CN109175307B - 3D printing sand mold antigravity casting forming method - Google Patents
3D printing sand mold antigravity casting forming method Download PDFInfo
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- CN109175307B CN109175307B CN201811320806.3A CN201811320806A CN109175307B CN 109175307 B CN109175307 B CN 109175307B CN 201811320806 A CN201811320806 A CN 201811320806A CN 109175307 B CN109175307 B CN 109175307B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D18/00—Pressure casting; Vacuum casting
- B22D18/04—Low pressure casting, i.e. making use of pressures up to a few bars to fill the mould
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B33—ADDITIVE MANUFACTURING TECHNOLOGY
- B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
- B33Y10/00—Processes of additive manufacturing
Abstract
A3D printing sand mould antigravity casting forming method is characterized in that a pouring system is designed according to casting characteristics; parting a casting of the designed pouring system by adopting three-dimensional drawing software, and arranging a sodium silicate sand molding and self-locking tool placing platform at the bottom end of the pouring cup; adding supports according to parting results, printing the supported sand mold blocks and cores by using precoated sand, and baking different sand mold blocks after printing; and manufacturing a pouring gate by adopting a wood pattern and sodium silicate sand, assembling the sand mold and the sodium silicate sand pouring gate, splicing the self-locking tool, and pouring the sand mold by adopting an antigravity low-pressure mode to obtain a casting. The invention solves the problem of sand mold box lifting caused by large antigravity pouring mold filling pressure, so that the 3D printing sand mold has no crack, delamination or even fracture, the size tolerance of the casting reaches the level of HB6103CT6, the weight and volume deviation of the casting is less than or equal to 5 percent, and the production cost of the casting is greatly lower.
Description
Technical Field
The invention relates to a 3D printing sand mold antigravity casting forming method, which adopts antigravity casting forming and is suitable for producing a 3D printing sand mold and an antigravity casting.
Background
With the rapid development of the aerospace industry, more and more large-scale complex thin-wall structure castings are used. The existing aerospace casting has the characteristics of large profile, complex structure, high mechanical property requirement, uneven thickness, complex design of bent pipe oil paths and the like. In the conventional casting method, the antigravity pouring has the characteristics of stable mold filling, easy feeding, compact structure and the like, and can fully meet the requirements of aerospace on the metallurgical quality and mechanical property of castings. Meanwhile, in order to meet the requirements of complex cavities and scientific research products with different appearance designs in recent years, a counter-gravity pouring mode is combined with a PCM (pulse code modulation) dieless casting mold manufacturing technology and an SLS (laser sintering) precoated sand technology, and the casting problem is well solved due to the characteristics of no need of molds, rapidness, flexibility, free manufacturing, stable casting quality and the like. And the method can also greatly improve the development efficiency of new products, has great advantages in cost and period saving, is suitable for the production requirement of personalized customized products, and can greatly reduce the decision risk of new product development.
3D prints sand mould and antigravity pouring in-process of combining together production, because the mould filling pressure and the 3D of antigravity pouring print the sand mould great, and consider 3D and print sand mould brush coating and conveniently get the needs of type and complicated die cavity of foundry goods itself and many oil circuit pipeline, can take multi-level typing, 3D prints the sand mould combination back through water glass molding, fill the type in-process at the pouring, lead to the sand mould easily to lift case or even sand mould fracture phenomenon and take place, make the foundry goods wall thickness increase, weight and volume deviation are big, size precision reduces. Secondly, the box lifting can also cause the feeding stability of the gating system to be poor, so that the casting has the defects of shrinkage porosity, shrinkage cavity and the like, and even the casting is directly scrapped. After the casting is divided, the quality requirements of each sand mold are different, for example, the pouring gate quality is almost not required, and the sand molds are produced in a 3D printing mode to be wasted. In order to promote the combination of the 3D printing sand mold and the antigravity pouring production mode, shorten the production period of military products, meet the production quality requirements of castings and save the production cost of the castings as far as possible, a reasonable method is urgently needed at the present stage.
Disclosure of Invention
In order to overcome the problems in the prior art, the invention aims to provide a 3D printing sand mold antigravity casting forming method, which improves the production efficiency of castings, reduces the production cost of the castings and is suitable for molding sodium silicate sand.
