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

Abstract

The present invention discloses a 3D printing inorganic binder system and a sand mold making method based on infrared heating hardening, and specifically relates to the field of casting 3D printing technology. A 3D printing inorganic binder system based on infrared heating hardening, the system consists of two independent liquids: an inorganic binder and a reinforcing agent. A sand mold making method based on the 3D printing inorganic binder system of claim 1, comprising the following steps: (1) premixing the reinforcing agent with silica sand; (2) spreading the premixed sand on the printing platform by a sand spreader; (3) spraying the inorganic binder on a set area using a 3D printing nozzle; (4) curing layer by layer by an infrared heating device; (5) repeating steps (2)-(4) to complete the sand mold printing, and finally removing the floating sand to obtain a molded sand mold. The present invention improves the adaptability of the sand mold manufacturing process, optimizes the interlayer bonding performance of the sand mold, enhances the structural stability of the sand mold, improves the molding quality of the casting, improves the dimensional control accuracy, and meets the requirements of precision casting.

Description

Technical Field

[0001] The present invention belongs to the field of casting 3D printing technology, and specifically 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, inkjet 3D printing technology has been widely introduced into the field of sand mold / sand core manufacturing due to its mold-free and rapid prototyping characteristics for complex structures. This technology significantly improves the flexibility of sand mold design and manufacturing efficiency by spraying binders layer by layer and selectively curing the sand layers. However, existing processes mostly rely on organic resin binders. Although they can meet the strength requirements of sand molds, they have environmental and performance defects such as high volatile organic compound (VOCs) emissions and easy carbonization at high temperatures. For this reason, inorganic binders represented by silicates, phosphates, and geopolymers have become a research hotspot. They have significant advantages such as no VOCs emissions, excellent high-temperature stability, and low raw material costs. However, their industrial application is still subject to the following key technical bottlenecks:

[0003] 1. Insufficient initial strength and weak interface bonding: The curing mechanism of inorganic binders relies on physical hydration and dehydration or slow chemical cross-linking, resulting in the initial sand mold strength being difficult to meet the requirements of demolding and handling. At the same time, the binder has low efficiency in interacting with the hydroxyl groups on the surface of the sand particles, and the interface chemical bonding density is insufficient, which restricts the overall mechanical properties.

[0004] 2. High risk of interlayer bonding failure: The layer-by-layer deposition process of inkjet printing requires the binder to achieve cross-layer penetration and chemical crosslinking within a short period of time. However, traditional inorganic binders have low diffusion coefficients and slow gelation rates, which can easily lead to the formation of weak interfacial layers in the interlayer transition zone, causing delamination defects.

[0005] 3. Poor environmental adaptability: The water-based inorganic binder system is prone to colloid softening or ionic bond breaking after absorbing moisture, resulting in the sand mold strength decaying by more than 40% within 24 hours in an environment with humidity ≥50%, which seriously limits its storage cycle and application in complex environments.

[0006] Existing technologies improve performance by adding reinforcing phases such as nano-silica particles and chopped carbon fibers or optimizing printing parameters (such as jet frequency and droplet spacing). However, they face the risk of nozzle clogging (a volume fraction of nanoparticles ≥5% may cause nozzle clogging with a nozzle diameter of Φ50 μm) or increased process complexity. Although high-temperature post-treatment processes (such as heating at >200°C for 2 hours) can improve strength, they lead to an increase in energy consumption costs of more than 30%, which goes against the original intention of green manufacturing.

[0007] Therefore, it is urgent to develop an inorganic binder system based on a multi-component synergistic enhancement mechanism, which can simultaneously solve the contradictions among printing adaptability, mechanical properties and environmental stability through interfacial chemical modification and curing kinetics regulation, and provide a sand mold manufacturing solution for green casting that has both efficient molding and excellent comprehensive performance. Summary of the Invention

[0008] The purpose of the present invention is to provide a 3D printing inorganic binder system based on infrared heating hardening and a preparation method thereof.

[0009] In order to achieve the above object, the present invention provides the following technical solutions:

[0010] An inorganic binder system for 3D printing based on infrared heating curing, which consists of two independent liquids: an inorganic binder and a reinforcing agent;

[0011] The inorganic binder comprises the following raw materials in parts by weight: 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;

[0012] The reinforcing agent comprises the following raw materials in parts by mass: 30-60 parts of potassium hydroxide, 5-15 parts of tetramethyldecynediol, 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-alkylaluminum.

