A method for controlling the composition of high-silicon, high-manganese, aluminum-free heavy rail steel

Abstract

The present invention provides a method for controlling the composition of high-silicon, high-manganese, aluminum-free heavy rail steel, specifically comprising the following steps: S1, molten iron pretreatment; S2, converter smelting: controlling the carbon content of the converter tapping to ≤0.08% or the oxygen content of the tapping to ≥400 ppm; controlling the clearance of the molten steel ladle after tapping to between 800 mm and 1000 mm; S3, LF smelting: controlling the basicity of the LF top slag to between 2.3 and 2.6; controlling the alt in the molten steel entering the VD furnace to ≤0.007%; controlling the Mn content at the discharge end to between 2.10% and 2.20%; and controlling the basicity of the final slag before discharge to between 1.6 and 2.0; S4, VD smelting: controlling the discharge end temperature of the molten steel to between 1560°C ±15°C; and S5, continuous pouring: achieving a target maximum temperature of tundish baking of ≥1320°C during continuous pouring. The technical solution of the present invention can improve the qualified rate of molten steel composition and achieve the goal of producing purer molten steel.

Description

Technical Field

[0001] The present invention relates to the technical field of iron and steel metallurgy, and in particular to a method for controlling the composition of high-silicon, high-manganese, aluminum-free heavy rail steel. Background Art

[0002] Currently, the steelmaking plant produces bainite heavy rail steel using the BOF-LF-VD-CC process. This process is targeted at steel grades with high silicon, high manganese, low sulfur, and no aluminum: finished product silicon 1.45%-1.60%, finished product manganese 2.0%-2.15%, finished product sulfur ≤0.006%, and finished product aluminum ≤0.008%. Using existing steelmaking technology, the addition of large amounts of ferrosilicon alloy during the converter alloying process increases the aluminum content of the steel. The LF treatment uses high-basicity reducing slag for deep desulfurization. The high-basicity top slag in the ladle increases aluminum significantly during the VD treatment. Furthermore, due to the high manganese content, manganese evaporation is severe during the VD treatment, with Mn evaporation ranging from 0.12% to 0.18%. In summary, the process control methods used in the existing technology are difficult to control, which can easily lead to the return of incompatible components to the furnace, seriously affecting the cleanliness of the molten steel or causing the scrapping of the ingots, which also restricts the production of the steel plant. Summary of the Invention

[0003] Based on the above technical problem that the composition of existing heavy rail steel is difficult to control, a method for controlling the composition of high-silicon, high-manganese, and aluminum-free heavy rail steel is provided, which can improve the qualified rate of molten steel composition, achieve the goal of producing purer molten steel, and produce bainitic rails that are more stable and run smoothly.

[0004] The technical means adopted in the present invention are as follows:

[0005] A method for controlling the composition of high-silicon, high-manganese, aluminum-free heavy rail steel, wherein the steel composition of the high-silicon, high-manganese, aluminum-free heavy rail steel is as follows by weight: C: 0.22%-0.26%, Si: 1.45%-1.60%, Mn: 2.0%-2.15%, P≤0.015%, S≤0.006%, Al≤0.008%, and Ti: 0.005%-0.020%. The method specifically comprises the following steps:

[0006] S1, molten iron pretreatment;

[0007] S2. Converter smelting: The converter tapping temperature should be controlled at C≤0.08% or oxygen value≥400ppm, and tapping temperature should be ≥1630℃; the clearance of the molten steel ladle after tapping should be controlled between 800mm-1000mm;

[0008] S3, LF smelting: control the Al2O3 content in the LF top slag to 8%-15%, FeO≤0.9%, control the LF top slag basicity to be between 2.3-2.6; control the Alt in the molten steel entering the VD furnace to be ≤0.007%; the Mn content of the discharged molten steel is between 2.10%-2.20%; the temperature of the discharged molten steel is between 1605℃±10℃; control the basicity of the final slag to be between 1.6-2.0 before discharge;

[0009] S4, VD smelting: the temperature of the molten steel removed is between 1560℃±15℃;

[0010] S5. Continuous pouring: During continuous pouring, the target maximum temperature of the tundish baking is ≥1320℃ and the duration is ≥5min.

[0011] Furthermore, in step S1, the molten iron is desulfurized to S≤0.005%.

[0012] Furthermore, in step S2, the scrap steel used in the converter smelting is clean scrap steel without adding ore-type slag.

