阅读说明：本技术 一种无机覆膜砂用固化剂及包含其的无机覆膜砂芯 (Curing agent for inorganic coated sand and inorganic coated sand core containing curing agent ) 是由 刘栋 尹海军 李卓情 唐品 包羽冲 于 2020-12-24 设计创作，主要内容包括：本发明提供一种无机覆膜砂用固化剂,其包括氧化钙、氧化铜、乙二酸四乙酸二钠和十二烷基磺酸钠,其中氧化钙和氧化铜能够与无机覆膜砂中的表面粘结剂膜发生中和反应,缩短固化时间；乙二酸四乙酸二钠能够与无机覆膜砂和氧化铜、氧化钙反应得到的产物发生配合反应,形成稳定的多元配合物,有效增强砂芯强度；十二烷基磺酸钠溶于水后能够有效增加砂粒之间的流动性,从而使用砂芯表面更加致密、光滑,且能有效屏蔽大气中的水分侵入,防止出现造成强度下降,砂芯结构变软断裂等问题。本发明得到的砂芯的固化时间在135s以下,抗拉强度在2.33MPa以上；24h抗拉强度下降率在25％以下,具有表安性好、强度高、存放稳定的优点。(The invention provides a curing agent for inorganic precoated sand, which comprises calcium oxide, copper oxide, disodium edetate and sodium dodecyl sulfate, wherein the calcium oxide and the copper oxide can be subjected to neutralization reaction with a surface binder film in the inorganic precoated sand, so that the curing time is shortened; the disodium ethylene diamine tetraacetate can perform a matching reaction with a product obtained by the reaction of the inorganic coated sand, copper oxide and calcium oxide to form a stable multi-element complex, so that the strength of the sand core is effectively enhanced; the sodium dodecyl sulfate can effectively increase the fluidity among sand grains after being dissolved in water, so that the surface of the sand core is more compact and smooth, the invasion of moisture in the atmosphere can be effectively shielded, and the problems of strength reduction, softening and breaking of the sand core structure and the like are prevented. The curing time of the sand core obtained by the invention is below 135s, and the tensile strength is above 2.33 MPa; the reduction rate of the tensile strength is below 25 percent after 24 hours, and the composite material has the advantages of good surface safety, high strength and stable storage.)

1. The curing agent for the inorganic precoated sand is characterized by comprising the following components in percentage by weight:

30 to 50 percent of calcium oxide,

5 to 20 percent of copper oxide,

20 to 40 percent of ethylene diacid tetraacetic acid disodium salt,

10 to 25 percent of sodium dodecyl sulfate.

2. The curing agent for the inorganic precoated sand according to claim 1, which is characterized by comprising the following components in percentage by weight:

29.5 to 45.7 percent of calcium oxide,

10.2 to 20.4 percent of copper oxide,

25 to 33.5 percent of ethylene diacid tetraacetic acid disodium salt,

11.5 to 23.3 percent of sodium dodecyl sulfate.

3. The curing agent for the inorganic precoated sand according to claim 1, which is characterized by comprising the following components in percentage by weight:

40 percent of calcium oxide,

15 percent of copper oxide,

30 percent of ethylene diacid tetraacetic acid disodium salt,

15 percent of sodium dodecyl sulfate.

4. Use of the curing agent for inorganic precoated sand according to any one of claims 1 to 3 in phosphate inorganic precoated sand.

5. The use according to claim 4, wherein the curing agent is added to the phosphate inorganic precoated sand in an amount of 0.4 to 1.4 wt%.

6. The preparation method of the inorganic coated sand core is characterized by comprising the following steps:

(1) weighing phosphate inorganic precoated sand, adding the inorganic precoated sand curing agent as defined in any one of claims 1 to 3, and uniformly stirring to obtain mixed sand;

(2) performing sand shooting and core making on the mixed sand obtained in the step (1); and then spraying water mist to carry out molding and curing of the sand core, thereby obtaining the inorganic precoated sand core.