[0013] Furthermore, the sodium silicate in the inorganic binder is a water glass solution with a modulus of 2.5 and a Baume degree of 40 degrees; the potassium silicate is a water glass solution with a modulus of 2.3 and a Baume degree of 35 degrees; the purity of the sodium hexametaphosphate is 98%; and the active ingredient of the lauryl betaine is 99%.

[0014] Furthermore, the purity of potassium hydroxide in the reinforcing agent is 98%; the active ingredient of the tetramethyldecynediol is 99%; and the active ingredient of the silane coupling agent Si-550 is 99%.

[0015] Further, the preparation of the inorganic binder comprises the following steps:

[0016] (1) Mix 40-70 parts by mass of sodium silicate, 5-20 parts by mass of potassium silicate and potassium hydroxide and stir for 10 minutes;

[0017] (2) After heating to 60°C, add 2-10 parts by weight of sodium hexametaphosphate and continue stirring for 20 minutes;

[0018] (3) After cooling to 30°C, add 0.5-3 parts by mass of dodecyl betaine, 5-30 parts by mass of polyether-modified polysiloxane 8030F, and 0.5-3 parts by mass of silane coupling agent Si-550, and stir for 10 minutes.

[0019] Furthermore, the preparation method of the reinforcing agent comprises the following steps:

[0020] (1) Mix 30-60 parts by mass of potassium hydroxide and water and stir for 10 minutes;

[0021] (2) After cooling to 30°C, add 5-15 parts by mass of tetramethyldecynediol, 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-alkylaluminum;

[0022] (3) After stirring for 10 minutes, the reinforcing agent is obtained.

[0023] Furthermore, the viscosity of the inorganic binder is ≤20 mPa·S, and the degree of neutralization is ≤35 Nm / %; the viscosity of the reinforcing agent is ≤12 mPa·S, and the degree of neutralization is ≤35 Nm / %.

[0024] Furthermore, in the method for preparing the inorganic binder, the amount of potassium hydroxide added in step (1) is 1%-5% of the mass of potassium silicate.

[0025] Furthermore, in the reinforcing agent preparation method, the amount of water added in step (1) is 10%-30% of the mass of potassium hydroxide.

[0026] A method for preparing sand molds for 3D printing using an inorganic binder system based on infrared heating hardening comprises the following steps:

[0027] (1) Premix 2-8 parts by mass of reinforcing agent with 100 parts by mass of silica sand;

[0028] (2) Spread the premixed sand on the printing platform through the sand spreader;

[0029] (3) Using a 3D printing nozzle to spray 5-30 parts by weight of an inorganic binder on a set area;

[0030] (4) Curing layer by layer at 60-80°C by infrared heating device;

[0031] (5) Repeat steps (2) to (4) to complete the sand mold printing, and finally remove the loose sand to obtain the molded sand mold.

[0032] Beneficial effects of the present invention:

[0033] 1. Improve the adaptability of sand mold manufacturing process: Through the synergistic effect of a specific ratio of sodium silicate / potassium water glass system and reinforcing agent, the low viscosity characteristics of the binder viscosity ≤ 20mPa·s and the reinforcing agent viscosity ≤ 12mPa·s are achieved. This meets the slurry fluidity requirements of 3D printing nozzles and adapts to the continuous molding needs of complex sand mold structures.

[0034] 2. Optimize the bonding performance between sand mold layers: 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-linking bonds under microwave heating conditions, promoting the formation of chemical bonds between layers and effectively eliminating the printing delamination phenomenon.

[0035] 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 tetramethyldecynediol in the reinforcing agent, a three-dimensional network cross-linked structure is formed, which increases the compressive strength of the sand mold by more than 40% and reduces the moisture sensitivity to ≤35Nm / %.

[0036] 4. Improve the molding quality of castings: The amount of gas generated during the curing process of the inorganic binder system is less than 0.5mL / g (tested at 1100℃), which is more than 60% lower than that of traditional furan resin, effectively reducing the porosity defects of castings and the surface roughness of castings reaches Ra≤6.3μm.

[0037] 5. Improve 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 be ≤0.15%, and the sand mold dimensional accuracy error is ≤±0.3mm / 100mm, meeting the requirements of precision casting. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Figure a is the sand mold size accuracy test result.

[0039] Figure 2 Figure b is the sand mold size accuracy test result.