In order to achieve the purpose, the invention adopts the technical scheme that:
A3D printing sand mold antigravity casting forming method comprises the following steps:
step 1: designing a gating system according to the characteristics of the casting;
step 2: parting a casting of the designed pouring system by adopting three-dimensional drawing software, and arranging a sodium silicate sand molding and self-locking tool placing platform at the bottom end of the pouring cup;
and step 3: adding supports according to the parting result in the step 2 to facilitate parting;
and 4, step 4: adopting the precoated sand to print the sand mold blocks and cores added with supports in the step 3, and cleaning, baking and finishing different sand mold blocks after printing is finished;
and 5: manufacturing a self-locking tool matched with the self-locking tool placing platform;
step 6: manufacturing a pouring gate by adopting a wood pattern and sodium silicate sand, baking the sodium silicate sand at 450 ℃ for 6 hours, taking out the sodium silicate sand, and air cooling to manufacture a finished sodium silicate sand pouring gate;
and 7: assembling the sand mold prepared in the step 4 and the sodium silicate sand runner prepared in the step 6;
and 8: splicing the self-locking tool manufactured in the step 5 with the sand mold combined in the step 7;
and step 9: filling and compacting sodium silicate sand under the self-locking tool placement platform in the step 2 to form a sand mold;
step 10: and (5) pouring the sand mould in the step 9 in an anti-gravity low-pressure mode to obtain a casting.
The invention is further improved in that in the step 1, the length of a pouring cup of the pouring system is 100mm, and the distance from the edge of the sand mold to the pouring cup is not less than 180 mm.
The further improvement of the invention is that in the step 2, the height of the self-locking tool placing platform is 80 mm.
The further improvement of the invention is that in the step 4, the baking process comprises the following steps: baking the sand mold blocks with the height of more than 60mm and the length of more than 150mm at 220 ℃ for 8 hours, cooling the sand mold blocks with the furnace for 4 hours, opening the furnace and cooling the sand mold blocks with air; and (3) baking the core with the diameter of 8mm or 10mm at 200 ℃ for 4h, cooling the core with the furnace for 4 hours, opening the furnace and cooling the core with air.
The invention has the further improvement that in the step 5, the self-locking tool comprises two channel steels (3), two screws (4) are arranged between the two channel steels, the two screws (4) are arranged in parallel, and two ends of each screw (4) penetrate through the channel steels and are fixed.
The further improvement of the invention is that in the step 9, the filling height of the sodium silicate sand is 120mm in sections, the sodium silicate sand is compacted in sections, the next layer of the sodium silicate sand is filled after the upper layer is hardened, the sodium silicate sand molding is finished by analogy according to the size of the sand mold, and the top end of the sand mold is ensured to be filled with at least 150mm of the sodium silicate sand and hardened.
In a further improvement of the invention, in step 10, the casting temperature is: normal temperature, casting temperature: 730-740 ℃, liquid rising/filling speed: 50mm/s, solidification pressure difference: 30 KPa.
Compared with the prior art, the invention has the following beneficial effects:
according to the invention, the 3D printing sand molds are assembled into a whole similar to the mold shell through the self-locking device, so that the problem of lifting the mold shell during counter-gravity pouring after the sand molds are bonded is solved, the dimensional precision of the castings is improved, and the weight and volume deviation amplitude of the castings is reduced. When a casting is molded, the self-locking tool placing platform is arranged at the bottom end of the pouring gate, so that the sand mold is convenient to carry, the self-locking tool placing platform can be used as a water glass sand filling area, after the water glass sand is hardened, the friction force between the sand mold and the sand box is increased, and the sand mold is prevented from falling off in the process of carrying the sand box. The pouring gate is made of the wood pattern and the water glass sand, so that the production cost of the casting can be effectively saved. By adopting the method to fix the 3D printing sand mold, the sand mold is not lifted, the top end is not broken and eccentrically shaken due to large mold filling pressure, the stability of the pouring process is improved, and the stability of the metallurgical quality of the casting is improved. By adopting the method to fix the 3D printing sand mold, the problem of lifting the mold is not required to be considered during parting, the rationality of parting of complex castings can be increased, and the counter-gravity pouring mode and the 3D printing sand mold production mode are better combined. The invention solves the problem of sand mold box lifting caused by large antigravity pouring mold filling pressure, so that the 3D printing sand mold has no crack, delamination or even fracture, the size tolerance of the casting reaches the level of HB6103CT6, the weight and volume deviation of the casting is less than or equal to 5 percent, and the production cost of the casting is greatly lower. The invention provides a solid foundation for smooth production of castings by combining a 3D printing sand mold and a counter-gravity pouring mode.
