Method for judging alkalinity of slag according to color of slag

Abstract

The method comprises the following steps: S1, in order to improve the purity of molten steel and reduce the C content of the molten steel, carrying out VOD (Vacuum Oxygen Decarburization) treatment on the molten steel; s2, silica and dolomite are added into an LF furnace to make low-alkalinity slag, the slag alkalinity R is 1.6 according to the VOD slag alkalinity and the adding amount of the silica and the dolomite during LF furnace slagging, and the calculation formula of the LF alkalinity is R = (dolomite adding amount * 0.55 + VOD lime adding amount) / VOD station entering Si% * VOD molten steel amount t * 10) * 2.14 + ((reduced silicon iron adding amount-(VOD molten steel amount t * VOD station exiting Si * 10) / 0.75) * 0.75 * 2.14)) + silica adding amount * 0.98), wherein 2.14 is the conversion coefficient of Si and SiO2, 0.75 is the content of Si in ferrosilicon, and 0.55 is the proportion of CaO in dolomite.

Description

Technical Field

[0001] The invention relates to the technical field of stainless steel smelting, and in particular to a method for determining slag basicity according to slag color. Background Art

[0002] High-basicity slag is beneficial to deoxidation, desulfurization, and purity of molten steel, while low-basicity slag helps to improve the plasticity of inclusions. As the slag basicity decreases, inclusions evolve from the CaO-SiO2-Al2O3 system to the SiO2-Al2O3-MnO system with good plasticity. Low-basicity slag is a necessary condition for the plasticization of inclusions. By adopting the "two-slag making method" smelting process, high-basicity slag is made for desulfurization and deoxidation during the AOD desulfurization period, deep decarburization and deoxidation are carried out in VOD, and LF refining is used to make low-basicity slag for plastic steel inclusions, and finally the excellent molten steel cleanliness and inclusion plasticization of 316L are achieved. However, when making low-basicity slag in the LF furnace, the theoretical calculation of basicity needs to be combined with the actual test composition. Too low basicity will cause ladle erosion and carbon increase, and too high basicity is not conducive to the plasticization of inclusions. Therefore, a reasonable operation method is needed to make an effective judgment on the slag basicity to guide production. Summary of the invention

[0003] In view of the above technical problems, the present invention provides a method for determining slag basicity according to slag color.

[0004] In order to achieve the above object, the technical solution of the present invention is as follows: A method for determining slag basicity according to slag color comprises the following steps: S1. To improve the purity of molten steel and reduce the C content of molten steel, VOD treatment is performed on the molten steel; S2. Add silica and dolomite to the LF furnace to make low basicity slag. According to the VOD slag basicity, the amount of silica and dolomite added during LF furnace slag making is based on the slag basicity R=1.6. The LF basicity calculation formula is: R=(dolomite addition×0.55+VOD lime addition) / VOD inlet Si%×VOD molten steel volume t×10)×2.14+((reduced ferrosilicon addition-(VOD molten steel volume t×VOD outlet Si×10) / 0.75)×0.75×2.14))+silica addition×0.98), where 2.14 is the conversion coefficient of Si and SiO2, 0.75 is the Si content in ferrosilicon, 0.55 is the proportion of CaO in dolomite, and 0.98 is the proportion of SiO2 in silica; After the slag is chemically processed, take a slag sample. If the slag sample is black or grayish black, the actual alkalinity of the slag should be below 1.6, and no silica needs to be added. If the slag sample is white or grayish white, the slag alkalinity is too high, and 50-200 kg of silica needs to be added for slag adjustment.

[0005] Wherein, in the step S1, in the VOD treatment, the amount of lime added is controlled according to the slag basicity R=1.8, the amount of reduced ferrosilicon added=1.25×(total oxygen consumption in smelting-oxygen consumption of carbon oxide-oxygen consumption of silicon oxide) / silicon content of ferrosilicon+steel output×alloyed silicon content / silicon content of ferrosilicon, where 1.25 means that 1 standard cubic meter of oxygen requires 1.25 kg of Si, and the Si content of molten steel tapping is controlled at 0.38-0.5%; In VOD treatment, the calculation formula of slag basicity is: R=(amount of lime added Kg) / ((VOD inlet Si%×VOD molten steel volume t×10) ×2.14+((amount of reduced ferrosilicon added-(VOD molten steel volume t×VOD outlet Si×10) / 0.75) ×0.75×2.14)), where 2.14 is the conversion coefficient of Si and SiO2, and 0.75 is the Si content in ferrosilicon.