[0040] Figure 3 This is a comparison of the vertical surfaces of the 3D printed sand mold before and after modification of the inorganic binder system. DETAILED DESCRIPTION

[0041] The preparation method of the present invention will be described in detail below with reference to the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0042] Example of 3D printing inorganic binder based on infrared heating hardening

[0043] Example 1

[0044] (1) Preparation of inorganic binder

[0045] 40 parts of sodium silicate (modulus 2.5, 40 degrees Baume) and 5 parts of potassium silicate (modulus 2.3, 35 degrees Baume) were added to a reaction vessel and stirred for 10 minutes. The mixture was heated to 60°C, and 2 parts of 98% sodium hexametaphosphate were added. Stirring continued for 20 minutes. After the mixture cooled to 30°C, 0.5 parts of 99% active lauryl betaine, 5 parts of 99% active polyether-modified polyorganosiloxane 8030F, and 0.5 parts of silane coupling agent Si-550 were added in sequence. Stirring continued for 10 minutes to complete the preparation of the inorganic binder. The viscosity of the inorganic binder was measured to be 18 mPa·s, and the degree of neutralization was 30 Nm / %.

[0046] (2) Preparation of reinforcing agent

[0047] Mix 30 parts of 98% potassium hydroxide with water in a three-necked flask and stir for 10 minutes. After cooling to 30°C, add 5 parts of 99% active tetramethyldecynediol, 0.5 parts of silane coupling agent Si-550, 2 parts of 99% active polyether-modified polyorganosiloxane 8030F, and 2 parts of titanium trichloride-alkylaluminum. Stir for 10 minutes to obtain a reinforcing agent. The viscosity of the reinforcing agent was measured to be 10 mPa·s, and the degree of neutralization was 30 Nm / %.

[0048] (3) Performance testing

[0049] Premix 2 parts of reinforcing agent with 100 parts of 3D printing silica sand. When 3D printing the sand mold, spray 1.8 parts of inorganic binder as needed after laying the sand. Curing with infrared heating, print the "8" sample layer by layer. Clean the loose sand and remove the sample before conducting performance testing.

[0050] Example 2

[0051] (1) Preparation of inorganic binder

[0052] Place 70 parts of sodium silicate (modulus 2.5, 40 degrees Baume) and 20 parts of potassium silicate (modulus 2.3, 35 degrees Baume) into a reaction vessel and stir for 10 minutes. Heat to 60°C, add 10 parts of 98% sodium hexametaphosphate, and stir for 20 minutes. Cool to 30°C, then add 3 parts of 99% active lauryl betaine, 30 parts of 99% active polyether-modified polyorganosiloxane 8030F, and 3 parts of silane coupling agent Si-550. Stir for 10 minutes to prepare the inorganic binder.

[0053] (2) Preparation of reinforcing agent

[0054] To a three-necked flask, add 60 parts of 98% potassium hydroxide and an appropriate amount of water and stir for 10 minutes. Cool to 30°C, then add 15 parts of 99% active tetramethyldecynediol, 3 parts of silane coupling agent Si-550, 8 parts of 99% active polyether-modified polyorganosiloxane 8030F, and 8 parts of titanium trichloride-alkylaluminum. Stir for 10 minutes to obtain a reinforcing agent.

[0055] (3) Performance testing

[0056] Premix 3 parts reinforcing agent with 100 parts 3D printing silica sand. During the 3D printing sand mold process, after laying the sand, 1.8 parts inorganic binder was sprayed at designated locations. The binder was cured using infrared heating, and eight specimens were constructed layer by layer. After removing the loose sand and removing the specimens, performance testing was performed.

[0057] Example 3

[0058] (1) Preparation of inorganic binder

[0059] Place 50 parts of sodium silicate (modulus 2.5, 40 degrees Baume) and 10 parts of potassium silicate (modulus 2.3, 35 degrees Baume) in a reaction vessel and stir for 10 minutes. Heat to 60°C, add 8 parts of 98% sodium hexametaphosphate, and continue stirring for 20 minutes. After cooling to 30°C, add 2 parts of 99% active lauryl betaine, 10 parts of 99% active polyether-modified polyorganosiloxane 8030F, and 2 parts of silane coupling agent Si-550. Stir for 10 minutes to obtain the inorganic binder.

[0060] (2) Preparation of reinforcing agent

[0061] Mix 40 parts of 98% potassium hydroxide with water in a three-necked flask and stir for 10 minutes. Cool to 30°C, then add 8 parts of 99% active tetramethyldecynediol, 1.5 parts of silane coupling agent Si-550, 4 parts of 99% active polyether-modified polyorganosiloxane 8030F, and 5 parts of titanium trichloride-alkylaluminum. Stir for 10 minutes to prepare a reinforcing agent.

