Complex thin-wall casting forming and mud core repairing method
By using high-temperature resistant fiber belt winding repair in the molding process of complex thin-wall castings, the problems of core cracks and quality defects are solved, and the yield and production efficiency of castings and cores are improved.
Patent Information
- Application Number
- CN202411903775.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-23
- Publication Date
- 2025-03-21
AI Technical Summary
During the molding process of complex thin-wall castings, the core is prone to cracks during the core making and drying process, resulting in quality problems, such as pores, iron-clad sand and cold iron adhesion, causing the casting to be scrapped, and the existing repair methods cannot effectively solve these problems.
High-temperature resistant fiber belts are used to wind and repair the parts that need to be formed or repaired. By pre-wrapped high-temperature resistant fiber belts, we prevent wet water from infiltration or cold iron from contacting the castings, thereby avoiding quality defects.
It improves the yield rate of castings and cores, reduces the scrap rate, improves production efficiency and casting quality, and reduces production costs and resource waste.
Smart Images
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Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of casting, and in particular relates to a method for molding a complex thin-wall casting and repairing a mud core. Background Art
[0002] Casting is one of the basic processes in the modern machinery manufacturing industry. It is a relatively economical method for blank forming, and it is more economical for parts with complex shapes. For example, complex castings such as the cylinder block, cylinder head, and box body of the engine cannot be formed without casting.
[0003] The cylinder block and cylinder head of the engine are the core components of the diesel engine and one of the most critical components of the diesel engine. They require high dimensional accuracy and high inner cavity cleanliness. Therefore, the castings are not allowed to have slag inclusions, sand inclusions, pores, looseness, cracks and other casting defects that affect product performance and water pressure and air pressure tests. Casting is very difficult.
[0004] The dimensional accuracy and inner cavity cleanliness of castings are mainly affected by factors such as molding (core) method and mold accuracy. In previous production practices, the repair of complex casting cores, the cleaning of thin walls and small cross-sectional areas, and other issues were bottlenecks in the production process, seriously restricting the smooth progress of production.
[0005] Take the cylinder head as an example. The inner cavity of the cylinder head is entirely formed by the core. In particular, the core of the upper and lower water jackets of the cylinder head has a complex shape, uneven wall thickness, and small sections at the local connection parts. The problem of difficult cleaning has long plagued the production workshop. The following defects are prone to occur during the production process:
[0006] 1. During the core making and drying process, due to the small size of the local cross-section of the core, the core is prone to cracks at the small cross-section if the operation is not done carefully. In severe cases, the core may even break. Since it cannot be repaired, the core is scrapped in batches. During the casting process, the gas in the core is discharged from the cracks, resulting in pore defects. At the same time, molten iron invades the core from the cracks, forming iron-encased sand defects that cannot be cleaned, causing the casting to be scrapped. Figure 1 The inner cavity core diagram of a cylinder head of a certain type is shown in FIG. Figure 1 (a) A and Figure 1 The areas shown at B in (b) are all small cross-sections.
[0007] 2. For the core with small connection parts or elongated holes, during the pouring process, due to the small cross-sectional size, it is easy to form iron-enclosed sand under the wrapping of high-temperature molten iron, which is difficult to clean and leads to the scrapping of castings. Figure 2 Point C in (a) shows that a certain type of cylinder head has a φ20×160 elongated hole on the water jacket, which is difficult to clean and the scrap rate of the blank reaches more than 70%; Figure 2The cylinder head water jacket of a certain type shown in (b) has a small cross-section. During the early production trial process, due to the iron-encased sand defect, the scrap rate of the blank reached more than 80%.
[0008] 3. In order to ensure the quality of castings, according to the process requirements, it is necessary to set an internal chiller inside the casting. Since the chiller is in direct contact with the molten iron, the casting and the chiller will be sintered together, which cannot be cleaned and will cause the casting to be scrapped. Figure 3 The diagram at E in the middle shows the placement of the chiller for a certain type of cylinder head.
[0009] 4. According to the structural characteristics and process requirements of the casting, the inner cavity of the mud core needs to be partially made of Hafu core. During the pouring process, the surface of the Hafu core is easy to penetrate into the molten iron, making it difficult to clean or even impossible to clean, resulting in the scrapping of the casting. Figure 4 (a) and (b) are both pictures of a single mud core, where F and G are both the Hafu split core locations, and (c) is a simplified diagram of the inner cavity mud core assembly, where H is a schematic diagram of the Hafu split core after assembly.
[0010] Therefore, it is necessary to propose improvements to the above-mentioned core mud problem in the casting process. Summary of the invention
[0011] The technical problem solved by the present invention is: to provide a method for forming complex thin-walled castings and repairing mud cores. The purpose of the present invention is to design a simple and easy-to-operate casting forming or mud core repairing method to solve the problems that the mud core cannot be repaired during the production process, and the iron-coated sand and cold iron stick together during the cleaning process, thereby improving the casting production qualification rate, improving production efficiency, reducing production costs and saving resources.
