Production method of sand casting thin-wall casting

Abstract

The invention provides a production method of a sand casting thin-wall casting, and belongs to the technical field of sand casting. Comprising the following steps that (1) a three-dimensional model of the pre-printed thin-wall casting is designed according to the size requirement of the thin-wall casting, and a sand mold, a sand core, a pouring system, a dead head and an exhaust system of the thin-wall casting are obtained by conducting 3D printing with silica sand as a raw material through a 3D printing device; (2) after the sand mold, the sand core, the pouring system, the riser and the exhaust system are assembled, the sand mold, the sand core, the pouring system, the riser and the exhaust system are assembled with the sand box; and (3) during pouring, molten iron dispersedly enters a casting mold from a lower pouring system, and cold molten iron entering the casting mold in advance enters a riser to be discharged out of a mold cavity. The method overcomes the defects that in existing thin-wall casting production, during casting production, the casting is prone to skin penetration, cold shut and insufficient pouring, and machined parts do not have obvious steps.

Description

Technical Field

[0001] The invention belongs to the technical field of sand casting, and in particular relates to a production method of a sand casting thin-wall casting. Background Art

[0002] Thin-walled frame castings and thin-walled box castings often appear in sand casting production. Some castings are large in size, thin in wall thickness, and have high material requirements, making casting very difficult. Specifically, there are several difficulties in the production of sand mold thin-walled parts: 1. Sand casting, the thermal insulation performance of the molding sand is poor, the heat dissipation is fast, and the molten metal liquid will solidify quickly after entering the mold, and the casting is prone to cold shut defects; 2. Box castings are relatively complex, the resistance to the molten iron flow is large, and the fluidity is poor. When the molten iron flows in thin walls and large areas, the temperature of the molten iron drops quickly, causing insufficient pouring defects. 3. The minimum wall thickness of casting production is also related to the type of alloy. Cast copper and cast aluminum alloys have low melting points and good fluidity; cast iron and cast steel alloys have high melting points and poor fluidity. Among cast iron alloys, gray cast iron solidifies layer by layer with good fluidity, while ductile iron solidifies in a dendritic manner with poor fluidity.

[0003] Based on the above problems, improvements are proposed. Summary of the invention

[0004] The technical problem solved by the present invention is to provide a production method for sand casting thin-walled castings. The purpose of the present invention is to solve the defects of existing thin-walled casting production, such as easy penetration, cold shut, insufficient pouring, and no obvious steps in the parts after processing, etc. during casting production by designing a sand casting production method for thin-walled box-type castings.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A method for producing a thin-walled casting by sand casting comprises the following steps:

[0007] Step 1): designing a pre-printed three-dimensional model of a thin-walled casting according to the size requirements of the thin-walled casting, and using a 3D printing device to perform 3D printing using silica sand as a raw material to obtain a sand mold, a sand core, a pouring system, a riser, and an exhaust system of the thin-walled casting;

[0008] Step 2): After the sand mold, sand core, pouring system, riser, and exhaust system are assembled, they are assembled with the sand box;

[0009] Step 3): During pouring, molten iron disperses into the mold from the pouring system below, and the cold molten iron that entered the mold earlier is discharged from the mold cavity through the riser.

[0010] To further limit the above scheme, in the above step 1), the pouring system adopts a bottom pouring form, and the inner gate of the pouring system is evenly distributed in multiple channels.

[0011] To further limit the above scheme, in the above step 1), the sand mold adopts a horizontal split type parting.

[0012] To further limit the above scheme, in the above step 1), the riser is a duckbill riser, and a plurality of risers are provided and evenly distributed on the top of the casting.

[0013] To further limit the above scheme, in the above step 1), the cross-section of the inner runner and the riser diameter of the pouring system and the exhaust plate of the exhaust system are all wide and flat rectangular sections.

[0014] To further limit the above scheme, in the above step 3), the pouring temperature during pouring is 1360°C to 1390°C.

[0015] The advantages of the present invention compared with the prior art are:

[0016] 1. This solution uses 3D printing to make sand molds, sand cores and other casting parts. For thin-walled castings with high dimensional accuracy requirements, it is beneficial to process obvious step surfaces to ensure product quality;

[0017] 2. This solution is to produce thin-walled castings of larger sizes. The inner gates of the pouring system are evenly distributed, so as to prevent the molten iron from flowing horizontally for too long in the mold. During the flow process, the temperature drops, causing insufficient pouring.

[0018] 3. In this scheme, in order to ensure that the molten iron has a higher temperature in the mold cavity when pouring thin-walled castings, the cool molten iron that entered the mold earlier is discharged from the mold cavity through the riser. Therefore, the function of the riser in this method is mainly to allow the cold molten iron that entered the mold first to enter the riser to avoid shrinkage in the thin-walled parts of the casting. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a cross-sectional view of a filling box in an embodiment of the present invention;

[0020] Figure 2 Schematic diagram of a 3D printing pouring system for a filling box in an embodiment of the present invention. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] See also Figure 1-2 , details of the embodiments of the present invention.

[0023] A production method for sand casting thin-walled castings. The method aims to produce various specifications of ductile iron thin-walled castings by designing a sand casting production method for thin-walled box-type castings. The casting method is also suitable for gray cast iron, cast steel, non-ferrous castings, etc.

