CN108774660B - Smelting method of DT L A steel - Google Patents

Smelting method of DT L A steel Download PDF

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CN108774660B
CN108774660B CN201810709045.4A CN201810709045A CN108774660B CN 108774660 B CN108774660 B CN 108774660B CN 201810709045 A CN201810709045 A CN 201810709045A CN 108774660 B CN108774660 B CN 108774660B
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steel
smelting
oxygen
converter
slag
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CN108774660A (en
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陈路
曾建华
梁新腾
王建
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Pangang Group Panzhihua Iron and Steel Research Institute Co Ltd
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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
    • C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
    • C21C5/28—Manufacture of steel in the converter
    • 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
    • C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
    • C21C5/28—Manufacture of steel in the converter
    • C21C5/36—Processes yielding slags of special composition
    • 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
    • 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
    • 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
    • C21C2200/00—Recycling of waste material

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  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Treatment Of Steel In Its Molten State (AREA)
  • Carbon Steel Or Casting Steel Manufacturing (AREA)

Abstract

The invention belongs to the field of metallurgy, and particularly relates to a smelting method of DT L A steel, which aims at the problem of high slagging and deoxidation costs in the smelting of DT L A steel by the existing method, and comprises the following steps of a, during converter smelting, retaining slag 2/3 from end-point slag of a converter in the previous furnace, adding semisteel, adding active lime and high-magnesium lime into the furnace, adding 6-9 kg/t of treated converter waste slag into the steel, blowing oxygen while adding, performing converter smelting, controlling the end-point slag alkalinity to be 3-4, tapping when end-point carbon is 0.05-0.07% and the temperature is 1650-1670 ℃, adding aluminum iron of steel of 1.5-2.5 kg/t into a steel ladle for deoxidation, then conducting oxygen determination on a small platform, feeding aluminum wire for deoxidation after oxygen determination, and smelting to obtain DT L A steel, wherein steel smelting auxiliary materials and acidic composite slag are replaced by waste converter slag, and qualified steel of low cost can be obtained through smelting L A steel.

