Model and method for evaluating influence of precoated sand and coating thereof on surface quality of casting

Abstract

The invention discloses a model and method for evaluating the influence of precoated sand and coating thereof on the surface quality of a casting, and the model comprises an upper matrix sand mold, a middle matrix sand mold and a lower matrix sand mold; a sprue is formed in the upper base body sand mold; the bottom of the straight pouring gate is communicated with a plurality of transverse pouring gates; a plurality of vertically distributed ingates are arranged in the middle matrix sand mold, and the tops of the ingates are communicated with the tail ends of the cross gates; a plurality of cavities are formed in the lower base body sand mold, standard cylindrical precoated sand core samples are placed in the cavities, and the cavities are opposite to the bottoms of the ingates and communicate with the bottoms of the ingates; and the upper base body sand mold, the middle base body sand mold and the lower base body sand mold are sequentially fastened from top to bottom. According to the method, the influence of different precoated sand coatings and processes thereof on the surface quality of the casting can be quickly, accurately and intuitively evaluated.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of casting, more particularly to a model and method for evaluating the influence of coated sand and its coating on the surface quality of castings. BACKGROUND

[0002] In the field of casting, coated sand cores are widely used to form complex internal cavity structures of castings. In order to further improve the surface quality of castings and prevent defects such as sand sticking and porosity, a layer of refractory coating is usually applied on the surface of the sand core. The type of coating (such as zirconium powder, graphite powder, etc.), the application method (such as dipping, spraying, brushing), and the post-application treatment process (such as surface drying temperature and time) are all key factors affecting the performance of the final coating, which directly determines the surface quality of the casting.

[0003] Currently, the industry relies mostly on macroscopic inspection of the final casting or experience accumulation in actual production to evaluate the effect of the coating, lacking a scientific, efficient, and quantitative front-end testing method. The traditional evaluation method has obvious drawbacks: 1) high trial and error cost; a complete casting pouring must be performed to obtain the results, which is time-consuming and wastes materials; 2) poor comparability; due to fluctuations in parameters such as melting process and pouring temperature, it is difficult to perform fair and scientific horizontal comparison of different batches and different conditions; 3) many interference factors; the surface quality of the casting is the result of the combined action of multiple factors, and the traditional method is difficult to isolate the influence of the single variable "application process" for independent evaluation.

[0004] Therefore, it is an urgent problem for those skilled in the art to develop a model and method that can quickly, accurately, and intuitively evaluate the influence of different coated sand coatings and their processes on the surface quality of castings. SUMMARY

[0005] Therefore, the present application provides a model and method that can quickly, accurately, and intuitively evaluate the influence of different coated sand coatings and their processes on the surface quality of castings.

[0006] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0007] The model for evaluating the influence of coated sand and its coating on the surface quality of castings comprises:

[0008] An upper base sand mold, the inside of which is provided with a sprue;

[0009] A middle base sand mold, the inside of which is provided with a plurality of vertically distributed ingates, the top of which is in communication with the end of the cross runner;

[0010] The lower base sand mold is internally provided with a plurality of mold cavities in which standard coated sand core samples are placed, the mold cavities are opposite to the bottom of the inner gate and are in communication with each other; the upper base sand mold, the middle base sand mold and the lower base sand mold are sequentially fastened from top to bottom.

[0011] The beneficial effects of the above technical scheme are that a plurality of sand core samples are tested simultaneously under completely consistent working conditions through one pouring experiment, rapid, scientific and parallel comparison of different coating processes is realized, and evaluation efficiency and accuracy are improved.

[0012] Preferably, the top of the upper base sand mold is provided with a sprue cup, and the bottom of the sprue cup is in communication with the straight gate.

[0013] Preferably, the bottom of the straight gate is provided with a straight gate nest, and a plurality of the cross gates are in communication with the straight gate nest. The straight gate nest plays a role of flow distribution, so that the metal liquid enters each cross gate smoothly, ensures uniform distribution of the metal liquid, and improves test consistency.

[0014] Preferably, a filter screen is arranged in the straight gate nest. The filter screen can filter out inclusions and slag in the metal liquid, purify the metal liquid, prevent impurities from interfering with the evaluation of the surface quality of the casting, and improve the accuracy of the test data.

