CN109332604B - Method for solving shrinkage porosity of cylindrical nodular iron casting - Google Patents
Method for solving shrinkage porosity of cylindrical nodular iron casting Download PDFInfo
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- CN109332604B CN109332604B CN201811300616.5A CN201811300616A CN109332604B CN 109332604 B CN109332604 B CN 109332604B CN 201811300616 A CN201811300616 A CN 201811300616A CN 109332604 B CN109332604 B CN 109332604B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C9/00—Moulds or cores; Moulding processes
- B22C9/22—Moulds for peculiarly-shaped castings
- B22C9/24—Moulds for peculiarly-shaped castings for hollow articles
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C9/00—Moulds or cores; Moulding processes
- B22C9/08—Features with respect to supply of molten metal, e.g. ingates, circular gates, skim gates
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Abstract
A method for solving shrinkage porosity of cylindrical nodular iron castings belongs to the technical field of castings and is used for solving the defects of shrinkage porosity and the like of the nodular iron castings. The arrangement of a pouring system in a pouring mode is realized by arranging the cross gate at the thin wall part in the middle of the cylindrical nodular iron casting, namely the cross gate is positioned in the middle of the whole cylindrical nodular iron casting, and meanwhile, the cross gate has feeding effect on the thick wall at the lower part, so that the sequential solidification of the whole cylindrical nodular iron casting from bottom to top is realized.
Description
Technical Field
The invention relates to a casting process, in particular to a casting process of a nodular iron casting.
Background
The traditional production of thick and large nodular iron castings adopts a die and a special tool, the rigidity of the special tool and a casting mold can enable graphitization expansion to realize self feeding, and the shrinkage porosity problem in the casting solidification process can be solved by adopting the modes of chilling, riser feeding and sequential solidification and the like.
When the nodular iron castings with cylindrical structures with large wall thickness difference are produced in a core cladding dry sand burying box bare casting mode, the casting process is designed with the following difficulties:
(1) the sand consumption of the conventional core package is 50 mm-100 mm, the sand consumption of the thickness is relative to the sand consumption of a dry sand buried box for bare casting, the casting mould rigidity required by the graphitization expansion of the nodular cast iron in the solidification process cannot be met, and the graphitization expansion self-feeding of the nodular cast iron cannot be realized;
(2) when the problem of sequential solidification of the nodular iron castings with thick ends and thin walls in the middle of the nodular iron castings is solved by adopting a chilling mode, the quantity and the size of chills required to be adopted are large, chills are required to be arranged on the inner wall and the outer wall of the cylinder, and then a mode of riser feeding is combined, the sequential solidification method of chilling the chills and the riser feeding is complex in process and high in production cost; meanwhile, when 3D printing core making is adopted, the chill is inconvenient to fix when placed, and the outer ring of the casting belongs to a non-processing surface, so that a large amount of chills are added, and the appearance quality is poor;
(3) the problem of sequential solidification of the traditional nodular iron castings with cylindrical structures and obvious thick large thermal junctions at two ends is difficult to solve by adopting a bottom casting process design mode, and the yield of the castings is low.
Disclosure of Invention
In view of the above-mentioned shortcomings that the shrinkage porosity problem of the cylindrical nodular iron castings is difficult to solve, it is necessary to provide a method for solving the shrinkage porosity problem of the cylindrical nodular iron castings, wherein the method adopts a slip casting system to realize sequential solidification from bottom to top and avoid the shrinkage porosity.
A method for solving shrinkage porosity of a cylindrical nodular iron casting is characterized in that an annular patch type cross runner is arranged at the middle thin wall of the cylindrical nodular iron casting, the upper end face of the cross runner does not exceed the joint or transition between the thin wall and the upper thick wall, and the distance from the cross runner to a cavity of the cylindrical nodular iron casting is 30-50 mm; the ingate is arranged at the bottom of the horizontal pouring channel, namely the central axis of the ingate is arranged in the middle of the thin-wall area, or the distance between the ingate and the transition or connection position of the thin wall and the thick wall at the lower part is 20-40 mm. The patch type cross pouring gate can increase the temperature of the temperature field of the middle thin-wall part, simultaneously reduce heat dissipation and play a role in overheating the middle thin-wall part, thereby balancing the temperature difference of the temperature field of the middle thin-wall part and the temperature field of the areas where the upper thick wall and the lower thick wall are located; meanwhile, the annular patch type cross pouring gate arranged above the lower thick wall plays a role of arranging a riser above the lower thick wall, so that smooth transition between a heat node of the lower thick wall and patch of the middle part is realized, and sequential solidification of the lower thick wall and the middle thin wall from bottom to top is realized; in the same way, the sequential solidification from bottom to top of the middle thin wall and the upper thick wall is realized, and the sequential solidification from bottom to top of the whole cylindrical casting is also realized.
