Diesel engine cylinder block bolt hole core forming method

Abstract

According to the diesel engine cylinder block bolt hole core forming method, the bolt hole core manufacturing technology is optimized, so that the bolt hole core molding sand density is increased, the sand mold strength is guaranteed, the problem that the surface quality of a casting is affected due to unsmooth exhaust of a traditional bolt hole core is solved, follow-up cleaning is convenient, and the production efficiency is improved. The sand burning problem of the diesel engine cylinder block bolt hole is effectively solved, the surface smoothness of a casting is good, manual cleaning due to the sand burning problem is not needed, the production cleaning efficiency is improved, the casting quality is ensured, a coating in the bolt hole is easy to shell after shakeout, a bolt is through after shot blasting, the sand burning condition of the bolt hole is greatly improved, and the process guarantee is improved through superposition of multiple schemes; the defects such as sand sticking and air holes of bolt holes are thoroughly overcome, and the surface quality and cleaning efficiency of castings are improved.

Description

Technical Field

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

[0002] As one of the key components of diesel engines, the cylinder block of a large diesel engine must have high quality and high precision. Figure 5-6 The diesel engine cylinder block shown has a gross weight of 34.5t, a main wall thickness of 60-80mm, and a size of approximately 4100mm×2065mm×2170mm. 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 is at an angle of 7° to the lower plane 4 and 30° to the upper plane 2, respectively, and is a slender hole. This diesel engine cylinder block blank is cast by 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 split, and one side of the mold is divided into four movable blocks 6, which are pounded and 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 coated with three coats of composite alcohol-based paint according to the process regulations, and the Baume degrees are 50-60, 60-70, and 40-50 respectively.

[0003] When cleaning the casting, it was found that the bolt hole was seriously sanded and often in a state of tight sand adhesion. It could not be removed manually and the inclined surface could not be cleaned. In addition, there were small pores next to the bolt hole 3 on the lower plane 4, which affected the surface quality of the casting. In order to ensure the smoothness of the casting, the most common method is to use an oxygen melting rod to quickly melt the sand layer in the bolt hole at a high temperature of 3600℃. However, whether it is melted from the upper or lower plane, the end face hole diameter is too small, which often melts the casting body, and the two inclined surfaces cannot be melted and cut. It can only be cleaned slowly by manual labor, which takes a long time and often affects the delivery progress. Therefore, it is necessary to make improvements to the above problems. Summary of the invention

[0004] The technical problem solved by the present invention is as follows: a method for forming a bolt hole core of a diesel engine cylinder block is provided. The method increases the density of the bolt hole core sand by optimizing the preparation process of the bolt hole core, ensures the strength of the sand mold, solves the problem of poor exhaust of the traditional bolt hole core affecting the surface quality of the casting, facilitates subsequent cleaning, effectively solves the problem of sand sticking to the bolt hole of the diesel engine cylinder block, and provides a good surface finish of the casting, without the 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 of a diesel engine cylinder block, comprising the following steps:

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

[0007] 2) Core bone: A circular tubular structure is arranged at the core of the bolt hole and is used for exhausting the bolt hole core. A lifting ring with an upper end not higher than the upper core head is welded on the top surface of the core bone. A plurality of through holes are evenly distributed from bottom to top on the outer circumferential wall of the core bone, and steel nails for hanging sand are inserted in the through holes;

[0008] 3) Exhaust gas from the bolt hole core: Wrap the upper port on the outer wall of the core bone to the metal spiral tube at the upper end of the bolt hole core, and use the steel nail inserted in the through hole to prevent the metal spiral tube from falling off and positioning;

[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 and compacted layer by layer using a vibration motor to vibrate the molding sand;

[0010] 5) Die removal and placement: The bolt hole core is removed from the die and left to stand 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 1600°C to apply paint on the outer wall of the bolt hole core multiple times;

[0012] 7) Use of fiber tape: Before assembly, a fiber tape that can withstand high temperatures of 1700°C is wound around the overheated filling 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 40-70 mesh fine sand.