[0012] In order to achieve the above object, the technical solution adopted by the present invention is:
[0013] The molding of complex thin-walled castings and the repair method of the core include the following steps:
[0014] Step 1): Select the high temperature resistant fiber belt material according to the pouring temperature, and determine the size of the high temperature resistant fiber belt according to the part to be formed or repaired;
[0015] Step 2) Use a high temperature resistant fiber belt to repair the part that needs to be formed or the part of the mud core that needs to be repaired by winding it.
[0016] In the above step 1), the width and thickness of the high temperature resistant fiber belt are determined according to the part to be formed or the part of the clay core to be repaired, and the thickness of the high temperature resistant fiber belt is selected to be 0.1 mm.
[0017] In the above step 2), when repairing cracks or breaks in small cross-sections on the clay core, wrap the cracked part with a high-temperature resistant fiber tape, then ignite and dry it, wrap the defective part inside the high-temperature resistant fiber tape, and the molten iron cannot penetrate into the crack during the pouring process.
[0018] In the above step 2), for the parts with small cross-sections and elongated holes on the casting core, the parts prone to defects are pre-wrapped tightly with high-temperature resistant fiber belts before entering the next process to avoid iron-encased sand defects.
[0019] In the above step 2), for castings using Harv core, the fine joint surfaces are wrapped with high temperature resistant fiber tapes in advance during the box matching process to prevent the infiltration of molten iron and eliminate skin seam defects.
[0020] In the above step 2), for castings using chilled iron at hot spots, high temperature resistant fiber tape is used to wrap the chilled iron to prevent contact between molten iron and the chilled iron during the pouring process, thereby preventing adhesion between the chilled iron and the casting.
[0021] The advantages of the present invention compared with the prior art are:
[0022] 1. This solution uses high temperature resistant fiber belts to solve the quality of mud cores and castings. According to the structure of mud cores or castings, fiber belts are used to wrap and wrap parts prone to quality problems in advance during the production process, which improves the yield rate of castings and mud cores. At the same time, direct contact with molten iron is effectively prevented during the pouring process, solving the defects of molten iron penetrating into the mud core to form iron-encased sand defects, the formation of skin seams on the core separation surface after the hafu core separation, and the adhesion of molten iron to cold iron. The scrap rate of mud cores is fundamentally reduced, and the production efficiency and the yield rate of castings are improved;
[0023] 2. For the production of complex castings, this solution solves the difficulties in repairing the core, eliminates the defects of iron-coated sand and skin seams, and avoids the adhesion of cold iron to the casting without affecting the quality and size of the casting. Its significance is not only reflected in improving economic benefits, but also in promoting the factory's diesel engine manufacturing technology, especially the casting technology level, to a new level through production and research. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Figure 1 (a) and (b) are drawings of a certain type of cylinder head inner cavity core with a small cross section in the prior art;
[0025] Figure 2 (a) is a diagram of a cylinder head core with an elongated hole in the prior art, and (b) is a diagram of a cylinder head core with a small cross section in the prior art;
[0026] Figure 3 This is a diagram showing the placement of a certain type of cylinder head cold iron in the prior art;
[0027] Figure 4 (a) and (b) are both diagrams of a single clay core with a Haver core in the prior art, and (c) is a simplified assembly diagram of an inner cavity clay core with a Haver core in the prior art;
[0028] Figure 5 The following is a simplified diagram of the cylinder head in the embodiment of the present invention, wherein (a) is the appearance of the cylinder head, (b) is the assembly diagram of the inner cavity of the cylinder head, and (c) is the internal structure of the cylinder head. Figure 1 , (d) is the internal structure of the cylinder head Figure 2 ;
[0029] Figure 6 1 is a structural diagram of a cylinder head in an embodiment of the present invention, wherein (a) is a lower water jacket, (b) is an upper water jacket, (c) is an assembly diagram of upper and lower water jackets, (d) is a cover plate core, and (e) is a casting diagram. DETAILED DESCRIPTION
[0030] 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.
[0031] See also Figure 1-6 , details of the embodiments of the present invention.
[0032] This embodiment further illustrates the technical solution of the present invention in combination with a certain type of cylinder head in production (hereinafter referred to as W cylinder head):
[0033] Product structure characteristics and difficulties analysis
[0034] The W diesel engine cylinder head has an external dimension of 700×536×543mm, with cooling water chamber, air inlet, exhaust and through screw holes arranged inside. The main wall thickness is 12mm, the net weight is 690Kg, and the gross weight is 900Kg. Figure 5 The following is a simplified diagram of the cylinder head, where (a) is the cylinder head appearance, (b) is the cylinder head inner cavity core assembly diagram, and (c) is the cylinder head internal structure. Figure 1 , (d) is the internal structure of the cylinder head Figure 2 .