Description

Smelting method of DT L A steel
Technical Field
The invention belongs to the technical field of metallurgy, and particularly relates to a smelting method of DT L A steel.
Background
The DT L A steel is a low-carbon aluminum killed steel which is independently developed by Pan Steel group, is a steel grade with wide application, has low component carbon content, has higher content of dissolved oxygen in molten steel after smelting in a converter, and must perform excess aluminum deoxidation on the dissolved oxygen in the molten steel for improving the deep drawing performance, otherwise, the casting of the molten steel is influenced, and a casting blank or steel ingot with reasonable structure cannot be obtained.
The deoxidation of the DT L A steel smelting process is particularly important, the existing smelting method generally adopts a semi-steel-converter smelting-L F smelting-continuous casting process, 20-25 kg/t of steel is added with active lime, 20-25 kg of high-magnesium lime and 12-17 kg/t of acid composite slag during converter smelting, and 3.5-4.5 kg/t of aluminum iron of the steel is added into a steel ladle for deoxidation in the tapping process.
However, the existing method for smelting DT L A steel has the defects of high slagging cost, high deoxidation cost and the like, and needs to be further improved.
Disclosure of Invention
The invention aims to solve the technical problems of high slagging cost, high deoxidation cost and the like in the process of smelting DT L A steel in the prior art.
The technical scheme for solving the technical problems is to provide a smelting method of DT L A steel, which comprises the following steps:
a. when the converter is smelted, 2/3 of slag remained at the end point of the last converter is added, semisteel is added, 10-14 kg/t of steel of active lime and 10-14 kg/t of steel of high-magnesium lime are added into the converter, 6-9 kg/t of steel of the treated converter waste slag is added, oxygen is blown while the steel is added, converter smelting is carried out, and the alkalinity of the end point slag is controlled to be 3-4; tapping when the end point carbon is 0.05% -0.07% and the temperature is 1650-1670 ℃;
b. and during tapping, adding 1.5-2.5 kg/t of aluminum iron of steel into a ladle for deoxidation, then carrying out oxygen determination on a small platform, feeding an aluminum wire for deoxidation after oxygen determination, and smelting to obtain DT L A steel.
In the smelting method of the DT L A steel, the semi-steel in the step a comprises, by weight, 3.25-3.85% of C, 0.01-0.03% of Si, 0.01-0.03% of Mn, 0.045-0.080% of P and 0.018-0.025% of S, preferably, the semi-steel comprises, by weight, 3.46% of C, 0.02% of Si, 0.02% of Mn0.02%, 0.06% of P and 0.024% of S.
In the smelting method of DT L A steel, the lance position of the oxygen lance in the oxygen blowing process in the step a is 1.4-2 m, preferably 1.4-1.8 m, the lance position of the oxygen lance refers to the distance from the tail end of the nozzle of the oxygen lance to the liquid level of the molten pool, the lance position in the blowing process is 2m, the lance is prevented from being burnt, the carbon lance position is 1.4m, and the good fluidity of the molten slag is ensured so as to early melt the slag, remove more phosphorus and protect the furnace lining.
Wherein in the smelting method of DT L A steel, when the oxygen blowing progress in the step a is 0-40%, the oxygen supply intensity of the oxygen lance is 2.5-3.0 m3T.min, the oxygen blowing progress is 40 percent until the blowing is finished, and the oxygen supply intensity of the oxygen lance is 3.5 to 4.5m3/t·min。
The overall converting control principle is: rapid slagging and early slagging, active slag, and no drying or splashing in the process.
In the smelting method of DT L A steel, for better dephosphorization, the active lime in the step a is active lime with CaO content of 85-90 wt%.
In the smelting method of DT L A steel, for better dephosphorization, the high-magnesium lime in the step a is the high-magnesium lime with 48-55 wt% of CaO and 30-40 wt% of MgO.
In the smelting method of DT L A steel, for better dephosphorization, the converter end-point waste slag in the step b comprises 18-23% of FeO and Fe by weight percentage2O38 to 12%, MFe 5 to 10%, CaO 35 to 43%, SiO210 to 15% of Al2O31 to 3%, 1 to 2% MnO, 10 to 15% MgO, 0.8 to 1.3% P, 0.02 to 0.05% S, and the balance unavoidable impurities.
In the smelting method of DT L A steel, for better deoxidation, the aluminum iron in the step b is aluminum iron with 40-42 wt% of aluminum content and 57-59 wt% of iron content.
In the method for smelting DT L A steel, the aluminum added in the step b of feeding the aluminum wire is aluminum with the purity of 99.1-99.5% for better deoxidation.
In the smelting method of DT L A steel, the aluminum wire feeding standard in step b is 150m when the oxygen activity of molten steel is less than or equal to 100ppm, 200m when the oxygen activity of molten steel is 100-200 ppm, 300m when the oxygen activity of molten steel is 200-300 ppm, and 450m when the oxygen activity of molten steel is more than 300.
