JP2000239730A - METHOD FOR MELTING Ag-CONTAINING STEEL - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a melting method of an Ag-containing steel having drastically higher Ag additional yield than the conventional method. SOLUTION: In the melting method of the Ag-containing steel by adding Ag particles into the molten steel held in a refining apparatus provided with a gas blowing stirring function and stirring the molten steel, the addition of the Ag particles is intermittently executed at many times and the addition at one time is executed by satisfying the following conditions: the stirring power density (ε): >=30 (W/t), the stirring time: >=0.34 (sec/t) and charging quantity: <=0.1 (kg/t). Wherein, ε=0.0285.Q.(T/W).log[1+(Z/148.(760/P)]. In the equation. W: ton (molten steel), Q: blowing gas flowing rate (normal liter/min), T: molten steel temp. (absolute temp.), Z: the steel bath depth at the gas blowing position (cm) and P: atmospheric pressure (torr).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for adding Ag to molten steel, and more particularly to a technique for adding Ag to molten steel at a high yield in the production of Ag-containing steel.

[0002]

2. Description of the Related Art Recently, there has been a tendency to be concerned about the effects of contamination, bad smell, slime, etc. due to the propagation of various bacteria on human bodies and animals. It was started. In particular, materials that are resistant to various bacteria are preferred for kitchens, toilet plumbing supplies, medical equipment, and the like that require cleanliness. Therefore, a technique of applying a paint or resin containing an antimicrobial agent to the surface of a steel sheet (Japanese Patent Application Laid-Open Nos. 5-228202 and
Stainless steel sheets containing Cu or Ag have been developed and put to practical use in order to impart antibacterial properties to steel materials themselves and to steel materials themselves. In particular, Ag-containing stainless steel is a very effective material because it can exhibit an antibacterial effect without impairing glossiness and workability.

By the way, Ag is an element having a large specific gravity and hardly forming a solid solution with Fe.
When solidified, it is dispersed in the matrix as a simple Ag phase precipitate. Therefore, in order to enhance the antibacterial property, it is necessary to disperse as widely and uniformly in the matrix as possible. Further, since it does not form a solid solution with Fe, the addition yield of Ag is remarkably low (usually about 50%). Therefore, it is necessary to increase the addition yield. Among them, the uniform dispersion is described in
No. 259456 proposes to add Ag having a small particle size while stirring molten steel.

However, Japanese Patent Application Laid-Open No. 10-259456 discloses
In the publication, there is only a statement in the claims that "addition of Ag having a small particle size to stirred steel melt". Regarding a specific method for producing Ag-containing steel, there is no description in the text. Is not mentioned. In this case, the produced Ag-containing steel has a low yield and is expensive, and there is room for improvement in the production method.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a method for producing an Ag-containing steel in which the yield of Ag is significantly higher than in the past.

[0006]

Means for Solving the Problems In order to achieve the above object, the inventor has made intensive efforts to improve the yield of Ag addition during smelting, and has embodied the results in the present invention.

That is, the present invention provides a method for producing Ag-containing steel in which Ag particles are added to molten steel held in a refining apparatus having a gas blowing and stirring function, and the molten steel is stirred.
The addition of the Ag particles is performed intermittently many times, and one addition is performed while satisfying the following conditions.
This is a method for producing g-containing steel.

[0008] Stirring power density (ε): 30 (watt / t) or more Stirring time: 0.34 (sec / t) or more Input amount: 0.1 (kg / t) or less Here, ε = 0.0285 · Q ・ (T / W) ・ log
(1+ (Z / 148) · (760 / P)) W: Ton (molten steel) Q: Blowing gas flow rate (normal liter / min) T: Steel bath temperature (absolute temperature) Z: At gas blowing position Steel bath depth (cm) P: Atmospheric pressure (torr) Further, in the present invention, it is preferable that the refining device is a VOD.

In the present invention, Ag is added and dispersed in small amounts while the molten steel is vigorously stirred by a refining apparatus having a gas blowing and stirring function. Will be improved.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below on the basis of the circumstances leading to the invention.

First, the inventor of the present invention has stated that since Ag has a higher specific gravity than steel, has a higher vapor pressure than iron, and does not form a solid solution in molten steel, it is necessary to uniformly add Ag and disperse it in molten steel. It was thought that it was necessary to add a small amount of the molten steel intermittently in large numbers while stirring it vigorously. Then, in order to realize this idea, the following experiments were performed under various conditions with respect to the amount of Ag added at one time, the power for stirring the molten steel at that time, and the stirring time.