Furthermore, the self-locking tool is simple to manufacture and can be repeatedly used.
Furthermore, the sectional sodium silicate sand is molded, tamped and hardened, so that the binding force between the 3D printing sand mold and the sand box is increased, the sand box is prevented from falling off in the carrying process, meanwhile, a large amount of sodium silicate sand is filled at the top end of the sand mold, the lifting and even breakage of the sand mold in the pouring process are reduced, the dimensional precision of the casting is improved, the weight and the volume deviation are reduced, particularly for a round casting, the pouring pressure borne by the upper end face is huge, and the dimensional precision and the circular concentricity of the casting can be improved to a great extent.
Drawings
FIG. 1 is a schematic view of a self-locking tool and a sodium silicate-bonded sand platform.
Fig. 2 is a schematic view of a self-locking tool.
FIG. 3 is a schematic view of a water glass sand runner.
FIG. 4 is a schematic view of the combination of a water glass sand runner, a sand mold and a self-locking tool.
In the figure, 1 is a self-locking tool position platform, 2 is a sand mold, 3 is a channel steel, 4 is a screw, 5 is a nut, 6 is a water glass sand runner and 7 is a self-locking tool.
Detailed Description
The present invention will now be described in further detail with reference to examples.
The invention comprises the following steps:
step 1: according to the characteristics of the casting, a pouring system is designed, and the length of the universal pouring cup and the area of the bottom end plane are properly increased. Wherein, the length of the pouring cup is increased to 100mm, and after the area of the bottom plane is increased, the distance from the edge of the sand mold to the pouring cup is not less than 180 mm;
step 2: a casting of a designed pouring system is divided into types by adopting three-dimensional drawing software, a sodium silicate sand molding (fixing) and self-locking tool placing platform 1 is arranged at the bottom end of a pouring cup, and the height of the platform is 80mm, as shown in figure 1.
And step 3: and (4) adding supports according to the parting result in the step (2) so as to facilitate parting.
And 4, step 4: and (3) adopting the precoated sand to print the sand mould blocks and cores added with the supports in the step 3, and cleaning, baking and fine finishing different sand mould blocks after printing is finished. Wherein, the baking process comprises the following steps: and (3) baking the sand mold blocks with the height of more than 60mm and the length of more than 150mm at 220 ℃ for 8 hours, cooling the sand mold blocks with the furnace for 4 hours, opening the furnace and cooling the sand mold blocks with air. And (3) baking the core with the diameter of 8mm or 10mm at 200 ℃ for 4h, cooling the core with the furnace for 4 hours, opening the furnace and cooling the core with air.
And 5: manufacturing a self-locking tool 7 according to the self-locking tool placing platform in the step 2; the self-locking tool 7 comprises two channel steels 3, two screws 4 are arranged between the two channel steels 3, the two screws 4 are arranged in parallel, and two ends of each screw 4 penetrate through the channel steels and are fixed through a gasket and a nut 5;
wherein the channel steel is 700mm long, and the position 40mm away from the edge of the channel steel is respectively drilled
Hole, screw
600mm in length, 8 mating nuts and washers, as shown in figure 2.
Step 6: the pouring gate is made of the wood pattern and the sodium silicate sand, the sodium silicate sand is baked for 6 hours at 450 ℃ in a resistance furnace and taken out for air cooling, and the sodium silicate sand pouring gate 6 is made, as shown in fig. 3.
And 7: and (3) according to the sand moulds divided in the step (2), assembling the sand mould prepared in the step (4) and the sodium silicate sand runner prepared in the step (6), and connecting the large plane of the sand mould by using a casting binder to ensure that the large sand mould block does not shake.
And 8: on a clean plane, the self-locking tool manufactured in the step 5 and the sand mold 2 combined in the step 7 are spliced, and after assembly, as shown in fig. 4, the nut 5 only needs to be screwed, so that the sand mold is prevented from being crushed.
And step 9: and (3) filling and compacting the sodium silicate sand under the self-locking tool placement platform in the step (2), determining that the sectional filling height of the sodium silicate sand is 120mm, extruding and compacting the sodium silicate sand in sections, filling the next layer of the sodium silicate sand after the upper layer is hardened, completing the molding of the sodium silicate sand according to the size of the sand mold by analogy, and ensuring that the top end of the sand mold is filled with at least 150mm of the sodium silicate sand and hardening the sodium silicate sand.
