JPS61143505A - Refining method of high alloy steel - Google Patents

Abstract

PURPOSE:To reduce the consumption of FeSi for reducing alloy component oxides by producing a high alloy steel by using a top and bottom blown converter or bottom blown converter and blowing a reducing gas from a bottom blowing tuyere in the reduction refining period after decarburization. CONSTITUTION:The reducing gas such as H2 or CO is blown through the bottom blowing tuyere and is passed through the inside of the steel bath and slag in the reduction refining period after decarburization in the stage of producing the high alloy steel such as high chromium steel or high manganese steel by using the top and bottom blown converter or bottom blown converter. The above-mentioned reducing gas reduces the alloy component oxides such as Cr2O3 and MnO in the slag to reduce the fuel consumption of the FeSi to be charged for the purpose of reducing said oxides; at the same time, the S in the molten steel is desulfurized in the form of H2S anmd COS, by which the fuel consumption of the CaO to be charged for desulfurization is economized and the cost of refining is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for refining high-alloy steel, and more specifically, to refining high-alloy steel such as high-chromium steel and high-manganese steel using a top-bottom blowing converter or a bottom-blowing converter. This invention relates to a refining method for producing alloy steel.

Previous technology and its problems High chromium steel, using top-bottom blowing converter or bottom-blowing converter,
When manufacturing high alloy steel such as high manganese steel, it is important to know how to reduce the loss of chromium or manganese due to oxidation during the decarburization process. For this reason, AOD methods and the like have been developed for some time, in which decarburization progresses and a gas mixture of nitrogen and argon gas is injected into the molten metal along with the oxygenated carbon in the molten metal.

However, even in the conventional AOD method that promotes preferential decarburization, after decarburization, for example, in the case of high chromium steel,
15 kfA of chromium oxide is produced. For this reason, after decarburization, FeSi, etc. are introduced into the furnace to remove CrI! in the slag. 1! A commonly used method is to reduce and recover chemical compounds using SL. However, in the conventional recovery method, although Si is cheaper than Cr, it is still expensive, and 5i02 is generated and Cα0 is required to neutralize it, which increases the amount of slag. There are problems such as.

Purpose of the Invention The purpose of the present invention is to reduce oxides such as chromium or manganese during the reduction period after decarburization.
The object of the present invention is to obtain a method for refining high alloy steel that can reduce the basic unit of tSi.

The above object of the present invention is to inject reducing gas from the bottom blowing tuyere during the reduction refining period after decarburization when melting high alloy steel using a top-bottom blowing converter or a bottom-blowing converter. This is achieved by the high alloy steel refining method of the present invention, which is characterized by the following.

Structure of the Invention In the present invention, reducing gases such as H2 and CQ are blown into the steel bath through the bottom blowing tuyere during the reductive refining period after the decarburization process carried out in a top-bottom blowing converter or a bottom-blowing converter. The inside of the slag is floated and the slag is passed through the slag at high temperature.

At this time, the following reaction occurs between the slag and the reducing gas.

C'y203+3H2→2Cr+3H20Cr2o3+
3CO→2Cr+3CO2M n O+H2−+ M
rL+H20Mn0+CO-+M+C02 Trapping and desulfurization are performed simultaneously with the recovery of M, but the gas blown in as stirring gas for the steel bath can be effectively used. Note that by using a reducing gas, vaporization desulfurization can also be performed in the form of CO3 or H2S.

Examples will be described below.

Example 1 Using a top-bottom blowing experimental furnace, as shown in Figure 1, burnt lime, kamata stone, and ferrosilicon were introduced from the furnace mouth, and H2 gas was injected from the bottom tuyere to investigate the effect. The operating conditions during the reduction period were as shown in Table 1.

Table 1 Bottom-blown gas flow rate H2 gas 2.5 N value reduction time 6 minutes Burnt lime 30ky/l Dolomite 25kjll
/noF, 5i (75chi) 15kp/, <Hataruishi 5.Oki/, that is, the molten steel components are analyzed before and after reduction smelting after decarburization, and the material balance before and after reduction smelting that also serves as desulfurization is determined by H2. We investigated the refund situation. An example of the results is shown in FIG. It is thought that about 10% of the H2 gas blown into the furnace contributed to the reduction of chromium. The average is 12.5% (r
The utilization efficiency was L=22). Moreover, the desulfurization situation at this time is shown in FIG. Compared to the previous case where the entire amount of 7erosilicon was used to reduce chromium, the %S after reduction was
is 0.001% lower on average.

From this, it is considered that a part of S in the molten steel was reduced by H2 gas and desulfurized.

Table 2 shows the changes in units of various conditions when the natural properties are used in operation.
g/t Base -1・3kr Nm'/
13 ・O H2N, m'/l-3・O Cr yield base ±0 Cost index 100 98・O・From Table 2, effects such as reduction in FtSi and reduction in burnt lime for basicity adjustment are recognized. It was found that costs could be reduced by 2%.

Example 2 Next, in 5, high manganese molten steel was heated using a top-bottom blowing experimental furnace.
Restored with gas. The operating conditions are shown in Table 3, and the changes in components before and after reduction are shown in Table 4.

Table 3 Reduction time 6 minutes CO gas flow rate 2.5N/M temperature
165 (FeSi for PC reduction
13.2 Q/ Burnt lime 25.Q
kg/l Dolomite 10ky/l Barrel
5.Okt/<Table 4 When the reduction efficiency by CO gas was calculated in the same way as in the case of H2 gas, the utilization efficiency was about 10%, which was almost the same value as the reduction efficiency of Cr by H2 gas. .

The average for Le = 10 was also 9.5%.

The basic unit for Mn reduction with CO gas is 0.25ky/
N-, and the reduction in the basic unit of ferrosilicon for reduction due to the CO gas chamber of 3.ONm'/l is 0.3 kt/l.

As described in detail of the invention, when refining high-alloy steel using a top-bottom blowing or bottom-blowing converter, reducing gas is blown into the slag through the bottom blowing tuyere during the reduction period after decarburization and refining. The oxidized metal can be reduced and recovered, thereby reducing the SL for reduction.
In addition, the amount of quicklime added can be reduced, and manufacturing costs can be reduced.

[Brief explanation of drawings]

Figure 1 is a reduction operation flow diagram of the present invention, Figure 2 is a diagram showing the balance of reducing substances after reduction, and Figure 3 is a comparison of the method of the present invention and the conventional method regarding %S after reduction. It is a line diagram. town

Claims (1)

[Claims] A high alloy steel characterized in that when high alloy steel is melted using a top-bottom blowing converter or a bottom-blowing converter, a reducing gas is blown from the bottom blowing tuyere during the reduction refining period after decarburization. Refining method.