JPH0135885B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a recarburizing agent for steel manufacturing. Various types of carburizing agents are currently used, but some have advantages and disadvantages, such as some having too low a specific gravity and floating during melting and not being sufficiently mixed, and others using binders that are too expensive to be practical. Ta. In other words, the specific gravity of beans that are mostly carbon, such as charcoal, is too low.
PVA (polyvinyl alcohol) and CMC (carboxymethylcellulose), which are organic substances, can be used as binding agents in very small amounts (approximately 1%) because they have a large binding force, but it is difficult to mix such small amounts uniformly throughout the product. Moreover, since PVA and CMC are very expensive, they are not practically suitable for applications where they are used in large quantities, such as recarburizing agents for steelmaking. The present invention aims to provide a method for producing a recarburizing agent that solves the above-mentioned problems, and the gist thereof is as follows:
Granular pig iron or granular steel with a grain size of 3 mm or less obtained from various slags or dust generated in the pig iron making and steel making processes30
3 to 8 parts by weight of bentonite as a binder is added to 100 parts by weight of a mixture of ~70% by weight and the balance is carbon powder with a particle size of 3 mm or less, and the water content at the time of molding is 5 to 100 parts by weight. This is a method for producing a carburizing agent characterized by adding 10% by weight of bentonite and forming it into a lump after mixing. Less than half of the bentonite used as a binder may be replaced with CaO. obtain. The granular pig iron used here is blast furnace slag,
It refers to granular pig iron that is selected from slag produced in outside-furnace smelting processes such as hot metal desulfurization and desulfurization, and iron pig iron obtained from these slags usually contains 3 to 4% carbon by weight. When it is used as a component of a recarburizing agent as described above, it has the advantage that dissolution in the molten metal progresses rapidly. In addition, granular steel refers to granular steel selected from steelmaking furnace slag or converter dust of a converter or electric furnace, and these granular steels can be used when the recarburizer according to the present invention is used at the final stage of the steelmaking process. This is because it is convenient, that is, at the final stage of the steelmaking process, it is better to use granular steel, which has low P and S content and has already become steel, rather than using pig iron with high P and S content. The series of tests that led to the development of the present invention and their results will be described below. First, typical compositions of the various raw materials used are shown in Tables 1 and 2 below.

【table】

[Table] Three types of samples, Nos. 1, 2, and 3, were prepared by blending these raw materials in the proportions shown in Table 3 below.

[Table] The units in Table 3 are 100% by weight for granular pig iron, granular steel, coke powder, and Fe-Si.
Bentonite and lime are parts by weight when the total of granular pig iron, granular steel, coke powder, and Fe-Si is 100 parts by weight. 6 to 9% by weight of water was added to each of the samples as shown in Table 3, and after mixing, a lump material was formed using a compactor to obtain a recarburizing agent as a product. The properties of the obtained recarburizer are shown in Table 4 below. Note that the product numbers in Table 4 indicate the product recarburizing agents obtained from the above samples with the same numbers (the same applies hereinafter).

[Table] The carburizing agent obtained by the method of the present invention undergoes an exothermic reaction mainly due to the oxidation reaction of iron during its mixing and agglomeration (agglomeration), and the temperature immediately after the agglomeration is 90 to 100℃. Therefore, there is an advantage that the product carburizing agent is cured by itself with this heat, and Table 5 below shows the change in water content in the product carburizing agent over time showing the degree of curing.

[Table] Next, sample No. 1 obtained by the above method and miniature charcoal with a carbon content of 87% by weight as a comparison sample were placed on the bottom of a molten steel ladle, and molten steel was poured over them. As a result of comparing the carburization effect by boiling in hot water, the carbon content yield of the comparison sample, bean charcoal, was 51%, while that of invention sample No. 1 was 57%.
It was a big improvement. There are various ways to use the carburizing agent, such as placing it on the ground as described above, and pushing it into the molten metal. Depending on the method, there is a large difference in the carbon content yield, but the method described above It should be added that the method of simply placing the sample and using it without any stirring generally has a low yield, and the 57% yield of sample No. 1 of the present invention is on the high side. By the way, when the particle size of the carbon powder such as granular pig iron, granular steel, and coke used in the present invention is larger than 3 mm,
First, it is difficult to apply molding pressure during molding, making it difficult to obtain a product with sufficient strength.Additionally, the product has drawbacks such as difficulty in melting when used as a carburizing agent. The reason why the blending ratio of granular pig iron and granular steel is set to 30 to 70% by weight is because if these are less than 30% by weight, the specific gravity of the recarburizer obtained will be small and will float on the slag or remain in the slag. If it exceeds 70% by weight, the carbon content will be insufficient and the carburizing effect will also be reduced. If the amount of bentonite is less than 3 parts by weight, the grain quality will not be sufficient as a whole, and if it is too large, and if it exceeds 8 parts by weight, it will be difficult to apply molding pressure during molding, so it should be 3 to 8 parts by weight. do. Next, the amount of water is set at 5 to 10% by weight in order to ensure that sufficient pressure is applied during molding. In addition, lime is used in combination with bentonite because bentonite has a low CaO content, so lime is used to adjust the composition and has considerable binding properties by itself. It should be 1/2 or less. As described above, according to the method of the present invention, all of the above-mentioned various raw materials are made by utilizing various slags or dusts that are normally used only in landfills, or bentonite, which exists widely throughout Japan, and It self-cures through its own oxidative exothermic reaction without the need for special curing equipment or a curing place, and hardens solidly.The resulting recarburizer contains a large amount of iron, so it must be handled by hanging using magnetic force. A transporter can be used, and when it is actually used as a carburizing agent, as is clear from Table 4, it reacts well with the molten metal because it has a higher specific gravity than molten slag and quickly reaches the molten metal surface. It shows a high carburizing effect.

Claims (1)

[Scope of Claims] 1. 30 to 70% by weight of granular pig iron or granular steel with a particle size of 3 mm or less obtained from various slags or dust generated in pig iron making and steel making processes, and the balance being carbon powder particles with a particle size of 3 mm or less. To 100 parts by weight of the mixture, add 3 to 8 parts by weight of bentonite as a binder, and add water such that the water content at the time of molding is 5 to 10% by weight, and after mixing, mold into a lump. A method for producing a recarburizing agent characterized by: 2 100 parts by weight of a mixture of 30 to 70% by weight of granulated pig iron or granulated steel with a particle size of 3 mm or less obtained from various slags or dust generated in the pig iron making and steel making processes, and the balance of carbon powder particles with a particle size of 3 mm or less. On the other hand, a total of 3 to 8 parts by weight of bentonite and lime, which is less than 1/2 of the bentonite, is added as a binder, and water is added so that the moisture content at the time of molding is 5 to 10% by weight, and mixed. A method for producing a recarburizing agent, which is characterized in that it is then molded into a lump.