The method for smelting DT L A steel has the advantages that the converter end point waste slag is returned to the semisteel steelmaking converter to partially replace the metallurgical auxiliary materials such as lime, high-magnesium lime and the like, and a large amount of CaO and SiO in the converter end point waste slag are fully utilized2The steel-making method comprises the steps of adding a small amount of aluminum-iron alloy into the steel-making process for preliminary deoxidation, then feeding aluminum wires into the molten steel for deoxidation according to the oxygen content of the molten steel after small-platform oxygen determination, and further reducing the production cost.
Detailed Description
The invention provides a smelting method of DT L A steel, which returns the converter end point waste slag to a semisteel steelmaking converter to partially replace metallurgical auxiliary materials for steelmaking, thereby saving the production cost.
The invention provides a smelting method of DT L A steel, which comprises the following steps:
a. when the converter is smelted, 2/3 of slag remained at the end point of the last converter is added, semisteel is added, 10-14 kg/t of steel of active lime and 10-14 kg/t of steel of high-magnesium lime are added into the converter, 6-9 kg/t of steel of the treated converter waste slag is added, oxygen is blown while the steel is added, converter smelting is carried out, and the alkalinity of the end point slag is controlled to be 3-4; tapping when the end point carbon is 0.05% -0.07% and the temperature is 1650-1670 ℃;
b. and during tapping, adding 1.5-2.5 kg/t of aluminum iron of steel into a ladle for deoxidation, then carrying out oxygen determination on a small platform, feeding an aluminum wire for deoxidation after oxygen determination, and smelting to obtain DT L A steel.
The converter end point waste slag used by the invention comprises the following components: according to weight percentage, FeO accounts for 18-23%, Fe2O38 to 12%, MFe 5 to 10%, CaO 35 to 43%, SiO210 to 15% of Al2O31 to 3%, 1 to 2% MnO, 10 to 15% MgO, 0.8 to 1.3% P, 0.02 to 0.05% S, and the balance unavoidable impurities. The waste slag is preferably smelted by a steel-climbing converter, the phosphorus content of the waste slag does not reach the dephosphorization limit, and the inventor finds that the waste slag can be recycled through accurate analysis. The specific principle is as follows:
the dephosphorization reaction in steel making can be represented by the formula (1):
2[P]+5[O]＝(P2O5) (1)
ΔGo＝-151200+123.74T (2)
according to the isothermal equation,
Figure BDA0001715984170000031
to enable equation (2) to proceed, Δ G must be negative, i.e., negative. J is less than K;
of formula (2)
Figure BDA0001715984170000032
When T1873, K4.4 × 10～10，
Therefore, the conditions that enable equation (2) to be performed are:
Figure BDA0001715984170000033
according to the typical slag composition CaO of a steel converter: 40 percent; SiO 22: 12 percent; MgO: 12 percent; FeO: 20 percent; MnO: 6% calculated
Figure BDA0001715984170000034
End point of molten steel [ P ]]＝0.012％、[O]Calculating the limit P in the final slag of the converter when the slag is 0.06 percent2O5The molar concentration is 0.0118, which corresponds to about 2.36% P2O5. Pan steel converter final slag P2O5Generally about 1.0 percent and far less than the limit target, which indicates that the current operating process parameters of the steel climbing are far from the optimal values, so that all or part of the converter can return to the continuous steelmaking by using the waste slag at the end point of the converter.
Therefore, through a large number of tests, the inventor adds the waste slag at the end point of the converter into the converter again, reduces the addition of steelmaking auxiliary materials such as lime, high-magnesium lime and the like, does not add the acidic composite slag any more, and changes the deoxidation process in the tapping process to obtain the smelting method of the DT L A steel.
The original acidic composite slag mainly adopts Si and Mn components for dephosphorization, the cost is high, and the converter end-point waste slag contains FeO, CaO and SiO2And the dephosphorization of the molten steel can be effectively carried out by using the components, the production cost is saved, and the dephosphorization effect is good.
The following examples are intended to illustrate specific embodiments of the present invention without limiting the scope of the invention to the examples.
The active lime used in the examples and comparative examples had the composition: 85-90% ofCaO. The high-magnesium lime comprises the following components: 48-55% of CaO and 30-40% of MgO. The acidic composite slag comprises the following components: SiO 22: 48%, MgO: 10%, CaO: 12%, TFe (total iron): 20%, MnO: 8% of Al2O3: 2%, and inevitable impurities. The composition of the waste slag of the converter is 18 percent of FeO and 9 percent of Fe2O37% of MFe, 36% of CaO, 13% of SiO22% of Al2O3MnO of 1.5 percent, MgO of 11 percent, P of 1.0 percent and S of 0.03 percent, and the balance is inevitable impurities; the water content of the waste slag is less than 1 percent.
Example 1 DT L A Steel smelted by the method of the invention
