CN113637822A - Molten steel alloying method - Google Patents

Molten steel alloying method Download PDF

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Publication number
CN113637822A
CN113637822A CN202110859174.3A CN202110859174A CN113637822A CN 113637822 A CN113637822 A CN 113637822A CN 202110859174 A CN202110859174 A CN 202110859174A CN 113637822 A CN113637822 A CN 113637822A
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Prior art keywords
molten steel
phosphorus
tapping
iron
alloy
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陈永亮
贠海振
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Hebei Rongxin Iron And Steel Co ltd
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Hebei Rongxin Iron And Steel 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
    • 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
    • C21C7/0068—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00 by introducing material into a current of streaming metal

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

Abstract

The invention discloses a molten steel alloying method, which comprises the following steps: step one, adding surface iron during converter tapping, blowing argon in the whole process during tapping, blowing argon at the bottom of a ladle, and stirring; adding other alloys into a refining furnace or a ladle to ensure that the alloy content in molten steel meets the steel grade requirement; on one hand, the invention enables alloy elements such as C, Si, Mn and the like contained in the bread iron to replace part of carburant, ferromanganese and ferrosilicon alloy, reduces the alloy consumption, thereby saving the alloy cost; on the other hand, as the bread iron can be directly changed into molten steel, the steel yield is increased, so that the consumption of slagging materials such as lime, dolomite and the like is reduced, the energy is saved, and the steel-making cost is reduced.

