Large Propeller Middle Hole Core and Its Casting Fastening Tooling

Abstract

The present invention discloses a large propeller middle-hole core. On the outer peripheral surface of the central steel pipe, a riser section and a body section in the shape of a frustum of a cone are arranged adjacent to each other up and down. The riser section is filled with the first material sand. The body section includes an inner layer and an outer layer. The outer layer includes at least two segmented sections A arranged adjacent to each other vertically in sequence. Each segmented section A includes a plurality of strip-shaped chill blocks evenly distributed in the circumferential direction. There are gaps between the circumferentially adjacent strip-shaped chill blocks. The number and thickness of the strip-shaped chill blocks on each segmented section A are the same, and the gaps are equal. The inner layer and the gaps are filled with the second material sand. At the same time, a fastening tooling for casting a large propeller with this middle-hole core is also disclosed. By improving the structure and materials of the middle-hole core and improving the fastening tooling for the middle-hole core during the casting of the propeller, defects such as shrinkage porosity, shrinkage cavity, and gas porosity in the middle hole of the propeller casting are significantly reduced, and the phenomena of copper drilling and environmental humidity influence on the middle-hole core are significantly improved. The fastening tooling has universality, convenience, firmness, and safety.

Description

Technical Field

[0001] The present invention relates to the field of propeller casting, in particular to a middle hole core for large propeller casting and its casting fastening tooling. Background Art

[0002] Quality control of the casting middle hole is an important part of the propeller casting process. With the development of technology, the design of propellers is trending towards being larger and more complex, which undoubtedly brings unprecedented difficulties and challenges to the quality control of the propeller middle hole.

[0003] In the existing propeller casting process, all the middle hole cores of the propellers are made of sodium silicate sand. In order to increase the overall strength of the core, facilitate sand hanging and lifting, a steel pipe is vertically placed in the middle of the core, and some round steel bars are welded around the outer periphery of the steel pipe from top to bottom for reinforcement. The upper end of the steel pipe is directly welded to the crossbar to fasten and fix the core to the crossbar tooling.

[0004] This kind of core structure and its fixing method have the following problems:

[0005] 1. If the quality control of the casting middle hole is not good, it is very easy to appear casting defects such as shrinkage cavity and shrinkage porosity. Subsequent mechanical scribing adjustment is time-consuming and laborious. At the same time, in order to deal with the defects, rescue operations such as "welding repair - machining - welding repair" are also required, which greatly affects the processing efficiency and may even lead to the scrapping of the propeller in severe cases;

[0006] 2. Since the cores are all made of sodium silicate sand and have no chill effect, the area near the middle hole belongs to the casting hot spot circle area, and shrinkage cavity and shrinkage porosity defects are very likely to appear in the middle hole;

[0007] 3. During pouring, the core is very likely to have the phenomenon of copper penetration, that is, the molten copper is easy to enter the inside of the core. Once the molten copper enters the inside of the core, it may cause serious over-standard of the middle hole defects, out-of-roundness of the middle hole, eccentricity of the middle hole, etc., and may even lead to the scrapping of the propeller in severe cases;

[0008] 4. Affected by the material of the sodium silicate sand itself, the core is relatively sensitive to changes in environmental humidity. In humid weather, the surface of the core is prone to powdering, peeling, and loss of strength. In extreme cases, the core needs to be remade due to scrapping;

[0009] 5. Affected by the material of the sodium silicate sand itself, during the pouring process, when the middle hole is under high temperature for a long time, the gas inside the core will invade the molten copper, easily causing porosity defects;

[0010] 6. For large propellers, such cores are likely to cause poor feeding effect in the riser area, thus easily causing shrinkage cavity defect problems;

[0011] 7. The material properties of sodium silicate sand are different from those of steel pipes and round steel. Therefore, during the high-temperature and cooling processes of the core, the shrinkage characteristics of the two materials are different, resulting in a decrease in the strength of the middle-hole core and an increase in the probability of copper drilling, seriously affecting the quality of the middle hole. Summary of the Invention

[0012] Object of the Invention: Aiming at the above problems, one object of the present invention is to provide a middle-hole core for casting large propellers, and the second object is to provide a fastening tooling for this middle-hole core during propeller casting to improve the quality of the cast middle hole.