And (2) smelting in a 120t converter, adding 12kg/t of steel with active lime and 12kg/t of high-magnesium lime into the converter while blowing after adding semisteel into the converter, adding 6kg/t of steel with treated converter waste slag, wherein an oxygen lance nozzle is 1.4-2 m away from the basic lance position of the molten pool metal liquid level, a blowing lance position is 1.4-1.8 m, and a blowing lance position is 2m, so that lance burning is prevented. The carbon drawing gun position is 1.4 m. Ensures that the slag has good fluidity so as to early melt the slag, remove more phosphorus and protect the furnace lining. In the invention, the lance position of the oxygen lance refers to the distance from the spray head end of the oxygen lance spray head to the liquid level of the molten pool. Controlling the end point slag alkalinity between 3 and 4, and controlling the oxygen supply intensity of the oxygen lance to be 2.5 to 3.0m when the oxygen blowing progress is 0 to 40 percent3Between t and min, the oxygen blowing rate is 40% and the oxygen supply intensity is 3.5-4.5 m3And (4) within the range of/t.min until the blowing end point, and obtaining molten steel qualified at the end point.
The composition of the end-point molten steel is as follows: c: 0.05%, P: 0.011%, S: 0.015 percent.
During tapping, firstly adding aluminum iron into a steel ladle, wherein the adding amount of the aluminum iron is 1.975kg/t of steel, then, fixing oxygen on a small platform, wherein the oxygen activity is 28ppm after oxygen fixing, and feeding an aluminum wire for 30 m.
In the embodiment, the cost for smelting each ton of DT L A steel is 2950 yuan.
Example 2 DT L A Steel smelted by the method of the invention
Smelting in a 120t converter, adding half steel into the converter, blowing while adding 12kg/t steel of active lime and 12.2kg high-magnesium lime into the converter, and adding the treated converter6kg/t steel of waste slag in the furnace, 1.4-2 m of basic lance position of an oxygen lance nozzle from the metal liquid level of a molten pool, 1.4-1.8 m of blowing lance position, and 2m of blowing lance position, so that the lance is prevented from being burnt. The carbon drawing gun position is 1.4 m. Ensures that the slag has good fluidity so as to early melt the slag, remove more phosphorus and protect the furnace lining. In the invention, the lance position of the oxygen lance refers to the distance from the spray head end of the oxygen lance spray head to the liquid level of the molten pool. Controlling the end point slag alkalinity between 3 and 4, and controlling the oxygen supply intensity of the oxygen lance to be 2.5 to 3.0m when the oxygen blowing progress is 0 to 40 percent3Between t and min, the oxygen blowing rate is 40% and the oxygen supply intensity is 3.5-4.5 m3And (4) within the range of/t.min until the blowing end point, and obtaining molten steel qualified at the end point.
The composition of the end-point molten steel is as follows: c: 0.05%, P: 0.010%, S: 0.014%.
Adding aluminum iron into a steel ladle in the tapping process, wherein the adding amount of the aluminum iron is 1.975kg/t of steel, then, determining oxygen on a small platform, the oxygen activity is 30ppm after oxygen determination, and feeding an aluminum wire for 50 m.
In the embodiment, the cost for smelting each ton of DT L A steel is 2960 yuan.
Comparative example 3 DT L A Steel smelted by the existing method
The 120t converter adopts semisteel for steelmaking, after the semisteel is added into the converter, 21kg/t steel of active lime, 21kg of high-magnesium lime and 15kg/t steel of acid composite slag are added into the converter while blowing is carried out, the basic lance position of an oxygen lance nozzle from the metal liquid level of a molten pool is 1.4-2 m, the blowing lance position is 1.4-1.8 m, the blowing lance position is 2m, and burning is prevented. The carbon drawing gun position is 1.4 m. Ensures that the slag has good fluidity so as to early melt the slag, remove more phosphorus and protect the furnace lining. In the invention, the lance position of the oxygen lance refers to the distance from the spray head end of the oxygen lance spray head to the liquid level of the molten pool. Controlling the end point slag alkalinity between 3 and 4, and controlling the oxygen supply intensity of the oxygen lance to be 2.5 to 3.0m when the oxygen blowing progress is 0 to 40 percent3Between t and min, the oxygen blowing rate is 40% and the oxygen supply intensity is 3.5-4.5 m3And (4) within the range of/t.min until the blowing end point, and obtaining qualified end point molten steel.
The composition of the end-point molten steel is as follows: c: 0.055%, P: 0.011%, S: 0.013%.
In the tapping process, firstly adding aluminum iron into a ladle, wherein the adding amount of the aluminum iron is 3.986kg/t steel.
In the comparative example, the cost for smelting each ton of DT L A steel is 2987 yuan.
From the examples and comparative examples it can be seen that: after converter waste slag is adopted to replace part of metallurgical auxiliary materials, the end point steel components can meet the smelting requirements, the total auxiliary materials are reduced by 16kg/t steel, the alloy cost can be reduced by 7.62 yuan/ton steel, the utilization efficiency of aluminum and iron is improved, and the benefit is remarkable.