[0006] The beneficial effects of the present invention are: 1. The present invention can realize the plasticization of inclusions in 316L steel grade low-basicity slag to obtain good surface quality and mechanical properties. According to the amount of VOD lime added, incoming Si, molten steel, reduced ferrosilicon added, and tapped silicon, the VOD slag basicity is calculated. When LF furnace slag is made, the amount of silica added is added according to the slag basicity R=1.6. After the slag is well slaged, the slag sample is taken. If the slag sample is black or grayish black in color, the actual slag basicity should be below 1.6, and no more silica is needed. If the slag sample is white or grayish white in color, the slag basicity is too high, and 50-200Kg of silica needs to be added for slag adjustment. This method uses the sticky slag operation to judge the slag basicity by the color of the slag after it is discharged from the furnace, and guides the workers to operate online. It is simple and easy to operate and has strong guidance.

[0007] 2. The present invention uses slag sticking operation, and the personnel on duty judge the slag basicity according to the slag color, which is simple, easy to operate and highly instructive.

[0008] 3. The present invention can achieve plasticization of inclusions in 316L steel grade low basicity slag by producing low basicity slag, so as to obtain good surface quality and mechanical properties. DETAILED DESCRIPTION

[0009] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with specific embodiments. It should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present invention. In addition, in the following description, the description of known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0010] Example 1 In the first step, the steel produced from the AOD converter with a composition of C0.211%, Si0.105%, Mn0.858%, Ni13.52%, Cr17.43%, P0.027%, and S0.002% is subjected to VOD treatment.

[0011] 1.1 After the oxidation stage, the carbon is removed to 0.0095%. The oxygen blowing amount in the oxidation stage is 558Nm 3 .

[0012] 1.2 The boiling time of VCD stage is 14min.

[0013] 1.3 In the reduction stage, the amount of lime added is 1803 kg, the amount of fluorite added is 650 kg, the amount of reduced ferrosilicon added is 937 kg, the amount of low-carbon ferromanganese added is 594 kg, and the binary basicity of the reduced slag is 1.8.

[0014] 1.4 The steel composition of VOD is C0.0099%, Si0.399%, Mn1.338%, Ni13.478%, Cr17.248%, P0.027%, S0.0012%, and Al0.005%.

[0015] In the second step, silica and dolomite are added to the LF furnace to make low basicity slag.

[0016] 2.1 According to the VOD lime addition of 1803 kg, incoming Si of 0.105%, molten steel of 103.7 t, reduced ferrosilicon addition of 937 kg, and outgoing silicon of 0.399%, the binary basicity of VOD slag R is calculated to be 2.12.

[0017] 2.2 When LF furnace slag is made, 600Kg silica and 500Kg dolomite are added, and the theoretical LF slag basicity R=1.45.

[0018] 2.3 After the slag is oxidized, the slag sample is taken. It can be seen that the slag sample is black in color, indicating that the slag basicity should be below 1.6, and no silica needs to be added. At the same time, the LF alloying sampling composition is: C0.0123%, Si0.516%, Mn1.427%, Ni13.508%, Cr17.332%, P0.0269%, S0.0014%, Al0.0043%, which meets the exit requirements.

[0019] Example 2 In the first step, the steel produced from the AOD converter with a composition of C0.237%, Si0.085%, Mn0.796%, Ni13.502%, Cr17.448%, P0.028%, and S0.0013% is subjected to VOD treatment.

[0020] 1.1 After the oxidation stage, the carbon is removed to 0.01%. The oxygen blowing amount in the oxidation stage is 630Nm3 .

[0021] 1.2 The boiling time in the VCD stage is 15 minutes.

[0022] 1.3 In the reduction stage, the amount of lime added is 1900Kg, the amount of fluorite added is 700Kg, the amount of reduced ferrosilicon added is 970Kg, the amount of low-carbon ferromanganese added is 660Kg, and the binary basicity of the reduced slag is 1.8.

[0023] 1.4 The steel composition of VOD is C0.0143%, Si0.498%, Mn1.343%, Ni13.372%, Cr17.226%, P0.027%, S0.0008%, and Al0.0062%.

[0024] In the second step, silica and dolomite are added to the LF furnace to make low basicity slag.

[0025] 2.1 According to the VOD lime addition of 1900 kg, incoming Si of 0.085%, molten steel of 103.t, reduced ferrosilicon addition of 970 kg, and outgoing silicon of 0.498%, the binary basicity of VOD slag R is calculated to be 2.96.

[0026] 2.2 900Kg silica and 500Kg dolomite were added during LF furnace slag making, and the theoretical LF slag basicity R=1.43.