Description

Molten steel alloying method
Technical Field
The invention relates to the technical field of steel smelting, in particular to a molten steel alloying method.
Background
In the tapping process of the converter, oxygen brought by oxygen blowing of an oxygen lance enters molten steel, and in order to ensure that the molten steel is smoothly cast in a continuous casting process, the molten steel needs to be deoxidized, and alloy materials are added according to the purpose of steel so as to meet the mechanical properties of the steel, such as yield strength, tensile strength, hardness, toughness and the like. At present, silicon-manganese alloy is used for deoxidation alloying, the cost is high, and the absorption rate is greatly influenced by the end point, so that a new molten steel alloying method needs to be provided, and the production cost is reduced.
Disclosure of Invention
The present invention is directed to a method for alloying molten steel, which overcomes the above-mentioned disadvantages of the prior art.
In order to solve the problems, the technical scheme adopted by the invention is as follows:
a molten steel alloying method comprises the following steps:
step one, adding surface iron when tapping is carried out in a converter, blowing argon in the whole tapping process, wherein the argon blowing pressure at the bottom of a ladle is 0.25-0.30 MPa, and the argon flow is 270-300 NL/min, and stirring;
adding other alloys into a refining furnace or a ladle to ensure that the alloy content in molten steel meets the steel grade requirement;
the method for calculating the addition amount of the bread iron comprises the following steps:
1) controlling the addition amount of the ladle iron by taking the phosphorus increase amount as a standard limiting condition:
phosphorus in molten steel depends on: phosphorus content at the end point of the converter, phosphorus return amount in tapping and refining processes and phosphorus increment brought by alloy,
△p＝ptarget-(pTapping+pComprises+pGo back to) (1-1)
(m1×p1+m2×p2)/(m1+m2)≤△p (1-2)
pComprises＝ΣMη×ω[P]η/MGeneral assembly (1-3)
In the formula: delta p is the maximum phosphorus increment of the molten steel;
ptargetThe target content is the finished product;
ptappingThe phosphorus content is the blowing end point;
pcomprisesIntroducing phosphorus content into the alloy;
pgo back toThe amount of phosphorus returned in the tapping process;
m1is the molten steel quantity, t;
p1the content of phosphorus in the molten steel is percent;
m2adding amount of bread iron t;
p2the phosphorus content in the bread iron is percent;
Mηis the alloy addition, t;
ω[P]ηis the phosphorus content in the alloy,%;
Mgeneral assemblyThe total amount of each alloy;
2) controlling the iron addition of the ladle by taking the carbon increment as the control surface:
(m1×ωc1+m2×ωc2)/(m1+m2)＝Cm (1-4)
in the formula: m is1Is the molten steel quantity, t;
m2is the amount of bread iron, t;
ωc1carbon content in molten steel,%;
ωc2the carbon content of the bread iron is percent;
Cmtarget carbon content,%.
Further, the tapping temperature of the converter is 1640-1680 ℃, and the tapping temperature is reduced to be less than 40 ℃.
Further, when the steel tapping weight is 1/3 of the total steel tapping weight, the surface iron is added, and the adding is finished when the steel tapping weight reaches 3/4.
Further, before tapping, the bread iron is baked in a gas baking oven for 15-20min at the baking temperature of 800-.
Adopt the produced beneficial effect of above-mentioned technical scheme to lie in:
on one hand, the invention enables alloy elements such as C, Si, Mn and the like contained in the bread iron to replace part of carburant, ferromanganese and ferrosilicon alloy, reduces the alloy consumption, thereby saving the alloy cost; on the other hand, as the bread iron can be directly changed into molten steel, the steel yield is increased, so that the consumption of slagging materials such as lime, dolomite and the like is reduced, the energy is saved, and the steel-making cost is reduced.
Detailed Description
The following examples further describe embodiments of the present invention in detail. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.
The invention discloses a specific implementation mode of a molten steel alloying method, which comprises the following steps:
step one, when converter tapping is carried out, the converter tapping temperature is 1640-1680 ℃, the tapping temperature is reduced to be less than 40 ℃, when the tapping weight accounts for 1/3 of the total tapping weight, the bread iron is added, the adding is finished when the tapping weight reaches 3/4, the bread iron is baked in a gas baking oven for 20min before tapping, the baking temperature is 900 ℃, argon is blown in the whole tapping process, the argon blowing pressure at the bottom of a molten steel ladle is 0.25-0.30 MPa, and the argon flow is 270-300 NL/min, and stirring is carried out;
adding other alloys into a refining furnace or a ladle to ensure that the alloy content in molten steel meets the steel grade requirement;
only iron ladles are added in the alloying process of converter tapping, the silicomanganese alloying process is carried out, aluminum is used for deoxidation, and the aluminum content is controlled to be 0.005%; other alloy elements (such as vanadium-nitrogen alloy, molybdenum-chromium alloy and the like) can be carried out in a refining furnace or a ladle after tapping is finished, and whether the silicon-manganese alloy is supplemented or not is determined according to the control of national standard components.
The method for calculating the addition amount of the bread iron comprises the following steps:
1) controlling the addition of ladle iron by using phosphorus increase as standard limiting condition
Because the alloy contains phosphorus and the process returns phosphorus, the molten steel of the alloy generally increases phosphorus. Therefore, the determination of the phosphorus increment is an important problem in the alloying process by using the bread iron. The phosphorus in the molten steel depends on: phosphorus content at the end point of the converter, phosphorus return amount in tapping and refining processes and phosphorus increment brought by alloy;
△p＝ptarget-(pTapping+pComprises+pGo back to) (1-1)
(m1×p1+m2×p2)/(m1+m2)≤△p (1-2)
pComprises＝ΣMη×ω[P]η/MGeneral assembly (1-3)
Because the phosphorus of the molten steel at the end point of the converter can be detected, the phosphorus brought in by the alloy can also be calculated, and the rephosphorization amount can be controlled within 0-0.003 percent by controlling the slag discharge amount of tapping and adding a dephosphorizing agent only if the rephosphorization amount in the process can not be accurately calculated. Therefore, in order to make the alloying economy of the added bread iron as good as possible, the amount of rephosphorization at the end point of tapping and refining must be controlled. From the thermodynamic point of view, the main factors affecting dephosphorization are: temperature, slag alkalinity, slag oxidability and slag quantity. However, the dephosphorization factors are changed during the tapping process due to deoxidation alloying, so that phosphorus is returned from the slag into the molten steel.
