阅读说明：本技术 一种覆膜砂及其制备工艺 (Precoated sand and preparation process thereof ) 是由 朱程远 于 2021-07-24 设计创作，主要内容包括：本申请具体公开了一种覆膜砂,包含以下组分：石英砂、粘结剂、硬脂酸钙；粘结剂包含以下组分：淀粉、蔗糖、白云石粉、石英粉、环氧植物油、精氨酸。一种覆膜砂的制备工艺,包括以下步骤：S1,称取石英砂在870-900℃下焙烧4-6h；S2,将由S1得到的石英砂放置在(-10)-(-30)℃中冷却,得到冷却砂；S3,将冷却砂加入粘结剂以及硬脂酸钙搅拌混合均匀,冷却,得到混合料；S4,将混合料经过破碎、过筛,得到覆膜砂。粘结剂使用过程中无有害气体产生的原料制备得到,且覆膜砂具有强度高强度、发气量小的优点。添加沸石粉,使覆膜砂的透气性和强度均提高。通过采用氧化锌改性沸石粉,使覆膜砂的强度能进一步提高。(The application specifically discloses precoated sand, contains following component: quartz sand, a binder and calcium stearate; the binder comprises the following components: starch, sucrose, dolomite powder, quartz powder, epoxy vegetable oil and arginine. A preparation process of precoated sand comprises the following steps: s1, weighing quartz sand, and roasting at 870-900 ℃ for 4-6 h; s2, cooling the quartz sand obtained in S1 at (-10) - (-30) DEG C to obtain cooled sand; s3, adding the cooling sand into the binder and the calcium stearate, stirring and mixing uniformly, and cooling to obtain a mixture; and S4, crushing and sieving the mixture to obtain the precoated sand. The raw materials without harmful gas generation are prepared in the using process of the binder, and the precoated sand has the advantages of high strength and small gas evolution. The zeolite powder is added, so that the air permeability and the strength of the precoated sand are both improved. The zinc oxide modified zeolite powder is adopted, so that the strength of the precoated sand can be further improved.)

1. The precoated sand is characterized by comprising the following components in parts by weight:

500 portions and 600 portions of quartz sand;

40-60 parts of a binder;

1-2 parts of calcium stearate;

the adhesive comprises the following components in parts by weight: 50-60 parts of starch, 10-15 parts of cane sugar, 4-5 parts of dolomite powder, 20-30 parts of quartz powder, 1-2 parts of epoxy vegetable oil and 0.4-1 part of arginine.

2. The precoated sand according to claim 1, wherein: the preparation method of the adhesive comprises the following steps:

s1, weighing 20-30 parts by weight of quartz powder, 1-2 parts by weight of epoxy vegetable oil and 0.4-1 part by weight of arginine, stirring and reacting for 2-3h at the temperature of 160-95 ℃, and cooling to 85-95 ℃ to obtain a mixture A;

s2, weighing 50-60 parts of starch, 10-15 parts of sucrose, 16-20 parts of dolomite powder and 100-120 parts of water by weight, stirring and reacting for 1-2 hours at 85-95 ℃ to obtain a mixture B;

s3, adding the mixture B into the mixture A, stirring for 4-6h at the stirring speed of 1200-1500r/min, drying until the water content is less than 0.2%, and crushing and sieving to prepare the binder.

3. The precoated sand according to claim 1, wherein: the binder also comprises 2-4 parts by weight of zeolite powder, and the zeolite is mixed with starch, cane sugar, dolomite powder and water simultaneously.

4. The precoated sand according to claim 3, wherein: the zeolite powder is nano zinc oxide modified zeolite powder.

5. The precoated sand according to claim 4, wherein: the nano zinc oxide modified zeolite powder is prepared by the following method: weighing zeolite powder and nano zinc oxide, stirring and roasting for 4-6h at the temperature of 560-.

6. The precoated sand according to claim 1, wherein: the quartz sand is 40-100 meshes.

7. The precoated sand according to claim 6, wherein: the adhesive is 500-800 meshes.

8. A process for preparing precoated sand according to any one of claims 1 to 7, comprising the steps of:

s1, weighing 500-600 parts of quartz sand, and roasting at 870-900 ℃ for 4-6 h;

s2, cooling the quartz sand obtained in S1 in an environment of (-10) - (-30) DEG C to obtain cooled sand;

s3, taking out the cooling sand, heating to 160-180 ℃, adding 40-60 parts of binder and 1-2 parts of calcium stearate, stirring, mixing uniformly, and cooling to obtain a mixture;

and S4, crushing and sieving the mixture to obtain the precoated sand.

