JP2002060826A - Converter type pretreating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a converter type pretreating method with which the pretreating cost in refining process can drastically be reduced without increasing the non-melted scrap so that the steelmaking cost is reduced drastically, and further desirably, metal-containing slag generated in the refining process can be recovered and the blowing can be performed at the low temperature and improvement of a dephosphorizing performance can be expected. SOLUTION: Before the converter type pretreatment is performed, crude concentrate is charged into the first converter and successively, molten iron is charged and further, burnt lime, ingot-making slag and auxiliary raw material containing silica rock, are charged, and after adjusting the basicity to 1-4, the blowing is started. The iron ore is charged and the temperature is adjusted to 1250-1400 deg.C, and the dephosphorized molten iron is tapped off from the first converter and this dephosphorized molten iron is again charged into the second converter, and main blowing is performed to attain the above purpose.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of a converter refining method for iron and steel products in general, and more particularly to a crude concentrate obtained as a substitute for scrap, for example, a crude concentrate obtained by recovering metal in slag. The present invention relates to a converter type pretreatment method that reduces the cost of pretreatment in refining and reduces steelmaking cost.

[0002]

2. Description of the Related Art In a steelmaking method combining dephosphorization of hot metal using a dephosphorization furnace and a decarburization furnace and decarburization blowing of dephosphorized hot metal, a converter for performing dephosphorization refining is generally used. Scrap is added. Such techniques include, for example, JP-A-08-209228 and JP-A-10-24561.
The method disclosed in Japanese Patent Application Publication No. 4 (KOKAI) No. 4 is known.

[0003] Of the above prior arts, Japanese Patent Application Laid-Open No. 08-209
The technology disclosed in Japanese Patent Publication No. 228 is one of two converter type refining furnaces having an upper blowing or upper and lower blowing function, one of which is a dephosphorizing furnace,
The other is a steelmaking method using a decarburization furnace, in which a cold iron source such as scrap is charged into both the dephosphorization furnace and the decarburization furnace for refining. With this technology, poor dephosphorization and poor calcification of calcined lime due to the introduction of cold iron source only into the dephosphorization furnace, and lack of heat due to the introduction of the cold iron source only to the decarburization furnace and the accompanying high cost of graphite etc. High productivity, good dephosphorization,
A steelmaking method with low refining cost has been achieved.

The technique disclosed in Japanese Patent Application Laid-Open No. H10-245614 is a steelmaking method using two converter type refining furnaces as in the above-described technique, and a low S
The hot metal containing i (0.3% wt or less) is dephosphorized and refined, and the obtained dephosphorized hot metal is inserted into the other converter to perform decarburization refining within the dephosphorizing refining time. Thus, the use of low-Si hot metal reduces the amount of slag generated, reduces the time spent mainly on waste, shortens the time for dephosphorization refining and makes it about the same as the time for decarburization refining, and increases the idle time of the decarburization refining furnace. By eliminating them, steelmaking efficiency is improved as a whole.

[0005]

By the way, in the dephosphorization refining in the converter, since the treatment is performed at a lower temperature than in the decarburization refining, the dephosphorization refining is carried out as in the techniques disclosed in the above publications. There is a problem that when the scrap is charged sometimes, the scrap may remain undissolved. In addition, in the dephosphorization blowing, if a large amount of oxygen gas is used to dissolve the scrap, there is a problem that the oxygen gas basic unit is increased and the blowing time is necessarily extended.
Furthermore, during the dephosphorization refining, charging scraps
There are also problems such as an increase in refining costs or inability to collect metal-containing slag generated in the refining process.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and the use of coarse slag concentrate as a substitute for scrap, which raises the cost of refining, makes the scrap undissolved. Without reducing the cost of pretreatment in refining.
As a result, it is a main object to provide a converter type pretreatment method capable of greatly reducing steelmaking costs.

Another object of the present invention is to recover metal-containing slag generated in the refining process, and to recover metal-containing slag generated in the refining process. It is an object of the present invention to provide a converter type pretreatment method capable of blowing and improving the dephosphorization ability.

[0008]

Means for Solving the Problems In order to achieve the above object, the present inventors have proposed a method for significantly reducing the cost of preliminary processing in converter refining in order to achieve a significant reduction in steelmaking costs. As a result of earnest research, there is a large amount of impurities mixed with ingots and slag, and there is concern that rephosphorization and resulfurization will occur. It is necessary and conventionally, it is crude steel obtained by collecting slag ingots that have been sold as scrap iron and has not been used as a converter material up to now, but it is inexpensive and costs of steelmaking are low. Knowing that this would be an effective technology if it could be linked to reductions, such coarse slag concentrate was used as a substitute for scrap in dephosphorization blowing without the need to worry about rephosphorization and resulfurization. To refine this crude ore By enabling started use in Bei process, and have reached the present invention.