7. The inorganic precoated sand core of claim 6, wherein in step (1), the phosphate binder is used in an amount of 1.5 to 3 wt% in the phosphate inorganic precoated sand.

8. The inorganic coated sand core of claim 7, wherein the phosphate binder has a degree of neutralization of 32%.

9. The inorganic coated sand core of claim 6, wherein in step (1), the stirring time is 20 to 45 s.

10. The inorganic coated sand core of claim 6, wherein in step (2), the rate of spraying water mist is 45-55mL/s, the diameter of water mist particles is below 10 μm, and the spraying time is 3-10 s.

Technical Field

The invention belongs to the technical field of precoated sand, and particularly relates to a curing agent for inorganic precoated sand, application of the curing agent and an inorganic precoated sand core containing the curing agent.

Background

Compared with the traditional organic resin, the inorganic binder does not generate toxic and harmful gases in the casting production process, can greatly improve the casting production operation environment, and is an environment-friendly casting material. The practical application of the inorganic binder still has some problems, and firstly, the use of the inorganic binder needs matched production equipment, thereby causing the equipment cost of a casting enterprise to be increased. In addition, the use of the inorganic binder has various problems such as a short usable time of the kneaded sand and poor storage stability. Therefore, the inorganic binder is currently used in a small range and is applied under severe conditions.

Disclosure of Invention

In order to solve the technical problems, the invention provides a curing agent for phosphate inorganic coated sand, which can react with an adhesive film on the surface of the phosphate inorganic coated sand to realize rapid curing and molding, and a sand core with good surface safety, high strength and stable storage is prepared.

The invention aims to provide a curing agent for inorganic coated sand.

The invention also aims to provide the application of the curing agent in the phosphate inorganic coated sand.

It is a further object of the present invention to provide an inorganic coated sand core including the curing agent described above.

The invention provides a curing agent for inorganic precoated sand, which comprises the following components in percentage by weight:

30 to 50 percent of calcium oxide,

5 to 20 percent of copper oxide,

20 to 40 percent of ethylene diacid tetraacetic acid disodium salt,

10 to 25 percent of sodium dodecyl sulfate.

The curing agent for the inorganic precoated sand comprises disodium oxalate tetraacetate, sodium dodecyl sulfate, alkaline metal oxide calcium oxide and copper oxide, wherein the alkaline metal oxide calcium oxide and the copper oxide can perform a neutralization reaction with an acidic substance-surface binder film in the inorganic precoated sand to play a role in curing; the disodium edetate is a polydentate ligand, and can perform a matching reaction with a product obtained by reacting inorganic precoated sand and an alkaline metal oxide to form a stable multi-element complex, so that the strength of the sand core is effectively enhanced; the sodium dodecyl sulfate is a surfactant, and can effectively increase the fluidity among sand grains after being dissolved in water, so that the surface of the sand core is more compact and smooth, the water invasion in the atmosphere can be effectively shielded, and the problems of strength reduction, softening and breaking of the sand core structure and the like are prevented.

Preferably, the sum of the weight of the calcium oxide and the copper oxide is more than 50 wt%. Further preferably, the sum of the weights of calcium oxide and copper oxide is between 50 and 55 wt%. In the invention, calcium oxide and copper oxide can perform neutralization reaction with acidic phosphate colloid to play a role in curing, and metal ions in the calcium oxide and the copper oxide can perform coordination reaction with disodium edetate to form a multi-element complex with a more stable structure, so that the strength and the stability of the sand core can be effectively enhanced; when the content of calcium oxide and copper oxide is too low, the curing time is too long, and when the content of calcium oxide and copper oxide is too high, the strength of the sand core is affected.

The curing agent for the inorganic coated sand preferably comprises the following components in percentage by weight:

29.5 to 45.7 percent of calcium oxide,

10.2 to 20.4 percent of copper oxide,

25 to 33.5 percent of ethylene diacid tetraacetic acid disodium salt,

11.5 to 23.3 percent of sodium dodecyl sulfate.

