CN112453314B - Curing agent for inorganic phosphate binder precoated sand and application thereof - Google Patents
Curing agent for inorganic phosphate binder precoated sand and application thereof Download PDFInfo
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- CN112453314B CN112453314B CN202011376890.8A CN202011376890A CN112453314B CN 112453314 B CN112453314 B CN 112453314B CN 202011376890 A CN202011376890 A CN 202011376890A CN 112453314 B CN112453314 B CN 112453314B
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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
- B22C1/16—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents
- B22C1/18—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents of inorganic agents
- B22C1/185—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents of inorganic agents containing phosphates, phosphoric acids or its derivatives
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C9/00—Moulds or cores; Moulding processes
- B22C9/02—Sand moulds or like moulds for shaped castings
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Abstract
The invention discloses a curing agent for inorganic phosphate binder precoated sand, which comprises the following components: coupling agent: 2-6 parts; phosphate binder: 25-40 parts; organic weak acid aqueous solution: 2-6 parts; crystalline hydrate: 25-30 parts of a solvent; coating magnesite powder with PVP: 30-50 parts. According to the curing agent for the inorganic phosphate binder precoated sand, the inorganic phosphate binder and the crystal hydrate are attached to the surface of sand grains, hot air is introduced to dry the binder, the crystal hydrate is wrapped in the binder, and the dry precoated sand is obtained and has excellent fluidity, after sand shooting, the hydrate is decomposed into water molecules by heating a mould, the binder is wetted, the sand grains are mutually bonded and molded, and then the sand grains are rapidly cured to form strength.
Description
Technical Field
The invention relates to the technical field of casting of phosphate binder molding sand, in particular to a curing agent for inorganic phosphate binder precoated sand and application thereof.
Background
With the increasingly strict environmental supervision, people are aroused by environmental awareness and cannot neglect the environmental pollution problem caused by the traditional organic resin coated sand, but the traditional inorganic binder has no ideal effect in practical application due to various problems of low molding strength, poor collapsibility of molding sand and the like. It is urgent to find a new inorganic binder capable of replacing the conventional organic resin sand.
The phosphate binder is a green environment-friendly casting binder, has the advantages of low curing temperature, good heat resistance, small gas evolution, good high-temperature collapsibility, good reusability, simple process, low cost and the like, and is a molding material with application value and application prospect. The curing mode of the phosphate binder sand at present mainly comprises heating hardening and self hardening of a reinforcing agent or air blowing auxiliary hardening, and because the binder and the auxiliary material are added into the two types of inorganic resin molding sand during use, the binder and the auxiliary material are both liquid components, and the fluidity of the sand can be influenced after the binder and the auxiliary material are added into the sand, the complex sand core corners can not be completely filled during core shooting.
Disclosure of Invention
The invention aims to provide a curing agent for inorganic phosphate binder precoated sand, which is used for obtaining dry precoated sand with good moisture absorption resistance after standard sand and the curing agent for the inorganic phosphate binder precoated sand are mixed, and when the dry precoated sand is used, not only is good fluidity required during core molding and core making, but also the dry precoated sand can be quickly wetted by water under heating condition, and then the dry precoated sand is quickly cured under heating condition to have strength, so that the fluidity of the sand is improved, and the storage stability (no moisture absorption) of the precoated sand can be improved.
The invention also aims to provide an application of the curing agent for inorganic phosphate binder precoated sand in preparation of casting sand molds, and the scheme adopted for solving the problems of poor fluidity and low strength after curing of the current phosphate wet sand is that: a curing agent for inorganic phosphate binder precoated sand comprises the following components:
coupling agent: 2-6 parts;
phosphate binder: 25-40 parts;
organic weak acid aqueous solution: 2-6 parts;
crystalline hydrate: 25-30 parts of a solvent;
coating magnesite powder with PVP: 30-50 parts.
According to the formula of the coupling agent and the PVP coated magnesite powder, on one hand, moisture absorption during storage of the coated sand is prevented, and on the other hand, water loss is caused during heating and curing of the crystalline hydrate, so that the PVP coated magnesite powder is dissolved to promote the curing speed and strength during molding of the coated sand.
More preferably, the phosphate binder is diethylenetriamine pentaacetic acid modified phosphate binder, and comprises the following raw materials in parts by weight:
industrial phosphoric acid: 50.92 parts;
aluminum hydroxide powder: 11.68 parts;
silicic acid: 0.3 part;
boric acid: 1.81 parts;
magnesium oxide: 1.21 parts;
citric acid: 0.3 part
Copper oxide: 0.9 part;
zinc oxide: 0.9 part;
yttrium oxide: 0.04 parts;
DTPA: 1.81 parts
Water: 30.13 parts.
