Diesel engine cylinder block bolt hole core forming method

Abstract

Provided is a diesel engine cylinder block bolt hole core forming method. By optimizing the preparation process of the bolt hole core, the density of the bolt hole core molding sand is increased, the strength of the sand mold is guaranteed, and the problem of poor exhaust of the traditional bolt hole core affecting the surface quality of the casting is solved. Subsequent cleaning is convenient, and the problem of sand sticking to the bolt hole of the diesel engine cylinder block is effectively solved. The casting surface finish is good, and manual cleaning due to the sand sticking problem is unnecessary, thereby improving the production cleaning efficiency and ensuring the casting quality. After the sand is removed, the coating inside the bolt hole is easy to shell, and the bolt is penetrated after shot peening, which greatly improves the sand sticking problem of the bolt hole. The superposition of multiple solutions improves the process assurance, completely solves the defects such as sand sticking and air holes in the bolt hole, and improves the casting surface quality and cleaning efficiency.

Description

Technical Field

[0001] The invention belongs to the technical field of diesel engine cylinder block casting, and particularly relates to a method for forming a bolt hole core of a diesel engine cylinder block. Background Art

[0002] As one of the key components of diesel engines, large diesel engine cylinder blocks must have high quality and high precision. Figure 5-6 The diesel engine cylinder block shown has a gross weight of 34.5 t, a main wall thickness of 60 to 80 mm, and dimensions of approximately 4100 mm × 2065 mm × 2170 mm. The exhaust side 1 and the intake side 5 of the diesel engine cylinder block each have three bolt holes 3 penetrating the upper plane 4 and the lower plane 2, as shown in FIG. Figure 7 As shown, the bolt hole 3 is more than two meters high, with a minimum cross-section of φ104, and the middle part forms an angle of 7° with the lower plane 4 and a 30° angle with the upper plane 2, respectively. It is a slender hole. This diesel engine cylinder block blank is cast using self-hardening furan resin sand. The bolt hole 3 is a bolt hole core (sand core), and the sand filling direction is vertically downward; the mold is a split type, and one side of the mold is divided into four movable blocks 6. Sand is pounded layer by layer and the movable blocks are installed layer by layer to ensure that each bolt hole core 7 can be filled with sand tightly in place. After demolding and core repairing, it is painted three times with composite alcohol-based paint in accordance with process regulations, with Baume degrees of 50-60, 60-70, and 40-50 respectively.

[0003] During casting cleaning, it was discovered that the bolt hole was severely sand-bound and often tightly adhered, making it impossible to remove manually and the bevel surface could not be cleaned. In addition, small air holes existed near the bolt hole 3 on the lower plane 4, affecting the surface quality of the casting. To ensure the smoothness of the casting, an oxygen melt rod was most commonly used to quickly melt the sand layer in the bolt hole at a high temperature of 3600°C. However, whether melting from the upper or lower plane, the end face diameter was too small, often damaging the casting body. Moreover, the two bevel surfaces could not be melted, and cleaning could only be done slowly and manually, which was time-consuming and often affected the delivery schedule. Therefore, it was necessary to improve the above-mentioned problems. Summary of the Invention

[0004] The technical problem solved by the present invention is to provide a method for forming the bolt hole core of a diesel engine cylinder block. By optimizing the preparation process of the bolt hole core, the density of the bolt hole core molding sand is increased, the strength of the sand mold is ensured, and the problem of poor exhaust of the traditional bolt hole core affecting the surface quality of the casting is solved. The subsequent cleaning is convenient, and the problem of sand sticking to the bolt hole of the diesel engine cylinder block is effectively solved. The surface finish of the casting is good, and there is no need for manual cleaning due to the sand sticking problem, thereby improving the production cleaning efficiency and ensuring the quality of the casting.