The raw materials in the curing agent react with the inorganic precoated sand in the process of preparing the inorganic precoated sand, and different raw materials have different effects and different reactions, so the inventor researches and finds that the basic metal oxide sub-calcium oxide and copper oxide have the advantages that the curing time is below 135s and the curing effect is good within the weight range; wherein, the disodium ethylene diamine tetraacetic acid is in the weight range, the obtained sand core has high tensile strength, and the tensile strength is more than 2.33 MPa; the sodium dodecyl sulfate is in the weight range, the obtained precoated sand has high moisture absorption resistance, and the reduction rate of the 24-hour tensile strength is below 25%.

The curing agent for the inorganic coated sand preferably comprises the following components in percentage by weight:

40 percent of calcium oxide,

15 percent of copper oxide,

30 percent of ethylene diacid tetraacetic acid disodium salt,

15 percent of sodium dodecyl sulfate.

The raw materials in the curing agent react with the inorganic precoated sand in the process of preparing the inorganic precoated sand, and different raw materials have different effects and different reactions, so the inventor researches and finds that the basic metal oxide sub-calcium oxide and copper oxide have the advantages that the curing time is below 130s and the curing effect is good within the weight range; wherein, the disodium ethylene diamine tetraacetic acid is in the weight range, the obtained sand core has high tensile strength, and the tensile strength is more than 2.6 MPa; the sodium dodecyl sulfate is in the weight range, the obtained precoated sand has high moisture absorption resistance, and the reduction rate of the 24-hour tensile strength is below 15%.

The curing agent for inorganic precoated sand provided by the invention can be applied to phosphate inorganic precoated sand, and can accelerate the curing speed of the inorganic sand in the process of preparing the sand core, so that the sand core with good surface safety, high strength and high storage stability is obtained.

Preferably, the addition amount of the curing agent in the phosphate inorganic coated sand is 0.4-1.4 wt%. The curing agent provided by the invention is less in use amount in inorganic precoated sand, and can achieve good performance on the premise of small addition.

The invention provides an inorganic coated sand core, and a preparation method thereof comprises the following steps:

(1) weighing phosphate inorganic precoated sand, adding the inorganic precoated sand curing agent as defined in any one of claims 1 to 3, and uniformly stirring to obtain mixed sand;

(2) performing sand shooting and core making on the mixed sand obtained in the step (1); and then spraying water mist to carry out molding and curing of the sand core, thereby obtaining the inorganic precoated sand core.

Preferably, in the step (1), the phosphate inorganic coated sand is prepared by coating a phosphate binder on raw sand. The phosphate binder for the phosphate inorganic coated sand adopted by the invention is a phosphate inorganic binder for casting.

Further preferably, the phosphate binder is used in an amount of 1.5 to 3 wt%, and the degree of neutralization of the phosphate binder is 32%.

Preferably, in step (1), the stirring time is 20-45 s.

Preferably, in the step (2), the spraying speed of the water mist is 45-55mL/s, the diameter of the water mist particles is less than 10 μm, and the spraying time is 3-10 s.

The invention has the beneficial effects that:

1. the curing agent for the inorganic precoated sand comprises disodium oxalate tetraacetate, sodium dodecyl sulfate, alkaline metal oxide calcium oxide and copper oxide, wherein the alkaline metal oxide calcium oxide and the copper oxide can perform a neutralization reaction with a surface binder film in the inorganic precoated sand to play a role in curing; the disodium edetate is a polydentate ligand, and can perform a matching reaction with a product obtained by reacting inorganic precoated sand and an alkaline metal oxide to form a stable multi-element complex, so that the strength of the sand core is effectively enhanced; the sodium dodecyl sulfate is a surfactant, and can effectively increase the fluidity among sand grains after being dissolved in water, so that the surface of the sand core is more compact and smooth, the water invasion in the atmosphere can be effectively shielded, and the problems of strength reduction, softening and breaking of the sand core structure and the like are prevented.

