JPS6059011A - Desulfurizing method of molten metal - Google Patents

Abstract

PURPOSE:To desulfurize efficiently a molten metal such as molten iron, molten steel or the like by adding a desulfurizer consisting principally of CaO contg. a relatively high concn. of CaF2 into a molten metal path without stirring or fluidizing the slag on the bath surface so that the main desulfurizting reaction is completed. CONSTITUTION:A desulfurizer contg. >=20wt% CaF2, more particularly 40wt% CaF2 and consisting of the balance CaO is added into a molten metal without fluidizing and stirring substantially the slab on the bath surface so that the main desulfurizing reaction is completed. The addition of the above-mentioned desulfurizer is accomplished by circulating only the molten slag in which the slag does not substantially exist through a circulating path 2 provided on the side face of a ladle 1 where the slag (ys) is made to exist atop the molten steel (y) therein as shown in the figures (a), (b) and adding and above-described desulfurizer through a blow port 4 to end the main reaction. The consumption of the desulfurizer is thus considerably reduced and the desulfurization is completed in a short time. The extra low sulfur steel is thus quickly, economically and efficiently obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for efficiently desulfurizing molten metal such as hot metal or molten steel.

[Prior art and its problems]

Recently, in the field of line pipe materials, marine tunnel construction materials, etc.
The requirements for hydrogen-induced cracking resistance and corrosion resistance are extremely strict (1?Lfi). It is necessary to reduce the content of nitrogen (S) as much as possible;
Oxygen (hereinafter referred to as O) and some thick plates also contain water pressure (hereinafter referred to as H).
and 1) t must also be reduced.

Hot metal desulfurization methods are broadly divided into hot pig iron desulfurization methods performed at the bath pig iron stage and molten steel desulfurization methods performed at the temperature control stage (8)≦20p.
In order to produce extremely low pm sulfur iron, desulfurization in a slag pot is especially necessary in addition to desulfurization at the bath iron stage. Conventionally, the well-known method for desulfurizing molten steel is the injection method, in which OaO-based composite mixtures and Oa alloys are blown into a broken pot together with a carrier gas. It is characterized by desulfurization through a strong slag-metal reaction. however,
In desulfurization treatment, which is mainly based on the slag-metal reaction with strong stirring like this method, rephosphorization from the dephosphorization slag and a decrease in the yield of addition of alloys such as IJ are likely to occur during the treatment, and the temperature drop is also relatively low. There are problems such as getting bigger. Furthermore, due to the turbulence rL on the bottom of the slag pan caused by strong stirring, absorption of gas components - especially I(, N) - into the atmosphere A, Sunta 4, etc. is unavoidable. H, N' like a board
In order to produce steel types that require a simultaneous reduction in power, degassing processes such as RH or A corresponding increase in the amount of processing is unavoidable, such as the need for superheating the bath steel, and furthermore, quality is often adversely affected.

Recently, as a means to solve these problems, a desulfurizing agent was injected into the ascending flow of hot steel into a vacuum chamber together with a carrier gas.
A treatment method has been developed that performs desulfurization and degassing at the same time.

However, in this method, the added desulfurization agent is mainly passed through a separate reaction tank through which the molten steel is introduced into the reaction vessel, and into the pot with the pot via the outlet W from the separate reaction tank. The reaction proceeds within a short period of time until reaching the target. In order to efficiently desulfurize using the same method as fc, what is the desulfurization rate in molten steel? A desulfurizing agent is needed that can maintain high temperatures. However, looking at the CIaO powder, which has been proposed as a desulfurization agent for the same method, 0aU-OaP2 powder, and 2-process mixture, it is found that the OaO powder remains normally even after being blown into it. Since it exists as a solid at steel-making temperatures of In addition, OaF2 is used as an additive to promote OaO sludge formation, but the commonly used additive 7JO ratio is necessarily less than 20% by weight of OaF2, and the composition within this range is indispensable. Even if OaO-OaF2 Itokomoto is used as a desulfurization agent, the desulfurization efficiency is only comparable to that of OaO. Furthermore, when a Ca alloy is used in the same method, the volatilization loss of Ca is large, so the desulfurization efficiency becomes rapid, and furthermore, the vaporized Oa may cause damage to the exhaust system. There is a need for arrangement.

