JPH0238508A - Production of low phosphor and sulfur pig iron for foundry - Google Patents

Abstract

PURPOSE:To stably produce a low P and S pig iron for foundry regardless of P and S levels in raw material by executing de-Si, de-P and de-S treatments in a part of the molten iron, adding Si to the remained molten iron and after that, merging both treated molten irons into one molten iron. CONSTITUTION:The molten iron having about 1/10-1/2 of the total quantity of the pig iron for foundry is received into a torpedo ladle car, etc., and de-Si and de-P, de-S treatments are executed. Si content adjusting agent of Fe-Si, etc., is added to the remained molten iron, to increase Si content, and this molten iron is tapped into a vessel storing the above low Si, P and S molten iron to merge both molten irons. By this method, the low P and S pig iron for foundry can be easily produced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for economically producing foundry pig iron with low P and S concentrations by processing hot metal after tapping in a blast furnace. .

[Prior art] Foundry pigs include pigs for gray cast iron, pigs for malleable cast iron, pigs for 6-spheroidal graphite cast iron, etc., and their compositions are based on JIS-G.
As shown in -2202, the Si content is high at 3-4%,
The amount of P is required to be 0.1% or less, and the amount of S is required to be 0.05% or less.

As described above, the Si content is high and the P content and S content are low compared to the composition of the iron just tapped from the blast furnace, so the blast furnace tapped iron cannot be used as foundry pig iron under normal blast furnace operating conditions. Therefore, in the past, the P and S concentrations were determined by considering the P level and S level in the raw materials charged to the blast furnace (coke, sintered pellets, ore, pulverized coal, etc.) and devising the blending ratio of each raw material. On the other hand, the Si concentration in the hot metal will be reduced by adopting a high coke ratio operation with an increased amount of charged coke.
I am trying to raise the if.

However, in recent years, blast furnaces have tended to use more ores and coal with high amounts of P and S due to the depletion of high-grade raw materials or for the purpose of proactively reducing production costs.

As a result, the P-3 level in the hot metal rises, creating a situation in which foundry pig iron with the target P-S level cannot be manufactured even if the raw material blending ratio is modified. Also, in the field of foundry pig iron, there is a tendency for hot metal with a lower P-S level to be required.

[Problem to be solved by the invention] The present invention has been made focusing on these circumstances,
Foundry pig iron with low P and S content, i.e. high Si, low P, low S
The purpose of this invention is to provide a new method for producing pig iron economically.

[Means for Solving the Problems] The method of the present invention, which has achieved the above object, prepares low-Si, low-P, and low-S pig iron by performing Si-free, P-free, and S-free treatments, while requiring no preliminary treatment. The first point is that Si is added to pig iron to prepare high-Si pig iron, and this is combined with the low-Si, low-P, and low-S pig iron to dry it. The second key point is that low-Si, low-P, and low-S pig iron is prepared by the injection method, and Si is added to it by the injection method. This is an effective method for manufacturing. Among these methods, the former method can be called a temperature-matching method and is suitable when economic efficiency is more important, while the latter method can be called an injection method and can further reduce P-3. It can be said that this is a suitable method for measuring.

[Effects] Regarding the former temperature control, hot metal in an amount of about 1/10 to 172 of the total amount of foundry pig iron to be produced is received from a blast furnace into a pig iron mixer, etc., and then dephosphorized. Get rid of it!
Perform A process. From the viewpoint of deP treatment efficiency, when the amount of Si in the hot metal is high, the deP reaction proceeds more preferentially than the deP reaction, so the effect of the deP treatment does not improve.

That is, there is a relationship as shown in FIG. 1 between the Si concentration and the P concentration in hot metal, and in the region where the Si concentration is high, even if PIA removal treatment is performed, the degree of decrease in the P concentration is small. On the other hand, Si concentration 0
In the region of 0.8% or less, the P concentration is efficiently reduced by blowing in the dephosphorizing agent, and P is trapped in the slag. Therefore, it is desirable to perform a Si-removal treatment beforehand in the P-removal treatment, and the Si-removal treatment may be carried out in a cast bed, a pig iron mixing car, or the like. Also, after the Si, P, and S removal treatments, p20. Slag containing a large amount of
Therefore, it is desirable to remove the Si-free slag after the 5tIA process and to remove the P/S slag after the P-S process. The relationship between the amount of residual slag and the amount of recycled P is as shown in FIG. 2, and it is desirable to keep the amount of residual slag as small as possible in order to prevent the amount of recycled P. In this way, low-Si, low-P, and low-S pig iron is prepared in the mixer car, etc., while blast furnace hot metal in an amount of about 172 to 9/lO of the foundry pig iron to be manufactured is transferred from the blast furnace via the above-mentioned pig iron mixer car or pig iron mixer car. The low-Si, low-P, and low-S pig iron is tapped into a storage container and subjected to combined drying. At this time, a Si content regulator such as Fe-5i is added to the blast furnace hot metal to increase the Si content, and then the hot metal is mixed with low Si, low P, and low S pig iron. After the mixture has dried, bubbling stirring may be performed if necessary for the purpose of sufficiently mixing the hot metal.

