JP2002285217A - Dephosphorizing agent and desulfurizing agent for molten iron and molten steel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dephosphorizing agent and a desulfurizing agent for molten iron and molten steel consisting essentially of inexpensive CaO which can safely be used without affecting any troubles to the working environment and a facility and devices, etc., and also, has a reactivity and a slag-removability almost the same degree as in the case of adding CaF2 . SOLUTION: These agents comprise addition of a compound containing Na2 O into the treating agent consisting essentially of lime.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a dephosphorizing agent and a desulfurizing agent for hot metal and molten steel, and more particularly to a dephosphorizing agent used for dephosphorizing and / or desulfurizing hot metal and molten steel. It relates to a desulfurizing agent.

[0002]

2. Description of the Related Art Recently, inexpensive quicklime (desulfurizing agent) has been used as a dephosphorizing agent or desulfurizing agent for dephosphorizing or desulfurizing hot metal or molten steel contained in a reaction vessel such as a ladle. CaO) is often used as a main component. In the treatment agent containing CaO as a main component, the reaction efficiency of dephosphorization and desulfurization is poor even if CaO having a high melting point is added alone.
In some cases, fluorite (CaF ₂ ) is used in order to improve the dephosphorization and desulfurization reactivity and to improve the slag removal properties (for example, Japanese Patent Publication No. 5-57325 discloses a dephosphorization agent).
JP-B-55-51402 for the publication and desulfurizing agent).

[0003] Although CaF ₂ has the effect of lowering the melting point of CaO, which is the main component of the treating agent, and at the same time improving the reactivity and scum-removing properties as described above, it has recently been considered due to environmental considerations. Its usage tends to be suppressed,
Further, when the slag containing CaF ₂ is cooled and solidified and then pulverized and reused, its use may be limited. Therefore,
Development of CaF ₂ alternative agents having the same functions and effects as CaF ₂ is needed.

Japanese Patent Publication No. 55-51402 describes a combined use of quick lime (CaO) and soda (page 1, column 2, lines 8 to 23 of the same publication). s is soda ash as illustrated (Na ₂ CO _3), a caustic soda (NaOH), which are as described in the publication, the generation of white smoke during processing, the lining of the processing vessel ( There are drawbacks such as erosion of the refractory and fluctuations in the composition of the hot metal.

[0005] On the other hand, the applicant of the present invention has previously described Ca as a main agent.
O (70 to 95% by mass) and SiO ₂ as an auxiliary agent: 65
80 wt%, Na ₂ O: 10~20 wt%, CaO:
Soda-lime glass having a composition of 5 to 15% by mass (5 to 15% by mass)
30% by mass) (see JP-A-8-209212). In this proposal,
Compared to the conventional Na ₂ CO ₃ -based desulfurizing agent, Na in the desulfurizing agent
_Since the concentration of ₂ O is as low as 6% by mass at the maximum, the slag after desulfurization treatment of hot metal can be reused as a cement raw material without being restricted by the remaining amount of Na ₂ O as in the conventional case. Further, by mixing soda-lime glass as an auxiliary agent, slagification of CaO as a main agent is promoted, and CaO1
The effect of increasing the desulfurization rate of hot metal was obtained with a smaller unit of desulfurizing agent than when it was 00%.

[0006] However, as a result of a subsequent investigation and examination,
In the proposed hot metal desulfurizing agent, the addition of Na ₂ O is as small as 6% by mass as a whole, so that the basicity of the slag at the time of desulfurization treatment is reduced, and it is found that a sufficient desulfurizing action by CaO cannot be obtained. It can be used for dephosphorization.

The present invention has been made based on the above-mentioned circumstances, and an object of the present invention is to use an inexpensive CaO-based treating agent safely without harming the working environment and equipment. An object of the present invention is to provide a dephosphorizing agent and a desulfurizing agent for hot metal and molten steel having substantially the same reactivity and slag removal properties as when CaF ₂ is added.

