Description:DESCRIPTION:
Field of the invention:
[0001] The present disclosure generally relates to the technical field of calcium oxide (CaO) and hydrogen borate (H3BO3) fluxing agents for use in steel refining processes and, in specific, relates to a method for treating Si-Mn killed steels using CaO and H3BO3 fluxing agents to reduce synthetic slag consumption, resulting in cost savings.
Background of the invention:
[0002] Steel, the backbone of modern infrastructure and countless essential items, derives its strength and versatility from elements beyond iron alone. In steel raw form, iron comes bundled with an unwelcome guest sulfur. The sulfur element can wreak havoc on steel's properties, making it brittle, prone to corrosion, and difficult to work with. Steel desulfurization is the process that eliminates sulfur, thereby unlocking the true potential of this remarkable metal. In response to the increasing demand for ultra-clean steels, diverse types of ladle fluxes have been developed to aid in the desulfurization of steel.

[0003] Ladle fluxes are ideally introduced during the steel tapping into the ladle, which is then subjected to secondary metallurgical activities. These fluxes find extensive use in the treatment of Si-Killed steels in order to obtain a more advantageous CaO-Al2O3-SiO2 system than a CaO-MgO-SiO2 system. Depending on the application, many types of ladle fluxes are employed, such as calcium aluminate-based, calcium magnesium aluminate-based, calcium fluoride-based, and alumina-based. Among these, CaO-Al2O3-based ladle fluxes are commonly chosen due to their low melting point. However, these fluxes are costly, and a significant quantity of synthetic slag addition is required along with lime to accelerate desulfurization. If only synthetic slag is used as fluxing agent, available lime in slag will be low. This leads to a reduced sulfide capacity, presenting a challenge for efficient steel desulfurization.

[0004] In existing methodologies, while in the ladle, the molten steel can be subjected to additional refining processes (ladle refining processes). For instance, additional ladle fluxes may be added to the molten steel in order to further remove impurities that remained within the molten steel after being tapped from the furnace. The byproducts formed during the ladle refining process are generally referred to as ladle slags. After the completion of all refining activities, the ladle is transported to the continuous caster, where the molten metal is cast. The residual unwanted ladle slag is then discharged into the slag pot or emergency container. Generally, the chemical composition, as well as the physical properties, of the ladle slag makes it unsuitable for recycling into the steel refining process. Accordingly, the majority of ladle slags are discarded and transported to landfills for disposal. Most of the ladle slags contain high alumina and high CaO content, the recycling potential is low due to slag disintegration phenomena.

[0005] By addressing all the above mentioned problems, there is a need for a method that prepares low melting CaO based ladle flux containing B2O3, this method aims to treat Si-Killed Steels using CaO and H3BO3 fluxing agents. Additionally, there is a necessity fora method that reduces melting point of flux even by maintaining higher percentage of CaO in the ladle flux. Furthermore, there is also a need for a method that improves slag fluidity drastically to reduce synthetic slag addition. Moreover, there is also a need for a method that includes H3BO3 and CaO as fluxing agents for treating Si-Killed steels on an industrial scale. Additionally, there is also a need for a method that reduces synthetic slag addition, which result cost saving. Finally, there is also a need for a method that improves slag valorisation potential.
Objectives of the invention:
[0006] The primary objective of the present invention is to provide a method that prepares low melting CaO based ladle flux containing B2O3, thereby treating Si-Killed Steels with the using CaO and H3BO3 fluxing agents.

[0007] Another objective of the present invention is to provide a method that reduces melting point of the ladle slag while maintaining an elevated percentage of CaO.

[0008] The other objective of the present invention is to provide a method that significantly enhances slag fluidity, leading to a substantial reduction in the need for synthetic slag addition with improved desulfurization efficiency.

[0009] The otherobjective of the present invention is to provide a method that that includes H3BO3 and CaO as fluxing agents for treating Si-Mn Killed steels on an industrial scale.

[0010] Yet another objective of the present invention is to provide a methodthat minimizes the requirement of synthetic slag, thereby helping to reduce synthetic slag addition and achieve cost savings.

