3D printing inorganic binder system based on infrared heating hardening and sand mold preparation method

Abstract

The invention discloses a 3D printing inorganic binder system based on infrared heating hardening and a sand mold preparation method, and particularly relates to the technical field of casting 3D printing. The invention discloses a 3D printing inorganic binder system based on infrared heating hardening. The system is composed of two independent liquids including an inorganic binder and a reinforcing agent. A sand mold preparation method based on the 3D printing inorganic binder system in claim 1 comprises the following steps: (1) premixing a reinforcing agent and silica sand; (2) laying the premixed sand on a printing platform through a sand laying device; (3) spraying an inorganic binder in a set area by adopting a 3D printing nozzle; (4) curing layer by layer through an infrared heating device; and (5) repeating the steps (2)-(4) to finish sand mold printing, and finally removing floating sand to obtain a molded sand mold. According to the method, the adaptability of a sand mold manufacturing process is improved, the interlayer bonding performance of the sand mold is optimized, the structural stability of the sand mold is enhanced, the casting forming quality is improved, the size control precision is improved, and the precision casting requirement is met.

Description

Technical Field

[0001] The present invention belongs to the technical field of casting 3D printing, and particularly relates to a 3D printing inorganic binder system based on infrared heating hardening and a sand mold manufacturing method. Background Art

[0002] In recent years, the inkjet 3D printing technology has been widely introduced into the field of sand mold / sand core manufacturing due to its characteristics of moldless and rapid prototyping of complex structures. This technology significantly improves the flexibility of sand mold design and manufacturing efficiency by spraying the binder layer by layer and selectively curing the sand layer. However, existing processes mostly rely on organic resin-based binders, which can meet the strength requirements of sand molds, but have environmental protection and performance defects such as high emissions of volatile organic compounds (VOCs) and easy carbonization at high temperatures. Therefore, inorganic binders represented by silicates, phosphates, and geopolymers have become a research hotspot, which have significant advantages such as no VOCs emissions, excellent high-temperature stability, and low raw material costs. However, their industrial applications are still restricted by the following key technical bottlenecks: 1. Insufficient initial strength and weak interfacial bonding: The curing mechanism of inorganic binders relies on physical hydration dehydration or slow chemical cross-linking, resulting in the difficulty of the sand mold strength in the initial printing stage to meet the requirements of demolding and handling; at the same time, the interaction efficiency between the binder and the hydroxyl groups on the surface of sand grains is low, and the interfacial chemical bonding density is insufficient, restricting the overall mechanical properties.

[0003] 2. High risk of interlayer bonding failure: The process characteristics of inkjet printing with layer-by-layer stacking require the binder to achieve cross-layer penetration and chemical cross-linking in a short time. However, traditional inorganic binders have low diffusion coefficients and slow gelation rates, which easily lead to the formation of weak interfacial layers in the interlayer transition zone, causing delamination defects.

[0004] 3. Poor environmental adaptability: The water-based inorganic binder system is prone to colloidal softening or ionic bond breakage after absorbing moisture, resulting in the strength of the sand mold decaying by more than 40% within 24 hours in an environment with a humidity ≥ 50%, severely restricting its storage period and application in complex environments.

[0005] The prior art improves the performance by adding reinforcing phases such as nano-silica particles and short carbon fibers or optimizing printing parameters (such as spraying frequency, droplet spacing), but faces the risk of nozzle clogging (≥ 5% volume fraction of nanoparticles may cause nozzle clogging of a nozzle with a diameter of Φ50 μm) or the problem of increased process complexity; while the high-temperature post-treatment process (such as heating at > 200 °C for 2 hours) can improve the strength, but it increases the energy consumption cost by more than 30%, violating the original intention of green manufacturing.

[0006] Therefore, there is an urgent need to develop an inorganic binder system based on a multi-component synergistic enhancement mechanism. By means of interfacial chemical modification and curing kinetics regulation, the contradictions of printing adaptability, mechanical properties, and environmental stability are solved synchronously, providing a sand mold manufacturing solution with both high-efficiency forming and excellent comprehensive properties for green casting. Summary of the Invention

[0007] The object of the present invention is: a 3D printing inorganic binder system based on infrared heating hardening and a preparation method thereof.

