阅读说明：本技术 一种基于3d打印制备砂型模壳的铸造方法 (Casting method for preparing sand mold shell based on 3D printing ) 是由 屈志 王伟 张唯 贺伟 陈功代 王强 闫国栋 金枫 张全艺 于 2020-06-12 设计创作，主要内容包括：本发明公开一种基于3D打印制备砂型模壳的铸造方法,包括：采用三维制图软件构建三维中空砂型模壳并3D打印输出；将打印输出的三维中空砂型模壳进行涂覆耐火涂料处理或加热固化处理；向砂箱中填入原砂将三维中空砂型模壳包覆起来,同时进行振实；然后在砂箱的顶部铺上一层塑料薄膜密封,在塑料薄膜上均匀的铺上薄砂,预留浇口杯安装位置,并在该位置上放置浇口杯后继续填入原砂、振实；利用抽气管道对砂箱内部进行抽真空；将金属合金液浇入砂箱内三维中空砂型模壳的空腔；待浇注的合金溶液凝固后,关闭抽真空系统,继续冷却后,开砂箱取出模壳并进行表面清理,获得铸件。本发明结合3D打印技术以及铸造工艺,提高了生产效率,实现了规模化生产。(The invention discloses a casting method for preparing a sand mould shell based on 3D printing, which comprises the following steps: constructing a three-dimensional hollow sand mold shell by adopting three-dimensional drawing software and carrying out 3D printing output; carrying out refractory coating treatment or heating curing treatment on the three-dimensional hollow sand mold shell which is printed and output; filling the sand box with raw sand to coat the three-dimensional hollow sand mould shell, and simultaneously compacting; then laying a layer of plastic film on the top of the sand box for sealing, uniformly laying thin sand on the plastic film, reserving a pouring cup mounting position, placing the pouring cup on the position, then continuously filling the raw sand and compacting; vacuumizing the interior of the sand box by using an air exhaust pipeline; pouring metal alloy liquid into a cavity of a three-dimensional hollow sand mould shell in a sand box; and after the poured alloy solution is solidified, closing the vacuum pumping system, continuously cooling, opening the sand box, taking out the formwork, and cleaning the surface to obtain the casting. The invention combines the 3D printing technology and the casting process, improves the production efficiency and realizes large-scale production.)

1. The casting method for preparing the sand mold shell based on 3D printing is characterized by comprising the following steps of:

step S1: constructing a three-dimensional hollow sand mould shell according to the geometric shape and the casting performance of a casting by adopting three-dimensional drawing software;

step S2: printing and outputting the three-dimensional hollow sand mould shell by using a 3D printer and sand mould raw materials; the sand mould raw materials comprise: raw sand, a binder and an auxiliary additive; the raw sand is common sand or special sand; the special sand is at least one of ceramsite sand, precious pearl sand and chrome ore sand; the binder is at least one of furan resin, phenolic resin, urethane resin, clay and inorganic salt, and the auxiliary additive is at least one of coal powder, starch, graphite powder, iron oxide powder, a release agent and residual oil;

step S3: coating refractory paint on the inner surface of the three-dimensional hollow sand mold shell which is printed and output, and drying in a baking oven or a microwave oven within a set temperature range; the set temperature range is 100-300 ℃; the thickness of the fire-resistant coating is 0.05-4.0 mm;

or heating the three-dimensional hollow sand mold shell which is printed and output to 120-200 ℃ for curing treatment;

step S4: putting the three-dimensional hollow sand mold shell obtained in the step S3 into a sand box, filling raw sand into the sand box to coat the three-dimensional hollow sand mold shell, and simultaneously performing compaction; then laying a layer of plastic film on the top of the sand box for sealing, uniformly laying 10-50 mm of thin sand on the plastic film, reserving a pouring cup installation position, placing the pouring cup on the position, then continuously filling the raw sand and compacting;

step S5: connecting an air exhaust pipeline, and vacuumizing the interior of the sand box by using the air exhaust pipeline to control the negative pressure of the sand box within a set pressure range;

step S6: pouring metal alloy liquid into a cavity of the three-dimensional hollow sand mold shell in the sand box through a pouring cup; the metal alloy liquid is obtained by smelting in a natural gas furnace, an electric furnace, a smelting furnace, an intermediate frequency furnace or an electric arc furnace;

step S7: after the poured alloy solution is solidified, after the first set time, closing the vacuum pumping system, after the alloy solution is continuously cooled for a second set time, opening the sand box, taking out the formwork, and carrying out surface cleaning to obtain a casting; the first set time is 1-5 min, and the second set time is 1-10 hours.

2. The casting method for preparing a sand mold shell based on 3D printing according to claim 1, further comprising before step S4: and filling a layer of raw sand at the bottom of the sand box.