As the further optimization of the technical scheme, the patching type cross gate is set to be of a narrow and high structure, so that the slag blocking effect of the cross gate is further improved.
As a further optimization of the technical solution, a protrusion may be further provided on the upper end surface of the patch-type runner, and the protrusion may be provided in the middle of the upper end surface of the annular patch-type runner, that is, the distance between the protrusion and the inlet of the runner is equal to the distance between the protrusion and the end of the runner, or the difference between the distance between the protrusion and the inlet of the runner and the distance between the protrusion and the end of the runner is not greater than 100 mm. The overall height of the cross gate can be reduced by arranging the bulges, so that molten metal is saved, and meanwhile, the effect of setting a patch type cross gate can be achieved.
As a further optimization of this embodiment, when the lower thick wall is abruptly thickened, chill may be provided on the inner wall of the abruptly thickened portion of the lower wall of the cylindrical spheroidal graphite cast iron in order to ensure that the lower molten metal is first solidified to ensure a dense structure and that shrinkage porosity or shrinkage cavity defects do not occur.
As a further optimization of the technical scheme, when the density requirement of the casting on the metal meets the defect-free requirement of ultrasonic detection, chilling blocks can be uniformly distributed on the inner wall of the lower thick wall so as to further reduce the temperature of the lower thick wall part, so that the temperature field of the lower part is lower than that of the middle part, and the chilling effect of solidification at first is realized.
As a further optimization of the technical solution, in order to avoid the top end face of the upper thick wall from being defective, the temperature field of the upper thick wall may be shifted upwards, that is, a feeding head larger than the upper thick wall thermal node is arranged above the upper thick wall, so that the possible defects such as surface slag, surface pores, shrinkage porosity, graphite floating and the like are transferred into the feeding head, and the specific modulus ratio of the feeding head to the upper thick wall is MCap with heating means：MUpper thick wall＝1.1～1.2。
The technical scheme of the invention has the beneficial effects that: by adopting an injection type annular patch pouring system, a method that a chill is arranged in a hot spot area at the bottom of a casting and a shrinkage-compensating riser is arranged at a hot spot part at the top, sequential solidification of the cylindrical nodular cast iron is realized, so that the largest hot spot part at the top is solidified at last, and possible shrinkage porosity is moved into the shrinkage-compensating riser, thereby realizing shrinkage-free casting of the cylindrical nodular cast iron.
Drawings
FIG. 1 is a three-dimensional schematic view of a typical cylindrical structure ductile iron casting;
FIG. 2 is a three-dimensional schematic diagram of a pour-in-place gating system arrangement;
FIG. 3 is a schematic cross-sectional view of a pour-in-place gating system;
FIG. 4 is a schematic bottom view of a pour-in-place gating system arrangement;
in the drawings, 1-casting; 101-upper thick wall; 102-thin middle wall; 103-lower thick wall; 2-straight pouring channel; 3-a horizontal pouring channel; 301-a bump; 4-inner pouring channel; 5-feeding a shrink head; 6-chilling block.
Detailed Description
In order to more clearly illustrate the technical solution of the present invention, the detailed description will be given according to the embodiments of the drawings, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.
As shown in fig. 1, a high-grade cylindrical ductile iron casting has a typical cylindrical structure and a large wall thickness difference, and is embodied in a manner that a middle wall is thin and two ends are thick; in terms of quality, ultrasonic flaw detection is required to have no internal tissue defects and no leakage in a hydrostatic test. Namely, the cylindrical ductile iron casting 1 is divided into three sections, namely an upper thick wall 101, a middle thin wall 102 and a lower thick wall 103.
