JP2001271113A - Converter-refining method for by-producing steel manufacturing slag having low free lime content - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an effective slag upgrading method in which the lowering of F-CaO as the main cause of expansion-collapsibility is extremely, quickly and efficiently be performed and the conventional aging treatment can be omitted or saved when the by-produced steel manufacturing slag is reused. SOLUTION: In a converter-refining method performing desiliconization and dephosphorization as a pre-treatment of molten iron by utilizing the converter, the following molten iron is charged in the state of leaving the slag after completing the dephosphorized treatment in the furnace without removing the slag after tapping the steel. Then, oxygen is supplied and the desiliconizing treatment is performed, and after desiliconizing, the oxygen-blowing is once interrupted and an intermediate slag-removing process for discharging the slag is performed, and the dephosphorizing refining is successively performed to by-produce the steel manufacturing slag having low free lime content.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a slag having a high basicity (% CaO /% SiO ₂ ) and free lime (hereinafter referred to as “F”).
-CaO ". The present invention relates to a method for reforming steelmaking slag containing a large amount of slag.

[0002]

2. Description of the Related Art Steel slag is roughly divided into blast furnace slag and steelmaking slag. Among these, steelmaking slag is pre-processed hot metal slag which removes some unnecessary components before refining pig iron in a converter, and pig iron. The main components are converter slag generated during refining in a converter and ladle slag after continuous casting. Steelmaking slag has been used in full-fledged technology development and spread promotion activities since the 1975's, and its recent main uses are for civil engineering and roads. However, steelmaking slag has a high basicity, and F
-Because it contains a large amount of CaO and has expansive disintegration properties, it is essential to solve the expansive disintegration properties for reuse. At present, aging treatment (reaction with air and water after crushing) That is, a technique for suppressing expansion to a point where there is no problem in practical use has been taken. An aging method that further reduces the expansion coefficient of slag using steam has been developed. In addition to these conventional techniques, for example, in Japanese Patent Application Laid-Open No. H11-71160, `` Stones for submersion in the sea and a method for producing the same '', CaCO ₃ generated by a carbonation reaction using steel slag as a material is solidified as a binder, A method for producing a stone material by modifying a slag such as agglomeration is disclosed.

[0003]

As described above, when steelmaking slag is reused as a by-product, it is necessary to solve the expansive collapse property.
Reduction of CaO is effective. However, the current air aging method has problems that the reforming level of the slag in the yard tends to be non-uniform due to temperature fluctuations, uneven permeation at the time of watering, etc., furthermore, the aging processing time is long, and a large yard is required. There is. Also, the steam aging method,
There are many issues from the viewpoints of steam equipment cost, running cost, and processing capacity, and further, there is no description in the above-mentioned patent gazette of a method for reducing F-CaO, and development of a new slag reforming technology to replace them Is desired.

[0004]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above circumstances, and is capable of extremely quickly and efficiently reducing F-CaO, which is a main cause of expansion and collapse, to achieve a conventional aging treatment. An object of the present invention is to provide an effective slag reforming method that can be moderated or omitted. The gist of the present invention is as follows. (1) In a converter refining method for removing Si and P as molten iron pretreatment using a converter, the slag after the completion of the removal of P is left in the furnace without discharging after discharge from the hot water. Hot metal is charged, oxygen is supplied, and de-Si treatment is performed.
(b) A converter refining method for producing by-produced steel slag having a low free lime content, which comprises interrupting the blowing and temporarily discharging an intermediate slag after discharging the slag, and subsequently performing de-P refining. (2) The converter refining method according to the above (1), wherein the slag remaining in the furnace after the de-P treatment and the slag containing free lime generated in another step are charged into the furnace before the de-Si treatment. (3) In a converter refining method that uses a converter to remove Si and P as molten iron pretreatment, slag containing free lime generated and recovered in its own process or another process prior to blowing is loaded into the furnace. Injection and supply of oxygen to perform a de-Si treatment, and after the de-Si, a blowing process is temporarily interrupted to provide an intermediate waste discharging step of discharging the reformed slag, and then the de-P refining is continuously performed. Converter refining method that produces steelmaking slag with low lime content.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION In a converter refining process, a large amount of lime is used as an auxiliary material, and the slag generated usually has a basicity of 1.1 to 4.0 for de-P refining and 2.0 to 4 for de-C refining. It is about 0.0, and fluorite or the like is used to efficiently turn such high basicity slag into slag. However, even if fluorite is used, it is difficult to completely form lime, and lime that has not been lime becomes free lime in the recovered slag. Also,
Even in slag slag, particularly when the basicity is high, free lime crystallizes as primary crystals. Therefore, the by-product slag usually contains about 1 to 4% of free lime (F-CaO). Slag containing free lime reacts with the atmosphere and expands in volume, and thus cannot be used as a civil engineering material as it is. Therefore, when such slag is reused outside the system for civil engineering and road use, aging processing is usually performed.