Molten steel 1 whose component corresponds to SUS430,
After holding in the VOD apparatus 2 shown in FIG. 2 and blowing oxygen under reduced pressure to perform decarburization treatment, deoxidation treatment was performed with ferrosilicon. The amount of molten steel per process is 17
It was 5 tons. The grain size is about 3 with respect to the molten steel 1 after the treatment.
The Ag particles 3 of 10 mm were divided into 10 times and charged at intervals of 2 minutes, and argon gas 5 was blown from the bottom of the ladle 4 to stir the molten steel 1. The target Ag concentration in the molten steel 1 was the same for each charge and was 0.045%.
% By weight.

At this time, for each charge, the amount of charge per charge, the stirring time at that time, and the stirring power density (ε) were selected from the following values and operated in combination. (1) ε: 10, 20, 30, 40 (W / t) (2) Stirring time: 0.20, 0.30, 0.35, 0.40 (sec / t) (3) Charge per time Amount: 0.02, 0.05, 0.10, 0.15 (kg / t) The results are collectively shown in Table 1. From Table 1, the stirring power density per time is 30 watts / ton or more, the stirring time is 0.34 sec / t or more, and the input amount is 0.1 kg / ton.
It can be seen that the addition yield of Ag is always 85% or more when the addition is performed while satisfying all the conditions of tons or less. Then, the inventor adopted this condition in the present invention. FIG. 1 shows an example in which a specific smelting method according to the present invention is performed five times with a target Ag concentration of 0.025% by weight.
Will be shown below.

[0014]

[Table 1]

[0015] In the present invention, the number of times the Ag particles are charged depends on the target Ag concentration of the molten steel and differs depending on the type of steel to be smelted. The smelting equipment used is VOD
Not limited to the apparatus 2, any RH degassing apparatus having a decompression function, an AOD furnace without a decompression function, or the like may be used as long as the apparatus has a bottom-blowing gas function. In addition, although the Ag-containing steel to which the present invention is applied is mostly stainless steel, it is needless to say that the invention is not limited to this.

[0016]

EXAMPLE A stainless steel molten steel containing 0.0070% by weight of C, 0.30% by weight of Si, 0.25% by weight of Mn, and 19% by weight of Cr was charged into the VOD apparatus shown in FIG. ,
Antibacterial stainless steel was melted. At this time, the target Ag concentration was set to 0.04% by weight, and the amount per injection was set to 0.05 kg / t and the stirring time was set to 0.37 sec / according to the present invention.
At t, the stirring power density was 35 watt / t, and 10 intermittent Ag injections were performed.

On the other hand, molten steel 1 having the same composition is
And an antibacterial stainless steel having the same target Ag concentration was melted by a conventional melting method. That is, a predetermined amount of Ag is continuously supplied, and the stirring power density 20 watts is adjusted accordingly.
Stirring was performed at t / t. The Ag particles used had a particle size of 3 mm.

As a result, according to the present invention, the addition yield of Ag was 88%, but according to the conventional method, it was only 52%. In addition, these molten steels were subjected to continuous casting and rolling steps to obtain antibacterial stainless steel sheets, and were subjected to a known antibacterial test. As a result, the steel sheet smelted by the method according to the present invention has a sterilization rate of 60% as compared with the steel sheet smelted by the conventional method.
It turned out to be large.

[0019]

As described above, according to the present invention, Ag
Ag is always produced at a yield of 85% or more when smelting steel containing steel.
Can be added.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a method for melting Ag-containing steel according to the present invention.

FIG. 2 is a longitudinal sectional view showing a normal VOD device.

[Explanation of symbols]

 Reference Signs List 1 molten steel (stainless steel molten steel) 2 VOD device 3 Ag particles 4 ladle 5 argon gas 6 lance for oxygen blowing 7 charging device

Claims (2)

[Claims] 1. A method for producing Ag-containing steel by adding Ag particles to molten steel held in a refining apparatus having a gas injection stirring function and stirring the molten steel, wherein the Ag particles are added intermittently. A is characterized in that a single addition is performed under the following conditions:
Melting method of g-containing steel. Stirring power density (ε): 30 (W / t) or more Stirring time: 0.34 (sec / t) or more Input amount: 0.1 (kg / t) or less Here, ε = 0.0285 · Q · ( T / W) · log
(1+ (Z / 148) · (760 / P)) W: Ton (molten steel) Q: Blowing gas flow rate (normal liter / min) T: Steel bath temperature (absolute temperature) Z: Steel at gas blowing position Bath depth (cm) P: Atmospheric pressure (torr) 2. The method according to claim 1, wherein the refining device is a VOD.