DE1508168B2 - METHOD AND APPARATUS FOR REFRESHING PHOSPHORUS-CONTAINING BIG IRON - Google Patents

Description

1 2

The invention relates to a method and to a) that the converter during the first blowing direction for freshening phosphorus-containing crude phase in a manner known per se in an upright position iron remains at rest in two blowing positions by means of an oxidizing gas,

phases with an intermediate _{slag removal between b) that the} intermediate slag removal with a coal

of the first and second blowing phase, the oxygen _{content of the bath being between 0.7 and 1.7} »/ ₀

rende gas is carried out in both blowing phases together with powder

shaped or lumpy slag formers on the '

Bath in a symmetrical, about its longitudinal axis c) that the converter at the beginning of the second blow-rotating Converter by means of a non-immersing phase in rotation in a manner known per se Lance is blown. io offset against the horizontal in an oblique

It is known (French patent specification 1 219 089) that the position is pivoted between 15 and 25 °

Phosphorus pig iron in the way to fresh, with a speed of between 20

that in two blowing phases the bath is rotated with the oxidizing up to 30 revolutions per minute,

the gas lime and / or soda as a slag former d) that in the course of the first three quarters of the second

in the form of powder or in pieces or granules 15 blow phase the lance against the horizontal in

is added, wherein lying between the two blowing phases _e j _{nem zw} j _sc hen 35 and 90 °

a detox is carried out and the inclination is carried out and during the last quarter

drive through the total duration of the second blowing phase by means of a rotatable converter

can be performed. Oxygen supply either through reduction in size

It is also known (French patent 20 there _d blowing pressure or 1218 043 by using a), in a method for refining lance smaller usable diameter phosphorus pig iron with two blowing phases in reduced, and that during this period of the first phase of the oxidizing gas in the bath the lance is inclined so that the oxygen is blown in by means of a non-immersed lance, blown superficially onto the bath, the converter in the upright position at rest 25 _the lance against the horizontal in one position, and during the second fresh phase the converter is _{inclined at} 15 and 45 °, preferably at 20 °, at an approximately horizontal angle,
In a further embodiment of the invention, a lance 30 which is not immersed in the bath is blown onto the slag during the first blowing phase. in a manner known per se, one of oxygen and

It is also known to use in refining phosphorus, a gaseous fuel of high calorific value

containing pig iron directed a flame generated with oxygen and gaseous form, which - as with oxygen-

gem fuel, such as B. natural gas, operated burner lances known - does not penetrate the metal bath,

lance to use (USA.-Patent 3 202 201) 35 In an advantageous embodiment of the invention

and the oxygen flame on the slag layer, sodium carbonate briquettes are added to the bath,

to be directed in such a way that they do not get into the metal bath consisting of powdered sodium carbonate and a

penetrates (British Patent 823 996). Binders with metallurgical tar in such a way

It is also known when steelmaking is set that it is completely at that point in time

made of phosphorus-rich pig iron are melted in the second blowing 4 °, in which the blowing for the

phase to add sodium carbonate or the decoction is interrupted.

treatment by an increased blowing speed. According to the invention, the foaming of the

accelerate, at the same time by adding slag by blowing in the oxygen jet

Alkali halides or lime powder a foaming of suspended sodium carbonate powder can be controlled.

the slag is reduced (French patent 45 In an advantageous manner according to the invention depending

scripture 1133 958). Ton of treated pig iron three to 10 kg

It is also known (French patent specification sodium carbonate to be introduced.

1124 851), in steel production a rotatable converter for carrying out the invention

To use converter, which in addition to an appropriate method is essentially thereby Rotation axis vertical axis can be tilted. 5 ° marked that he was in a known manner

In this known rotary converter, which is designed to be rotationally symmetrical, its inner wall

for dephosphorization and cooling are conically expanded from the bottom to the hood,

Supplements generally in pieces in front of and with the angle of the cone generating against the

added during blowing. This can be between 10 and 25 ° in relation to the longitudinal axis of the converter a rapid wear of the refractory lining 55 is preferably 18 ° that it is against the

lead. Neck has to be closed conical hood, the

The invention is based on the object of providing an apex angle of this cone between 70 and 130 °, a method and a device which is preferably close to 90 ° at the outset, so that it creates a cradle of the type mentioned with partial use of method steps known per se in planes perpendicular to the longitudinal axis of the converter to create, which has 60 orderly raceways and one of the cradle the disadvantages of known methods - namely the supported drive motor and that the cradle is provided with uneven texture of the steel produced in fixed bearings resting journals, and the wear of the lining - not on common axis of rotation perpendicular to the convergence and an economical and technical opti- terlongitudinal axis is arranged.
mum results. 6g Excessive foaming of the slag in the

According to the invention, this object is avoided by the first blowing phase

the combination of the following process steps results in a sufficiently liquid state from the start

solves: is brought, namely by being on the slag

directing a flame generated from oxygen and a gaseous fuel with a high calorific value, which does not penetrate the bath, but rather merely heats the slag.