[0013] Technical Solution: A middle-hole core for a large propeller includes a central steel pipe, and a riser section and a body section in the shape of a frustum of a cone arranged adjacent to each other up and down on its outer peripheral surface. The two are adjacent to each other with their lower bottom surfaces having equal diameters. The riser section is filled with the first material sand. The body section includes an inner layer and an outer layer. The outer layer includes at least two segmented sections A arranged adjacent to each other vertically in sequence. Each segmented section A includes a plurality of strip-shaped chillers evenly distributed in the circumferential direction. There is a gap between adjacent strip-shaped chillers in the circumferential direction. The number and thickness of the strip-shaped chillers on each segmented section A are the same, and the gaps are equal. The inner layer and the gaps are filled with the second material sand.

[0014] Further, between the segmented sections A arranged adjacent to each other vertically in sequence, the strip-shaped chillers are vertically connected with matching steps, which not only ensures the dimensional accuracy of the end faces of the strip-shaped chillers of adjacent segmented sections A but also enhances the strength of the entire outer layer.

[0015] Further, on the outer wall surface of the central steel pipe in the riser section, there is a protruding first round steel; on the inner wall surface of the strip-shaped chiller, there is a protruding second round steel, and the second round steel is fixed to the central steel pipe in the body section. The second round steel connects and fixes the strip-shaped chiller in the outer layer of the body section to the central steel pipe. When filling the material sand, the first round steel and the second round steel strengthen the fastening and shaping effects on the material sand, improving the strength of the core.

[0016] Further, the number of strip-shaped chillers on each segmented section A is 8 - 12, and the strip-shaped chillers on each segmented section A are the same; the width of the gap is 20 mm.

[0017] Further, the material of the strip-shaped chiller is cast iron H200.

[0018] Further, when the height of the body section is less than 1300 mm, the outer layer includes two segmented sections A, and the heights of the segmented sections A are equal; when the height of the body section is not less than 1300 mm, the outer layer includes three segmented sections A, and the heights of the segmented sections A are equal.

[0019] Further, when the propeller diameter is not greater than 9 m, both the first material sand and the second material sand are sodium silicate sand; when the propeller diameter is greater than 9 m, the first material sand is composed of silica sand, ceramsite sand, foundry clay, and sodium silicate mixed in a mass ratio of 66:23:1.5:9.5. The particle size of the silica sand is 70 - 140 mesh, the particle size of the ceramsite sand is 50 - 100 mesh, the particle size of the foundry clay is 140 mesh, and the modulus of the sodium silicate is 2.0 and the Baume degree is 50°Bé. This can enhance the strength of the riser section core, improve the collapsibility and thermal stability of the core at high temperatures, reduce the gas evolution amount, and avoid the problem of copper drilling. The second material sand is sodium silicate sand.

[0020] Further, when the propeller diameter is greater than 9 m, in order to enhance the riser feeding effect and prevent shrinkage cavity and shrinkage porosity defects, the riser section includes frustum-shaped segment B and segment C arranged adjacent to each other up and down. The lower bottom surface of segment B is equal in diameter to the upper bottom surface of segment C and is adjacent. The height ratio of segment B to segment C is 4:1.

[0021] A fastening tooling for casting a large propeller with a middle-hole core as described above includes a crossbar, a locking plate, a positioning ring, a pressing plate, a sleeve, a tension bolt, and a positioning bolt. The pressing plate and the locking plate are arranged up and down. The sleeve is fixed on the lower surface of the pressing plate, the positioning ring is fixed on the upper surface of the locking plate, the tension bolt passes through the pressing plate and the locking plate. The lower end of the tension bolt is screwed to the locking plate, and the upper end abuts against the pressing plate. A crossbar is fixed at each end of the locking plate. The upper end of the central steel pipe of the middle-hole core sequentially passes through the locking plate, the positioning ring, and the sleeve upward until it abuts against the pressing plate. The positioning bolt passes through the circumference of the positioning ring to abut against the outer peripheral surface of the central steel pipe.

[0022] Further, a nut is sleeved on the upper end of the tension bolt, and the nut abuts against the pressing plate.

