CN108188339B - Precoated sand for casting with sintering resistance and low expansion performance - Google Patents
Precoated sand for casting with sintering resistance and low expansion performance Download PDFInfo
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- CN108188339B CN108188339B CN201711489945.4A CN201711489945A CN108188339B CN 108188339 B CN108188339 B CN 108188339B CN 201711489945 A CN201711489945 A CN 201711489945A CN 108188339 B CN108188339 B CN 108188339B
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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
- 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
- B22C1/02—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by additives for special purposes, e.g. indicators, breakdown additives
Abstract
The invention discloses precoated sand with sintering resistance and low expansion performance for casting, which is prepared from the following raw materials in parts by mass: 100 parts of aggregate sand, 0.8-3.5 parts of resin, 0.2-5 parts of composite additive, 0-0.5 part of water, 0-1 part of urotropine and 0-0.5 part of calcium powder; the composite additive comprises the following raw material components in parts by weight: 100 parts of silicon micropowder, 1-10 parts of superfine alumina powder, 1-15 parts of spherical ceramic powder, 4-50 parts of reducing additive and 0.1-10 parts of composite high polymer material. Compared with the conventional precoated sand, the precoated sand has the excellent performances of higher (better) melting point, high-temperature fluidity, high-temperature compressive strength, anti-caking rate, low expansion rate, expansion behavior, high-temperature resistant time and the like.
Description
Technical Field
The invention belongs to the technical field of precoated sand, and particularly relates to precoated sand for casting, which has sintering resistance and low expansion performance.
Background
The resin coated sand is one of main auxiliary materials in the casting industry. In the casting process, resin coated sand is used for preparing sand cores, assembling cores and pouring to achieve the purpose of preparing castings.
The resin coated sand for casting is compounded by refractory aggregate and high molecular resin, the resin coated sand is heated in a mould to generate a curing reaction during core making, the granular coated sand is consolidated into a sand core with a certain shape, and the single sand core is combined or independently used for casting into a metal casting. The casting is divided into non-ferrous metal casting and ferrous metal casting according to different material types, the pouring temperature of the non-ferrous metal casting is low, the pouring temperature of cast aluminum in the non-ferrous metal casting is usually 700 ℃, the pouring temperature of cast copper is about 1250 ℃, the pouring temperature of cast iron in the ferrous metal casting is 1320-1450 ℃, and the pouring temperature of cast steel is higher and usually reaches above 1450-1530 ℃, so when resin coated sand is used as a molding sand material, the high-temperature resistance is required.
The high temperature resistance of the resin coated sand for ferrous metal casting needs to have the characteristics of low high temperature expansibility of the prepared sand core, relatively slow resin thermochemical reaction under high temperature condition to relatively high carbon residue, fracture resistance under high temperature condition, sand core integrity under high temperature condition, high temperature sand adhesion resistance, high coated sand melting point and the like besides the basic characteristics (instant strength, fluidity, melting point, normal temperature strength, gas forming amount and gas forming rate) required by engineering.
The high temperature characteristic detection method of the resin-coated sand for casting generally comprises the steps of preparing the resin-coated sand into a standard sample block, judging by testing the size change of the sample block under the constant temperature condition of 1000 ℃, the integrity of the sample block after the thermochemical reaction and the duration of fracture or breakage, and generally adopting phenolic resin with higher molecular weight and using aggregate with higher refractoriness (such as quartz sand, ceramsite sand, white corundum sand, mullite sand and the like with high silicon content) to improve the high temperature resistance from the material perspective in order to achieve good high temperature resistance. Some inorganic additives (such as albite, potash feldspar, anorthite, iron oxide powder and the like) with a slightly lower content than the aggregate are also added during the preparation of the resin-coated sand, and organic additive materials (such as silane, flame retardant, plasticizer and the like) are used for achieving the purpose of improving the high-temperature resistance. However, the high temperature resistance of the precoated sand is still poor after inorganic additives or organic additives are added in the existing method.
