CN110385395B - Modified precoated sand for selective laser sintering and preparation method thereof - Google Patents
Modified precoated sand for selective laser sintering and preparation method thereof Download PDFInfo
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- CN110385395B CN110385395B CN201910713851.3A CN201910713851A CN110385395B CN 110385395 B CN110385395 B CN 110385395B CN 201910713851 A CN201910713851 A CN 201910713851A CN 110385395 B CN110385395 B CN 110385395B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C1/00—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds
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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
- B33Y70/00—Materials specially adapted for additive manufacturing
Abstract
The invention provides modified precoated sand for selective laser sintering and a preparation method thereof, wherein the precoated sand is prepared by mixing modified two-dimensional TiC, graphene, sand grains, urotropine, phenolic resin and calcium stearate according to the weight ratio of (1-2) to 1-2: 100: 10-15: 1-5: 4-8; pouring the modified two-dimensional TiC, graphene and sand grains into a sand mixer, stirring and heating to 120-140 ℃, adding phenolic resin, mixing sand for 60-100 s, cooling to 110 ℃, adding urotropine aqueous solution and calcium stearate, and stirring the mixed sand for 30s to a sand scattering state. The modified precoated sand prepared by the method has the advantages of environmental protection, short sintering and curing time and high product strength.
Description
Technical Field
The invention relates to the technical field of new materials, in particular to modified precoated sand for selective laser sintering and a preparation method thereof.
Background
The preparation of core boxes and patterns is crucial in sand casting. The traditional preparation method has the advantages of complex process, high cost and long period. Particularly, a plurality of sand molds are often combined for large complex thin-wall castings, and the position and the size of the sand molds are slightly wrong, so that the casting precision is low, the surface quality is poor, the cutting machining amount is large, a large amount of metal materials are wasted, the machining cost is increased, the working efficiency is low, and the economic effect is poor. The selective laser sintering SLS technology belongs to one of 3D printing technologies, has the characteristics of high forming speed, high forming precision, short production period and low economic cost, and the preparation of the sand mold by adopting the SLS technology is a trend of later sand mold casting.
The precoated sand is an important raw material for SLS forming, is a type of molding sand with a resin film coated on sand grains, has the characteristics of high temperature resistance, low expansion, no unshelling and the like, and is one of the best molding materials for complex castings such as automobile cylinders, cylinder covers, intake manifolds, pipe fittings, pump bodies and the like. At present, the precoated sand for SLS forming has the defects of low strength of the obtained sintered product, long curing time and poor environmental protection.
Disclosure of Invention
The invention aims to provide modified precoated sand for selective laser sintering, and the product obtained by SLS sintering has excellent comprehensive mechanical properties.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows: the modified precoated sand for selective laser sintering is prepared by mixing modified two-dimensional TiC, graphene, sand grains, urotropine, phenolic resin and calcium stearate according to the weight ratio of (1-2) to 100 to (10-15) to (1-5) to (4-8);
preferably, the sand grains are silica sand with the grain size of 70-140 microns, and the phenolic resin is formed by mixing PF8121 type thermoplastic phenolic resin and PF8122 type thermoplastic phenolic resin according to the weight ratio of 7: 5.
The invention also aims to provide a preparation method of the modified precoated sand for selective laser sintering, which comprises the steps of mixing and stirring the modified two-dimensional TiC, the graphene and the sand grains, heating to 120-140 ℃, adding the phenolic resin, mixing for 60-100 s, stopping heating, adding the urotropine aqueous solution and the calcium stearate when the temperature is reduced to 110 ℃, mixing and stirring until the materials are in a loose sand state.
Specifically, the modified two-dimensional TiC is prepared by the following steps:
(1) mixing the two-dimensional TiC and the RMgCl solution according to the weight ratio of 2: 1 to form a uniform solution;
(2) adding KH solution into the mixed solution obtained in the step (1), wherein the mass ratio of KH to RMgCl in the solution is 2: 1, and uniformly stirring and mixing;
(3) adding an organosilane coupling agent and bromoethane into the mixed solution obtained in the step (2), wherein the weight ratio of the organosilane coupling agent to the RMgCl to the bromoethane in the solution is 1: 2, and uniformly mixing and stirring;
(4) filtering the mixed solution obtained in the step (3), putting the obtained filter residue into NaOH solution, wherein the mass ratio of the filter residue to the NaOH is 1: 2, and then sequentially filtering, cleaning and drying to obtain the two-dimensional TiC with magnesium ions loaded on the surface;
(5) and (3) carrying out melt blending treatment on nylon, thermoplastic phenolic resin and a silane coupling agent according to the mass ratio of 1: 1, then adding the two-dimensional TiC loaded with magnesium ions on the surface obtained in the step (4), stirring and dispersing for 30min, and then sequentially cooling and crushing the obtained product to obtain the modified two-dimensional TiC with the diameter of 50-100 microns.