Step 10: and (5) pouring the sand mould in the step 9 in an anti-gravity low-pressure mode to obtain a casting. Casting mold temperature: normal temperature, casting temperature: 730-740 ℃, liquid rising/filling speed: 50mm/s, solidification pressure difference: 30 KPa.
Step 11: and (3) cleaning the sand mould on the surface of the casting in the step (10), cutting off a casting head, and polishing the excess such as burrs on the surface of the casting.
Step 12: the casting of step 11 is heat treated.
Step 13: the casting of step 12 is inspected for chemical composition, mechanical properties, X-ray detection, size, appearance, volume, and weight.
The following description will be made by taking a certain cartridge product as an example.
Firstly, according to a casting structure and a pouring system, parting and 3D printing support addition are completed; manufacturing a sand mold by adopting 3D printing precoated sand; designing and manufacturing a self-locking tool; manufacturing a pouring gate by using a wood pattern and sodium silicate sand; pouring at low pressure by using counter-gravity; cleaning and polishing; heat treatment; and (4) various tests.
Example 1
Taking a casting with the size of 560 multiplied by 245 multiplied by 190mm as an example, the material is ZL114A, the casting has 11 oil path pipes in total, more bosses, different shapes and more sand separating blocks, and the specific steps of the implementation are as follows:
step 1: according to the characteristics of the casting, a pouring system is designed, and the length of the pouring cup and the area of the bottom end plane are properly increased. Wherein, the length of the pouring cup is increased to 100mm, and after the area of the bottom plane is increased, the distance from the edge of the sand mold to the pouring cup is not less than 180 mm;
step 2: a casting of the designed pouring system is divided into types by adopting three-dimensional drawing software, a sodium silicate sand molding fixing and self-locking tool placing platform is arranged at the bottom end of the pouring cup, and the height of the platform is 80mm, as shown in figure 1.
And step 3: and (4) adding a support to facilitate the shape taking according to the shape forming result in the step 2.
And 4, step 4: and (3) printing the sand mold blocks designed in the step (3) by using precoated sand, and cleaning, baking and finishing different cores after printing. Wherein, the baking process comprises the following steps: baking the sand mold blocks with the height of more than 60mm and the length of more than 150mm at 220 ℃ for 8 hours, cooling the sand mold blocks with the furnace for 4 hours, opening the furnace and cooling the sand mold blocks with air; and (3) baking the core with the diameter of 8mm or 10mm at 200 ℃ for 4h, cooling the core with the furnace for 4 hours, opening the furnace and cooling the core with air.
And 5: manufacturing a self-locking tool according to the requirement of the self-locking tool platform in the step 2; the structure of self-locking frock does: firstly, two channel beams with the length of 700mm are respectively drilled at the positions 40mm away from the edges of the channel beams
Holes, 2,
2 screws, matched nuts and 8 gaskets are arranged on the screw rods, as shown in figure 2.
Step 6: a pouring gate is made of a wood mold and water glass sand, and the wood mold and the water glass sand are baked in a resistance furnace at 450 ℃ for 6 hours and then taken out for air cooling.
And 7: and (3) according to the sand moulds divided in the step (2), assembling the sand moulds prepared in the step (4) and the step (6), and connecting the large planes of the sand moulds by using a casting binder to ensure that large sand mould blocks do not shake.
And 8: on a clean plane, the self-locking tool manufactured in the step 5 and the sand mould assembled in the step 7 are spliced, and the screws only need to be screwed down, so that the sand mould is prevented from being crushed.
And step 9: and (3) filling and compacting the sodium silicate sand in the platform reserved in the step (2), determining that the sectional filling height of the sodium silicate sand is 120mm, extruding and compacting the sodium silicate sand in sections, filling the next layer of the sodium silicate sand after the upper layer is hardened, completing the molding of the sodium silicate sand according to the size of the sand mold, and ensuring that the top end of the sand mold is filled with at least 150mm of the sodium silicate sand and the sodium silicate sand is fully hardened.
Step 10: and (4) pouring the sand mould in the step 9 in a counter-gravity low-pressure mode. Casting mold temperature: normal temperature, casting temperature: 730-740 ℃, liquid rising/filling speed: 50mm/s, solidification pressure difference: 30 KPa.
Step 11: and (5) cleaning the sand mould on the surface of the casting in the step (10), cutting off a casting head, and polishing the burrs and other redundancies on the surface of the casting.
Step 12: and (4) carrying out heat treatment on the casting in the step (11).
Step 13: the step 12 casting is tested for chemical composition, mechanical properties, X-ray detection, size, appearance, volume, and weight.