[0008] In order to achieve the above object, the present invention provides the following technical solutions: A 3D printing inorganic binder system based on infrared heating hardening, which is composed of two independent liquids, an inorganic binder and a reinforcing agent; The inorganic binder contains the following raw materials in parts by mass: 40-70 parts of sodium silicate, 5-20 parts of potassium silicate, 2-10 parts of sodium hexametaphosphate, 0.5-3 parts of dodecyl betaine, 5-30 parts of polyether-modified polyorganosiloxane 8030F, and 0.5-3 parts of silane coupling agent Si-550; The reinforcing agent contains the following raw materials in parts by mass: 30-60 parts of potassium hydroxide, 5-15 parts of tetramethyl decynediol, 0.5-3 parts of silane coupling agent Si-550, 2-8 parts of polyether-modified polyorganosiloxane 8030F, and 2-8 parts of titanium trichloride-aluminum alkyl.

[0009] Further, the sodium silicate in the inorganic binder is a water glass solution with a modulus of 2.5 and a Baume degree of 40; the potassium silicate is a water glass solution with a modulus of 2.3 and a Baume degree of 35; the purity of the sodium hexametaphosphate is 98%; the active ingredient of the dodecyl betaine is 99%.

[0010] Further, the purity of the potassium hydroxide in the reinforcing agent is 98%; the active ingredient of the tetramethyl decynediol is 99%; the active ingredient of the silane coupling agent Si-550 is 99%.

[0011] Further, the preparation of the inorganic binder includes the following steps: (1) Mix 40-70 parts by mass of sodium silicate, 5-20 parts by mass of potassium silicate with potassium hydroxide and stir for 10 minutes; (2) Heat to 60 °C and then add 2-10 parts by mass of sodium hexametaphosphate, and continue to stir for 20 minutes; (3) Cool down to 30 °C and then add 0.5-3 parts by mass of dodecyl betaine, 5-30 parts by mass of polyether-modified polyorganosiloxane 8030F, and 0.5-3 parts by mass of silane coupling agent Si-550, and stir for 10 minutes.

[0012] Further, the preparation method of the reinforcing agent comprises the following steps: (1) Mix 30 - 60 parts by mass of potassium hydroxide with water and stir for 10 minutes; (2) After cooling to 30°C, add 5 - 15 parts by mass of tetramethyl decynediol, 0.5 - 3 parts by mass of silane coupling agent Si - 550, 2 - 8 parts by mass of polyether - modified polyorganosiloxane 8030F, and 2 - 8 parts by mass of titanium trichloride - alkyl aluminum; (3) Obtain the reinforcing agent after stirring for 10 minutes.

[0013] Further, the viscosity of the inorganic binder ≤ 20 mPa·S and the neutralization degree ≤ 35 Nm / %; the viscosity of the reinforcing agent ≤ 12 mPa·S and the neutralization degree ≤ 35 Nm / %.

[0014] Further, in the preparation method of the inorganic binder, the addition amount of potassium hydroxide in step (1) is 1% - 5% of the mass of potassium silicate.

[0015] Further, in the preparation method of the reinforcing agent, the addition amount of water in step (1) is 10% - 30% of the mass of potassium hydroxide.

[0016] A method for making a sand mold of a 3D - printing inorganic binder system based on infrared heating hardening comprises the following steps: (1) Premix 2 - 8 parts by mass of the reinforcing agent with 100 parts of silica sand; (2) Spread the premixed sand on the printing platform through a sand spreading device; (3) Spray 5 - 30 parts by mass of the inorganic binder in a set area using a 3D - printing nozzle; (4) Cure layer by layer at 60 - 80°C through an infrared heating device; (5) Repeat steps (2) - (4) to complete the sand mold printing, and finally remove the floating sand to obtain the formed sand mold.

[0017] Advantages of the present invention: 1. Improve the adaptability of the sand mold manufacturing process: Through the synergistic effect of a specific ratio of sodium / potassium silicate water glass system and the reinforcing agent, the low - viscosity characteristics of the binder viscosity ≤ 20 mPa·S and the reinforcing agent viscosity ≤ 12 mPa·S are achieved, meeting the requirements of the 3D - printing nozzle for the fluidity of the slurry and adapting to the continuous forming requirements of complex sand mold structures.

