JPH01195241A - Method for refining high cu, sn-containing molten iron - Google Patents

Abstract

PURPOSE:To effectively remove Cu and Sn from high Cu, Sn-contg. molten iron and to extend the degree of freedom on the use of starting material by treating the molten iron under reduced pressure, regulating the pressure to a practical degree of vacuum and feeding a specified amt. of oxygen at a specified flow rate to form a local high-temp. region. CONSTITUTION:High Cu, Sn-contg. molten iron contg. >=0.10wt.% Cu and >=0.02wt.% Sn is treated under reduced pressure and the pressure of the atmosphere is regulated to <=3Torr. Oxygen is fed to the surface of the molten iron or into the molten iron by >=0.05Nm<3>/min/t-steel at >=50Nm/sec flow rate to form a local high-temp. region in the molten steel and the Cu and Sn are removed. Since the impurities are removed, a large amt. of low-cost commercial scraps can be melted in a steel manufacturing stage and the cost of manufacture of steel can be reduced.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention is directed to high-Cu, Sn-containing molten iron.
It concerns removal methods.

(Prior Art) Cu and Sn in molten iron are generally considered to be harmful as so-called tramp elements, except for some steel types, and their reduction has been desired.

On the other hand, in the steel manufacturing process using the blast furnace-converter method, the content of Cu and Sn in the iron ore used as the iron source is low, so the content of Cu and Sn in the molten iron is also extremely small, and these elements are removed and reduced. There was little need.

However, a recent technological trend in the blast furnace-converter method is the use of a large amount of six iron-containing materials in the converter, which makes it possible to reduce costs and improve production flexibility. At this time, it is cost-effective to melt a large amount of scrap, which is cheap iron-containing cypress material, especially so-called commercial scrap that is commonly distributed in the market.
“It is essential to reduce

(Problem to be solved by the invention) However, since the contents of Cu and Sn in commercial scrap are high,
The content of Cu and Sn in the molten iron produced has also increased, and a technology for efficiently removing these elements has been required.

Regarding the removal of Cu and Sn, only a few basic research results have been reported, and no examples have been put into practical use as industrial technology. The basic research results are “Tetsu to Hagane J”
; 51965), P, 1863;
This is an example of removing Cu and Sn under high vacuum. However, these high temperature and high vacuum conditions are at a level that is difficult to achieve as an industrial technology, and therefore it has not been put into practical use.

The present invention has advantageously solved these problems, and has been completed as an industrial technology based on the principle of vacuum removal of Cu and Sn.

(Means for solving the problem) That is, the gist of the present invention is that the Cu content is 0.1
High Cu with Sn content of 0% by weight or more and Sn content of 0.02% by weight or more
, Sn-containing molten iron is subjected to vacuum treatment, and the atmospheric pressure is reduced to 5.
Torr or less and oxygen blowing is performed to reduce oxygen to 0.
．． O5Nm3/min/t-steel or more at a flow rate of 53
This is a method for refining molten iron containing high Cu and Sn, which is characterized by removing Cu and Sn by supplying at a rate of Nm/sec or more to form a localized high temperature region.

The details of the present invention will be described below.

The present inventors developed Cu under high temperature and high vacuum.

We considered how to realize the principle of Sn evaporation removal as an industrial technology. As a result, Cu is produced by oxygen blowing in a practical vacuum range using reduced pressure processing equipment such as RH and DH, and by forming a localized ultra-high temperature region within the molten iron.

This led to the idea of a method for removing Sn. In other words, this method can locally generate 2,000
This is based on the basic idea that Cu and Sn can be removed by evaporation if an ultra-high temperature region of about 0.degree. C. can be formed.

Based on this idea, we conducted an experiment on a scale of 120 tons of molten iron and investigated the conditions under which Cu and Sn could be removed.

As a result, as shown in Figure 1, the practical degree of vacuum range is 5.
Below torr, oxygen is 0.05Na+3/wi
If more than n/t steel is supplied, Cu can be more than 50%,
It has become clear that 60% or more of Sn can be removed. From this result, even in a vacuum of about 5 torr or less, oxygen can be reduced to 0. If O5Nm3/min/t-steel or more is supplied, an ultra-high temperature region will be formed around the oxygen supply flash point, and C
It was found that u and Sn can be removed.

