JP2002053351A - Pollution-free stainless steel slag and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the elution of hexavalent Cr and F from stainless steel reduction slag and to allow resource recovery thereof to subbase course materials, civil engineering materials or cement raw materials, or the like. SOLUTION: (1) The slag component is regulated to be made into Claim 1 or Claim 2. (2) The slag composition is controlled by a method of regulating the amount of a deoxidizing agent and a slag forming agent to be fed in a refining reduction period or a method for feeding a material containing insufficient components after refining reduction. (3) Brick waste materials which are industrial wastes are effectively utilized as flux materials for regulating the slag composition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for suppressing the dissolution of hexavalent Cr, F and B from slag (hereinafter referred to simply as "stainless slag") generated during refining of stainless steel, thereby rendering it harmless. And a detoxifying stainless slag usable as a resource such as a cement material or the like, and a method for obtaining such a stainless slag.

According to the present invention, the amount of industrial waste generated can be reduced by utilizing the refractory waste disposed of as industrial waste as a slag-making agent for adjusting the slag composition.

[0003]

2. Description of the Related Art From the viewpoint of protection of the global environment and the problem of depletion of industrial waste dumping sites, it is important to reduce the amount of industrial waste generated and to make it harmless and recycle. Stainless slag is also positioned as one of the industrial wastes and has similar problems.

[0004] Stainless slag, ie, stainless reduced slag, is inevitably generated when reducing or desulfurizing oxides generated in a raw material melting or refining process. The generated stainless slag has the following problems in detoxification and recycling due to its own characteristics. Powdering of slag: Stainless slag contains 2CaO ・ SiO ₂ (hereinafter, C ₂ S), and this C ₂ S is α ′ → γ during cooling.
It is well known that the phase transforms into a mold and powders due to the volume change at this time.

When slag is used as a roadbed material or civil engineering material, it is necessary to maintain strength, and there is a problem that powdered slag is difficult to recycle. In addition, there is a problem in terms of deterioration of surroundings and working environment and difficulty in processing. Hexavalent Cr elution: Stainless slag contains Cr ₂ O ₃ , some of which may be trace amounts depending on the conditions of waste and cooling.
Slag, which is one of the factors of concern in recycling stainless slag. F elution: Stainless slag contains F since fluorite (CaF ₂ ) is used as a melting point depressant during refining. Since F has an adverse effect on ecosystems, it is necessary to control elution from slag. B elution: Normal stainless slag contains only a trace amount of B ₂ O ₃ , but when a boric acid compound is added for the purpose of solidifying the slag, or when B-containing stainless steel is melted, a high concentration of B ₂ O ₃ is obtained. O ₃ is present in the slag. B also has an adverse effect on ecosystems, so it is necessary to suppress elution from slag.

To cope with these problems, for example, regarding solidification of stainless slag, Japanese Patent Application Laid-Open No. 62-87442 proposes a method of adding a boric acid compound and a heat-generating substance such as Al and Si. According to this method, slag can be solidified, but the slag contains a large amount of B ₂ O _3, which causes B elution. Further, the relationship between B ₂ O ₃ and B elution is not considered.

Japanese Patent Application Laid-Open No. Hei 8-26791 discloses a method for modifying stainless slag in which Al ash and a silica-based substance are added into a molten slag or a slag pan, and Japanese Patent Application Laid-Open No. 9-316523 discloses an index specified by composition. A method of suppressing slag powdering and suppressing hydration swelling by satisfying is proposed.

[0008] These methods are aimed at obtaining the strength of slag or stabilizing the quality as earth wood and roadbed material, and have taken into account the suppression of elution of hexavalent Cr, F and B. However, the technology is not sufficient for detoxifying stainless slag.

To prevent the dissolution of hexavalent Cr, for example, in JP-A-6-171993, powdering of slag is suppressed by adding Al ash and Mg-based substances to slag containing Cr oxide in a molten state. He also proposed a method to suppress the elution of hexavalent Cr.

However, even in this method, no consideration is given to the suppression of elution of B and F, and it cannot be said that the stainless slag is rendered harmless. As described above, in the conventional slag solidification technology, there is no example in which a sufficient quantitative study has been made on the relationship between the suppression of the dissolution of hexavalent Cr, F and B and the slag composition.