[Purpose of the invention]

The purpose of the present invention is to solve the above-mentioned βυ problem 2 in the conventional desulfurization of molten metal, and to solve the basic unit of desulfurization agent? greatly reduced,
Moreover, desulfurization can be completed in a short time, and ultra-low sulfur steel 2'4 can be produced quickly, economically and efficiently.

[Structure and operation of the invention]

In order to solve the above-mentioned problems, the present inventors have desulfurized the i-unmei-shi, X is according to the reaction temperature, and in addition, rationally Various experiments and studies were conducted to find ways to obtain ultra-low sulfur steel with reduced reinforcement of H, N, etc. As a result, in the method of adding all the desulfurization agent to the molten steel, the first
As shown in the figure, when the cocoon content of bath steel [S] is 10 ppm or more, the desulfurization rate increases almost linearly with respect to the desulfurization agent consumption;
Desulfurization progresses as a rate-determining rate of desulfurization agent supply, and if there is virtually no slag or there is virtually no fluid agitation at the slag-metal interface (if the desulfurization agent is injected into the molten metal, the desulfurization rate per desulfurization agent layer unit will be reduced). As a result of further experimentation, we found that 0aF2 in the desulfurization agent increased as shown in Figure 2.
The higher the annual turnover, the more effectively desulfurization progresses.
For example, by injecting OaO-Oa Fz powder, a high desulfurization efficiency of 60% or more, which is unimaginable based on conventional knowledge, can be obtained with a desulfurization agent consumption of less than about Z5kq/lon of molten steel, and 0aF2 Even though the melting point decreases more rapidly when the temperature exceeds 40°, is this due to insufficient absolute amount of OaO or some other influence?

Although it is unclear, a high desulfurization rate exceeding 95% was not observed.

The present invention was made based on the above-mentioned knowledge, and
The feature is that the slag on the bath surface is effectively converted into VC.
Adding to the molten metal bath, without stirring or fluidizing, a treatment agent containing OaFz at a weight concentration of at least 20%, preferably 40%, and whose residual content is mainly OaO,
A method for desulfurizing molten metal, characterized in that the main desulfurization reaction is completed in the bath.

Hereinafter, an embodiment in which the present invention is implemented in defogging # steel will be described.

Since the treatment method according to this example does not use a slag-metal reactor, the slag is essentially made to flow and stir. There is also a method of refluxing the inside of the tank and finishing the main reaction before it returns to the ladle, as shown in & Figure 3 (a) and (b).

Slag ys & molten steel y in ladle 1 present on the top surface.

With the circulation path 2VC provided on the side of the ladle 1 and the electromagnetic pump 3,
Only the molten steel that is substantially free of slag is circulated through the circulation path 2, and the desulfurization agent containing 0aF2 at a weight concentration of 20 g or more is added from the inlet 4 to the outlet (4 of the 4-magnetic pump). As shown in Figures 4 (a) and 4 (b), the method for finishing the main reaction before leaving the IC is to add the desulfurizing agent to the heat convection circulation path 2 through the inlet 4, and then
A method was used in which the desulfurization reaction was completed while the molten steel was flowing down in the circulation path 2.

The position where the desulfurization agent is added/JO is not only the position shown in 1 but also the position where the molten steel flows towards the circulation path 2 which forms each circulation flow in the case of the RH method, preferably the Vi circulation path 2.
It is most preferable to inject the desulfurizing agent together with the carrier gas at a location away from the artificial circulation path 2, since this will not cause any agitation of the slag in the ladle 1.

The Oa Fz concentration in the OaO-based treatment agent that can be used as a desulfurization agent is shown in FIG. 2 above. Regardless of whether it is bright or not, it is sufficient if the weight concentration is at least 20 or more, but the desulfurization agent consumption rate is about 2. In order to stably obtain (8) 8 degree ultra-low sulfur steel with 5 kg/tonn copper steel and 5 ppm or less,

OaO-0aF2 containing 40 or more OaF1 is preferred. father.

Desulfurization agents come in powder, linear, mixed, and silimelt forms.

Any of them can be used, and the grains are not particularly limited, but within the range where an increase in economic burden is allowed in order to promote slag formation of the desulfurizing agent and increase the reaction interfacial area.

It is better to use something as fine as possible.