[0008]

Means for Solving the Problems In order to achieve the above object, a dephosphorizing agent for hot metal and molten steel according to the present invention (claim 1) is a treating agent mainly containing quick lime (CaO).
It is obtained by adding a compound containing ₂ O.

[0009] The applicant of the present invention used CaF _{2 when} performing a dephosphorization treatment or a desulfurization treatment using a treatment agent containing CaO as a main component.
As a result, we have been developing alternative agents to replace the additives that cause harm to the working environment, equipment, etc. As a result, soda-lime glass (5 to 30% by mass) is used as a treatment agent suitable for desulfurization treatment. A desulfurizing agent for hot metal comprising the addition of is proposed (see JP-A-8-209212). And
In subsequent investigations and developments, the present inventors have found that Na ₂ O contained in soda-lime glass has a CaO ₂ melting point drop equivalent to CaF ₂ as shown in FIG. Oxide of phosphorus generated and oxidized from the inside is (P ₂ O ₅ ) +3 (Na ₂ O) = 3 (Na ₂ O) · P ₂
It reacts like O ₅ , fixes it in slag, and has a dephosphorizing effect. Further, since Na ₂ O is a very unstable compound at normal temperature, CaO is mainly composed of Na ₂ O as it is. The present invention (Claim 1) has found that it is difficult to add and use a treating agent to be used in the form of a compound containing Na ₂ O.

The above Na_TwoAs compounds containing O, general
Soda ash (Na_TwoCO_Three) Is used, but this
Add soda ash to CaO-based treatment agent for use
Is easily reduced by C and Al in hot metal and steel
Peripheral equipment such as exhaust duct of processing equipment that generates Na vapor
There is a concern that it will corrode. Therefore, the present inventors strongly consider
Na, a basic oxide_TwoO stabilized with acidic oxide
With the use of the Na gas, there is no concern about the Na vapor.
Thought, Na_TwoO and SiO which is an acidic oxide_TwoIs a compound
Of the present invention
(Claim 2)_TwoThe compound containing O is converted to Na_TwoO
Containing silicate. In addition, Na _TwoSilicon containing O
Soda lime glass and sodium orthosilicate
And they can be suitably used. The saw
Na in lime glass_TwoGlass cullet containing O
Glass raw materials for glass production), waste glass, etc.
You. Cost reduction, especially by using waste glass
It is also possible to achieve.

Further, the Na as the silicate containing ₂ O, which in its silicate comprising a Na ₂ O of 20 mass% or more can be preferably used (claim 3). The reason why the silicate containing 20% by mass or more of Na ₂ O is preferable as described above is that when the content of Na ₂ O is less than 20% by mass, the melting point of CaO as the main component and the phosphorus due to Na ₂ O itself are reduced. Is not expected to be fixed, and the basicity (CaO / SiO ₂ ) of the slag may be unnecessarily reduced due to the high SiO ₂ concentration, which may also cause a decrease in the dephosphorization ability. is there.

Further, the treating agent containing CaO as a main component is not particularly limited, but may not contain CaF ₂ at all (claim 4). As described above, by adding the compound containing Na ₂ O, it can substitute for the melting point lowering function of CaO of CaF ₂ and increase the dephosphorizing ability of CaO, and Na ₂ O itself has the dephosphorizing ability. It is.

In order to achieve the above object, the desulfurizing agent for hot metal and molten steel according to the present invention (Claim 5) comprises a treating agent mainly composed of quick lime (CaO), and Na ₂ O containing 6%. It is obtained by adding a compound containing Na ₂ O so as to exceed the mass%. By adding more than 6% by mass of Na ₂ O, the melting point of CaO is lowered to increase the desulfurizing ability of CaO itself, as shown in FIG. 1, while the desulfurizing ability of Na ₂ O itself is sufficiently increased. If the addition of Na ₂ O is less than 6% by mass, the expectation of such an effect is weakened. In addition,
Desulfurization by Na ₂ O is possible to react sulfur and Na ₂ O in the molten iron and molten steel as with desulfurization action of CaO to produce sodium sulfide (Na ₂ S), to fix the Na ₂ S in the slag Done by