[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, firstly, movable block 1 with a lower core head is installed at the lower end of the mold, and the lower port is blocked by the lower core head, and then molding sand is driven between the outer periphery of the core bone and the mold, and the molding sand at the position of movable block 1 is manually compacted using a slender wooden stick; then, movable block 2 in contact with the upper edge of movable block 1 is installed at the outer periphery of the core bone, and then the vibration motor is fixed on movable block 2, and molding sand is driven into the outer periphery of the core bone, and the molding sand at the position of movable block 2 is manually compacted using a slender wooden stick. The vibrating motor is then used to vibrate and compact the molding sand; then, a movable block three in contact with the upper edge of the movable block two is loaded outside the core frame, and molding sand is driven into the periphery of the core frame. The molding sand at the position of the movable block three is manually compacted using a slender wooden stick, and the vibration motor is started to vibrate and compact the molding sand; finally, a movable block four in contact with the upper edge of the movable block three and with an upper core head at the upper end is loaded outside the core frame, and molding sand is driven into the periphery of the core frame. The molding sand at the position of the movable block four is manually compacted using a slender wooden stick, and the vibration motor is started 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 no 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 painted with a paint with a Baume degree of 30 to 50, so that the paint can fully penetrate into the surface of the bolt hole core, and the paint needs to be repeatedly painted until the paint is saturated to fill the gaps between the sand particles; the second to fifth coats are painted with a paint with a Baume degree of 50 to 60 to increase the coating thickness and improve the anti-sand adhesion ability of the bolt hole core; the sixth coat is painted with a paint with a Baume degree of 30 to 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 casting from generating pores, 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 in the through holes. On the one hand, the steel nails play a 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, and by providing a lifting ring at the upper end of the core bone, it is convenient for demoulding, lifting and core lowering 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, avoid molten iron from penetrating into the gap between sand particles to form sticky sand, and use mixed sand;

[0024] 4. This technical solution increases the density of the bolt hole core sand by optimizing the preparation process of the bolt hole core, ensures the strength of the sand mold, solves the problem of poor exhaust of the traditional bolt hole core affecting the surface quality of the casting, facilitates subsequent cleaning, and effectively solves the problem of sand sticking in the bolt hole of the diesel engine cylinder block. The casting has a good surface finish and does not require manual cleaning due to sand sticking problems, thereby improving production cleaning efficiency and ensuring casting quality. 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 being arranged on the core bone;

[0027] Figure 3 This is a schematic diagram of the electric compaction 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 It is a schematic diagram of the three-dimensional structure of the exhaust side of the cylinder block casting;

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

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

[0032] The following will be combined with the embodiments of the present invention Figure 1-4 7. The technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field without creative work based on the embodiments of the present invention are 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", "inside", "outside", etc., indicating positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", etc., are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0034] In this document, the terms "comprises", "comprising" or any other variation thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further limitations. The elements defined by the sentence "comprising a ..." do not exclude the presence of other identical elements in the process, method, article or device comprising the elements.

[0035] A method for forming a core of a bolt hole of 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. The mixed sand molding sand of this ratio has high strength, high air permeability and low gas emission. The sand particles of raw sand and regenerated sand are 40-70 mesh fine sand, which can increase the air permeability of the bolt hole core, effectively reduce the gap between sand particles, and prevent molten iron from penetrating into the gap between sand particles to form sticky sand;

[0037] 2) Core bone: such as Figure 1 As shown, a core bone 8 with a circular tubular structure and used for exhausting the bolt hole core 7 is arranged at the center of the bolt hole core 7, a lifting ring 9 with an upper end not higher than the upper core head 10 is welded on 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; 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; wherein the core bone 8 is a seamless steel tube; the provision of the through hole 11, on the one hand, is conducive to exhausting the bolt hole core 7 and eliminating the generation of pores, and on the other hand, is used for inserting steel nails, so that the steel nails play a role of hanging sand and improve the rigidity of the bolt hole core; and by providing the lifting ring 9 at the upper end of the core bone 8, it is convenient for demoulding, lifting and core lowering operations;

[0038] 3) Venting at the bolt hole: Figure 2As shown, three metal spiral tubes 12 with upper ports connected to the upper end of the bolt hole core 7 are wound on the outer wall of the core bone 8, and the metal spiral tubes 12 are prevented from falling off and positioned by steel nails inserted in the through holes 11; the core bone 8 with the metal spiral tubes 12 wound on the outer circumferential wall is arranged at the center of the bolt hole core 7, which is conducive to gas discharge, prevents the casting from generating pores, 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 components are installed layer by layer. The molding sand is manually compacted layer by layer using a slender wooden stick and the vibrating motor 13 is used to vibrate 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 make the bolt hole core 7 tight in place;

[0040] The movable block assembly includes movable block 1 6, movable block 2 15, movable block 3 16 and movable block 4 17 which are distributed from bottom to top. During molding, firstly, movable block 1 6 with lower core head 18 is installed at the lower end of mold 19, and the lower port is blocked by lower core head 18, and then molding sand is driven into the space between the periphery of core bone 8 and mold 19, and the molding sand at the position of movable block 1 6 is manually compacted by using slender wooden stick; then, movable block 2 15 which contacts with the upper edge of movable block 1 6 is installed into the periphery of core bone 8, and then vibration motor 13 is installed and fixed on movable block 2 15, and molding sand is driven into the periphery of core bone 8, and the molding sand at the position of movable block 2 15 is manually compacted by using slender wooden stick, and then the movable block 2 15 is manually compacted by using slender wooden stick. The molding sand is vibrated and compacted by a vibration motor 13; then, a movable block 3 16 in contact with the upper edge of the movable block 2 15 is loaded outside the core skeleton 8, and molding sand is driven into the periphery of the core skeleton 8. The molding sand at the position of the movable block 3 16 is manually compacted using a slender wooden stick, and the vibration motor 13 is started to vibrate and compact the molding sand; finally, a movable block 4 17 in contact with the upper edge of the movable block 3 16 and with an upper core head 10 at the upper end is loaded outside the core skeleton 8, and molding sand is driven into the periphery of the core skeleton 8. The molding sand at the position of the movable block 4 17 is manually compacted using a slender wooden stick, and the vibration motor 13 is started 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 compact and in place, reduces the gap 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 placed to allow the bolt hole core to fully harden, a slender bolt hole core 7 is formed; the bolt hole core 7 is placed for no less than 24 hours after demolding, and the placement time is checked and confirmed before painting. The painting can only be done after the time period exceeds 24 hours, at which time the bolt hole core is not easy to crack;