That is, according to the present invention, in performing the converter type pretreatment, the coarse concentrate is charged into the first converter, then the molten iron is charged, and then the calcined lime, the slag slag and An auxiliary material containing at least one type of silica stone is charged, and the slag basicity (CaO
/ SiO ₂ ) is adjusted to 1 to 4, after which blowing is started, iron ore is charged, the temperature is adjusted to 1250 to 1400 ° C., and dephosphorized hot metal is tapped from the first converter. The present invention also provides a converter type pretreatment method characterized by charging the dephosphorized hot metal again into the second converter and performing main blowing. Here, the first converter and the second converter may be the same converter or different converters.

[0010] In the present invention, the crude ore refers to a metal obtained by recovering metal from slag generated at the time of desiliconization, dephosphorization, desulfurization, etc. of hot metal. That is, the coarse concentrate is
It is preferable that metal is recovered from slag generated during at least one of the steps of desiliconization, dephosphorization and desulfurization of the hot metal. Further, it is preferable that the crude concentrate has a metal content of 20% or more in the crude concentrate.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a converter type pretreatment method according to the present invention will be described in more detail.

In the converter type pretreatment method of the present invention,
Converter blowing is performed using coarse concentrate as an alternative to scrap (cold iron source) as follows. (1) First, a coarse concentrate is charged into a converter. (2) Next, hot metal is charged. (3) Subsequently, auxiliary raw materials such as calcined lime, slag and silica stone are charged. At this time, the basicity (CaO / SiO ₂ ) is set to 1 to 4
Adjust to (4) Thereafter, blowing, that is, dephosphorization blowing is started. At this time, iron ore is charged, and dephosphorization blowing is performed while adjusting or controlling the tapping temperature of the hot metal from the converter to be 1250 to 1400 ° C. (5) When the dephosphorization blowing is completed, the dephosphorized hot metal is discharged from the converter. Here, the reason why tapping is carried out once is to remove slag at the time of dephosphorization blowing and to prevent rephosphorization. (6) Next, the dephosphorized hot metal that has been tapped is charged into the same converter or another different converter again (when using the same converter,
After tapping, the waste is used.) (7) In the converter into which the dephosphorized hot metal has been charged, main blowing, that is, decarburization blowing is performed. (8) After the components are adjusted by decarburization blowing, the component-adjusted decarburized molten steel is tapped.

First, the converter type pretreatment method according to the present invention is characterized by using coarse slag concentrate as a substitute for scrap charged in converter refining. The coarse concentrate used in the present invention is not particularly limited as long as it is a coarse refined steel of slag that can be used as a substitute for scrap.
Metal-containing slag generated in the refining process that can be recovered as an iron source when used in a converter or the like can be given. Such a crude steel is, for example, one recovered using the recovery method disclosed in Japanese Patent Publication No. 53-721 and the recovery method disclosed in the prior art in the publication. You can list everything you have.

That is, in the converter refining of the present invention, coarse concentrate charged as a substitute for scrap is obtained by recovering ingots from slag generated during desiliconization, dephosphorization, desulfurization, etc. of hot metal. Can be used. The slag is
After cooling, the metal is crushed and the metal is collected by magnetic separation.However, even if the metal in the slag is usually crushed, its surface is often covered with slag, and in this state it is difficult to perform magnetic separation. Thereafter, the crushed material is crushed again by a crusher or the like, and is collected by magnetic separation. As coarse concentrates that can be used in the present invention, not only ingots recovered by magnetic separation, but also ingots that are allowed to cool and then crushed and remaining in the magnetic separation after the magnetic separation can be used. . The reason is,
When slag, which usually adheres to the metal, is used in the converter,
The reason for this is that it is not used because it causes phosphorus reversion, but in the converter refining according to the present invention, it is rendered harmless by adjusting the basicity and exhibits a dephosphorization function. If the amount of slag attached to the slag is large, the amount of slag produced during the operation of the converter is increased. Therefore, the slag content is preferably 20% or more. In other words, the metal content in the coarse concentrate is 20%
Those magnetically selected as described above are preferable, and those having a total iron content (T.Fe; Total Fe) of 50% or more can be suitably used.