[0005] The technical solution adopted by the present invention is a method for forming a core of a bolt hole in a diesel engine cylinder block, comprising the following steps:

[0006] 1) Molding sand: Molding sand is formed by mixing original sand and regenerated sand;

[0007] 2) Core: A circular tubular structure is set at the core of the bolt hole and is used to exhaust the bolt hole core. The top surface of the core is welded with a lifting ring with the upper end not higher than the upper core head. A number of through holes are evenly distributed from bottom to top on the outer circumference of the core, and steel nails are inserted into the through holes to hang sand.

[0008] 3) Bolt hole core gas outlet: A metal spiral tube with an upper end connected to the upper end of the bolt hole core is wound around the outer wall of the core bone, and the metal spiral tube is prevented from falling off and positioned by a steel nail inserted into the through hole;

[0009] 4) Molding: The outer wall of the core bone is driven into the molding sand layer by layer from bottom to top and the movable block components are installed layer by layer. The molding sand is manually compacted layer by layer using a slender wooden stick and vibrated by a vibration motor layer by layer;

[0010] 5) Demolding and placing: The bolt hole core is demoulded and placed to allow the bolt hole core to fully harden, forming a slender bolt hole core;

[0011] 6) Paint application: Use paint for cast steel with a refractoriness of up to 1600°C to apply paint multiple times on the outer wall of the bolt hole core;

[0012] 7) Use of fiber tape: Before assembling the box, a fiber tape that can withstand high temperatures of 1700°C should be wound around the filling overheating position at the minimum cross-section of the lower part of the bolt hole core. The number of winding layers should be no less than three and the thickness should be no less than 0.5mm. After winding, the dimensional tolerance should meet the design dimensional requirements of the bolt hole core.

[0013] In the above step 1), the ratio of the original sand to the regenerated sand is 3:7, and the sand particles of the original sand and the regenerated sand are fine sand of 40-70 mesh.

[0014] In the above step 2), the sum of the length of the steel nail and the radius of the outer wall of the core bar is smaller than the radius of the minimum position of the bolt hole core.

[0015] In the above step 2), the core steel is a seamless steel pipe.

[0016] In the above step 4), the movable block assembly includes movable block 1, movable block 2, movable block 3 and movable block 4 distributed from bottom to top. During molding, first install movable block 1 with a lower core head at the lower end of the mold, and use the lower core head to seal the lower end. Then, inject molding sand between the outer periphery of the core bone and the mold, and manually compact the molding sand at the position of movable block 1 using a slender wooden stick; then, install movable block 2 at the outer periphery of the core bone, which contacts the upper edge of movable block 1, and then install and fix the vibration motor on movable block 2. In addition, inject molding sand into the outer periphery of the core bone, and manually compact the molding sand at the position of movable block 2 using a slender wooden stick. Then use the vibration motor to vibrate and compact the molding sand; then load the movable block three that contacts the upper edge of the movable block two outside the core bone, and then drive the molding sand to the periphery of the core bone, use a slender wooden stick to manually compact the molding sand at the position of the movable block three, and then start the vibration motor to vibrate and compact the molding sand; finally, load the movable block four that contacts the upper edge of the movable block three and has an upper core head at the upper end outside the core bone, and then drive the molding sand to the periphery of the core bone, use a slender wooden stick to manually compact the molding sand at the position of the movable block four, and then start the vibration motor to vibrate and compact the molding sand, so that the molding sand is driven in layer by layer and compacted.

[0017] In the above step 5), the bolt hole core is left to stand for not less than 24 hours after demoulding.

[0018] In the above step 6), the outer wall of the bolt hole core is painted six times in total; the first coat is applied with a paint having a Baume degree of 30-50 to allow the paint to fully penetrate the surface of the bolt hole core, and the paint needs to be repeatedly applied until the paint is saturated with the paint to fill the gaps between the sand particles; the second to fifth coats are applied with a paint having a Baume degree of 50-60 to increase the coating thickness and improve the bolt hole core's anti-sand adhesion ability; the sixth coat is applied with a paint having a Baume degree of 30-50 to ensure the surface smoothness and coating strength of the bolt hole core.