Technical Field

The application relates to precoated sand and a preparation process thereof.

Background

The precoated sand is molding sand or core sand with a layer of adhesive coated on the surface of sand grains before molding. The method comprises the steps of preheating sand to a certain temperature, adding a binder, stirring to enable the binder to be coated on the surface of sand grains, cooling, crushing and screening to obtain the coated sand. The precoated sand is mainly used for steel castings and iron castings.

In the related art, phenolic resin is generally used as a binder, and urotropine is added to enable the phenolic resin to be coated on the surface of sand grains after being cured, so that coated sand is obtained. However, the precoated sand prepared by the method generates harmful gas when in use, and is not beneficial to the health of workers.

Disclosure of Invention

In order to solve the problem that harmful gas is generated when the precoated sand prepared by adopting phenolic resin is used, the application provides the precoated sand and a preparation process thereof.

In a first aspect, the present application provides a precoated sand, which adopts the following technical scheme:

the precoated sand comprises the following components in parts by weight:

500 portions and 600 portions of quartz sand;

40-60 parts of a binder;

1-2 parts of calcium stearate;

the adhesive comprises the following components in parts by weight: 50-60 parts of starch, 10-15 parts of cane sugar, 4-5 parts of dolomite powder, 20-30 parts of quartz powder, 1-2 parts of epoxy vegetable oil and 0.4-1 part of arginine.

By adopting the technical scheme, the quartz sand is raw sand, and the calcium stearate is a lubricant. Compared with phenolic resin, the binder in the scheme has no harmful gas in the preparation and use processes, and is green and environment-friendly. And the binder enables the precoated sand to have better strength and smaller gas evolution. Starch and cane sugar are main bonding components, dolomite powder and quartz powder are used as carriers, and epoxy groups on the epoxy vegetable oil can react with carboxyl groups on arginine to generate high-viscosity elastomers, so that the strength and toughness of the precoated sand after curing are obviously improved. And the high-viscosity elastomer coats the outer surface of the quartz sand, so that the quartz sand has good compatibility in a binder system, and the quartz conveniently bears the binder components.

The preparation method of the optional adhesive comprises the following steps:

s1, weighing 20-30 parts by weight of quartz powder, 1-2 parts by weight of epoxy vegetable oil and 0.4-1 part by weight of arginine, stirring and reacting for 2-3h at the temperature of 160-95 ℃, and cooling to 85-95 ℃ to obtain a mixture A;

s2, weighing 50-60 parts of starch, 10-15 parts of sucrose, 16-20 parts of dolomite powder and 100-120 parts of water by weight, stirring and reacting for 1-2 hours at 85-95 ℃ to obtain a mixture B;

s3, adding the mixture B into the mixture A, stirring for 4-6h at the stirring speed of 1200-1500r/min, drying until the water content is less than 0.2%, and crushing and sieving to prepare the binder.

By adopting the technical scheme, the quartz powder, the epoxy vegetable oil and the arginine are reacted, so that the high-viscosity elastomer obtained after the reaction of the epoxy vegetable oil and the arginine is uniformly attached to the surface of the quartz powder. And pasting the starch, the sucrose and the dolomite powder, and mixing the pasted starch, the sucrose and the mixture A to enable the starch and the sucrose to be loaded on the dolomite powder and the quartz powder, thereby obtaining the binder.

Optionally, the binder further comprises 2-4 parts by weight of zeolite powder, and the zeolite is mixed with starch, sucrose, dolomite powder and water at the same time.

Through the technical scheme, the porous structure of the zeolite powder improves the air permeability of the precoated sand after the zeolite powder is added, and meanwhile, the zeolite powder can catalyze the chemical reaction between the binder and the surface of the quartz sand, so that the crosslinking degree is improved, the binding strength of the binder is improved, and a formed part obtained after the precoated sand is cured has better strength, so that defective products of cast parts are reduced.

Optionally, the zeolite powder is a nano zinc oxide modified zeolite powder.

By adopting the technical scheme, the catalytic performance of the nano zinc oxide modified zeolite powder on the binder and the quartz sand is higher, and the strength of the precoated sand is further improved.

Optionally, the nano zinc oxide modified zeolite powder is prepared by the following method: weighing zeolite powder and nano zinc oxide, stirring and roasting for 4-6h at the temperature of 560-.

Through the technical scheme, the nano-oxidation and zeolite powder are roasted at high temperature, so that the nano-zinc oxide is uniformly attached to the surface of the zeolite powder.

Optionally, the quartz sand is 40-100 meshes.