As described above, coarse ore obtained from such metal-containing slag contains a large amount of impurities in which metal and slag are mixed. Is concerned. For this reason, in order to use such crude steel in converter blowing, it is necessary to follow up, such as lowering the S of the hot metal to be compounded.Conventionally, it has been sold as scrap iron. As previously described, it was not used. However, such coarse concentrates are inexpensive and can lead to a reduction in steelmaking costs. For this reason, the present invention eliminates the fear of rephosphorization and resulfurization by using such crude steel in dephosphorization blowing in converter refining, and is possible for the first time in crude refinery refining pretreatment. It was.

In the converter type pretreatment method of the present invention, as described above, first, in the first step of the coarse concentrate insertion step,
The converter is charged with coarse concentrate instead of scrap. Next, in a second step, which is a hot metal charging step, the hot metal is charged into the converter in which the coarse concentrate has been charged. Subsequently, in a third step, which is an auxiliary raw material charging step, auxiliary raw materials such as calcined lime, slag, and silica stone are charged into the converter into which the coarse concentrate and the hot metal have been charged.
At this time, the basicity (CaO /
SiO ₂ ) is adjusted to be 1 to 4.

The auxiliary raw material charged into the converter in the third step is an auxiliary raw material used for dephosphorization refining, and mainly adjusts the basicity (CaO / SiO ₂ ) of the slag in the converter. Lime (CaO), lumps containing a large amount of Al ₂ O ₃ which is a slag accelerating agent for this calcined lime, and calcined lime (C
aO) together with silica (SiO ₂ ) for adjusting the basicity of the melt, and any other material that can be adjusted to the desired basicity may be used. These may be included, and conventionally known auxiliary raw materials can be used. In this case, at least one of the auxiliary materials such as calcined lime, slag, silica stone, and the like is placed in the converter so that the basicity of the slag in the converter becomes 1 to 4 as the auxiliary material. You just need to put it.

In the present invention, the basicity (CaO / SiO ₂ ) of the melt containing the hot metal in the converter in the dephosphorization refining is set to 1
The reason for adjusting to ４4 is that the promotion of slagging and the improvement of dephosphorization ability can be expected. That is, if the basicity is less than 1, the dephosphorization ability due to the reduction of CaO in the slag is reduced, and the increase in the phosphorus content due to the use of coarse concentrate cannot be avoided. Because it causes

Thereafter, blowing of hot metal in the converter using oxygen gas, that is, dephosphorization blowing is started, and a fourth step, which is a dephosphorization blowing step, is performed. At this time, iron ore is introduced as a cooling oxygen source, and the temperature of the dephosphorized hot metal at the end of the dephosphorization blowing, that is, the tapping temperature of the hot metal from the converter is 1250 to
Dephosphorization blowing is performed while being adjusted or controlled to be 1400 ° C. Dephosphorization blowing is performed on the melt charged in the converter and having the basicity adjusted to 1 to 4. Here, blowing using oxygen gas can be performed according to a conventional method, and iron ore as a cooling oxygen source can be input according to a conventional method.

In the fourth step of the present invention, while controlling or adjusting the temperature of the dephosphorized hot metal at the end of the dephosphorization blowing, that is, the tapping temperature of the hot metal from the converter, is 1250 to 1400 ° C. The dephosphorization blowing is performed because the lower the temperature, the more effective the dephosphorization and the improvement of the dephosphorization ability can be achieved. That is, the tapping temperature (dephosphorization end temperature) is 125
If the temperature is lower than 0 ° C, poor slag slag formation, deterioration of the slagging property, and insufficient heat source during decarburization blowing will occur. This is because of the decline. Therefore, 1250-14
The tapping temperature is preferably set as high as possible within a range where the dephosphorization ability of 00 ° C. can be guaranteed, and preferably 1300 to 138
0 ° C is good.

After adjusting the basicity in the converter to 1 to 4 as described above, the tapping temperature (dephosphorization end temperature) is set to 1250 to 14
By performing the dephosphorization blowing while controlling the temperature to 00 ° C., it is possible to maintain the dephosphorization ability while reducing the refining cost even when coarse concentrate is used instead of scrap. When the dephosphorization blowing is completed in this way, in the fifth step which is the dephosphorization hot metal tapping process, the tapping temperature (dephosphorization end temperature) from the converter
The dephosphorized hot metal is tapped at 1250 to 1400 ° C. Thus, the hot metal dephosphorization treatment including the first to fifth steps is completed.

