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Alumina Adsorbent

The oxygen content of gray cast iron melted in power frequency furnace is (10-22) × 10 *%, oxygen content of cupola gray cast iron water is (30-60) X10 *%(alumina adsorbent). When the molten iron is then undercooled to slightly lower than the metastable eutectic temperature, the cementite nucleus will grow rapidly relying on austenite to produce cementite co products and form the structure of gray outside and white inside. 

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Therefore, most of the cementite eutectic is in the form of coating(black silicon carbide). In this case, eutectic austenite is embedded in cementite in a cylindrical shape. For a long time, some people have been studying the behavior and change law of oxygen in iron phosphorus alloy liquid(aluminum oxide sandblasting media). Until the solid electro oxygen concentration battery is developed, this problem has not been clearly solved(alumina adsorbent). 

Because the content of carbon and silicon in cast iron melt is much higher than that in molten steel, it can react with oxygen, so there is no need to carry out specific deoxidation process like steelmaking(aluminum oxide blasting grit). Although the oxygen content is small, it plays an important role in the formation of cast iron structure(alumina adsorbent). The effect of hot metal superheat temperature on its oxygen content and decarburization is shown in the figure.

According to the functional relationship between the potential difference between the two electrodes buried in molten iron and the molten iron temperature and oxygen partial pressure, the electric oxygen concentration battery measures the dissolved oxygen concentration in molten iron at the moment, which provides accurate data for understanding the behavior of oxygen in molten iron(alumina adsorbent). 

Considering the reaction of silicon and carbon to oxygen only, the relationship between dissolved oxygen concentration and temperature is shown in the figure, and the intersection temperature of the two curves is 1384 ℃(green silicon carbide). Only increasing the temperature can increase the reaction rate and reach equilibrium(alumina adsorbent). Graphite nucleation occurs when w (c) = 2.53% and w (SI) = 1.44% of molten iron is undercooled to 1104 ℃.

First, molten iron exists in a dissolved state and becomes dissolved oxygen(aluminum oxide blasting abrasive); The second is the formation of oxides, which exist in a combined state. Below this temperature, the formation of new oxides is difficult to occur spontaneously, and the reaction proceeds slowly to equilibrium(garnet sand). The reason for the formation of gray spots is not very clear(alumina adsorbent). The thickness of the growing layer is about several to tens of atomic spacing.

Dissolved oxygen has metallurgical activity, dominates the behavior of oxygen in molten iron, and affects the metallurgical reaction in the smelting process of cast iron(alumina grit). Dissolved oxygen also varies with temperature and the progress of metallurgical reaction. Oxygen exists in molten iron in two states(alumina adsorbent). In the melting process of cast iron, SiO2 particles from charge and lining exist simultaneously with silica reactants in molten iron. 

FeO in the charge belt and FeO formed by the reaction of supersaturated oxygen with iron also play a role in the process of sio2-co equilibrium conversion (Si-C equilibrium reaction). Below this temperature, SiO2 formation reaction takes priority; Above this temperature, the CO formation reaction takes priority(aluminium oxide shot blasting grit). 1384 ℃ is the theoretical equilibrium temperature for the conversion of the two reactions(alumina adsorbent). 

The following four reaction formulas involve the metallurgical reaction of oxygen at the same time(alumina abrasive powder): if the content of carbon and silicon and the relevant interaction coefficient are known, the equilibrium temperature of Si-C reaction can be calculated, or the content of carbon and silicon when the reaction reaches equilibrium at a certain temperature(alumina adsorbent). According to the above calculation, a nomogram can be drawn, which is very convenient to use.

After further rapid cooling, the second eutectic stop point appears in the cooling curve(220 grit aluminum oxide blast media). After solidification, the upper surface of the sample section is gray belt and the interior is pitting structure. During Eutectic Transformation, a considerable amount of pre eutectic austenite exists in molten iron(alumina adsorbent). Eutectic austenite must preferentially grow on the original austenite dendrite, resulting in this form of eutectic growth.

When the undercooling is higher, a D-type graphite eutectic thin layer appears on the surface of the sample(fine grit aluminum oxide). Due to the small amount of CO products, there is almost no eutectic stop point on the cooling curve(alumina adsorbent). Cementite eutectic precipitates below the metastable eutectic temperature, and the latent heat of crystallization heats up the sample, resulting in the lamellar cementite(steel grid). There are gray cellular spots in the white mouth area. 

One possible reason is that the nucleation matrix in the liquid phase forms a few effective graphite crystalline cores under high undercooling(1200 grit aluminum oxide). The anti white mouth of the former is generally composed of the gray belt on the surface and the hemp mouth structure inside. Sometimes there is compact graphite in the transition zone between the gray mouth and the white mouth(alumina adsorbent).

Another possibility is that the microcrystals formed near the mold wall at the beginning of solidification float inside the casting and become the core material inducing graphite eutectic reaction, resulting in the formation of gray spots(aluminium oxide blasting grit). The molten iron with low carbon equivalent, especially low silicon content, is prone to anti white structure during solidification under high undercooling conditions(alumina adsorbent).

Malleable cast iron and high strength gray cast iron have low carbon equivalent and are very sensitive to anti white cast iron(glass bead blasting media suppliers). Especially when there are alloying elements or impurity elements that promote the undercooling of molten iron, it is most likely to produce anti white mouth defects(alumina adsorbent). The anti white structure of low carbon equivalent gray cast iron and malleable cast iron is not exactly the same. 

Based on the experience of controlling anti white mouth defects, the main gold treatment factors of anti white mouth phenomenon are: improper control of batching or melting process, low alkali equivalent of molten iron(alumina adsorbent). Malleable cast iron contains excessive Qi or bismuth(150 grit aluminum oxide). These oxygen make the dissolved oxygen content of molten iron usually exceed the equilibrium content and in a supersaturated state.

Hot metal has high superheat temperature (more than 1500 ℃) and is kept in the furnace for a long time(alumina blasting); High content of oxygen, ammonia and hydrogen; The sulfur absorption of molten iron is large, the manganese sulfur ratio is inappropriate, and the sulfur content of molten iron is high(aluminium oxide blast media). Oxygen in cast iron comes from several aspects: absorption from the atmosphere; Dissolved oxygen in charge belt(alumina adsorbent); The rust carries human chemical oxygen. 

 For heavy castings with high chromium content, such as hot metal pouring at low temperature, the residual magnesium content or residual rare earth content of nodular cast iron is too high(240 grit aluminum oxide); The inoculation of low carbon equivalent gray cast iron or nodular cast iron is insufficient or the inoculation recession occurs(alumina adsorbent); Low temperature molten iron casts molds with high thermal conductivity.

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