[0023] Beneficial effects: Compared with the prior art, the advantages of the present invention are as follows: By improving the structure and materials of the middle-hole core, and improving the fastening tooling for the middle-hole core during the casting of the propeller, defects such as shrinkage porosity, shrinkage cavity, and air holes in the middle hole of the propeller casting are significantly reduced. The phenomena of copper drilling and being affected by environmental humidity of the middle-hole core are significantly improved. The fastening tooling has versatility, convenience, firmness, and safety. While improving the positioning accuracy of the middle-hole core, it can meet the requirement of effectively releasing high-temperature stress. Description of the Drawings

[0024] Figure 1 It is one of the schematic diagrams of the middle-hole core structure of the present invention;

[0025] Figure 2 It is Figure 1 The schematic diagram of one of the segments A on the outer layer of the main body section in

[0026] Figure 3 This is the second schematic diagram of the structure of the middle-hole core in the present invention;

[0027] Figure 4 This is the schematic diagram of the fastening tooling structure for casting a large propeller with a middle-hole core;

[0028] Figure 5 is Figure 4 The top view of the connection structure of the middle crossbar, locking plate, positioning ring, and positioning bolt. Specific embodiments

[0029] The present invention will be further illustrated below in conjunction with the accompanying drawings and specific embodiments. These embodiments are only used to illustrate the present invention and not to limit the scope of the present invention.

[0030] A middle-hole core for a large propeller, as shown in the attached Figure 1 figure, includes a central steel pipe 1, and a riser section 2 and a body section 3 which are arranged adjacent to each other up and down on the outer peripheral surface of the central steel pipe 1. The central steel pipe 1 is a hollow seamless steel pipe. Both the riser section 2 and the body section 3 are frustum-shaped structures, and the diameters of their lower bottom surfaces are equal. The lower bottom surface of the riser section 2 faces downward and the upper bottom surface faces upward, while the lower bottom surface of the body section 3 faces upward and the upper bottom surface faces downward, and the two are adjacent to each other at the lower bottom surface.

[0031] In the central steel pipe 1 in the riser section 2, a protruding first round steel 21 is provided on its outer wall surface. The riser section is filled with a first material sand. When filling, the fastening and shaping effects on the material sand can be enhanced through the first round steel, thereby improving the core strength.

[0032] The body section 3 includes an inner layer 31 and an outer layer 32, and the outer layer 32 includes at least two adjacent segments A33 arranged vertically in sequence. Combining with the attached Figure 2As shown, for one of the segments A33, it includes a plurality of bar-shaped chills 34 made of cast iron H200, which are arranged vertically and evenly distributed in the circumferential direction, and there is a gap 35 with a width of 20 mm between adjacent bar-shaped chills 34. Then, each bar-shaped chill 34 has the same structure and size, and is a long strip structure of equal thickness. The inner and outer wall surfaces are both curved surfaces, and the curvature of the upper end is greater than that of the lower end. The curvature of the outer wall surface is the same as that of the outer circumferential surface of the body segment 3. A protruding second round steel 37 is provided on the inner wall surface of the bar-shaped chill 34, and the second round steel 37 is welded and fixed to the central steel pipe 1 in the body segment 3, so that the bar-shaped chill in the outer layer of the body segment is connected and fixed to the central steel pipe. For each segment A33, the number and thickness of the bar-shaped chill 34 are the same, and the gaps 35 are equal. Between the vertically adjacent segments A33, a matching step 36 structure is provided on the end surface of the strip-shaped chill 34 to form a vertical connection, thereby ensuring the dimensional accuracy of the end surface of the strip-shaped chill of the adjacent segments A and enhancing the strength of the entire outer layer. The inner layer 31 and the gap 35 are filled with the second material sand. During the filling, the second round steel can also play a role in strengthening the fastening and shaping of the material sand, thereby improving the strength of the mud core.

[0033] The strip-shaped chill replaces part of the material sand on the outer peripheral surface of the main body section, which can play a role of chilling when pouring molten copper, making the surface layer of the middle hole crystallized and dense, which is conducive to solving shrinkage cavities and shrinkage defects.

[0034] The gaps between adjacent strip chills allow the mud core to have a certain degree of yielding capacity under high temperature conditions, facilitate the subsequent cleaning of the strip chills, and ensure that the strip chills can be recycled multiple times.

[0035] The number of segments A33 on the outer layer 32 can be set to 2 to 3, depending on the total height of the main body segment 3: when the total height is less than 1300 mm, 2 segments A33 are set with equal heights; when the total height is ≥1300 mm, 3 segments A33 are set with equal heights.