[0043] 6) Paint painting: Use paint for cast steel with a refractoriness of 1600°C to paint the outer wall of the bolt hole core 7 for multiple times; specifically, 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 30-50, so that the paint can fully penetrate into the surface of the bolt hole core 7, and the paint needs to be repeatedly painted until the paint is saturated to fill the gaps between the sand particles; the second to fifth times are painted with a paint with a Baume degree of 50-60, 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 30-50 to ensure 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 the box is assembled, a fiber tape 14 that can withstand a high temperature of 1700°C is wound at the filling overheating position at the minimum cross-section of the lower part of the bolt hole core 7, and the number of winding layers is not less than three and the thickness is not less than 0.5mm. After winding, its dimensional tolerance 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 sand of the bolt hole core 7, ensure the strength of the sand mold, solve the problem of poor exhaust of the traditional bolt hole core 7 affecting the surface quality of the casting, facilitate subsequent cleaning, and effectively solve the problem of sand sticking in the bolt hole of the diesel engine cylinder block. The casting has a good surface finish and does not require manual cleaning due to sand sticking, which improves production cleaning efficiency and ensures the quality of the casting. After the sand falls off, the coating inside the bolt hole is easy to peel off, and the bolt is penetrated after shot peening, which greatly improves the situation of sand sticking in the bolt hole. The superposition of multiple solutions improves the process assurance, completely solves the defects of sand sticking and pores in the bolt hole, and improves the surface quality and cleaning efficiency of the casting.

[0046] 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.

[0047] 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 may also be appropriately combined to form other implementation modes 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 raw 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 arranged at the center of the bolt hole core (7), a lifting ring (9) whose upper end is not higher than the upper core head (10) is welded on 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) Exhausting gas from the bolt hole core: winding the upper port on the outer wall of the core bone (8) to the metal spiral tube (12) at the upper end of the bolt hole core (7), and using a steel nail inserted in the through hole (11) to prevent the metal spiral tube (12) from falling off and positioning; 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, and 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) Coating: coating the outer wall of the bolt hole core (7) with a coating having a refractoriness of 1600° C. for cast steel for multiple times; 7) Use of fiber tape: Before assembly, 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 bolt hole of a diesel engine cylinder block according to claim 1, characterized in that: 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 40-70 mesh fine sand.

3. The method for forming a core of a bolt hole of a diesel engine cylinder block according to claim 1, characterized in that: 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 (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 of a diesel engine cylinder block according to claim 1, characterized in that: 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, characterized in that: 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) which are distributed from bottom to top. During molding, the movable block 1 (6) with the lower core head (18) is first installed at the lower end of the mold (19), and the lower end is blocked by the lower core head (18). Then, molding sand is driven into the space between the outer periphery of the core bone (8) and the mold (19), and the molding sand at the position of the movable block 1 (6) is manually compacted using a slender wooden stick; then, the movable block 2 (15) in contact with the upper edge of the movable block 1 (6) is installed into the outer periphery of the core bone (8), and the vibration motor (13) is fixedly mounted on the movable block 2 (15), and molding sand is driven into the outer periphery of the core bone (8). The molding sand at the position of the movable block 2 (15) is manually compacted using a slender wooden stick. The sand is manually compacted, and then the vibrating motor (13) is used to vibrate and compact the molding sand; then, a movable block (16) in contact with the upper edge of the movable block (15) is loaded outside the core frame (8), and then the molding sand is driven into the outer periphery of the core frame (8), and the molding sand at the position of the movable block (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, a movable block (17) in contact with the upper edge of the movable block (16) and having an upper core head (10) at the upper end is loaded outside the core frame (8), and then the molding sand is driven into the outer periphery of the core frame (8), and the molding sand at the position of the movable block (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, characterized in that: 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, characterized in that: 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 can fully penetrate into the surface of the bolt hole core (7), and the paint needs to be repeatedly painted until the paint is saturated to achieve the effect of filling 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, characterized in that: In the above step 7), the fiber tape is a high-silica glass fiber tape for casting.

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