2. In the using process of the curing agent for inorganic precoated sand, the curing agent is fully mixed with phosphate inorganic precoated sand, and then the mixture is injected into a mold cavity, and water mist is sprayed to the mold cavity; the phosphate binder film on the surface of the inorganic phosphate precoated sand firstly absorbs water rapidly to form dihydric phosphate colloid, then calcium oxide and copper oxide and the acidic dihydric phosphate colloid are subjected to neutralization reaction, high-temperature heating is not needed, the curing is accelerated, the curing time is shortened, and the inorganic precoated sand and the curing agent do not react chemically during sand mixing, so that the usable time after sand mixing is greatly prolonged; the disodium edetate is a polydentate ligand, and after the dihydric phosphate reacts with the alkaline metal oxide, metal ions in the reactant and the disodium edetate can perform a matching reaction to form a multi-element complex with a more stable structure, so that the strength and the stability of the sand core can be effectively enhanced; the sodium dodecyl sulfate can effectively increase the fluidity among sand grains after being dissolved in water, so that the surface of the sand core obtained by using the sand core is more compact and smooth, the invasion of moisture in the atmosphere can be effectively shielded, and the problems of strength reduction, softening and breaking of the sand core structure and the like are prevented.

3. The preparation process of the inorganic precoated sand core provided by the invention is simple, the cost is low, the process control is convenient, and the curing agent for phosphate inorganic precoated sand and the sand core which meet the requirement of casting production can be prepared.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be described in detail below. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the examples given herein without any inventive step, are within the scope of the present invention.

The invention provides a phosphate inorganic coated sand core,

the raw materials comprise inorganic phosphate precoated sand and an inorganic precoated sand curing agent, wherein the amount of the curing agent is 0.4-1.4 wt% of that of the inorganic phosphate precoated sand;

the inorganic precoated sand curing agent comprises the following components in percentage by weight:

30 to 50 percent of calcium oxide,

5 to 20 percent of copper oxide,

20 to 40 percent of ethylene diacid tetraacetic acid disodium salt,

10 to 25 percent of sodium dodecyl sulfate;

the inorganic precoated sand core of phosphate provided by the invention takes inorganic precoated sand of phosphate as a base material, and takes disodium oxalate, sodium dodecyl sulfate, alkaline metal oxide calcium oxide and copper oxide as inorganic precoated sand curing agents, in the preparation process of the sand core, a phosphate binder film on the surface of the inorganic precoated sand of phosphate firstly absorbs water rapidly to form dihydrogen phosphate colloid, and then calcium oxide and copper oxide and acidic dihydrogen phosphate colloid are subjected to neutralization reaction to play a role in curing; the component disodium oxalate tetraacetate in the inorganic coated sand curing agent is a polydentate ligand, after dihydric phosphate reacts with alkaline metal oxide, metal ions in a reactant can generate a matching reaction with the disodium oxalate tetraacetate to form a multi-element complex with a more stable structure, so that the strength and the stability of the sand core can be effectively enhanced; the sodium dodecyl sulfate can effectively increase the fluidity among sand grains after being dissolved in water, so that the surface of the sand core obtained by using the sand core is more compact and smooth, the invasion of moisture in the atmosphere can be effectively shielded, and the problems of strength reduction, softening and breaking of the sand core structure and the like are prevented.

Preferably, the inorganic precoated sand curing agent comprises the following components in percentage by weight:

29.5 to 45.7 percent of calcium oxide,

10.2 to 20.4 percent of copper oxide,

25 to 33.5 percent of ethylene diacid tetraacetic acid disodium salt,

11.5 to 23.3 percent of sodium dodecyl sulfate.

It is further preferred that the first and second liquid crystal compositions,

the inorganic precoated sand curing agent comprises the following components in percentage by weight:

40 percent of calcium oxide,

15 percent of copper oxide,

30 percent of ethylene diacid tetraacetic acid disodium salt,

15 percent of sodium dodecyl sulfate.

The inventor researches to find that the content of calcium oxide and copper oxide influences the curing time, the content of disodium edetate influences the strength of the sand core, and the sodium dodecyl sulfate influences the moisture absorption resistance of the sand core. When the weight percentage of each component is above, the curing time, the tensile strength and the moisture absorption resistance are optimal. Wherein the curing time is below 130s, the curing effect is good, the tensile strength is above 2.6MPa, and the reduction rate of the tensile strength is below 15% in 24 h.