The addition of the desulfurizing agent can be started at any time after the molten steel has been deoxidized, and when treating molten steel that has not been deoxidized or has been slightly deoxidized, the addition of the desulfurizing agent (i- Desulfurization proceeds efficiently.

The atmosphere of molten metal without slag is not limited, but
Ar gas atmosphere is desirable for reducing gas components such as H, N, and 0 as much as possible.

Alternatively, it is preferable to use a reduced pressure state. Regarding the degree of vacuum in a reduced pressure state, in order to effectively perform degassing,
As long as the four major economic burdens are acceptable, the sieve vacuum is more desirable.

When injecting a desulfurization agent into molten steel, any inert gas may be used, but Ar gas is effective in reducing the concentration of gas components in molten steel. The conditions VC for blowing the desulfurizing agent are also not particularly limited. In order to effectively perform degassing at the same time as desulfurization, it is most preferable to use Ar as a carrier gas and maintain the reaction atmosphere in a reduced pressure state.

The present invention makes it possible to carry out the desulfurization reaction in an environment or atmosphere that is not affected by the slag on the top surface of the molten steel in the ladle, in a molten steel bath. A strong direct slag-metal reaction is not required, thereby virtually eliminating rephosphorization during processing and post-processing desulfurization resulting from slag flow and agitation.

There is no need for sludge removal or slag reformation before treatment, which is carried out in conventional molten steel desulfurization methods, making it possible to significantly reduce treatment costs. In addition, the corrosion of refractories in pots, reaction vessels, etc., which is a concern due to the use of large amounts of %OaFg, is reduced.Since the desulfurization of the present invention completes the main reaction in molten steel, the efficiency is lower than that of madder.
The unit consumption of desulfurization agent is greatly reduced, and there is no flow in the slag line.

As a result, the problem will be reduced to the point where it will not actually become a problem. In addition, there is no need to use salt-sealing pots to promote desulfurization ability, and the cost of refractory materials is greatly reduced.

〔Example〕

Embodiment 1 As an implementation of the present invention, as shown in Figure 5, the container is 1°, the circulation path is 2. Blowpipe Bt% tapping 5. Conduit 62 molten steel y.

1 using the equipment consisting of slag ys, and 1i as a comparative example using the equipment shown in Fig. 5 and using the same desulfurization agent addition method as the example of the present invention, Arashi tic + AiL 18 ToCD
The treatment using OaO-0aF2 containing OaF2 and OaOf as a desulfurization agent, and the container 1 and lid 11 shown in FIG. In the desulfurization method by injection of several sets consisting of blowing pipe Bt, molten steel y, and slag ys, 40
OaO-0aF2 including 0aFz k, &yohi0a
Desulfurization treatment was performed using Of.

Table 1 shows the desulfurizing agent composition and treatment conditions used in the Examples and Comparative Examples of the present invention.

In the present invention examples and comparative examples, (0]=o, t.

%±0.02%, (S i ]=0.20 X±o,
03 X 1['Mn)=0,'95%±0.03
% molten steel? When receiving the steel into the molten steel container, it was carried out through a sliding gate type nozzle at the bottom of the molten steel pot. Therefore, in the treatment using the equipment shown in FIG. show,
As an example of the change in (S) concentration in molten steel during treatment, A, O, E
The results of 2 and H are shown in Figure 7.

As is clear from Table 2 and FIG. 7, A, B, O, and D of Examples of the present invention have a desulfurization agent consumption of 2.5 k
7/ton of molten steel, with a treatment time of 10 minutes, a desulfurization rate of 60% or more and a sa saturation of 19 ppm or less were obtained.In particular, test No. 4 with a UaF2m content of 40% or more in the desulfurization agent, For A and O, the desulfurization rate is 809C or higher, and the slag pot LS] - 5 ppro is extremely low.
l,/ko. Also, like two anchors, A of the embodiment of the present invention.

B, 0. and D had little absorption of I(, N, etc.), and there was also a tendency for A and CAT'' to be dehydrogenated by the Ar gas blown in from the blowing pipe B!.

Furthermore, as is clear from the two nests, A of the embodiment of the present invention,
In B, O, and D, the rephosphorization during treatment was reduced to 10 p.
Below pm, [people in molten steel! ] Decrease in concentration k 40 pp
The temperature drop during treatment must be kept at 7°C or less.