[0015] Preferably, the diameter of the inner gate gradually decreases from top to bottom. The tapered inner gate design can accelerate the flow of the metal liquid, form stable and concentrated liquid flow, enhance the scouring effect on the surface of the sand core, and magnify the performance difference of different coating processes.

[0016] Preferably, a gap is left between the bottom of the inner gate and the top of the coated sand core sample. The gap forms a suspended impact, prolongs the thermal action and mechanical scouring time of the metal liquid on the surface of the sand core, makes the coating performance difference more obvious, and facilitates observation and evaluation.

[0017] The method for evaluating the influence of coated sand and its coating on the surface quality of a casting by using a model comprises the following steps:

[0018] S1, a plurality of standard cylindrical coated sand core samples with the same material, formula and core making process are prepared, the coated sand core samples are divided into a plurality of groups, the coating type, application method, surface drying temperature and surface drying time are changed respectively, and a group of coated sand cores to be tested are prepared;

[0019] S2, the prepared upper base sand mold, middle base sand mold and lower base sand mold are cleaned, a plurality of coated sand cores treated by different processes are selected and placed in a plurality of mold cavities, the upper base sand mold, middle base sand mold and lower base sand mold are clamped and fastened, and pouring is prepared;

[0020] S3, using the same bag chemical composition and pouring temperature uniform metal liquid pouring, metal liquid in turn through the pouring cup, sprue, runner, inner gate, eventually forming a vertical downward flow, with consistent flow rate and pressure, while impacting the surface of multiple test sand core;

[0021] S4, after cooling, shakeout, take out the bearing-shaped castings formed with sand core, directly observe and compare the inner surface quality of multiple castings.

[0022] Preferably, the upper base sand mold, the middle base sand mold and the lower base sand mold are manufactured by using a 3D printing process.

[0023] According to the technical solution, compared with the prior art, the model and method for evaluating the influence of coated sand and its coating on the surface quality of castings are provided, and the beneficial effects are as follows:

[0024] (1) A single pouring can compare multiple coating processes, significantly shorten the test period, and perform parallel tests under completely consistent thermodynamic conditions to ensure fair data;

[0025] (2) Effectively separate the variable "coating process" to independently evaluate its influence on the surface quality of castings;

[0026] (3) By using 3D printing sand molds, standardized sand cores and filter screens, the interference factors such as sand mold manufacturing, metal liquid purity and flow field fluctuations are maximally eliminated, the test variable is perfectly focused on the "coating process" itself, and the test repeatability and data reliability are ensured;

[0027] (4) The impact-formed castings do not form a closed loop, and the inner surface is not blocked, which facilitates subsequent detection and analysis such as visual observation, three-dimensional scanning and roughness measurement, the data acquisition is simple and intuitive, the coating performance is directly reflected by the inner surface quality of the castings, and qualitative and quantitative analysis is facilitated. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description. Obviously, the drawings in the following description are only embodiments of the present application, and those skilled in the art can obtain other drawings according to the provided drawings without creative labor.

[0029] Figure 1 The structural schematic diagram of the model provided by the present application;

[0030] Figure 2 The top view of the model provided by the present application;

[0031] Figure 3A sectional view at A-A in FIG. Figure 2 A sectional view at A-A in FIG.

[0032] Figure 4 A sectional view at A-A in FIG.

[0033] Figure 5 A sectional view at A-A in FIG. Figure 6 A sectional view at A-A in FIG. Figure 7 A sectional view at A-A in FIG. Figure 8 A sectional view at A-A in FIG.

[0034] In the figure,

[0035] 1 - upper base sand mold;

[0036] 11 - sprue; 12 - runner; 13 - sprue pocket;

[0037] 2 - middle base sand mold;

[0038] 21 - inner runner;

[0039] 3 - lower base sand mold;

[0040] 31 - cavity;

[0041] 4 - coated sand core sample; 5 - sprue cup; 6 - casting; 7 - surface to be tested. DETAILED DESCRIPTION

[0042] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0043] The embodiments of the present application disclose a model for evaluating the influence of coated sand and its coating on the surface quality of a casting, comprising:

[0044] The upper base sand mold 1 is internally provided with a sprue 11; the bottom of the sprue 11 is communicated with multiple runners 12;