[0011] Further objective of the present invention is to provide a method that enhances the potential for Si-Mn killed slag valorisation.
Summary of the invention:
[0012] The present disclosure proposes a method of treating Si-Mn killed steels using CaO and H3BO3 fluxing agents. The following presents a simplified summary in order to provide a basic understanding of some aspects of the claimed subject matter. This summary is not an extensive overview. It is not intended to identify key/critical elements or to delineate the scope of the claimed subject matter. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is presented later.

[0013] In order to overcome the above deficiencies of the prior art, the present disclosure is to solve the technical problem to provide a method for treating Si-Mn killed steels using CaO and H3BO3 fluxing agents for reducing synthetic slag consumption, leading to cost savings.

[0014] According to one aspect, the invention provides a method of treating Si-Mn Killed steels using lime (CaO) and boric acid (H3BO3) as fluxing agents. At one step, steel is processed from a basic oxygen furnace (BOF) route, thereby taping steel into ladle of 150 tons capacity for secondary metallurgical operations. At one step, plurality Ferro alloys and one or more ladle fluxes are added, depending on the steel grade. At one step, the steel is processed at ladle furnace (LF) station for desulfurization and inclusion absorption, thereby homogenizing steel composition and maintaining steel temperature required for smooth casting.

[0015] At one step, the steel is deoxidized before casting by the adding one or more components to avoid evolution of gas during solidification. The method for reducing the melting point of LF slag and improving desulphurization efficiency.

[0016] In one embodiment, the ferro alloys include Fe-Si, Si-Mn, lime, and synthetic slag. The ladle fluxes, comprising lime and boron trioxide (B2O3), are introduced to significantly enhance slag fluidity. This leads to a notable reduction in synthetic slag addition, ultimately resulting in lowered steel production costs.

[0017] In one embodiment, the one or more components include silicon, manganese, and aluminium, but also sometimes vanadium, titanium, and zirconium. The method for preparing low melting flux comprises 70–80 weight percentage of lime, 3–8 weight percentage of B2O3, and 10–20 weight percentage of synthetic slag in varied proportions. The synthetic slag comprises 34–38 weight percentage of CaO, 41–45 weight percentage of Al2O3, 6–8 weight percentage of MgO, and 5 weight percentage of SiO2 as major constituents. The ladle flux comprises 60–80 weight percentage of CaO, 1 to 3 weight percentage of SiO2, 5 to 15 weight percentage of Al2O3, and 2 to 8 weight percentage of B2O3 as major constituents.

[0018] In one embodiment, the method for reducing flux melting point to 1100 to 1400 °C by addition of 3 to 8 weight percentage of B2O3 in slag containing 50–55 weight percentage of CaO, 8 to 12 weight percentage of MgO, 18 to22 weight percentage of SiO2, 10 to 15 weight percentage of Al2O3, and 1 to 2 weight percentage of FeO as major constituents. The method for improving Si-killed steel desulphurization efficiency by addition of 50 to 80 weight percentage of lime, 3 to 8 weight percentage of B2O3, and 10 to 40 weight percentage of synthetic slag.

[0019] In one embodiment, the method includes treating low carbon-Si-killed steels with 70 to 80 weight percentage of lime, 3 to 6 weight percentage of B2O3, and 10 to 20 weight percentage of synthetic slag to improve slag basicity and at the same time achieve low melting and fluid LF or Ladle slag. The method includes treating high-carbon Si-Mn killed steels with 50 to 60 weight percentage of lime, 3 to 8 weight percentage of B2O3, and 30 to 40 weight percentage of synthetic slag to improve slag basicity and at the same time achieve low melting and fluid LF slag. The melting temperature is determined through the ash fusion test, with the hemispherical temperature being regarded as the slag melting temperature.

[0019] Further, objects and advantages of the present invention will be apparent from a study of the following portion of the specification, the claims, and the attached drawings.
Detailed description of drawings:
[0020] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate an embodiment of the invention, and, together with the description, explain the principles of the invention.

[0021] FIG.1 illustrates a flow diagram of the view of a method for treating Si-Mn killed steels using CaO and H3BO3 fluxing agents, in accordance to an exemplary embodiment of the invention.

[0022] FIGs. 2A-2B illustrate screenshots of the analysis of an ash fusion tester results, in accordance to an exemplary embodiment of the invention.

[0023] FIG. 3 illustrates a graphical representation of the Effect of B2O3 in ladle or ladle furnace (LF) slag on melting temperature derived from lab scale experiments, in accordance to an exemplary embodiment of the invention.