In addition, as shown in the second picture, the molten steel after the treatment of the example of the present invention [
The O'll concentration was ~13 ppm''C.

On the other hand, in the comparative examples El and F, which were carried out using the equipment shown in FIG. 5, similar to the inventive examples, [1-1] .

[N] and [0] concentrations and post-phosphorus 1+i:s during treatment
Molten steel [A! ] Although the reduction in concentration, the amount of temperature drop, etc. were the same as in the examples of the present invention, it was not possible to obtain ultra-low sulfur steel like the examples of the present invention.

Comparative examples G and H using equipment noise shown in Figure 6 -
According to Figure 7 (1), the desulfurization agent consumption is 2.5 kW/ton bath S''AI, and the processing time is 10.
It was not possible to obtain a [S:l concentration of less than 20 ppm in minutes. Also, as shown in the second picture, [H] is being processed.

(N) and CP:] The increase in degrees was large, and the amount of decrease in [A]) degree and the amount of decrease in copper temperature were also large.

Embodiment 2 As an embodiment of the present invention, as shown in FIG.
(vacuum chamber), blowing pipe B! A vacuum degassing tank consisting of molten steel y and slag ys was used. Table 3 shows the conditions for blowing the desulfurizing agent at this time. Also, as a comparative example, using the equipment shown in Figure 8,
And under the same blowing conditions as in Table 3, the gravity is 18X%1
0aO-OaF2 system containing 3% 0aF2' and 0a (J
In the desulfurization method using simple ladle injection without combination of degassing treatment, M
0a(J-
Desulfurization treatment was carried out using OaF2 and OaOf as desulfurization agents in the fourth blowing process.

Examples of the present invention and comparative examples: Composition, temperature, temperature, B, and ultimate vacuum level of the flame used in the comparative examples The results are shown in the 6th section,
As an example of the change in C3OU degree in molten steel during processing, I, T,
, N, CI, E, 1: V) H, 5 results are shown in Figure 10.

As is clear from Fig. 6 and Fig. 10, I, J, K, T, , M, and N of the embodiment of the present invention
In addition, the desulfurization agent consumption rate is 2.5 kli/t on igi'
4. In a treatment time of 9 minutes, a desulfurization rate of 65% or more and a final condition [S] of 19 ppm or less were obtained in all cases. In particular, test No. I in which the degree of Oa F2 in the desulfurization agent is 40% or more
, J, and K have a desulfurization rate of 90% or more,
) Rebellion 5-6 J) I)m ultra-low sulfur steel was obtained. In particular, as is clear from Table 6, I of the embodiment of the present invention,
J, K.

Regarding L, M, and NVc, CH in molten steel after treatment
:l@degree is 0.8~1. Oppmr Rari, processing [
N] absorption is also low, and conversely, the molten copper [N] concentration before treatment is 35
In test T exceeding ppm k, there was no tendency for slight denitrification during treatment.Furthermore, as is clear from Table 5, I
, J, K, L, Il+4, Min and N, post-phosphorus during treatment is 40001% or less, molten steel [8]
] is the degree of decrease in all Q, below 006%, the temperature during processing? The temperature could be kept below 9℃.

In addition, as shown in the sixth column, after the treatment of the embodiment of the present invention, #
The concentration of Kin[0] was 8 to 13 ppm, while the 8th
O2P and Q″′ of the comparative example carried out with the equipment shown in the figure
C is the density of [H:] , [N) l [0] tatami after treatment, Fukurinhi during treatment, [AI! 3.The conditions such as humidity and low humidity were almost the same as in the previous example, but molten steel with extremely low sulfur content could not be obtained. T.

For U and V, molten copper [S) MS degree is 20pp
In order to obtain a desulfurization agent of less than 10 ppm, it is necessary to use three times as much desulfurizing agent as in the examples of the present invention, and as shown in Figures 46k, v, and 10, it is necessary to obtain [S] of 10 ppm or less even in cases of n. I couldn't. Furthermore, as is clear from Table 6, the absorption of gas components such as [1mu] and [to] during processing is large, and alloy fatigue such as wrinkles and [:AA] occurs. The decrease in concentration and bath temperature was also large. In addition, in R, S, T, U, and V of comparative examples, no difference was observed in the desulfurization behavior even if the Oa li'2 concentration of the desulfurization agent was changed.
'L wasn't there.