Further, from the viewpoint of the protection of human health and the preservation of the living environment, the Environment Agency has determined that the landfill standards are as follows: hexavalent chromium elution amount ≤ 0.5 mg / l, F elution amount ≤ 8.0 mg / l, B elution amount ≤ 10.0. mg / l, for soil environmental standards, hexavalent chromium elution amount ≤ 0.05 mg / l, F elution amount ≤ 0.8 mg / l, B elution amount ≤ 1.0 mg / l
It has been proposed that the value should be l, and it is very important to obtain knowledge on the relationship between the elution amount of the above items and the slag composition components.

On the other hand, as a method for controlling the slag composition, JP-A-11-217246 discloses a method for controlling the composition of reduced slag by adding a heating agent and components necessary for solidifying slag to a container in which molten slag is collected. There has been proposed a method for preventing such a phenomenon. However, this method has a problem that the number of processes for slag treatment increases and the cost such as equipment cost increases.

[0013] In Japanese Patent Application Laid-Open No. Hei 8-2681,
Although a method of adding Al ash and a silica-based substance has been proposed, there is a problem that sufficient mixing cannot be obtained by addition to a steel receiving pan.

The slag composition control method as described above is a process that causes an increase in man-hours. As a slag composition control method in a steady operation, a slag treatment method capable of obtaining a uniform slag composition without increasing the process is desired.

As a method for modifying stainless slag, Japanese Patent Application Laid-Open No. 9-165238 proposes a method in which waste concrete is poured into stainless slag and solidified. It is useful to use such waste materials as a slag modifier, and it is important to effectively utilize not only concrete waste materials but also other industrial waste materials in order to reduce the amount of industrial waste generated. It is also important.

[0016]

SUMMARY OF THE INVENTION An object of the present invention is to suppress the elution of hexavalent Cr, F, and B from stainless slag to render it harmless, and to use it as a resource for earth wood, roadbed material, cement material, and the like. It is to provide a simple stainless slag and a refining method for obtaining it.

Further, it is another object of the present invention to develop a technique for reducing the amount of industrial waste generated by using a refractory waste material disposed of as industrial waste as a solvent.

[0018]

According to the present invention, the amount of hexavalent Cr eluted from stainless slag is ≤0.5 mg / l, and the amount of F eluted is ≤0.5 mg / l.
The following slag composition (% by mass) is proposed in order to suppress the amount of B dissolved to 8 mg / l and the amount of B eluted to ≦ 10 mg / l.

(% CaO) / (% SiO ₂ ) ≧ 1.5 and 15.83 (% CaO) /
(SiO ₂ ) −19.30 ≦ (% Al ₂ O ₃ ) ≦ 30% or 14% ≦ (% Al
₂ O ₃ ) ≦ 30%, (% Cr ₂ O ₃ ) ≦ 20%, (% B
₂ O ₃ ) ≦ 0.6%, (% F) ≦ 5%, (% MgO) / (% CaO) = 0.05 ~
0.40, (% T.Fe) + (% Cr ₂ O ₃ ) + (% MnO) ≦ 5%.

In another aspect of the present invention, the amount of hexavalent Cr eluted from stainless slag is ≤0.05 mg /
In order to suppress l, F elution amount ≤ 0.8 mg / l and B elution amount ≤ 1.0 mg / l, the stainless slag composition is specified as follows in terms of mass%.

(% CaO) / (% SiO ₂ ) ≧ 1.5 and 15.83 (% CaO) /
(SiO ₂ ) −19.30 ≦ (% Al ₂ O ₃ ) ≦ 30% or 14% ≦ (% Al
₂ O ₃ ) ≦ 30%, (% Cr ₂ O ₃ ) ≦ 10%, (% B ₂ O ₃ )
≤0.1%, (% F) ≤2.0%, (% MgO) / (% CaO) = 0.05-0.4
0, (% T.Fe) + (% Cr ₂ O ₃ ) + (% MnO) ≦ 5%.

The method for preparing stainless slag according to the present invention is characterized in that one or two of Al and Si are used as deoxidizing agents and Al ₂ O ₃ , CaO, SiO ₂ and MgO are used as slag-making agents in the slag in the refining and refining period. It may be carried out by a method of charging two or more components, or a method of charging a slag after smelting reduction or at a temperature adjustment time with a substance containing a component less than the slag composition described above.

Also, the amount of industrial waste generated may be reduced by utilizing refractory waste as a medium solvent of the slag composition.

[0024]

Next, the details of the embodiment of the present invention will be described. In this specification, "%" that defines the slag composition is "mass%" unless otherwise specified.