According to the phosphate modified binder formula, silicic acid can form silicic acid gel, the binder can be prevented from being dehydrated prematurely when the surface of a mold with higher temperature is heated, the binder close to the surface of the mold can be wetted fully, water released by aluminum sulfate in molding sand on the surface of the hot mold is prevented from losing prematurely, the binder in the molding sand cannot be wetted fully, diethylenetriaminepentaacetic acid is an organic acid, has hygroscopicity, has a complexing effect with metal ions, and can be matched with silicic acid to play a certain role in retaining water when coated sand is heated, so that the surface of a sand mold has better surface safety.
More preferably, the coupling agent is a silane coupling agent: KH 550. The coupling agent is alkaline, so that dehydration can be accelerated during preparation of the precoated sand, dry precoated sand can be obtained quickly, the moisture absorption resisting effect is achieved during storage of the precoated sand, the coupling agent can be hydrolyzed again due to moisture release of crystalline hydrate during application of the precoated sand, curing of the binder is accelerated, and the coupling agent plays a role in resisting moisture absorption in a cured product due to the fact that curing is carried out at a high temperature.
Preferably, the organic weak acid aqueous solution is a citric acid aqueous solution with a mass ratio of 1: 2.
Preferably, the crystalline hydrate is aluminum sulfate octadecahydrate
In the precoated sand formula, the aluminum sulfate has the function of releasing crystal water to re-dissolve the solid binder so as to bond sand grains.
Preferably, the PVP coated magnesite powder is fused magnesite powder, and the granularity of the fused magnesite powder is 800-1000 meshes. The formulation magnesite according to the invention has the functions of moisture absorption and solidification after being mixed with a liquid phosphate binder, the moisture absorption characteristic of the formulation magnesite is skillfully applied to prevent moisture absorption of a dry precoated sand binder, the reactivity of the magnesite is influenced to a certain extent after excessive moisture absorption, PVP is adopted for coating treatment, the PVP is also water-soluble and can absorb water and is coated on the surface of the magnesite so as to weaken the moisture absorption of the magnesite, in addition, the magnesite is reacted with the binder and is not required to be used when the phosphate binder precoated sand is prepared, however, the magnesite is added after the binder is dried, the reaction with the solid binder is avoided, the PVP is used for coating the magnesite, the contact between the magnesite and the binder is isolated, after the dry precoated sand is prepared, the precoated sand is used and meets a hot mold, the PVP is dissolved due to the water discharging effect of a hydrate, the magnesia is exposed, and at the moment, the magnesia can react with the binder which is melted at the same time, so the magnesia also plays the role of a curing agent, and all the effects are good,
the second scheme adopted by the invention for achieving the purpose is as follows: the application of the curing agent for inorganic phosphate binder precoated sand in the preparation of casting sand molds comprises the following steps: mixing standard sand with a coupling agent accounting for 0.2-0.6% of the standard sand by mass to obtain mixed sand, then, phosphate binder accounting for 2.5 to 4.0 percent of the standard sand by mass, organic weak acid aqueous solution accounting for 0.2 to 0.6 percent of the standard sand by mass and crystal hydrate accounting for 2.5 to 3.5 percent of the standard sand by mass are mixed uniformly in advance, then adding the mixed sand to continue mixing, finally crushing, drying and dehydrating under the condition of introducing hot air until no obvious agglomeration exists to obtain dry precoated sand, the temperature of the hot air is lower than the water loss temperature of the crystalline hydrate, PVP (polyvinyl pyrrolidone) coated magnesia powder accounting for 3-5% of the standard sand mass percent is added after screening the dry coated sand, the finished coated sand is obtained after uniform mixing, a core shooter is utilized to spray the finished coated sand into a mould, and heating for curing, and then demoulding, wherein the heating temperature is 150-170 ℃ higher than the water loss temperature of the crystalline hydrate.
Preferably, the temperature of the hot air is 40-50 ℃.
When the curing agent for inorganic phosphate binder precoated sand is used, the inorganic phosphate binder and the crystal hydrate are attached to the surface of sand grains, hot air is introduced to dry the binder, the crystal hydrate is uniformly coated in the binder to obtain dry precoated sand, and meanwhile, the magnesium sand powder coated by PVP is added, so that the effects of increasing sand grain lubrication and accelerating sand mould curing are achieved.