The technical scheme includes that the cylindrical ductile iron casting 1 is cast, specifically, an injection type patching pouring system is arranged on the periphery of a middle thin wall 102 of the cylindrical ductile iron casting 1, the pouring system comprises a sprue 2, a cross runner 3 and an inner runner 4, the cross runner 3 is arranged on the middle thin wall 102, the upper end face of the cross runner 3 is flush with the joint or transition of an upper thick wall 101 and a middle thin wall 102, the inner runner 4 is arranged at the bottom of the cross runner 3, and the central axis of the inner runner 4 is arranged in the middle lower region of the middle thin wall 102. The arrangement of a pouring system in a pouring mode is realized by arranging the cross gate 3 at the middle thin wall 102 of the cylindrical nodular iron casting 1, namely the cross gate is positioned in the middle of the whole cylindrical nodular iron casting 1, and meanwhile, the cross gate 3 has a feeding effect on the lower thick wall 103, so that the sequential solidification of the whole cylindrical nodular iron casting 1 from bottom to top is realized.
Preferably, in order to further improve the feeding effect on the lower thick wall 103, the distance between the central axis of the ingate 4 and the transition position of the lower thick wall 103 and the middle thin wall 102 is 20 mm-40 mm, so that the thin wall transition region between the overheated middle thin wall 102 and the lower thick wall 103 is realized, the temperature field is equalized, and the heat node effect of the lower thick wall 103 is avoided being increased or increased.
Preferably, in order to ensure that the temperature of molten metal entering the cavity of the cylindrical ductile iron casting 1 is not reduced too much and the hot pouring is performed at the middle thin-wall part, the cross runner 3 is arranged at a position close to the cavity, that is, the distance between the cross runner and the cavity is 30mm to 50mm, that is, the length of the ingate 4 is 30mm to 50 mm.
As a further improvement of this embodiment, in order to achieve the attaching effect of the runner 3 and to reduce the amount of the molten metal consumed by the runner 3, the runner 3 is formed to be narrow and tall, and for example, the aspect ratio of the cross section of the runner 3 may be 2 to 3: 1.
as a further improvement of this embodiment, in order to improve the patching effect of the runner 3, a protrusion 301 may be provided on the upper end surface of the runner 3, and the protrusion 301 may be provided at an intermediate position of the runner 3, that is, a distance difference between the protrusion 301 and the inlet and the end of the runner 3 is not more than 100 mm. By providing the projections 301 in the runner 3, the aspect ratio of the cross section of the runner 3 can be reduced, thereby further saving molten metal, that is, reducing the cross section of the runner 3.
As a further improvement of this embodiment, when there is a sudden or abrupt increase in the thickness of the lower thick wall 103 of the cylindrical ductile iron casting 1, in order to ensure that the molten metal in the thickened portion solidifies first, a chill 6 may be provided on the inner wall of the thickened portion, so as to accelerate the cooling of the molten metal in the cavity in the thick-walled portion and ensure the sequential solidification of the molten metal in the entire cavity from bottom to top.
As a further improvement of this embodiment, in order to ensure that the product can meet the defect of no tissue compactness during ultrasonic detection, chills 6 may be uniformly distributed on the inner wall of the cavity at the position of the lower thick wall 103, so as to improve the tissue compactness of the lower thick wall 103.
AsIn a further improvement of this embodiment, when the thickness of the upper thick wall 101 is relatively large, in order to ensure that the upper end surface or the upper end portion of the upper thick wall 101 does not have defects such as surface slag, surface pores or shrinkage porosity, the feeding head 5 may be further disposed on the upper thick wall 101, and the feeding head 5 may move the temperature field of the molten metal in the cavity upward, that is, the final solidification surface of the molten metal upward to the feeding head 5, so as to move the defects such as surface slag, surface pores, shrinkage porosity and graphite floating, which may be generated, upward to the feeding head 5. In order to realize the upward movement of the temperature field of the metal liquid in the cavity, the modulus ratio of the feeding head 5 to the upper thick wall 101 is MCap with heating means：MUpper thick wall＝1.1～1.2。
The above embodiments are only two typical cases of the present invention, and do not limit the technical solution of the present invention, and the reasonable inference and extension obtained according to the technical solution of the present invention without invasive labor are all within the scope of the technical solution of the present invention.
