CN108642239B - Method for alloying molten steel silicon and treating calcium by using metal-containing calcium-silicon-iron alloy - Google Patents
Method for alloying molten steel silicon and treating calcium by using metal-containing calcium-silicon-iron alloy Download PDFInfo
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- CN108642239B CN108642239B CN201810454209.3A CN201810454209A CN108642239B CN 108642239 B CN108642239 B CN 108642239B CN 201810454209 A CN201810454209 A CN 201810454209A CN 108642239 B CN108642239 B CN 108642239B
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/0006—Adding metallic additives
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/06—Deoxidising, e.g. killing
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/064—Dephosphorising; Desulfurising
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/072—Treatment with gases
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- Engineering & Computer Science (AREA)
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- Treatment Of Steel In Its Molten State (AREA)
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Abstract
A method for alloying molten steel silicon and treating calcium by using a ferrosilicon alloy containing metal calcium belongs to the field of ferrous metallurgy refining. During the tapping process after the smelting of the converter, partial silicon alloying is not carried out or is carried out, simultaneously molten steel aluminum deoxidation treatment and slag pre-refining are carried out, and the aluminum content is controlled according to the upper limit of the steel grade requirement. And after secondary refining, adding ferrosilicon alloy containing metal calcium into the molten steel for silicon alloying and calcium treatment, then blowing argon at a larger flow rate and stirring for 1-3 minutes to promote the alloy to melt, and then blowing argon at a low flow rate and stirring to homogenize the components of the molten steel and promote the modification and floating of inclusions. The invention utilizes the metallic calcium contained in the ferrosilicon alloy, and simultaneously realizes the aims of silicon alloying and calcium treatment of the molten steel by adjusting the time of silicon alloying, reduces or even cancels the conventional calcium feeding line operation, and reduces the production cost; meanwhile, the problem of molten steel splashing caused by calcium feeding lines is avoided, oxygen and nitrogen increasing of the molten steel is reduced, the operation stability and the calcium yield are improved, and the cleanliness of the molten steel is further improved.
Description
Technical Field
The invention relates to a method for simultaneously carrying out molten steel silicon alloying and calcium treatment by utilizing a ferrosilicon alloy containing metal calcium, belonging to the field of ferrous metallurgy refining.
Background
In the production process of the aluminum deoxidized steel, a calcium treatment process is widely adopted to prevent the blockage of a submerged nozzle in the casting process, and in addition, the calcium treatment is also widely applied to the modification of MnS in steel grades such as pipeline steel and the like to avoid the formation of hydrogen-induced cracks in the service process. In steel enterprises, calcium treatment is mainly implemented by feeding various calcium-containing cored wires including pure calcium wires, silico-calcium wires, aluminum-calcium wires and the like into molten steel at present. In addition to the increase of cost, the calcium treatment mode is easy to generate molten steel splashing when calcium wires are fed due to high vapor pressure of calcium, secondary oxidation of the molten steel is caused, the calcium yield is low, and a large amount of non-metallic inclusions can be formed. Silicon is an element for increasing the strength and hardness of steel, and different steel grades have certain requirements on the silicon content. In steel production, ferrosilicon is generally added to steel during tapping in a converter to silicon alloy the molten steel. Ferrosilicon is produced by carbothermic reduction, and a certain amount of metallic calcium is present in the ferrosilicon due to the content of CaO in silica. Because the oxygen content of molten steel is high in the tapping process of the converter, calcium in the ferrosilicon is oxidized, and the waste of metal calcium is caused.
The invention provides a method for fully utilizing metal calcium contained in ferrosilicon to replace calcium wires, simultaneously realizing silicon alloying and calcium treatment of molten steel, reducing production cost, improving calcium yield and improving molten steel cleanliness.
Disclosure of Invention
The invention aims to provide a method for simultaneously carrying out molten steel silicon alloying and calcium treatment by utilizing ferrosilicon containing metal calcium. The method utilizes the calcium metal contained in the ferrosilicon alloy to replace calcium wires, and simultaneously realizes silicon alloying and calcium treatment of the molten steel, thereby not only reducing the production cost, but also improving the yield of calcium and improving the cleanliness of the molten steel.
In order to achieve the purpose, the invention adopts the technical scheme that: during the tapping process after the smelting of the converter, partial silicon alloying is not carried out or is carried out, simultaneously, the slag pre-refining and the aluminum deoxidation treatment are carried out, the aluminum content is controlled according to the upper limit of the steel grade requirement, and the aluminum supplement in the secondary refining process is avoided. And after secondary refining, adding ferrosilicon containing metal calcium into the molten steel for silicon alloying and calcium treatment, then blowing argon at a larger flow rate and stirring for 1-3 minutes to promote the alloy to melt, and then blowing argon at a low flow rate and stirring to homogenize the components of the molten steel and promote inclusions to float.