The preparation method of the phosphate inorganic coated sand core comprises the following steps:

(1) weighing phosphate inorganic precoated sand, adding the inorganic precoated sand curing agent, and uniformly stirring to obtain mixed sand;

preferably, the phosphate inorganic coated sand comprises a phosphate binder, wherein the use amount of the phosphate binder is 1.5-3 wt%, and the neutralization degree of the phosphate binder is 30-35%;

the phosphate inorganic coated sand adopted by the invention adopts the phosphate adhesive with the performance, has small addition amount, can realize good reaction with the curing agent of the invention, and obtains a sand core with high strength and high stability.

Preferably, the stirring time is 20 to 45 s.

The curing agent and the matrix material can be fully contacted after being stirred for 20-45s, which is beneficial to the subsequent reaction.

(2) Performing sand shooting and core making on the mixed sand obtained in the step (1); and then spraying water mist to carry out molding and curing of the sand core, thereby obtaining the inorganic precoated sand core.

Preferably, the speed of spraying the water mist is 45-55mL/s, the diameter of water mist particles is below 10 mu m, and the spraying time is 3-10 s.

The sand core is formed and solidified by spraying water mist to the sand core, the water mist is uniformly sprayed, all components in the sand core can fully react, the solidification is accelerated, the reaction is more uniform, and the strength of the sand core is effectively improved.

The invention provides the following examples in particular.

Example 1

A phosphate inorganic coated sand core,

the raw materials comprise phosphate inorganic precoated sand and an inorganic precoated sand curing agent,

the amount of the curing agent is 0.4 wt% of the phosphate inorganic precoated sand;

the inorganic precoated sand curing agent comprises the following components in percentage by weight:

50 percent of calcium oxide,

5 percent of copper oxide,

20 percent of ethylene diacid tetraacetic acid disodium salt,

25% of sodium dodecyl sulfate;

the preparation method of the phosphate inorganic coated sand core comprises the following steps:

(1) weighing phosphate inorganic precoated sand, adding the inorganic precoated sand curing agent, and stirring for 20s to be uniform to obtain mixed sand; the phosphate inorganic coated sand is prepared by coating a phosphate inorganic binder on raw sand, wherein the use amount of the phosphate inorganic binder is 1.5 wt%, and the neutralization degree of the phosphate inorganic binder is 32%;

(2) performing sand shooting and core making on the mixed sand obtained in the step (1); and then spraying water mist, wherein the spraying speed is 45mL/s, the diameter of water mist particles is less than 10 microns, and the spraying time is 3s, and molding and curing the sand core to obtain the inorganic coated sand core.

Example 2

A phosphate inorganic coated sand core,

the raw materials comprise phosphate inorganic precoated sand and an inorganic precoated sand curing agent,

the amount of the curing agent is 1.4 wt% of the phosphate inorganic precoated sand;

the inorganic precoated sand curing agent comprises the following components in percentage by weight:

30 percent of calcium oxide,

20 percent of copper oxide,

40 percent of ethylene diacid tetraacetic acid disodium salt,

10% of sodium dodecyl sulfate;

the preparation method of the phosphate inorganic coated sand core comprises the following steps:

(1) weighing phosphate inorganic precoated sand, adding the inorganic precoated sand curing agent, and stirring for 45s until the mixture is uniform to obtain mixed sand; the phosphate inorganic coated sand is prepared by coating a phosphate inorganic binder on raw sand, wherein the use amount of the phosphate inorganic binder is 3 wt%, and the neutralization degree of the phosphate inorganic binder is 32%;

(2) performing sand shooting and core making on the mixed sand obtained in the step (1); and then spraying water mist, wherein the spraying speed is 55mL/s, the diameter of water mist particles is less than 10 microns, the spraying time is 3-10s, and the sand core is molded and cured for 20-45s to obtain the inorganic coated sand core.