Disclosure of Invention
The invention aims to provide the precoated sand for casting, which has sintering resistance and low expansion performance, and has higher (better) melting point, high-temperature fluidity, high-temperature compressive strength, caking resistance, low expansion rate, expansion behavior, high-temperature resistant time and other excellent performances compared with the conventional precoated sand.
In order to achieve the above purpose, the basic scheme of the invention is as follows:
the precoated sand for casting with sintering resistance and low expansion performance comprises the following raw materials in parts by mass: 100 parts of aggregate sand, 0.8-3.5 parts of resin, 0.2-5 parts of composite additive, 0-0.5 part of water, 0-1 part of urotropine and 0-0.5 part of calcium powder; the composite additive comprises the following raw material components in parts by weight: 100 parts of silicon micropowder, 1-10 parts of superfine alumina powder, 1-15 parts of spherical ceramic powder, 4-50 parts of reducing additive and 0.1-10 parts of composite high polymer material.
The invention also provides a preparation method of the precoated sand for casting, which has the sintering resistance and low expansion performance, and comprises the following steps:
(1) heating 100 parts of sand to 110-230 ℃;
(2) adding 0.8-3.5 parts of resin and 0.2-5 parts of composite additive;
(3) adding 0-0.5 part of water;
(4) adding 0-1 part of urotropin;
(5) blowing air to cool for 40-80 s;
(6) adding 0-0.5 part of calcium powder, mixing uniformly and then sanding.
In the resin coated sand of this scheme, added 0.2 ~ 5 parts of composite additive, the resin coated sand that enables to prepare and obtain has following advantage:
1. the addition of the composite additive improves the total normal-temperature film hardness of the resin, reduces the relative friction coefficient and the heating melting rate of the coated sand grains, improves the melting point of the coated sand and the capability of being sent to the far end of the inner cavity in a high-temperature mould, and simultaneously improves the compactness and the surface finish of the sand core;
2. the sintering property of the mixture of the inorganic oxides of the composite additive is utilized when the mixture is subjected to the action of high temperature (600-2000 ℃), so that the high-temperature compressive strength of the mixture is improved;
3. the addition of the composite additive improves the total normal-temperature film hardness of the resin and reduces the heating melting rate, so that the prepared resin-coated sand has better caking resistance;
4. the reductive component of the composite additive can slow down the thermal cracking reaction of the coated sand resin film when the coated sand resin film is subjected to high temperature (600-2000 ℃);
5. the graphite in the additive has high heat transfer coefficient, so that the high temperature on the surface of the sand core is accelerated to be quickly transmitted to the inner layer of the sand core, the temperature rise rate of the surface of the sand core is reduced, the attenuation of the high-temperature strength of the sand core is slowed down, the expansion rate of the sand core is reduced, the expansion behavior of the sand core is changed, the maximum expansion time is prolonged, and the occurrence probability of expansion defects is favorably reduced;
6. because the silicon-aluminum oxide in the additive is subjected to thermochemical reaction sintering under the coordination of other components to form a layer of inorganic film, the high-temperature strength of resin carbonization loss is reinforced, and meanwhile, the capability of the sand core for bearing metal liquid pressure and shearing force in a high-temperature environment is greatly improved, namely, the high-temperature deformation of the sand core of the resin coated sand is reduced, and the high-temperature resistance is improved.
Further, 100 parts of aggregate sand, 2 parts of resin, 1.2 parts of a composite additive, 0.1 part of water, 0.3 part of urotropine and 0.1 part of calcium powder. The inventor finds in experiments that the precoated sand prepared by adopting the components in the proportion has better comprehensive performance.
Further, 1-8 parts of superfine alumina powder, 2-9 parts of spherical ceramic powder, 5-20 parts of reducing additive and 0.5-6 parts of composite high polymer material. The inventors found in experiments that the performance of the resin-coated sand prepared by using the composite additive in the above content range is more excellent.