3. The casting method for preparing the sand mold shell based on 3D printing according to claim 1, wherein the acceleration of tapping is controlled to be 10-20 m/s²The time is 10-90 s.

4. The casting method for preparing the sand mold shell based on 3D printing according to claim 1, wherein the set pressure range is-600 to-300 kPa.

5. The casting method for preparing a sand mold shell based on 3D printing according to claim 1, wherein the three-dimensional mapping software is CAE software or UG software or CATIA software or PROE software or SO L IDWORK software.

6. A casting method for preparing a sand mould shell based on 3D printing according to claim 1, characterised in that the refractory coating is applied by at least one of brushing, dipping, flow coating and spraying.

7. A casting method for preparing a sand mould shell based on 3D printing according to claim 1, characterised in that the 3D printer comprises a 3DP sand mould printer and an S L S printer.

Technical Field

The invention relates to the technical field of metal casting forming and additive manufacturing, in particular to a casting method for preparing a sand mold shell based on 3D printing.

Background

Casting is the most important method for obtaining mechanical part blanks and plays an important role in industrial production. The sand casting is the most common casting production mode with the widest application, and the traditional sand casting method needs to use a manual or molding machine to prepare the sand mold, so that three obvious disadvantages exist in the use of the sand mold, firstly, the manufacture of the sand mold needs to use a large amount of binder, and most of the binder has strong smell and is harmful to human bodies; secondly, a large amount of dust pollution is generated in the stages of sand pre-treatment and post-treatment and casting cleaning, which is not favorable for the environment; thirdly, the sand mold manufacturing process is relatively complicated and the construction period is long.

The V-method casting technology and the lost foam casting technology are novel casting methods of metal castings developed in the 60-80 th century, have the advantages of high size precision of the castings, high surface smoothness, less subsequent machining allowance, good economy and the like, have the common characteristics of adopting a vacuum sealing molding sand mold and maintaining strength, avoid using a binder, have the characteristics of cleanness and environmental protection, and are called as green casting technologies of the 21 st century. In recent decades, V-process casting technology and lost foam casting technology have been rapidly developed and applied worldwide.

However, the lost foam casting technology is limited in that the white mold production process is complex, a matched steam system is required, and the energy consumption is high; on the other hand, the white mold is large in gas amount generated by cracking in the presence of high-temperature molten metal, so that the casting is easy to form a pore defect, the casting is easy to carburize, and the components and the structure of the casting are difficult to control. In addition, the risk of metal liquid back spraying may exist in the pouring process, and certain danger is caused. The V-method casting technology has the defects that a wood mold or a metal mold needs to be manufactured firstly, the mold manufacturing cost is high, the period is long, the molding process is complex, the yield is low, and the hollow casting still cannot be separated from the sand core.

The 3D printing technology is a new material forming technology that emerged at the end of the 20 th century and is soon applied in the field of casting. At the present stage, the 3D printing method for preparing the sand mold has obvious advantages in the aspects of single-piece, small-batch and high-complexity-coefficient casting production and product trial production because mold opening is not needed, but the 3D printing method is not deeply combined with the traditional V method, lost foam or sand mold casting process, and compared with an automatic molding machine, a core shooter and the like of the sand mold, the 3D printing method is relatively low in production efficiency, and large-scale application is difficult to realize at present.

Disclosure of Invention

Based on the above, the invention aims to provide a casting method for preparing a sand mold shell based on 3D printing, so that large-scale printing and application are realized.

In order to achieve the purpose, the invention provides a casting method for preparing a sand mold shell based on 3D printing, which comprises the following steps:

step S1: constructing a three-dimensional hollow sand mould shell according to the geometric shape and the casting performance of a casting by adopting three-dimensional drawing software;

step S2: printing and outputting the three-dimensional hollow sand mould shell by using a 3D printer and sand mould raw materials;

step S3: coating refractory paint on the inner surface of the three-dimensional hollow sand mold shell which is printed and output, and drying in a baking oven or a microwave oven within a set temperature range;

or heating the three-dimensional hollow sand mold shell which is printed and output to 120-200 ℃ for curing treatment;

step S4: putting the three-dimensional hollow sand mold shell obtained in the step S3 into a sand box, filling raw sand into the sand box to coat the three-dimensional hollow sand mold shell, and simultaneously performing compaction; then laying a layer of plastic film on the top of the sand box for sealing, uniformly laying 10-50 mm of thin sand on the plastic film, reserving a pouring cup installation position, placing the pouring cup on the position, then continuously filling the raw sand and compacting;

step S5: connecting an air exhaust pipeline, and vacuumizing the interior of the sand box by using the air exhaust pipeline to control the negative pressure of the sand box within a set pressure range;

step S6: pouring metal alloy liquid into a cavity of the three-dimensional hollow sand mold shell in the sand box through a pouring cup; the metal alloy liquid is obtained by smelting in a natural gas furnace, an electric furnace, a smelting furnace, an intermediate frequency furnace or an electric arc furnace;

step S7: and after the poured alloy solution is solidified, after the first set time, closing the vacuumizing system, continuously cooling for a second set time, opening the sand box, taking out the formwork, and cleaning the surface to obtain the casting.