The present inventor has found, from many experimental results, a slag composition which solidifies stainless slag, suppresses elution of hexavalent Cr, F, and B, renders it harmless, and can be recycled.

First, the reasons for limiting the slag composition and the effects of the slag composition will be described below. The following data is obtained when the slag composition is adjusted by adding various additives to the slag during the refining and refining of stainless steel.

FIGS. 1, 2 and 3 show the relationship between the slag powdering ratio and the amounts of hexavalent Cr, F and B eluted, respectively. As shown in the figures, the elution amounts of hexavalent Cr, F and B show a decreasing tendency with a decrease in the slag powdering rate, and particularly, the powdering rate is 10%.
% Or less, the elution amounts of hexavalent Cr, F and B are rapidly suppressed. This suppression of the elution amount is presumed to be due to a decrease in the slag surface area due to a decrease in the slag powdering rate.

The elution amount of each component is determined by the Environment Agency Notification No. 13
We investigated according to the number. One week after the slag is generated, the slag is crushed and passed through a 4 mesh sieve,
It was the ratio of the weight passed through the sieve to the total weight.

In the refining and refining of stainless steel, the basicity is generally controlled so that CaO / SiO ₂ in the slag becomes ≧ 1.5 from the viewpoint of reducing the total oxygen concentration of the molten steel and ensuring the cleanliness of the molten steel. However, in the region where CaO / SiO ₂ is ≧ 1.5, 2CaO
· SiO ₂ is produced slag is powdered.

FIG. 4 shows a ternary phase diagram of CaO—SiO ₂ —Al ₂ O ₃ . From the ternary phase diagram of FIG. 4, the region where powdered 2CaO.SiO ₂ is generated can be easily predicted. However, the slag in the actual operation contains other components of the ternary system or more, and does not always coincide with the region in the figure.

Therefore, the inventor has investigated various slag compositions in which CaO / SiO ₂ is in the range of ≧ 1.5 and the slag applied in actual operation is not powdered. FIG. 5 shows slag CaO / SiO ₂ , in slag (% Al ₂ O
The relationship between ₃ ) and the slag dusting ratio is shown.

In the figure, the charge having a powdering rate of ≦ 10% is solidified,
Charges with a powdering rate ≧ 10% were classified as powdered. As shown in the figure, the slag content (% Al ₂ O ₃ ) is ≧ 15.38 (CaO / SiO ₂ ) −1
When 9.30 or ≧ 14%, slag powdering can be suppressed.

FIG. 6 shows the relationship between the Al ₂ O ₃ concentration in the slag and the erosion rate of the refractory. As can be seen from this, when the Al ₂ O ₃ concentration in the slag exceeds 30%, the erosion rate of the refractory increases rapidly. This is presumed to be due to the decrease in the melting point of the slag due to the increase in the slag (% Al ₂ O ₃ ).

The erosion rate was calculated from the erosion amount of the smelted refractory under each operating condition. Therefore, in the slag (% Al ₂ O ₃ )
The concentration was defined as (% Al ₂ O ₃ ) ≧ 15.38 (CaO / SiO ₂ ) −19.3 to 30% or 14 to 30%.

The reason why the concentration of Cr ₂ O ₃ in the slag is set to 20% or less, preferably 10% or less is that the slag is stabilized when the CaO / SiO ₂ ratio and the Al ₂ O ₃ concentration are within the above ranges. As shown in FIG. 7, when the content is 20% or less, the amount of hexavalent Cr eluted is 0.5 mg / l or less.
% Or less can be suppressed to 0.05 mg / l or less. As the Cr ₂ O ₃ concentration in the slag is lower, the elution of hexavalent Cr is suppressed.

The B ₂ O ₃ concentration in the slag is set to 0.6% or less, preferably 0.1% or less when the slag is stabilized when the CaO / SiO ₂ ratio and the Al ₂ O ₃ concentration are within the above ranges. As shown in the figure, the elution amount of B can be suppressed to 10 mg / l or less at ≤0.6% and 1 mg / l or less at ≤0.1%. The lower the B ₂ O ₃ concentration in the slag, the more the amount of B eluted is suppressed.

The F concentration in the slag is 5% or less, preferably
When the CaO / SiO ₂ ratio and the Al ₂ O ₃ concentration are stabilized within the above-mentioned ranges, the slag is stabilized at 2% or less, as shown in FIG. ≦ 2% can be suppressed to 0.8 mg / l or less. The lower the F concentration in the slag, the more the F elution amount is suppressed.