[0024] This embodiment takes a filling box as an example to introduce a production method for a complex thin-walled box-body ductile iron casting.

[0025] like Figure 1 The filling box cross-sectional view shown in the figure has the following problems in the current production process: 1. The filling box has relatively large dimensions, with a length × width × height of 1250mm × 585mm × 570mm, and a cast iron wall thickness of only 8mm, which belongs to the thin-walled box type casting; the casting is prone to defects such as skin penetration and cold shut during casting production; 2. The casting material is QT450-10, and the molten iron has poor fluidity, which is prone to insufficient pouring during casting production; 3. The casting size accuracy requirements are high, and the difference between the machined surface and the non-machined surface in some parts is only 2mm. If the size deviation of the casting blank is large, the machining step of the casting shape will be flush with the surface of the casting blank, and there will be no obvious step on the part after processing; 4. Regardless of whether the filling box is placed horizontally or vertically for pouring, due to the large size and thin wall thickness of the casting, the molten iron temperature drops quickly during pouring, and the casting is likely to have skin penetration and insufficient pouring.

[0026] In order to solve the above problems existing in the production of filling boxes, the present invention provides a new method for producing thin-walled castings, which specifically includes the following steps:

[0027] Step 1): Due to the high dimensional accuracy requirements of the filling box, such as Figure 1 The filling box 1 shown is designed to pre-print a three-dimensional model of the filling box casting according to the size requirements of the filling box, and a 3D printing device is used to obtain a sand mold, a sand core, a pouring system 2, a riser 3, and an exhaust system 4 of the filling box casting by 3D printing with silica sand as a raw material;

[0028] In this embodiment, the sand mold of the filling box adopts a horizontal split type mold, and the molten iron enters the mold in a dispersed manner from the bottom. There are 12 inner gates. The multiple inner gates are to allow the molten iron to fill the mold quickly and avoid the cold shut of the casting caused by the molten iron flowing too long.

[0029] In this embodiment, 9 duckbill risers and 7 exhaust plates are placed on the top of the casting. The main function of the riser is to allow the cold molten iron that enters the mold first to enter the riser to avoid shrinkage in the thin-walled parts of the casting, and at the same time play a role in venting the cavity.

[0030] In this embodiment, the ingates, riser diameters, and exhaust plate cross-sections are wide, flat rectangular sections, mainly to prevent thin-walled parts from being damaged when cleaning the ingates.

[0031] In this embodiment, the pouring system adopts the bottom pouring form, 12 inner pouring channels, and a thin and wide cross-section, so that the molten iron can enter the mold evenly and the molten iron in the mold can rise steadily. Figure 2 shown.

[0032] In this embodiment, the sand core is printed to be hollow, which not only reduces the weight of the sand core but also facilitates the exhaust of the sand core. The upper mold sand core is printed, and the riser and exhaust plate are printed as a part of the height, and the riser height is printed to be 90mm high.

[0033] Step 2): After the sand mold, sand core, pouring system, riser, and exhaust system are assembled, they are assembled with the sand box. After the sand core is placed in the sand box, the surrounding of the casting is filled with molding sand, and the pouring channel, riser, and exhaust plate are raised by 100mm, and a pressure iron is placed on the sand mold.

[0034] Step 3): During pouring, the molten iron enters the mold from the pouring system below in a dispersed manner, and the cold molten iron that entered the mold earlier is discharged from the mold cavity through the riser. Pouring temperature: Because it is a thin-walled part, the pouring temperature is determined to be 11390℃.

[0035] According to the above process method, the size of the cast castings meets the requirements of the drawings and technical documents, the surface of the castings is smooth, and the inspection is qualified.

[0036] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0037] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for producing thin-walled castings by sand casting, characterized in that: The following steps are involved: Step 1): designing a pre-printed three-dimensional model of a thin-walled casting according to the size requirements of the thin-walled casting, and using a 3D printing device to perform 3D printing using silica sand as a raw material to obtain a sand mold, a sand core, a pouring system, a riser, and an exhaust system of the thin-walled casting; Step 2): After the sand mold, sand core, pouring system, riser, and exhaust system are assembled, they are assembled with the sand box; Step 3): During pouring, molten iron disperses into the mold from the pouring system below, and the cold molten iron that entered the mold earlier is discharged from the mold cavity through the riser.

2. The method for producing a thin-walled casting by sand casting according to claim 1, characterized in that: In the above step 1), the pouring system adopts a bottom pouring form, and the inner gates of the pouring system are evenly distributed in multiple channels.

3. The method for producing a thin-walled casting by sand casting according to claim 1, characterized in that: In the above step 1), the sand mold is split horizontally.

4. The method for producing a thin-walled casting by sand casting according to claim 1, characterized in that: In the above step 1), the riser is a duckbill riser, and a plurality of risers are provided and evenly distributed on the top of the casting.

5. The method for producing a thin-walled casting by sand casting according to claim 1, characterized in that: In the above step 1), the cross section of the inner runner and riser diameter of the pouring system and the exhaust plate of the exhaust system are all wide and flat rectangular sections.

6. The method for producing a thin-walled casting by sand casting according to claim 1, characterized in that: In the above step 3), the pouring temperature during pouring is 1360°C to 1390°C.

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