[0024] FIG.4 illustrates a graphical representation comparing the effect of B2O3 addition on slag melting temperature of LF or Ladle slag. The data is obtained from lab-scale experiments and industrial trials across various steel grades of Si-killed steels, in accordance with an exemplary embodiment of the invention.

[0025] FIG. 5 illustrates a graphical representation of the variation in slag composition between LF-In and LF-Out after B2O3 addition, in accordance with an exemplary embodiment of the invention.

[0026] FIG. 6 illustrates a graphical representation of the Variation in LF out slag composition for regular heats and trial heats with B2O3 addition, in accordance to an exemplary embodiment of the invention.

[0027] FIGs. 7A-7B illustrate screenshots of the appearance of slag at LF entry and the appearance of ladle bottom after slag dumping with B2O3 addition.

[0028] FIG. 8 illustrates a graphical representation of the position of slag composition on the ternary diagram of CaO-Al2O3-SiO2 for high carbon grade, depicting trial heats with B2O3 addition and regular heats at 10 weight percentage of MgO.

[0029] FIG. 9 illustrates a flowchart for a method for treating Si-Mn Killed steels using lime (CaO) and boric acid (H3BO3) as fluxing agents, in accordance to an exemplary embodiment of the invention.
Detailed invention disclosure:
[0030] Various embodiments of the present invention will be described in reference to the accompanying drawings. Wherever possible, same or similar reference numerals are used in the drawings and the description to refer to the same or like parts or steps.

[0031] The present disclosure has been made with a view towards solving the problem with the prior art described above, and it is an object of the present invention to provide amethod for treating Si-Mn killed steels using CaO and H3BO3 fluxing agents for reducing synthetic slag consumption, which result cost saving.

[0032] According to one exemplary embodiment of the invention, FIG. 1 refers to a flow diagram 100 of the view of a method for treating Si-Mn killed steels using CaO and H3BO3 fluxing agents. At step 102, the steel processed from BOF route. At step 102, the processed steel is further taped into ladle of 150 Tons capacity for secondary metallurgical operations as shown in FIG. 1. At step 106, various Ferro alloys and ladle fluxes are added depending on steel grade during tapping the steel.

[0033] At step 108, the steel undergoes a thorough rinsing process to achieve homogenization in terms of both temperature and composition before being sent to the LF (ladle furnace). At step 110, the steel undergoes additional processing at the ladle furnace station. Thorough killing is employed to reduce the dissolved oxygen content, enhancing the surface quality. Additionally, the process includes desulfurization and inclusion absorption before the steel is sent to casting.

[0034] The LF station also helps in homogenizing steel composition and maintaining steel temperature required for smooth casting. The bath stirring is achieved by means of argon purging from the bottom. The Killed steel is steel that has completely deoxidized by the addition of de-oxidizers before casting such that there is practically no evolution of gas during solidification. The steel is fully deoxidised (killed) before casting by the addition usually of silicon, manganese and aluminium. Additionally, vanadium, titanium and other ferro alloys are sometimes included to meet specific grade requirements. At step 112, continuing the steel casting process.

[0035] In one embodiment herein, the B2O3 is an effective fluxing agent. The B2O3 additions may assist in improving slag fluidity. The small quantity of B2O3 may improve slag fluidity drastically and hence, the synthetic slag addition can be reduced. This helps in cost savings. The addition of B2O3 source solves the problem of crusty slag and helps in smooth arcing. The effect of B2O3 additions on CaO-MgO-SiO2-Al2O3 based slag was studied by many researchers.

[0036] The B2O3 addition assists in lowering the viscosity of slag which helps in eliminating the sticking of slag to lip or mouth of the ladle during refining. It was found that B2O3 can be used as a replacement to conventional CaF2. By substituting the CaF2 with B2O3, the melting temperature of the slag decreased remarkably. The temperature range for low viscosity is expanded and the stability of slag viscosity varying with temperature is improved. The slag could be controlled in a higher basicity range while still maintaining a good fluidity.

[0037] In one embodiment herein, the ladle furnace slag, however, is so basic that ß-C2S is formed during the post-metallurgical cooling process. The ß-C2S transforms upon cooling into ?-C2S and this transformation is accompanied with a considerable volume increase, leading to material disintegration. Thus, the valorisation of this slag as aggregate becomes a challenge. The small amount of B2O3 addition could significantly depress the crystallization during the cooling and therefore improves the valorisation potential.

