Study on the Permeability Test of Fabric

Silica sol is a high quality binder commonly used in precision casting industry. The silica sol shell has high temperature strength and good surface quality. However, the silica sol shell has a low residual strength, which is less difficult to clean, and the shell is long. However, the strength and permeability of the cast silica sol are related to each other. The use of an increased shell thickness is often used to ensure the strength of the shell, resulting in difficulty in heat dissipation, large grain size, and poor air permeability through the permeability tester. , Must improve the pouring temperature of molten metal, making the shell and metal reaction to the extent of increased, greatly affecting the product surface quality, while the high temperature of the metal solution makes shell deformation serious, thus affecting the quality of casting.

So far, domestic and foreign scholars to study the use of fiber as a reinforcement to join the metal matrix composite material, can effectively improve the mechanical properties of composite matrix and organizational properties. According to the idea of ​​fiber-reinforced composites, the addition of ceramic organic fibers in the shells can hinder the expansion of the shells. When the cracks cross the fibers, it is necessary to remove the fibers from the shell base and to increase the energy The shell at room temperature strength, followed by making the shell at high temperatures is not easy to burst, thereby enhancing the shell of high temperature strength. The addition of polymer binder and nylon organic fiber to the slurry enhances the shell and found little effect on the strength, but it can increase the thickness of the shell and the anti-cracking at the corners. At the same time, After the roasting, the nylon fibers are completely burned, leaving many microvoids in the shell, enhancing the permeability of the shell.
The addition of rice bran to the ceramic shell has improved the performance of the shell before and after calcination, especially when the rice bran is burned in the shell, which increases the porosity of the ceramic shell and reduces the shell crack. the quality of. Based on this, in order to ensure that the shell has high room temperature strength, sufficient high temperature strength and better permeability, the authors use ceramic and nylon composite fiber reinforced cast silicon sol shell, through the fabric permeability tester test compound fiber The influence of the content on the shell temperature and the permeability and permeability of the silica sol shell was discussed, and the strengthening mechanism was discussed, which provided scientific basis and theoretical support for the production of the whole castings with high melting point complex structure.
Experimental MaterialsThe binder is alkaline silica sol, SiO2 content is 29% ~ 31%, colloidal particle size is 9 ~ 20 nm; nylon fiber, diameter d 9 ~ 13 μm, length For 2 ~ 4 mm ,; ceramic fiber (aluminum silicate fiber), diameter d 3 ~ 4.5 μm, length 4 ~ 6 mm. The main performance indicators of fiber are listed in Table 1.
experimental methodAccording to the current process of preparation of the shell layer and excessive layer of slurry, the fiber is only added to the back layer and the sealant slurry. The content of the composite fiber is increased from 0 to 0.75% of the mass of the silica sol in the slurry, and the intercalation amount is 0.15%, and the composite fiber is composed of 1: 1 interwoven with ceramic fiber and nylon fiber. The process parameters of the shell sample preparation are listed in Table 2. The roasting process of the shell sample is shown in Fig.Test test shell strength: with a size of 70 mm × 22.36 mm × 6 mm rectangular sample, using XQY? Ⅱ type intelligent sand strength tester, three-point bending test test bending strength method, the determination of shell samples The strength of the shell and the strength of the briquette were observed under the Quanta200 SEM. Test type shell permeability: with a size of d50 mm × 6 mm disc samples, using ZTY intelligent sand permeability tester, at room temperature to test the permeability of the wafer sample.
in conclusion1) ceramic and nylon composite fiber reinforced cast silica sol shell, when the composite fiber content of 0 ~ 0.75%, with the fiber content increases, shell strength increases first and then reduce; when the composite fiber content of 0.6 %, The shell temperature at room temperature reached a maximum of 3.638 MPa, compared with the traditional shell increased by 39%.2) The composite fiber content w was established, and the relationship between the calcination temperature t and the strength p after calcination was as follows: + + × pt t3 3.0758 2.9705 1.3 102 7 2 2.4518w 8.6667 10 t + The calcination temperature increases, and the strength of the shell increases first and then decreases. When the composite fiber content is 0.60% and the calcination temperature is 1050 ℃, the strength of the shell sample is 5.145 MPa after calcination.3) The nylon fiber is completely burned during the roasting process of the composite fiber reinforced shell, and many microvoids are left in the shell, which can effectively improve the permeability of the shell. With the increase of the composite fiber content, the permeability of the shell gradually increases.