Next, the dephosphorized hot metal thus tapped is charged into the converter again, and main blowing, that is, decarburizing blowing is performed according to a conventional method. Here, the converter in which the dephosphorized hot metal is charged again may be a converter that has been subjected to a dephosphorization blowing process,
Another converter different from this may be used. The dephosphorized hot metal charged with the slag crude refined steel and dephosphorized and blown is converted into slag where many impurities contained in the crude refined steel at the time of dephosphorization blowing are slagged together by auxiliary raw materials. At the same time, tapping from the converter in the dephosphorization blowing process is performed, and the dephosphorized hot metal that has been tapped into a clean converter that does not contain impurities and the like that are often contained in crude steel is recharged to convert the hot metal. Eliminate concerns about steel contamination such as rephosphorization and resulfurization caused by using crude steel as a substitute for scrap in furnace refining, and decarburize and blow dephosphorized hot metal in a clean converter to improve cleanliness. Molten steel can be obtained, and clean steel can be obtained.

Such a decarburization blowing process is performed as follows. First, in the sixth step, which is a dephosphorization hot metal charging step, the dephosphorized hot metal that has been tapped is charged again into the same converter or another different converter. Next, in a seventh step, which is a decarburization blowing step, the dephosphorized hot metal charged in the converter is subjected to main blowing using oxygen gas, that is, decarburization blowing according to a conventional method. As a result, the composition of the decarburized molten steel is adjusted. When the decarburization blowing is completed in this way, in the eighth step, which is a decarburized molten steel tapping step, the decarburized molten steel whose components have been adjusted is discharged from the converter. Thus, the decarburization blowing process comprising the sixth to eighth steps is completed. The converter type pretreatment method of the present invention is basically configured as described above.

According to such a converter type pretreatment, the use of inexpensive crude ore can greatly reduce steelmaking costs, and also recovers metal-containing slag generated in the refining process as an iron source. Because it is possible, it is also beneficial in terms of recycling. In addition, since slag in the coarse concentrate promotes slagging at the initial stage of blowing, the dephosphorization ability can be improved.

That is, in the above embodiment, calcined lime, silica stone and the like are added as auxiliary materials, and the basicity (CaO / S
By adjusting iO ₂ ) in the range of 1 to 4, promotion of slagging and dephosphorization ability can be expected. Furthermore, since the lower the processing temperature is, the more effective the dephosphorization blowing of the hot metal is, the (phosphorization) temperature at the end of the dephosphorization blowing is set to 1250 to 1400 ° C, so that the dephosphorization is performed. Performance can be improved.

Further, in the converter type pretreatment method according to the present invention, by using the converter twice or by using two converters, it is possible to use inexpensive coarse concentrate instead of scrap. Can be made possible. Here, the first converter for performing dephosphorization blowing and the second converter for performing decarburization blowing are:
Another converter or the same converter may be used. First, dephosphorization treatment is performed in the first converter to eliminate steel contamination associated with the use of coarse concentrate,
The tapping amount of the first converter is charged into a second converter, and in the second converter, decarburization blowing is performed by a conventional method.
Clean steel can be obtained.

Hereinafter, the present invention will be specifically described with reference to examples.

[0028]

EXAMPLES First, refining costs in converter refining of hot metal were estimated. The result is shown in FIG. Refining when the ratio of hot metal charged from the outside to the converter to the total hot metal content in the converter is the hot metal ratio by charging scrap or crude steel into the converter, and the hot metal ratio is 90%. When the refining cost when the hot metal ratio is 100% is "1", (1) Hot metal ratio: 90%, and when 10% scrap is used: 0.95 (2) Hot metal ratio: 90%, When using 10% crude steel:
It was 0.88. As is clear from FIG. 1, the refining cost reduction effect of the converter type pretreatment method according to the present invention is remarkable.

(Example 1) First, 5.4 tons of crude slag concentrate generated in a slag yard was charged into a converter, and 177.0 tons of hot metal having a Si content of 0.3 wt% or less were charged. Charge
The hot metal content was 97%. In addition, to promote dephosphorization and adjust the basicity, calcined lime 5.1 kg / t, lumps slag 5.6 k
g / t was charged beforehand and dephosphorization blowing was started. The basic unit of oxygen gas used for dephosphorization blowing was 10.9 Nm ³ / tp · p, and the iron ore charged as a cooling / oxygen source was 39.8 kg / t.
The blowing time was 6.9 minutes.

Example 2 In the same converter as in Example 1, 10.0 tons of coarse concentrate and 190.0 tons of hot metal were charged.
The hot metal ratio was 95%. The timing of charging the auxiliary material and the blowing pattern were substantially the same as those in Example 1. In the same manner as in Example 1, 4.9 kg / t of calcined lime and 5.4 kg / t of lump slag were charged beforehand to promote dephosphorization and adjust basicity. 50.1 kg / t of iron ore was introduced as a cooling / oxygen source, and the oxygen gas basic unit used for dephosphorization blowing was 10.5 Nm.
³ / tp · pulverization time was 6.3 minutes.