[0013] Furthermore, in step S2, the ladle for converter smelting uses a molten steel tank that has never produced aluminum- and titanium-containing steel grades.

[0014] Furthermore, in step S2, the S of the converter steel is controlled to be ≤0.012%; ferrosilicon, silicomanganese, and ferromanganese are used for alloying when the converter steel is tapped, so as to control the C, Si, and Mn contents within the lower limit of the finished product, the ferrosilicon used is ferrosilicon L or low-carbon ferrosilicon, and the ferromanganese used is metallic manganese or sintered manganese balls; and Alt in the molten steel entering the LF furnace is controlled to be ≤0.004%.

[0015] Furthermore, in the LF smelting process of step S3, the composition is adjusted to use ferrosilicon, medium carbon ferromanganese and high titanium ferrosilicon, and the ferrosilicon used is ferrosilicon L or low carbon ferrosilicon.

[0016] Furthermore, in step S3, the elemental composition of C, Si, and Ti removed from LF is controlled according to the target, the removed C is controlled at 0.23-0.25%, the removed Si is controlled at 1.50%-1.55%, the removed Mn is controlled at 2.10%-2.20%, the removed Ti is controlled at 0.010%-0.015%, and the removed S is ≤0.006%.

[0017] Furthermore, during the VD smelting process in step S4, the pressure is maintained for 15-25 minutes, and the target pressure of argon is controlled to be above 0.2 MPa during the pressure maintenance process; during the VD smelting process, the Alt increase of the molten steel is controlled within 0.001%, and the discharged S is ≤0.005%.

[0018] Furthermore, in step S5, a constant casting speed is maintained during the casting process.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] The composition control method of high-silicon and high-manganese aluminum-free heavy rail steel provided by the present invention can stably control the cost of molten steel within a certain range, and the composition adjustment of the LF refining furnace is simple, and the evaporation of the molten steel composition during the VD pressure holding process can be effectively controlled. At the same time, by adjusting the different slag basicities of the LF and VD refining furnaces, the amount of aluminum added to the molten steel can be effectively controlled, and the adsorption effect of the refining on inclusions in the molten steel can be improved, so as to achieve pure molten steel and qualified ingot quality.

[0021] Based on the above reasons, the present invention can be widely promoted in the field of iron and steel metallurgy. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is in no way intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0023] The present invention provides a method for controlling the composition of high-silicon and high-manganese aluminum-free heavy rail steel. The steel composition of the high-silicon and high-manganese aluminum-free heavy rail steel is as follows by weight: C: 0.22%-0.26%, Si: 1.45%-1.60%, Mn: 2.0%-2.15%, P≤0.015%, S≤0.006%, Al≤0.008%, and Ti: 0.005%-0.020%. The method specifically comprises the following steps:

[0024] S1, molten iron pretreatment;

[0025] S2. Converter smelting: The tapping temperature of the converter should be ≥1630°C, with a C content of ≤0.08% or an oxygen content of ≥400ppm. The converter can increase the oxygen content in the molten steel, oxidize the Al in the alloy, and promote the formation of Al2O3 from Al, thereby reducing the aluminum content in the molten steel after converter tapping. At the same time, the low carbon content during the converter smelting process can prevent carbon increase in the molten steel due to a long refining cycle. The clearance of the molten steel tank after tapping should be controlled between 800mm and 1000mm. By controlling the high clearance of the molten steel tank, the risk of molten steel churning out of the tank during the pressure maintenance process of the refining VD furnace can be reduced.

[0026] S3, LF smelting: Control the Al2O3 content in the LF top slag to 8%-15%, FeO≤0.9%, LF produces high basicity reducing slag, and control the basicity of the LF top slag between 2.3-2.6 to ensure the desulfurization effect of the LF refining process;

[0027] Control the Alt content of the molten steel entering the VD furnace to ≤ 0.007%; the Mn content of the discharged molten steel should be between 2.10% and 2.20%; the temperature of the discharged molten steel should be between 1605℃±10℃; and the basicity of the final slag should be between 1.6 and 2.0 before discharge.

[0028] S4, VD smelting: the temperature of the molten steel removed is between 1560℃±15℃;

[0029] The present invention controls the slag-making process of the refined LF furnace top slag and the VD top slag, utilizes the LF high-basicity top slag (2.3-2.6) to remove the sulfur content in the molten steel, and the VD low-basicity top slag (1.6-2.0) to remove the Al content in the molten steel. The present invention utilizes the characteristics of different slag systems in adsorbing different inclusions to achieve the purpose of stably controlling the element content and improving the purity of the molten steel.

