CN101928808A - Method for determining adding amount of alloy in RH refining process - Google Patents

Abstract

The invention discloses a method for determining the adding amount of an alloy in an RH refining process. The method mainly comprises the following steps of: determining the temperature of molten steel and the concentration of free oxygen in the molten steel; calculating the dosage of the alloy serving as a temperature raising agent in the RH refining process; and calculating the adding amount of each alloy according to an initial value and a target value of each alloy element and the target element content of the alloy. An alloy yield is calculated by a self-learning method, so that the input cost of the alloy is lowered and the component control accuracy of the alloyed molten steel is enhanced.

Description

A kind of method of definite RH refining process interalloy add-on

Technical field

The present invention relates to the production and the control field of metallurgical process, determine the method for alloy addition in particularly a kind of RH refining process.

Background technology

The RH refinery practice is most important a kind of in numerous external refining methods, have short, series of advantages such as throughput is big, refining effect good, easy operation of processing cycle, in STEELMAKING PRODUCTION, obtained widespread use, at present the major function of RH has been changed into by original single degassing equipment and has comprised vacuum decarburization, oxygen decarburization, powder injection desulphurization, temperature compensation, uniform temperature and the outer refining unit of the multifunctional furnace that becomes to grade, and is showing significant superiority aspect the ultra low-carbon steel producing.

Along with the user is more and more higher to quality, kind and the performance demands of steel, control accuracy to RH refining treatment process molten steel composition is also had higher requirement, and RH refining treatment technological process is very complicated, the factor that influences molten steel composition is more, and this has more increased the accurately difficulty of control of molten steel composition.

In present RH purified actual production process, operator take relatively more conservative, safe alloying control method often according to operating experience.Particularly, when the kind of determining the adding alloy and quantity, basically only consider the target value that molten steel composition will reach after the alloying, the method of judgement of employing experience and empirical Calculation, the optimization problem of not only ignoring the alloy input cost, and deviation appears in the result of empirical Calculation unavoidably, is difficult to guarantee control accuracy.On the process control strategy, generally carry out coarse adjustment earlier, between the RH carbon period, add the more cheap alloy of price, with the actual value of molten steel composition be controlled at one with the bigger scope of target value deviation in, add alloy once more according to the chemical analysis results of extracting molten steel sample and operator's experience again molten steel composition is finely tuned, make final molten steel composition relatively near target value.

Therefore, the RH refined alloy chemical control system method that adopts more is the experience that relies on operator at present, and the add-on of different-alloy when the angle that reduces cost of alloy is optimized coarse adjustment and fine setting not, both increased steel-making cost, be difficult to guarantee control accuracy again.

A kind of method of calculation of RH refining process interalloy add-on have been introduced in the invention " the alloying control method in a kind of RH refining process " (patent No. ZL 200410024741.X), what it adopted is the linear programming algorithm, total cost with the input alloy is an objective function, with alloying element, impurity element input amount is constraint condition, guarantee the stable of yield of alloy by optimizing the alloy ordering in launching, but do not provide the detailed method of calculation of yield of alloy for the alloy that drops under the hyperoxia voltinism condition.

Summary of the invention

The purpose of this invention is to provide a kind of method of definite RH refining process interalloy add-on, especially provided a kind of method of calculating yield of alloy, it has the advantage that reduces RH refining treatment alloy input total cost and improve the molten steel composition control accuracy.

A kind of method of definite RH refining process interalloy add-on may further comprise the steps:

1) determines free oxygen concn in liquid steel temperature and the molten steel;

2) calculating is as the alloy consumption of intensification agent in the RH refining process;

3) according to the add-on of every kind of alloy of cubage of object element in initial value, target value and the alloy of each alloying element in the molten steel.

Reasonablely be in the method for above-mentioned definite RH refining process interalloy add-on, to be aluminium as the alloy of intensification agent.

Reasonablely be that in the method for above-mentioned definite RH refining process interalloy add-on, related alloy comprises two kinds of deoxygenated alloy and non-deoxygenated alloys.

