DE2146355C3 - Refining a steel melt - Google Patents

Description

The invention relates to the application of the measure brown oxide vapors more than balanced,
If the carbon content of the batch, from the

Blowing one or more oxide particles in the weld pool is produced above that in the finished steel Desired metals by means of a sour- 30 noble steel is necessary value, the one-substance-containing Carrier gas which the molten steel in the blow continues until the carbon passes through Unit of time from the oxygen oxidation supplied to the carrier gas is so far away that the value amount to which the molten steel in the unit of time in the finished steel results in the same value, with within to match the amount of oxide particles supplied. this time also hydrogen and nitrogen as well

In the prior art (US Pat. No. 2,502,259), the 35 other undesirable elements, such as silicon and manganese, are used to keep the melt and phosphorus removed or oxidized. If the center temperature, in which the endothermic reaction, the charge, on the other hand, has a lower heat of carbon from the reaction of the oxide particles with the content than is required to produce the desired carbon of the molten steel of the exothermic reaction-refined steel, the heat of the reaction is only so long Carrier gas oxygen is blown in until hydrogen and nitrogen are perfectly removed with the carbon from the molten steel and other undesirable elements are oxy-speaking. For this purpose, the carrier gas has an oxygen content, whereupon the refined steel itself has a content of at least 45%; it is preferred to recarbonize the desired carbon-pure oxygen in an amount of 0.34 to 0.41 m ^{3 in a known manner.}

worked per 1 kg of oxide particles. The advantage of this 45 The measures described can be applied to The procedure shows that the freshly use practically all of the aforementioned types of steel. Process on the order of magnitude with the reaction depending on the specific type of steel desired speed of oxygen freshening expires; the suitable oxides, such as iron oxide, nickel oxide, The disadvantage, however, is that when freshening for chromium oxide, molybdenum oxide, copper oxide, cobalt oxide, Because of the high supply of molecular oxygen, tungsten oxide was added. For carbon steels will Large amounts of brown oxide from the carrier gas - for example an oxide in the form of a hammer blow, Vapors are created above the molten steel, which are then replaced by iron ore or iron oxide dust from dust cleaners Subsequent elimination (FR-PS 11 24 227) great difficulty added, while for corrosion-resistant steels causes problems and costs. Oxides of nickel, chromium, molybdenum, copper, cobalt

The invention is that of the prior art 55 or tungsten or some combination thereof (BE-PS 7 27 735), although known, but not post-possibly with an iron oxide, in order for little workable The problem solved is based on how at least some of the metallic components of the a steel melt with about the reaction speed steels a cheaper raw material to form, Verdigkeit of oxygen freshening can be used.

but without brown oxide vapors above the 60 sub "oxide particles" should be in this co-molten steel appear. hang all grits from relatively coarse to

The invention consists in the use of the grain that is too fine to be understood as dust. For the purpose of this, the above-mentioned measure must of course not be so coarse that the brown oxide vapors cannot be blown in through a lance to prevent the formation of brown oxide vapors; the molten steel, in that it may not be too fine as a carrier gas, so as not to be carried through the molten bath by the oxygen-enriched air with an acidic carrier gas, an impact content of at most 35% in an amount of and simply into the furnace atmosphere ge-0.06 to 0.2 m ^{3 is used} per 1 kg of oxide particles. to be blown. Have proven to be particularly suitable

The following grain sizes were found: maximally ready for the oxidation, and it was pulverized grain under 6.35 mm; at most about 30% added with hammer blow in the following grain size:
0.0104 mm.

To facilitate and accelerate the slag-metal reactions, slag formers such as 5 Lime powder, limestone or fluorspar blown in with the metal oxide or metal oxides, namely either continuously with the same or during one or more selected periods during the process flow. ok

The method according to the invention is described below are explained on the basis of some implementation examples.

example 1

Carbon steel This haramer whipped powder was made by means of

a lance immersed in the weld pool

An electric arc furnace with a capacity of 41 to use compressed air as the carrier gas for 2 minutes was filled with scrap steel, blown in at a temperature of 22.7 kg / min. Of carrier gas were heated temperature of 1550 ⁰ C and formed a slag on the at Normaitemperatur and pressure 2.83 m ³ of air ver molten bath. The weld pool was then needed.

An examination of the weld pool immediately before and immediately after the blowing in showed the following Table, with column 1 indicating the percent by weight before and column 2 the percent by weight after blowing:

C Mn Si SP Ni Cr N ₂ H _a

Grit (Weight percent) (mm) 41 3.17 to 2.41 13.4 2.41 to 1.685 3.5 1.685 to 1.395 6.1 1.395 to 1.193 6.1 1.193 to 0.99 4.5 0.99 to 0.863 6.1 0.863 to 0.0687 11.8 0.687 to 0.508 11.8 0.508 to 0.356 30.6 below 0.356

1 0.39 0.32 0.02 0.033 0.015 0.15 0.09 0.012 5.3 2 0.24 0.25 0.00 0.032 0.013 0.15 0.09 0.008 2.4

This steel should have a carbon content of _{r M ς p N} "

0.24%, so that no recooling is required- 40 ^J (ppm)

was borrowed. The weld pool was then free of slag

made, deodized, a reduction slag extracted ^ 0 40 0 29 0 034 0 004 0 011 3 0
forms and then drained. ''''''

As the table shows, the carbon thus became ² °> ²⁴ ° ^'23 °' ⁰²⁵ ° ' ⁰⁰² °' ^{010 2} ' ⁷
rapidly removed that also the content of nitrogen 45 _{In this case, the steel should} have _{0) 30%} C, and was markedly reduced hydrogen The encryption _{s0 that it rückge by addition of m k pig iron.} driving took place without any visible emission of brown fumes. _kohU ^^ was known _{by dcm> that it was 4} 0, _{c eat} .

held. Brown smoke was not observed.