Optionally, before step S4, the method further includes: and filling a layer of raw sand at the bottom of the sand box.

Optionally, the set temperature range is 100-300 ℃, the first set time is 1-5 min, and the second set time is 1-10 hours.

Optionally, the acceleration of the tap is controlled to be 10-20 m/s²The time is 10-90 s.

Optionally, the set pressure range is-600 to-300 kPa.

Optionally, the three-dimensional mapping software is CAE software or UG software or CATIA software or pro software or SO L IDWORK software.

Optionally, the refractory coating is applied by at least one of brushing, dipping, flow coating, and spraying.

Optionally, the 3D printer includes a 3DP sand mold printer and an S L S printer.

Optionally, the sand mold raw material comprises: raw sand, a binder and auxiliary additives.

Optionally, the thickness of the fire-resistant coating is 0.05-4.0 mm.

According to the specific embodiment provided by the invention, the invention discloses the following technical effects:

the invention discloses a casting method for preparing a sand mould shell based on 3D printing, which comprises the following steps: constructing a three-dimensional hollow sand mold shell by adopting three-dimensional drawing software and carrying out 3D printing output; carrying out refractory coating treatment or heating curing treatment on the three-dimensional hollow sand mold shell which is printed and output; filling the sand box with raw sand to coat the three-dimensional hollow sand mould shell, and simultaneously compacting; then laying a layer of plastic film on the top of the sand box for sealing, uniformly laying thin sand on the plastic film, reserving a pouring cup mounting position, placing the pouring cup on the position, then continuously filling the raw sand and compacting; vacuumizing the interior of the sand box by using an air exhaust pipeline; pouring metal alloy liquid into a cavity of a three-dimensional hollow sand mould shell in a sand box; and after the poured alloy solution is solidified, after the first set time, closing the vacuumizing system, continuously cooling for a second set time, opening the sand box, taking out the formwork, and cleaning the surface to obtain the casting. The invention combines the 3D printing technology and the casting process, improves the production efficiency and realizes large-scale production.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.

Fig. 1 is a flow chart of a casting method for preparing a sand mold shell based on 3D printing according to an embodiment of the present invention;

FIG. 2 is a three-dimensional hollow sand mold shell structure diagram of a coated connecting rod sleeve casting in an embodiment of the invention;

fig. 3 is an explosion structure diagram of a three-dimensional hollow sand mold shell of a coated impeller casting according to an embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The invention aims to provide a casting method for preparing a sand mold shell based on 3D printing, so that large-scale printing and application are realized.

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.

The invention provides a casting method for preparing a sand mold shell based on 3D printing, which comprises the following steps:

step S1: and (3) constructing a three-dimensional hollow sand mold shell by adopting three-dimensional drawing software according to the geometric shape and the casting performance of the casting. The casting properties include structural processing properties and material processing properties.

Step S2: and printing and outputting the three-dimensional hollow sand mold shell by using a 3D printer and sand mold raw materials.

Step S3: coating refractory paint on the inner surface of the three-dimensional hollow sand mold shell which is printed and output, and drying in a baking oven or a microwave oven within a set temperature range; the set temperature range is 100-300 ℃.

Or heating the three-dimensional hollow sand mold shell which is printed and output to 120-200 ℃ for curing treatment.

Step S4: putting the three-dimensional hollow sand mold shell obtained in the step S3 into a sand box, filling raw sand into the sand box to coat the three-dimensional hollow sand mold shell, and simultaneously performing compaction; and then, laying a layer of plastic film on the top of the sand box for sealing, uniformly laying 10-50 mm of thin sand on the plastic film, placing a pouring cup on the thin sand, then continuously filling the raw sand, and compacting. The invention lays thin sand to prevent high-temperature liquid from splashing and scalding.

Step S5: connecting an air exhaust pipeline, and vacuumizing the interior of the sand box by using the air exhaust pipeline to control the negative pressure of the sand box within a set pressure range; the set pressure range is-600 to-300 kPa.

Step S6: pouring metal alloy liquid into a cavity of the three-dimensional hollow sand mold shell in the sand box through a pouring cup; the metal alloy liquid is obtained by smelting in a natural gas furnace, an electric furnace, a smelting furnace, an intermediate frequency furnace or an electric arc furnace.