The fuel and oxygen for combustion can be through a special lance or can also be fed through the main blowing lance, which in the latter case has heating channels.

The flame can advantageously by means of small, obliquely directed against the bath surface Gas jets are formed.

By these measures it is possible to regulate the extent of foaming of the slag to control the burner output. A reduction in the burner output results in less heating of the Slag and thus a stronger foaming result. In the opposite case, you get by increasing the burner output a reduced foaming. By adding iron oxide, the slag can also can be made more fluid and less foaming.

In the event that you want to free the pig iron bath very quickly from phosphorus, it is necessary to Increase the activity of the slag by adding sodium carbonate to it, using tar as a binding agent pressed into briquettes. The briquettes are sent to the converter at a time by means of a chute fed that they are melted just at the moment in which the blowing of the first Fresh phase has ended. .

The sodium carbonate can also be in powder form, optionally mixed with powdered lime are supplied suspended in the oxygen jet. This soda supplement combats the foaming of the Slag and can even suppress this completely if it is in the bath together with the lime The amount of soda introduced is sufficient for this. A suitable supply of soda can therefore cause foaming the slag can be kept within certain limits. For this purpose 3 to 10 kg of sodium carbonate are used per ton of treated pig iron either in briquette form or in the form of an oxygen jet suspended powder added.

The first refining phase is terminated when the carbon content of the bath / ", is preferably from 1.2 to 0.9 reduced ° / ₀ value lying on a 1.7 to 0.7 °. This point in time is determined as a function of the amount of oxygen blown into the bath, which in turn is measured by a flow meter of known type.

A simple chemical calculation, the result of which is obtained from the previous processes If the results are corrected, the total amount of oxygen can be determined very easily, which is to be introduced into the bath during the first fresh phase in order to increase the basic material content, for example to a value between 1.7 and 0.7%.

However, since the relevant dephosphorization and decarburization rates are not exactly known, it is not possible to conclude with absolute accuracy the carbon content that was obtained after the injection of a predetermined amount of oxygen from the knowledge of the amount of oxygen blown in. ' ^s

In the event that at the end of the first fresh phase a carbon content lying between narrow limits is to be achieved, it is necessary to carry out a carbon content determination shortly before the end the first fresh phase. The following procedure is advantageously used:

Taking into account the previous processes, the process is used to lower the carbon content for example, calculated up to 1.5% of the amount of oxygen to be introduced into the bath. '

The blowing is stopped, the lance is withdrawn, and when the converter is lowered, a ίο Metal sample taken. This sample is subjected to a rapid carbon determination, e.g. B. by means of a Carbometer, subjected; furthermore, the phosphorus content is determined by means of a quantitative spectrograph, it's correct. · '

The specific carbon and phosphorus content of the bath is calculated by calculation or by means of Tables determine the amount of oxygen still to be blown into the bath in order to keep the metal to the prescribed level Bring levels of carbon and phosphorus. Is the carbon content determined by means of the sample higher than 1.5%, the converter is brought into the vertical position and the lance is reinserted and a sufficient amount of oxygen recorded to be blown in so that the carbon content is decreased to approximately 1.2%, whereupon the blowing is stopped. The converter will then lowered again, the bath is slagged off and the transition to the second fresh phase takes place.

If, on the other hand, the carbon content of the sample is below. 1.5% that is how you go after the bath was also skimmed off, immediately to the second .Fresh phase over.

To carry out the second fresh phase, the converter is lowered so that it is slightly against the horizontal direction is inclined, with its longitudinal axis against the horizontal one preferably between 15 and 25 ° above the same inclination.

