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The ammonia content of molten iron after inoculation is reduced from 0.0165% at discharge to 0.0076%(cheap aluminium oxide sandblasting suppliers brazil). The ammonia content increases after spray desulfurization treatment. In general, the ammonia content of nodular iron castings in each plant is lower than that when molten iron is discharged, and can be maintained below 0.008%(aluminum oxide for sale). The solubility of nitrogen in pure molten iron at 1600 ℃ is 0.045%. 

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If iron contains carbon and silicon, the solubility decreases(cheap aluminium oxide sandblasting suppliers brazil). This formula shows that the limit solubility [n%] of nitrogen is directly proportional to the square root of nitrogen partial pressure. Adjusting nitrogen partial pressure can change the amount of nitrogen dissolved in molten iron during melting(180 grit aluminum oxide). The dissolution of nitrogen in molten iron is a process in which gaseous nitrogen molecules decompose into single atoms and dissolve into molten iron. 

For example, high carbon low silicon hot metal is desulfurized by this method, and w (n) increases from 0.0070% - 0.00995% to 0.0188% - 0.0164%(cheap aluminium oxide sandblasting suppliers brazil). The American Foundry Association (AFS) has investigated the nitrogen content of castings in five nodular iron plants. The results show that the nitrogen content of molten iron in electric arc furnace is higher than that in cupola(aluminum oxide sand). This structure usually occurs in cast iron with low carbon equivalent. 

Oxygen enriched air supply of cupola and injection of natural gas (increasing CO concentration) can reduce the nitrogen partial pressure and reduce the dissolution of nitrogen in molten iron(garnet sand). Results if the carbon content is unsaturated and the solubility remains unchanged, the effect of silicon is much greater than this(cheap aluminium oxide sandblasting suppliers brazil). While eliminating the white mouth, it does not significantly change the number and size of graphite of thick section. 

Opravil et al. Measured the saturated carbon content of molten iron and the solubility of nitrogen in molten iron at different temperatures at a pressure of 0.1MPa(70 grit aluminum oxide). The experimental results show that increasing the temperature of molten iron increases the solubility of carbon and the content of ammonia(aluminium oxide sandblasting grit). Too low or too high oxygen will lead to the formation of white mouth tissue and anti white mouth tissue(cheap aluminium oxide sandblasting suppliers brazil).

Therefore, the figure shows that the change of silicon content in carbon saturated Fe-C-Si solution at 1300-1700 ℃ causes the change of nitrogen solubility(black corundum). It can be seen that the increase of silicon content significantly reduces the solubility of nitrogen. This reduction has included the factor of increasing carbon solubility(cheap aluminium oxide sandblasting suppliers brazil). Surface active elements, especially oxygen and sulfur, reduce the dissolution rate of nitrogen.

When the content of oxygen and sulfur is low, the dissolution rate of nitrogen in molten iron is controlled by the diffusion rate of chlorine atoms(alumina adsorbent). The effect of sulfur is very significant, increasing sulfur by 0.05% and reducing the dissolution rate coefficient of nitrogen by about 50%(cheap aluminium oxide sandblasting suppliers brazil). Because carbon and silicon significantly reduce the solubility of nitrogen in molten iron, the nitrogen content of cast iron is lower than that of steel. 

High activity carbon atoms get rid of the tendency to form compounds with iron atoms and transfer to the surface of nucleation matrix, which can increase the number of effective graphite nuclei and promote the smooth growth of graphite(steel grid). The technical means of using specific foreign substances to promote the graphitization of cast iron is called cast iron inoculation treatment(cheap aluminium oxide sandblasting suppliers brazil). Nitrogen has a significant effect on the microstructure of cast iron.

Before the solidification of molten iron, a small amount of alloy additives (inoculants) are added to form carbon atom activation micro areas around the existing or newly added nucleation matrix in molten iron(pink aluminum oxide). Some inoculants are properly added with pearlite stabilizing elements, so that the inoculants expand from simply promoting graphitization to the composite function of graphitization and stabilizing pearlite(cheap aluminium oxide sandblasting suppliers brazil). 

However, the eutectic of molten iron with this composition has high undercooling and is prone to white mouth(aluminium oxide sand). In this case, good results can be obtained by inoculation treatment, which can not only avoid white cast iron, but also obtain fine A-type graphite, and the mechanical properties of cast iron are significantly improved(cheap aluminium oxide sandblasting suppliers brazil). Some iron castings need ammonia to improve the microstructure and mechanical properties of cast iron. 

The microstructure and strength of cast iron castings poured with molten iron in the same furnace will be significantly different in different parts of section thickness(glass bead blasting media suppliers), that is, the microstructure and properties of cast iron castings are sensitive to section size(cheap aluminium oxide sandblasting suppliers brazil). High quality and high strength gray cast iron should have fine and evenly distributed A-type graphite and fine pearlite matrix structure. 

Inoculant can improve the nucleation probability of graphite, promote graphitization, and help to eliminate the white mouth of thin section(green silicon carbide). Thin gray edges and internal white spots containing cellular gray spots often appear in the reverse white section of malleable cast iron(cheap aluminium oxide sandblasting suppliers brazil). Hot metal insulation is carried out before desulfurization in each plant, and the nitrogen content is reduced during the insulation process.

Because the main function of inoculant is to promote graphite nucleation, and when the carbon equivalent and silicon carbon ratio change little, the number of nucleation per unit molten iron volume is also limited(cheap aluminium oxide sandblasting suppliers brazil). Therefore, inoculant can effectively reduce the sensitivity of casting structure to section size and make the section structure with different thickness tend to be uniform(aluminum oxide abrasive powder). The same is true of flake graphite.

The composite inoculant can play a role in the eutectic transformation stage and in the solid phase transformation process, reduce ferrite in the matrix, stabilize and refine pearlite structure, eliminate secondary carbides, and make the mechanical properties of cast iron reach a higher level(cheap aluminium oxide sandblasting suppliers brazil). To discuss the nucleation conditions of graphite in molten iron, the problem of graphite nucleation is always involved(aluminum oxide grit blasting). 

To explore the inoculation theory, we should pay attention to the following problems(cheap aluminium oxide sandblasting suppliers brazil): how the inoculant changes the carbon activity in molten iron and thus promotes graphitization, and how the inoculation treatment creates the nucleation conditions of graphite in molten iron(black silicon carbide). When discussing whether there is a specific crystal core in spherical graphite, it has been explained that such crystal core has not been found at present. 

After adding ferrosilicon particles, many high silicon micro regions are produced near the graphite core(aluminium oxide blast media). The solution samples were scanned and diffracted by electron microprobe(cheap aluminium oxide sandblasting suppliers brazil). It was found that there were pure silicon and electron compound 2 phase with hexagonal lattice composed of silicon and iron near the peak of silicon concentration(corundum sand). With the diffusion of carbon and silicon atoms, e phase is transformed into SiC crystal.