The present inventors conducted research and development to reduce the amount of F-CaO in slag generated in a hot metal pretreatment process for removing Si and P using a converter. The present inventors used a 300 TON converter on a full scale,
A study was conducted in the process of charging about 290 TON of hot metal.

In the conventional method, as shown in FIG. 3, after the molten iron is charged into the converter, quick lime and iron ore are added, and oxygen is supplied to the converter to remove oxygen and remove Si. After the molten metal is poured into a ladle, the slag is discharged to a slag pan after de-P treatment after the molten metal is poured. The basicity of this slag is 1.8 on average, F
-CaO averaged 2.2%. This slag cannot be used as a civil engineering material because it has expandability and collapse properties as it is.

[0008] The inventors of the present invention perform an intermediate waste after the de-Si treatment, perform a de-P treatment after that, discharge the molten metal in the furnace to the ladle after the treatment is completed, and after the tapping, remove the slag after the de-P treatment in the furnace. Remained. The composition of this slag had an average basicity of 1.8 and F-CaO an average of 2.2%, as in the conventional method. In order to further improve the slagification of the slag and reduce the amount of F-CaO, the hot metal of the next heat is charged while the slag remains in the furnace, and oxygen is supplied to remove the Si from the hot metal. An attempt was made to reduce the basicity of the slag with the generated SiO _{2 and to} slag F-CaO in the residual slag. The average composition of the hot metal at the time of charging the converter was [C] = 4.6%, [S]
i] = 0.45%, [Mn] = 0.23%, [P] =
0.095%, [S] = 0.020%. As a result, it was found that at the end of the de-Si treatment of the next heat, F-CaO in the slag was reduced to an average of 0.19%. Since the slag is a mixture with the de-P slag from the previous heat, it contains a large amount of P ₂ O ₅ , and the de-P treatment of the next heat cannot be performed as it is. Therefore, S
After the i-treatment, the blowing is temporarily interrupted, the intermediate waste is discharged by tilting the furnace, and discharged out of the system. The slag discharged out of the system is F-Ca
Since O is low, it does not exhibit expansion collapse property and can be used as it is as a civil engineering material.

Then, the auxiliary material for removing P is recharged into the converter,
Subsequently, the de-P refining is performed, and thereafter, the above-described steps are repeated, whereby only the reformed slag can be discharged out of the system and manufactured.

FIG. 1 shows the processing flow of claims 1 and 2 of the present invention, FIG. 2 shows the processing flow of claim 3 of the present invention, and FIG.
15 shows an i-P removal processing flow.

The present invention is a very effective method for reducing F-CaO. Therefore, for example, slag generated and recovered in another process containing a large amount of F-CaO, such as slag after de-C, is charged into the furnace prior to de-Si blowing, and de-Si blowing is performed. By doing so, slagification can be promoted by the generated SiO ₂ , and F-CaO can be easily reduced.

The reason that the present invention is limited to the converter steelmaking method in which the hot metal pretreatment is performed by using the converter is that the steel removal method using the converter is used.
This is because if the treatment is performed, sufficient stirring power can be obtained, and the P slag removed from the previous heat and the Si slag removed from the next heat are sufficiently mixed to exhibit the slag reforming effect. In addition, in the case of hot metal pretreatment using a converter, the control of the slag composition can be satisfactorily performed, and the return P at the time of slag reforming can also be reliably suppressed.