[0027] 2.3 After the slag is oxidized, the slag sample is taken. It can be seen that the slag sample is gray in color, indicating that the slag basicity should be below 1.6, and no silica needs to be added. At the same time, the LF alloying sampling composition is: C0.0179%, Si0.533%, Mn1.404%, Ni13.485%, Cr17.275%, P0.0274%, S0.0013%, Al0.006%, which meets the exit requirements.

[0028] Example 3 In the first step, the steel produced from the AOD converter with a composition of C0.232%, Si0.117%, Mn0.806%, Ni13.434%, Cr17.353%, P0.034%, and S0.0018% is subjected to VOD treatment.

[0029] 1.1 After the oxidation stage, the carbon is removed to 0.0097%. The oxygen blowing amount in the oxidation stage is 599Nm 3 .

[0030] 1.2 The boiling time of VCD stage is 14min.

[0031] 1.3 In the reduction stage, the amount of lime added is 1900Kg, the amount of fluorite added is 650Kg, the amount of reduced ferrosilicon added is 940Kg, the amount of low-carbon ferromanganese added is 631Kg, and the binary basicity of the reduced slag is 1.8.

[0032] 1.4 The steel composition of VOD is C0.0105%, Si0.382%, Mn1.308%, Ni13.374%, Cr17.153%, P0.028%, S0.0015%, and Al0.0055%.

[0033] In the second step, silica and dolomite are added to the LF furnace to make low basicity slag.

[0034] 2.1 According to the VOD lime addition of 1900Kg, incoming Si of 0.117%, molten steel of 102t, reduced ferrosilicon addition of 940Kg, and outgoing silicon of 0.382%, the binary basicity of VOD slag R is calculated to be 2.04.

[0035] 2.2 When LF furnace slag is made, 600Kg silica and 500Kg dolomite are added, and the theoretical LF slag basicity R=1.44.

[0036] 2.3 After the slag is oxidized, the slag sample is taken. It can be seen that the slag sample is black in color, indicating that the slag basicity should be below 1.6, and no silica needs to be added. At the same time, the LF alloying sampling composition is: C0.0126%, Si0.511%, Mn1.421%, Ni13.495%, Cr17.257%, P0.0268%, S0.0016%, Al0.0050%, which meets the exit requirements.

[0037] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for determining slag basicity based on slag color, characterized in that: The following steps are involved: S1. To improve the purity of molten steel and reduce the C content of molten steel, VOD treatment is performed on the molten steel; S2. Add silica and dolomite to the LF furnace to make low basicity slag. According to the VOD slag basicity, the amount of silica and dolomite added during LF furnace slag making is based on the slag basicity R=1.

6. The LF basicity calculation formula is: R=(dolomite addition×0.55+VOD lime addition) / VOD inlet Si%×VOD molten steel volume t×10)×2.14+((reduced ferrosilicon addition-(VOD molten steel volume t×VOD outlet Si×10) / 0.75)×0.75×2.14))+silica addition×0.98), where 2.14 is the conversion coefficient of Si and SiO2, 0.75 is the Si content in ferrosilicon, 0.55 is the proportion of CaO in dolomite, and 0.98 is the proportion of SiO2 in silica; After the slag is chemically processed, take a slag sample. If the slag sample is black or grayish black, the actual alkalinity of the slag should be below 1.6, and no silica needs to be added. If the slag sample is white or grayish white, the slag alkalinity is too high, and 50-200 kg of silica needs to be added for slag adjustment.

2. The method for determining slag basicity according to slag color according to claim 1, characterized in that: In the step S1, in the VOD treatment, the amount of lime added is controlled according to the slag basicity R=1.8, the amount of reduced ferrosilicon added=1.25×(total oxygen consumption in smelting-oxygen consumption of carbon oxide-oxygen consumption of silicon oxide) / silicon content of ferrosilicon+steel output×alloyed silicon content / silicon content of ferrosilicon, where 1.25 means that 1 standard of oxygen requires 1.25 kg of Si, and the Si content of molten steel is controlled at 0.38-0.5%; In VOD treatment, the calculation formula of slag basicity is: R=(amount of lime added Kg) / ((VOD inlet Si%×VOD molten steel volume t×10) ×2.14+((amount of reduced ferrosilicon added-(VOD molten steel volume t×VOD outlet Si×10) / 0.75) ×0.75×2.14)), where 2.14 is the conversion coefficient of Si and SiO2, and 0.75 is the Si content in ferrosilicon.