Reasonable is that in the method for above-mentioned definite RH refining process interalloy add-on, the employing self-learning method is determined the alloy consumption in the RH refining process in step (2), (3).

The method of a kind of definite RH refining process interalloy add-on set forth in the present invention adopts self-learning method to calculate yield of alloy, has not only reduced the alloy input cost, has also improved the control accuracy of molten steel composition after the alloying.

Embodiment

The present invention is a kind of method of definite RH refining process interalloy add-on, may further comprise the steps:

1) determines free oxygen concn in liquid steel temperature and the molten steel;

2) calculating is as the alloy consumption of intensification agent in the RH refining process;

3) according to the add-on of every kind of alloy of cubage of object element in initial value, target value and the alloy of each alloying element in the molten steel.

In step 1, obtain liquid steel temperature and molten steel free oxygen concentration by direct measurement or according to theoretical model or experimental formula, this is the routine techniques in the RH refining production process.

Enter step 2 subsequently, liquid steel temperature and the molten steel free oxygen concentration determined according to step 1 calculate the alloying element consumption that is used as the intensification agent.

In RH refining treatment process because the circulating of molten steel, thereby with conduction, convection current and radiating form to extraneous transferred heat amount, liquid steel temperature is reduced, as not carrying out hyperthermic treatment, be difficult in and reach the target temperature that needs after the RH processing finishes.At present all be by aluminium in the molten steel and oxygen reaction basically, discharge a large amount of heats, thereby make molten steel heating that the chemical equation of aluminium and oxygen is as follows:

$\begin{array}{cc}\left[\mathrm{Al}\right]+\frac{3}{2}\left[O\right]=\frac{1}{2}\left({\mathrm{Al}}_2{O}_3\right)& \mathrm{\ΔH}=-402.6\mathrm{kJ}/\mathrm{mol}\left[O\right]\end{array}---\left(1\right)$

Calculate the intensification amount that the aluminium consumption that heats up should judge at first that molten steel needs,, must when treating processes finishes, free oxygen be dropped to enough low degree, that is to say that the present free oxygen of molten steel nearly all can be removed by aluminium according to the requirement of RH refining treatment.Can calculate according to formula (1), the dissolved oxygen of 1PPm can make molten steel temperature raise 0.05 ℃, and the free oxygen that obtains removing molten steel thus makes the intensification amplitude of molten steel be:

ΔT _DEO＝[O] _OLD×0.05 (2)

Wherein, Δ T _DEOBe the molten steel temperature changing value that deoxygenation causes, unit is ℃; [O] _OLDFor RH handles preceding molten steel free oxygen concentration, unit is PPm.

The oxygen dissolution that is blown into also can produce certain heat in molten steel the time, and its chemical equation is as follows:

{O ₂} _25℃＝{O ₂} _1600℃ ΔH＝53.86kJ/mol[O] (3)

According to formula (3) and (4), the molten steel temperature that the dissolving of oxygen causes is changed to:

$\mathrm{\Δ}{T}_{O2}=\frac{{\mathrm{VOLUME}}_{O2}\×1000\×(117.15-53.86)}{11.2\×C_{\mathrm{PSTEEL}}\×W_{\mathrm{STEEL}}}---\left(5\right)$

Wherein, Δ T _O2The changing value of the liquid steel temperature that causes for the dissolving of oxygen, unit are ℃; VOLUME _O2Be the blowing oxygen quantity in the refining process, unit is a standard cubic meter; C _PSTEELBe the specific heat of molten steel, unit is KJ/t ℃; W _STEELBe molten steel weight, unit is a ton.