[0045] The middle base sand mold 2 is internally provided with multiple vertically distributed inner runners 21, the top of the inner runner 21 is communicated with the end of the runner 12;

[0046] The lower base sand mold 3 is internally provided with a plurality of mold cavities 31, the mold cavities 31 are internally placed with standard coated sand core samples 4, the mold cavities 31 are opposite to the bottom of the inner gate 21 and are in communication with each other; the upper base sand mold 1, the middle base sand mold 2 and the lower base sand mold 3 are sequentially fastened from top to bottom. The present application is internally provided with a plurality of mold cavities 31, through one-time pouring experiment, parallel comparison data of a plurality of coating processes can be obtained under absolutely consistent working conditions, so that fast, scientific and quantitative evaluation is realized, and efficient and reliable decision basis is provided for coating selection and process optimization.

[0047] In one embodiment, the plurality of cross gates 12 are horizontally symmetrically distributed, and are in communication with the bottom of the straight gate 11 to ensure that the metal liquid is uniformly distributed into the plurality of cross gates 12.

[0048] In one embodiment, the top of the upper base sand mold 1 is provided with a sprue cup 5, and the bottom of the sprue cup 5 is in communication with the straight gate 44.

[0049] In one embodiment, the bottom of the straight gate 44 is provided with a straight gate nest 13, and the plurality of cross gates 12 are in communication with the straight gate nest 13.

[0050] In one embodiment, the straight gate nest 13 is internally provided with a filter screen. The filter screen 22 is a refractory filter screen, and the filter screen 22 is arranged at the bottom of the straight gate 11. On one hand, the filter screen 22 filters out slag and inclusions in the metal liquid, purifies the metal liquid, and prevents large impurities from affecting surface quality evaluation. On the other hand, the filter screen 22 plays a role in buffering and stabilizing flow state, so that the metal liquid enters the cross gate 12 smoothly.

[0051] In one embodiment, the diameter of the inner gate 21 gradually decreases from top to bottom. The inner gate 21 adopts a tapered design with a thick upper part and a thin lower part, which can effectively converge the metal liquid, increase the flow rate of the metal liquid, increase the scouring efficiency, provide sufficient pressure head, and ensure that the metal liquid is fully accelerated in the inner gate 21 and forms a directional flow beam.

[0052] In one embodiment, the standard coated sand core sample 4 is cylindrical, with a diameter of 50 mm and a height of 50 mm. The surface is coated with a specific type of coating, applied in a specific manner, and treated at a specific surface dry temperature and time according to the experimental design requirements.

[0053] In one embodiment, the bottom of the inner gate 21 and the top of the coated sand core sample 4 are spaced apart. The outlet of the inner gate 21 is kept a certain distance from the highest point of the upper surface of the coated sand core sample 4, forming a suspended impact. The semicircular cavity at the bottom of the middle base sand mold 2 provides sufficient space for the metal liquid to splash and flow after impacting the sand core, aiming to prolong the time of the high-temperature metal liquid and the coating sand core surface heat action and mechanical scouring action, so as to amplify the performance difference of different coating processes, so that the test results are more obvious and easy to observe.

[0054] The method for evaluating the impact of coated sand and its coatings on the surface quality of castings using a model is as follows:

[0055] S1. Prepare four standard cylindrical coated sand core samples 4 with identical materials, formulations and core-making processes. Divide the coated sand core samples 4 into several groups and change the coating type, application method, surface drying temperature and surface drying time to prepare a group of coated sand cores to be tested.

[0056] S2, clean the prepared upper matrix sand mold 1, middle matrix sand mold 2, and lower matrix sand mold 3, select four coated sand cores that have undergone different processes, and put them into the four cavities 31 respectively. Close and secure the upper matrix sand mold 1, middle matrix sand mold 2, and lower matrix sand mold 3, and prepare for pouring.

[0057] S3 uses molten metal with the same chemical composition and pouring temperature for pouring. The molten metal flows through the pouring cup 5, the straight sprue 11, the horizontal sprue 12, and the ingate 21 in sequence, eventually forming multiple vertical downward liquid streams that simultaneously impact the surfaces of the four test sand cores with consistent flow rate and pressure.

[0058] S4. After cooling, remove the sand and take out the casting sample with the sand core forming the bearing shape. Directly observe and compare the inner surface quality of the four castings 6.