[0038] Few researchers found that the number of Si–O and Al–O broken bonds increased in Al2O3–SiO2 melts with B2O3 addition, which decreases the crystallization temperature and benefits the glass formation. The B2O3 exhibits the ability to amalgamate with various oxides, forming eutectics with low melting points that subsequently decrease the overall melting point of the slag. This results in a reduction in slag viscosity. Additionally, the slag tends to undergo early melting, leading to improved slag fluidity, desulphurization kinetics, and enhanced dissolution of CaO and absorption of Al2O3. B2O3 addition may also help in reduction of synthetic slag usage.

[0039] First, the low melting temperature of B2O3, which is about 450°C, is favorable for the high melting temperature components such as CaO and Al2O3 fusing into slag, so the melting temperature of system is decreased. At the same time, the B2O3 may combine with various oxides of slag to form eutectics such as MgO.B2O3, (melting temperature 988°C), CaO.B2O3 (melting temperature 1100°C) and so on. The formation of eutectics is advantageous for reducing the melting temperature of the slag, as these eutectics have inherently low melting temperatures.

[0040] According to one exemplary embodiment of the invention, FIG. 2A-2B refer to screenshots of the analysis of an ash fusion tester 200 results. In order to estimate the effect of the B2O3 additions on melting temperature of LF slag, the melting experiments are carried out by mixing known quantity of B2O3 in LF slag in 3 to 8 weight percentage. The properties of H3BO3 used in experiments are given in the below Table 1. The composition of slag used for lab scale trials is given in the Table 2. The slag was re-melted in high temperature muffle furnace to homogenize the mix. The slag is subsequently analyzed for its melting temperature in an Ash Fusion testing equipment, as illustrated in FIG. 2A.

[0041] The Hemisphere method is followed to estimate slag melting temperature. The ash fusion equipment with heating rate of 8°C per minute is used to analyze slag melting property and the hemispherical temperature is considered as base for comparison. In this method slag sample of 14 mm size was prepared in the form of cone. The sample is then heated in reducing atmosphere to analyze the melting behavior. The temperature is recorded at four points, when the rounding off of sample tip is observed it is called as deformation temperature (DT), when the height of sample equals to width it is called softening temperature (ST).When height of sample is half the width it is called hemisphere temperature (HT).

[0042] Lastly when the slag fuses and flows, it is called flow temperature (FT) as shown in FIG. 2B. The temperature at which height of the sample reduces to half its width is considered as melting temperature. From lab scale experiments, examiner found that with 3 to 8 weight percentage of B2O3 addition, melting temperature of slag reduced from 1400 to 1110°C as shown in FIG. 3. The FIG 3 illustrates the graphical representation 300 of the Effect of B2O3 in slag on melting temperature from lab scale experiments.

[0043] Table 1: Properties of the H3BO3.
B2O3 (Wt %) H2O (Wt %) Density Melting Point Appearance Packing
56 44 1.435 g/cm3 170.9oC White crystals 10 kg bags

[0044] Table 2: Composition of slag used in lab scale experiments.
CaO MgO SiO2 Al2O3 FeO MnO TiO2 P2O5 S
48-55 8-12 16-18 8-11 1.0-1.5 0.5-1.0 0.25-0.5 0.025-0.40 0.5-0.8

[0045] In one embodiment herein, In Si-Mn killed steel making process; steel is deoxidized with Si and Mn. Conventionally around 1 to 1.5 ton of CaO-Al2O3 based synthetic slag is added as flux during taping steel into ladle of 150 tons capacity. In the present invention around 500 to 900 kg lime, 60 to 100 kg H3BO3and 0 to 300 kg of CaO-Al2O3 based synthetic slag are added during tapping steel into ladle as shown in FIG. 4. The H3BO3is packed in 10 kg bags for ease of addition. The composition of H3BO3, CaO- Al2O3based synthetic slag and lime is given in the Table 1, Table 3 and Table 4, respectively.