FIG. 10 shows the relationship between the MgO / CaO ratio and the erosion rate. If the MgO / CaO ratio is less than 0.05, the life of the refractory decreases due to infiltration and erosion of the slag into the refractory. On the other hand, 0.40
As shown in FIG. 11, it was found that when the temperature exceeds the limit, the yield decreases due to an increase in the amount of heat for melting and a decrease in the fluidity of the slag, thereby increasing the operation load. Therefore, the MgO / CaO ratio is 0.05-
It was set to 0.40.

The reason why (% T.Fe) + (% Cr ₂ O ₃ ) + (% MnO) is ≦ 5% is that a decrease in yield can be suppressed. The detoxification treatment of stainless slag of the present invention is applied to slag generated in AOD, VOD, top and bottom blown converter, LF, and bubbling treatment. Refining with AOD and LF includes treatment under reduced pressure.

Conventionally, as a method for adjusting the slag composition, installation of slag processing equipment, insertion of a slag modifier with insufficient stirring, and the like have been employed. One or two of Al and Si, Al as a slag-making agent
_Two methods for introducing two or more of ₂ O ₃ , CaO, SiO ₂ and MgO, and two methods for introducing a substance containing a deficient component after reduction refining or at the time of temperature adjustment have been found.

Both methods can detoxify slag without increasing the process for controlling slag composition, and are effective in reducing equipment costs, efficiency, and operating costs.
The refining method using Al or Al and Si as a deoxidizing agent is effective for steel types that require low oxygen in the molten steel and a reduced amount of inclusions, while maintaining high cleanliness of the steel and detoxifying the slag. A possible way.

The refining method using Si as the deoxidizing material in the above method is effective for melting a pressing material or the like in which a product trouble due to Al ₂ O ₃ inclusions is concerned in use, and Al is used in a trace amount. We can supply molten steel.

As methods for controlling the composition of slag by the above methods, methods for predicting from oxygen efficiency, methods for predicting from changes in molten steel components during refining, methods for predicting from exhaust gas flow rates and concentrations during refining, conventional operating conditions and A method of predicting from the slag composition and the like can be given.

In another method, more accurate slag composition
And has the advantage that temperature control is possible. Input
SiO_TwoSources include CaO sources such as silica sand and river sand.
Lime, dolomite, etc.
ー, natural magnesia, Al_TwoO _ThreeMetal Al, Al ash as source
And the like.

On the other hand, refractory waste materials include MgO, Al ₂ O ₃ , SiO ₂
And a component such as CaO 2, and is suitable as a solvent for adjusting the slag composition, that is, as a slag-making agent. Al ₂ O ₃ refractories, Al ₂ O ₃ -MgO refractories, CaO-MgO refractories, SiO ₂ refractories, MgO-C refractories, MgO refractories Objects and the like. These refractories are crushed after being separated and collected, and applied as a slag-making agent.

FIG. 12 shows the relationship between the particle size after crushing and the rate of slag formation. The slagging rate tends to decrease as the particle size increases, and from the viewpoint of slagging and effective use of refractory waste material, the slagging rate is preferably ≦ 50 mm exceeding 80%. In addition, slagification rate,
It was calculated as the ratio of the slag component before charging and the component after charging to the charging component.

Further, since the brick waste is treated as industrial waste, it is also effective in reducing the amount of industrial waste generated in the total slag and brick waste by utilizing it as a slag-making agent for adjusting the slag composition. .

[0048]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to embodiments.

[0049]

Example 1 Austenitic stainless steel having a charge of 80 t was melted using AOD. The slag composition was controlled by adjusting the amounts of Al and Si as reducing agents and MgO and CaO as slag-making agents based on changes in molten steel components during refining.

The slag after the AOD treatment was collected, and the composition of each slag, the elution amounts of hexavalent Cr, F and B, and the powdering ratio were examined. In addition, the measurement of the amount of erosion of the furnace body was operated under the same conditions for 10 charges,
The erosion rate was calculated from the amount of erosion of the tuyere.

Table 1 shows the AOD slag compositions of the invention examples and the comparative examples, and Table 2 shows the results of the investigation of the elution amount, powdering rate and erosion rate.
Shown in Inventive Example 1, as compared with Comparative Example 6, (% Al ₂ O ₃ ) ≧
In the case of Invention Example 1 where 15.38 (CaO / SiO ₂ ) −19.30, the powdering ratio was 0%, whereas (% Al ₂ O ₃ ) ≧ 15.38 (CaO / Si
In Comparative Example 6 where O ₂ ) is −19.30, the powdering ratio is 100%.