[0018] 2. Optimize the inter - layer bonding performance of the sand mold: The titanium trichloride - alkyl aluminum catalyst in the reinforcing agent reacts with the polyether - modified polyorganosiloxane 8030F in the inorganic binder to generate highly active cross - linked bonds under microwave heating conditions, promoting chemical bonding between layers and effectively eliminating the printing delamination phenomenon.

[0019] 3. Enhance the structural stability of the sand mold: Through the bonding effect of the silane coupling agent Si-550 and the silicon-oxygen bond of the inorganic binder, combined with the wetting modification of 2,4,7,9-tetramethyl-5-decyne-4,7-diol in the reinforcing agent, a three-dimensional network cross-linked structure is formed, increasing the compressive strength of the sand mold by more than 40% and reducing the humidity sensitivity to ≤35 Nm / % level.

[0020] 4. Improve the casting forming quality: The amount of gas generated during the curing process of the inorganic binder system is <0.5 mL / g (tested at 1100 °C), which is more than 60% lower than that of the traditional furan resin, effectively reducing the porosity defects of the casting, and the surface roughness of the casting reaches Ra ≤ 6.3 μm.

[0021] 5. Improve the dimensional control accuracy: Through the precise ratio of sodium silicate with a Baume degree of 40 and potassium silicate with a Baume degree of 35, the curing shrinkage rate of the binder system is controlled to ≤0.15%, and the dimensional accuracy error of the sand mold is ≤±0.3 mm / 100 mm, meeting the requirements of precision casting. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is the test result diagram a of the dimensional accuracy of the sand mold.

[0023] Figure 2 It is the test result diagram b of the dimensional accuracy of the sand mold.

[0024] Figure 3 It is the front view comparison diagram of the 3D printed sand mold before and after the modification of the inorganic binder system. DETAILED DESCRIPTION OF THE INVENTION

[0025] The preparation method of the present invention will be described in detail below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0026] Example of 3D printing inorganic binder based on infrared heating and hardening Example 1 (I) Preparation of inorganic binder Add 40 parts of sodium silicate with a modulus of 2.5 and a Baume degree of 40 and 5 parts of potassium silicate with a modulus of 2.3 and a Baume degree of 35 to the reaction vessel and stir for 10 minutes. Heat to 60 °C, add 2 parts of sodium hexametaphosphate with a content of 98%, and continue to stir for 20 minutes. After the mixture is cooled to 30 °C, add 0.5 part of dodecyl betaine with an active ingredient of 99%, 5 parts of polyether-modified polyorganosiloxane 8030F with an active ingredient of 99%, and 0.5 part of silane coupling agent Si-550 in sequence, and stir for 10 minutes to complete the preparation of the inorganic binder. The viscosity of the inorganic binder is measured to be 18 mPa·S, and the neutralization degree is 30 Nm / %.

[0027] (II) Preparation of reinforcing agent Mix 30 parts of potassium hydroxide with a content of 98% and water in a three-necked flask, and stir for 10 minutes. After cooling to 30 °C, add 5 parts of 2,4,7,9-tetramethyl-5-decyne-4,7-diol with an active content of 99%, 0.5 part of silane coupling agent Si-550, 2 parts of polyether-modified polyorganosiloxane 8030F with an active content of 99%, and 2 parts of titanium trichloride-aluminum alkyl, and stir for 10 minutes to obtain a reinforcing agent. The viscosity of the reinforcing agent is measured to be 10 mPa·S, and the neutralization degree is 30 Nm / %.

[0028] (III)Performance Testing Take 2 parts of the reinforcing agent and premix it with 100 parts of 3D printing silica sand. When 3D printing the sand mold, spray 1.8 parts of inorganic binder as needed after spreading the sand, and cure it by infrared heating. Layer by layer, print the "8" specimen. After cleaning the floating sand and taking out the specimen, carry out performance testing.

