce the automobile engine castings for many years and a lot of experience of the technology and the process have been obtained. Most of the technology measures of the green sand could be transplanted to the process of the invention. It brings the abundant basis of the technology for the invention process.

4. The core/mold package will be hold and squeezed in the flask by the filling of the filling material. And also when needed, it will be possible to use the vacuum suction to inaease the hardness of the filling material to make the stronger support on back of the core/mold package, in order that it will satisfy the technology need of the casting and meanwhile it could save the material cost of the core/mold package. Furthermore the vacuum suction will increase the pressure from the pressure head of the pouring system. It will help the filling of the molten iron into the cavity. Especially for the complex structure and difficult castings with the thin-wall, the vacuum suction could be taken advantage to solve the problems from the cavity filling of the castings.

5. The contact between the filling material with the core/mold package is the type of " Zero Clearance". Comparing with green sand process, it will reduce the fit clearance between the mold and the core/mold package completely. And also avoid the lack of the support from the green sand mold on the hollow part of the back of the core/molds, which was designed to reduce the weight of the core mold in order to save the package material cost.

6. If the dry sand used as the filling material to be taken as the same sand as used for the core/mold package, the sand recycle will be very easy and its energy cost will be reduced considerably. Because the dry sand doesn't need use bentonite, coal powder or any other additive comparing with the green sand process, and the core/mold package will be burned well to be collapsed after the pouring of the casting, the separation and the reclaim of them will get much simple and easy.

7. To realize the Cooling-in-flask instead of the stress-relief treatment will save the manufacture cost of the casting.

Brief description of the attached drawings

Fig.l: Sample of the core/mold package(including the gating system) .

Fig. 2: Sketch of the flask with the vacuum suction structure.

Fig.3: Sketch of the flask filled with the bottom sand

Fig.4: Sketch of the core/mold package (including gating system) setting in the flask on the top of the bottom sand.

Fig. 5: Sketch of the second filling of the flask.

Fig. 6: Sketch of the second filling material to be filled into the flask.

Fig.7: Sketch of the conclusion of the second filling.

Fig. 8: Sketch of covering the top open of the flask with the plastic film

Fig. 9: Sketch of the vacuum suction operating to the flask.

Fig.10: Sketch of the pouring with the vacuum suction operating .

Detailed operation of the invention

The operation of the invention will be described as follows in the further details with the aid of the attached drawings.

Before the start of the operation steps of the invention, the core/mold package 1 of the automobile engine castings shall have been prepared and also have been assembled with the gating system 2 and fixed together, see Fig.l. Due to the advantages of the cold box process as efficiency, less deformation, lower gas evolution, good operation environment, lower manufacture cost and so on, as much as possible of the cores and the core/molds of the core/mold package 1 shall be designed to use the cold box process. And the back side of the core/molds shall be made conforming design by using the gridding strengthening rib structure, in order to reduce the sand consumption to save the cost and to be strong enough for the technology need.

See Fig.2 the flask 3 with vacuum suction structure is equipped with the vacuum suction box in the bottom part of the flask 3. And the suction connector is designed on the side of the box, which will be used to connect to the vacuum operation unit of the system. The size of the flask shall be designed under the consideration on all the product of the system. As the first step of the operation of the invention, the dry sand 4 will be filled to the bottom of the flask 3 to be the bottom layer sand. This operation is called the first filling. If the bottom side of the core/mold package is relative flat, the bottom layer sand will be 100-150mm thick. Otherwise the bottom layer sand shall be filled more and to prepare some shape as need of the bottom side of the package, in order that the core/mold package will be set and adjusted conveniently. Under this case the thickness of the bottom layer sand under the package shall be guaranteed at least 100mm after its setting and adjustment, see Fig. 3.

The prepared core/mold package 1 (including the gating system 2) of the automobile engine casting will be set and relatively center in the flask on the bottom layer sand. By using the specially designed fixture, the core/mold package 1 and the gating system 2 will be adjusted and fixed its position in the flask 3, see Fig 4.

Then the second filling will be done around the core/mold package 1 (including the gating system 2). The general operation of the second filling is showed as Fig.5. If the technology strength need on the part of the core/molds or the part area of the core mold is higher than others during the pouring or the solidification of the casting, the multiple filling material will be the solution. In this case, the second filling material 5 will be filled to those area or position of the package before the dry sand 4, see Fig 6. To make this filling, the frame or separate plate will be used to hold the second filling material 5 in the need area. The dry sand 4 will be filled on their back. After the filling of the dry sand 4 the frame or separate plate will be removed away and to let the dry sand 4 to keep the second filling material 5 on their proper area.