Further, in contrast to Invention Example 2, Comparative Example 7
Invention Example 2 satisfying (% Al ₂ O ₃ ) ≧ 14% has a powdering rate of 0%, whereas (% Al ₂ O ₃ ) ≧ 15.38 (CaO / SiO ₂ ) −19.30 and (% Al ₂ O ₃ ) ₃ ) In Comparative Example 7, which did not satisfy both conditions of ≧ 14%, the powdering ratio was 60%.

In contrast to Inventive Example 3, as in Comparative Example 8, (% Al
₂ O ₃₎ exceeds ≧ 30% Comparative Example 8 tuyere erosion rate was found to be significantly worse. Further, Comparative Example 9 was compared to Invention Example 4.
As shown in the figure, Comparative Example 9 in which (% Cr ₂ O ₃ ) ≧ 20%
While the elution amount was ≧ 0.5 mg / l, in Invention Example 4 where (% Cr ₂ O ₃ ) ≦ 20%, the elution amount of hexavalent Cr could be suppressed to ≦ 0.5 mg / l.

Further, in Invention Example 5, (% Cr ₂ O ₃ ) was
%, The elution amount of hexavalent Cr could be suppressed to ≦ 0.05 mg / l. In addition, it was clarified that the slag composition can be controlled by adjusting the input amounts of Al and Si as reducing agents and MgO and CaO as slag-making agents according to this example.

[0055]

Example 2 Using a VOD, 75 tons of each charge of ferritic stainless steel was melted. The slag composition is based on Si as a reducing agent and Al ₂ O ₃ , MgO and CaO as slag-making agents based on oxygen efficiency.
Was adjusted and controlled. Incidentally, applying the Al ₂ O ₃ -MgO brick waste crushing to ≦ 25 mm as Al ₂ O ₃ source. Collect the slag after AOD treatment,
Cr, F and B elution amounts and powdering ratio were investigated.

Further, the measurement of the amount of erosion of the ladle was carried out for 10 charges under the same conditions, and the erosion rate was calculated from the remaining thickness of the slag line portion. Table 3 shows the composition of the VOD slag of this example, and Table 4 shows the results of the investigation of the elution amount, powdering rate and erosion rate.

For Examples Nos. 1 and 2, as shown in Nos. 7 and 8, the elution amount of B was (% B ₂ O ₃ ) ≦ 0.6% and ≦ 10.0 mg / l, (% B
_{At 2} O ₃ ) ≦ 0.1%, it could be controlled to ≦ 1.0 mg / l. For Nos. 3 and 4, the F elution amount was (%
F) ≤8.0 mg / l at ≤5.0%, 0.8 mg / l at (% F) ≤2.0%
l could be controlled.

In contrast to Nos. 5 and 6, as shown in Nos. 11 and 12, when the erosion rate of the refractory was (% MgO) / (% CaO) ≦ 0.05, the erosion rate increased to 220. On the other hand, when (% MgO) / (% CaO) ≧ 0.40, an increase in the lower oxide concentration and an increase in operation load such as heat compensation were caused.

Further, according to the present embodiment, it is possible to control the slag composition by adjusting the input amounts of Si as a reducing agent and Al ₂ O ₃ , MgO and CaO as slag-making agents. It has been clarified that brick waste can be used as a solvent.

[0060]

Example 3 At the bubbling station, the temperature and composition of stainless steel for each charge of 80 t were finely adjusted. For the slag composition, components that are insufficient for the material balance after refining were introduced.

Table 5 shows the results of slag composition analysis before and after bubbling. Since Al ₂ O ₃ component and MgO component were insufficient, waste Al ₂ O ₃ -MgO brick and magnesia clinker were charged. The slag composition after the bubbling treatment was almost as intended, and as shown in Table 6, each elution amount and powdering ratio could be reduced, and the slag was rendered harmless.

According to this example, it was clarified that the control of the slag composition from the balance of the material after refining and the use of the waste bricks as a slag-making agent for adjusting the slag composition were possible.

FIG. 13 shows the amount of industrial waste generated when the brick waste material is used as a slag-making agent, as compared with that during normal operation.
As can be seen, the use of brick waste as a slag-making agent has reduced the total amount of industrial waste generated by 30%.