[0030] S5. Continuous pouring: During continuous pouring, the target maximum temperature of the tundish baking is ≥1320℃ and the duration is ≥5min.

[0031] Furthermore, in step S1, the molten iron is desulfurized to S≤0.005%.

[0032] Furthermore, in step S2, the scrap steel used in the converter smelting is clean scrap steel without adding ore-type slag.

[0033] Furthermore, in step S2, the ladle for converter smelting uses a molten steel tank that has never produced aluminum- and titanium-containing steel grades.

[0034] Furthermore, in step S2, the S of the converter steel is controlled to be ≤0.012%; ferrosilicon, silicomanganese, and ferromanganese are used for alloying when the converter steel is tapped, so as to control the C, Si, and Mn contents within the lower limit of the finished product, the ferrosilicon used is ferrosilicon L or low-carbon ferrosilicon, and the ferromanganese used is metallic manganese or sintered manganese balls; and Alt in the molten steel entering the LF furnace is controlled to be ≤0.004%.

[0035] Furthermore, during the LF smelting process in step S3, the composition is adjusted to use ferrosilicon with less aluminum, such as ferrosilicon L or low-carbon ferrosilicon, medium-carbon ferromanganese and high-titanium ferrotitanium, to prevent residual Al in the alloy from being brought into the molten steel.

[0036] Furthermore, in step S3, the elemental composition of C, Si, and Ti removed from LF is controlled according to the target, the removed C is controlled at 0.23-0.25%, the removed Si is controlled at 1.50%-1.55%, the removed Mn is controlled at 2.10%-2.20%, the removed Ti is controlled at 0.010%-0.015%, and the removed S is ≤0.006%.

[0037] Furthermore, during the step S4 VD smelting process, the pressure is maintained for 15-25 minutes. During the pressure maintaining process, the argon amount is adjusted as much as possible, and the argon target pressure is controlled to be above 0.2 MPa. The argon blowing pressure can also be appropriately adjusted according to the actual argon blowing effect of the breathable brick and the tumbling effect of the molten steel surface; the longer the pressure maintaining time, the better the H removal effect, but the more Mn evaporates; the shorter the pressure maintaining time, the less Mn evaporates, but the H removal effect cannot be guaranteed. Therefore, the reasonable pressure maintaining time of the present invention is to take into account both the H removal effect and the Mn evaporation amount; VD smelting low-alkalinity, aluminum-free reducing slag can inhibit the increase of aluminum in molten steel. During the VD smelting process, the Alt increase in molten steel is controlled within 0.001%, and the discharged S is ≤0.005%.

[0038] Furthermore, in step S5, pouring can only be started after ensuring that the tundish is clean, and a constant pulling speed is maintained during the pouring process.

[0039] The composition control method of high-silicon and high-manganese aluminum-free heavy rail steel provided by the present invention can stably control the cost of molten steel within a certain range, and the composition adjustment of the LF refining furnace is simple, and the evaporation of the molten steel composition during the VD pressure holding process can be effectively controlled. At the same time, by adjusting the different slag basicities of the LF and VD refining furnaces, the amount of aluminum added to the molten steel can be effectively controlled, and the adsorption effect of the refining on inclusions in the molten steel can be improved, so as to achieve pure molten steel and qualified ingot quality.

[0040] The composition control method of the high-silicon and high-manganese aluminum-free heavy rail steel of the present invention is described below with reference to specific examples.

[0041] Example 1

[0042] The method for controlling the composition of high-silicon and high-manganese aluminum-free heavy rail steel provided in this embodiment specifically includes the following steps:

[0043] S1. Hot metal pretreatment: desulfurize the hot metal to a sulfur content of 0.002%;

[0044] S2. Converter smelting: 8 tons of clean scrap steel and 95 tons of molten iron are added to the converter, and a molten steel tank that has never produced aluminum- and titanium-containing steel is used. The converter tapping temperature is controlled at 0.068% and 1638°C. The converter tapping temperature is controlled at 0.010%. 1960 kg of low-carbon ferrosilicon, 2020 kg of silicon manganese, and metallic manganese are alloyed during converter tapping. The steel tank clearance after tapping is 950 mm.