A method for carrying out silicon alloying and calcium treatment on molten steel by utilizing ferrosilicon containing metallic calcium is characterized in that the ferrosilicon contains metallic calcium; the processing steps are as follows:
(1) calculating the tapping process of the converter and the addition of the refined ferrosilicon according to the metallic calcium content of the ferrosilicon alloy and the target silicon content and calcium content of the molten steel;
(2) adding slag for pre-refining in the tapping process after smelting in a converter, and simultaneously carrying out molten steel aluminum deoxidation treatment to avoid adding aluminum in the secondary refining process;
(3) according to the calculation in the step (1), no or partial silicon alloying is carried out in the converter tapping process;
(4) after the secondary refining is finished, adding ferrosilicon containing metallic calcium into molten steel for silicon alloying and calcium treatment, and then stirring by blowing argon at a large flow rate to promote the melting of the alloy;
(5) and finally, argon blowing and stirring are carried out at a low flow rate so as to homogenize the components of the molten steel and promote the floating of inclusions.
Further, the grain size of the ferrosilicon alloy in the step (1) is less than 50mm, the ferrosilicon alloy contains more than 0.1 percent of metallic calcium, and the metallic calcium in the same batch of alloy is ensured to be uniform.
Further, aluminum is added for deoxidation in the step (2), and the aluminum content is controlled according to the upper limit of the steel grade requirement.
Further, after the secondary refining in the step (4) is finished, the ferrosilicon containing the metal calcium is added, and then argon is blown and stirred for 1-3 minutes by adopting a large flow (the flow is referenced to 300-700NL/min to achieve the aim of rolling the slag surface) so as to promote the alloy to be melted.
Further, the low-flow argon-blowing stirring (flow rate is referred to 100-250NL/min to reach the condition that the slag surface slightly fluctuates and the molten steel is not exposed) in the step (5) is more than 10 min.
The method has the innovation point that the metallic calcium contained in the ferrosilicon alloy is fully utilized, and the aims of silicon alloying and calcium treatment of the molten steel are simultaneously realized by adjusting the time of silicon alloying. The method does not increase the addition of the silicon alloy on one hand, and reduces or even cancels the conventional calcium feeding operation on the other hand, thereby obviously reducing the production cost; meanwhile, the problem of molten steel splashing caused by calcium feeding lines is avoided, oxygen and nitrogen increase of the molten steel is reduced, the operation stability and the calcium yield are improved, and the cleanliness of the molten steel is improved.
Drawings
FIG. 1 shows the distribution of the components of inclusions in steel when the LF refining desulfurization is finished and no ferrosilicon alloy is added in the embodiment of the present invention;
FIG. 2 shows typical morphology of inclusions in steel when no ferrosilicon alloy is added after LF refining desulfurization in the embodiment of the present invention;
FIG. 3 shows the distribution of the components of inclusions in steel after the ferrosilicon alloy is added and argon is blown at a high flow rate for stirring in the embodiment of the invention;
FIG. 4 is a typical morphology of inclusions in steel after the ferrosilicon alloy is added and argon is blown at a large flow rate for stirring in the embodiment of the invention;
FIG. 5 is a graph showing the distribution of the components of inclusions in steel at the end of soft blowing in the example of the present invention;
FIG. 6 shows typical morphology of inclusions in steel at the end of soft blowing in an embodiment of the present invention.
Detailed Description
In order to make the technical solution and advantages of the present invention more clear, the following detailed description is given with reference to specific embodiments.
The specific embodiment is as follows:
taking a 300t converter, LF refining and continuous casting process for producing the pipeline steel as an example, according to thermodynamic calculation, the target calcium content in the molten steel after the pipeline steel is subjected to calcium treatment is 10-20 ppm. The ferrosilicon used in the production contains 0.38 percent of metallic calcium and has the granularity of about 50 mm. According to the target components of silicon and calcium in the pipeline steel, the silicon iron addition amounts distributed in the converter tapping process and the LF refining process under the condition that the total silicon iron usage amount is not changed are calculated to be 360kg and 420kg respectively.
Slag is added for pre-refining in the converter tapping process, and the content of acid-soluble aluminum in the molten steel is controlled to be 0.03-0.04% by adding aluminum particles into the molten steel and the like. Meanwhile, 360kg of the ferrosilicon alloy is added in the tapping process of the converter. And after normal temperature rise, slag melting and desulfurization operations of LF refining, 420kg of the ferrosilicon alloy is added. After the ferrosilicon alloy is added, the mixture is stirred for 3min by adopting argon with larger flow so as to promote the melting and the uniformity of the alloy. And then, carrying out soft blowing on the molten steel for 12min by adopting low argon flow so as to promote the transformation and removal of the inclusions. And after the soft blowing is finished, the molten steel is sent to a continuous casting platform for casting.
