Method for improving performance of amine cold-box process

Abstract

A method for improving the performance of an amine cold-box process. For a sand core prepared by means of an amine cold-box process, a heat treatment procedure is added subsequent to the preparation procedure, so that the sand core is heat-treated for a period of time within half an hour after the completion of sand core preparation. The method can improve the strength of products, and reduce the gas evolution of sand cores.

Description

A method for improving the performance of amine-based cold cores Technical Field

[0001] This invention relates to the field of casting technology, and in particular to a method for improving the performance of amine-process cold cores. Background Technology

[0002] The amine-based cold core process mainly utilizes phenolic resin (component I) and polyisocyanate (component II) as a two-component binder, and through the catalytic action of triethylamine, the sand core is rapidly cured at room temperature.

[0003] However, the sand cores obtained by this method have the following problems:

[0004] (1) If the strength of the sand core does not meet the requirements when the resin type and sand are determined, the strength of the sand core must be increased by increasing the amount of resin added. This will cause the sand injection pressure to increase, which will aggravate the sand core sticking to the mold and reduce the service life of the core box. The core sand fluidity will decrease, which will affect the quality of the sand core. The sand core gas generation will increase, which may cause defects such as porosity and leakage in the casting.

[0005] (2) The sand cores produced generally need to be left for a certain period of time to build up sufficient strength before they can be repaired and poured. Otherwise, some sand cores will have low strength, and the castings will deform or break after pouring.

[0006] (3) After the sand core is coated with water-based paint and dried, the strength of the sand core is reduced, and there will be core breakage after casting. Summary of the Invention

[0007] Based on the above problems, the purpose of this invention is to provide a method for improving the performance of amine-process cold cores, which can increase the strength of sand core products.

[0008] To overcome the shortcomings of the prior art, the technical solution provided by this invention is as follows:

[0009] A method for improving the performance of amine-process cold cores involves adding a heat treatment step after the preparation process for sand cores prepared by the amine-process cold core process, wherein the sand core is heat-treated for a period of time within half an hour after the sand core preparation is completed.

[0010] In one embodiment, the core heat treatment temperature is 120–200°C and the treatment time is 20–60 min.

[0011] In one embodiment, the core heat treatment temperature is 150°C and the treatment time is 40 minutes.

[0012] In one embodiment, a forced-air drying oven is used for heat treatment.

[0013] In one embodiment, the sand core is supported by a bracket and placed in the blower drying oven for heat treatment.

[0014] In one embodiment, during the preparation of the sand core, the blower drying oven is turned on in advance, the heating temperature is set, and after the temperature stabilizes, the prepared sand core is placed in the blower drying oven for heat treatment.

[0015] Compared with the prior art, the advantages of the present invention are:

[0016] 1. The sand core is prepared using the amine cold core process. The sand core is then heat-treated within half an hour of preparation. This treatment intensifies the thermal motion of the resin molecules, allowing more active groups to come into contact and react, resulting in a more complete curing reaction and the formation of a more perfect cross-linked network structure. This improves the strength of the sand core by about 10%, while reducing the gas evolution of the sand core and avoiding the adverse consequences of increasing the amount of resin added.

[0017] 2. For sand cores that originally did not require increased resin addition, the amount of single-component resin added can be reduced by 0.05% to 0.1% after heat treatment, while still meeting the requirements for sand core use.

[0018] 3. After heat treatment, the sand cores are coated with a paint while hot and then dried, which can improve the final tensile strength of the sample. Detailed Implementation

[0019] The above-described solution will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. The implementation conditions used in the embodiments may be further adjusted according to the conditions of specific manufacturers, and the implementation conditions not specified are generally those in routine experiments.

[0020] Example 1

[0021] In the laboratory, artificial sand was mixed using recycled lake sand with a particle size of 50 / 100. The cold core resin addition was 0.45% (phenolic resin content) + 0.45% (polyisocyanate content). Sand was shot to prepare standard "figure-eight" specimens. For specimens requiring heat treatment, they were placed on a support. Immediately after sample preparation, the support was placed in a forced-air drying oven with different set temperatures for 20 min, 40 min, and 60 min, respectively.