[0059] In one embodiment, such as Figure 8 As shown, the contact surface between the semi-circular part of casting 6 and the coated sand core sample 4 is the surface to be tested of the casting. By observing and comparing the surface roughness of the four test surfaces 7 of casting 6, tools such as roughness testers, three-dimensional scanners, and stereomicroscopes can be used for quantitative measurement and analysis, thereby scientifically evaluating the advantages and disadvantages of different coating processes.

[0060] In one embodiment, the upper matrix sand mold 1, the middle matrix sand mold 2, and the lower matrix sand mold 3 are manufactured using 3D printing technology. 3D printing ensures high dimensional accuracy and inherent consistency of the model itself, fundamentally eliminating interference factors such as cavity size deviations and uneven compaction that may occur with traditional manual molding or mold making, thus providing a highly repeatable benchmark platform for experiments.

[0061] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0062] The foregoing description of the disclosed embodiments enables a person skilled in the art to make or use the application. Modifications of these embodiments will occur to persons of skill in the art, and that the appended claims are intended to cover all such modifications that do not depart from the true spirit and scope of the application. Therefore, the application is not limited to the embodiments shown but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A model for evaluating the effect of coated sand and its coating on the surface quality of a casting, characterized in that, The utility model relates to a sand mold for evaluating the surface quality of coated sand cores, comprising: an upper base sand mold having a sprue hole formed therein; a middle base sand mold having a plurality of vertically distributed inner gates formed therein, the inner gates being connected to the end of the cross gates; a lower base sand mold having a plurality of cavities formed therein, the cavities being placed with standard coated sand core samples, the cavities being opposite to the bottom of the inner gates and being in communication with each other; the upper base sand mold, the middle base sand mold and the lower base sand mold being fastened in order from top to bottom.

2. The model for evaluating the coated sand and the effect of the coating thereon on the surface quality of a casting according to claim 1, characterized in that, The upper base sand mold is provided with a sprue cup at the top, the bottom of the sprue cup being in communication with the sprue hole.

3. The model for evaluating the coated sand and the effect of the coating thereon on the surface quality of a casting according to claim 2, characterized in that, The bottom of the sprue hole is provided with a sprue hole nest, and the plurality of cross gates are in communication with the sprue hole nest.

4. The model for evaluating the coated sand and the effect of the coating thereon on the surface quality of a casting according to claim 3, characterized in that, A filter screen is arranged in the sprue hole nest.

5. The model for evaluating the coated sand and the effect of the coating thereon on the surface quality of a casting according to claim 1, characterized in that, The diameter of the inner gate gradually decreases from top to bottom.

6. The model for evaluating the coated sand and the effect of the coating thereon on the surface quality of a casting according to claim 5, characterized in that, There is a gap between the bottom of the inner gate and the top of the coated sand core sample.

7. A method for evaluating the influence of coated sand and its coating on the surface quality of a casting using a model according to any one of claims 1 to 6, characterized in that, The evaluation steps are as follows: S1, a plurality of standard cylindrical coated sand core samples with the same material, formula and core-making process are prepared, the coated sand core samples are divided into groups, the coating type, application method, surface drying temperature and surface drying time are changed respectively, and a group of coated sand cores to be tested are prepared; S2, the prepared upper base sand mold, middle base sand mold and lower base sand mold are cleaned, a plurality of coated sand cores treated by different processes are selected and placed in the cavities, the upper base sand mold, middle base sand mold and lower base sand mold are fastened, and preparation for pouring is made; S3, the same chemical composition and pouring temperature of the metal liquid are used for pouring, the metal liquid flows through the sprue cup, the sprue hole, the cross gate and the inner gate in turn, and finally forms a plurality of vertically downward liquid streams, which impact the surfaces of the plurality of coated sand cores to be tested at the same flow rate and pressure; S4, after cooling, the sand casting is taken out, and the bearing-shaped castings with sand cores are directly observed and compared for the inner surface quality of the plurality of castings.

8. The method for evaluating coated sand and its coating effect on the surface quality of a casting using a model according to claim 7, characterized in that, The upper base sand mold, the middle base sand mold and the lower base sand mold are manufactured by 3D printing process.

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