Through the technical scheme, the granularity of the quartz sand is moderate, so that the surface roughness of the casting is just required, the mesh number of the quartz sand is small, the surface roughness of the casting is easily caused, the mesh number of the quartz sand is large, the price is high, and the cost price is high.

Optionally, the binder is 500-800 meshes.

Through the technical scheme, the binder has large mesh number, namely small particle size, so that the binder is high in melting speed and can be conveniently and quickly attached to the surface of quartz sand.

In a second aspect, the present application provides a preparation process of precoated sand, which adopts the following technical scheme:

a preparation process of precoated sand comprises the following steps:

s1, weighing 500-600 parts of quartz sand, and roasting at 870-900 ℃ for 4-6 h;

s2, cooling the quartz sand obtained in S1 in an environment of (-10) - (-30) DEG C to obtain cooled sand;

s3, taking out the cooling sand, heating to 160-180 ℃, adding 40-60 parts of binder and 1-2 parts of calcium stearate, stirring, mixing uniformly, and cooling to obtain a mixture;

and S4, crushing and sieving the mixture to obtain the precoated sand.

By adopting the technical scheme, the quartz sand raw material is easy to obtain, and the cost price is lower. The quartz sand is heated to 870 plus 900 ℃ and undergoes phase change to ensure that the quartz sand has obvious expansion volume, and then is cooled at (-10) - (-30) DEG C to ensure that the quartz sand is not easy to recover phase change, namely a certain expansion state is still kept, and the precoated sand prepared from the quartz sand obtained by the treatment is not easy to undergo volume expansion at high temperature, so that the surface of a casting is not easy to have sand holes, peeling, vein or orange peel defects, and the qualification rate of the casting is higher.

Heating the quartz sand to 160-180 ℃, adding the binder, and adhering the binder to the surface of the quartz sand after the binder is melted, thereby obtaining the precoated sand.

In summary, the present application has the following beneficial effects:

1. the binder is prepared from raw materials without harmful gas, and the precoated sand has the advantages of high strength and small gas evolution.

2. The zeolite powder is added, so that the air permeability and the strength of the precoated sand are both improved.

3. The zinc oxide modified zeolite powder is adopted, so that the strength of the precoated sand is further improved.

Detailed Description

The present application will be described in further detail with reference to examples.

Name of raw materials	Species or origin
		Quartz sand	The Lingshou county Jiaqi mineral processing factory sells the product with 40 meshes, 80 meshes and 100 meshes
Calcium stearate	Calcium stearate powder sold by Jinan Kogyi and trade Co., Ltd
		Starch	Corn starch, technical grade, sold by Changzhou Yaoshengmei environmental protection science and technology Limited
Sucrose	Commercial of new materials from Jinan quanxing Co Ltd
		Dolomite powder	Shijiazhuanhuidli mineral products, sold by Limited, 1250 mesh
Quartz powder	Sold by processing factories of 1000 meshes
		Epoxy vegetable oil	Epoxidized soybean oil sold by Jinan Prolaihua chemical Co., Ltd
Arginine	Shandong Nuanju Biotech Co Ltd
		Zeolite powder	1000 mesh, sold by Beijing national investment science and technology GmbH
Nano zinc oxide	Superfine nanometer zinc oxide, HN-JH03, sold by Hangzhou Hengge nanotechnology Co., Ltd

Preparation example

Preparation example 1

Preparing nano zinc oxide modified zeolite:

weighing 2kg of zeolite powder and 0.24kg of nano zinc oxide, stirring and roasting at 560 ℃ for 4h to obtain the nano zinc oxide modified zeolite.

Preparation example 2

Preparing nano zinc oxide modified zeolite:

weighing 4kg of zeolite powder and 0.8kg of nano zinc oxide, stirring and roasting at 600 ℃ for 6h to obtain the nano zinc oxide modified zeolite.

Preparation example 3

Preparing nano zinc oxide modified zeolite:

3kg of zeolite powder and 0.5kg of nano zinc oxide are weighed and stirred and roasted for 5 hours at 586 ℃, and the nano zinc oxide modified zeolite is obtained.

Preparation example 4

Preparation of the binder:

s1, weighing 20kg of quartz powder, 1kg of epoxidized soybean oil and 0.4kg of arginine, stirring and reacting for 2h at 160 ℃, and cooling to 85 ℃ to obtain a mixture A;

s2, weighing 50kg of starch, 10kg of cane sugar, 16kg of dolomite powder and 100kg of water, stirring and reacting for 1 hour at 85 ℃ to obtain a mixture B;

and S3, adding the mixture B into the mixture A, stirring for 4 hours at the stirring speed of 1200r/min, drying until the water content is 0.1%, and crushing and sieving to prepare the 500-mesh binder.