And respectively extracting molten steel samples at the end of LF refining desulfurization (before adding the ferrosilicon alloy), at the beginning of soft blowing (after finishing adding the ferrosilicon alloy and blowing argon at a high flow rate for stirring) and at the end of soft blowing. And detecting to obtain that the calcium content in the molten steel at the end of soft blowing is 18ppm and reaches an expected target value. Meanwhile, the total oxygen content in the steel is 17ppm and the nitrogen content is 22ppm at the end of soft blowing, so that high cleanliness is achieved. The non-metallic inclusions in the steel are detected, the composition distribution of the inclusions in the steel at the end of LF refining desulphurization is shown in figure 1, the morphology of typical inclusions is shown in figure 2, and the inclusions are mainly magnesium aluminate spinel with irregular shapes. After the ferrosilicon alloy is added and argon is blown at a large flow rate for stirring, the component distribution of the inclusions in the steel is shown in figure 3, the morphology of typical inclusions is shown in figure 4, most of the inclusions are converted into spherical calcium aluminate, but the components of part of the inclusions are not uniform and the size is large. The composition distribution of the inclusions in the steel at the end of the soft blowing is shown in fig. 5 and the morphology of the typical inclusions is shown in fig. 6, where the inclusions have been substantially transformed into more uniformly composed spherical calcium aluminates and further reduced in size.
The results show that the invention can well realize the aims of silicon alloying and calcium treatment of the molten steel at the same time under the conditions of not increasing the usage amount of the ferrosilicon alloy and not feeding calcium wires, obviously reduce the cost, is easy to operate and simultaneously ensure high cleanliness of the molten steel.
Claims (3)
1. A method for carrying out silicon alloying and calcium treatment on molten steel by utilizing ferrosilicon containing metallic calcium is characterized in that the ferrosilicon contains metallic calcium; the processing steps are as follows:
(1) calculating the tapping process of the converter and the addition of the refined ferrosilicon according to the metallic calcium content of the ferrosilicon alloy and the target silicon content and calcium content of the molten steel;
(2) adding slag for pre-refining in the tapping process after smelting in a converter, and simultaneously carrying out molten steel aluminum deoxidation treatment to avoid adding aluminum in the secondary refining process;
(3) according to the calculation in the step (1), no or partial silicon alloying is carried out in the converter tapping process;
(4) after the secondary refining is finished, adding ferrosilicon containing metallic calcium into molten steel for silicon alloying and calcium treatment, and then stirring by blowing argon at a large flow rate to promote the melting of the alloy;
(5) finally, argon blowing and stirring are carried out at low flow rate so as to homogenize the components of the molten steel and promote the floating of inclusions;
the ferrosilicon alloy in the step (1) has the granularity of less than 50mm, contains more than 0.1 percent of metallic calcium, and ensures that the metallic calcium in the same batch of alloy is uniform;
after the secondary refining in the step (4) is finished, the ferrosilicon alloy containing the metal calcium is added, then the large flow rate is adopted, the flow rate is 300-700NL/min, so that the slag surface is rolled, and argon is blown for stirring for 1-3 minutes to promote the alloy to be melted.
2. The method for silicon alloying and calcium treatment of molten steel using sendust as claimed in claim 1 wherein: and (3) aluminum is added for deoxidation in the step (2), and the aluminum content is controlled according to the upper limit of the steel grade requirement.
3. The method for silicon alloying and calcium treatment of molten steel using sendust as claimed in claim 1 wherein: and (5) the argon blowing stirring is performed at a low flow rate of 100 plus 250NL/min, so that the slag surface is slightly fluctuated without exposing molten steel, and the soft blowing is performed for more than 10 min.
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| CN112921147B (en) * | 2021-01-21 | 2022-02-22 | 北京科技大学 | CaS precipitation inhibition method in heat treatment process of aluminum deoxidized calcium treated steel |
| CN114574659A (en) * | 2022-02-22 | 2022-06-03 | 湖南华菱涟源钢铁有限公司 | Smelting method for controlling B-type inclusions in pipeline steel and pipeline steel |
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| CN102134630A (en) * | 2011-04-07 | 2011-07-27 | 河北钢铁股份有限公司唐山分公司 | Calcium treatment method for refining molten steel under vacuum |
| CN105349875B (en) * | 2015-10-27 | 2018-02-27 | 北京科技大学 | Possesses low-cost silicon ferroalloy of calcium treatment effect and preparation method thereof |
| CN105734393A (en) * | 2016-04-15 | 2016-07-06 | 唐山钢铁集团有限责任公司 | Production method for non-oriented electrical steel |
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