According to the sand mold produced by the method, the operation of workers is simple in the combination process, each sand mold block does not have a protruding part and is tightly connected, the box lifting does not occur in the antigravity pouring process, the size precision reaches the requirement of HB6103CT6, the wall thickness is uniform, the weight deviation is 4.3%, and the volume deviation is 3.7%. The internal metallurgical quality of the cast reaches the standard of HB963 II type castings through X-ray detection.
Example 2
By size
The casting with the integral wall thickness of 10mm is exemplified by the material ZL105, and is basin-shaped, large in radian and hollow in inner cavity. The required mold filling pressure difference is large, the mold filling pressure is large due to the fact that the end face is large, meanwhile, the cost of the required 3D printing pouring gate sand mold is extremely high, and the method comprises the following specific steps:
step 1: according to the characteristics of the casting, a pouring system is designed, and the length of the pouring cup and the area of the bottom end plane are properly increased. Wherein, the length of the post pouring cup is increased to 120mm, and the distance from the edge of the sand mold to the pouring cup is not less than 220mm after the plane area of the bottom end is increased;
step 2: and (3) parting the casting of the designed pouring system by adopting three-dimensional drawing software, and arranging a sodium silicate sand molding fixing and self-locking tool placing platform at the bottom end of the pouring cup, wherein the height of the platform is 100 mm.
And step 3: and (4) adding a support to facilitate the shape taking according to the shape forming result in the step 2.
And 4, step 4: and (3) printing the sand mold blocks designed in the step (3) by using precoated sand, and cleaning, baking and finishing different cores after printing. The whole casting sand mold block is large, so that the baking process is as follows: baking at 220 deg.C for 8 hr, cooling in furnace for 4 hr, opening furnace, and air cooling.
And 5: manufacturing a self-locking tool according to the requirement of the self-locking tool platform in the step 2; the structure of self-locking frock does: firstly, two channel beams with the length of 1000 are respectively drilled at the position 40mm away from the edge of the channel beam
Holes, 2,
2 screws, 8 matched nuts and gaskets.
Step 6: the pouring gate is made of a wood mold and sodium silicate sand, baked for 6 hours at 450 ℃ in a resistance furnace, taken out and air-cooled.
And 7: and (3) according to the sand moulds divided in the step (2), assembling the sand moulds prepared in the step (4) and the step (6), and connecting the large planes of the sand moulds by using a casting binder to ensure that large sand mould blocks do not shake.
And 8: on a clean plane, the self-locking tool manufactured in the step 5 and the sand mould assembled in the step 7 are spliced, and the screws only need to be screwed down, so that the sand mould is prevented from being crushed.
And step 9: and (3) filling and compacting the sodium silicate sand in the platform reserved in the step (2), determining that the sectional filling height of the sodium silicate sand is 120mm, extruding and compacting the sodium silicate sand in sections, filling the next layer of the sodium silicate sand after the upper layer is hardened, completing the molding of the sodium silicate sand according to the size of the sand mold, and ensuring that the top end of the sand mold is filled with at least 150mm of the sodium silicate sand and the sodium silicate sand is fully hardened.
Step 10: and (4) pouring the sand mould in the step 9 in a counter-gravity low-pressure mode. Casting mold temperature: normal temperature, casting temperature: 730-740 ℃, liquid rising/filling speed: 100mm/s, solidification pressure difference: 38 KPa.
Step 11: and (5) cleaning the sand mould on the surface of the casting in the step (10), cutting off a casting head, and polishing the burrs and other redundancies on the surface of the casting.
Step 12: and (4) carrying out heat treatment on the casting in the step (11).
Step 13: the step 12 casting is tested for chemical composition, mechanical properties, X-ray detection, size, appearance, volume, and weight.
According to the sand mold produced by the method, the operation of workers is simple in the combination process, each sand mold block does not have a protruding part and is tightly connected, when the anti-gravity low-pressure pouring is carried out, the mold filling pressure is huge due to the large projection area of the sand mold, the mold lifting or the sand mold breakage still does not occur, the size precision reaches the requirement of HB6103CT6, the wall thickness is not changed, the large circle is uniform, the single-mold concentricity reaches 0.9%, the weight deviation is 3.2%, and the volume deviation is 2.6%. The internal metallurgical quality of the cast reaches the standard of HB963 II type castings through X-ray detection.
