Inorganic binder coated sand and method of making and use

Abstract

The application provides inorganic binder coated sand and a preparation method and application thereof. The inorganic binder coated sand is prepared by mixing modified inorganic regenerated sand, sodium silicate and a catalyst. The specific preparation process of the modified inorganic regenerated sand is as follows: first, inorganic regenerated sand and modified liquid semi-products are prepared by using a wet regeneration method; then, the modified liquid semi-products are treated by pressure filtration; then, the conductivity value of the modified liquid products is adjusted by adding water or inorganic binders; then, the inorganic regenerated sand is added into the modified liquid products for reaction; and finally, the modified inorganic regenerated sand is obtained after drying. The inorganic binder coated sand prepared by the application has good fluidity, high strength and high core production rate, and can be recycled in the use process. The application has a simple process, is suitable for repeated use and low in cost, and is suitable for wide range of popularization and use.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of coated sand for casting, and particularly relates to an inorganic binder coated sand and a preparation method and application thereof. BACKGROUND

[0002] The automobile industry is rapidly developing towards light weight, intelligence and electrification, and the quality requirements for automobile parts are also becoming higher and higher. In addition, in order to achieve the "double carbon" goal, the environmental protection and low carbon technology research and development products for industrial application are gradually being industrialized and marketized. The key parts of new energy vehicles, such as aluminum alloy motor shell and auxiliary frame, are prone to porosity defects. More than half of the porosity defects are caused by the decomposition of organic resin in the molding material at high temperature. However, inorganic binder basically does not produce gas during casting, which can effectively avoid porosity in castings and greatly improve the yield of castings.

[0003] The inorganic binder coated sand is a casting molding material formed by coating inorganic binder as a bonding material (referred to as inorganic sand) and recycled sand as aggregate. According to the investigation of casting enterprises, there are two difficulties in the use of inorganic sand: 1) low strength, which easily causes sand core cracks and core breakage; 2) slow solidification, which easily causes shot nozzle blockage and causes interruption of core making.

[0004] Chinese patent CN 108097866A discloses a method for improving the strength of inorganic binder sand, which adds microsilica powder during the mixing process of inorganic binder sand to improve the strength of inorganic binder sand and solve the problem of collapsibility of inorganic binder sand. However, the addition of microsilica powder has a great negative impact on fluidity, and the yield and other indicators are not mentioned.

[0005] Chinese patent CN114472796A discloses a modified inorganic binder sand with collapsibility and a preparation method, which includes silica sand, modified inorganic binder and powder collapsibility agent, significantly improves the collapsibility of inorganic binder sand, greatly reduces the residual strength of inorganic binder sand after pouring, and is easy to clean the castings. However, the problems of core breakage, cracks, shot nozzle blockage and poor practicability during the use of inorganic binder are not considered. SUMMARY

[0006] Based on this, the application provides an inorganic binder coated sand and a preparation method and application thereof. To achieve the above purpose, the application adopts the following technical scheme:

[0007] An inorganic binder coated sand, in terms of weight parts, includes the following components: modified inorganic recycled sand 100 parts, sodium silicate 1-5 parts, and catalyst 0.1-0.5 parts.

[0008] The preparation of the modified inorganic recycled sand includes the following steps:

[0009] Take inorganic old sand, carry out wet regeneration, and get inorganic regenerated sand and modified liquid semi-product after sand water separation;

[0010] Add flocculants and precipitants to the modified liquid semi-product, carry out pressure filtration after reaction, and test the conductivity of the liquid after pressure filtration, adjust the conductivity value by adding water or sodium silicate to get the modified liquid product;

[0011] Add inorganic regenerated sand to the modified liquid product for reaction, and get modified inorganic regenerated sand after drying;

[0012] The catalyst comprises calcium oxide, butanedione and lecithin.

[0013] Further, the inorganic old sand specification is 40 / 70 mesh, and the three-screen concentration is 85-92%, and the sand-water ratio in wet regeneration is 1: (1-3).

[0014] Further, the flocculant is polymeric ferric sulfate, and the addition amount is 0.01%-0.05%, the precipitant is polyacrylamide, and the addition amount is 0.001-0.002%, and the conductivity value of the modified liquid product is 10000 us / cm-20000 us / cm.

[0015] Further, the proportion of calcium oxide in the catalyst is 10-50%, the proportion of butanedione is 10%-50%, and the proportion of lecithin is 10%-60%.