The compounds containing Na ₂ O include:
A silicate containing Na ₂ O and more than 20% by mass of N
Those containing a ₂ O can be suitably used (claim 6). The reason why the silicate containing more than 20% by mass of Na ₂ O is preferable as described above in the case of the dephosphorizing treatment agent is to suppress the generation of Na vapor and to make the above-mentioned N
This is for exhibiting the function and effect of a ₂ O. In the silicate containing less than 20% by mass of Na ₂ O,
In order to add more than 6% by mass of Na ₂ O, it is necessary to add a large amount of the silicate, and it is necessary to reduce the amount of inexpensive CaO. I can not expect much.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The dephosphorizing agent and desulfurizing agent for hot metal and molten steel of the present invention are obtained by adding a compound containing Na ₂ O to a treating agent mainly containing quick lime (CaO).

In the following, C containing a silicate containing Na ₂ O is added.
Dephosphorization ability and desulfurization ability when using aO-based dephosphorizing agent and CaO-based desulfurizing agent were investigated, and when CaO-based dephosphorizing agent and CaO-based desulfurizing agent added with conventional CaF ₂ were used. And dephosphorization ability were compared.

First, C containing silicate containing Na ₂ O is added.
The investigation and results of the dephosphorization ability of the aO-based dephosphorizing agent and the CaO-based dephosphorizing agent added with CaF ₂ will be described below.

In this investigation, 1 kg of pig iron having an initial phosphorus concentration of 0.085% was placed in an MgO crucible, heated and maintained at 1350 ° C., and then the following four types of fluxes were added thereto and stirred by argon bubbling. The hot metal was sampled by suction at predetermined intervals and analyzed by phosphorus analysis. FIG. 2 shows the results of this investigation. The four types of flux are C
aO and Fe ₂ O ₃ in a ratio of 1: 1 (CaO = 50 g: Fe
₂ O ₃ = 50 g) were mixed with flux (1), the flux (1) further flux with the addition of CaF ₂ quantity (5 g) striking the 10% CaO (2), the flux further of CaO to (1) 10% Na ₂ (5 g)
O and silicate containing _{Na 2 O 20% (20%} Na 2 O-8
0% SiO ₂ ), the flux (3) added to the flux (1) and an amount (5 g) of Na equivalent to 10% of CaO (5 g).
The ₂ O, silicate containing 60% _{Na 2 O (60% Na 2} O-
Flux (4) added with 30% SiO ₂ -10% H ₂ O).

FIG. 2 shows the change over time of the phosphorus concentration in the hot metal for each flux. As is clear from FIG. 2, in each of the flux (2) to which CaF ₂ was added and the flux (3) or (4) to which Na ₂ O was added,
It can be seen that the dephosphorization is more advanced by the addition than in the case of the CaO-only flux (1). In addition, CaF
It can be seen that the effect of promoting dephosphorization is almost the same between ₂ and Na ₂ O. Here, SiO ₂ contained in the silicate lowers the dephosphorization ability to lower the basicity of the slag, but since Na ₂ O itself has the dephosphorization ability, the dephosphorization ability by SiO ₂ is reduced. Is likely to have been offset. However, the flux (3) to which silicate containing 20% of Na ₂ O was added and the flux of Na ₂ O of 60% were used.
% Compared with the case of flux (4) to which silicate is added, since the latter has higher dephosphorizing ability than the former, the Na ₂ O concentration in the silicate is as high as possible. Deemed desirable.

Next, C containing silicate containing Na ₂ O is added.
The investigation and results of the desulfurization ability of the aO-based desulfurizing agent and the CaO-based desulfurizing agent added with CaF ₂ will be described below.