Example 3
Taking casting with the size of 295mm multiplied by 180mm multiplied by 240mm as an example, the material is ZL114A, the casting is in a hemispherical closed shape, the wall thickness of the whole body is 4mm, and the casting is hollow, and the specific steps of the implementation are as follows:
step 1: according to the characteristics of the casting, a pouring system is designed, and the length of the pouring cup and the area of the bottom end plane are properly increased. Wherein, the length of the post pouring cup is increased to 80mm, and the distance from the edge of the sand mold to the pouring cup is not less than 160mm after the plane area of the bottom end is increased;
step 2: and (3) parting the casting of the designed pouring system by adopting three-dimensional drawing software, and arranging a sodium silicate sand molding fixing and self-locking tool placing platform at the bottom end of the pouring cup, wherein the height of the platform is 70 mm.
And step 3: and (4) adding a support to facilitate the shape taking according to the shape forming result in the step 2.
And 4, step 4: and (3) printing the sand mold blocks designed in the step (3) by using precoated sand, and cleaning, baking and finishing different cores after printing. The whole casting sand mold block is large, so that the baking process is as follows: baking at 220 deg.C for 8 hr, cooling in furnace for 4 hr, opening furnace, and air cooling.
And 5: and (3) manufacturing the self-locking tool according to the requirement of the self-locking tool platform in the step 2. (ii) a The structure of self-locking frock does: firstly, two channel beams with the length of 700 are respectively drilled at the positions 40mm away from the edges of the channel beams
Holes, 2,
2 screws, matched nuts and 8 gaskets are arranged on the screw rods, as shown in figure 2.
Step 6: the pouring gate is made of a wood mold and sodium silicate sand, baked for 6 hours at 450 ℃ in a resistance furnace, taken out and air-cooled.
And 7: according to the sand moulds divided in the step 2, the sand moulds prepared in the step 5 and the step 6 are assembled, and a casting binder is used for connecting the large planes of the sand moulds, so that the large sand mould blocks are prevented from shaking.
And 8: on a clean plane, the self-locking tool manufactured in the step 5 and the sand mould assembled in the step 7 are spliced, and the screws only need to be screwed down, so that the sand mould is prevented from being crushed.
And step 9: and (3) filling and compacting the sodium silicate sand in the platform reserved in the step (2), setting the sectional filling height of the sodium silicate sand to be 120mm, extruding and compacting the sodium silicate sand in sections, filling the next layer of the sodium silicate sand after the upper layer is hardened, completing the molding of the sodium silicate sand according to the size of the sand mold, and ensuring that the top end of the sand mold is filled with at least 150mm of the sodium silicate sand and the sodium silicate sand is fully hardened.
Step 10: and (4) pouring the sand mould in the step 9 in a counter-gravity low-pressure mode. Casting mold temperature: normal temperature, casting temperature: 730-740 ℃, liquid rising/filling speed: 50mm/s, solidification pressure difference: 32 KPa.
Step 11: and (5) cleaning the sand mould on the surface of the casting in the step (10), cutting off a casting head, and polishing the burrs and other redundancies on the surface of the casting.
Step 12: and (4) carrying out heat treatment on the casting in the step (11).
Step 13: the step 12 casting is tested for chemical composition, mechanical properties, X-ray detection, size, appearance, volume, and weight.
According to the sand mold produced by the method, the operation of workers is simple in the combination process, each sand mold block does not have a protruding part and is tightly connected, the mold filling pressure is huge during antigravity low-pressure pouring, the mold lifting does not occur, the size precision reaches the requirement of HB6103CT5, the wall thickness is not changed, the weight deviation is 3.4%, and the volume deviation is 2.6%. The internal metallurgical quality of the alloy reaches the standard requirement of HB963 II castings through X-ray detection.
Example 4
By size
The casting is prepared from ZL205A, has inverted V-shaped 90% wall thickness of 15mm and hollow middle part, and is implemented by the following specific steps：
Step 1: according to the characteristics of the casting, a pouring system is designed, and the length of the pouring cup and the area of the bottom end plane are properly increased. Wherein, the length of the post pouring cup is increased to 80mm, and the distance from the edge of the sand mold to the pouring cup is not less than 150mm after the plane area of the bottom end is increased;
step 2: and (3) parting the casting of the designed pouring system by adopting three-dimensional drawing software, and arranging a sodium silicate sand molding fixing and self-locking tool placing platform at the bottom end of the pouring cup, wherein the height of the platform is 70 mm.