When the curing agent for inorganic phosphate binder precoated sand is used, the obtained dry precoated sand is screened to obtain precoated sand with uniform granularity. When the sand-blasting and filling mould is used, the inorganic phosphate binder in the dry precoated sand and the water in the auxiliary materials are removed before use, so that the whole precoated sand is completely dry, the fluidity of the sand is greatly improved, and the sand-blasting and filling are facilitated to obtain a compact sand core; the crystal hydrate coated in the phosphate binder decomposes water under the heating condition of a mould, so that the phosphate binder and the PVP coated magnesia are wetted, the sand grains are mutually adhered together, and the phosphate binder and the magnesia react and dehydrate to quickly solidify and form the sand core.
Detailed Description
The following examples are provided to further illustrate the present invention for better understanding, but the present invention is not limited to the following examples.
A curing agent for inorganic phosphate binder precoated sand comprises the following components:
coupling agent: 2-6 g;
phosphate binder: 25-40 g;
organic weak acid aqueous solution: 2-6 g;
crystalline hydrate: 25-30 g;
coating magnesite powder with PVP: 30-50 g.
Coupling agents used include: silanes, titanates, aluminates, organochromosomes, borides, phosphates, zirconates, stannates, etc. The crystalline hydrate is a solid compound containing a certain amount of water molecules at normal temperature. The application can use phosphate binder commonly used in the field, and the chemical components are as follows: 50.92% of industrial phosphoric acid, 11.68% of aluminum hydroxide powder, 1.81% of boric acid, 1.21% of magnesium oxide, 0.9% of zinc oxide, 0.9% of copper oxide and 0.9% of yttrium oxide. Preferably, in order to facilitate demolding after the precoated sand is cured, 1.81 percent of DTPA (diethylenetriaminepentaacetic acid), 0.3 percent of citric acid and 0.3 percent of silicic acid are added into the phosphate binder to obtain the phosphate modified binder. The PVP used was polyvinylpyrrolidone.
Example 1
1. Weighing 1000g of standard sand and 2g of silane coupling agent for later use;
2. adding standard sand and a silane coupling agent into a stirrer, and stirring for 90 seconds;
3. weighing and uniformly mixing 25g of phosphate binder, 2g of citric acid aqueous solution with the mass ratio of 1:2 and 25g of aluminum sulfate octadecahydrate, and adding the mixture into the sand prepared in the step 2 to continuously mix the sand for 120 s;
4. placing the wet sand prepared in the step 3 in a hot air stirrer, introducing hot air of 40 ℃ while stirring, preparing dry precoated sand when sand grains are uniformly dispersed in the stirrer and obviously not agglomerated, and carrying out screening and then carrying out sealed storage for later use;
5. adding 30g of PVP coated magnesia powder mixed sand into the dry precoated sand for 30S,
6. shooting sand by using a core shooter, wherein the temperature of a mould is 130 ℃, the heating time of the mould is 3min, and curing and molding are carried out;
7. and opening the die, taking out the sample, and measuring the tensile strength of the sample when the sample is cooled to room temperature.
Example 2
1. Weighing 1000g of standard sand and 2g of silane coupling agent for later use;
2. adding standard sand and a silane coupling agent into a stirrer, and stirring for 90 seconds;
3. weighing and uniformly mixing 30g of phosphate binder, 4g of citric acid aqueous solution with the mass ratio of 1:2 and 30g of aluminum sulfate octadecahydrate, and adding the mixture into the sand prepared in the step 2 for continuously mixing the sand for 120 s;
4. placing the wet sand prepared in the step 3 in a hot air stirrer, introducing hot air at 45 ℃ while stirring, preparing dry precoated sand when sand grains are uniformly dispersed in the stirrer and obviously not agglomerated, and carrying out screening and then carrying out sealed storage for later use;
5. adding 40g of PVP (polyvinyl pyrrolidone) -coated magnesia powder into the dry precoated sand, mixing the sand for 30 seconds, then shooting the sand by using a core shooter, heating the mould for 2min at the temperature of 150 ℃, and curing and forming;
6. and opening the die, taking out the sample, and measuring the tensile strength of the sample when the sample is cooled to room temperature.