[0045] S3, LF smelting: Control the Al2O3 content in the LF top slag to 12.6%, the FeO content to 0.4%, make high basicity reducing slag in LF, and control the basicity of the LF top slag to 2.36 to ensure the desulfurization effect of the LF refining process;

[0046] The Alt content of the molten steel entering the VD furnace is controlled at 0.004%; the Mn content of the molten steel discharged is controlled at 2.16%; and the temperature of the molten steel discharged is controlled at 1609°C.

[0047] During the LF smelting process, the adjusted composition is 236 kg, 241 kg of medium carbon ferromanganese, and 50 kg of high titanium ferrotitanium;

[0048] The C content is controlled at 0.236%, the Si content is controlled at 1.53%, the Ti content is controlled at 0.014%, and the S content is 0.004%.

[0049] Control the final slag basicity between 1.6-2.0 before moving out;

[0050] S4, VD smelting: the temperature of the molten steel is 1570℃; the molten steel content is C: 0.231%, Si: 1.54%, Mn: 2.06%, Ti: 0.013%, S: 0.002%, Al: 0.004%;

[0051] S5, continuous pouring;

[0052] The remaining control processes and parameters are as described above and will not be repeated here.

[0053] Example 2

[0054] The method for controlling the composition of high-silicon and high-manganese aluminum-free heavy rail steel provided in this embodiment specifically includes the following steps:

[0055] S1. Hot metal pretreatment: desulfurize the hot metal to a sulfur content of 0.001%;

[0056] S2. Converter smelting: 9.5t of clean scrap steel and 94t of molten iron were added to the converter, and a molten steel tank that had never produced aluminum- or titanium-containing steel was used. The C content of the converter tapping was controlled at 0.064% and the tapping temperature was 1641°C. The S content of the converter tapping was controlled at 0.012%. 1960kg of low-carbon ferrosilicon, 2020kg of silicon manganese, and metallic manganese were alloyed during converter tapping. The clearance of the molten steel tank after tapping was 920mm.

[0057] S3, LF smelting: Control the Al2O3 content in the LF top slag to 10.2%, the FeO content to 0.3%, make high basicity reducing slag in LF, control the basicity of the LF top slag to 2.44, and ensure the desulfurization effect of the LF refining process;

[0058] The Alt content of the molten steel entering the VD furnace is controlled at 0.004%; the Mn content of the molten steel discharged is controlled at 2.18%; and the temperature of the molten steel discharged is controlled at 1613°C.

[0059] During the LF smelting process, the composition was adjusted to use 245kg of ferrosilicon, 235kg of medium carbon ferromanganese, and 45kg of high titanium ferrotitanium;

[0060] The C content is controlled at 0.24%, the Si content is controlled at 1.51%, the Ti content is controlled at 0.015%, and the S content is 0.003%;

[0061] Control the final slag basicity between 1.6-2.0 before moving out;

[0062] S4, VD smelting: hold pressure for 20 minutes; the temperature of the molten steel is 1570℃; the molten steel content is C: 0.235%, Si: 1.52%, Mn: 2.09%, Ti: 0.014%, S: 0.002%, Al: 0.006%;

[0063] S5, continuous pouring;

[0064] The remaining control processes and parameters are as described above and will not be repeated here.

[0065] Example 3

[0066] The method for controlling the composition of high-silicon and high-manganese aluminum-free heavy rail steel provided in this embodiment specifically includes the following steps:

[0067] S1. Hot metal pretreatment: desulfurize the hot metal to a sulfur content of 0.001%;

[0068] S2. Converter smelting: 9 tons of clean scrap steel and 94 tons of molten iron are added to the converter. A molten steel tank that has never produced aluminum- or titanium-containing steel is used. The C content of the converter tapping is controlled at 0.06% and the tapping temperature is 1644°C. The S content of the converter tapping is controlled at 0.009%. 1980 kg of low-carbon ferrosilicon, 2040 kg of silicon manganese, and metallic manganese are alloyed during converter tapping. The clearance of the molten steel tank after tapping is 900 mm.

[0069] S3, LF smelting: Control the Al2O3 content in the LF top slag to 12.3%, the FeO content to 0.3%, make high basicity reducing slag in LF, and control the basicity of the LF top slag to 2.55 to ensure the desulfurization effect of the LF refining process;

[0070] The Alt content of the molten steel entering the VD furnace is controlled at 0.004%; the Mn content of the molten steel discharged is controlled at 2.15%; and the temperature of the molten steel discharged is controlled at 1615°C.