And step 3: and (4) adding a support to facilitate the shape taking according to the shape forming result in the step 2.
And 4, step 4: and (3) printing the sand mold blocks designed in the step (3) by using precoated sand, and cleaning, baking and finishing different cores after printing. The whole casting sand mold block is large, so that the baking process is as follows: baking at 220 deg.C for 8 hr, cooling in furnace for 4 hr, opening furnace, and air cooling.
And 5: manufacturing a self-locking tool according to the requirement of the self-locking tool platform in the step 2; (ii) a The structure of self-locking frock does: firstly, two channel beams with the length of 500 are respectively drilled at the positions 40mm away from the edges of the channel beams
Holes, 2,
2 screws, 8 matched nuts and gaskets.
Step 6: the pouring gate is made of a wood mold and sodium silicate sand, baked for 6 hours at 450 ℃ in a resistance furnace, taken out and air-cooled.
And 7: and (3) according to the sand moulds divided in the step (2), assembling the sand moulds prepared in the step (4) and the step (6), and connecting the large planes of the sand moulds by using a casting binder to ensure that large sand mould blocks do not shake.
And 8: on a clean plane, the self-locking tool manufactured in the step 5 and the sand mould assembled in the step 7 are spliced, and the screws only need to be screwed down, so that the sand mould is prevented from being crushed.
And step 9: and (3) filling and compacting the sodium silicate sand in the platform reserved in the step (2), setting the sectional filling height of the sodium silicate sand to be 120mm, extruding and compacting the sodium silicate sand in sections, filling the next layer of the sodium silicate sand after the upper layer is hardened, completing the molding of the sodium silicate sand according to the size of the sand mold, and ensuring that the top end of the sand mold is filled with at least 150mm of the sodium silicate sand and the sodium silicate sand is fully hardened.
Step 10: and (4) pouring the sand mould in the step 9 in a counter-gravity low-pressure mode. Casting mold temperature: normal temperature, casting temperature: 720-730 ℃, liquid rising/filling speed: 150mm/s, solidification pressure difference: 45 KPa.
Step 11: and (5) cleaning the sand mould on the surface of the casting in the step (10), cutting off a casting head, and polishing the burrs and other redundancies on the surface of the casting.
Step 12: and (4) carrying out heat treatment on the casting in the step (11).
Step 13: the step 12 casting is tested for chemical composition, mechanical properties, X-ray detection, size, appearance, volume, and weight.
According to the sand mold produced by the method, the operation of workers is simple in the combination process, each sand mold block does not have a protruding part and is tightly connected, the mold filling speed is high and the mold filling pressure is huge during antigravity low-pressure pouring due to the fact that the wall thickness of the whole sand mold is large, the mold filling pressure is not large, the sand mold is not damaged, the size precision of a casting reaches the requirement of HB6103CT6, the wall thickness is uniform, the weight deviation is 2.4%, and the volume deviation is 1.9%. The internal metallurgical quality of the alloy reaches the standard of HB 963I castings through X-ray detection.
The method is suitable for production of castings combining sodium silicate sand molding, antigravity pouring and 3D printing sand molds, provides a self-locking tool of the 3D sand molds, and adopts the sodium silicate sand molding to manufacture the pouring gate so as to save the production cost of the castings. The method has the following advantages:
1) the self-locking tool is simple to manufacture and can be repeatedly used, the 3D printing sand mold is assembled into a whole similar to a mold shell through the self-locking device, the problem that a box is lifted during anti-gravity pouring after the sand mold is bonded is solved, the size precision of a casting is improved, and the weight and the volume deviation amplitude of the casting are reduced.
2) When the casting is divided, the self-locking tool placing platform is arranged at the bottom end of the pouring gate, so that convenience is brought to sand mold carrying, the self-locking tool placing platform can be used as a water glass sand filling area, after the water glass sand is hardened, the friction force between the sand mold and the sand box is increased, and the sand mold is prevented from falling off in the sand box carrying process.
3) The pouring gate is made of the wood pattern and the water glass sand, so that the production cost of the casting can be effectively saved.
4) The sectional sodium silicate sand is molded, tamped and hardened, the binding force between the 3D printing sand mold and the sand box is favorably increased, the sand mold is prevented from falling off in the carrying process, meanwhile, a large amount of sodium silicate sand is filled at the top end of the sand mold, the lifting and even breaking of the sand mold in the pouring process are reduced, the dimensional precision of a casting is improved, the weight and the volume deviation are reduced, particularly for a round casting, the pouring pressure borne by the upper end face is huge, and the dimensional precision and the circular concentricity of the casting can be greatly improved.