Example 3

A phosphate inorganic coated sand core,

the raw materials comprise phosphate inorganic precoated sand and an inorganic precoated sand curing agent,

the amount of the curing agent is 1 wt% of the phosphate inorganic precoated sand;

the inorganic precoated sand curing agent comprises the following components in percentage by weight:

29.5 percent of calcium oxide,

20.4 percent of copper oxide,

33.5 percent of ethylene diacid tetraacetic acid disodium salt,

16.6 percent of sodium dodecyl sulfate;

the preparation method of the phosphate inorganic coated sand core comprises the following steps:

(1) weighing phosphate inorganic precoated sand, adding the inorganic precoated sand curing agent, and stirring for 30s to be uniform to obtain mixed sand; the phosphate inorganic coated sand is prepared by coating a phosphate inorganic binder on raw sand, wherein the use amount of the phosphate inorganic binder is 2 wt%, and the neutralization degree of the phosphate inorganic binder is 32%;

(2) performing sand shooting and core making on the mixed sand obtained in the step (1); and then spraying water mist, wherein the spraying speed is 50mL/s, the diameter of water mist particles is less than 10 microns, and the spraying time is 8s, and molding and curing the sand core to obtain the inorganic coated sand core.

Example 4

A phosphate inorganic coated sand core,

the raw materials comprise phosphate inorganic precoated sand and an inorganic precoated sand curing agent,

the amount of the curing agent is 1.2 wt% of the phosphate inorganic precoated sand;

the inorganic precoated sand curing agent comprises the following components in percentage by weight:

45.7 percent of calcium oxide,

10.2 percent of copper oxide,

32.6 percent of ethylene diacid tetraacetic acid disodium salt,

11.5 percent of sodium dodecyl sulfate;

the preparation method of the phosphate inorganic coated sand core comprises the following steps:

(1) weighing phosphate inorganic precoated sand, adding the inorganic precoated sand curing agent, and stirring for 35s until the mixture is uniform to obtain mixed sand; the phosphate inorganic coated sand is prepared by coating a phosphate inorganic binder on raw sand, wherein the use amount of the phosphate inorganic binder is 2.5 wt%, and the neutralization degree of the phosphate inorganic binder is 32%;

(2) performing sand shooting and core making on the mixed sand obtained in the step (1); and then spraying water mist, wherein the spraying speed is 50mL/s, the diameter of water mist particles is less than 10 microns, and the spraying time is 8s, and molding and curing the sand core to obtain the inorganic coated sand core.

Example 5

A phosphate inorganic coated sand core,

the raw materials comprise phosphate inorganic precoated sand and an inorganic precoated sand curing agent,

the amount of the curing agent is 0.8 wt% of the phosphate inorganic precoated sand;

the inorganic precoated sand curing agent comprises the following components in percentage by weight:

36.7 percent of calcium oxide,

15 percent of copper oxide,

25 percent of ethylene diacid tetraacetic acid disodium salt,

23.3 percent of sodium dodecyl sulfate;

the preparation method of the phosphate inorganic coated sand core is the same as that of the example 4.

Example 6

A phosphate inorganic coated sand core,

the raw materials comprise phosphate inorganic precoated sand and an inorganic precoated sand curing agent,

the amount of the curing agent is 0.8 wt% of the phosphate inorganic precoated sand;

the inorganic precoated sand curing agent comprises the following components in percentage by weight:

40 percent of calcium oxide,

15 percent of copper oxide,

30 percent of ethylene diacid tetraacetic acid disodium salt,

15% of sodium dodecyl sulfate;

the preparation method of the phosphate inorganic coated sand core is the same as that of the example 4.

Comparative example 1

A phosphate inorganic coated sand core,

the raw materials comprise phosphate inorganic precoated sand and an inorganic precoated sand curing agent,

the using amount of the curing agent is 20 wt% of the phosphate inorganic coated sand;

the inorganic precoated sand curing agent is commercially available fused magnesia powder as a curing agent.