Example 3
1. Weighing 1000g of standard sand and 4g of silane coupling agent for later use;
2. adding standard sand and a silane coupling agent into a stirrer, and stirring for 90 seconds;
3. weighing and uniformly mixing 35g of phosphate binder, 6g of citric acid aqueous solution and 30g of aluminum sulfate octadecahydrate in a mass ratio of 1:2, and adding the mixture into the sand prepared in the step 2 for continuously mixing the sand for 120 s;
4. placing the wet sand prepared in the step 3 in a hot air stirrer, introducing hot air at 45 ℃ while stirring, preparing dry precoated sand when sand grains are uniformly dispersed in the stirrer and obviously not agglomerated, and carrying out screening and then carrying out sealed storage for later use;
5. adding 50g of PVP (polyvinyl pyrrolidone) -coated magnesia powder into the dry precoated sand, mixing the sand for 30 seconds, then shooting the sand by using a core shooter, heating the mould for 2min at the temperature of 150 ℃, and curing and forming;
6. and opening the die, taking out the sample, and measuring the tensile strength of the sample when the sample is cooled to room temperature.
Example 4
1. Weighing 1000g of standard sand and 6g of silane coupling agent for later use;
2. adding standard sand and a silane coupling agent into a stirrer, and stirring for 90 seconds;
3. weighing and uniformly mixing 40g of phosphate binder, 6g of citric acid aqueous solution and 35g of aluminum sulfate octadecahydrate in a mass ratio of 1:2, adding the mixture into the sand prepared in the step 2, and continuously mixing the mixture for 120 s;
4. placing the wet sand prepared in the step 3 in a hot air stirrer, introducing hot air at 50 ℃ while stirring, preparing dry precoated sand when sand grains are uniformly dispersed in the stirrer and obviously not agglomerated, and carrying out screening and then carrying out sealed storage for later use;
5. adding 45g of PVP (polyvinyl pyrrolidone) -coated magnesia powder into the dry precoated sand, mixing the sand for 30 seconds, then shooting the sand by using a core shooter, wherein the temperature of a mould is 170 ℃, the heating time of the mould is 1.5min, and curing and forming;
6. and opening the die, taking out the sample, and measuring the tensile strength of the sample when the sample is cooled to room temperature.
Comparative example
1. Weighing 1000g of standard sand and 4g of silane coupling agent for later use;
2. adding standard sand and a silane coupling agent into a stirrer, and stirring for 90 seconds;
3. weighing and uniformly mixing 30g of phosphate binder and 6g of citric acid aqueous solution according to the mass ratio of 1:2, and adding the mixture into the sand prepared in the step 2 for continuously mixing the sand for 120 s;
4. shooting the green sand prepared in the step 3 by using a core shooter, wherein the temperature of a mould is 150 ℃, the heating time of the mould is 4min, and curing and forming;
6. and opening the die, taking out the sample, and measuring the tensile strength of the sample when the sample is cooled to room temperature.
The experimental test results are as follows:
the molding sand prepared in the embodiments 1 to 4 and the comparative example of the invention is used for preparing a standard 8-shaped sample by a core shooter, and the tensile strength is measured according to a test method of the sand and the mixture for casting GB/T2684-2009 after the sample is demoulded and cooled to room temperature. The results are shown in the following table:
average tensile strength/MPa sand sample average mass/g mould heating time/min
As seen from the data in the table above, the average tensile strength of the samples prepared in the examples 2 to 4 of the invention is obviously improved, and although the average tensile strength of the sample prepared in the example 1 is lower, the average quality of the sample is generally higher as that of the samples prepared in the examples 2 to 4, the sand core is more compact, which indirectly indicates that the coated sand has good fluidity. The total liquid amount of the dry precoated sand is greatly reduced, so that the sand sample is high in hardening and drying speed, and the demolding time is shortened.
The dehydration temperature of the aluminum sulfate octadecahydrate adopted in the experiment is 86.5 ℃, and the dehydration amount of the aluminum sulfate octadecahydrate is gradually increased along with the temperature rise, in the embodiment 1 of the invention, the mold temperature is lower, the dehydration amount of the crystalline hydrate is less, the phosphate binder can not be fully wetted, and the dehydration rate is lower due to the lower temperature, so the average tensile strength is lower, the heating hardening time is long, in the embodiments 2 to 4, the dehydration amount of the crystalline hydrate is more, the phosphate binder is fully wetted, and the dehydration rate is increased due to the high temperature, so the sand sample tensile strength is high, and the heating hardening time is short.