[0046] Table 3: Composition of CaO-Al2O3 based synthetic slag in weight percentage.
CaO MgO SiO2 Al2O3 FeO MnO S
34-38 6-8 5 max 41-45 <1 <1 <0.5

[0047] Table 4: Composition of lime in the weight percentage.
CaO SiO2 LOI
89-92 1-1.5 5-6

[0048] In one embodiment herein, trials are carried out in low carbon and high carbon Si-Mn killed steels. The average composition of steel is given in Table 5. The steel and slag samples are analysed before and after LF treatment to measure the desulphurization efficiency, sulphur partition ratio and melting temperature of slag. The melting temperature is estimated using the ash fusion tester where hemispherical temperature is considered as slag melting temperature.

[0049] Table 5: Composition of Si-Mn killed steels in the weight percentage.
Si-Mn killed steel C Mn P(max) S (max) Si Cr
Low carbon 0.12-0.23 0.30-1.50 0.045 0.045 0.4 max 0.05max
High Carbon 0.60-0.80 0.40-0.80 0.035 0.035 0.15-0.35 0.06-0.30

[0050] In one embodiment herein, the high carbon grades with 1.2 to 1.5 Tons of synthetic slag and 0-300 kg lime addition, the basicity of LF slag is in range of 1.2 to 2.5. With addition of 60to 100 kg H3BO3, lime addition was increased to 800 to 1000kg. The sulphide capacity of the slag increases with increase in CaO content. Therefore, industrial trials were carried out in both low carbon and high carbon Si-Killed steels to improve slag basicity and at the same time achieve low melting and fluid LF slag. 14 trials were carried out in low carbon grade and 6 trials in high carbon grade with different combination of lime, synthetic slag and H3BO3 additions as shown in the Table 6. Trials were carried out by varying B2O3 in flux from 3 to 8 weight percentage of the H3BO3 addition was carried out during taping steel into ladle.

[0051] Table 6: Flux mixtures are used in industrial trials.
Trail Grade (BOF) Taping + LF additions (kg) Wt % B2O3 in flux Basicity of LF exit slag Treatment Temp. at LF(oC) Treatment Time at LF (Minutes) Desulphurisation Efficiency (%)
Lime Synthetic slag H3BO3
1 Low Carbon 800 200 60 3.10 3.23 1598 41 53
2 550 500 60 3.00 2.60 1540 6 7
3 1350 310 80 2.57 3.02 1586 57 83
4 880 200 80 3.86 3.33 1588 60 42
5 700 300 80 4.14 2.75 1588 49 45
6 700 400 80 3.79 2.77 1579 25 50
7 700 400 80 3.79 2.80 1587 27 33
8 1100 0 100 4.60 3.11 1550 25 10
9 1000 0 100 5.09 3.12 1560 25 50
10 900 0 100 5.60 3.05 1576 26 92
11 990 0 100 5.13 3.00 1565 15 14
12 1000 0 100 5.09 2.62 1579 25 35
13 1776 0 100 2.98 3.76 1555 25 85
14 1174 300 100 3.55 2.62 1560 11 16
15 High Carbon 530 820 100 3.86 2.16 1536 62 45
16 580 660 120 4.64 2.10 1538 9 9
17 400 479 140 7.69 2.32 1545 50 20
18 605 435 150 7.05 2.05 1547 46 32
19 500 300 120 7.3 2.26 1538 90 12
20 840 520 120 4.52 2.66 1537 25 12

[0052] In one exemplary embodiment herein, the industrial trials are conducted by incorporating varying proportions of boric acid, lime, and synthetic slag, depending on the steel grade. The slag samples are collected at different stages of refining and analysed. From the industrial trials it was observed that melting point of LF slag decreased with increase in the weight percentage of the B2O3 as shown in the FIG. 4. The FIG 4 illustrates the graphical representation 400 of the comparison for Effect of B2O3 addition on slag melting temperature for LF slag from lab scale and industrial trials. There is a variation in the melting temperature of slag observed between lab-scale experiments and industrial trials, owing to the low recovery of B2O3 and the variability in amount of carryover and also total slag.

[0053] The effect of B2O3addition on ladle condition is checked. The slag did not stick to the ladle and there was no skull formation. The variation in slag composition before and after LF treatment is compared as shown in FIG. 5. The FIG 5 illustrates the graphical representation of comparison for Effect of B2O3 addition on slag melting temperature for LF slag from lab scale and industrial trials. The MgO saturation is in par with regular heats as shown in the FIG. 6. The FIG 6 illustrates graphical representation of the Variation in slag composition for trial heats with H3BO3 addition. The fluid LF slag is observed in all heats and slag did not stick to the ladle bottom as shown in FIG. 7A and FIG. 7B. The FIG 7A illustrates a screenshot of the appearance of slag at LF entry.