Preparation example 5

Preparation of the binder:

s1, weighing 30kg of quartz powder, 2kg of epoxidized soybean oil and 1kg of arginine, stirring and reacting for 3h at the temperature of 170 ℃, and cooling to 95 ℃ to obtain a mixture A;

s2, weighing 60kg of starch, 15kg of cane sugar, 20kg of dolomite powder and 120kg of water, stirring and reacting for 2 hours at 95 ℃ to obtain a mixture B;

s3, adding the mixture B into the mixture A, stirring for 6 hours at a stirring speed of 1500r/min, drying until the water content is 0.18%, and crushing and sieving to prepare the 500-mesh binder.

Preparation example 6

Preparation of the binder:

s1, weighing 25kg of quartz powder, 1.6kg of epoxidized soybean oil and 0.6kg of arginine, stirring and reacting for 1.5h at 165 ℃, and cooling to 90 ℃ to obtain a mixture A;

s2, weighing 55kg of starch, 13kg of cane sugar, 18kg of dolomite powder and 110kg of water, stirring and reacting for 1.5 hours at 90 ℃ to obtain a mixture B;

and S3, adding the mixture B into the mixture A, stirring for 5 hours at the stirring speed of 1250r/min, drying until the water content is less than 0.1%, and crushing and sieving to prepare the 500-mesh binder.

Preparation example 7

The difference from preparation example 6 is that 800 mesh binder was prepared after crushing and sieving.

Preparation example 8

The difference from preparation example 6 is that 625 mesh binder was prepared by crushing and sieving.

Preparation example 9

The difference from preparation example 6 is that 400 mesh binder was prepared after crushing and sieving.

Preparation example 10

The difference from preparation example 6 is that 1000 mesh binder was prepared after crushing and sieving.

Preparation example 11

The difference from preparation example 8 is that 2kg of zeolite powder was further added in the step of S2.

Preparation example 12

The difference from preparation example 8 is that 4kg of zeolite powder was also added in the step of S2.

Preparation example 13

The difference from preparation example 8 is that 4kg of the nano zinc oxide modified zeolite powder obtained in preparation example 1 was further added in the step of S2.

Preparation example 14

The difference from preparation example 13 is that the nano zinc oxide modified zeolite powder is prepared from preparation example 2.

Preparation example 15

The difference from preparation example 13 is that nano zinc oxide modified zeolite powder is prepared by preparation example 3.

Preparation example 16

The difference from preparation example 6 is that quartz powder was added in the step of S2.

Examples

Example 1

The preparation process of the precoated sand comprises the following steps:

s1, weighing 500kg of quartz sand of 40 meshes, and roasting at 870 ℃ for 4-6 h;

s2, placing the quartz sand obtained in the step S1 in an environment with the temperature of-10 ℃ for cooling to obtain cooling sand;

s3, taking out the cooling sand, heating to 160 ℃, adding 40kg of the binder obtained in the preparation example 4 and 1kg of calcium stearate, stirring and mixing uniformly, and cooling to obtain a mixture;

and S4, crushing the mixture, and screening the crushed mixture by a 30-mesh screen to obtain the precoated sand.

Example 2

The preparation process of the precoated sand comprises the following steps:

s1, weighing 600kg of 80-mesh quartz sand, and roasting at 900 ℃ for 4-6 h;

s2, placing the quartz sand obtained in the step S1 in an environment with the temperature of minus 30 ℃ for cooling to obtain cooling sand;

s3, taking out the cooling sand, heating to 180 ℃, adding 60kg of the binder obtained in the preparation example 4 and 2kg of calcium stearate, stirring and mixing uniformly, and cooling to obtain a mixture;

and S4, crushing the mixture, and screening the crushed mixture by a 30-mesh screen to obtain the precoated sand.

Example 3

The preparation process of the precoated sand comprises the following steps:

s1, weighing 550kg of 100-mesh quartz sand, and roasting at 880 ℃ for 5 h;

s2, placing the quartz sand obtained in the step S1 in an environment with the temperature of-20 ℃ for cooling to obtain cooling sand;

s3, taking out the cooling sand, heating to 170 ℃, adding 50kg of the binder obtained in the preparation example 4 and 1.5kg of calcium stearate, uniformly stirring and mixing, and cooling to obtain a mixture;

and S4, crushing the mixture, and screening the crushed mixture by a 30-mesh screen to obtain the precoated sand.

Example 4

The difference from example 3 is that the binder is obtained from preparation example 5.

Example 5

The difference from example 3 is that the binder is obtained from preparation 6.

Example 6

The difference from example 3 is that the binder is obtained from preparation example 7.