But when the refining treatment of reality, not all oxygen is all absorbed by molten steel, therefore should multiply by an oxygen utilization rate coefficient η _O2, the amount of oxygen that its expression is absorbed by molten steel and the ratio of oxygen blast total amount, like this, formula (5) promptly becomes:

$\mathrm{\Δ}{T}_{O2}=\frac{{\mathrm{VOLUME}}_{O2}\×1000\×(117.15-53.86)}{11.2\×C_{\mathrm{PSTEEL}}\×W_{\mathrm{STEEL}}}\×{\mathrm{\η}}_{O2}---\left(6\right)$

In addition, molten steel also has certain temperature drop in treating processes, takes all factors into consideration the influence of above each factor to molten steel temperature drop, and the calculation formula of molten steel heating amount is as follows:

ΔT＝T-T ₀-ΔT _DEO-ΔT _O2+ΔT _n+ΔT _alloy (7)

Wherein, Δ T is the intensification amount that molten steel needs, and unit is ℃; T is the target temperature of molten steel RH processing when finishing, and unit is ℃; T ₀Be the temperature before molten steel RH handles, unit is ℃; Δ T _DEOBe the molten steel temperature changing value that deoxygenation causes, unit is ℃; Δ T _O2The changing value of the liquid steel temperature that causes for the dissolving of oxygen, unit are ℃; Δ T _nBe the natural temperature drop of molten steel in the RH treating processes, unit is ℃ that this value is relevant with the treatment time, can or carry out homing method to former RH refining treatment actual achievement and try to achieve by experimental formula; Δ T _AlloyFor adding the changing value of the liquid steel temperature that other alloy causes, unit is ℃ or to carry out homing method to former RH refining treatment actual achievement and to try to achieve by Theoretical Calculation.

Thus, according to formula (1), can obtain:

W _H-Al＝0.0225×W _STEEL×ΔT (8)

Wherein, W _H-AlFor chemical heat use the aluminium amount, unit is a kilogram; W _STEELBe molten steel weight, unit is a ton.

In actual production, the aluminium of not all adding can both make molten steel heating, therefore should be divided by an intensification aluminium utilization ratio, and its expression is actual to play the aluminium of intensification effect and the ratio of intensification aluminium add-on, and like this, formula (8) promptly becomes:

W _H-Al＝0.0225×W _STEEL×ΔT/η _H-Al (9)

η in the formula _H-AlExpression intensification aluminium utilization ratio can be carried out homing method by former RH refining treatment actual achievement and be tried to achieve.

Consumption when in step 2, promptly calculating aluminium as the chemical heat agent according to formula (9).

Then, enter step 3, according to the initial value of molten steel composition, the add-on that target value is calculated various alloys.In the present embodiment, suppose that with aluminium as deoxygenated alloy, ferro-niobium is as non-deoxygenated alloy, for other alloy, the method for calculation of its consumption are similar, therefore repeat no more herein.Derive according to theory, deoxidation with the consumption of aluminium is:

W _D-Al＝0.001125×[O] _D×W _STEEL (10)

Wherein, W _D-AlBe the aluminium add-on as reductor, unit is a kilogram; [O] _DBe free oxygen concn in the molten steel before the deoxidation, unit is ppm; W _STEELBe molten steel weight, unit is a ton.

Simultaneously, aluminium is also as a kind of alloying element, is used to adjust the molten steel molten aluminium component of acid and the aluminium consumption that adds is:

$W_{e-\mathrm{Al}}=\frac{0.1\×W_{\mathrm{STEEL}}\×({\left[\mathrm{Al}\right]}_{\mathrm{end}}-{\left[\mathrm{Al}\right]}_{\mathrm{old}})}{{\mathrm{\α}}_{\mathrm{Al}}}---\left(11\right)$

Wherein, W _E-AlFor being used to adjust the composition aluminium consumption that the molten aluminium component of molten steel acid adds, unit is a kilogram; W _STEELBe molten steel weight, unit is a ton; [Al] _EndBe molten steel target aluminum concentration, unit is ppm; [Al] _OldBe molten steel initial aluminum concentration, unit is ppm; α _AlBe the content of element aluminum in the metallic aluminium that adds, unit is %.

Therefore, for the consumption of finishing the aluminium that deoxidation and aluminium alloying process need add be:

W _Al＝W _D-Al+W _e-Al (12)

Wherein, W _AlBe the aluminium consumption, unit is a kilogram.