Through such operations, it is possible to produce foundry pig iron with a high Si content and low P and S content.

In the method of the present invention, there are no particular restrictions on the type of hot metal treatment agent such as a desiliconizing agent;
Examples of the agent include Fe2O3, and examples of the dephosphorization agent include C.
aO, Na2Co3, etc., and CaC2 as a desulfurization agent.
etc. are exemplified respectively. In particular, as mentioned above, for the purpose of preventing P reversion during heating when combining with high Si pig iron, it is recommended to remove phosphorus-free slag etc. before combining with high-Si pig iron. In fact, this slag removal operation is so important that it can be said to hold the key to success or failure. Therefore, it is recommended to increase the emotionality of the slag to improve its deslagination properties, and from this point of view, N
It is desirable to use o, co3.

On the other hand, in the latter injection method, the entire amount of foundry pig iron to be produced is tapped from the blast furnace to a pig iron mixing car, etc., and the tapped hot metal is subjected to the same de-SI, de-P, and de-S processes as described above.
After fi filling, a 5tft modifier such as Fe-8i is added to it using the injection method to achieve high Si, low P and Si! All six hot metals are molten. In this method as well, the procedures for hot metal treatment and the importance of slag removal operations are the same as described above, and it is desirable that the treatment agents used in these hot metal treatments be those exemplified above. In addition, when injecting the Si content adjusting material, it is recommended to add lime in advance for the purpose of suppressing re-P.

Such an injection method can obtain foundry pig iron with lower amounts of P and S compared to the temperature properties. On the other hand, in the case of matching temperature, it is not necessary to apply hot metal treatment to the entire amount of foundry pig iron, so if the target P-3 amount is not so low (if the target P-3 amount is not so low) The advantage of this method is that it allows foundry pig iron to be produced economically.

Of course, in addition to the above features, the present invention has more basic features,
The component composition is shown in Table 1 N, with the advantage that there is no need to adjust the amount or ratio of charge material used in blast furnace operation.
It was as shown in 013.

Next, gas was blown into the pig iron mixing car and bubbling agitation was performed to obtain 298 tons of foundry pig iron having the composition shown in Table 1, No. 4.

This can contribute to improving the stability of blast furnace operation. Further, by the treatment after blast furnace tapping, it is possible to easily and stably produce low P/S foundry pig iron, and it is also possible to improve the dispersion of the components.

[Example] Example 1 117 tons of hot metal having the composition shown in Table 1, No. 1, was tapped from a blast furnace to a mixer car, and Fe20319J/l, Ca04
Sequential desulfurization using 0kg/l and CaC21kH/l, respectively.
When each treatment of i, de-P, and de-S was applied, Table 1 No. 2
Hot metal having the composition shown in was obtained. After removing Sl and removing S
Afterwards, a slag removal operation was carried out in each case.

On the other hand, when 181 tons of blast furnace molten pig iron having the composition shown in Table 1 No. 1 was added to the mixer car containing hot metal having the composition shown in Table 1 No. 2, and the blast furnace molten pig iron flowing through the hot metal gutter was After adding 300 kg/l of Fe-515, a mixing bath was carried out. Furthermore, Fe-5t 5300kg/l
Table 1 Example 2 280 tons of hot metal having the composition shown in Table 2 N011 was received in a pig iron mixing car, and the amount of FC20320kg/t, Na2CO
When the membrane Si, P and S removal treatments were performed sequentially using 36 kg/l and Ca C at 21 kg/l, the second
Hot metal shown in Table No. 12 was obtained. After removing Si and removing S
Afterwards, the slag was removed from each case. Then, Fe-313 was introduced into the treated hot metal in the pig iron mixing car using Ar gas as a carrier gas.
When 4kg/l was injected, Table 2 No.
, 282 tons of foundry pig iron having the composition shown in 3 were obtained.

[Effect of the invention] The present invention is configured as described above, and the P of the blast furnace charging raw material is
- It is now possible to produce foundry pig iron with low P/S without paying attention to the S level. In other words, we succeeded in overcoming the deterioration in raw material quality and easily and stably producing foundry pig iron with a low P/S level.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the amount of Si and the amount of P, and FIG. 2 is a graph showing the relationship between the amount of residual slag and the amount of returned P.

Claims (2)

[Claims] (1) Low Si and low P by removing Si, P, and S.
・While preparing low S pig iron, Si is added to non-pretreated pig iron to prepare high Si pig iron, and this is combined with the low Si, low P, and low S pig iron and hot water is produced. Method for manufacturing pig iron for S castings. (2) Low Si and low P by removing Si, P, and S.
- A method for producing low P/S foundry pig iron, which is characterized by preparing low S pig iron and adding Si to it by an injection method.