The reaction formula of rephosphorization is as follows:
2(3CaO·P2O5)+5[Si]＝4[P]+5(SiO2)+6(CaO) (1-5)
[Si]+(FeO)＝FeO+SiO2 (1-6)
due to (SiO)2) Increase to reduce the alkalinity, thereby leading to [ P ] in the molten steel]And therefore, the amount of slag discharged during tapping is reduced as much as possible, thereby reducing the amount of phosphorus returned. The influence of the converter end temperature on rephosphorization needs to be carried out at low temperature, the favorable condition of the dephosphorization is destroyed along with the increase of the converter tapping temperature, the reaction of the dephosphorization reaction formula (1-5) is carried out in the forward direction, the content value of the balance phosphorus in steel is increased, and the total rephosphorization content of the molten steel is increased. The lower the slag basicity and the smaller the slag oxidability, the greater the influence of tapping temperature on rephosphorization. The reasonable control of the tapping temperature is beneficial to inhibiting molten steel rephosphorization. And simultaneously, lime powder or a dephosphorizing agent is added into the steel ladle in the tapping process, so that the phosphorus content is reduced.
In order to meet the requirements of the specified components in the smelting of Q275 steel, the target components are shown in Table 1, and the alloying elements are shown in Table 2;
TABLE 1 target Components
Figure BDA0003185119570000041
When the rephosphorization in the process can be stably controlled within a certain range, determining the rephosphorization amount by controlling the slag amount in the tapping process, and calculating the reasonable phosphorus increase amount of the allowable molten steel according to the step (1-1); in order to ensure the accuracy of the added bread iron amount, when the allowable bread iron amount is calculated, the relationship between the phosphorus content of the bread iron and the phosphorus content of molten steel at the blowing end point and the target phosphorus content of a finished product is considered, and then the added amount of the bread iron is calculated according to the formulas (1-2) and (1-3).
TABLE 2 technical conditions of the alloy raw materials
Figure BDA0003185119570000042
Taking the steel tapping amount of 150T as an example, the adding amount of the bread iron is calculated as follows:
and (3) calculating:
by the formula Δ p ═ pTarget-(pTapping+pComprises+pGo back to) (1-1)
pComprises＝ΣMη×ω[P]η/MGeneral assembly (1-3)
Adding silicon-manganese alloy according to normal
Formula is added from alloy: adding amount (kg/t) of alloy per ton steel, namely (middle limit-end point residual component of steel grade specification)/content of alloy elements and alloy absorptivity, calculating alloy adding amount (1642.5 kg) of 150t steel tapping amount without using iron packageComprises＝(1642×0.001)/150000≈0.000011
pComprisesAccording to percentage, 0.000011 multiplied by 100 is 0.0011%
△p＝0.045-(0.015+0.0011+0.003)＝0.0259
(m1×p1+m2×p2)/(m1+m2)≤pIncrease
m1The steel tapping amount is 150 t; p is a radical of1＝pTapping，pTappingAs end point phosphorus content pTapping0.015 (determined by assay); m is2Adding bread iron amount; p is a radical of2The content of iron and phosphorus in bread is 0.150; p is a radical ofIncrease＝△p＝0.0259
By the formula: (m)1×p1+m2×p2)/(m1+m2)＝pIncrease
m2＝m1×(pIncrease-p1)/(p2-pZeng \u)
＝150000×(0.0259-0.015)/(0.150-0.0259)
≈13174kg
13.174t of bread iron finished product p is added to meet the national standard requirement.
According to the production conditions, a process mode of adding the bread iron after tapping is adopted, so that after tapping, the chemical components of the molten steel can be accurately known through sampling and testing, and favorable conditions are provided for determining the reasonable adding amount of the bread iron. Because the control principles of C, Si and Mn are similar, the recarburization rate is higher than that of silicomanganese, and the C content of Q275 steel is taken as a reference for analysis.
2) Controlling the iron addition of the ladle by taking the carbon increment as the control surface:
TABLE 3 bread iron composition and heating temperature
C Si Mn P S Heating to T
4.2 0.65 0.60 ≤0.120 ≤0.22 ≥800
TABLE 4 composition of converter end-point
Furnace number C Si Mn P S Tapping T
1 0.08 - 0.06 0.015 0.025 1610
2 0.08 - 0.05 0.013 0.022 1617
3 0.07 - 0.08 0.020 0.022 1633
4 0.09 - 0.08 0.022 0.019 1620
5 0.06 - 0.06 0.012 0.030 1625
6 0.06 - 0.08 0.017 0.011 1616
7 0.07 - 0.06 0.019 0.019 1611
And (3) calculating: (m)1×ωc1+m2×ωc2)/(m1+m2)＝Cm(1-4)
m1The steel discharge amount is 150 tons; omegac1End point carbon content 0.08; m is2Adding bread iron amount; omegac2The carbon content of the bread iron is 4.2; cmIs the carburetion amount; setting the target carbon of the finished product to be 0.31;
the end point carbon is 0.08, so that the carbon needs to be enriched by Cm＝0.31-0.08＝0.23
From equations 1-4, m can be derived2＝m1×(Cm1-ωc1)/(ωc2-Cm)
m2＝150000×(0.23-0.08)/(4.2-0.23)
＝5667kg≈5.7t
The addition amount of 5.7t is less than the limit condition of 13.174 t. And realizing deoxidation alloying.
TABLE 5 ingredients after 5t addition of bread iron
Furnace number C Si Mn P S
1 0.318 0.035 0.034 0.0373 0.0403
2 0.337 0.034 0.037 0.0369 0.0411
3 0.364 0.037 0.0036 0.0302 0.0446
4 0.344 0.033 0.033 0.0322 0.0506
5 0.289 0.038 0.031 0.0364 0.0469
6 0.297 0.038 0.035 0.0302 0.0202
7 0.312 0.033 0.032 0.0322 0.0392
TABLE 6 temperature of 5 tons of bread iron
Furnace number End point temperature C The steel discharging temperature is lower The tapping temperature is lowered to DEG C
1 1610 1568 42
2 1617 1567 50
3 1633 1566 67
4 1620 1560 70
5 1625 1570 55
6 1616 1572 44
7 1611 1566 45
As can be seen from Table 5, the content of C in the molten steel after alloying with the tundish iron is less than or equal to 0.35 percent, and the content of P is less than or equal to 0.045 percent, which meet the national standard. From the data in table 6, it is seen that the temperature limitation is satisfied by adding 5 tons of bread iron. Tables 4 and 5 for the comparative ladle alloyed with bread iron resulted in an average increase of 0.016% in phosphorus, 0.236% in carbon, 0.030% in silicon (with ferrosilicon added), 0.028% in manganese and 0.02% in sulphur.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