Preferably, the concentration of the RMgCl solution in the step (1) is 10-30 mol/L, and the solution temperature is 40-60 ℃.
Preferably, the concentration of the KH solution in the step (2) is 20-40 mol/L, and the solution temperature is 40-60 ℃.
Preferably, the concentration of the NaOH solution in the step (4) is 20-40 mol/L, and the solution temperature is 20-30 ℃.
Preferably, in the step (5), the silane coupling agent is formed by mixing KH550, KH560 and KH570 in equal proportion.
Preferably, the stirring time in the steps (1) and (2) is 30min, and the stirring speed is 20 r/min.
Preferably, the melting temperature in the step (5) is 300 ℃, the blending stirring speed is 20-40 r/min, and the melting blending time is 10 min.
Preferably, the stirring and dispersing treatment time in the step (5) is 30min, and the cooling speed is 10 ℃/min
Compared with the prior art, the invention has the beneficial effects that: the modified precoated sand provided by the invention has the characteristics of environmental protection, short sintering and curing time and high product strength.
Drawings
FIG. 1 is a part formed by selective laser sintering of modified precoated sand
Detailed Description
The present invention will be further described with reference to examples 1 to 3.
Example 1:
the modified precoated sand for selective laser sintering and the preparation method thereof comprise the following steps:
(1) adding two-dimensional TiC into the RMgCl solution, wherein the concentration of the RMgCl solution is 10mol/L, and the temperature is 40 ℃; the weight ratio of the two-dimensional TiC to the RMgCl solution is 2: 1, and then the two-dimensional TiC and the RMgCl solution are stirred and mixed uniformly, wherein the stirring time is 30min, and the rotating speed is 20 r/min;
(2) then, continuously adding KH solution into the RMgCl solution, wherein the concentration of the KH solution is 20mol/L, and the temperature of the solution is 40 ℃; the mass ratio of the KH solution to the RMgCl solution is 2: 1, and then the KH solution and the RMgCl solution are stirred and mixed uniformly, wherein the stirring time is 30min, and the rotating speed is 20 r/min;
(3) continuously adding an organosilane coupling agent and bromoethane, wherein the weight ratio of the organosilane coupling agent to the RMgCl solution is 1: 2, and the weight ratio of the bromoethane to the RMgCl solution is 1: 2, and then stirring and mixing uniformly, wherein the stirring time is 10min, and the rotating speed is 20 r/min;
(4) then filtering the obtained solution, and putting the obtained filter residue into a NaOH solution, wherein the concentration of the NaOH solution is 20mol/L, and the temperature of the solution is 20 ℃; the mass ratio of the filter residue to NaOH is 1: 2, the filter residue and NaOH are placed for 20min, then filtration is carried out, and the filter residue is cleaned by clear water and dried to obtain two-dimensional TiC with magnesium ions loaded on the surface;
(5) carrying out melt blending treatment on nylon, thermoplastic phenolic resin and a silane coupling agent, wherein the silane coupling agent is formed by mixing KH550, KH560 and KH570 in a mass ratio of 1: 1, the melting temperature is 300 ℃, the blending stirring speed is 30r/min, the melt blending time is 10min, then adding the two-dimensional TiC loaded with magnesium ions on the surface obtained in the step (4), carrying out stirring dispersion treatment for 30min, then cooling the obtained product at the cooling speed of 10 ℃/min, and then carrying out crushing treatment to obtain the modified two-dimensional TiC with the diameter of 50-100 mu m;
(6) pouring the modified two-dimensional TiC, the graphene and the silica sand (the particle size ranges from 70-140 microns) into a sand mixer, stirring and heating to 130 ℃, and then adding phenolic resin, wherein the phenolic resin is formed by mixing two series of PF8121 and PF8122, and the weight ratio is 7: 5; mixing sand for 80s, cooling to 110 ℃, adding urotropine aqueous solution and calcium stearate, and stirring the mixed sand for 30s to a sand scattering state; the coating consists of modified two-dimensional TiC, graphene, sand grains, a resin curing agent urotropine, phenolic resin for adjusting the thermal stability and collapsibility of the coated sand and calcium stearate, wherein the weight ratio of the modified two-dimensional TiC to the phenolic resin to the collapsibility of the coated sand is 1: 100: 13: 3: 6.