50 B e i s ρ i e 1 3

Austenitic corrosion-resistant steel

Carbon steel The procedure described in Example 1 was carried out in

a single charge electric arc furnace

The procedure was initially as in. Example 1 55 carried out by Va t and the molten bath carried out again as described and the molten bath again oxidized by blowing in hammer powder with the same grain size as in Example 1, using compressed air of the same grain as in Example 1 by means of compressed air as the carrier gas would. The powder was oxidized as a carrier gas, but in this case an amount of 9 kg / min was blown in for 3.5 minutes under 45.36 kg / min for 3.5 minutes, using a total of 2.97 m ³ Air for what purpose a total amount of compressed air (at normal temperature and pressure) is blown in. It was 10.62 m ³ at normal temperature and pressure and there was no visible brown smoke. One was overpowered. A review of the molten bath, testing the molten bath immediately before and immediately before and after the injection, showed the values given directly after the oxidation before and column 2 gives the values after column 2 the percentages by weight after blowing in,
indicates. The table clearly shows the reduction in

C. 5 Si H S. 3 Ni 6th Cf 0.053 1.1 0.52 0.022 21 46 355 8.66 16.1 0.020 0.05 0.42 0.019 P. 7.48 9.1 1 0.041 2 0.030

oxidizable elements through oxidation. The B e 's t>' e 1 4
The chromium content of the steel has been reduced to such an extent that

that for the desired final analysis of the steel he was named «Austenitic corrosion-resistant steel
was low, so the slag reducing agent

how, for example, ferrosilicon were added, The same procedure as in Example 1 was used

whereby chromium is carried out of the slag back into the bath, but with nickel oxide

was given. After checking, it was found that the powder had a grain size similar to that of the

that the chromium content had risen to 14%. The 15 hammer blows according to Example 1 for the oxidation

Melt was then freed from slag and one used and again compressed air as a carrier gas

Reduction slag formed, whereupon the melt was set and the powder for 2 minutes in a

Reduction slag formed, whereupon the amount of 4.5 kg / min was blown. To press

Melt was eventually drained. If for the air, 0.85 m ^{3 were} consumed here, and it was created

Desired type of steel the other alloy elements - no visible brown smoke. A review of the

elements must be present in larger quantities, melt immediately before and after the oxidation

one could also use suitable supplements of this type resulted in the following composition in weight per-

Adding elements after the reduction slag centers, column 1 again showing the values in front of and

had been trained. Column 2 shows the values after blowing.

C Si S P Mn Cr Ni Mo

1 0.26 0.28 0.005 0.034 0.76 10.8 5.49 0.73 2 0.20 0.10 0.001 0.037 0.38 8.16 9.06 0.77

During the oxidation, the increase in nickel showed. The bath was then ready for oxidation and attrition

that 95% of the nickel is recovered from the nickel oxide from an iron ore sintering plant, which passes through a sieve

were won. Chromium and other alloy with a mesh size of 6.35 mm was sent,

elements were according to the desired steel was in the bath for 3 min with a throughput of

composition in the same way as in Example 3 169 kg / min by means of a

modified. dived lance blown in. As a carrier gas

B is ρ ie 1 5 4o compressed air in an amount of 12.74 m ³ under one

...,. ,,. , _x _,. ",. Pressure of 3.5 kg / cm ^{2 was} used. The oxidation

Austenitic corrosion-resistant steel _{was produced without visible bare vapors} .

Here, too, the same procedure was used as in the case of the weld pool.

Game 1 carried out, with a mixture of 50% checked and contained indirectly after blowing

Chromite sand (ground chrome ore) and 50% urine 45 in percent by weight:
merschlag in the same grain size as in example 1

has been used. Immediately before oxidation ~ ~ ^ ~ ~ ^ ~

the weld pool was checked and it turned out ⁿ '*

a carbon content of 0.75% and a chromium _n " _nn , _{nfU7 nn91 n} ^ _{1 nm} ,

content of 6.18%. After the oxidation, the 50 ° ⁴¹⁵ ° 'contained ³³ ° ⁰³ °' ⁰⁴⁷ ° ' ⁰²¹ °' ²¹ °> ⁰¹⁵

Melt 0.65% carbon and 5.80% chromium, i.e. 0.265 0.20 0.02 0.045 0.015 0.18 0.007
a value that is easily within that for the