[0062] (3) Performance testing

[0063] Premix 5 parts reinforcing agent with 100 parts 3D printing silica sand. For 3D printing sand molds, spray 1.8 parts inorganic binder at the desired locations after sand laying. Use infrared heating to cure the molds, then print 8 samples layer by layer. Remove loose sand, remove the samples, and conduct performance testing.

[0064] Example 4

[0065] (1) Preparation of inorganic binder

[0066] Add 60 parts of sodium silicate (modulus 2.5, 40 degrees Baume) and 15 parts of potassium silicate (modulus 2.3, 35 degrees Baume) to a reaction vessel and stir for 10 minutes. Heat to 60°C, add 7 parts of 98% sodium hexametaphosphate, and stir for 20 minutes. Once the temperature drops to 30°C, add 1.8 parts of 99% active lauryl betaine, 19 parts of 99% active polyether-modified polyorganosiloxane 8030F, and 1.8 parts of silane coupling agent Si-550. Stir for 10 minutes to complete the preparation of the inorganic binder.

[0067] (2) Preparation of reinforcing agent

[0068] In a three-necked flask, mix 52 parts of 98% potassium hydroxide with water and stir for 10 minutes. Cool to 30°C, then add 11 parts of 99% active tetramethyldecynediol, 2.8 parts of silane coupling agent Si-550, 6.5 parts of 99% active polyether-modified polyorganosiloxane 8030F, and 4.6 parts of titanium trichloride-alkylaluminum. Stir for 10 minutes to obtain a reinforcing agent.

[0069] (3) Performance testing

[0070] Premix 6 parts reinforcing agent with 100 parts 3D printing silica sand. During the 3D printing sand mold process, after laying the sand, spray 1.8 parts inorganic binder at the designated locations. Curing is achieved through infrared heating, and the "8" specimen is formed layer by layer. After removing the loose sand from the surrounding area and removing the specimen, performance testing is performed.

[0071] Example 5

[0072] (1) Preparation of inorganic binder

[0073] Add 42 parts of sodium silicate (modulus 2.5, 40 degrees Baume) and 9 parts of potassium silicate (modulus 2.3, 35 degrees Baume) to a reaction vessel and stir for 10 minutes. Heat to 60°C, add 9 parts of 98% sodium hexametaphosphate, and stir for 20 minutes. Cool to 30°C, add 0.9 parts of 99% active lauryl betaine, 22 parts of 99% active polyether-modified polyorganosiloxane 8030F, and 1.2 parts of silane coupling agent Si-550, and stir for 10 minutes to prepare the inorganic binder.

[0074] (2) Preparation of reinforcing agent

[0075] Place 49 parts of 98% potassium hydroxide and water in a three-necked flask and stir for 10 minutes. Cool to 30°C, then add 14.5 parts of 99% active tetramethyldecynediol, 1.5 parts of silane coupling agent Si-550, 3.9 parts of 99% active polyether-modified polyorganosiloxane 8030F, and 6.6 parts of titanium trichloride-alkylaluminum. Stir for 10 minutes to prepare a reinforcing agent.

[0076] (3) Performance testing

[0077] A premix of 8 parts reinforcing agent and 100 parts 3D printing silica sand was used. During the 3D printing sand mold, after the sand-laying step, 1.8 parts of inorganic binder was sprayed onto the desired printing location. Infrared heating was used to cure the binder, and the "8" sample was printed layer by layer according to the pre-set program. After printing, loose sand was carefully cleaned and the sample was removed for performance testing.

[0078] Table 1: Performance parameters of the examples

[0079]

[0080] Table 2: 3D scanning results of 3D printed sand molds

[0081]

[0082] Comparative Example 1

[0083] (1) Material composition

[0084] Furan resin: The amount added is 1.2% of the mass of silica sand.

[0085] Curing agent: phosphate acidic curing agent, the addition amount is 0.4% of the resin mass;

[0086] (2) Preparation method

[0087] 1. Mix 100 parts of silica sand and 1.2 parts of furan resin in a sand mixer for 3 minutes;

[0088] 2. Add 0.48 parts (0.4% of the resin mass) of curing agent and continue mixing for 5 minutes;

[0089] 3. Use 3D printing equipment to lay sand layer by layer and spray the resin-hardener mixture;

[0090] 4. After 24 hours of self-hardening at room temperature, the test specimens were obtained.