[0016] A method for preparing the inorganic binder coated sand comprises the following steps:

[0017] Take modified inorganic regenerated sand and sodium silicate, add them to a sand mixer for mixing for 30-80s to get mixed material I;

[0018] Add a catalyst to the mixed material I for mixing for 8-20s to get inorganic binder coated sand.

[0019] The inorganic binder coated sand is applied in automobile part casting.

[0020] Compared with the prior art, the inorganic binder coated sand prepared by the method has the advantages that:

[0021] (1) The inorganic binder coated sand prepared by the method has good fluidity, high strength, and high core making yield, realizes recycling in use process, and has simple process, reusability and low cost.

[0022] (2) The high-concentration circulating water generated in the inorganic old sand regeneration process is proportioned to get modified liquid with a conductivity of 10000 us / cm-20000 us / cm, the inorganic regenerated sand is quickly soaked and dried by using the modified liquid, the inorganic regenerated sand after drying is covered with a layer of highly active sodium silicate inorganic binder, and the modified inorganic regenerated sand is better than new sand;

[0023] (3) The catalyst of this invention is selected from calcium oxide, dimethyl ethyl ketone and lecithin. Calcium oxide can quickly form a highly alkaline environment to greatly improve the curing efficiency. Dimethyl ethyl ketone strengthens the curing reaction and increases the strength. Lecithin effectively promotes the reaction activity and improves the catalytic effect. The combination of the three can effectively improve the yield of sand core. Attached Figure Description

[0024] Figure 1 This is a process flow diagram of Embodiment 1 of the present invention. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to specific embodiments, so that those skilled in the art can more clearly understand the present invention. All materials not specifically described in this invention are existing materials that can be purchased directly from the market.

[0026] Example 1

[0027] like Figure 1 As shown in the figure, this embodiment provides a method for preparing inorganic binder-coated sand, and the specific steps are as follows:

[0028] S1. Take inorganic recycled sand with a specification of 40 / 70 mesh and a three-sieve concentration of 90%, with a sand-to-water ratio of 1:2, and perform wet regeneration by stirring and scrubbing for 5 minutes at a stirring speed of 360 r / min. Then, pass it through a 100-mesh dewatering sieve to separate the sand and water, and obtain inorganic recycled sand and modified liquid semi-finished products.

[0029] S2, add 0.02% polyferric sulfate and 0.001% polyacrylamide to the modified liquid semi-finished product, stir evenly and let stand for 20 minutes, then filter using a filter press, add water or inorganic binder to the filtered liquid, and finally obtain the modified liquid finished product with an electrical conductivity of 15000us / cm.

[0030] S3. The inorganic recycled sand is immersed in the modified liquid product for 10 minutes to complete the surface modification, and then dried to obtain the modified inorganic recycled sand.

[0031] S4. Take 100 parts of modified inorganic recycled sand and 2 parts of sodium silicate, add them to a sand mixer and mix for 50 seconds to obtain mixture I.

[0032] S5, add 0.2 parts of catalyst (20% calcium oxide, 40% dimethyl ethyl ketone, 40% lecithin) to mixture I and mix for 8 seconds to obtain inorganic binder coated sand.

[0033] Example 2

[0034] The embodiment provides a method for preparing inorganic binder coated sand, raw materials and process steps of which are basically same with those of the embodiment 1, and the difference is that the catalyst content is 0.1 parts.

[0035] Embodiment 3

[0036] The embodiment provides a method for preparing inorganic binder coated sand, raw materials and process steps of which are basically same with those of the embodiment 1, and the difference is that the catalyst content is 0.5 parts.

[0037] Embodiment 4

[0038] The embodiment provides a method for preparing inorganic binder coated sand, raw materials and process steps of which are basically same with those of the embodiment 1, and the difference is that specific parameters are different, and the specific parameters are as follows.

[0039] S1, inorganic old sand with a specification of 40 / 70 meshes and a three-screen concentration of 85% is taken, sand-water ratio is 1:1, stirring scrubbing wet regeneration is carried out, time is 5min, stirring speed is 360r / min, sand-water separation is carried out through a 100-mesh dehydration screen, and inorganic regenerated sand and modified liquid semi-finished products are obtained.

[0040] S2, 0.01% of polymeric ferric sulfate and 0.001% of polyacrylamide are added into the modified liquid semi-finished products, after uniform stirring, standing for 20min, pressure filtration is carried out by using a filter press, and finally, the modified liquid finished products with an electric conductivity value of 10000us / cm are obtained by adding water or inorganic binders into the liquid after pressure filtration.