[0036] The number of the strip cold irons 34 on the segment A33 can be set to 8 to 12, according to the diameter of the bottom surface of the main body segment 3: when the bottom surface diameter is ≤400mm, set 8; when 400<bottom surface diameter<600, set 10; when the bottom surface diameter is ≥600mm, set 12.

[0037] When the propeller diameter is ≤9m, the first material sand and the second material sand are both water glass sand.

[0038] When the propeller diameter is greater than 9m, the second material sand is sodium silicate sand, and the first material sand is special sand. The special sand is composed of silica sand, perlite sand, foundry clay, and sodium silicate mixed in a mass ratio of 66∶23∶1.5∶9.5. The particle size of the silica sand is 70 - 140 mesh, the particle size of the perlite sand is 50 - 100 mesh, the particle size of the foundry clay is 140 mesh, and the modulus of the sodium silicate is 2.0 and the Baume degree is 50°Bé. The preparation method of the special sand is: weigh each component according to the mass ratio, first pour all the silica sand, perlite sand, and foundry clay into a roller mixer, dry mix for 1 minute, then pour all the sodium silicate into the roller mixer, and then wet mix for 3 minutes, and the sand obtained after discharging is the special sand. The special sand can enhance the strength of the core in the riser section, improve the collapsibility and thermal stability of the core at high temperatures, reduce the gas evolution amount, and at the same time avoid the problem of copper drilling.

[0039] When the propeller diameter is greater than 9m, in order to enhance the feeding effect of the riser and prevent shrinkage cavity and porosity defects, as shown in the attached Figure 3 figure, the riser section 2 includes sub - sections B22 and C23 arranged adjacent to each other up and down. Both sub - sections B22 and C23 are frustum - shaped structures, and the height ratio is 4∶1. The diameter of the lower bottom surface of sub - section B22 is equal to the diameter of the upper bottom surface of sub - section C23. Both sub - sections B22 and C23 have the lower bottom surface facing down and the upper bottom surface facing up, and the lower bottom surface of sub - section B22 is adjacent to the upper bottom surface of sub - section C23.

[0040] The above - mentioned fastening tooling for casting large - scale propellers with a core having a central hole, as shown in the attached Figure 4 、 5 figure, includes a cross - bar 4, a locking plate 5, a positioning ring 6, a pressing plate 7, a sleeve 8, a tension bolt 9, and a positioning bolt 10.

[0041] Both the locking plate 5 and the pressing plate 7 are flat parts. The pressing plate 7 is above the locking plate 5. The upper end surface of the sleeve 8 is fixed to the lower surface of the pressing plate 7, and the lower end surface of the positioning ring 6 is fixed to the upper surface of the locking plate 5. The sleeve 8 and the positioning ring 6 are vertically opposite. The tension bolt 9 is located outside the positioning ring 6 and the sleeve 8 and passes through the pressing plate 7 and the locking plate 5. Its lower end is screwed to the locking plate 5, and a nut 91 is sleeved on the upper end, and the nut 91 abuts against the pressing plate 7. By rotating the nut 91, the relative distance between the pressing plate 7 and the locking plate 5 can be changed. A cross - bar 4 is fixed at each end of the locking plate 5. The central steel pipe 1 of the core with a central hole passes upward through the locking plate 5, the positioning ring 6, and the sleeve 8 in sequence until it abuts against the lower surface of the pressing plate 7. The pressing plate fixes the upper limit of the central steel pipe, realizing the fastening of the core with a central hole in the height direction. Four positioning bolts 10 are passed through the circumferential direction of the positioning ring 6 until they abut against the outer peripheral surface of the central steel pipe, performing circumferential fixation on the central steel pipe, realizing the position adjustment of the core with a central hole in the horizontal direction, and ensuring concentricity.

[0042] After the copper water is poured, at regular intervals, by adjusting the nut 91 to increase the relative distance between the pressure plate 7 and the locking plate 5, the dynamic free release of the vertical thermal expansion stress of the middle-hole core can be realized under high-temperature conditions.

[0043] While improving the positioning accuracy of the middle-hole core, this fastening tooling can meet the requirement of effectively releasing high-temperature stress, solve the problem of copper drilling in the middle hole, and improve the quality of the middle hole. This fastening tooling has the characteristics of universality, convenience, firmness, safety, etc., can be reused repeatedly and can improve production efficiency. For example, sleeves with different diameters can be fixed on the upper and lower surfaces of the pressure plate, and according to the diameter of the central steel pipe of the middle-hole core, a certain surface of the pressure plate can be selected to assemble and use the fastening tooling downward.