Claims (7)

  1. The smelting method of DT L A steel is characterized by comprising the following steps:
    a. when the converter is smelted, 2/3 of slag remained at the end point of the last converter is added, semisteel is added, 10-14 kg/t of steel of active lime and 10-14 kg/t of steel of high-magnesium lime are added into the converter, 6-9 kg/t of steel of the treated converter waste slag is added, oxygen is blown while the steel is added, converter smelting is carried out, and the alkalinity of the end point slag is controlled to be 3-4; tapping when the end point carbon is 0.05% -0.07% and the temperature is 1650-1670 ℃; the waste slag of the converter comprises the following components: according to weight percentage, FeO accounts for 18-23%, Fe2O38 to 12%, MFe 5 to 10%, CaO 35 to 43%, SiO210 to 15% of Al2O31 to 3%, 1 to 2% of MnO, 10 to 15% of MgO, 0.8 to 1.3% of P, 0.02 to 0.05% of S, and the balance unavoidable impurities;
    b. and during tapping, adding 1.5-2.5 kg/t of aluminum and iron of steel into a ladle for deoxidation, then fixing oxygen on a small platform, feeding an aluminum wire for deoxidation after the oxygen fixing, and smelting to obtain DT L A steel, wherein the aluminum wire feeding standard is that when the oxygen activity of molten steel is less than or equal to 100ppm, the aluminum wire feeding amount is 150m, when the oxygen activity of the molten steel is more than 100ppm and less than 200ppm, the aluminum wire feeding amount is 200m, when the oxygen activity of the molten steel is 200-300 ppm, the aluminum wire feeding amount is 300m, and when the oxygen activity of the molten steel is more than 300ppm, the aluminum wire feeding amount is 450 m.
  2. 2. The DT L A steel smelting method according to claim 1, wherein the lance position during oxygen blowing in step a is 1.4-2 m.
  3. 3. The method for smelting DT L A steel according to claim 1, wherein the step a is performed byWhen the oxygen blowing progress is 0-40%, the oxygen supply intensity of the oxygen lance is 2.5-3.0 m3During the normal condition, the oxygen blowing process is 40% till the end of blowing, and the oxygen supply intensity of the oxygen lance is 3.5-4.5 m3/t ▪min。
  4. 4. The DT L A steel smelting method according to claim 1, characterized in that the active lime in step a is active lime with CaO content of 85-90 wt%.
  5. 5. The DT L A steel smelting method according to claim 1, wherein the high-magnesium lime in step a is a high-magnesium lime with CaO content of 48-55 wt% and MgO content of 30-40 wt%.
  6. 6. The method for smelting DT L A steel according to claim 1, wherein the aluminum-iron in step b is aluminum-iron with 40-42 wt% aluminum and 57-59 wt% iron.
  7. 7. The method for smelting DT L A steel according to claim 1, wherein the aluminum added during the feeding of the aluminum wire in step b is aluminum with a purity of 99.1-99.5%.
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