Claims (4)

1. A molten steel alloying method is characterized by comprising the following steps:
step one, adding surface iron when tapping is carried out in a converter, blowing argon in the whole tapping process, wherein the argon blowing pressure at the bottom of a ladle is 0.25-0.30 MPa, and the argon flow is 270-300 NL/min, and stirring;
adding other alloys into a refining furnace or a ladle to ensure that the alloy content in molten steel meets the steel grade requirement;
the method for calculating the addition amount of the bread iron comprises the following steps:
1) controlling the iron addition of the surface package by taking the phosphorus increase amount as a standard:
phosphorus in molten steel depends on: phosphorus content at the end point of the converter, phosphorus return amount in tapping and refining processes and phosphorus increment brought by alloy,
△p＝ptarget-(pTapping+pComprises+pGo back to) (1-1)
(m1×p1+m2×p2)/(m1+m2)≤△p (1-2)
pComprises＝ΣMη×ω[P]η/MGeneral assembly (1-3)
In the formula: delta p is the maximum phosphorus increment of the molten steel;
ptargetThe target content is the finished product;
ptappingThe phosphorus content is the blowing end point;
pcomprisesIntroducing phosphorus content into the alloy;
pgo back toThe amount of phosphorus returned in the tapping process;
m1is the molten steel quantity, t;
p1the content of phosphorus in the molten steel is percent;
m2adding amount of bread iron t;
p2the phosphorus content in the bread iron is percent;
Mηis the alloy addition, t;
ω[P]ηis the phosphorus content in the alloy,%;
Mgeneral assemblyThe total amount of each alloy;
2) controlling the iron addition of the ladle by taking the carbon increment as the control surface:
(m1×ωc1+m2×ωc2)/(m1+m2)＝Cm (1-4)
in the formula: m is1Is the molten steel quantity, t;
m2is the amount of bread iron, t;
ωc1carbon content in molten steel,%;
ωc2the carbon content of the bread iron is percent;
Cmtarget carbon content,%.
2. The molten steel alloying method of claim 1, wherein the converter tapping temperature is 1640-1680 ℃, and the tapping temperature drop is less than 40 ℃.
3. The method of alloying molten steel as claimed in claim 1, wherein the ladle iron is added when the steel weight is 1/3 of the total steel weight, and the addition is completed when the steel weight reaches 3/4.
4. The method of claim 1, wherein the surface iron is baked in a gas oven for 15min-20min at 800-900 ℃ before tapping.
CN202110859174.3A 2021-07-28 2021-07-28 Molten steel alloying method Pending CN113637822A (en)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110343810A (en) * 2019-07-04 2019-10-18 邯郸钢铁集团有限责任公司 A kind of method of liquid steel pre-deoxidizing in converter tapping process
CN112080682A (en) * 2020-09-23 2020-12-15 宁夏建龙龙祥钢铁有限公司 Method for increasing vanadium content of molten deformed steel bar by using vanadium-containing titanium-containing pig iron block
CN113355585A (en) * 2021-04-27 2021-09-07 红河钢铁有限公司 HRB400E produced by microalloying vanadium-containing pig iron and method

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110343810A (en) * 2019-07-04 2019-10-18 邯郸钢铁集团有限责任公司 A kind of method of liquid steel pre-deoxidizing in converter tapping process
CN112080682A (en) * 2020-09-23 2020-12-15 宁夏建龙龙祥钢铁有限公司 Method for increasing vanadium content of molten deformed steel bar by using vanadium-containing titanium-containing pig iron block
CN113355585A (en) * 2021-04-27 2021-09-07 红河钢铁有限公司 HRB400E produced by microalloying vanadium-containing pig iron and method

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