[0013]

[Example] 300T as a hot metal pre-removal Si and P removal furnace
The present invention was applied by charging 280 to 300 TON of hot metal using an ON converter. Table 1 shows the result of applying the processing flow of the present invention, and Examples 1 to 4 show the processing flow shown in FIG.
Example 5 shows the result of applying the processing flow shown in FIG. Table 2 shows the measurement results of the water immersion expansion coefficient of the slag modified by the practice of the present invention. In Table 1, among the slag compositions, “upper row; residual in the furnace” indicates the residual slag composition in the furnace after the de-P treatment, and “lower row;
3 shows the composition of slag remaining in the furnace after the treatment.

[0014]

[Table 1]

[0015]

[Table 2]

In Examples 1-4, the removal of P from the reforming furnace
The post residual slag is about 35 to 50 kg / t. Example 5 is a result of applying the present invention by leaving only slag generated and recovered in a decarbonization furnace, which is another process, in a furnace before desiliconization without leaving slag after P removal, and applying the present invention; The amount of C residue removed at this time is 25
It is about kg / t. As can be seen from the results in these examples, by applying the present invention, it is possible to lower the F-CaO content of the steelmaking slag containing a large amount of F-CaO, and as shown in Table 2, the expansion stability, which is a problem unique to steelmaking slag. Can be greatly improved without aging, and the standard for application of roadbed materials and concrete (water immersion expansion coefficient ≦ 1.5%) can be easily achieved.

Further, as shown in Example 5, the same effect was confirmed in the case where the C-removed slag was recycled instead of the P-removed slag, and the effect was also confirmed in the case where the method described in claim 2 was carried out. The basicity, F-CaO, and expansion stability of the slag generated in the normal operation of the comparative example shown in FIG.
The results are shown in Tables 1 and 2 with the actual values of residual slag in the furnace.

By the way, as shown in the examples, the slag basicity after the de-Si treatment is about 0.9 to 1.1, By controlling the slag composition so that the Fe content is about 15 to 25%, it is possible to suppress the recovery of P after the removal of Si, and to facilitate the subsequent removal of P. This slag composition control can be easily controlled by the amount of iron ore or the upper blowing oxygen.

[0019]

As described above, according to the present invention, the expansion stability of steelmaking slag, which has been improved by adding measures such as aging, can be obtained very easily in a normal converter refining cycle. In addition, the reforming level can be improved to a level that cannot be achieved by the conventional aging treatment, and this is a very useful invention in terms of effective utilization of steelmaking slag.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a flow of a process for reforming residual slag in a furnace according to the present invention.

FIG. 2 is an explanatory diagram showing a flow of a slag reforming process of another process of the present invention.

FIG. 3 is an explanatory diagram showing a flow of a conventional converter-type de-Si / de-P process.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Masayuki Arai 12, Nakamachi, Muroran City Inside Nippon Steel Corporation Muroran Works (72) Inventor Hiroaki Hayashi 12, Nakamachi, Muroran City Nippon Steel Corporation Muroran Inside the steelworks (72) Inventor Masato Kobayashi F-term in the Nippon Steel Corporation 2-6-3 Otemachi, Chiyoda-ku, Tokyo (reference) 4K002 AC09 AE02 AE06 4K014 AA01 AA03 AE01

Claims (3)

[Claims] 1. De-S as hot metal pretreatment using a converter
In the converter refining method for performing i and P removal, the molten iron of the next heat is charged while the slag after the removal of the P treatment is left in the furnace without discharging after tapping, and oxygen is supplied to remove the Si. A converter for producing by-produced steelmaking slag with low free lime content, characterized in that after the removal of Si, a blowing process is temporarily interrupted to provide an intermediate waste disposal step of discharging the slag, and thereafter the P-refining is continuously performed. Refining method. 2. After the de-P treatment, the slag is left in the furnace and the slag containing free lime generated in other steps is de-S
2. The converter refining method according to claim 1, wherein the converter is charged into the furnace before i treatment. 3. De-S as hot metal pretreatment using a converter.
In the converter refining method for performing i and de-P, prior to blowing, slag containing free lime generated and recovered in its own process or another process is charged into a furnace, oxygen is supplied, and de-Si treatment is performed. Converter refining by-producing steelmaking slag with a low free lime content, characterized by providing an intermediate waste disposal step to temporarily stop blowing after the removal of Si and discharge the reformed slag, and then continue to remove P. Law.