[0054] The FIG. 7B illustrates a screenshot of the appearance of ladle bottom after slag dumping. The ternary plot as shown in the FIG. 8 the graphical representation of variation in slag composition in high carbon grade for trial heats and regular heats at 10 weight percentage of MgO. From the ternary plot, by addition of B2O3 and CaO the composition of LF exit slag in high carbon grade shifted towards lime rich region which is beneficial for desulphurization .The basicity of LF exit slag increased compared to regular hats treated with synthetic slag. The basicity range increased from 1.8 to 3.0 to 2.5to 4. As B2O3 reduces the melting point of slag, this improves lime dissolution and hence slag can be maintained in higher basicity range. This in turn helps in improving desulphurization capability of slag.

[0055] According to another exemplary embodiment of the invention, FIG. 9 refers to a flowchart 900 of a method for treating Si-Mn Killed steels using lime (CaO) and boric acid (H3BO3) as fluxing agents. At step 902, the steel is processed from a basic oxygen furnace (BOF) route, thereby taping steel into ladle of 150 tons capacity for secondary metallurgical operations. At step 904, the plurality Ferro alloys and one or more ladle fluxes are added based on the steel grade. At step 906, the steel is processed at ladle furnace (LF) station for desulfurization and inclusion absorption, thereby homogenizing steel composition and maintaining steel temperature required for smooth casting.

[0056] At step 908, the steel is deoxidized before casting by the adding one or more components to avoid evolution of gas during solidification. The method for reducing the melting point of LF slag and improving desulphurization efficiency.

[0057] In one embodiment herein, the ferro alloys include Fe-Si, SI-Mn, lime, and synthetic slag. The one or more ladle fluxes include lime and boron trioxide (B2O3) to improve slag fluidity drastically, thereby reducing synthetic slag addition, which results in a reduction in steel production costs. The one or more ladle fluxes include lime and boron trioxide (B2O3) to improve slag fluidity drastically, thereby reducing synthetic slag addition, which results in a reduction in steel production costs.

[0058] In one embodiment herein, the one or more components include silicon, manganese, and aluminium, but also sometimes vanadium, titanium, and zirconium. The method for preparing low melting flux comprises 70 to 80 weight percentage of lime, 3–8 weight percentage of B2O3, and 10to 20 weight percentage of synthetic slag in varied proportions. The synthetic slag comprises 34 to 38 weight percentage of CaO, 41to 45 weight percentage of Al2O3, 6to 8 weight percentage of MgO, and 5 weight percentage of SiO2 as major constituents. The ladle flux comprises 60to 80 weight percentage of CaO, 1 to 3 weight percentage of SiO2, 5 to 15 weight percentage of Al2O3, and 2 to 8 weight percentage of B2O3 as major constituents.

[0059] In one embodiment herein, the method for reducing flux melting point to 1100 to 1400 °C by addition of 3 to 8 weight percentage of B2O3 in slag containing 50–55 weight percentage of CaO, 10 to 12 weight percentage of MgO, 18 to22 weight percentage of SiO2, 10 to 15 weight percentage of Al2O3, and 1 to 2 weight percentage of FeO as major constituents. The method for improving Si-killed steel desulphurization efficiency by addition of 50 to 80 weight percentage of lime, 3 to 8 weight percentage of B2O3, and 10 to 40 weight percentage of synthetic slag.

[0060] In one embodiment herein, the method includes treating low carbon-Si-killed steels with 70 to 80 weight percentage of lime, 3 to 6 weight percentage of B2O3, and 10 to 20 weight percentage of synthetic slag to improve slag basicity and at the same time achieve low melting and fluid LF slag. The method includes treating high-carbon Si-killed steels with 50 to 60 weight percentage of lime, 3 to 8 weight percentage of B2O3, and 30 to 40 weight percentage of synthetic slag to improve slag basicity and at the same time achieve low melting and fluid LF slag. The melting temperature is estimated using the ash fusion test, where hemispherical temperature is considered the slag melting temperature.