Example 2:
(1) adding two-dimensional TiC into the RMgCl solution, wherein the concentration of the RMgCl solution is 25mol/L, and the temperature is 55 ℃; the weight ratio of the two-dimensional TiC to the RMgCl solution is 2: 1, and then the two-dimensional TiC and the RMgCl solution are stirred and mixed uniformly, wherein the stirring time is 30min, and the rotating speed is 20 r/min;
(2) then, continuously adding KH solution into RMgCl solution, wherein the concentration of KH solution is 30mol/L, and the temperature of the solution is 50 ℃; the mass ratio of the KH solution to the RMgCl solution is 2: 1, and then the KH solution and the RMgCl solution are stirred and mixed uniformly, wherein the stirring time is 30min, and the rotating speed is 20 r/min;
(3) continuously adding an organosilane coupling agent and bromoethane, wherein the weight ratio of the organosilane coupling agent to the RMgCl solution is 1: 2, and the weight ratio of the bromoethane to the RMgCl solution is 1: 2, and then stirring and mixing uniformly, wherein the stirring time is 10min, and the rotating speed is 20 r/min;
(4) then filtering the obtained solution, and putting the obtained filter residue into a NaOH solution, wherein the concentration of the NaOH solution is 25mol/L, and the temperature of the solution is 20 ℃; the mass ratio of the filter residue to NaOH is 1: 2, the filter residue and NaOH are placed for 20min, then filtration is carried out, and the filter residue is cleaned by clear water and dried to obtain two-dimensional TiC with magnesium ions loaded on the surface;
(5) carrying out melt blending treatment on nylon, thermoplastic phenolic resin and a silane coupling agent, wherein the silane coupling agent is formed by mixing KH550, KH560 and KH570 in a mass ratio of 1: 1, the melting temperature is 300 ℃, the blending stirring speed is 20r/min, the melt blending time is 10min, then adding the two-dimensional TiC loaded with magnesium ions on the surface obtained in the step (4), carrying out stirring dispersion treatment for 30min, then cooling the obtained product at the cooling speed of 10 ℃/min, and then carrying out crushing treatment to obtain the modified two-dimensional TiC with the diameter of 50-100 mu m;
(6) pouring the modified two-dimensional TiC, the graphene and the silica sand (the particle size ranges from 70-140 microns) into a sand mixer, stirring and heating to 130 ℃, and then adding phenolic resin, wherein the phenolic resin is formed by mixing two series of PF8121 and PF8122, and the weight ratio is 7: 5; and (3) mixing sand for 80s, cooling to 110 ℃, adding the urotropine aqueous solution and calcium stearate, and stirring the mixed sand for 30s to a sand scattering state. The coating consists of modified two-dimensional TiC, graphene, sand grains, a resin curing agent urotropine, phenolic resin for adjusting the thermal stability and collapsibility of the coated sand and calcium stearate, wherein the weight ratio of the modified two-dimensional TiC to the phenolic resin to the collapsibility of the coated sand is 1: 100: 13: 3: 6.
Example 3:
(1) adding two-dimensional TiC into the RMgCl solution, wherein the concentration of the RMgCl solution is 20mol/L, and the temperature is 55 ℃; the weight ratio of the two-dimensional TiC to the RMgCl solution is 2: 1, and then the two-dimensional TiC and the RMgCl solution are stirred and mixed uniformly, wherein the stirring time is 30min, and the rotating speed is 20 r/min;
(2) then, continuously adding KH solution into RMgCl solution, wherein the concentration of KH solution is 30mol/L, and the temperature of the solution is 50 ℃; the mass ratio of the KH solution to the RMgCl solution is 2: 1, and then the KH solution and the RMgCl solution are stirred and mixed uniformly, wherein the stirring time is 30min, and the rotating speed is 20 r/min;
(3) continuously adding an organosilane coupling agent and bromoethane, wherein the weight ratio of the organosilane coupling agent to the RMgCl solution is 1: 2, and the weight ratio of the bromoethane to the RMgCl solution is 1: 2, and then stirring and mixing uniformly, wherein the stirring time is 10min, and the rotating speed is 20 r/min;
(4) then filtering the obtained solution, and putting the obtained filter residue into a NaOH solution, wherein the concentration of the NaOH solution is 20mol/L, and the temperature of the solution is 20 ℃; the mass ratio of the filter residue to NaOH is 1: 2, the filter residue and NaOH are placed for 20min, then filtration is carried out, and the filter residue is cleaned by clear water and dried to obtain two-dimensional TiC with magnesium ions loaded on the surface;