[0019] In the above step 7), the fiber tape is a high-silica glass fiber tape for casting.

[0020] The advantages of the present invention compared with the prior art are:

[0021] 1. This technical solution sets a core bone with a metal spiral tube wrapped around the outer circumferential wall at the core of the bolt hole, which is conducive to gas release, prevents the formation of pores in the casting, and improves the production quality of the casting;

[0022] 2. This technical solution provides a plurality of through holes on the outer circumferential wall of the core bone and inserts steel nails into the through holes. On the one hand, the steel nails play the role of hanging sand and improving the rigidity of the bolt hole core. On the other hand, the provision of the through holes is conducive to the exhaust of the bolt hole core. In addition, by providing a lifting ring at the upper end of the core bone, it is convenient for demoulding, lifting and core removal operations.

[0023] 3. This technical solution uses 40-70 mesh molding sand mixed with original sand and regenerated sand, which can increase the air permeability of the bolt hole core, effectively reduce the gap between sand particles, and avoid the penetration of molten iron into the gap between sand particles to form sticky sand.

[0024] 4. This technical solution optimizes the preparation process of the bolt hole core to increase the density of the bolt hole core sand, ensure the strength of the sand mold, and solve the problem of poor exhaust of the traditional bolt hole core affecting the surface quality of the casting. It is convenient for subsequent cleaning and effectively solves the problem of sand sticking in the bolt hole of the diesel engine cylinder block. The casting surface finish is good, and there is no need for manual cleaning due to sand sticking problems, which improves production cleaning efficiency and ensures the quality of the casting. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic diagram of the core bone structure of the present invention;

[0026] Figure 2 This is a schematic diagram of the structure of the metal spiral tube of the present invention arranged on the core bone;

[0027] Figure 3 This is a schematic diagram of the electric compacting structure of the movable block of the present invention;

[0028] Figure 4 This is a schematic diagram of the fiber tape winding position of the present invention;

[0029] Figure 5 This is a schematic diagram of the three-dimensional structure of the exhaust side of the cylinder block casting;

[0030] Figure 6 This is a schematic diagram of the three-dimensional structure of the intake side of the cylinder block casting;

[0031] Figure 7 This is the bolt hole core process diagram of the present invention. DETAILED DESCRIPTION

[0032] The following is a combination of the embodiments of the present invention Figure 1-4 7. The technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort shall fall within the scope of protection of the present invention.

[0033] It should be noted that, in this document, unless otherwise stated, it should be understood that the terms "center," "upper," "lower," "front," "back," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like indicate positions or relationships based on those shown in the accompanying drawings. These are intended only to facilitate the description of the present invention and simplify the description, and are not intended to indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limiting the present invention. Furthermore, the terms "first," "second," "third," and the like are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0034] As used herein, the terms "comprises," "comprising," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, the phrase "comprising a..." does not preclude the presence of additional identical elements in the process, method, article, or apparatus that includes the elements.

[0035] A method for forming a core of a bolt hole in a diesel engine cylinder block comprises the following steps:

[0036] 1) Molding sand: Molding sand is formed by mixing raw sand and regenerated sand. Specifically, the ratio of raw sand to regenerated sand is 3:7. This ratio of mixed sand has high strength, high air permeability, and low gas emission. The raw sand and regenerated sand are made of 40-70 mesh fine sand, which can increase the air permeability of the bolt hole core and effectively reduce the gaps between the sand grains, preventing molten iron from seeping into the gaps between the sand grains and forming sticky sand.