After the second filling operation, the compaction will be done in the flask. Due to the good flowability of the dry sand 4 and the second filling material 5, the compaction will be done by the manual operation or the vibration. The next operation is removing the fixture away and add the dry sand to the flask till the top of the dry sand 4 is 10-15mm to the top of the pouring basin. Finally nearly the complete core/mold package 1 (including the gating system) will be buried, just the part of the pouring basin is outside the dry sand 4. See Fig. 7.

For the product which doesn't need vacuum suction during their pburing process, the pouring will be done directly just after the second filling and compaction. Otherwise for the product which need the vacuum suction, the process operation will be as follows:

To film the flask: by using the plastic film to cover the top of the dry sand 4 and the top open of the flask 3, the sealing for the vacuum suction is prepared. The plastic film 6 shall exceed the edge of the flask 3 about 10-15mm. See Fig. 8.

After the vacuum suction connector on the side of the flask is connected to the connector of the vacuum unit of the system, the vacuum suction will be started for the flask 3. See Fig. 9. The filling material inside the flask will get hard and strong after the vacuum working on them. After their hardness and strength reached the technology requirement, the preparation for the pouring is ready and the pouring will be operated. See Fig. 10. After pouring the vacuum suction will be kept for the certain long time which depend the technology need of the casting solidification.

After the vacuum suction stopped, the casting will get cooling inside the flask under the regular air pressure. After the cooling, the flask with the casting will be moved to some other operations.

It's worthy of emphasis that the vacuum degree of the system is adjustable on the need of the product. The vacuum suction on the flask will simultaneously increase the pressure head of the pouring system too when it's working for the hardness of the filling material. The increased pressure head will be good help for the filling of the casting, especially for some difficult casting or the difficult area of the casting. But it's also possible to bring some new problems to the pouring process such as entrainment of air, effect on stabilization of the pouring. So, the vacuum degree need to be decided and applied to the specific casting under the consideration of its all the possible factor.

Remark: The above description is for the typical operation of the process of the invention. It's only for the further explanation of the invention, not to make any limit on the different solution of the process. Even the description of the invention has made the detailed description on the operation, but all the foundry person shall understand that it's still possible to make some change or substitute. All the technical solution or improvement which doesn't deviate the spirit and extent of the invention will be covered by the scope of the claim of the invention.

Claims

1. A pouring process used for the cold box core/mold packages of the automobile engine iron castings inside the flask filled with the dry sand; by using the dry sand (and some other filling material), the flask which was designed with the vacuum suction structure will be filled to bury the prepared cold box core/mold package (including gating system) inside; after the compaction, the filling material will hold and squeeze the core/mold package; the vacuum suction structure brings the possibility to increase the hardness of the filling material in order to improve the support on the back of the core/molds of the package to be further and strong enough, which will be the technology need of the casting during its pouring and solidification; and the cooling-in-flask will be realized too; characterized that in the standardized flask it doesn't need to mold anymore but still be able to give the strong enough support on the back of the core/molds of the cold box core/mold package to satisfy the technology need of the casting during its pouring and solidification; very convenient to realize the automatic production system and most of the technology measures of the traditional process could be transplanted to it.

2. A pouring process used for the cold box core/mold packages of the automobile engine iron castings inside the flask filled with the dry sand according to claim 1, characterized in that it's specifically for the cold box core/mold package of the automobile engine iron casting; the cold box core/mold package means the package will be assembled by the cold box cores completely or mainly by cold box cores, only a few or individual core are in some other processes as hot box.

3. A pouring process used for the cold box core/mold packages of the automobile engine iron castings inside the flask filled with the dry sand according to claim 1, characterized in that it make use of the flask which could be standardized.

4. A pouring process used for the cold box core/mold packages of the automobile engine iron castings inside the flask filled with the dry sand according to claim 1, characterized in that it take the dry sand as the main filling material to fill the flask to bury the core/mold package; the dry sand could be the same sand as used for the core/mold package, or the different sand.

5. A pouring process used for the cold box core/mold packages of the automobile engine iron castings inside the flask filled with the dry sand according to claim 1, characterized in that the second filling material could be used besides the dry sand as the main filling material when the flask is filled to bury the core/mold package; normally the dry sand will be the majority of the filling material, just using the second filling material as assistance; or it just use the dry sand completely; but in some case the castings are suitable to be poured with the second filling material; the second filling material will be used in high percent, even completely without any dry sand.

6. A pouring process used for the cold box core/mold packages of the automobile engine iron castings inside the flask filled with the dry sand according to claim 1, characterized in that the flask is designed with vacuum suction structure; but it doesn't mean all the casting need the vacuum suction operation; it depending on the technology need of the casting, to be poured with the air pressure or under the vacuum suction operation.