[0041] S3, the inorganic regenerated sand is soaked in the modified liquid finished products for 10min to complete surface modification, and then is dried to obtain modified inorganic regenerated sand.

[0042] S4, 100 parts of modified inorganic regenerated sand and 1 part of sodium silicate are taken and added into a sand mixer for mixing for 30s to obtain mixture I.

[0043] S5, 0.1 catalyst (calcium oxide 10%, butanedione 50% and lecithin 40%) is added into the mixture I for mixing for 15s, and inorganic binder coated sand is obtained.

[0044] Embodiment 5

[0045] The embodiment provides a method for preparing inorganic binder coated sand, raw materials and process steps of which are basically same with those of the embodiment 1, and the difference is that specific parameters are different, and the specific parameters are as follows.

[0046] S1. Take inorganic old sand with a specification of 40 / 70 mesh and a three-sieve concentration of 92%, with a sand-to-water ratio of 1:3, and carry out wet regeneration by stirring and scrubbing for 5 minutes at a stirring speed of 360 r / min. Separate the sand and water by passing it through a 100-mesh dewatering sieve to obtain inorganic regenerated sand and modified liquid semi-finished products.

[0047] S2, add 0.05% polyferric sulfate and 0.002% polyacrylamide to the modified liquid semi-finished product, stir evenly and let stand for 20 minutes, then filter using a filter press, add water or inorganic binder to the filtered liquid to finally obtain the modified liquid finished product with an electrical conductivity of 20000us / cm.

[0048] S3, the inorganic recycled sand is immersed in the modified liquid product for 10 minutes to complete the surface modification, and then dried to obtain the modified inorganic recycled sand;

[0049] S4, take 100 parts of modified inorganic recycled sand and 5 parts of sodium silicate, add them to the sand mixer and mix for 80 seconds to obtain mixture I;

[0050] S5, add 0.5% catalyst (30% calcium oxide, 10% dimethyl ethyl ketone, 60% lecithin) to mix I and mix for 20 seconds to obtain inorganic binder sand.

[0051] Comparative Example 1

[0052] This comparative example provides a method for preparing inorganic binder-coated sand, which uses the same raw materials and process steps as in Example 1, with the following specific differences: Inner Mongolian new sand is used instead of modified inorganic recycled sand.

[0053] Comparative Example 2

[0054] This comparative example provides a method for preparing inorganic binder-coated sand, which uses basically the same raw materials and process steps as in Example 1, except that the inorganic recycled sand is not modified. The specific operation is as follows:

[0055] S1. Take inorganic old sand with a specification of 40 / 70 mesh and a three-screen concentration of 90%, with a sand-to-water ratio of 1:2, and perform wet regeneration by stirring and scrubbing for 5 minutes at a stirring speed of 360 r / min. Then, pass it through a 100-mesh dewatering screen to separate the sand and water to obtain inorganic regenerated sand.

[0056] S2, take 100 parts of inorganic recycled sand and 2 parts of sodium silicate, add them to the sand mixer and mix for 50 seconds to obtain mixture I;

[0057] S3, add 0.2% catalyst (20% calcium oxide, 40% dimethyl ethyl ketone, 40% lecithin) to mixture I and mix for 8 seconds to obtain inorganic binder sand.

[0058] Comparative Example 3

[0059] The comparative example provides a method for preparing inorganic binder coated sand, which uses the same raw materials and process steps as in Example 1, with the following differences: the conductivity of the modified liquid product is 500 us / cm.

[0060] Comparative Example 4

[0061] The comparative example provides a method for preparing inorganic binder coated sand, which uses the same raw materials and process steps as in Example 1, with the following differences: the conductivity of the modified liquid product is 30000 us / cm.

[0062] Comparative Example 5

[0063] The comparative example provides a method for preparing inorganic binder coated sand, which uses the same raw materials and process steps as in Example 1, with the following differences: no catalyst is added, and the inorganic binder coated sand is prepared directly using modified inorganic reclaimed sand and sodium silicate.

[0064] Comparative Example 6

[0065] The example provides a method for preparing inorganic binder coated sand, which uses the same raw materials and process steps as in Example 1, with the following differences: the inorganic binder is replaced by sodium phosphate instead of sodium silicate.