[0035] According to the structure of the W cylinder head, it has the following characteristics during the production process:
[0036] 1) The core of the water jacket of the W cylinder head is relatively thick as a whole, with an average wall thickness of up to 100mm, but the local cross-section is small, with a size of about φ10, making production and operation difficult.
[0037] 2) The cooling water cavity of this type of cylinder head is an integral whole in the height direction. The sand core of the water cavity must be made of Harv core. During the casting process, molten iron can easily penetrate into the joint surface to form cracks, which are difficult to clean.
[0038] 3) The hot section of the spring seat is large, and the riser cannot be used for shrinkage compensation. A chiller needs to be installed at the hot section. However, the contact area between the chiller and the molten iron is large. After pouring, the chiller is easily sintered with the casting, making it difficult to clean.
[0039] like Figure 6 The figure shows the cylinder head structure diagram, (a) is the lower water jacket, (b) is the upper water jacket, (c) is the upper and lower water jacket assembly diagram, (d) is the cover plate core, and (e) is the casting diagram.
[0040] Analysis of the difficulties in producing the cylinder head
[0041] The scrap rate of W-type cylinder heads has been relatively high since 2006, accounting for about 50% of the production volume. The main reasons for the high scrap rate of W-type cylinder heads are:
[0042] 1) During the casting process of the cylinder head, cracks or fractures occur at the small cross-section of the lower water jacket core, and the gas in the core is discharged into the cavity, causing boiling in the riser, resulting in the scrapping of the blank.
[0043] 2) During the casting process of the cylinder head, the core mud is wrapped in high-temperature molten iron, and the small cross-section of the lower water jacket is prone to iron-encased sand, which cannot be cleaned and causes the cylinder head to be scrapped.
[0044] 3) According to the process requirements, a chill needs to be placed in the cover plate core. Due to the large contact area between the chill and the molten iron, fusion is easily produced, resulting in the inability to remove the chill normally during the cleaning process, resulting in waste loss.
[0045] 4) The inner cavity structure of the W-type cylinder head is complex, and the upper and lower water chambers are connected in many places, so the Harv core must be adopted. However, there are four small cross-sectional areas in the connecting parts. During the pouring process, the molten iron can easily penetrate and form seams, making it difficult to clean.
[0046] A systematic analysis of the problems in the production process combined with the actual situation shows that:
[0047] 1) The overall size of the W-type cylinder head is large, and the inner cavity structure is complex. The inner cavity is composed of 12 clay cores. The internal wall thickness is formed by the inner cavity clay cores. Therefore, the quality of the inner cavity clay cores determines the quality of the casting.
[0048] 2) The overall size of the water cavity mud core is large, but there are small cross-sections in some parts. During the core making process, the small cross-sections are very easy to break, and the amount of mud core scrapped is large, resulting in a huge waste of raw materials and labor.
[0049] 3) The cooling water chamber is a whole in the height direction, and Harv core must be used. The small joint surface is easy to penetrate into the molten iron to form cracks, which are difficult to clean.
[0050] 4) The W-type cylinder head is large in size, heavy in weight, and has many local heat nodes. Chilled iron is used for cooling in the areas where the riser cannot be compensated for shrinkage, but the chilled iron is easy to adhere to the body, making it difficult to clean.
[0051] For the production of W-type cylinder heads, the conventional method currently used is: for clay cores with slight cracks, the cracks are repaired with repair paste before use; for clay cores with small connecting parts or slender holes, more paint is applied to the parts prone to iron-coated sand to solve the problem; for the Hafu core parts, paint is used to seal the problem. Although there has been some improvement through production practice, the problem cannot be fundamentally solved and the scrap rate remains high.
[0052] In order to solve the core defect problem existing in the W-type cylinder head casting production, this embodiment provides a method for molding a complex thin-walled casting and repairing the core, which specifically includes the following steps:
[0053] Step 1): Select the high temperature resistant fiber belt material according to the pouring temperature, and determine the size of the high temperature resistant fiber belt according to the molding part or the mud core repair part; for the mud core repair part, the dimensional accuracy is high, and the general thickness is selected as 0.1mm.
[0054] Step 2) Use high temperature resistant fiber belt to repair the molding part or the part of the clay core that needs to be repaired by winding. During the core making process, for the clay core with cracks, use 0.1mm thick and 20mm wide fiber belt.
