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The role of petroleum carburizing agent as cast iron pretreatment agent in casting process

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The role of petroleum carburizing agent as cast iron pretreatment agent in casting process

Date:2017-09-16 Author: Click:

Petroleum carburizer 1, strong deoxidization, purify molten iron, reduce slag inclusion and porosity defects; reduce wall thickness sensitivity, make the microstructure compact, smooth cutting surface, significantly improve cutting performance.

As the presence of FeO lowers the melting point of any slag, at any given temperature, because the melting point of the slag drops, more slag becomes liquid. For example, when the content of FeO in the slag is 10%, its melting point will be 1350-1400 C. In addition, the liquid slag will be "homogenized" in the melt under the strong stirring of the coreless induction furnace, thus leaving tens of millions of very small slag particles in the melt. Many surface defects of the castings are high fluidity of FeO and Mn. O slag, commonly known as manganese silicate slag, is brought into the mold. If the FeO content of the slag is reduced to 1 or 2% due to the reduction reaction of the pretreatment agent, the melting point of the slag will be raised to 1500-1550 C, then the slag will remain solid at the usual tapping temperature (1500-1550 C), or only a small amount of the slag will become liquid, thus a large one. Monomers are retained in the furnace, which makes the slag particles easy to be removed because of the higher floating speed and leads them into the mold, thus greatly reducing the chance of casting defects.

The pretreatment agent can deoxidize the castings and react with the oxygen in the casting furnace in the smelting process, thus reducing the excess oxygen. It can also deoxidize the castings in the smelting process and in the front pack, thus reducing the formation of porosity and slag inclusion.

2. Increase fluidity, stabilize molten iron composition, prevent segregation and reduce defects in white and shrinkage.

The fine inclusion of FeO-SiO2 in molten iron is not easy to float out of molten iron, which is one of the important reasons for the decrease of molten iron mobility, the decrease of feeding capacity, the increase of shrinkage tendency and the obvious tendency of whitening. By adding pretreatment agent and ferric oxide, the pure molten iron can be reduced well, and its filling capacity and feeding capacity are enhanced.

3. Reduce the supercooled graphite in gray cast iron, promote the formation of A-type graphite, strengthen the control of graphite morphology and reduce the tendency of whiteness, thus optimize the mechanical properties of castings.

- There are high density dislocations around the pretreatment agent particles, and the crystallization increases so that the grain refinement, and changes the morphology of graphite, the length of graphite becomes shorter, the A-type graphite increases, the D-type graphite decreases, the number of eutectic clusters and the number of pearlite obviously improves.

4. For nodular cast iron, it is a strong deoxidizer. It can increase the number of graphite nodules, increase the nodularization rate, make the graphite nodules more rounded and fine, and reduce the amount of nodulizer.

Petroleum carburizing agent

As the content of FeO in ductile iron slag is higher than that in gray iron or vermicular iron slag, the problem caused by fluidized slag is more serious than that caused by gray iron or vermicular iron. Therefore, the effect of adding pretreatment agent to ductile iron is better.

5, enhance the graphite nucleation ability and increase the graphite core, effectively solve the incubation recession. It can create a long and stable core for the precipitation and growth of graphite, and has strong nucleation ability. It has the function of promoting and stabilizing nucleation, alleviating the melting of graphite core when molten iron is standing for a long time at high temperature (1520 ~1550 ~1550 ~1550 ~1550 ~1550 ~1550 ~1550 ~1550 ~1520 ~1550 ~1550 ~1550 ~1550 ~1550 ~1550 ~1550 ~1550 ~1550 ~1520 ~1520

6. Eliminate oxidation factors of iron melt, reduce lining oxidation and prolong lining life by 30% - 100%. When carburizing agent is used in casting, it can greatly increase the amount of scrap steel, reduce the dosage of pig iron or do not use pig iron. The feeding mode of electric furnace smelting should be that the carburizer should be put in with the scrap and other burden, and small doses of carburizer can be added to the surface of molten iron. However, large quantities of molten iron should be avoided to prevent excessive oxidation and carburization effect is not obvious and the carbon content of the casting is not enough. The amount of carburizing agent is determined according to the ratio of other raw materials and carbon content. Different types of cast iron are selected, and different types of carburizing agents are selected according to needs. Characteristic of carburizer itself choose pure carbon-containing graphitized material, reduce excessive impurities in pig iron, proper choice of carburizer can reduce the cost of casting production. The carburizing agent is suitable for smelting in induction furnace, but the specific use is different according to the technological requirements.

(1) The carburizer can be added to the lower and middle parts of the furnace according to the proportion or carbon equivalent requirement, and the recovery rate can reach more than 95%.

(2) If the carbon content is insufficient to adjust the carbon content, the slag in the furnace is cleaned first, and then the carburizer is added. Carbon can be dissolved and absorbed by heating up the molten iron, electromagnetic stirring or artificial stirring. The recovery rate can be about 90%. If the low temperature carburizing process is adopted, that is, the burden is only melted part, and the molten iron temperature is low, all the carburizer is used. The liquid is added into the liquid at a time and pressed into the molten iron with a solid charge so that it does not expose the surface of the molten iron. This method can increase carbon content by more than 1%.

2. carbon enrichment outside the furnace:

(1) Graphite powder is selected as carburizing agent for inner spraying of graphite powder in the ladle. The amount of carbon injected into the ladle is 40kg/t, which is expected to increase the carbon content of molten iron from 2% to 3%. With the increase of carbon content in molten iron, the utilization rate of carbon decreases. The molten iron temperature before and after carburization is 1600 C and 1299 C on average. In general, nitrogen is used as carrier for graphite powder carburization, but in industrial production conditions, it is more convenient to use compressed air, and oxygen combustion in compressed air produces CO. Chemical reaction heat can compensate part of the temperature drop, and the reduction atmosphere of CO is conducive to improving the carburization effect.

(2) 100-300 mesh graphite powder carburizer can be put into the ladle or flushed into the ladle with the flow from the tapping trough. After the molten iron is discharged, the carbon can be dissolved and absorbed as much as possible. The carbon recovery rate is about 50%.


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