[0066] The properties of the coated sand prepared in Examples 1-3 and Comparative Examples 1-6 were identified, including tensile strength, flowability, and curing thickness, which were tested according to the standard JB / T8583-2008.

[0067] Table 1: Physicochemical properties of coated sand

[0068]

[0069] As shown in Table 1:

[0070] Comparing Example 1 with Comparative Example 1, after replacing the modified inorganic reclaimed sand with Inner Mongolia new sand, the strength of the coated sand decreased by 35%, the flowability increased by 20%, the curing thickness decreased by 10%, and the core production rate decreased by 6 percentage points.

[0071] Comparing Example 1 with Comparative Example 2, after omitting the modification process of inorganic reclaimed sand, the strength of the inorganic sand decreased by 25%, the flowability increased by 30%, the curing thickness decreased by 10%, and the core production rate decreased by 8 percentage points.

[0072] Comparing Example 1 with Comparative Example 3, after the conductivity of the modified liquid product was as low as 500 us / cm, the strength of the inorganic sand decreased by 15%, the flowability increased by 15%, the curing thickness decreased by 15%, and the core production rate decreased by 5 percentage points.

[0073] Comparative example 1 and the comparative example 4, the modified liquid conductivity is high to 30000us / cm, the strength of the inorganic sand obtained is increased by 5%, the fluidity is prolonged by 35%, the curing thickness is increased by 10%, and the core production rate is reduced by 10 percentage points.

[0074] Comparative example 1 and the comparative example 5, when no catalyst is added, the strength of the inorganic sand obtained is decreased by 15%, the fluidity is prolonged by 5%, the curing thickness is decreased by 35%, and the core production rate is reduced by 3 percentage points.

[0075] Comparative example 1 and the comparative example 6, when the inorganic binder is replaced by sodium phosphate instead of sodium silicate, the strength of the inorganic sand obtained is decreased by 20%, the fluidity is prolonged by 11%, the curing thickness is decreased by 6%, and the core production rate is reduced by 47 percentage points.

[0076] It is found by comparing examples 1-3 that when the amount of catalyst added is small, curing is slow, and the strength is low; and when the amount of catalyst added is too much, curing is too early, the binder is ineffective, and there is floating sand and loose sand on the surface of the sand core.

[0077] In summary, the inorganic binder coated sand prepared in the application is excellent in cold strength, fluidity, curing thickness, and core production rate, and is suitable for large-scale production and application.

[0078] The above is only a preferred embodiment of the application, and is not used to limit the protection scope of the application. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the application should be included in the protection scope of the application.

Claims

1. An inorganic binder coated sand characterized by, By weight, including the following components: modified inorganic reclaimed sand 100 parts, sodium silicate 1-5 parts, catalyst 0.1-0.5 parts; The preparation of the modified inorganic reclaimed sand comprises the following steps: Take inorganic old sand, wet regeneration, sand water separation, and get inorganic reclaimed sand and modified liquid semi-finished product; Add flocculating agent and precipitating agent to the modified liquid semi-finished product, filter after reaction, and test the conductivity of the filtered liquid, adjust the conductivity value by adding water or sodium silicate to get modified liquid finished product; Add inorganic reclaimed sand to the modified liquid finished product, react, dry, and get modified inorganic reclaimed sand; The catalyst comprises calcium oxide, butanedione and lecithin; The conductivity value is 10000us / cm-20000us / cm; The proportion of calcium oxide in the catalyst is 10-50%, the proportion of butanedione is 10%-50%, and the proportion of lecithin is 10%-60%.

2. The inorganic bonded coated sand of claim 1, wherein, The specification of the inorganic old sand is 40 / 70 mesh, and the three-screen concentration is 85-92%. The sand-water ratio in wet regeneration is 1: (1-3).

3. The inorganic bonded coated sand of claim 1, wherein, The flocculating agent is polymeric ferric sulfate, and the addition amount is 0.01%-0.05%. The precipitating agent is polyacrylamide, and the addition amount is 0.001-0.002%.

4. A method of producing the inorganic binder coated sand according to any one of claims 1 to 3, characterized by, Comprise the following steps: Take modified inorganic reclaimed sand and sodium silicate, add to the sand mixer and mix for 30-80s to get mixed material I; Add catalyst to mixed material I and mix for 8-20s to get inorganic binder coated sand.

5. The application of the inorganic binder coated sand of any one of claims 1-3 in automobile part casting.

Images