The experiment on a scale of 120 tons of molten iron was conducted in the following manner. Molten iron in the ladle (C: 0.1-0.5%, 51:
0.05-0.30%, Mn: 0.20-0.50
%, P: 0.01~0.03%, S: 0.01~
0.02%, temperature: 1600-1650°C) with metal C
Add u and Sn to increase Cu content from 0.10 to 0.50
%, after adjusting the Sn content to 0.02-0.10%,
RH treatment was performed. RH processing conditions are vacuum degree 1-20
torr, and oxygen was supplied (sprayed) through a lance installed in the upper part of the RH tank. RH processing time is 15~
The duration was 20 minutes.

Next, the reason for specifying the Cu and Sn contents will be described.

The present inventors investigated the removal effect of the method of the present invention and the Cu, Sn before treatment.
We investigated the relationship between content ranges. As a result, Cu
It was confirmed that the removal rate decreased significantly when O was less than 10% by weight and Sn O was less than 2% by weight. Therefore, it is desirable that the method of the present invention be applied to molten iron containing high Cu and Sn content of 10% by weight or more of CuO and 0.02% by weight or more of Sn. By the way, CuO, 1% by weight or less, SnO
,02% by weight or less, Cu and Sn have almost no effect on the quality of the steel material.

Next, the method of supplying oxygen will be described. Methods for supplying oxygen in a reduced pressure treatment apparatus such as RH include (1) a method of spraying from above the surface of the molten iron, and (2) a method of directly blowing into the molten iron. Either method can be employed in the present invention. That is, the present inventors used both methods to reduce oxygen to 0. O5Nm3/min/
t-steel or more, and the oxygen supply flow rate is 50
If Nm/sec or more is ensured, a local high temperature area will be formed and C
It was confirmed that u and Sn could be removed. Furthermore, according to experiments conducted by the present inventors, the oxygen supply flow rate was 5 Q Nm.
/sec or less, the temperature in the vicinity of the oxygen supply flash point did not rise so much and the effect of removing Cu and Sn decreased. Therefore, the oxygen supply flow rate must be maintained at 50 Nm/sec or more.

Examples and comparative examples of the present invention will be described below, and the effects of the present invention will be described.

(Example) In a 120-ton converter, 120 tons of molten iron having the composition shown in Table 1 was obtained using 70 tons of blast furnace molten iron and 50 tons of cloth scrap as main raw materials. The molten iron was charged into a ladle and subsequently subjected to RH treatment.

The RH treatment conditions were a vacuum level of 2 torr, and a lance in the RH tank to supply oxygen at a rate of 0.1ONm'/min/t-st.
I sprayed it with eel. At this time, the oxygen supply flow rate was 12ONm/s.
ec, and the treatment time was 20 minutes. Through this treatment, molten iron with the composition shown in Table 1 was obtained, with a Cu content of 0.3-0
．． 07%, and Sm significantly decreased to 0.05-0.015%.

(Comparison example) Oxygen supply conditions at RH are set to 0. (13Nm'/min/t
- steel s supply flow rate was set to 38 Nm/sec, and other conditions were the same as in the example, but the first
As shown in the table, the removal of Cu and Sn remained slight.

(Effects of the Invention) As described above, the present invention has made it possible to significantly remove Cu and Sn, which are undesirable when purchasing steel products.

This makes it possible to melt a large amount of inexpensive cloth scrap in the steelmaking process, reducing melting costs and increasing the degree of freedom in the use of raw materials, which is extremely beneficial to the steel industry.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the influence of the degree of vacuum and the amount of oxygen supply on the removal rate of Cu and Sn. Figure 1

Claims (1)

[Claims] Cu content 0.10% by weight or more, Sn content 0.02
The molten iron containing high Cu and Sn content of more than % by weight is subjected to depressurization treatment, the atmospheric pressure is reduced to 3 torr or less, and oxygen blowing is performed to produce 0.05 Nm^3/min/t-ste of oxygen.
A method for refining molten iron containing high Cu and Sn, characterized in that Cu and Sn are removed by supplying el or more at a flow rate of 50 Nm/sec or more to form a localized high temperature region.