The preparation method of the phosphate inorganic coated sand core comprises the following steps:

(1) weighing phosphate inorganic precoated sand, adding the inorganic precoated sand curing agent, and stirring for 35s until the mixture is uniform to obtain mixed sand; the phosphate inorganic coated sand is prepared by coating a phosphate inorganic binder on raw sand, wherein the use amount of the phosphate inorganic binder is 2 wt%, and the neutralization degree of the phosphate inorganic binder is 32%;

(2) performing sand shooting and core making on the mixed sand obtained in the step (1); and then spraying water mist, wherein the spraying speed is 50mL/s, the diameter of water mist particles is less than 10 microns, and the spraying time is 8s, and molding and curing the sand core to obtain the inorganic coated sand core.

Comparative example 2

A phosphate inorganic coated sand core,

the raw materials comprise phosphate inorganic precoated sand and an inorganic precoated sand curing agent,

the amount of the curing agent is 0.8 wt% of the phosphate inorganic precoated sand;

the inorganic precoated sand curing agent comprises the following components in percentage by weight:

20 percent of calcium oxide,

15 percent of copper oxide,

60 percent of ethylene diacid tetraacetic acid disodium salt,

5% of sodium dodecyl sulfate;

the preparation method of the phosphate inorganic coated sand core is the same as that of the example 4.

Comparative example 3

A phosphate inorganic coated sand core,

the raw materials comprise phosphate inorganic precoated sand and an inorganic precoated sand curing agent,

the amount of the curing agent is 0.8 wt% of the phosphate inorganic precoated sand;

the inorganic precoated sand curing agent comprises the following components in percentage by weight:

50 percent of calcium oxide,

30 percent of copper oxide,

15 percent of ethylene diacid tetraacetic acid disodium salt,

5% of sodium dodecyl sulfate;

the preparation method of the phosphate inorganic coated sand core is the same as that of the example 4.

Test examples

The phosphate inorganic coated sand cores obtained in examples 1 to 6 and comparative examples 1 to 3 were tested for tensile strength according to JB/T8583-2008; testing the tensile strength for 24 hours according to JB/T8583-2008, and calculating the rate of reduction of the tensile strength after 24 hours compared with the initial tensile strength to obtain the moisture absorption resistance of the fabric; the method for detecting the curing time comprises the following steps: when the measured surface hardness of the sample reaches 90H, the pointer of the hardness meter does not rotate obviously, the sample is considered to be hardened, the time of the hardening is counted, 5 samples are tested in each group, and the average value is calculated to obtain the curing time of the sample. The results are shown in Table 1.

TABLE 1 Sand core Performance test results

As can be seen from the results in table 1, in comparative example 1, the conventional fused magnesite powder is used as the inorganic phosphate precoated sand curing agent, and when the conventional fused magnesite powder is used, the addition amount is large, the curing time is long, the strength is far lower than that of the sand core provided by the invention, and the moisture absorption resistance is far lower than that of the sand core provided by the invention. The sand core provided by the comparative example 2 has lower content of alkaline oxides of calcium oxide and copper oxide, the curing time is prolonged, the content of sodium dodecyl sulfate is low, and the moisture absorption resistance is seriously reduced; the sand core provided by the comparative example 3 has low content of disodium edetate, low tensile strength, low content of sodium dodecyl sulfate and seriously reduced moisture absorption resistance. The reason is that the addition of the alkaline metal oxide has great influence on the curing time, but the strength of the alkali metal oxide can be influenced when the addition amount of the alkaline metal oxide is too large, the disodium ethylene diamine tetraacetate reacts with metal ions in a matched manner to be saturated after the addition amount is higher than 30%, the strength cannot be further improved when the addition amount is continuously increased, and the content of other substances is influenced when the addition amount is continuously increased to reach 40%, and the tensile strength is reduced on the contrary. The sand core obtained in the embodiments 1 to 6 of the present invention has a curing time of 135s or less, a tensile strength of 2.33MPa or more, and a 24-hour strength reduction rate of 25.0% or less, which indicates that the sand core provided by the present invention has a shorter curing time, a higher tensile strength, and a better moisture absorption resistance.

The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.