According to the four embodiments and a comparative example, common magnesite has the functions of absorbing moisture and solidifying after being mixed with a liquid phosphate binder, because the magnesite is reacted with the phosphate binder, the common magnesite is not used when preparing phosphate binder coated sand, which is common knowledge of technicians in the field, but the invention skillfully utilizes the moisture absorption characteristic of the magnesite to prevent the moisture absorption of a dry coated sand binder, because the reactivity of the magnesite is influenced to a certain extent after the magnesite is excessively absorbed moisture, PVP is adopted for coating treatment, because the PVP is also water-soluble, the PVP can absorb water and is coated on the surface of the magnesite, so that the moisture absorption of the magnesite is weakened, firstly, the magnesite is added after the phosphate binder is dried, and the solid phosphate binder can not react at the moment, secondly, the magnesium sand is coated, the contact between the magnesite and the phosphate binder is isolated, and after the dry coated sand is prepared, when the precoated sand is used, after encountering a hot mold, PVP is dissolved due to the water discharging effect of the crystal hydrate, magnesia is exposed, and the magnesia can react with the phosphate binder which is dissolved at the same time, so that the magnesia also plays a role of a curing agent;
the coupling agent is alkaline, so that dehydration can be accelerated during preparation of the precoated sand, dry precoated sand can be obtained quickly, the moisture absorption resisting effect is achieved during storage of the precoated sand, the coupling agent can be hydrolyzed again due to moisture release of aluminum sulfate octadecahydrate during application of the precoated sand, curing of a phosphate binder is accelerated, and the coupling agent plays a role in resisting moisture absorption in a cured product due to the fact that the curing is carried out at a high temperature;
the aluminum sulfate octadecahydrate has more crystal water, is invisible water, does not affect the fluidity of sand, and skillfully utilizes the water released at a certain temperature to wet the phosphoric acid binder, so that the dry binder is dissolved again, sand grains are connected, and then the sand grains are solidified, so that the sand mold has strength;
the application uses silicic acid, and the silicic acid can also obtain certain moisture and has slow water loss, so that the water released by aluminum sulfate octadecahydrate in the molding sand on the surface of a hot mold is prevented from being lost too early, and a binder in the molding sand cannot be fully wetted;
although the CN 109550888B-disodium ethylenediamine tetraacetate modified phosphate binder and the preparation and application thereof describe EDTA-2Na, the EDTA is not the same as the diethylenetriamine pentaacetic acid, the diethylenetriamine pentaacetic acid is a salt, and the diethylenetriamine pentaacetic acid is an organic acid, has hygroscopicity, has complexing effect with metal ions, and can also be matched with silicic acid to play a certain role in water retention when coated sand is heated, so that the surface of a sand mold has better surface safety.
Although CN 109454200B-a liquid curing agent for phosphate binder and its application describe that when the adding amount of silane coupling agent reaches 24% -36% of the binder, they produce polymerization reaction at room temperature to form polymer containing P-O-Si group, and form carbonate under the condition of blowing compressed air to accelerate the reaction speed, so that the sample has a certain initial strength, in the course of storage, the polymerization reaction is gradually completed, the strength of the sample is gradually increased to reach the peak value, and it has good moisture-proof performance, the water-soluble citric acid in the component II is dissolved in water to form water solution which is easy to be stably stored, and after being mixed with the binder at normal temperature, it can be added into the molding sand to play double roles: on one hand, the chemical reaction with air in the storage of the molding sand can be slowed down, the service life of the molding sand is greatly prolonged, and on the other hand, the reaction with a silane coupling agent can generate a jelly containing B-O-Si groups, so that the combination among sand grains is tighter, and the strength of a sample is further improved; the water in the component II is used as a solvent of citric acid on one hand, and can dissolve the citric acid, and on the other hand, the phosphate binder can be diluted, so that the chemical reaction in the sand mixing process is slowed down, the usable time of the molding sand is prolonged, and the components can be more uniformly wrapped on the surface of sand grains in the sand mixing process, so that the internal strength of the prepared sample is more uniform; the effects of the silane coupling agent and citric acid are disclosed, but the technical scheme of the invention is not suggested; because the present application uses the different roles that the coupling agent plays in the two stages: in the stage of preparing the precoated sand, the precoated sand needs to be dried as soon as possible, the precoated sand has the moisture absorption resistance effect, the temperature is not high during the preparation of the precoated sand, the coupling agent is not inactivated, in the stage of forming the precoated sand, the coupling agent is hydrolyzed again, and the effect of accelerating curing can be exerted again at a higher temperature, and at the moment, the coupling agent is basically inactivated, so that the moisture absorption resistance effect with long time can be achieved.