Example 7

The difference from example 3 is that the binder is obtained from preparation 8.

Example 8

The difference from example 3 is that the binder is obtained from preparation example 9.

Example 9

The difference from example 3 is that the binder is obtained from preparation example 10.

Example 10

The difference from example 3 is that the binder is obtained from preparation example 11.

Example 11

The difference from example 3 is that the binder is obtained from preparation example 12.

Example 12

The difference from example 3 is that the binder is obtained from preparation 13.

Example 13

The difference from example 3 is that the binder is obtained from preparation example 14.

Example 14

The difference from example 3 is that the binder is obtained from preparation example 15.

Example 15

The difference from example 3 is that the binder is obtained from preparation 16.

Comparative example

Comparative example 1

The difference from example 3 is that epoxidized soybean oil was not added to the binder.

Comparative example 2

The difference from example 3 is that arginine was not added to the binder.

Comparative example 3

The difference from example 3 is that epoxidized soybean oil and arginine were not added to the binder.

Comparative example 4

The difference from example 3 is that the silica sand is not calcined.

Example 5

The difference from example 3 is that in the step of S2, the silica sand is naturally cooled.

Performance test

And (3) gas forming amount detection: the coated sand obtained in examples 1 to 15 and comparative examples 1 to 5 was placed on a gas meter and heated to 200 ℃ and the test data was recorded in table 1.

And (3) detecting the normal-temperature tensile strength: the precoated sand obtained in examples 1 to 15 and comparative examples 1 to 5 was prepared into test pieces by reference to JB/T8583-2008 "precoated sand for casting", and the test pieces were tested for tensile strength at room temperature by a hydraulic strength testing machine, and the test results are detailed in table 1.

Testing the influence of the expansibility of the precoated sand: the coated sand obtained in examples 1 to 15 and comparative examples 1 to 5 was molded into a mold and 50 castings were obtained by casting, and the surface of the castings was observed for the occurrence of cracks, blisters, flaking, veining or orange peel-like defects, and the number of defective castings having the above-mentioned problems was recorded, and the test results are detailed in table 1.

TABLE 1

	Gas evolution volume ml/g	Tensile strength at room temperature MPa	Number of disqualification
				Example 1	18.6	2.3	1
Example 2	18.5	2.4	1
				Example 3	18.5	2.3	1
Example 4	18.4	2.3	1
				Example 5	18.4	2.4	1
Example 6	18.4	2.5	1
				Example 7	18.4	2.5	1
Example 8	18.4	2.0	2
				Example 9	18.3	2.5	1
Example 10	18.2	2.9	1
				Example 11	18.2	3.0	1
Example 12	18.2	3.5	0
				Example 13	18.2	3.5	1
Example 14	18.1	3.6	0
				Example 15	18.2	2.0	2
Comparative example 1	18.4	1.5	4
				Comparative example 2	18.3	1.5	4
Comparative example 3	18.3	1.4	4
				Comparative example 4	27.4	2.2	10
Comparative example 5	24.4	2.3	8

It can be seen from the combination of example 3 and comparative examples 1 to 3 and table 1 that the room temperature tensile strength of the precoated sand was significantly improved by adding epoxidized soybean oil and arginine. The starch and the sucrose are used as bonding components, and the addition of the epoxidized soybean oil and the arginine can better improve the bonding strength of the bonding agent, thereby improving the normal-temperature tensile strength of the precoated sand.

As can be seen by combining example 3 and comparative examples 4 to 5 with Table 1, the gas evolution of the precoated sand was significantly improved without calcining the silica sand. The quartz sand is cooled at low temperature after being roasted, so that the expansion degree of the precoated sand is smaller after being heated, and the quantity of unqualified castings is obviously reduced.

Combining example 3 with examples 6-9 and combining table 1, it can be seen that the room temperature tensile strength of the coated sand is better when the binder is 500-800 mesh.

When example 3 and examples 10 to 11 were combined and table 1 was combined, it was found that the room-temperature tensile strength of the coated sand was significantly improved by adding zeolite.

It can be seen from the combination of example 11 and examples 12 to 14 and from table 1 that the room-temperature tensile strength of the coated sand was further improved by modifying the zeolite with zinc oxide.

Combining example 3 and example 15 with table 1, it can be seen that the quartz powder is not wrapped by the high-viscosity elastomer obtained after the reaction of epoxidized soybean oil and arginine, and is directly mixed with starch, sucrose and dolomite powder to obtain the binder, so that the normal-temperature tensile strength of the precoated sand is obviously reduced.

The present embodiment is only for explaining the present application, and it is not limited to the present application, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present application.