[0029] Example 2 (I)Preparation of Inorganic Binder Put 70 parts of sodium silicate with a modulus of 2.5 and a Baume degree of 40 and 20 parts of potassium silicate with a modulus of 2.3 and a Baume degree of 35 into a reaction vessel, and stir for 10 minutes. Heat up to 60 °C, put in 10 parts of sodium hexametaphosphate with a content of 98%, and stir for 20 minutes. Cool to 30 °C, add 3 parts of dodecyl betaine with an active content of 99%, 30 parts of polyether-modified polyorganosiloxane 8030F with an active content of 99%, and 3 parts of silane coupling agent Si-550, and stir for 10 minutes to prepare an inorganic binder.

[0030] (II)Preparation of Reinforcing Agent Add 60 parts of potassium hydroxide with a content of 98% and appropriate water to a three-necked flask, and stir for 10 minutes. After cooling to 30 °C, put in 15 parts of 2,4,7,9-tetramethyl-5-decyne-4,7-diol with an active content of 99%, 3 parts of silane coupling agent Si-550, 8 parts of polyether-modified polyorganosiloxane 8030F with an active content of 99%, and 8 parts of titanium trichloride-aluminum alkyl, and stir for 10 minutes to obtain a reinforcing agent.

[0031] (III)Performance Testing Premix 3 parts of the reinforcing agent and 100 parts of 3D printing silica sand. During the 3D printing of the sand mold, spray 1.8 parts of inorganic binder at the designated position after spreading the sand, and cure it by infrared heating. Layer by layer, construct the 8 specimen. After removing the floating sand and taking out the specimen, conduct performance testing.

[0032] Example 3 (I)Preparation of Inorganic Binder Put 50 parts of sodium silicate with a modulus of 2.5 and a Baume degree of 40 and 10 parts of potassium silicate with a modulus of 2.3 and a Baume degree of 35 into a reaction vessel and stir for 10 minutes. Heat to 60 °C, add 8 parts of sodium hexametaphosphate with a content of 98%, and continue to stir for 20 minutes. After cooling to 30 °C, add 2 parts of dodecyl betaine with an active ingredient of 99%, 10 parts of polyether-modified polyorganosiloxane 8030F with an active ingredient of 99% and 2 parts of silane coupling agent Si-550, and stir for 10 minutes to obtain an inorganic binder.

[0033] (II) Preparation of reinforcing agent Mix 40 parts of potassium hydroxide with a content of 98% and water in a three-necked flask and stir for 10 minutes. Cool to 30 °C, add 8 parts of 2,4,7,9-tetramethyl-5-decyne-4,7-diol with an active ingredient of 99%, 1.5 parts of silane coupling agent Si-550, 4 parts of polyether-modified polyorganosiloxane 8030F with an active ingredient of 99% and 5 parts of titanium trichloride-aluminum alkyl, and stir for 10 minutes to prepare a reinforcing agent.

[0034] (III) Performance testing Premix 5 parts of the reinforcing agent with 100 parts of 3D printing silica sand. When 3D printing a sand mold, after laying the sand, spray 1.8 parts of the inorganic binder at the required position, cure it by infrared heating, and print 8 specimens layer by layer. Clean the floating sand and take out the specimens to carry out performance testing work.

[0035] Example 4 (I) Preparation of inorganic binder Add 60 parts of sodium silicate with a modulus of 2.5 and a Baume degree of 40 and 15 parts of potassium silicate with a modulus of 2.3 and a Baume degree of 35 to a reaction vessel and stir for 10 minutes. Heat to 60 °C, put in 7 parts of sodium hexametaphosphate with a content of 98%, and stir for 20 minutes. When the temperature drops to 30 °C, add 1.8 parts of dodecyl betaine with an active ingredient of 99%, 19 parts of polyether-modified polyorganosiloxane 8030F with an active ingredient of 99% and 1.8 parts of silane coupling agent Si-550, and stir for 10 minutes to complete the preparation of the inorganic binder.

[0036] (II) Preparation of reinforcing agent In a three-necked flask, 52 parts of potassium hydroxide with a content of 98% was mixed with water and stirred for 10 minutes. After cooling to 30 °C, 11 parts of tetramethyl decynediol with an active content of 99%, 2.8 parts of silane coupling agent Si-550, 6.5 parts of polyether-modified polyorganosiloxane 8030F with an active content of 99% and 4.6 parts of titanium trichloride-aluminum alkyl were added and stirred for 10 minutes to obtain a reinforcing agent.