Further, the composite additive is prepared by adopting the following steps:
(1) a preparation step, namely preparing 100 parts of silica micropowder, 1-10 parts of superfine alumina powder, 1-15 parts of spherical ceramic powder, 4-50 parts of reducing additive and 0.1-10 parts of composite high polymer material, and respectively drying the silica micropowder and the superfine alumina powder;
(2) screening, namely screening the raw materials prepared in the step (1) respectively, and controlling the particle size of the silicon micro powder to be 38-110 microns, the particle size of the superfine alumina powder to be 40-60 microns, the particle size of the spherical ceramic powder to be 0.5-100 microns, the particle size of the reducing additive to be 40-80 microns, and the particle size of the composite polymer material to be 100-180 microns;
(3) mixing, namely respectively loading the raw materials into a powder mixer, controlling the rotation speed of the powder mixer to be 8-50 r/min, mixing for 5-120 min, and discharging after the mixing is finished;
(4) crushing and screening, namely crushing and screening the material mixed in the step (3), and controlling the content of more than 4 meshes to be less than or equal to 2 percent and the content of more than 10 meshes to be less than or equal to 10 percent;
(5) and packaging the screened raw materials of the screened part to obtain a finished product of the composite additive.
Further, the reducing additive comprises a mixture of graphite powder and metal salt substances, and the mass ratio of the graphite powder to the metal salt substances is 1: 0.5-1: 6.5.
Further, the composite high polymer material comprises a mixture of a surfactant and silicone, and the mass ratio of the surfactant to the silicone is 50: 1-5: 1.
Further, the pH value of a 1% aqueous solution of the composite polymer material is 3-10.
Further, SiO in the silicon micropowder
2The content of the silicon micro powder is more than 80 percent, and the average grain diameter of the silicon micro powder is less than 75 mu m.
Further, the heating temperature in the step (1) of the preparation method is 128-150 ℃.
Detailed Description
The following is further detailed by way of specific embodiments:
the following will describe in detail by taking example 1 as an example, and other examples are shown in the table, and the portions not shown in the table are the same as those of example 1.
The inventor of the invention finds in experiments that the anti-sintering and low-expansion performance of the precoated sand is mainly realized by adding the composite additive, so in the following examples, the content change of the composite additive is mainly compared, the raw material components except the composite additive and the treatment process are not separately compared, and the content range of each component and the treatment process parameter range disclosed in the scheme can solve the technical problem of the invention.
The aggregate sand used in the following embodiments may be one or a mixture of several of raw sand, reclaimed sand, baozhu sand, ceramsite sand and chromite.
Example 1
The precoated sand for casting with sintering resistance and low expansion performance comprises the following raw materials in parts by mass: 100 parts of aggregate sand, 2 parts of resin, 1.2 parts of composite additive, 0.1 part of water, 0.3 part of urotropine and 0.2 part of calcium powder; the composite additive comprises the following raw material components in parts by weight: 100 parts of silicon micropowder, 1 part of superfine alumina powder, 1 part of spherical ceramic powder, 4 parts of reducing additive and 0.1 part of composite high polymer material.
The reducing additive comprises a mixture of graphite powder and metal salt substances, the mass ratio of the graphite powder to the metal salt substances is 1: 0.5-1: 6.5, and the mass ratio of the graphite powder to the metal salt substances in the embodiment is 1: 3. The graphite powder comprises soil, water ink and scale graphite; the metal salt compounds include sodium carbonate, ferrous carbonate, soda, baking soda, calcium carbonate, calcium bicarbonate, magnesium carbonate, potassium carbonate, and other carbonate or mineral containing carbonate, alone or in combination.
The composite high polymer material comprises a mixture of a surfactant and silicone, wherein the mass ratio of the surfactant to the silicone is 50: 1-5: 1, and the mass ratio of the surfactant to the silicone in the embodiment is 10: 1.
The precoated sand for casting with sintering resistance and low expansion performance of the embodiment is prepared by the following steps:
(1) heating 100 parts of aggregate sand to 110-230 ℃, wherein the heating temperature is 130 ℃;
(2) adding 2 parts of resin and 1.2 parts of composite additive at the same time;
(3) adding 0.1 part of water;
(4) adding 0.3 part of urotropin;
(5) blowing air to cool for 60 seconds;
(6) adding 0.2 part of calcium powder, mixing uniformly and then discharging sand.