[0037] 2) Core bone: such as Figure 1 As shown, a core bone 8 with a circular tubular structure is provided at the center of the bolt hole core 7 and is used for venting the bolt hole core 7. A lifting ring 9 with an upper end not higher than the upper core head 10 is welded to the top surface of the core bone 8. A plurality of through holes 11 are evenly distributed from bottom to top on the outer circumferential wall of the core bone 8, and steel nails for hanging sand are inserted into the through holes 11. Specifically, the sum of the length of the steel nail and the radius of the outer wall of the core bone 8 is less than the radius of the minimum position of the bolt hole core 7. The core bone 8 is a seamless steel tube. The provision of the through holes 11, on the one hand, is conducive to venting the bolt hole core 7 and eliminating the generation of air holes. On the other hand, it is used for inserting steel nails, so that the steel nails play the role of hanging sand, thereby improving the rigidity of the bolt hole core. Moreover, by providing a lifting ring 9 at the upper end of the core bone 8, it is convenient for demoulding, lifting and core lowering operations.

[0038] 3) Bolt hole core gas outlet: Figure 2As shown, three metal spiral tubes 12 with upper ends extending to the upper ends of the bolt hole core 7 are wound around the outer wall of the core bar 8, and the metal spiral tubes 12 are prevented from falling out and positioned by steel nails inserted into the through holes 11; the core bar 8 with the metal spiral tubes 12 wound around the outer circumferential wall is arranged at the center of the bolt hole core 7, which is conducive to gas release, prevents the formation of air holes in the casting, and improves the production quality of the casting;

[0039] 4) Modeling: Figure 3 、 Figure 7 As shown, the outer wall of the core bone 8 is driven into the molding sand layer by layer from bottom to top and the movable block assembly is installed layer by layer. The molding sand is manually compacted layer by layer using a slender wooden stick and the vibration motor 13 is used to vibrate and compact the molding sand layer by layer. The entire sand pounding process is manually compacted. The vibration motor 13 is installed on the mold body through the movable block 2 15. Every time the sand is pounded 1 / 4 of the height, the vibration motor is used to vibrate for 3-5 minutes to tighten the bolt hole core 7 into place.

[0040] The movable block assembly includes movable block 16, movable block 2 15, movable block 3 16 and movable block 4 17 distributed from bottom to top. During molding, first, movable block 16 with lower core head 18 is installed at the lower end of mold 19, and the lower end port is blocked by lower core head 18. Then, molding sand is poured between the outer periphery of core bone 8 and mold 19, and the molding sand at the position of movable block 16 is manually compacted by using a slender wooden stick; then, movable block 2 15 in contact with the upper edge of movable block 16 is installed at the outer periphery of core bone 8, and then the vibration motor 13 is fixed on movable block 2 15, and molding sand is poured into the outer periphery of core bone 8, and the molding sand at the position of movable block 2 15 is manually compacted by using a slender wooden stick, and then the molding sand is manually compacted by using a slender wooden stick. Use the vibration motor 13 to vibrate and compact the molding sand; then, load the movable block 3 16 in contact with the upper edge of the movable block 2 15 outside the core bone 8, and then drive the molding sand into the periphery of the core bone 8, use a slender wooden stick to manually compact the molding sand at the position of the movable block 3 16, and then start the vibration motor 13 to vibrate and compact the molding sand; finally, load the movable block 4 17 in contact with the upper edge of the movable block 3 16 and with the upper core head 10 at the upper end outside the core bone 8, and then drive the molding sand into the periphery of the core bone 8, use a slender wooden stick to manually compact the molding sand at the position of the movable block 4 17, and then start the vibration motor 13 to vibrate and compact the molding sand, so that the molding sand is driven in layer by layer and compacted.

