RU2016075C1 - Method for carburization of pig iron - Google Patents

Abstract

FIELD: ferrous metallurgy and foundry. SUBSTANCE: molten pig iron during its pouring into ladle and from ladle is passed through carburizer installed in channel found in ladle hollow. EFFECT: degree of carbonization is increased by 5-9%. 5 dwg

Description

 The invention relates to ferrous metallurgy and foundry, more specifically to methods for carburizing cast iron.

 The aim of the invention is to increase the degree of assimilation of carbon carburetor, and at the same time increase the carbon content in cast iron, reducing the consumption of carburetor and the cost of cast iron.

 Figure 1 presents a General view of the bucket; figure 2 - the time of casting iron from the smelter (cupola, induction furnace) into the bucket; figure 3 - the moment of discharge of metal from the bucket and pouring the mold; figure 4 is the same, node I in figure 3; figure 5 is a section of the casting ladle for the implementation of the proposed method, (figure 2, 3 is a diagram of carburization).

 The method is carried out in a casting ladle (figures 1, 5). The bucket consists of a housing 1, a lining 2, a tilting and lifting mechanism, a slag-separating partition 3. A slag-separating partition 3 and a ladle lining 2 form a drain channel 4, which at the same time is a channel for pouring pig-iron into the bucket.

 The drain channel 4 is filled with lumpy carburetor 5 (coke, electrode fight, carbon chips, coal tar pitch, etc.). The carburetor layer is blocked from above and below by refractory perforated partitions 6 with channels 7 for the passage of molten iron. Partitions 6 are sealed in the drain channel using chamotte paste 8. Partitions can be made of any refractory material (fireclay, high-alumina refractory, mullite, carbon refractories, etc.). Partitions are used to prevent the carburizer from being washed out of the drain channel by a liquid metal stream, and to reduce the loss of carbon-containing material.

The method is as follows. Before melting in the drain channel 4 of the bucket, the lower partition is mounted, a layer of a carburetor is poured on it (pieces 20-100 mm in size, depending on the capacity of the bucket). Then cover the layer with the upper partition 6 and close it with refractory paste. After that, the bucket and drain channel are dried and heated with an injection gas burner to 500-800 ^о С.

 When the metal is released from the melting unit, the stream from the trough 9 is directed into the drain channel 4 (Fig. 2). Metal through the channels 7 of the partition 6 enters the layer of the carburetor 5, where it is carburized, and then enters the bucket. After filling the bucket, it is transported to the place of pouring molds 10 and the metal is drained into the mold (Fig. 3). The metal is also drained through the drain channel 4, which ensures double filtration of the liquid metal through the layer of the carburizer when pouring and draining the metal. During the discharge of metal through the drain channel, secondary carburization of cast iron occurs. The carburizer layer can be used several times. As the carburetor is used up, it can be replenished, for which they remove the upper partition, fill in pieces of carbon-containing substances, and reassemble the partition.

 The method allows to increase the degree of assimilation of carbon carburetor.

A positive effect is ensured by the following:
when the metal is double filtered through a single channel filled with a carburizer, the contact time of the reacting phases doubles, which contributes to the development of diffusion processes of carbon dissolution in cast iron. This helps to increase the efficiency of the process and increase the degree of assimilation of carbon carburetor;
when liquid metal flows through the carburetor layer in both directions, good conditions arise for mutual mixing of the reacting phases due to their intensive movement relative to each other, which increases the degree of assimilation;
when liquid metal flows through the layer of the carburizer, the metal flow is turbulized. In a turbulized flow, carburization processes are more intense, which has a positive effect on increasing the degree of assimilation;
turbulization of the metal flow helps to detach micro- and particulate carbon-containing substances from the carburetor pieces that are effectively dissolved in the metal during metal accumulation;
the presence of a certain period of time after the first filtration (during the period of accumulation of metal in the bucket) contributes to the flow of diffusion processes of dissolution of particles of the carburizer in the liquid metal;
secondary filtration of the metal through the layer of the carburizer helps to increase the degree of assimilation of the carburizer not only due to the above factors, but also due to the fact that the layer of the carburizer is heated due to the heat of the metal filtered during filling of the bucket to a high temperature (1100-1300 ^о С). This contributes to the activation of dissolution processes and increase the degree of assimilation of the carburizer.

 In the end, the degree of assimilation of carbon carburetor increases by 5-8%. Since the carburetor with repeated use of the bucket can be completely consumed, in this case, the utilization rate of the carburetor can reach a value close to 100%.

PRI me R. Carbonization of cast iron in a ladle of 50 kg, melted in a gas cupola 0.5 t / h, was carried out. The composition of the source iron,%: carbon 3.05-3.10, silicon 1.3-1.4, manganese 0.4-0.5. Temperature 1420 ^о С.

 The carbonization foundry bucket had a baffle forming a drain channel with the walls of the lining. An electrode battle in pieces of 15-20 mm in size was loaded into the funnel. The layer of electrode battle was blocked from above and below by refractory perforated partitions with openings with a diameter of 10 mm.

Bucket before releasing metal warmed to 500-600 ^C. injectate gas burner. Cast iron from a cupola was released through a notch with a diameter of 15 mm into a drain channel filled with electrode battle. Then, after filling the bucket and a short exposure (0.5 min), the iron was poured through the drain channel and the molds and samples were poured. The carbon content after carburization of 3.5%. The carbon assimilation rate of the carburizer is 1.14, which is 4.7-8.5% more than in the prototype method.

The present invention provides, in comparison with the prototype, the following technical and economic effect:
the degree of assimilation of carbon carburetor increases (by 5-8%);
it is possible to obtain high-carbon cast iron (up to 3.4-3.6%);
the use of expensive equipment (transformer, current leads, contact plates, etc.) and additional fuel (electricity) is excluded;
carburetor consumption is reduced (by 10-15%);
it becomes possible to reduce the cost of charge materials through the use of cheaper low-carbon cast irons (by 5-10%).

 The method is simple to implement, effective and will find application in the iron and steel industry and foundry for carburizing cast iron.

Claims (1)

 METHOD FOR CARBONIZING IRON IN THE DUCK, including supplying molten metal to the ladle through the layer of the carburizer, characterized in that, in order to increase the degree of carbon assimilation and reduce the consumption of the carburizer, the molten metal is passed through the layer of the carburizer when it is poured into the ladle and drained from the ladle, while the carburetor is placed in a channel located in the bucket cavity.

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