The desired steel required chromium content of The bath was then purged, deoxidized, was 5 to 6%. As a result, it can be seen that the chromite sand, which is known to be a reduction slag, forms an inexpensive starting material and is finally drained off,
chromium for the melt resulted and effective

the reduction caused by oxidation of the chromium Example 7
of the chromium content, so that an addition of expensive chromium in the reduction stage An open hearth furnace with a capacity of 2401 was no longer necessary. Here too, in the 1960s, 1461 scrap and 95 t of hot metal did not produce brown smoke from the blowing-in process. charged to a blast furnace. At the end of the melting process, the metal contained 0.70% carbon,

Example 6 with this carbon content 48 minutes after completion

In this one, carbon steel of ^the melting process fell to 0 45%

65 state were 1422.5 kg of iron oxide powder means

• An electric arc furnace was supplied with 37.95 t of 39.64 m ^{3 of} air at a pressure of 3.5 kg / cm ²

Steel scrap and brought to a temperature by a lance immersed in the weld pool.

Heated 1500 ° C, whereby a slag was formed. blow.

The blown Eisenoxid'wies following grit _o to: · *

Decrease / h

Particle size (mm)

(Weight percent)!

3.390 to 1.590 0.7 1.590 to 0.060 15.7 0.060 to 0.025 • 24.5 0.025 to 0.018 3.8 0.018 to 0.015 11.6 0.015 to 0.0105 10.5 0.0105 to 0.0075 24.7

60 min after the * "0.25

Melting

117 min after the ■ -. ' 0.08

Melting - ^,

047

Samples taken from the weld pool at different times during refining showed the following Results:

Decrease / h

(Vo)

At the end of the melting 0.70 18 minutes after the 0.45

Melting

51.5 min after the start of blowing

Melting

57.5 min after the end of the blowing

Melting

} o, 31

0.60 The steel was then drained in the usual manner and potted.

The oxidation occurred with no visible brown vapor over the weld pool.

Examples 8 and 9

Examples 8 and 9 were carried out in order to avoid the limit value for the oxygen content of the carrier gas to represent the prevention of the emergence

ao of brown iron oxide vapors are complied with got to.

In each example, powdered hammer was blown into a single capacity resistance furnace of 204 kg blown in using compressed air as the carrier gas. The air then became like this far enriched with oxygen until brown oxide vapor was observed for the first time, with the proportion of Oxygen in the carrier gas at this point in time is recorded in the table below:

Throughput a b a + b C = b + c Oxygen percentage m 'at to hammer ~ 20% of a in the carrier gas Carrier gas example blow Air flow oxygen total Oxygen- total quantity with smoke per kg sentence throughput throughput amount in of oxygen education Hammer blow (kg / min) with smoke of carrier gas the air with smoke (7o) education education (m '/ min) (m '/ min) (m '/ min) (m '/ min) (m '/ min)

4.54 6.8 9.07

4.54 6.8 9.07

0.368 0.368 0.368

0.368

0.3

0.48

0.057 0.037 0.066

0.042 0.051 0.085

0.42

0.405

0.433

0.411 0.351 0.490

0.074 0.074 0.074

0.074

0.06

0.082 0.13
0.11
0.139

0.116

0.11

0.167

30.5
27.7
31.8

28.0
31.5
35.0

0.093 0.060 0.048

0.091 0.052 0.054

From the table above it can be seen that the formation of smoke between the carrier gas and the oxide affects Throughput at hammer blow between 4.54 started when the oxygen content in the carrier gas is down and 9.07 kg / min and a ratio of about 1: 1 50 approached about 30 volume percent.

Claims (1)

The invention uses the knowledge that Claim: even when using the carrier gas in a close to the ^ Min- required to blow in the oxide particles Application of the measure, when freshening a minimum amount, that is, with an offer of Ij ₁ molten steel by blowing in oxide particles 5 of molecular oxygen from the carrier gas, at the same time one or more in the finished steel desired sam in ^{deficit in the course of refining with the a} metals by means of an oxygen-containing carrier oxide particle comparable to oxygen refining s, gases that the molten steel reaches in the unit of time from the reaction rate, which presumably the amount of oxygen supplied to the carrier gas is due to the fact that at the location of the ^ a common reaction of the molecular oxygen supplied to the molten steel in the unit of time ^ To match the amount of oxide particles for the purpose and the oxide particles with the carbon of the steel § prevent the formation of brown oxide melt under the given conditions / vapors above the molten steel, in that special thermodynamic conditions exist as carriers. % gas optionally enriched with oxygen It is also surprising that despite the blowing in 'Air with an oxygen content of not more than 15 of molecular oxygen in the molten steel 35% in an amount of 0.06 to 0.2 m ³ per 1 kg, a development that was previously regarded as unavoidable Oxide particles is used. brown oxide vapors are absent over the molten steel. The fact that im ao within the scope of the measures described, a noteworthy one There is practically no cooling of the steel melt entry. Should contrary to expectations in the course of the fresh _{f the} process still results in undesirable cooling ΐ the steel melt enter and thus an additional As the supply of heat is required, this would be small disadvantage due to the advantage of not being able to do so