[0064]

[Table 1]

[0065]

[Table 2]

[0066]

[Table 3]

[0067]

[Table 4]

[0068]

[Table 5]

[0069]

[Table 6]

[0070]

Industrial Applicability According to the present invention, hexavalent Cr, F and B can be prevented from being eluted and solidified from stainless slag, the stainless slag can be made harmless, and resources can be recycled into earth wood, roadbed material and cement material. Is now available.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between a powdering rate and an elution amount of hexavalent Cr.

FIG. 2 is a graph showing a relationship between a powdering rate and an F elution amount.

FIG. 3 is a graph showing a relationship between a powdering rate and a B elution amount.

FIG. 4 is a diagram of a ternary phase diagram of CaO—SiO ₂ —Al ₂ O ₃ .
4 is a graph showing CaO and SiO ₂ generation regions.

FIG. 5 is a graph showing the relationship between (% CaO) / (% SiO ₂ ), (% Al ₂ O ₃ ) and the powdering rate.

FIG. 6 is a graph showing the relationship between (% Al ₂ O ₃ ) and the erosion rate.

FIG. 7 is a graph showing the relationship between (% Cr ₂ O ₃ ) and the amount of hexavalent Cr eluted.

FIG. 8 is a graph showing the relationship between (% B ₂ O ₃ ) and the amount of B eluted.

FIG. 9 is a graph showing the relationship between (% F) and the F elution amount.

FIG. 10 is a graph showing the relationship between (% MgO) / (% CaO) and the erosion rate.

FIG. 11 is a graph showing the relationship between (% MgO) / (% CaO) and yield.

FIG. 12 is a graph showing the relationship between the crushed particle size of the refractory waste material and the slag ratio.

FIG. 13 is a graph showing a comparison of the amount of industrial waste generated.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C21C 5/54 B09B 3/00 ZAB 7/00 304C F term (Reference) 4D004 AA16 BA02 CA34 CA41 CC11 DA03 DA10 4G012 JB02 JC06 JL02 JM04 4K002 AA03 AA04 AE01 AE06 4K013 AA02 BA00 CA09 CF01 EA03 EA04 EA05 4K014 CA04 CB05 CC07 CE01

Claims (5)

[Claims] The slag composition generated during refining of stainless steel is (% CaO) / (% SiO ₂ ) ≧ 1.5 and 1% by mass.
5.83 (% CaO) / (SiO ₂ ) −19.30 ≦ (% Al ₂ O ₃ ) ≦ 30%, or 14% ≦ (% Al ₂ O ₃ ) ≦ 30%, and (% Cr ₂ O ₃₎ ) ≦ 20%, (% B ₂ O ₃ ) ≦ 0.60%, (% F) ≦ 5.0%, (% MgO) / (% CaO) = 0.05 to 0.40, (% T.Fe) + (% Cr ₂ O ₃ ) + (% MnO) ≦ 5%, and the amount of hexavalent Cr eluted from the slag is 0.5 mg / l or less,
A detoxified stainless steel slag having an F elution amount of 8.0 mg / l or less and a B elution amount of 10 mg / l or less. 2. The slag composition generated during refining of stainless steel is (% CaO) / (% SiO ₂ ) ≧ 1.5 and 1% by mass.
5.83 (% CaO) / (SiO ₂ ) −19.30 ≦ (% Al ₂ O ₃ ) ≦ 30% or 14% ≦ (% Al ₂ O ₃ ) ≦ 30%, and further (% Cr ₂ O ₃ ) ≦ 10%, (% B ₂ O ₃ ) ≦ 0.10%, (% F) ≦ 2.0%, (% MgO) / (% CaO) = 0.05 to 0.40, (% T.Fe) + (% Cr ₂ O ₃ ) + (% MnO) ≦ 5%, and the amount of hexavalent Cr eluted from the slag is 0.05 mg / l or less,
A detoxified stainless slag having an F elution amount of 0.8 mg / l or less and a B elution amount of 1.0 mg / l or less. 3. The slag in the refining and refining stage of stainless steel,
By adding one or two of Al and Si as a deoxidizing agent and two or more of Al ₂ O ₃ , CaO, SiO ₂ and MgO components as a slag-making agent, A method for producing detoxified stainless slag, which has a specified slag composition. 4. A harmless slag composition as defined in claim 1 or 2, wherein a material containing a deficient component is introduced into the slag after the refining and refining of the stainless steel or at the time of temperature adjustment. Of manufacturing stainless steel slag. 5. A method for detoxifying stainless slag, wherein a refractory waste material is used as a slag-making agent.