[0055] When repairing cracks or breaks in small cross-sections of the clay core, wrap the cracked area with a high-temperature resistant fiber tape and then ignite and dry it. Due to its thin thickness, it will not affect the final size. After wrapping the fiber tape, the strength of the clay core is increased, and the defective area is wrapped inside the high-temperature resistant fiber tape. During the pouring process, molten iron cannot penetrate into the cracks.
[0056] In the above step 2), for the parts with small cross-sections and elongated holes on the casting core, the parts prone to defects are pre-wrapped tightly with high-temperature resistant fiber belts before entering the next process to avoid iron-encased sand defects.
[0057] In the above step 2), for castings using Hafu core, the fine joint surfaces are wrapped with high temperature resistant fiber tape in advance during the box matching process to effectively prevent the infiltration of molten iron and completely eliminate the skin seam defects.
[0058] In the above step 2), for castings using chilled iron at hot spots, high temperature resistant fiber tape is used to wrap the chilled iron to prevent contact between molten iron and the chilled iron during the pouring process, thereby preventing the chilled iron from sticking to the casting.
[0059] The application of this embodiment on the W cylinder head has been successful, solving the problem that the broken core cannot be repaired, solving the problem that the fine parts of the core are easy to form iron-encased sand defects during the casting process, solving the problem that the skin seams formed on the core surface after the Hafu core is split are difficult to clean, solving the problem of adhesion between molten iron and cold iron, and improving the quality and yield rate of the cylinder head. It is mainly manifested in the following aspects:
[0060] 1) In the core making process, the problem of the core being unable to be repaired after being broken is solved, and the core yield rate is greatly improved from 50% to about 98%.
[0061] 2) The problem of iron-coated sand being formed after sintering of the molding sand in the casting process due to the slender holes and small cross-sections is solved, which reduces the scrap rate and improves production efficiency.
[0062] 3) Since the fiber tape is wrapped in advance at the small Hafu core section, the molten iron cannot pass through the fiber tape during the pouring process to form skin seam defects, and the problem of difficult cleaning is solved.
[0063] 4) The chiller with a large contact area with the molten iron is wound in advance, which effectively prevents the molten iron from contacting the chiller, thereby solving the defect of chiller adhesion.
[0064] 5) The qualified rate of W cylinder head blanks has increased from about 50% to about 90% at present, which has created favorable conditions for the company's mass production, greatly reduced costs and improved market competitiveness.
[0065] The method solves the problems of broken mud cores that cannot be repaired, thin-walled mud cores that cannot be cleaned, and castings that are scrapped due to the inability to clean slender holes. It solves the problem of complex thin-walled mud cores that are scrapped due to broken or cracked mud cores, while preventing the risk of molten iron infiltrating into the mud cores and causing castings to be scrapped. It also solves the problems of mud cores that cannot be cleaned due to sintering and cold iron adhesion, thereby improving the qualified rate of castings and production efficiency, reducing production costs and saving resources.
[0066] 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.
[0067] 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. The method for molding complex thin-walled castings and repairing mud cores is characterized by: The following steps are involved: Step 1): Select the high temperature resistant fiber belt material according to the pouring temperature, and determine the size of the high temperature resistant fiber belt according to the molding part or the repair part; Step 2) Use a high temperature resistant fiber belt to repair the part to be formed or repaired by winding it.
2. The method for forming a complex thin-walled casting and repairing a core according to claim 1, characterized in that: In the above step 1), the width and thickness of the high temperature resistant fiber belt are determined according to the part to be formed or repaired, and the thickness of the high temperature resistant fiber belt is selected to be 0.1 mm.
3. The method for forming a complex thin-walled casting and repairing a core according to claim 1, characterized in that: In the above step 2), when repairing cracks or breaks in small cross-sections on the clay core, wrap the cracked part with a high-temperature resistant fiber tape, then ignite and dry it, wrap the defective part inside the high-temperature resistant fiber tape, and the molten iron cannot penetrate into the crack during the pouring process.
4. The method for forming a complex thin-walled casting and repairing a core according to claim 1, characterized in that: In the above step 2), for the parts with small cross-sections and elongated holes on the casting core, the parts prone to defects are pre-wrapped tightly with high-temperature resistant fiber belts before entering the next process to avoid iron-encased sand defects.
5. The method for forming a complex thin-walled casting and repairing a core according to claim 1, characterized in that: In the above step 2), for castings using Harv core, the fine joint surfaces are wrapped with high temperature resistant fiber tapes in advance during the box matching process to prevent the infiltration of molten iron and eliminate skin seam defects.
6. The method for forming a complex thin-walled casting and repairing a core according to claim 1, characterized in that: In the above step 2), for castings using chilled iron at hot spots, high temperature resistant fiber tape is used to wrap the chilled iron to prevent contact between molten iron and the chilled iron during the pouring process, thereby preventing adhesion between the chilled iron and the casting.