[0041] The combination of the above two vibration modes makes the molding sand inside the bolt hole core 7 compacted and in place, reduces the gaps between the sand particles, improves the surface hardness of the bolt hole core 7, and effectively prevents sand from sticking;

[0042] 5) Demolding and placing: After the bolt hole core 7 is demolded and left to stand until the bolt hole core is fully hardened, a slender bolt hole core 7 is formed; the bolt hole core 7 is left to stand for not less than 24 hours after demolding. Check and confirm the placement time before painting. Paint can only be applied after the time period exceeds 24 hours. At this time, the bolt hole core is not easy to crack;

[0043] 6) Paint application: Paint for cast steel with a refractoriness of up to 1600°C is applied multiple times to the outer wall of the bolt hole core 7. Specifically, the outer wall of the bolt hole core 7 is painted six times. The first coat is applied with a paint having a Baume degree of 30-50, allowing the paint to fully penetrate the surface of the bolt hole core 7. The paint needs to be applied repeatedly until the paint is saturated and fills the gaps between the sand particles. The second to fifth coats are applied with a paint having a Baume degree of 50-60, increasing the coating thickness and improving the anti-sand adhesion capability of the bolt hole core 7. The sixth coat is applied with a paint having a Baume degree of 30-50, ensuring the surface finish and coating strength of the bolt hole core 7. The above-mentioned painting process can ensure the surface finish and coating strength of the bolt hole core, thereby improving the surface roughness of the casting.

[0044] 7) Use of fiber tape: Figure 4 As shown, before closing the box, a fiber tape 14 that can withstand high temperatures of 1700°C is wound around the filling overheating position at the minimum cross-section of the lower part of the bolt hole core 7. The number of winding layers is not less than three and the thickness is not less than 0.5 mm. After winding, the dimensional tolerance is such that it meets the design dimensional requirements of the bolt hole core 7. This process can effectively improve the anti-sand adhesion here. Specifically, the fiber tape is a high-silica glass fiber tape for casting.

[0045] This technical solution optimizes the preparation process of the bolt hole core 7 to increase the density of the molding sand of the bolt hole core 7, ensure the strength of the sand mold, and solve the problem of poor exhaust of the traditional bolt hole core 7 affecting the surface quality of the casting. It facilitates subsequent cleaning and effectively solves the problem of sand sticking to the bolt hole of the diesel engine cylinder block. The casting surface finish is good, and there is no need for manual cleaning due to sand sticking, which improves production cleaning efficiency and ensures the quality of the casting. After the sand falls out, the coating inside the bolt hole is easy to shell, and the bolt is penetrated after shot peening, which greatly improves the problem of sand sticking to the bolt hole. The superposition of multiple solutions improves process assurance, completely solves defects such as sand sticking and air holes in the bolt hole, and improves the surface quality of the casting and cleaning efficiency.

[0046] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be included therein. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

[0047] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method 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 methods that can be understood by those skilled in the art.

Claims

1. A method for forming a core of a bolt hole in a diesel engine cylinder block, characterized in that The following steps are involved: 1) Molding sand: Molding sand is formed by mixing original sand and regenerated sand; 2) Core bone: A core bone (8) having a circular tubular structure and used for exhausting the bolt hole core (7) is provided at the center of the bolt hole core (7), a lifting ring (9) having an upper end not higher than the upper core head (10) is welded to the top surface of the core bone (8), a plurality of through holes (11) are evenly distributed from bottom to top on the outer circumferential wall of the core bone (8), and steel nails for hanging sand are inserted in the through holes (11); 3) Bolt hole core gas outlet: a metal spiral tube (12) with an upper end connected to the upper end of the bolt hole core (7) is wound on the outer wall of the core bone (8), and the metal spiral tube (12) is prevented from falling off and positioned by a steel nail inserted into the through hole (11); 4) Molding: The outer wall of the core (8) is driven into the molding sand layer by layer from bottom to top and the movable block components are installed layer by layer. The molding sand is manually compacted layer by layer using a slender wooden stick and vibrated and compacted layer by layer using a vibration motor (13) to vibrate the molding sand; 5) Demolding and placing: the bolt hole core (7) is demolded and placed to allow the bolt hole core (7) to fully harden, thereby forming a slender bolt hole core (7); 6) Paint application: Use paint for cast steel with a refractoriness of up to 1600°C to apply paint to the outer wall of the bolt hole core (7) multiple times; 7) Use of fiber tape: Before closing the box, a fiber tape (14) that can withstand high temperatures of 1700°C is wound around the overheated position of the minimum cross-section at the bottom of the bolt hole core (7). The number of winding layers is not less than three and the thickness is not less than 0.5 mm. After winding, the dimensional tolerance of the fiber tape meets the design dimensional requirements of the bolt hole core (7).