[0044] The middle-hole core and the fastening tooling of the present invention, after being actually applied and tested in the casting of large propellers, can achieve the following effects:

[0045] 1. The occurrence probability of shrinkage porosity and shrinkage cavity defects in the middle hole is reduced by at least 80%, greatly reducing the rework man-hours such as subsequent welding repair, and improving work efficiency.

[0046] 2. The occurrence probability of gas hole defects in the middle hole is reduced by at least 90%.

[0047] 3. The stress of the middle-hole core is effectively released, and the phenomenon of copper drilling is reduced by at least more than 95%.

[0048] 4. Effectively reduce the sensitivity of the middle-hole core to environmental humidity, and greatly reduce the problems of moisture absorption and powdering.

[0049] 5. The strip chill on the middle-hole core and the fastening tooling can be recycled, saving costs and reducing losses.

[0050] 6. The cost of production enterprises is reduced, and the efficiency can be increased by about 10%.

Claims

1. A large propeller middle-hole core, characterized in that: It includes a central steel pipe (1), and a frustum-shaped riser section (2) and a body section (3) arranged adjacent to each other vertically on its outer peripheral surface. The lower bottom surface of the riser section (2) is equal in diameter to and adjacent to the upper bottom surface of the body section (3). The riser section (2) is filled with a first material sand. The body section (3) includes an inner layer (31) and an outer layer (32). The outer layer (32) includes at least two segment A (33) arranged adjacent to each other vertically in sequence. Each segment A (33) includes a plurality of strip-shaped chill irons (34) evenly distributed in the circumferential direction. There is a gap (35) between the circumferentially adjacent strip-shaped chill irons (34). The number and thickness of the strip-shaped chill irons (34) on each segment A (33) are the same, and the gap (35) is equal. The inner layer (31) and the gap (35) are filled with a second material sand; in the central steel pipe (1) in the riser section (2), a protruding first round steel (21) is provided on its outer wall surface; a protruding second round steel (37) is provided on the inner wall surface of the strip-shaped chill iron (34), and the second round steel (37) is fixed to the central steel pipe (1) in the body section (3); when the diameter of the propeller is not greater than 9m, both the first material sand and the second material sand are sodium silicate sand; when the diameter of the propeller is greater than 9m, the first material sand is composed of silica sand, ceramsite sand, foundry clay, and sodium silicate mixed in a mass ratio of 66∶23∶1.5∶9.

5. The particle size of the silica sand is 70 - 140 mesh, the particle size of the ceramsite sand is 50 - 100 mesh, the particle size of the foundry clay is 140 mesh, the modulus of the sodium silicate is 2.0, and the Baume degree is 50°Bé. The second material sand is sodium silicate sand.

2. The large propeller middle-hole core according to claim 1, characterized in that: Between the segment A (33) arranged adjacent to each other vertically in sequence, the strip-shaped chill irons (34) are vertically connected with matching steps (36).

3. The large propeller middle-hole core according to claim 1, characterized in that: The number of the strip-shaped chill irons (34) on each segment A (33) is 8 - 12, and the strip-shaped chill irons (34) on each segment A (33) are the same; the width of the gap (35) is 20mm.

4. The large propeller middle-hole core according to claim 1, characterized in that: The material of the strip-shaped chill iron (34) is cast iron H200.

5. The large propeller middle-hole core according to claim 1, characterized in that: When the height of the body section (3) is less than 1300mm, the outer layer (32) includes two segment A (33), and the height of each segment A (33) is equal; when the height of the body section (3) is not less than 1300mm, the outer layer (32) includes three segment A (33), and the height of each segment A (33) is equal.

6. The large propeller middle-hole core according to any one of claims 1 - 5, characterized in that: When the propeller diameter is greater than 9 m, the riser section (2) includes frustum-shaped subsections B (22) and C (23) arranged adjacent to each other vertically. The lower bottom surface of subsection B (22) has the same diameter as and is adjacent to the upper bottom surface of subsection C (23), and the height ratio of subsection B (22) to subsection C (23) is 4:1.

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