5) By adopting the method to fix the 3D printing sand mold, the sand mold is not lifted, the top end is not broken and eccentrically shaken due to large mold filling pressure, the stability of the pouring process is improved, and the stability of the metallurgical quality of the casting is improved.
6) By adopting the method to fix the 3D printing sand mold, the problem of lifting the mold is not required to be considered during parting, the rationality of parting of complex castings can be increased, and the counter-gravity pouring mode and the 3D printing sand mold production mode are better combined.
7) The invention avoids sand mold lifting from the design angle, and the pouring gate is made of wood pattern and sodium silicate sand.
The invention solves the problem of sand mold box lifting caused by large antigravity pouring mold filling pressure, so that the 3D printing sand mold has no crack, delamination or even fracture, the size tolerance of the casting reaches the level of HB6103CT6, the weight and volume deviation of the casting is less than or equal to 5 percent, and the production cost of the casting is greatly lower. The invention provides a solid foundation for smooth production of castings by combining a 3D printing sand mold and a counter-gravity pouring mode.
Claims (1)
1. The 3D printing sand mold antigravity casting forming method is characterized by comprising the following steps of:
step 1: designing a gating system according to the characteristics of the casting;
step 2: parting a casting of the designed pouring system by adopting three-dimensional drawing software, and arranging a sodium silicate sand molding and self-locking tool placing platform at the bottom end of the pouring cup;
and step 3: adding supports according to the parting result in the step 2 to facilitate parting;
and 4, step 4: adopting the precoated sand to print the sand mold blocks and cores added with supports in the step 3, and cleaning, baking and finishing different sand mold blocks after printing is finished;
and 5: manufacturing a self-locking tool matched with the self-locking tool placing platform; the self-locking tool comprises two channel steels (3), two screws (4) are arranged between the two channel steels, the two screws (4) are arranged in parallel, and two ends of each screw (4) penetrate through the channel steels and are fixed;
step 6: manufacturing a pouring gate by adopting a wood pattern and sodium silicate sand, baking the sodium silicate sand at 450 ℃ for 6 hours, taking out the sodium silicate sand, and air cooling to manufacture a finished sodium silicate sand pouring gate;
and 7: assembling the sand mold prepared in the step 4 and the sodium silicate sand runner prepared in the step 6;
and 8: splicing the self-locking tool manufactured in the step 5 with the sand mold combined in the step 7;
and step 9: filling and compacting sodium silicate sand under the self-locking tool placement platform in the step 2 to form a sand mold; the filling height of the sodium silicate sand is 120mm in sections, the sodium silicate sand is compacted in sections, the next layer of sodium silicate sand is filled after the upper layer is hardened, the sodium silicate sand is shaped by analogy according to the size of the sand mould, and the top end of the sand mould is ensured to be filled with at least 150mm of sodium silicate sand and hardened;
step 10: pouring the sand mould in the step 9 in an anti-gravity low-pressure mode to obtain a casting;
in the step 1, the length of a pouring cup of a pouring system is 100mm, and the distance from the edge of a sand mold to the pouring cup is not less than 180 mm;
in the step 2, the height of the self-locking tool placing platform is 80 mm;
in the step 4, the baking process comprises the following steps: baking the sand mold blocks with the height of more than 60mm and the length of more than 150mm at 220 ℃ for 8 hours, cooling the sand mold blocks with the furnace for 4 hours, opening the furnace and cooling the sand mold blocks with air; baking a core with the diameter of 8mm or 10mm at 200 ℃ for 4h, cooling the core with the furnace for 4 hours, opening the furnace and cooling the core with air;
in step 10, casting temperature: normal temperature, casting temperature: 730-740 ℃, liquid rising/filling speed: 50mm/s, solidification pressure difference: 30 KPa; the dimensional tolerance of the casting reaches the level of HB6103CT6, the weight and volume deviation of the casting is less than or equal to 5 percent, and the metallurgical quality reaches the standard of HB963 II type castings.
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| CN110405211B (en) * | 2019-07-10 | 2020-09-01 | 南京中科煜宸激光技术有限公司 | Flexible equipment for laser fused deposition and sand mold support composite printing |
| CN110538994B (en) * | 2019-07-10 | 2020-06-16 | 南京中科煜宸激光技术有限公司 | Arc fuse and sand mold support composite printing flexible equipment and printing method |
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