In this example, the composite additive was prepared by the following steps:
(1) a preparation process, namely preparing 100 parts of silicon micropowder, 1 part of superfine alumina powder, 1 part of spherical ceramic powder, 4 parts of reducing additive and 0.1 part of composite high polymer material, and respectively drying the silicon micropowder and the superfine alumina powder;
(2) screening, namely screening the raw materials prepared in the step (1) respectively, and controlling the particle size of the silicon micro powder to be 38-110 microns, the particle size of the superfine alumina powder to be 40-60 microns, the particle size of the spherical ceramic powder to be 0.5-100 microns, the particle size of the reducing additive to be 40-80 microns, and the particle size of the composite polymer material to be 100-180 microns;
(3) mixing, namely respectively loading the raw materials into a powder mixer, controlling the rotation speed of the powder mixer to be 8-50 r/min, mixing for 5-120 min, and discharging after the mixing is finished;
(4) crushing and screening, namely crushing and screening the material mixed in the step (3), and controlling the content of more than 4 meshes to be less than or equal to 2 percent and the content of more than 10 meshes to be less than or equal to 10 percent;
(5) and packaging the screened raw materials of the screened part to obtain a finished product of the composite additive.
In examples 1 to 6 of the present invention, the contents of the components in the composite additive were different, and are specifically shown in table 1:
TABLE 1
Comparative example 1 is precoated sand prepared without adding an additive for precoated sand, and the properties of immediate bending resistance, normal temperature bending resistance, melting point, high temperature fluidity and the like of the precoated sand prepared by adding each of the above examples and comparative examples were respectively tested to obtain the following test results:
TABLE 2
From the above table, examples 1 to 6 are all the precoated sand prepared after the compound additive is used, and comparative example 1 is the precoated sand prepared without the compound additive, and it can be seen from the test results that the normal temperature bending resistance, the melting point, the high temperature fluidity, the high temperature compressive strength, the caking rate, the maximum expansion time and the high temperature time resistance of the precoated sand in examples 1 to 6 are all obviously superior to those without the compound additive.
The above description is only an example of the present invention and common general knowledge of known features in the schemes is not described herein. It should be noted that, for those skilled in the art, without departing from the concept of the present invention, several variations and modifications can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the utility of the patent. The scope of the claims of the present application shall be determined by the contents of the claims, and the description of the embodiments and the like in the specification shall be used to explain the contents of the claims.
Claims (10)
1. The precoated sand for casting with sintering resistance and low expansion performance is characterized by comprising the following raw materials in parts by mass: 100 parts of aggregate sand, 0.8-3.5 parts of resin, 0.2-5 parts of composite additive, 0-0.5 part of water, 0-1 part of urotropine and 0-0.5 part of calcium powder;
the composite additive comprises the following raw material components in parts by weight: 100 parts of silicon micropowder, 1-10 parts of superfine alumina powder, 1-15 parts of spherical ceramic powder, 4-50 parts of reducing additive and 0.1-10 parts of composite high polymer material.
2. The precoated sand for casting having sintering resistance and low expansion performance according to claim 1, wherein the precoated sand comprises 100 parts of aggregate sand, 2 parts of resin, 1.2 parts of composite additive, 0.1 part of water, 0.3 part of urotropine and 0.1 part of calcium powder.
3. The precoated sand for casting having sintering resistance and low expansion performance according to claim 1, wherein the precoated sand comprises 1-8 parts of ultrafine alumina powder, 2-9 parts of spherical ceramic powder, 5-20 parts of a reducing additive and 0.5-6 parts of a composite polymer material.