The converter is then rotated around its longitudinal axis set in rotation at a speed between 20 and 50 revolutions per minute. Then the second lance is inserted into the converter and the one to terminate the Fresh amount of oxygen still to be supplied is blown into the bath. In the oxygen jet are more advantageous Way slag-forming substances such. B. Lime with or without soda and iron oxide additives in powder form suspended.

In this connection it should be noted that the greater the size, the better the fresh reactions is the speed of rotation of the converter.

The slag formers can also be advantageous

Way to be introduced in the form of grains, fed by means of a mechanical centrifuge Device in the from the oxygen jet. hit metal zone.

As in the first fresh phase, it can also be used Increase their activity Soda briquettes are introduced, if a very low weak final phosphorus content should be preserved. ':

It has been found to be advantageous that from the beginning of the second fresh phase during one preferably the inclination of the converter is between half and three quarters of its total duration and to regulate that of the lance so that the oxygen jet penetrates deep into the bath, preferably near the converter neck. The deep penetration of the oxygen jet into the bath and the rotation of the

In this case, converters considerably accelerate the fresh reactions.

This deep penetration of the oxygen jet into the bath near the converter neck also offers the great advantage that oxidized metal is thrown against the wall and the bottom of the converter is reduced and that thereby the corrosion and wear of the refractory lining slows down will.

During most of the second fresh phase, the end of the lance is tilted towards the horizontal . inclined at an angle between 35 and 90 degrees, the preferred value being close to 45 ".

To reach the end of the. Mastering the fresh process is preferred reduced the oxygen supply during the last quarter of the total duration of the second fresh phase, either by reducing the blowing pressure or by using a lance from smaller usable width. In addition, during this period the lance advantageously becomes so inclined so that the oxygen hits the surface of the bath, around the inclusions dispersed in the mass to enable outsourcing. To do this, the lance is tilted between 15 and 45 ° from the horizontal . lying angle, preferably at an angle of 20 °, inclined. The blowing will stop as soon as that A registering flow meter indicates that the intended amount of oxygen has been added to the bath. In At this moment the rotation of the converter is interrupted and the lance is withdrawn. At the same time, a metal sample is taken in order to 'determine the composition by means of a rapid analysis determine. If necessary, a short supplementary blowing is carried out. The purification and The steel is poured out according to the procedure customary in Thomas steelworks.

The method according to the invention is carried out in an advantageous manner. means of a symmetrical converter, the inner wall of which extends from the Base extended to the hood in the shape of a cone of revolution, the angle of the generatrix with the Longitudinal axis is between 10 and 25 ° C and preferably close to 18 °. The conical hood closes against the neck too, the angle at the apex of this cone being between 70 and 130 ", preferably in the Is close to 90 °. . '

The converter is supported by a socket or cradle with the aid of raceways that lie in planes perpendicular to the longitudinal axis of the converter. the Rotation of the converter around its longitudinal axis is carried out by means of a motor carried by the cradle. The cradle itself is provided with pins resting in fixed bearings, their common axis of rotation is arranged perpendicular to the longitudinal axis of the converter. With this measure, the converter The load-bearing cradle can be tilted in such a way that it brings it into a vertical or lying position.

In the following the invention is explained in more detail with reference to two exemplary embodiments, which the production of steel with 0.100% "carbon content... '· ■" ■.; ..

B e i s ρ i e 1 1

A symmetrical converter with a full bottom is used to carry out the fresh process, which can be rotated about its longitudinal axis by means of a rotary drive mounted on the cradle; the converter rests in the cradle on tracks that are arranged in planes perpendicular to the converter axis are. This cradle can be pivoted around two coaxial pins in the manner of a conventional converter will.

At the beginning of the process, the converter is loaded with 28 t of pig iron, approximately 7 t of scrap iron and 500 kg Lump lime charged.