(5) carrying out melt blending treatment on nylon, thermoplastic phenolic resin and a silane coupling agent, wherein the silane coupling agent is formed by mixing KH550, KH560 and KH570 in a mass ratio of 1: 1, the melting temperature is 300 ℃, the blending stirring speed is 20r/min, the melt blending time is 10min, then adding the two-dimensional TiC loaded with magnesium ions on the surface obtained in the step (4), carrying out stirring dispersion treatment for 30min, then cooling the obtained product at the cooling speed of 10 ℃/min, and then carrying out crushing treatment to obtain the modified two-dimensional TiC with the diameter of 50-100 mu m;
(6) pouring the modified two-dimensional TiC, the graphene and the silica sand (the particle size ranges from 70-140 microns) into a sand mixer, stirring and heating to 130 ℃, and then adding phenolic resin, wherein the phenolic resin is formed by mixing two series of PF8121 and PF8122, and the weight ratio is 7: 5; mixing sand for 80s, cooling to 110 ℃, adding urotropine aqueous solution and calcium stearate, and stirring the mixed sand for 30s to a sand scattering state; the coating consists of modified two-dimensional TiC, graphene, sand grains, a resin curing agent urotropine, phenolic resin for adjusting the thermal stability and collapsibility of the coated sand and calcium stearate, wherein the weight ratio of the modified two-dimensional TiC to the phenolic resin to the collapsibility of the coated sand is 1: 100: 13: 3: 6.
Claims (1)
1. The modified precoated sand for selective laser sintering is characterized by being prepared by mixing modified two-dimensional TiC, graphene, sand grains, urotropine, phenolic resin and calcium stearate according to the weight ratio of 1-2: 100: 10-15: 1-5: 4-8;
the sand grains are silica sand with the grain size of 70-140 microns, and the phenolic resin is formed by mixing PF8121 type thermoplastic phenolic resin and PF8122 type thermoplastic phenolic resin according to the weight ratio of 7: 5;
the modified two-dimensional TiC is prepared by the following steps:
(1) mixing the two-dimensional TiC and the RMgCl solution according to the weight ratio of 2: 1 to form a uniform solution;
(2) adding KH solution into the mixed solution obtained in the step (1), wherein the mass ratio of KH to RMgCl in the solution is 2: 1, and uniformly stirring and mixing;
(3) adding an organosilane coupling agent and bromoethane into the mixed solution obtained in the step (2), wherein the weight ratio of the organosilane coupling agent to the RMgCl to the bromoethane in the solution is 1: 2, and uniformly mixing and stirring;
(4) filtering the mixed solution obtained in the step (3), putting the obtained filter residue into NaOH solution, wherein the mass ratio of the filter residue to the NaOH is 1: 2, and then sequentially filtering, cleaning and drying to obtain the two-dimensional TiC with magnesium ions loaded on the surface;
(5) carrying out melt blending treatment on nylon, thermoplastic phenolic resin and a silane coupling agent according to the mass ratio of 1: 1, then adding the two-dimensional TiC loaded with magnesium ions on the surface obtained in the step (4), stirring and dispersing for 30min, and then sequentially cooling and crushing the obtained product to obtain modified two-dimensional TiC with the diameter of 50-100 mu m;
the concentration of the RMgCl solution in the step (1) is 10-30 mol/L, and the temperature of the solution is 40-60 ℃;
the concentration of the KH solution in the step (2) is 20-40 mol/L, and the temperature of the solution is 40-60 ℃;
the concentration of the NaOH solution in the step (4) is 20-40 mol/L, and the temperature of the solution is 20-30 ℃;
the silane coupling agent in the step (5) is prepared by mixing KH550, KH560 and KH570 in equal proportion;
the stirring time in the steps (1) and (2) is 30min, and the stirring speed is 20 r/min;
the melting temperature in the step (5) is 300 ℃, the blending stirring speed is 20-40 r/min, and the melting blending time is 10 min; the stirring dispersion treatment time in the step (5) is 30min, and the cooling speed is 10 ℃/min;
the preparation method of the modified precoated sand for selective laser sintering comprises the following steps of mixing and stirring modified two-dimensional TiC, graphene and sand grains, heating to 120-140 ℃, adding phenolic resin, mixing for 60-100 s, stopping heating, adding urotropine aqueous solution and calcium stearate when the temperature is reduced to 110 ℃, mixing and stirring until the materials are in a sand scattering state.
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