[0061] Numerous advantages of the present disclosure may be apparent from the discussion above. In accordance with the present disclosure a method of treating Si-Mn killed steels using CaO and H3BO3 fluxing agents is disclosed. The proposed invention provides the method that prepares low melting CaO based ladle flux containing B2O3, thereby treating Si-Killed Steels with the using CaO and H3BO3 fluxing agents. The method that reduces melting point of flux even by maintaining higher percentage of CaO in the ladle flux. The method that improves slag fluidity drastically to reduce synthetic slag addition.

[0062] The proposed invention provides the method that reduces synthetic slag addition, which result cost saving. The method that improves slag valorisation potential. The method that that includes H3BO3 and CaO as fluxing agents for treating Si-Killed steels at industrial scale.

[0063] It will readily be apparent that numerous modifications and alterations can be made to the processes described in the foregoing examples without departing from the principles underlying the invention, and all such modifications and alterations are intended to be embraced by this application.
, Claims:CLAIMS:
We Claim:
1. A method for treating Si-Mn Killed steels using lime (CaO) and boric acid (H3BO3) as fluxing agents, comprising:
processing steel from a basic oxygen furnace (BOF) route, thereby taping steel into ladle of 150 tons capacity for secondary metallurgical operations;
adding plurality Ferro alloys and one or more ladle fluxes based on the steel grade;
processing the steel at ladle furnace (LF) station for desulfurization and inclusion absorption, thereby homogenizing steel composition and maintaining steel temperature required for smooth casting; and
deoxidizing the steel before casting by the adding one or more components to avoid evolution of gas during solidification,
whereby, the method for reducing the melting point of LF slag enhances the dissolution of lime, thereby improving desulphurization efficiency.
2. The method as claimed in claim 1, wherein the ferro alloys include Fe-Si, SI-Mn, lime, ferro alloys and synthetic slag.
3. The method as claimed in claim 1, wherein the one or more ladle fluxes include lime and boron trioxide (B2O3) to improve slag fluidity drastically, thereby reducing synthetic slag addition, which results in a reduction in steel production costs.
4. The method as claimed in claim 1, wherein one or more components include silicon, manganese, and aluminium, but also sometimes vanadium, and titanium.
5. A method as claimed in claim 1, wherein
the method for preparing low melting flux comprises 70 to 80 weight percentage of lime, 3 to 8 weight percentage of B2O3, and 10 to 20 weight percentage of synthetic slag in varied proportions,
the synthetic slag comprises 34 to 38 weight percentage of CaO, 41 to 45 weight percentage of Al2O3, 6 to 8 weight percentage of MgO, and 1to5 weight percentage of SiO2 as major constituents, and the ladle flux comprises 60 to 80 weight percentage of CaO, 1 to 3 weight percentage of SiO2, 5 to 15 weight percentage of Al2O3, and 2 to 8 weight percentage of B2O3 as major constituents.
6. The method as claimed in claim 1, wherein the method for reducing flux melting point to 1100–1400 °C by addition of 3 to 8 weight percentage of B2O3 in slag containing 50 to 55 weight percentage of CaO, 10 to 12 weight percentage of MgO, 18 to 22 weight percentage of SiO2, 10 to 15 weight percentage of Al2O3, and 1 to 2 weight percentage of FeO as major constituents.
7. The method as claimed in claim 1, wherein the method for improving Si-killed steel desulphurization efficiency by addition of 50 to 80 weight percentage of lime, 3 to 8 weight percentage of B2O3, and 10 to 40 weight percentage of synthetic slag.
8. The method as claimed in claim 1, wherein the method includes treating low carbon-Si-killed steels with 70 to 80 weight percentage of lime, 3 to 6 weight percentage of B2O3, and 10 to 20 weight percentage of synthetic slag to improve slag basicity and at the same time achieve low melting and fluid LF slag.
9. The method as claimed in claim 1, wherein the method includes treating high-carbon Si-killed steels with 50 to 60 weight percentage of lime, 3 to 8 weight percentage of B2O3, and 30 to 40 weight percentage of synthetic slag to improve slag basicity and at the same time achieve low melting and fluid LF slag.
10. The method as claimed in claim 1, wherein the melting temperature is estimated using an ash fusion test, where hemispherical temperature is considered the slag melting temperature.