ίο The pig iron introduced contains 3.5% C, -1.9% P, 0.4% Si and 0.300% Mn. After erecting the pear, which is blocked in its cradle, the vertical lance is lowered and oxygen is supplied at a rate of 100 Nm ³ / min. (Normal cubic meters per minute at 0 ° C and 760 mm of mercury) and blown in ^{under an effective pressure of 12 kg / cm 2.} During this blowing, granular lime is continuously introduced into the converter at a rate of 190 kg / min. For this purpose, a vibrating distributor and a supply line are used, which throws the lime into the bath zone, which is hit by the oxygen jet. The blowing is stopped after about 14 minutes, after which 1,385 Nm ^{3 of} oxygen and 2,640 kg of granulated lime with a content of 2,240 kg of effective CaO have been blown into the bath. were introduced. The air blown through the lance 1385 Nm ³ oxygen of 99.5% purity lead to the bath with consideration of the losses to ³ oxygen in the Konverterabdämpfen 1,315 Nm. During this first phase, carbon burns to form CO and CO ₂ in a ratio of 70% CO and 30% CO ₂ . The lance is now raised and the converter is turned over. Then the phosphorus-rich slag is removed, which contains 23% P ₂ O ₅ and 6% iron. A scoop sample of the metal is taken for the spectrographic determination of phosphorus and carbon, and the bath temperature is then measured using an immersion thermocouple. It is found that the metal still contains 1.2% C and 0.15% P and its temperature is 1,580 ° C.

Now 2,900 kg of scrap are brought in. The converter is inclined so that its longitudinal axis forms an angle of 20 ° with the horizontal, the neck being higher than the floor, and the pear at a speed of 28 rev / min. set in rotation. An oxygen lance is introduced through the neck, the blowing pressure of the oxygen being 3 kg / cm ² and the supply being 40 Nm ³ / min. amounts to. After about 14 minutes of blowing, 580 Nm ^{3 of} oxygen were blown into the bath and 335 kg of granulated lime were introduced. After these 14 minutes, the blowing is interrupted for a final check of the composition and the temperature of the metal. If necessary, if the desired composition is not achieved, blowing is resumed for a few seconds.

The final composition of the steel contains

0.100% C, 0.020% P, 0.100% Mn and below 0.003% N at a temperature of 1600 "C ..." It should be noted that the pig iron in the course of the Frischens has undergone a desulfurization of 70% and the sulfur contained in pig iron to 0.050% has passed into the steel with 0.015% .. '..

After the freshening process is complete, the lance is withdrawn and the casting is placed in the metal pan made by icin in the convector neck made pouring hole.

The steel jet flowing into the pan is poured 340 kg of freshly prepared ice cream with a manganese

7 8

content of 50 ° / ₀ added. This is how the manganese sodium carbonate is introduced in powder form. To

content of the steel increased to 0.400 ° / ₀ . these 7 minutes the blowing becomes final

The slag is stored in the pear for the following examination of the composition and the tempe-

Process retained. temperature of the metal interrupted. One finds 0.100 ° / ₀ C,

The balance of the fresh process described is 5 0.014 ° / ₀ P, 0.100% Mn and one below 0.003 ° / ₀

the following: 'lying nitrogen content, with the temperature

For a charge of 1000 kg of pig iron, 247 kg of 1600 ^° C. were required.

Scrap in the first phase and 103 kg of scrap in the After completion of the refining process, the

Second phase introduced, which withdrew a total lance and the casting in the steel ladle Dispatch of 1350 kg results. 1220 kg of steel passed through a pouring hole made in the converter neck won. So the outcome of the process was done. The steel flowing into the pan

340 kg of freshly melted iron are poured into the beam

1220 · 100 _ OQ> ₀ , a manganese content of 50% added. It will

1350 '. so the manganese content of the steel is increased to 0.400 ° / ₀ .

15 The slag will be in the pear for the following

Retain the various stages of the freshening process just described.

Fresh process have the following duration: The inventive method has above all the

",. ,.-or ,, · great advantage of being effective in moving the bath

Charging with 28 t of pig iron _{takes place during the entire} refining process.

i? u ° . 20 As a result of the constant movement of the bath

. , / 2 t lime ^ w. ^en a physico-chemical equilibrium between

Blisters in the first stage. . .. 14 minutes _meta " _{and smack during the whole} treatment,

Tee off, spectrographic PM - _{like Martin} . _{Process is present} . _{This results in}

fung temperature measurement 10 minutes _immediately that the final properties of the generated

Loading with 2.9 t scrap 4 minutes to master _{2 $ steels with much greater accuracy}

Bubbles in the 14 minute second phase _are procedures known as ^ _{the michm.} Further-

abschheßende examination and temperature _{through a wjrd überma} SSI _ge wear lining

temperature measurement for 5 minutes of _{the converter} prevented.