(Comparative Example) As a comparative example, in the dephosphorization refining, scrap was placed in the same converter as in Example 1 for 10.
0t, 193.8t of hot metal were charged, and a comparative study was conducted by taking a conventional case in which hot metal was charged at a mixing ratio of about 95%. At this time, calcined lime 5.1k was used as an auxiliary material.
g / t, ingot slag 5.4 kg / t, iron ore 52.2 kg / t as a cooling / oxygen source was charged, and the oxygen gas consumption unit used for dephosphorization blowing was 10.7 Nm ³ / t · p. The blowing time was 6.5 minutes.

Table 1 shows the change in the component concentration in the converter type hot metal pretreatment (dephosphorization blowing) in each of the cases of Example 1, Example 2 and Comparative Example, together with the change in temperature.

[0033]

[0034] The decarburization blowing method is the same as usual.

As is clear from Table 1, first, Example 1
According to the dephosphorization action, 0.137 before dephosphorization blowing.
% After the dephosphorization blowing.
The reduction rate is about 23%, whereas the reduction rate of the comparative example is about 36%, and the absolute amount is about 60% of that of the comparative example. You can see that. After dephosphorization blowing, tapping and decarburization blowing were performed, and as shown in Table 2, components after decarburization blowing were obtained. Decarburization blowing is a conventional method, in addition to oxygen blowing by top and bottom blowing, lime, to prevent dust generation during blowing and to prevent refractory melting.
Dolomite was put into operation. Despite the use of coarse concentrate, there is no quality problem.

On the other hand, according to Example 2, the change in the content of phosphorus (P) is about 30% in the reduction rate, while it is about 36% in the comparative example. It turns out that it is big. In the comparative example, carbon having no change was 4.30% before dephosphorization blowing, but was 3.30% after dephosphorization blowing.
It has been reduced to 29% (a reduction rate of about 76%), and the effect of having a decarburizing effect has also been obtained. As is clear from the above, both Examples 1 and 2 have an effect of improving the dephosphorization and decarburization effects in addition to the remarkable reduction effect of the refining cost as compared with the comparative example.

The converter type pretreatment method according to the present invention has been described with reference to various embodiments.
This is an example of the present invention, and it goes without saying that the present invention should not be limited to this, and that improvements and design changes may be made without departing from the gist of the present invention. Of course.

[0038]

As described above in detail, according to the present invention, in the dephosphorization blowing of the converter type pretreatment method, the crude concentrate is used as a substitute for the scrap, so that the dephosphorization is performed. In addition, the steelmaking cost can be significantly reduced while suppressing resulfurization, and the metal-containing slag generated in the refining process can be recovered.

Further, according to the present invention, since the coarse concentrate contains slag, slagification is promoted in the early stage of blowing, and
Since it is easier to dissolve than scrap, it can be blown at lower temperatures, which makes it possible to improve the dephosphorization capacity during blowing when using coarse concentrate, and coarse concentrate can be used like scrap. Since it does not become undissolved, the effect that the blowing time can be shortened can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating the refining cost reduction effect of a converter type pretreatment method of the present invention.

Continued on the front page (72) Inventor Toshio Fujimura 1-chome, Mizushima-Kawasaki-dori, Kurashiki-shi, Okayama Pref. None) Kawasaki Steel Corporation Mizushima Works F term (reference) 4K002 AB01 AB04 AC09 AE02 AE06 4K014 AA03 AB02 AB03 AB04 AC11 AD00 AE01

Claims (4)

[Claims] In a converter type pretreatment, crude ore is charged into a first converter, and then hot metal is charged. Then, at least one of calcined lime, slag and silica is charged. After feeding the auxiliary material including seeds and adjusting the slag basicity to 1 to 4, blowing is started, and iron ore is charged to raise the temperature to 1250 to 14
The dephosphorized hot metal is tapped from the first converter at a temperature adjusted to 00 ° C., and the dephosphorized hot metal is charged into the second converter again to perform main blowing. Mold pretreatment method. 2. The converter type pretreatment method according to claim 1, wherein the first converter and the second converter are the same converter. 3. The converter type pretreatment method according to claim 1, wherein the first converter and the second converter are different converters. 4. The crude ore concentrate according to any one of claims 1 to 3, wherein metal is recovered from slag generated during at least one treatment of desiliconization, dephosphorization and desulfurization of the hot metal. A converter type pretreatment method according to any one of the above.