[0037] (III) Performance testing 6 parts of the reinforcing agent were premixed with 100 parts of 3D printing silica sand. During the 3D printing of the sand mold, after spreading the sand, 1.8 parts of an inorganic binder were sprayed at the specified position, and infrared heating was used for curing. The "8" specimen was formed layer by layer. After cleaning the surrounding floating sand and taking out the specimen, performance testing was carried out.

[0038] Example 5 (I) Preparation of inorganic binder 42 parts of sodium silicate with a modulus of 2.5 and a Baume degree of 40 and 9 parts of potassium silicate with a modulus of 2.3 and a Baume degree of 35 were added to a reaction vessel and stirred for 10 minutes. After heating to 60 °C, 9 parts of sodium hexametaphosphate with a content of 98% were added and stirred for 20 minutes. After cooling to 30 °C, 0.9 part of dodecyl betaine with an active content of 99%, 22 parts of polyether-modified polyorganosiloxane 8030F with an active content of 99% and 1.2 parts of silane coupling agent Si-550 were added and stirred for 10 minutes to prepare the inorganic binder.

[0039] (II) Preparation of reinforcing agent 49 parts of potassium hydroxide with a content of 98% and water were placed in a three-necked flask and stirred for 10 minutes. After cooling to 30 °C, 14.5 parts of tetramethyl decynediol with an active content of 99%, 1.5 parts of silane coupling agent Si-550, 3.9 parts of polyether-modified polyorganosiloxane 8030F with an active content of 99% and 6.6 parts of titanium trichloride-aluminum alkyl were added and stirred for 10 minutes to prepare the reinforcing agent.

[0040] (III) Performance testing 8 parts of the reinforcing agent were premixed with 100 parts of 3D printing silica sand. When 3D printing the sand mold, after the sand spreading step was completed, 1.8 parts of the inorganic binder were sprayed at the required printing position, and infrared heating was used to promote the curing of the binder. The "8" specimen was printed layer by layer according to the preset program. After printing, the floating sand was carefully cleaned and the specimen was taken out for testing of various performance indicators.

[0041] Table 1: Performance parameter table of examples Table 2: 3D Printed Sand Mold 3D Scanning Results Table Comparative Example 1 (I) Material Composition Furan resin: The addition amount is 1.2% of the mass of silica sand. Curing agent: Phosphate-based acidic curing agent, and the addition amount is 0.4% of the resin mass; (II) Preparation Method 1. Mix 100 parts of silica sand and 1.2 parts of furan resin in a sand mixer for 3 minutes; 2. Add 0.48 parts (0.4% of the resin mass) of the curing agent and continue to mix for 5 minutes; 3. Layer by layer lay sand through a 3D printing device and spray the resin-curing agent mixture; 4. Obtain test specimens after self-hardening and curing at room temperature for 24 hours.

[0042] (III) Performance Test Results Tensile strength at 24h: 2.0 - 2.4 MPa; Residual strength (compressive): <0.5 MPa (Φ50mm cylinder); Gas evolution amount (1100℃): 11.0 mL / g; Sand mold dimensional accuracy ±0.2 mm / 100mm; Moisture absorption resistance: Strength reduction rate <20% (RH80%, 24h).

[0043] Figure 1 and Figure 2 shows the dimensional accuracy detection results of the sand mold in this embodiment. Figure 3 is a comparison diagram of the 3D printed sand mold vertical surfaces before and after modification of the inorganic binder system. The sand mold on the left side of the picture is printed before modification, with obvious step marks, increasing the difficulty of surface treatment and affecting the machining accuracy of the casting; the sand mold on the right side is printed after modification and has good performance.

[0044] Matters not covered in this invention are well-known technologies.