Pour into the pan 5 Μιημίεη

Total duration of the process 62 minutes 3 °

Claims (6)

Claims: Example2 · 1 w c u τ? ■ 'u u u 1 n- 1. Process for freshening phosphorus-containing The same converter as in the first example is often used with pig iron by means of an oxidizing gas and a two-phase blowing process with an intermediate deslagging process, which is very similar to the first example, is carried out. between the first and second blowing phase, whereby the converter, which contains the liquid slag from the previous pouring of the oxidizing gas in both blowing phases, is slag-forming with 281 raw materials with powdered or lumpy iron, approx. 7 t scrap iron and 200 kg lump lime sent to the bathroom in a symmebeschickt. The pig iron introduced contains 3.5 ° / ₀ C, 40 Irish converters rotatable about its longitudinal axis, 1.9% P and 0.4 ° / ₀ Si. blown by means of a non-immersing lance. The vertical lance is lowered and oxygen, characterized by the combination, is applied at a rate of 100 Nm ³ / min. under an effective nation of the following process steps: blown in pressure of 12 atm. The oxygen jet ent- a) that the converter remains in suspension during the first blast holding a mixture of pulverized 45 phase in a manner known per se in the upright position and sodium carbonate in a ratio of 1.8 kg, mixture per Nm ³ des blown oxygen. b) that the intermediate slag removal is interrupted after 14 minutes, ■ carbon content of the bath between 0.7 and during which time 1400 Nm ^{3 of} oxygen, I ₅ 7 ⁰ / o is carried out in the bath, 2360 kg of lime and 140 kg Sodium carbonate introduced 5 ° c) that the converter was at the beginning of the second blow. The lance is withdrawn, the converter phase is rotated in a known manner and the slag is removed. At the end offset against the horizontal in one of these first phases, the metal contains 1.2 ° / oC and an incline between 15 and 25 ° .swiveled 0.08 ° / ₀ P, and its temperature is 1580 ° C. "is and with a speed of rotation 2900 kg of scrap are now brought in. The pear 55 between 20 and 50 revolutions per minute. is rotated to 5 ° below the horizontal with lower than that, Neck inclined on the floor. d) that in the course of the first three quarters of the The pear is at a speed of 28 rev / second blowing phase the lance against the balance-min. set in rotation. A right-hand oxygen lance between 35 and 90 ° is inclined through the neck with an inclination of 45 ° against the 60 ■ ■ angle and inserted during the last horizontal line. The oxygen blown by the lance into a quarter of the total duration of the second blowing bath contains in suspension a phase the oxygen supply either through a mixture of powdered lime and sodium carbonate in a reduction of the blowing pressure or through a ratio of 0.58 kg per Nm ^{3 of} the blown turn of a lance with smaller useful oxygen. The blowing pressure is 6 at, and the 65 bar diameter is reduced and the supply is 80 Nm ³ / min. After about 7 minutes of blowing the lance so inclined during this period, 580 Nm ^{3 of} acid became so in the bath that the oxygen was blown onto the surface of the material and 310 kg of powdered lime and 28 kg of bath were blown, with the lance against the Horizontal inclined at an angle between 15 and 45 °, preferably at 20 ° will. 2. Fresh process according to claim 1, characterized in that during the first blowing phase on the slag in a manner known per se one made of oxygen and a gaseous fuel flame generated by a high calorific value is directed, which - as known with oxygen lances - does not enter the metal bath. 3. Fresh method according to claim 1 or 2, characterized in that the bath sodium carbonate briquettes are added, which are made of powdered Sodium carbonate and a binder with metallurgical tar are so composed, that they are completely melted at the point in time in which the blowing to detoxify is interrupted. 4. Freshly process according to claim 1, characterized in that the foaming of the slag is controlled by blowing in sodium carbonate powder suspended in the oxygen jet. 5. Fresh process according to claim 3 or 4, characterized in that per ton of the treated Pig iron 3 to 10 kg of sodium carbonate are introduced. 6. Converter for carrying out the method according to one or more of the preceding Claims, characterized in that it is rotationally symmetrical in a manner known per se is designed, its inner wall expands conically from the bottom to the hood, the The angle of the cone generating line to the longitudinal axis of the converter is between 10 and 25 ° and preferably 18 ° is that it has a conical hood to be closed against the neck, the The tip angle of this cone is between 70 and 130 °, preferably close to 90 °, that it is a cradle with arranged in planes perpendicular to the converter longitudinal axis raceways and one of the Cradle-borne drive motor and that the cradle with bearing journals resting in fixed bearings is provided, the common axis of rotation is arranged perpendicular to the converter longitudinal axis.