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40 Grit Aluminum Oxide

The outermost electron layer (L layer) of carbon atom has four electrons with a configuration of 23p °(40 grit aluminum oxide). Many years of scientific research and practice have proved that the key to the inoculation theory is to study the role of nucleation matrix in the inoculation process of molten iron(aluminum oxide abrasive media). Inoculant changes the carbon cleanliness in molten iron and promotes graphitization. 

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The figure shows the silicon concentration distribution in molten iron micro zone without inoculated ferrosilicon and after inoculated ferrosilicon(aluminium oxide blasting grit). It can be seen that silicon is basically evenly distributed before ferrosilicon is added. The carbon atoms occupying the corner of the hexagonal lattice base form a covalent chain connection by the hybrid orbital formed by the overlap of orbital and No. p orbital(40 grit aluminum oxide). 

The fourth electron (called electron) outside the hybrid orbital binds to other atoms by opening bonds with weak binding force(aluminium oxide blasting media). The binding force of R bond in atomic nucleus is small, and snow electrons are easy to break away from the binding force and participate in chemical reactions(40 grit aluminum oxide). The outermost layer (n layer) of iron atom has only s sublayer, which contains paired electrons, i.e. 4(aluminum oxide blasting abrasive).

It can be seen that after inoculant is added into molten iron, how to affect the thermodynamic properties of potential graphite nucleation micro region and effectively lead to graphite formation should be the main part of inoculation theory(40 grit aluminum oxide). The study of graphite nucleation conditions basically focuses on the nucleation carrier(220 grit aluminum oxide blast media), that is, the nucleation matrix that can accept carbon atoms deposited on it. 

The electron configuration of the sub outer layer (m layer) is 30pd, the electrons in D orbit are not full, and the electrons in D and orbit are easy to exchange(40 grit aluminum oxide). The sublayer orbital enters the d orbital not filled with electrons in the m layer of iron atoms through s → D exchange, and the iron carbon compound is formed according to the following formula(150 grit aluminum oxide). Therefore, the electrons in some carbon atoms in molten iron are easy to transfer to the electrons in iron atoms.

In the silicon rich micro region of molten iron, this reaction changes, and the iron carbon compound is replaced by graphite crystal(glass bead abrasive). Because the extra nuclear electron configuration of silicon atom is 12p3s3p. Inoculation treatment is indispensable for low carbon equivalent gray cast iron, nodular cast iron with high undercooling and some alloy cast iron(40 grit aluminum oxide). The affinity between these elements and oxygen is higher than that of silicon, and the oxidation reaction is exothermic. 

At the same time, the p orbital of the M electron layer of silicon atom also transports electrons to the electron region of carbon, strengthening the binding energy between C-C(40 grit aluminum oxide). SiC crystal is unstable and can only exist in molten iron for a short time, and decomposes according to the following formula(alumina grit): the decomposed carbon atoms have high activity in the silicon rich micro region, and can form graphite crystal nucleus by attaching to a suitable nucleation matrix.

The above mechanism shows that the inoculation effect of these ferrosilicon (or composite ferrosilicon) in cast iron is not to directly provide nucleation basic materials to molten iron, but to promote the formation of graphite crystalline core by improving the activity of carbon in molten iron(40 grit aluminum oxide). Therefore, the reason why ferrosilicon inoculation promotes graphitization is put forward from the aspect of atomic structure(240 grit aluminum oxide).

For example, some related statements are discussed below(40 grit aluminum oxide). The alloy additives added for the purpose of promoting graphitization are usually ferrosilicon and composite ferrosilicon containing some alkaline earth metals and rare earth elements, which are usually called silicon inoculants(green silicon carbide). The formation heat, melting point and lattice type of oxides and sulfides of aluminum, barium, calcium, cerium, tension, silicon, saw and drill are listed in the table. 

Although the formation of graphite does not rule out the possibility of homogeneous nucleation, the fact that there are heterogeneous cores in most graphite shows that the graphite crystalline core is mainly formed by the "germ" action of nucleation matrix (heterogeneous nucleation). Therefore, a lot of research work has been devoted to exploring the structure and properties of these nuclear basic materials(40 grit aluminum oxide). 

After inoculant is added to molten iron, some oxides, sulfides and compound salts are produced in molten iron(steel shot abrasive). These suspended solid particles have their own crystal structure(40 grit aluminum oxide). The p orbital in the outermost layer (m layer) can transport valence electrons to the d orbital of iron atom, and reach the d orbital of iron atom through the electron exchange of SD orbital to form FeSi (€ phase), which significantly reduces the binding energy between iron atom and carbon atom.

Some of the particles are close to a certain lattice constant of graphite crystal (low mismatch), which is conducive to the combination with carbon atoms(black silicon carbide); If the physical and chemical properties of these solid particles can meet some thermodynamic conditions, its surface may accept carbon atoms and become the basic material (nucleation matrix) of graphite nucleus(40 grit aluminum oxide). The role of silicon in promoting the graphitization of cast iron can also be discussed from the atomic structure.

In addition, insoluble graphite particles in molten iron are also considered to be effective nucleation matrix(aluminum oxide blasting grit). Ferrosilicon contains IIA group elements calcium, strontium, barium, aluminum, zirconium and other elements. The essence is that the activity of carbon in silicon rich micro region in molten iron is improved, the tendency of carbon atoms to combine with iron atoms to form compounds is reduced, and the tendency to form graphite is enhanced(40 grit aluminum oxide).

When the above aluminum and zirconium elements generate oxides in molten iron, the temperature of graphite nucleation micro region can be further increased(aluminium oxide shot blasting grit), so that carbon atoms have sufficient thermodynamic driving force and enough time to migrate to the surface of nucleation matrix, so as to promote the formation of graphite nucleus(40 grit aluminum oxide). Some sulfides, carbides, oxides and silicates of these elements have been detected in the heart of graphite. 

Sulfide is found in the graphite core of many gray cast iron and nodular cast iron(garnet blasting media). It is also found that the presence of a small amount of sulfur in gray cast iron has an obvious effect on the type of graphite, the number of eutectic clusters, the depth of white cast iron and the cooling curve(40 grit aluminum oxide). Silicon oxides play an important role in the nucleation process(fine grit aluminum oxide). SiO2 heat of formation is often used as the comparison standard of oxide heat of formation.

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