In conclusion, the curing agent for inorganic phosphate binder precoated sand is applied, the obtained dry precoated sand is sieved to obtain loose sand, and the water in the phosphate binder in the dry precoated sand is removed before extraction, so that the amount of the adopted liquid auxiliary materials is small, the total liquid amount is greatly reduced, the fluidity of the sand is greatly improved, and the sand shooting and filling are facilitated to obtain a compact sand core; in addition, the crystal hydrate particles wrapped in the phosphate binder are dehydrated under the heating condition of the mould, so that the solid phosphate binder on the surface of the sand grains is liquefied again, the sand grains are connected with each other, and the sand core is rapidly solidified due to the catalytic action of the auxiliary materials and the heating of the mould, so that the sand sample is prepared.
While the foregoing is directed to the preferred embodiment of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.
Claims (6)
1. The curing agent for the inorganic phosphate binder precoated sand is characterized by comprising the following components:
coupling agent: 2-6 parts;
phosphate binder: 25-40 parts;
organic weak acid aqueous solution: 2-6 parts;
crystalline hydrate: 25-30 parts of a solvent;
coating magnesite powder with PVP: 30-50 parts of a solvent;
the coupling agent is a silane coupling agent: KH 550; the organic weak acid aqueous solution is a citric acid aqueous solution with the mass ratio of 1: 2.
2. The curing agent for inorganic phosphate binder coated sand according to claim 1, wherein the phosphate binder is a diethylenetriamine pentaacetic acid modified phosphate binder, and comprises the following raw materials in parts by weight:
industrial phosphoric acid: 50.92 parts;
aluminum hydroxide powder: 11.68 parts;
silicic acid: 0.3 part;
boric acid: 1.81 parts;
magnesium oxide: 1.21 parts;
citric acid: 0.3 part
Copper oxide: 0.9 part;
zinc oxide: 0.9 part;
yttrium oxide: 0.04 parts;
DTPA: 1.81 parts;
water: 30.13 parts.
3. The curing agent for inorganic phosphate binder-coated sand according to claim 1, characterized in that: the crystalline hydrate is aluminum sulfate octadecahydrate.
4. The curing agent for inorganic phosphate binder-coated sand according to claim 1, characterized in that: the PVP coated magnesia powder is fused magnesia powder, and the granularity of the fused magnesia powder is 800-1000 meshes.
5. The use of the curing agent for inorganic phosphate binder coated sand as defined in any one of claims 1 to 4 in the preparation of foundry sand molds, characterized in that: mixing standard sand with a coupling agent accounting for 0.2-0.6% of the standard sand by mass to obtain mixed sand, then, phosphate binder accounting for 2.5 to 4.0 percent of the standard sand by mass, organic weak acid aqueous solution accounting for 0.2 to 0.6 percent of the standard sand by mass and crystal hydrate accounting for 2.5 to 3.5 percent of the standard sand by mass are mixed uniformly in advance, then adding the mixed sand to continue mixing, finally crushing, drying and dehydrating under the condition of introducing hot air until no obvious agglomeration exists to obtain dry precoated sand, the temperature of the hot air is lower than the water loss temperature of the crystalline hydrate, PVP (polyvinyl pyrrolidone) coated magnesia powder accounting for 3-5% of the standard sand mass percent is added after screening the dry coated sand, the finished coated sand is obtained after uniform mixing, a core shooter is utilized to spray the finished coated sand into a mould, and heating for curing, and then demoulding, wherein the heating temperature is 150-170 ℃ higher than the water loss temperature of the crystalline hydrate.
6. Use according to claim 5, characterized in that: the temperature of the hot air is 40-50 ℃.
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| CN113732241B (en) * | 2021-08-25 | 2023-04-07 | 湖北工业大学 | Hydrophilic nano-silica modified inorganic phosphate binder and application thereof |
| CN113510217B (en) * | 2021-09-15 | 2021-12-24 | 中车戚墅堰机车车辆工艺研究所有限公司 | Inorganic dry precoated sand for warm core box molding and core making method thereof |
| CN113787165B (en) * | 2021-09-29 | 2023-05-26 | 江西特欣实业有限公司 | High-melting-point precoated sand with good fluidity |
| CN114535499B (en) * | 2021-12-31 | 2023-06-02 | 北京航空航天大学宁波创新研究院 | Moisture absorption resistant inorganic binder powder for casting, activating solution and using method |
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