[0045] The above embodiments are only used to illustrate the technical concept and features of the present invention, and the purpose is to enable those who are familiar with this technology to understand the content of the present invention and implement it accordingly, and it should not be used to limit the protection scope of the present invention. All equivalent changes or modifications made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A 3D printing inorganic binder system based on infrared heating hardening, characterized in that, This system consists of two independent liquids, an inorganic binder and a reinforcing agent; The inorganic binder contains the following raw materials in parts by mass: 40 - 70 parts of sodium silicate, 5 - 20 parts of potassium silicate, 2 - 10 parts of sodium hexametaphosphate, 0.5 - 3 parts of dodecyl betaine, 5 - 30 parts of polyether-modified polyorganosiloxane 8030F, and 0.5 - 3 parts of silane coupling agent Si-550; The reinforcing agent contains the following raw materials in parts by mass: 30 - 60 parts of potassium hydroxide, 5 - 15 parts of tetramethyl decynediol, 0.5 - 3 parts of silane coupling agent Si-550, 2 - 8 parts of polyether-modified polyorganosiloxane 8030F, and 2 - 8 parts of titanium trichloride - alkyl aluminum; 2. The 3D printing inorganic binder system based on infrared heating hardening according to claim 1, wherein: The sodium silicate in the inorganic binder is a water glass solution with a modulus of 2.5 and a Baume degree of 40; the potassium silicate is a water glass solution with a modulus of 2.3 and a Baume degree of 35; the purity of the sodium hexametaphosphate is 98%; the active ingredient of the dodecyl betaine is 99%.

3. The 3D printing inorganic binder system based on infrared heating hardening according to claim 1, wherein: The purity of the potassium hydroxide in the reinforcing agent is 98%; the active ingredient of the tetramethyl decynediol is 99%; the active ingredient of the silane coupling agent Si-550 is 99%.

4. The 3D printing inorganic binder system based on infrared heating hardening according to claim 1, wherein: The preparation of the inorganic binder includes the following steps: (1) Mix 40 - 70 parts by mass of sodium silicate, 5 - 20 parts by mass of potassium silicate with potassium hydroxide and stir for 10 minutes; (2) After heating to 60 °C, add 2 - 10 parts by mass of sodium hexametaphosphate and continue stirring for 20 minutes; (3) After cooling to 30 °C, add 0.5 - 3 parts by mass of dodecyl betaine, 5 - 30 parts by mass of polyether-modified polyorganosiloxane 8030F, and 0.5 - 3 parts by mass of silane coupling agent Si-550, and stir for 10 minutes.

5. The 3D printing inorganic binder system based on infrared heating hardening according to claim 1, wherein: The preparation method of the reinforcing agent includes the following steps: (1) Mix 30 - 60 parts by mass of potassium hydroxide with water and stir for 10 minutes; (2) After cooling to 30 °C, add 5 - 15 parts by mass of tetramethyl decynediol, 0.5 - 3 parts by mass of silane coupling agent Si-550, 2 - 8 parts by mass of polyether-modified polyorganosiloxane 8030F, and 2 - 8 parts by mass of titanium trichloride - alkyl aluminum; (3) Stir for 10 minutes to obtain the reinforcing agent.

6. The 3D printing inorganic binder system based on infrared heating hardening according to claim 1, wherein: The viscosity of the inorganic binder ≤ 20 mPa·S, and the neutralization degree ≤ 35 Nm / %; The viscosity of the reinforcing agent ≤ 12 mPa·S, and the neutralization degree ≤ 35 Nm / %; 7. The 3D printing inorganic binder system based on infrared heating hardening according to claim 4, wherein: In the preparation method of the inorganic binder, the addition amount of potassium hydroxide in step (1) is 1% - 5% of the mass of potassium silicate.

8. The 3D printing inorganic binder system based on infrared heating hardening according to claim 5, characterized in that: In the preparation method of the reinforcing agent, the addition amount of water in step (1) is 10% - 30% of the mass of potassium hydroxide.

9. A method for making a sand mold of a 3D printing inorganic binder system based on infrared heating hardening as described in claim 1, characterized in that: It includes the following steps: (1) Premix 2 - 8 parts by mass of the reinforcing agent with 100 parts of silica sand; (2) Spread the premixed sand on the printing platform through a sand spreading device; (3) Spray 5 - 30 parts by mass of the inorganic binder in the set area using a 3D printing nozzle; (4) Cure layer by layer at 60 - 80 °C using an infrared heating device; (5) Repeat steps (2) - (4) to complete sand mold printing, and finally remove the loose sand to obtain the formed sand mold.

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