Note that each of the above-mentioned embodiments has explained the desulfurization of molten steel, but regarding the desulfurization of bath pig iron, Previous ij 2 Method of adding dehumidification agent and decompression, ■ Immerse a long #L tube pipe along the axis of the torpedo car inside the torpedo car, and run it from one end of this pipe to the other end.iiJ Md Method of desulfurization by injecting de-IJAe, ■ Continuous iron making and continuous steel making experimental equipment, connecting pipes for both processes (
A method of desulfurizing by injecting the desulfurizing agent into the conduit 6 (similar to the conduit 6 in FIG. 5)? 60% in a short time, similar to the molten steel desulfurization described above.
A high desulfurization rate of more than % was obtained.

〔Effect of the invention〕

As stated above, in the present invention, the weight concentration of molten gold is 20% in 5 baths. OaO0XIF' containing 0aFzk of X or more
2 Because the desulfurization agent is added, the desulfurization reaction is extremely fast, and the main desulfurization reaction is completed in the molten metal, eliminating the need for the conventional desulfurization treatment based on the very strong slag-metal reaction, and reducing the It is now possible to obtain extremely low sulfur in a desulfurizing agent unit and in a short time; metals can be obtained by shortening the processing time and reducing the temperature drop of molten metal, reducing the amount of base metal adhering to the container. 1 iron yield is improved, and significant effects such as resource and energy savings can be obtained.

Furthermore, in the above treatment method, the desulfurizing agent is completely inert gas and is blown into the molten metal as a carrier gas! /L: The desulfurization effect of the upper self can be further increased).

In addition, in the above treatment method, RH or D is used as the reaction environment.
A vacuum degassing tank such as H or an inert gas atmosphere? By using it, it becomes possible to perform degassing at the same time as desulfurization.

Also, hot metal desulfurization, steel making, molten steel desulfurization? If the present invention is implemented in each desulfurization process in series, the industrial effects of the present invention are extremely large, such as the continuous molten metal treatment process, which significantly shortens the time, reduces manufacturing costs, and improves manufacturing yield. .

[Brief explanation of the drawing]

Figure 1 shows the relationship between the desulfurization agent consumption rate and the desulfurization rate in the present invention? The graph shown in FIG. 2 is OaO-OaF in the present invention.
0aF29 degrees in 2-system desulfurization agent, desulfurization rate and reached molten steel [
几〕Relationship with concentration′? The graph shown, Figure 3 is a schematic diagram showing an example of a device implementing 8A of the present invention, (a) is a side view, (a) is a side view, (
B) is a plan view, Figure 4 is a schematic diagram showing another example of equipment in which the present invention is implemented, (A) is a side view, (B) is a plan view, and Figure 5 is the equipment used in Example 1. Figure 6 is a schematic diagram showing the equipment in which the ratio of softening of Qf to IAM1yllll was 0) f-1, and Figure 7 is a schematic diagram showing the equipment in which molten copper (S) was subjected to general processing in Example IK. Graph showing transition to 58, level 8
The figure is a schematic diagram showing the equipment used in Example 2, Figure 9 is a schematic diagram showing the equipment used in the comparative example of Example 2, and Figure 1O is a schematic diagram showing the equipment used in the comparative example in Example 21C. f&
It is a graph showing the change in copper C5) 9 degrees. Agent Patent attorney Masamitsu Akizawa and 2 others (Ro) Raku 3 Zuzetsu 4 Challenging Figure 7 Figure 8 Jofukuchi Hiroshi Figure 10

Claims (3)

[Claims] (1) At least 20% of the slag is added to the molten metal bath without substantially stirring or flowing the slag on the bath surface.
1. Violet contains 40% 0aF2, the rest is 0a
7JO is added with the treatment agent which is the main fraction, and the main desulfurization reaction takes place in the drop. A method for desulfurizing molten metal, characterized in that: (2) The method for desulfurizing molten metal according to claim 1, wherein a treating agent is blown into the molten metal using an inert gas as a carrier gas. (3) A method for desingnulating molten metal according to claim 1 or 2, in which degassing is carried out at the same time as desulfurization using a reduced pressure +L or inert force atmosphere as a molten metal tank. .