2. The method for forming a core of a diesel engine cylinder block bolt hole according to claim 1, wherein: In the above step 1), the ratio of the original sand to the regenerated sand is 3:7, and the sand particles of the original sand and the regenerated sand are fine sand of 40-70 mesh.

3. The method for forming a core of a diesel engine cylinder block bolt hole according to claim 1, wherein: In the above step 2), the sum of the length of the steel nail and the outer wall radius of the core bone (8) is smaller than the radius of the minimum position of the bolt hole core (7).

4. The method for forming a core of a bolt hole in a diesel engine cylinder block according to claim 1, wherein: In the above step 2), the core steel (8) is a seamless steel pipe.

5. The method for forming a core of a bolt hole in a diesel engine cylinder block according to claim 1, wherein: In the above step 4), the movable block assembly includes movable block 1 (6), movable block 2 (15), movable block 3 (16) and movable block 4 (17) distributed from bottom to top. When molding, first install movable block 1 (6) with lower core head (18) at the lower end of mold (19), seal the lower end by lower core head (18), then inject molding sand between the outer periphery of core bone (8) and mold (19), and use slender wooden stick to manually compact the molding sand at the position of movable block 1 (6); then install movable block 2 (15) in contact with the upper edge of movable block 1 (6) at the outer periphery of core bone (8), and then install and fix the vibration motor (13) on movable block 2 (15), inject molding sand into the outer periphery of core bone (8), and use slender wooden stick to compact the molding sand at the position of movable block 2 (15). The sand is manually compacted, and then the vibrating motor (13) is used to vibrate and compact the molding sand; then, the movable block three (16) in contact with the upper edge of the movable block two (15) is loaded outside the core bone (8), and then the molding sand is driven into the outer periphery of the core bone (8). The molding sand at the position of the movable block three (16) is manually compacted using a slender wooden stick, and then the vibrating motor (13) is started to vibrate and compact the molding sand; finally, the movable block four (17) in contact with the upper edge of the movable block three (16) and with the upper core head (10) at the upper end is loaded outside the core bone (8), and then the molding sand is driven into the outer periphery of the core bone (8). The molding sand at the position of the movable block four (17) is manually compacted using a slender wooden stick, and then the vibrating motor (13) is started to vibrate and compact the molding sand, so that the molding sand is driven in layer by layer and compacted.

6. The method for forming a core of a bolt hole in a diesel engine cylinder block according to claim 1, wherein: In the above step 5), the bolt hole core (7) is left to stand for not less than 24 hours after demoulding.

7. The method for forming a core of a bolt hole in a diesel engine cylinder block according to claim 1, wherein: In the above step 6), the outer wall of the bolt hole core (7) is painted six times in total; the first time is painted with a paint with a Baume degree of 30 to 50, so that the paint fully penetrates into the surface of the bolt hole core (7), and the paint needs to be repeatedly painted until the paint is saturated and fills the gaps between the sand particles; the second to fifth times are painted with a paint with a Baume degree of 50 to 60, so as to increase the coating thickness and improve the anti-sand adhesion ability of the bolt hole core (7); the sixth time is painted with a paint with a Baume degree of 30 to 50, so as to ensure the surface smoothness and coating strength of the bolt hole core (7).

8. The method for forming a core of a bolt hole in a diesel engine cylinder block according to claim 1, wherein: In the above step 7), the fiber tape is a high-silica glass fiber tape for casting.

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