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Understanding petroleum carburizing agents

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Understanding petroleum carburizing agents

Date:2017-08-24 Author: Click:

Petroleum carburizer is a kind of pure carbon-containing graphitized material, which can reduce excessive impurities in pig iron. Proper selection of carburizer can reduce the cost of casting production. The carburizer produced by our company is made of high quality graphite which is strictly screened and refined, crushed and baked at high temperature by continuous high temperature furnace process.

Dry and sieving processes, with high purity, high quality particle morphology and graphitized crystal structure, not only play a role in carburizing, but also promote the inoculation and nucleation of cast iron, improve graphite refinement, increase the number of graphite nodules, improve the mechanical properties and processing properties of materials. Carburizer used in casting can greatly increase the amount of scrap steel, reduce the amount of pig iron or no pig iron, is very suitable for electric furnace smelting, there are also a small number of absorption rate of special fast carburizer used in cupola. In order to avoid excessive oxidation and low carbon content of castings, carburizer should be added to molten iron with scrap and other burden in electric furnace. The amount of carburizing agent is determined according to the ratio of other raw materials and carbon content. Different types of cast iron, according to need, choose different types of carburizing agent 1. carbon carburizing particle size influence.

The carburizing process using carburizing agent includes dissolution and diffusion process and oxidation loss process. The size of the carburizing agent is different, and the rate of dissolution and diffusion and the rate of oxidation loss are different. The absorption rate of the carburizer depends on the comprehensive effect of the dissolution and diffusion rate of the carburizer and the oxidation loss rate: in general, the carburizer particles are small, the dissolution rate is fast, and the loss rate is large; the carburizer particles are large, the dissolution rate is slow, and the loss rate is small. The size of the carburizing agent is related to the diameter and capacity of the furnace. In general, the diameter and capacity of the furnace is large, the particle size of the carburizer is larger; conversely, the particle size of the carburizer is smaller. The granularity of crystalline graphite is required to be 0.5-2.5 mm for electric furnace melting below 1 t, 2.5-5 mm for crystalline graphite for 1t-3 t, 5.0-20 mm for crystalline graphite for 3t-10 T and 0.5-1 mm for crystalline graphite for coating in ladle.

2. the influence of adding amount of carburizing agent.

Under certain conditions of temperature and chemical composition, the saturation concentration of carbon in molten iron is certain. The dissolution limit of carbon in cast iron is ([C%]=1.3+0.0257T-0.31 [Si%]-0.33 [P%]-0.45 [S%]+0.028 [Mn%] (T is molten iron temperature). At a certain saturation, the more the carburizer is added, the longer the dissolution and diffusion time is required, the greater the corresponding loss, and the lower the absorption rate.

3. effect of temperature on absorbance of carburant

From the point of view of kinetics and thermodynamics, the oxidation of molten iron is related to the equilibrium temperature of C-Si-O system, that is, O in molten iron reacts with C and Si. However, the equilibrium temperature varies with the target C and Si content. When the molten iron is above the equilibrium temperature, carbon oxidation takes precedence. C and O form CO and C O2. In this way, the oxidation loss of carbon in molten iron increases. Therefore, above the equilibrium temperature, the absorbency of carburizing agent decreases; below the equilibrium temperature, the saturated solubility of carbon decreases, and the dissolution and diffusion rate of carbon decreases, resulting in a lower yield; at the equilibrium temperature, the absorbency of carburizing agent is the highest.

Petroleum carburizing agent

4. the influence of iron stirring on the absorbance of carburant

Mixing is conducive to the dissolution and diffusion of carbon, so that the carburizing agent will be burned on the surface of molten iron. The stirring time is long and the absorption rate is high before the carburizing agent is completely dissolved. Stirring can also reduce the carburizing and holding time, shorten the production cycle and avoid the burning loss of alloy elements in molten iron. However, too long stirring time not only has a great impact on the service life of the furnace, but also increases the carbon loss in molten iron after the carburizer dissolves. Therefore, suitable iron stirring time should be guaranteed to completely dissolve the carburizing agent.

5. the influence of chemical composition of iron liquid on the absorbance of carburant

When the initial carbon content in molten iron is high, the absorption rate of carburizer is slow, the absorption amount is small, the burning loss is relatively large, and the absorption rate of carburizer is low under a certain dissolution limit. When the initial carbon content of molten iron is low, the opposite is true. In addition, silicon and sulfur in molten iron hinder the absorption of carbon and reduce the absorption rate of carburant, while manganese contributes to the absorption of carbon and increases the absorption rate of carburant. As far as the extent of impact is concerned, silicon is the largest, followed by manganese, and carbon and sulfur are less affected. Therefore, the actual production process should increase manganese first, then increase carbon and then increase silicon. Carburizer is an indispensable auxiliary material in steelmaking enterprises. At present, there are three kinds of carburizer used in domestic steel plants.

1. coal carburizing agent: the composition is generally C:90-93%, S0.3-0.5%. The absorption rate is more than 60-75%, which is mainly used in steelmaking enterprises.

Advantages: low price

Disadvantages: low carbon content, slow melting, waste of electricity, large amount of residue and large usage. Coal carburizing agent

2. Calcined petroleum coke carburizer: the composition is generally C:96-98.5%, S<0.5% is more, the absorption rate is more than 90%.

Advantages: Petroleum coke carburizer is made by calcining and purifying petroleum coke at 2000 degrees Celsius. It has less impurities, reasonable price and high absorption rate. It is a kind of carburizer with good effect and cost in steel plant.

Carbon additive for petroleum coke

3. Graphite carburizer: the composition is generally C:98-99.5%, S 0.03-0.05% is more, the absorption rate is more than 90-95%.

Advantages: The graphitized carburizer is graphitized by high temperature treatment, and the carbon molecular morphology changes from irregular arrangement to hexagonal arrangement at 3000 C. The graphite structure is most easily decomposed in molten iron because of its high fixed carbon content, high absorption and less impurities.

Disadvantage: The price is on the high side, domestic steelmakers use less, but in the smelting of high-quality steel will be used.



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