4. The precoated sand for casting with sintering resistance and low expansion performance according to claim 1, wherein the composite additive is prepared by adopting the following steps:
(1) a preparation step, namely preparing 100 parts of silica micropowder, 1-10 parts of superfine alumina powder, 1-15 parts of spherical ceramic powder, 4-50 parts of reducing additive and 0.1-10 parts of composite high polymer material, and respectively drying the silica micropowder and the superfine alumina powder;
(2) screening, namely screening the raw materials prepared in the step (1) respectively, and controlling the particle size of the silicon micro powder to be 38-110 microns, the particle size of the superfine alumina powder to be 40-60 microns, the particle size of the spherical ceramic powder to be 0.5-100 microns, the particle size of the reducing additive to be 40-80 microns, and the particle size of the composite polymer material to be 100-180 microns;
(3) mixing, namely respectively loading the raw materials into a powder mixer, controlling the rotation speed of the powder mixer to be 8-50 r/min, mixing for 5-120 min, and discharging after the mixing is finished;
(4) crushing and screening, namely crushing and screening the material mixed in the step (3), and controlling the content of more than 4 meshes to be less than or equal to 2 percent and the content of more than 10 meshes to be less than or equal to 10 percent;
(5) and packaging the screened raw materials of the screened part to obtain a finished product of the composite additive.
5. The precoated sand for casting having sintering resistance and low expansion performance according to claim 1, wherein the reducing additive comprises a mixture of graphite powder and a metal salt substance, and the mass ratio of the graphite powder to the metal salt substance is 1: 0.5-1: 6.5.
6. The precoated sand for casting having sintering resistance and low expansion performance according to claim 1, wherein the composite polymer material comprises a mixture of a surfactant and silicone, and the mass ratio of the surfactant to the silicone is 50: 1-5: 1.
7. The precoated sand for casting having sintering resistance and low swelling properties according to any one of claims 1 to 6, wherein a 1% aqueous solution of the composite polymer material has a pH of 3 to 10.
8. The foundry coated sand having sintering resistance and low expansion properties according to any one of claims 1 to 6, wherein SiO is contained in the fine silica powder
2The content of the silicon micro powder is more than 80 percent, and the average grain diameter of the silicon micro powder is less than 75 mu m.
9. The method for preparing the precoated sand for casting having the sintering resistance and the low expansion property according to any one of claims 1 to 6, characterized by comprising the steps of:
(1) heating 100 parts of aggregate sand to 110-230 ℃;
(2) adding 0.8-3.5 parts of resin and 0.2-5 parts of composite additive;
(3) adding 0-0.5 part of water;
(4) adding 0-1 part of urotropin;
(5) blowing air to cool for 40-80 s;
(6) adding 0-0.5 part of calcium powder, mixing uniformly and then sanding.
10. The method for preparing precoated sand for casting having sintering resistance and low expansion property according to claim 9, wherein the heating temperature in step (1) is 128 to 150 ℃.
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| CN110216237B (en) * | 2019-07-25 | 2020-12-29 | 盐城仁创砂业科技有限公司 | Additive for steel casting precoated sand and preparation method and application thereof |
| CN112589042A (en) * | 2020-12-10 | 2021-04-02 | 含山县朝霞铸造有限公司 | Additive for steel casting precoated sand and preparation method and application thereof |
| CN113770297B (en) * | 2021-09-09 | 2023-04-28 | 合肥仁创铸造材料有限公司 | Self-heat-absorption precoated sand and preparation method thereof |
| CN113857421B (en) * | 2021-09-29 | 2023-02-14 | 江西特欣实业有限公司 | Preparation method and application of wet precoated sand |
| CN117510510B (en) * | 2024-01-08 | 2024-03-19 | 中北大学 | Preparation method of Sha Zhuang urotropine difficult to agglomerate |
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| CN106563765A (en) * | 2016-11-03 | 2017-04-19 | 重庆长江造型材料（集团）股份有限公司 | Low-ammonia environment-friendly resin coated sand |
| CN106807881A (en) * | 2017-02-06 | 2017-06-09 | 柳州市柳晶科技有限公司 | Casting precoated sand and its manufacture method |
| CN107377865A (en) * | 2017-08-07 | 2017-11-24 | 伊婕 | A kind of novel film coating sand and preparation method thereof |
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