Claims (7)
1. A method for solving shrinkage porosity of a cylindrical nodular iron casting is characterized in that an annular patch type cross runner is arranged at the position of a middle thin wall of the cylindrical nodular iron casting, the upper end face of the cross runner does not exceed the joint or transition position of the thin wall and an upper thick wall, and a bulge is further arranged on the cross runner; the inner pouring gate is arranged at the bottom of the horizontal pouring gate, and the central axis of the inner pouring gate is arranged in the middle of the thin-wall area; arranging a chill on the inner wall of the part with the sharply changed wall thickness at the lower part of the cylindrical nodular cast iron; and a feeding head is arranged above the upper thick wall.
2. The method for solving the shrinkage porosity of the cylindrical ductile iron casting as claimed in claim 1, wherein the distance from the ingate to the transition or connection between the thin wall and the lower thick wall is 20mm to 40 mm.
3. The method for solving the shrinkage porosity of the cylindrical ductile iron casting according to claim 1, wherein the distance between the cross runner and the cavity of the cylindrical ductile iron casting is 30mm to 50 mm.
4. The method for solving the shrinkage porosity of cylindrical ductile iron castings according to any one of claims 1 to 3, characterized in that said cross runners are provided with a narrow and tall structure.
5. The method for solving the shrinkage porosity of the cylindrical ductile iron casting according to claim 1, wherein the protrusion is provided in the middle of the upper end surface of the ring-shaped patch type runner.
6. The method for solving the shrinkage porosity of cylindrical ductile iron castings according to claim 1, wherein the difference between the distance of said protrusion from the inlet of said runner and the distance from the end of said runner is not more than 100 mm.
7. The method for solving the shrinkage porosity of cylindrical ductile iron casting according to claim 1, wherein said method comprises the step of forming a cylindrical ductile iron casting by using a mold, and said method comprises the step of forming a cylindrical ductile iron casting by using a mold
The modulus ratio of the feeding head to the upper thick wall is 1.1-1.2.
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| CN113102690A (en) * | 2021-04-06 | 2021-07-13 | 洛阳乾中新材料科技有限公司 | Design method of casting mold |
| CN114653924B (en) * | 2022-03-16 | 2023-08-29 | 南京工业大学 | Low-pressure casting pouring system of feeding path of complex thin-wall part |
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| CN108326242A (en) * | 2018-03-01 | 2018-07-27 | 四川共享铸造有限公司 | The casting casting mold and casting method of twi-tier blade impeller |
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| CN201455180U (en) * | 2009-06-23 | 2010-05-12 | 河南省西峡汽车水泵股份有限公司 | Ductile iron non-riser casting die |
| CN101618425B (en) * | 2009-07-25 | 2011-07-13 | 日月重工股份有限公司 | Method for casting rotary axis casts of aerogenerators |
| CN102430714A (en) * | 2011-11-30 | 2012-05-02 | 天津一机机械有限公司 | Process for casting thick and large nodular cast iron valve plate |
| CN203459669U (en) * | 2013-07-31 | 2014-03-05 | 四川省祥业机械铸造有限公司 | Central air conditioner shell non-riser casting structure |
| CN204018646U (en) * | 2014-07-11 | 2014-12-17 | 合肥江淮铸造有限责任公司 | A kind of vermicular cast iron brake drum running gate system |
| CN204724802U (en) * | 2015-06-30 | 2015-10-28 | 四川德恩精工科技股份有限公司 | Based on the belt pulley blank casting mould of symmetric form ingate |
| CN105728661A (en) * | 2016-03-09 | 2016-07-06 | 南京晨光艺术工程有限公司 | Bronze bell casting process |
| CN205851844U (en) * | 2016-07-30 | 2017-01-04 | 临沂天阔铸造有限公司 | A kind of edge iron casting mould |
| CN107774909A (en) * | 2016-08-25 | 2018-03-09 | 青岛润成车辆配件有限公司 | A kind of filter for casting |
| CN106513586B (en) * | 2016-11-22 | 2018-06-08 | 鞍钢铸钢有限公司 | A kind of casting method of In Mine Crusher upper frame |
| CN107812891B (en) * | 2017-12-06 | 2019-08-02 | 四川共享铸造有限公司 | A kind of circular ring structure part running gate system |
| CN108500212A (en) * | 2018-05-28 | 2018-09-07 | 康诺精工有限公司 | A kind of water cooling turbine case and its casting technique |
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