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High Quality Aluminum Oxide Suppliers Tunisia

What needs to be further discussed is the thermodynamic conditions for the nucleation of graphite on homogeneous substances in order to confirm the universality of this view(high quality aluminum oxide suppliers tunisia). The effect of hot metal residence time on the number of common clusters after inoculation at different superheat temperatures is shown in Fig. The reduction of eutectic clusters varies with different inoculants. 


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In the inoculation practice of cast iron, it is found that the inoculation effect increases sharply in a short time after the inoculant is added to molten iron(aluminum oxide blasting abrasive). However, after a period of time, the inoculation reached a peak, then began to weaken, and finally disappeared completely. The phenomenon that the incubation effect decreases with time is called incubation recession(high quality aluminum oxide suppliers tunisia). Breeding recession is manifested in the following phenomena. 


These phenomena are compared with the intact inoculation results(silicon carbide powder). Each inoculant has the approximate number of eutectic clusters that can be produced when it gives full play to the inoculation effect. White mouth appeared in some thin sections earlier. The mechanical properties of the material decreased(high quality aluminum oxide suppliers tunisia). This situation generally occurs when the content of carbon and silicon in the raw molten iron is high and the sample cools quickly. 


With the increase of eutectic undercooling, the tendency of white cast iron increases(high quality aluminum oxide suppliers tunisia). The white mouth depth shown by the triangular test piece poured on the production site increases. From the section of the test piece, there is a pockmarked area where graphite and cementite coexist between the gray mouth area and the white mouth area or within the gray mouth area(aluminium oxide blasting media): the number of eutectic clusters decreases significantly.


A typical example is that silica is contaminated by FeO and forms a complex surface layer of iron, manganese, oxide and silica on the substrate(high quality aluminum oxide suppliers tunisia). When the molten iron reaches the solidification temperature, the graphite particles and the carbon atom groups that have been biased become the graphite nucleation matrix, so that the carbon atoms can be conveniently deposited on it to form graphite nuclei(aluminium oxide shot blasting grit). 


Among the above phenomena, as long as one or two are very obvious, it shows that the batch of castings has been inoculated and declined(silicon carbide grit). The graphite nucleation effect produced by inoculant is corresponding to the viscosity of molten iron (Fig. 52). Curve a in Figure 52 represents the molten iron without inoculation treatment, and curve B is the variation curve of molten iron viscosity with time after adding ferrosilicon inoculant(high quality aluminum oxide suppliers tunisia).


It can be seen that the effect of inoculation temperature on the change of eutectic number is small when the residence time is short(aluminium oxide blasting grit); When the residence time is fixed, the higher the inoculation temperature is, the fewer the number of eutectic clusters is, indicating that the inoculation decay phenomenon is more significant(high quality aluminum oxide suppliers tunisia). This concentration difference drives the silicon atoms in the silicon rich micro region to diffuse to the periphery.


The occurrence of inoculation decay involves a series of factors, such as the behavior of inoculant in molten iron, the diffusion process of carbon and silicon atoms in molten iron under the change of molten iron temperature, the formation and dissolution process of graphite crystal nucleus and so on(fine grit aluminum oxide). Generally, the formation and decline of these inoculation processes are dynamic processes(high quality aluminum oxide suppliers tunisia). The sensitivity of casting structure to section is strengthened.


The effective time of inoculation mainly depends on the melting rate of inoculant in molten iron and the diffusion rate of carbon and silicon atoms leading to the homogenization of molten iron composition(garnet blasting media). Generally speaking, the main causes of inoculation recession of cast iron are as follows: the disappearance of silicon rich micro region(high quality aluminum oxide suppliers tunisia). Only this surface can make carbon grow epitaxially on it to form a surface graphite layer.


Someone once made the concentration tend to balance, the silicon rich micro area gradually disappeared, and the inoculation also declined or even disappeared(high quality aluminum oxide suppliers tunisia). As mentioned earlier, breeding recession will not appear immediately, but will go through a time process(150 grit aluminum oxide). The white depth and cast iron strength of samples poured at different times were measured, and the results were in good agreement with the law of viscosity change. 


However, at the normal inoculation temperature (1380 ~ 1420 ℃), the melting rate of granular = (SI) = 75% ferrosilicon or composite inoculant in molten iron is very high(steel shot abrasive). The melting time of particles below 5mm shall not exceed lmin(high quality aluminum oxide suppliers tunisia). In the inoculation process, the silicon concentration in the silicon rich micro region formed by adding inoculant with high silicon content is much higher than that in the surrounding molten iron. 


When the particle size is large, the holding time of inoculant in molten iron is longer(glass bead abrasive). The diffusion rate of alkali is low The time of re dissolving molten iron is longer than the diffusion time of silicon, and can be maintained on the surface of nucleation matrix for 3-5min. The length of this process is affected by some factors(alumina blasting). Properly reducing the melting rate of inoculant can make the disappearance time of silicon rich micro region go back(high quality aluminum oxide suppliers tunisia). 


In actual production, the effective action time of silicon inoculant with appropriate particle size in molten iron is 10-20min, which is longer than the retention time of silicon and carbon atoms in the above-mentioned preparation area(high quality aluminum oxide suppliers tunisia). With the same amount of inoculant, when the particle size increases, the number of particles decreases, the nucleation position of graphite will also decrease, and the carbon atoms in the micro region will also diffuse(40 grit aluminum oxide).


Although the carbon atoms on the surface of this activated nucleus will gradually dissolve in molten iron, their diffusion rate and dissolution rate are much lower than those in the silicon rich micro region, so that the effective action time of the inoculant can be prolonged(high quality aluminum oxide suppliers tunisia). If the inoculant contains anti decay elements such as calcium, strontium and fear, the oxides formed by these elements in molten iron can effectively inhibit the diffusion of carbon and silicon atoms.


In the short time before the diffusion of carbon and silicon atoms, some carbon atoms have covered the nucleation matrix and become activated nuclei(240 grit aluminum oxide). The graphite nucleation matrix is polluted, so that its crystalline surface is covered by pollutants and loses its activity, the nucleation disappears, and finally leads to incubation decline(high quality aluminum oxide suppliers tunisia). The graphite type changes. Most of the A-type graphite is changed to D-type graphite.


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