[0071] During the LF smelting process, the composition was adjusted to use 240kg of ferrosilicon, 230kg of medium carbon ferromanganese, and 55kg of high titanium ferrotitanium;

[0072] The C content is controlled at 0.246%, the Si content is controlled at 1.50%, the Ti content is controlled at 0.011%, and the S content is 0.003%.

[0073] Control the final slag basicity between 1.6-2.0 before moving out;

[0074] S4, VD smelting: hold pressure for 23 minutes; the temperature of the molten steel is 1565℃; the molten steel content is C: 0.241%, Si: 1.51%, Mn: 2.04%, Ti: 0.011%, S: 0.003%, Al: 0.005%;

[0075] S5, continuous pouring;

[0076] The remaining control processes and parameters are as described above and will not be repeated here.

[0077] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for controlling the composition of high-silicon, high-manganese, aluminum-free heavy rail steel, wherein the steel composition of the high-silicon, high-manganese, aluminum-free heavy rail steel is as follows by weight: C: 0.22%-0.26%, Si: 1.45%-1.60%, Mn: 2.0%-2.15%, P≤0.015%, S≤0.006%, Al≤0.008%, Ti: 0.005%-0.020%; characterized in that: The specific steps include: S1. Hot metal pretreatment: desulfurize the hot metal to a sulfur content of ≤ 0.002%; S2. Converter smelting: The C content of converter steel tapping is controlled to be ≤0.068% or the oxygen content of the steel tapping is ≥400ppm, and the tapping temperature is ≥1630℃; the clearance of the molten steel ladle after tapping is controlled between 800mm and 1000mm; the S content of converter steel tapping is controlled to be ≤0.012%; ferrosilicon, silicomanganese, and ferromanganese are used for alloying during converter tapping to control the C, Si, and Mn contents to the lower limit of the finished product. The ferrosilicon used is ferrosilicon L or low-carbon ferrosilicon, and the ferromanganese used is metallic manganese or sintered manganese balls; the Alt content of the molten steel entering the LF furnace is controlled to be ≤0.004%; S3, LF smelting: Control the Al2O3 content in the LF top slag to 8%-15%, FeO≤0.9%, and control the basicity of the LF top slag between 2.44-2.6; During the LF smelting process, adjust the composition to use ferrosilicon, medium carbon ferromanganese and high titanium ferrotitanium, and the ferrosilicon used is ferrosilicon L or low carbon ferrosilicon; The LF discharge C, Si and Ti elemental composition is controlled according to the target, the discharge C is controlled at 0.23-0.25%, the discharge Si is controlled at 1.50%-1.55%, the discharge Mn is controlled at 2.10%-2.20%, the discharge Ti is controlled at 0.010%-0.015%, and the discharge S is ≤0.006%; Control the Alt content of the molten steel entering the VD furnace to ≤ 0.007%; the Mn content of the discharged molten steel should be between 2.10% and 2.20%; the temperature of the discharged molten steel should be between 1605℃±10℃; and the basicity of the final slag should be between 1.6 and 2.0 before discharge. S4, VD smelting: the temperature of the molten steel discharged is between 1560℃±15℃; during the VD smelting process, the pressure is maintained for 15-25 minutes, and the argon target pressure is controlled above 0.2MPa during the pressure maintenance process; during the VD smelting process, the Alt increase of the molten steel is controlled within 0.001%, and the discharged S is ≤0.005%; S5. Continuous pouring: During continuous pouring, the target maximum temperature of the tundish baking is ≥1320℃ and the duration is ≥5min.

2. The method for controlling the composition of high-silicon and high-manganese aluminum-free heavy rail steel according to claim 1, characterized in that: In step S2, the scrap steel used in converter smelting is clean scrap steel without adding ore-type slag.

3. The method for controlling the composition of high silicon and high manganese aluminum-free heavy rail steel according to claim 1, characterized in that: In step S2, the ladle for converter smelting uses a molten steel tank that has never produced aluminum- and titanium-containing steel grades.

4. The method for controlling the composition of high silicon and high manganese aluminum-free heavy rail steel according to claim 1, characterized in that: In step S5, a constant casting speed is maintained during the casting process.