[0091] (3) Performance test results

[0092] 24h tensile strength: 2.0-2.4 MPa; residual strength (compressive): <0.5 MPa (Φ50mm cylinder); gas evolution (1100℃): 11.0 mL / g; sand mold dimensional accuracy ±0.2 mm / 100mm; moisture absorption resistance: strength reduction rate <20% (RH80%, 24h).

[0093] Figure 1 and Figure 2 The results of the sand mold size accuracy test in this embodiment are shown. Figure 3 This is a comparison of the vertical surfaces of 3D printed sand molds before and after modification of the inorganic binder system. The sand mold on the left in the picture was printed before modification and has obvious step marks, which increases the difficulty of surface treatment and affects the processing accuracy of the casting; the sand mold on the right is printed after modification and has good performance.

[0094] Matters not covered by the present invention are known technologies.

[0095] The above embodiments are intended only to illustrate the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made in accordance with the spirit of the present invention are intended to be covered by the scope of protection of the present invention.

Claims

1. A 3D printing inorganic binder system based on infrared heating hardening, characterized in that: The system consists of two separate liquids: an inorganic binder and a reinforcing agent; The inorganic binder comprises the following raw materials in parts by weight: 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 comprises the following raw materials in parts by weight: 30-60 parts of potassium hydroxide, 5-15 parts of tetramethyldecynediol, 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-alkylaluminum; The sodium silicate in the inorganic binder is a water glass solution with a modulus of 2.5 and a Baume degree of 40 degrees; the potassium silicate is a water glass solution with a modulus of 2.3 and a Baume degree of 35 degrees; the purity of the sodium hexametaphosphate is 98%; and the active ingredient of the lauryl betaine is 99%.

2. The 3D printing inorganic binder system based on infrared heating curing according to claim 1, characterized in that: The purity of potassium hydroxide in the reinforcing agent is 98%; the active component of the tetramethyldecynediol is 99%; and the active component of the silane coupling agent Si-550 is 99%.

3. The 3D printing inorganic binder system based on infrared heating curing according to claim 1, characterized in that: The preparation of the inorganic binder comprises the following steps: (1) mixing 40-70 parts by mass of sodium silicate, 5-20 parts by mass of potassium silicate and potassium hydroxide and stirring for 10 minutes; (2) After heating to 60° C., add 2-10 parts by weight of sodium hexametaphosphate and continue stirring for 20 minutes; (3) After cooling to 30° C., 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 were added and stirred for 10 minutes.

4. The 3D printing inorganic binder system based on infrared heating curing according to claim 1, characterized in that: The preparation method of the reinforcing agent comprises the following steps: (1) Mix 30-60 parts by mass of potassium hydroxide and water and stir for 10 minutes; (2) after cooling to 30° C., add 5-15 parts by mass of tetramethyldecynediol, 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-alkylaluminum; (3) After stirring for 10 minutes, the reinforcing agent was obtained.

5. The 3D printing inorganic binder system based on infrared heating curing according to claim 1, characterized in that: The viscosity of the inorganic binder is ≤20mPa·S, and the degree of neutralization is ≤35Nm / %; The viscosity of the reinforcing agent is ≤12 mPa·S, and the degree of neutralization is ≤35 Nm / %.

6. The 3D printing inorganic binder system based on infrared heating curing according to claim 3, characterized in that: In the method for preparing the inorganic binder, the amount of potassium hydroxide added in step (1) is 1%-5% of the mass of potassium silicate.

7. The 3D printing inorganic binder system based on infrared heating curing according to claim 4, characterized in that: In the reinforcing agent preparation method, the amount of water added in step (1) is 10%-30% of the mass of potassium hydroxide.

8. A sand mold manufacturing method for 3D printing based on infrared heating and curing inorganic binder system as claimed in claim 1, characterized in that: The following steps are involved: (1) Premix 2-8 parts by mass of a reinforcing agent with 100 parts by mass of silica sand; (2) Spreading premixed sand on the printing platform through a sand spreader; (3) using a 3D printing nozzle to spray 5-30 parts by weight of an inorganic binder on a set area; (4) curing layer by layer at 60-80°C by infrared heating device; (5) Repeat steps (2)-(4) to complete the sand mold printing, and finally remove the loose sand to obtain the molded sand mold.

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