Step S7: after the poured alloy solution is solidified, after the first set time, closing the vacuum pumping system, after the alloy solution is continuously cooled for a second set time, opening the sand box, taking out the formwork, and carrying out surface cleaning to obtain a casting; the first set time is 1-5 min, and the second set time is 1-10 hours.

As an alternative embodiment, before step S4, the present invention further includes: and filling a layer of raw sand at the bottom of the sand box.

As an optional implementation mode, the acceleration of the tap of the invention is controlled to be 10-20 m/s²The time is 10-90 s.

As an optional implementation mode, the strength of the three-dimensional hollow sand mold shell after output by the invention is 0.8-6 MPa.

As an optional implementation mode, the three-dimensional drawing software is CAE software or UG software or CATIA software or PROE software or SO L IDWORK software.

As an optional embodiment, the three-dimensional hollow sand mold shell of the present invention may be an empty mold shell, or may be a non-empty mold shell including a core therein, and the core is connected to the three-dimensional hollow sand mold shell; the three-dimensional hollow sand mould shell can be in a shape of only covering a casting, or in a shape of covering the casting and a pouring channel connected with the casting; the three-dimensional hollow sand mould shell can be an integral body or consists of a plurality of three-dimensional hollow sand mould shell components; the wall thickness of the three-dimensional hollow sand mold shell can be uniform or variable, and the wall thickness of the three-dimensional hollow sand mold shell is 5-40 mm; if coated sand is adopted, the thickness is 2mm at the thinnest.

As an optional implementation mode, the 3D printer comprises a 3DP sand mold printer and an S L S printer, wherein the S L S printer is a selective laser sintering sand mold printer.

When the printer adopts a 3DP sand mold printer for printing output, the inner surface of the three-dimensional hollow sand mold shell which is printed out is coated with refractory coating and then dried in a baking oven or a microwave oven within a set temperature range; the set temperature range is 100-300 ℃; the thickness of the fire-resistant coating is 0.05-4.0 mm. The refractory coating is applied by at least one of brushing, dipping, flow coating and spraying.

And when the printer adopts an S L S printer for printing output, heating the three-dimensional hollow sand mold shell for printing output to 120-200 ℃ for curing treatment.

As an optional embodiment, the sand mold raw material of the present invention includes: raw sand, a binder and an auxiliary additive; the raw sand can be common sand or special sand; the special sand is at least one of ceramsite sand, precious pearl sand and chrome ore sand; the binder is at least one of furan resin, phenolic resin, urethane resin, clay and inorganic salt (water-containing glass), and the auxiliary additive is at least one of coal powder, starch, graphite powder, iron oxide powder, a release agent and residual oil. The special sand is used for improving the strength, the air permeability and the cooling effect of the formwork.

The method for preparing the sand mould shell by adopting the 3D printing method has the advantages of high efficiency, low cost, no limitation on the shape of the shell and the like, and can print and form the core, the pouring channel and the shell together, thereby simplifying the molding process. The concrete embodiment is as follows:

compared with the traditional sand casting technology, the invention adopts the thin sand casting conformal shell to replace the full-size sand mold (comprising a core), and the raw sand at the periphery of the mold shell is fastened by negative pressure, so that the sand grains are not bonded by using a bonding agent any more, and only the mold shell with the thickness of 5-40 mm (the thinnest of the precoated sand can be up to 2 mm) needs to use the bonding agent, so that the use of the bonding agent can be greatly reduced (the use amount of the bonding agent is reduced by more than 90%), the gas pollution emission is less, and the environment is more environment-friendly. Compared with the prior art that the full-size 3D printing sand mold and sand casting are combined, the full-size 3D printing sand mold is more environment-friendly, and the printing time is shortened and the production efficiency is higher due to the fact that only a thin mold shell is printed.

Compared with the traditional technology of combining the carving foam model with the lost foam casting, the invention adopts the thin sand mould shell to replace the shell made of the white mould, thereby directly saving the generation procedure of the whole 'white area' of the lost foam casting, greatly simplifying the process flow, avoiding the gas generated by the cracking of the white mould in the casting stage, preventing the recarburization, reducing the possibility of forming the air hole defect, greatly improving the quality of the casting, having no pollution caused by the burning of the white mould and really realizing the green casting.

Compared with the V-method casting technology, the use of the sand mould shell directly saves the manufacturing procedures of the mould sample and the mould plate, saves the manufacturing cost of the mould sample and the mould plate, can also avoid the procedures of mould assembling, core setting and the like, greatly simplifies the process flow and improves the production efficiency.