In this study, 1 kg of pig iron to which iron sulfide was added so as to have an initial sulfur concentration of 0.06% was placed in an MgO crucible, heated and maintained at 1350 ° C., and the following four types of fluxes were added. Then, stirring was performed by argon bubbling, and hot metal was sucked and collected at predetermined time intervals, and a sulfur analysis was performed to investigate. FIG. 3 shows the results of this investigation. In addition,
Four kinds of flux are CaO plain (CaO = 50g)
Flux (5), and this flux (5) further contains Ca
The flux (6) to which CaF ₂ was added in an amount corresponding to 20% of O (10 g), and the flux (5) further contained 20% of CaO.
The Na ₂ O in an amount hitting percent (10 g), flux (7) supplemented with silicate _{(20% Na 2 O-80} % SiO 2) containing Na ₂ O 20%, further the CaO in the flux (5) 2
Quantity corresponds to 0% of Na ₂ O of (10 g), the Na ₂ O 60%
Silicate containing (60% Na ₂ O-30% SiO ₂ -10% H
₂ O) fluxes (8) added.

FIG. 3 shows the sulfur concentration in the hot metal for each flux.
It shows a change with time of the degree. As is clear from FIG.
And CaF_Two(6) with Na added and Na_TwoO
In any of the added fluxes (7) and (8),
By adding CaO only flux (5)
It can also be seen that desulfurization is progressing. In addition, CaF _Two
And Na_TwoThe effect of accelerating desulfurization with O is almost the same.
I understand. Here, the SiO contained in the silicate_TwoIs a slag
Reduces the desulfurization ability to lower the basicity of
But Na_TwoO itself has desulfurization ability
Et al., SiO_TwoDecrease in desulfurization ability due to
available. However, Na_TwoSilicate containing 20% O
In case of added flux (7) and Na_TwoContains 60% O
And flux (8) with added silicate
In comparison, the latter has a higher desulfurization capacity than the former.
Therefore, Na in silicate_TwoO concentration is as high as possible
Is considered more desirable.

Further, from the studies described above, silicates containing Na ₂ O has a dephosphorization capacity desulfurization ability substantially equal to the CaF _2, the same lime dephosphorization treatment agent and desulfurization agent and CaF ₂ It became clear that it can be added and used.
The above study is the dephosphorization treatment and desulfurization treatment were those simulating in hot metal, even when carried out a similar investigation in simulated to 1600 ° C. The dephosphorization desulfurization of the molten steel, Na ₂ O Flux containing silicate containing Ca
It was confirmed that the flux had the same effect as the flux to which F ₂ was added.

[0024]

EXAMPLES As an example of the present invention, a dephosphorization treatment was performed by the following treatment method. A desiliconization treatment was performed on the blast furnace cast floor, and 280 t of the desiliconized hot metal was received by a mixed iron wheel. The hot metal components at this time were: C: 4.5%, Si: 0.17%, Mn:
0.15%, P: 0.098%, S: 0.017%. After removing the desiliconized slag on the hot metal with a slag dragger, quicklime powder 19 kg / t and iron ore powder 24 kg /
A flux mixed with silicate containing 60% of t and Na ₂ O was blown together with nitrogen gas from a lance immersed in the hot metal to remove phosphorus. Here, the addition amount of the silicate was set to 1.7 kg / t so that the addition amount of Na ₂ O became 1.0 kg / t. During the dephosphorization treatment, oxygen gas was sprayed onto the hot metal from a water-cooled lance at 1.8 m ³ / t. In the above treatment, no CaF ₂ was used at all.

In the mixed iron wheel that has been subjected to the above treatment, the phosphorus concentration after the dephosphorization treatment is P: 0.018%, which is the conventional Ca concentration.
Dephosphorization efficiency comparable to obtain a time which has been added using the F _2, and very good also Haikasu resistance, slag deposition on the torpedo car bottom did not occur.

Next, as an embodiment of the present invention, a desulfurization treatment was carried out by the following treatment method. Hot lime powder 2.5 kg / t, calcium carbide 2.2
A flux containing kg / t and a silicate containing 60% of Na ₂ O was blown from a lance immersed in the hot metal using nitrogen gas to perform desulfurization treatment. At this time, the hot metal components in the mixed iron wheel were C: 4.4%, Si: 0.20%, Mn: 0.1%.
18%, P: 0.096%, and S: 0.014%. The addition amount of the silicate was 0.8 kg / t so that the addition amount of Na ₂ O was 0.5 kg / t. In the above treatment, no CaF ₂ was used at all.