When actual purified deoxidation alloying was handled, not all aluminium all participated in deoxygenation and enters in the molten steel fully, so following formula also should be divided by an aluminium recovery rate, and this recovery rate is the aluminium of participation reaction and the ratio of the aluminium consumption of input.Formula (12) becomes after considering aluminium recovery rate factor:

W _Al＝(W _D-Al+W _e-Al)/η _Al (13)

η wherein _AlConsume the recovery rate (%) of aluminium for deoxidation alloying.

η _AlAdopt the method for self study to try to achieve, concrete calculating thinking is: by before the database formed of RH refining treatment actual achievement in, choose the jar identical with the inferior steel grade of current jar, that working condition is close and the timed interval is the shortest time conduct reference jar, in database, choose some jars with reference to jar, each is averaged with reference to the yield of alloy of jar, and resulting average recovery rate is as the yield of alloy of this jar molten steel.In the deposit process after every jar of smelting finishes,, then deposit it in database as historical data,, thereby finish self study as next reference jar to be selected of new jar time if this jar is that normally jar is inferior.

For close being interpreted as of working condition: for aluminium, oxygen amount in its recovery rate and molten steel and the slag is closely related, and because there are chemical equilibrium in oxygen amount and the dissolved oxygen in the molten steel in the slag, therefore can be with the total oxygen demand in molten steel dissolved oxygen content indirect reaction molten steel and the slag, promptly can whether close with adding molten steel dissolved oxygen content before the aluminium if whether characterizing different jars times molten steel working conditions mutually recently.Simultaneously, also should take all factors into consideration of the influence of situations such as slag is thick, vacuum chamber baking, ladle turnover to yield of alloy.

For ferro-niobium, its add-on is:

$W_{\mathrm{NbFe}}=\frac{0.1\×W_{\mathrm{STEEL}}\×({\left[\mathrm{Nb}\right]}_{\mathrm{end}}-{\left[\mathrm{Nb}\right]}_{\mathrm{old}})}{{\mathrm{\α}}_{\mathrm{NbFe}}\×{\mathrm{\η}}_{\mathrm{NbFe}}}---\left(14\right)$

Wherein, W _NbFeFor being used to adjust the ferro-niobium consumption that molten steel niobium composition adds, unit is a kilogram; W _STEELBe molten steel weight, unit is a ton; [Nb] _EndBe molten steel target niobium concentration, unit is ppm; [Nb] _OldBe the initial niobium concentration of molten steel, unit is ppm; α _NbFeBe the content of elemental niobium in the ferro-niobium, unit is %; η _NbFeBe the recovery rate of ferro-niobium, unit is %.

Because the recovery rate of ferro-niobium is more stable, can try to achieve by former RH refining treatment actual achievement is carried out homing method.

Claims (5)

1. the method for a definite RH refining process interalloy add-on is characterized in that mainly may further comprise the steps:

1) determines free oxygen concn in liquid steel temperature and the molten steel;

2) calculating is as the alloy consumption of intensification agent in the RH refining process;

3) according to the add-on of every kind of alloy of cubage of object element in initial value, target value and the alloy of each alloying element in the molten steel.

2. the method for a kind of definite RH refining process interalloy add-on according to claim 1 is characterized in that the alloy as the intensification agent is an aluminium.

3. the method for a kind of definite RH refining process interalloy add-on according to claim 1 is characterized in that related alloy comprises two kinds of deoxygenated alloy and non-deoxygenated alloys.

4. according to the method for claim 1,2 or 3 described a kind of definite RH refining process interalloy add-ons, it is characterized in that in step (2), (3), adopting self-learning method to determine alloy consumption in the RH refining process.

5. the method for a kind of definite RH refining process interalloy add-on according to claim 4, it is characterized in that described self-learning method with jar inferior with reference that current jar time steel grade is identical, working condition is close and the timed interval is the shortest be learning object.