[0022] During the sand core preparation process, the forced-air drying oven is turned on in advance, the heating temperature is set, and after the temperature stabilizes, the prepared sand core is placed in the forced-air drying oven for heat treatment.

[0023] After heat treatment, the samples were placed in a laboratory environment. According to the national standard GB / T 2684-2009, Test Methods for Foundry Sand and Mixtures, the final tensile strength of each sample was tested using an intelligent strength tester. At least five data points were measured for each sample. After removing the maximum and minimum values, the average value was calculated. The final tensile strength data and comparisons are shown in Table 1.

[0024] Table 1 Comparison of final tensile strength

[0025] As can be seen from Table 1, the final strength is basically the highest when the heat treatment temperature is 150℃ and the heat treatment time is 40min. The final strength under this heat treatment condition is 11.1% higher than the strength without heat treatment. The improvement in final tensile strength is not significant when the heat treatment is 60min. Based on the principle of economy, the heat treatment temperature is 150℃ and the heat treatment time is 40min.

[0026] Table 2 shows the comparison of 24-hour gas output. As can be seen from Table 2, the 24-hour gas output decreased by 10.8%.

[0027] Table 2 Comparison of 24-hour gas production

[0028] Example 2

[0029] Regenerated lake sand with a particle size of 50 / 100 was used for verification using a collapsible core box (containing an "8" sample). When the sand core was not heat-treated, the resin addition was 0.55% (phenolic resin content) + 0.55% (polyisocyanate content). When the core and the "8" sample were heat-treated at 150℃ for 40min, the resin addition was 0.5% (phenolic resin content) + 0.5% (polyisocyanate content). The specific comparison is shown in Table 3.

[0030] Table 3 Comparison of sample strengths with different resin addition amounts

[0031] The amount of single-component resin added to the heat-treated sample was reduced by 0.05%, but the strength was comparable to the final strength of the untreated sample with 0.55% (phenolic resin content) + 0.55% (polyisocyanate content), and the quality of the core-making and collapsible samples were both qualified.

[0032] It can be seen that the core strength of the inner core and the figure-eight sample was improved after heat treatment at 150℃ for 40min, so the amount of single-component resin added can be reduced by 0.05%.

[0033] Example 3

[0034] Two types of samples were prepared using recycled lake sand with a particle size of 50 / 100: one with 0.6% (phenolic resin content) + 0.6% (polyisocyanate content) cold core resin and 0.3% anti-veining agent; and the other with 0.55% (phenolic resin content) + 0.55% (polyisocyanate content) cold core resin and 0.3% anti-veining agent. The final tensile strength of the samples coated immediately after core preparation and the samples coated hot after heat treatment were tested. Specific data are shown in Table 4.

[0035] Table 4 Final tensile strength after coating is applied directly after core making and after hot coating is applied following heat treatment.

[0036] It is evident that applying a coating to the sand core sample in a hot state after heat treatment can improve the final tensile strength of the product.

[0037] The above examples are merely illustrative of the technical concept and features of the present invention, intended to enable those skilled in the art to understand the content of the invention and implement it accordingly, and should not be construed as limiting the scope of protection of the present invention. All equivalent transformations or modifications made according to the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for improving the performance of amine-based cold cores, characterized in that: For sand cores prepared by the amine cold core process, a heat treatment step is added after the preparation process. The sand core is heat treated for a period of time within half an hour after the preparation is completed.

2. The method for improving the performance of amine-based cold cores according to claim 1, characterized in that: The temperature for heat treatment of sand cores is 120–200℃, and the treatment time is 20–60 min.

3. The method for improving the performance of amine-based cold cores according to claim 2, characterized in that: The core heat treatment temperature was 150℃, and the treatment time was 40 minutes.

4. The method for improving the performance of amine-based cold cores according to claim 1, characterized in that: Heat treatment was performed using a forced-air drying oven.

5. The method for improving the performance of amine-based cold cores according to claim 4, characterized in that: The sand core is supported by a bracket and placed in the blower drying oven for heat treatment.

6. The method for improving the performance of amine-based cold cores according to claim 5, characterized in that: During the preparation of the sand core, the drying oven is turned on in advance, the heating temperature is set, and after the temperature stabilizes, the prepared sand core is placed in the drying oven for heat treatment.

Images