In the mixed iron wheel that has been subjected to the above desulfurization treatment, the sulfur concentration after the desulfurization treatment is S: 0.003%, and the same desulfurization efficiency as when conventional CaF ₂ is used is obtained. In addition, the slag property was extremely good, and no slag was deposited on the bottom of the mixed iron wheel.

Next, as a comparative example, a dephosphorization treatment was performed by the following treatment method. A desiliconization treatment was performed on the blast furnace cast floor, and 280 t of the desiliconized hot metal was received by a mixed iron wheel. The hot metal components at this time were: C: 4.5%, Si: 0.19%, Mn:
0.13%, P: 0.090%, S: 0.020%. After removing the desiliconized slag on the hot metal with a slag dragger, quick lime powder 19 kg / t and iron ore powder 24 kg /
The flux mixed with t was blown together with nitrogen gas from a lance immersed in the hot metal to remove phosphorus. During the dephosphorization treatment, oxygen gas was sprayed onto the hot metal from a water-cooled lance at 1.8 m ³ / t. In this process, Ca
F ₂ and Na ₂ O was not used at all.

In the mixed iron wheel that has been subjected to the above treatment, the phosphorus concentration after the dephosphorization treatment is P: about 0.041%,
In addition, the waste property was extremely poor, and slag was deposited on the bottom of the mixed iron wheel.

[0030]

As described above, according to the dephosphorizing agent for hot metal and molten steel according to the present invention, the added Na ₂ O
However, since it has the same effect of decreasing the melting point of CaO as CaF ₂ conventionally added and maintains the dephosphorizing effect of CaO, CaF ₂ is partially or entirely replaced with Na ₂ O and added. In recent years, the use of CaF ₂ has been reduced or eliminated in a direction where its use is being restricted due to concerns about work environment and concerns about harm to equipment, etc. It can be achieved without causing operational problems such as deterioration of sex. In addition, CaF in slag
_{2 By} reducing or eliminating the concentration, the reuse of slag after dephosphorization can be expected to be expanded.

The same effect as in the case of the above-mentioned dephosphorizing agent can be obtained by the desulfurizing agent for hot metal and molten steel according to the present invention.

[Brief description of the drawings]

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a graph showing the relationship between the melting point of CaO and the amounts of Na ₂ O and CaF ₂ added.

FIG. 2 is a graph showing the change over time in the dephosphorization ability of the flux according to the present invention and the flux according to the comparative example with each flux.

FIG. 3 is a graph showing the change over time of the desulfurization ability of each of the flux according to the present invention and the flux according to the comparative example.

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) 4K013 BA03 BA05 CA01 CA04 CA08 CA12 CA15 CB04 CB09 DA03 DA06 DA09 DA10 EA01 EA02 EA03 FA02 4K014 AA02 AA03 AB02 AB03 AB04 AB09 AC14 AC16 AC17 AD01 AD14 AD27

Claims (6)

[Claims] 1. A treatment agent mainly composed of quick lime is Na ₂ O.
A dephosphorizing agent for hot metal or molten steel, characterized by adding a compound containing: Wherein Na dephosphorization treatment agents molten iron-molten steel according to claim 1, wherein the silicate containing compound containing ₂ O is a Na ₂ O. 3. The dephosphorizing agent for hot metal and molten steel according to claim 2, wherein the silicate containing Na ₂ O contains 20% by mass or more of Na ₂ O. 4. The treatment agent mainly containing quicklime is CaF
4. The dephosphorizing agent for hot metal and molten steel according to any one of claims 1 to 3, wherein the agent does not contain ₂ . 5. A treating agent mainly containing quicklime, Na ₂
A desulfurizing treatment agent for hot metal and molten steel, wherein a compound containing Na ₂ O is added so that O is more than 6% by mass. 6. A compound containing Na ₂ O is a silicate containing Na ₂ O, and 20 wt% of Na ₂ O comprising the claims 5 desulfurization agent of molten iron-molten steel according to .