JPH059551A - Deoxidizer for molten iron and molten steel refining - Google Patents

Abstract

PURPOSE:To expedite deoxidation and desulfurization without the increase of [C] and the increase of [Si] by pulverizing Ca-Si powder and carbon powder as a deoxidizer in a method of diffusion deoxidation and specifying both mixing ratio. CONSTITUTION:A deoxidizer scattered on slag in the stage of reduction refining for molten iron and molten steel is essentially constituted of Ca-Si powder and carbon powder. Then, the main distribution of each grain size of the Ca-Si powder and carbon powder is regulated to <=0.15mm, and both mixing ratio is regulated to (1:0.5) to (1:4). At the time of pulverizing the carbon powder as the above-mentioned manner, the increase of [C] does not occur, and the rate of reaction is promoted in accordance with the improvement of its diffusivity at the time of scattering. Furthermore, there occurs a tendency that, in accordance with the pulverizing of Ca-Si, its combustibility in the slag improves, but, in the case it is the fine powder of <0.15mm, it burns explosively, and it is dangerous. As for the mixing ratio of the Ca-Si powder and carbon powder, in the case of more than the upper limit, there is no great difference compared to the case of carbon powder only, so that the effect of the fine powder Ca-Si can not be obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a deoxidizer used in the steelmaking process of steel.

[0002]

2. Description of the Related Art Generally, deoxidation refining is performed in the refining process of molten iron and molten steel, and the method is roughly classified as follows. (A) Deoxidized metal (Ca, Al, Si, Mn,
Etc.) (forced deoxidation) (b) Method of exposing molten steel to vacuum (vacuum deoxidation) (c) Deoxidizing slag (reducing FeO) and deoxidizing molten steel in contact with the slag Method (diffusion deoxidation) The present invention belongs to the above (c), but conventionally, in this field, carbon powder, Ca-Si powder particles, etc. are used as a deoxidizing agent for slag, and these are sprayed on the slag. The general method is to proceed with deoxidation.

[0003]

The above-mentioned prior art has the following problems. (B) When deoxidation refining is performed only with carbon powder, the rate of deoxidation reaction is slow, and especially in molten steel containing little Si, Mn, Al, etc., it is very difficult to reduce the oxygen content to 50 ppm or less. There are difficult ones. Furthermore, the particle size of the charcoal powder is large
In the case of (about 0.15 mm or more), there was a drawback that increased [C] of molten steel.

(B) Ca-Si is usually about 8 mesh (2-
(3 mm or more) is commercially available, but the oxidative combustion in the slag is slow, so that the chances of contact with molten steel as metal Si increases, and [Si] increases. Therefore low
Not suitable for [Si] material. Further, it has a drawback that the reaction rate is slow even in the case of steel types in which the increase of [Si] does not matter.

(C) Even if a mixture of both is used, the above-mentioned defects (a) and (b) are hardly improved. When the above problems are sorted out, it is considered that the slow oxidation reaction of each deoxidizer causes [C] increase, [Si] increase, and refining time becomes longer.

Therefore, as a means for increasing the reaction rate, an attempt was made to finely powder the deoxidizer. (1) First, for charcoal powder, finer than 100 mesh
It was confirmed that the increase in [C] was eliminated by setting (0.15 mm or less). Furthermore, the effect of promoting the reaction rate was observed with the improvement of the diffusivity at the time of spraying by pulverization.

(2) Next, a study on Ca-Si was conducted. When commercially available Ca-Si (0.4 mm to 3 mm) was crushed and used, the flammability in the slag tended to gradually improve, but 100 mesh (0.15 mm)
It became clear that the finer the powder, the more explosive it would be when it was sprayed in the furnace (or the ladle), and it was dangerous.

[0008]

The present invention has been made to solve these problems, and it has been found that diluting the Ca-Si concentration is effective as a method for preventing deflagration, and the present invention has been made. It came to. That is, Ca-S
i When carbon powder is mixed with fine powder, the carbon powder is Ca-S by volume ratio.
Since the deflagration disappeared when the amount of i exceeded 1/2,
As a result of pursuing an optimum mixed powder of Ca-Si + carbon powder, Ca
-Si carbon powder particle size is 100 mesh or less (particle size 0.15 m
m or less) (however, even if some large particles are included, the effect is not adversely affected). The mixing ratio of Ca-Si powder: charcoal powder is (1: 0.5) to (1 :).
4).

[0009] The conclusion was obtained as described above, and the solution was obtained. The upper limit of the charcoal powder ratio is defined here, when Ca-Si is further reduced, there is no great difference from the case of only charcoal powder,
This is because the effect of fine powder Ca-Si cannot be obtained.

[0010]

The Ca-Si fine powder having the above-mentioned particle size is mixed with the carbon powder fine powder and sprayed on the high-temperature slag to obtain the Ca-Si fine powder.
Fine powder of burns. The combustion promotes the burning of charcoal powder,
Slag deoxidation proceeds. In addition, there is no increase in [Si] and increase in [C], the progress of diffusion deoxidation and the promotion of desulfurization can be obtained in a short time, and as a result, highly clean molten steel can be obtained.

[0011]

Embodiments of the present invention will be described below with reference to FIGS. Molten steel amount of 3.5% NiCrMoV steel 80-1
20 Ton was refined in a ladle refining furnace. In this case, 0.5 kg / T. Ca-
The amount of Si used is 0.4 kg / T. As shown in FIG. 1, as the grain size No of the carbon powder and Ca-Si powder increases, the degree of increase in [C] and [Si] decreases.

Molten Steel Amount of 3.5% NiCrMoV Steel 12
0 Ton was refined in a ladle. At that time, as the deoxidizing agent, the conventional method is a mixture of Ca-Si of 8 mesh and carbon powder of 200 mesh in a ratio of 1: 2, and the method of the present invention is C of 200 mesh.
It is a one-to-two blend of a-Si and 200 mesh carbon powder. The amount of the deoxidizer used was 0.5 kg / Ton of the conventional method and 0.5 kg / Ton of the present invention, and the spraying was carried out almost uniformly over 180 minutes. The refining time and the transition of the [S] amount in this case are shown in FIG. The method of the present invention achieves [S] level,
It is clear that the refining time has improved significantly. The changes in the refining time and the amount of [O] under the same conditions are shown in FIG. 3, and in this case as well, the method of the present invention shows remarkably good results.

[0013]

EFFECTS OF THE INVENTION (a) Deoxidation and deoxidation [S] were accelerated, and the time was shortened by about 50% as compared with the conventional method. (B) Achievement levels of deoxidation and deoxidization [S] up to [S] 0.0004% (conventional 0.002%) and [O] up to 30 ppm (conventional 50
ppm) became possible. (C) There is no increase in [Si] during refining. (D) Since the operation time was shortened, the wear of refractory materials was reduced. In addition, these effects are due to the addition of Ca-Si and Fe as deoxidizing metal.
The same can be obtained by using -Si and Si-Mn.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention, and is a diagram showing the particle size of Ca-Si and carbon powder and the state of component increase. FIG. 2 shows an embodiment of the present invention. ] Diagram showing changes in quantity,
FIG. 3 shows an embodiment of the present invention. Refining time and [O]
It is a figure which shows the change of quantity.

Claims (1)

Claims: 1. A deoxidizing agent sprinkled on slag in the reduction refining process of molten iron / molten steel has Ca-Si powder and carbon powder as main components, and the respective particle sizes are both A deoxidizing agent for refining molten iron and molten steel, characterized in that the main distribution is 0.15 mm or less, and the mixing ratio of Ca-Si powder and carbon powder is 1: 0.5 to 1: 4.