US1940341A

US1940341A - Treating iron baths

Info

Publication number: US1940341A
Application number: US383069A
Authority: US
Inventors: Bansen Hugo; Lobbecke Karl
Original assignee: Krupp Stahl AG
Current assignee: Krupp Stahl AG; Fried Krupp AG
Priority date: 1928-08-14
Filing date: 1929-08-02
Publication date: 1933-12-19
Anticipated expiration: 1950-12-19
Also published as: AT127359B

Description

Dec. 19, 1933. H. BANSEN EHL ,94o,34

TREATING IRON BATHS Filed Aug. 2, 1929 2 Sheets-Sheet- 1 F' 1. WWW/%WWW WWWW n 2. F'g. 3.

Dec. 19, 1933. BANSEN El' AL 9 3 TREATING IRON BATHS Filed Aug. 2,' 1929 2 shans-Sheet 2 COLD AIR O W vvA s'ra GAS Es i PREHEHTER PREHEATED AIR . Patented nec. 19, 1933 Ari-:Nr OFFICE' 1.9,341 TRATING IRON BATHS Hugo Base, Rleinhausen-'n-iemersleim, and- Karl Lbbecke, Rheihausen, Germany', assignors to Fried. K-pp Aktien'gesellsclaft,

Friedrich-Alfred-Hutte, Rleinhausen, .Ger-` many Application August 2, 1929, Serial No. 383.069,

and in Germany August 14, 1928 8 Claims.

The invention relates to a process for treating iron baths in steel producing furnaces;

As' well known, the process of fining the material by the action of "an oxidizing flame upon j the surface of the bath and through the intermediary of the slag cover takes place very slowly when the bath is at rest. Furthermore the heat transmission is very slow. In order to accelerate these processes a mechanical movement of the o bath by stirrng, rocking or circulating -has been employed and, further, an increased contact with oxygen is caused by blowing-in air or supplying ore.

The ore causes a motion of the bath only dur- 16 ingthe decarburization. Since it is fed intermittently and in irregular size, an utilization of the irregularly developed carbon monoxide by after-combustion is impossible'. Furthermore, the government of the charge becomes uncertain in 20 fining by means of ores.

According to the invention water is injected into the bath itself which measure aifords several advantages. If the water is injected with suflicient speed, the injection tube is protected. Furthermore, a highly valued oxygen bearer is thus introduced into the bath and, finally, a continuous movement of the bath is caused by the constant violent development of hydrogen gas.

By splitting off the oxygen in this fining operation by water less heat is consumed for 1 kg. of

oxygen than in fining by ore.. Furthermore, this quantity of heat may be fully converted to useful heat by combustion above the bath and more particularly a great useful heat drop can be produced !5 by preheating the combustion air up to 1200 degrees by the waste heat, the hydrogen being preheated to an average temperature of 1450 degrees C., so that a great portion of the heat is recovered for the process. Finally, the regular supply and [0 uniform distribution of the water makes possible The bath may have any depth and any desired 'portion of a bath can be brought to seethe so that the process can be employed also' in the openhearth fmace when'the charge will not start 5 seething. Furthermore. in applying the proc ss to the Thomas or Bessemer process the charge can be treated as long as desired by heating the bath by the after-combustion of the gases developed and correspondingly regulating the quantity of combustion air. In this manner a notably higher working temperature is obtained than for instance by the after-combustion of the carbon monoxide in a converting process, owing to the dilutionof i the gas by the nitrogen of the fining air being dispensed with. I

The combustion airgis to be conducted so as to come to eflicacious contact with the gas that escapes from the entire surface of the bath. The water may be fed by the above-mentioned tube in a. full jet or the tube may be a double walled structure through the outer jacket of whichthe water `is fed, in'order to obtain suitable muzzle velocities.

A particular advantage resides in the voluntary supply of the water both as to quantity and time so that the course of the fining action and of the after-combustion can be exactly regulated and the progress of the charge carefully observed according to the development of the gas.

Any want of heat can be compensated for by addition of fuel. so' In carrying out the described process simple iron tubes have been found to be` of short life only so that the process might be rendered un-' economical due to the high consumption -of these tubes. This short life of simple iron tubes is due to the prevailing conditions of heat transition and heat conduction. For, the heat transition from the agitated bath to the tube is about equal to that of water to the tube wall, that is amounts about to 2000 to 3000 thermal um'ts, and will be near the upper limit, that is 3000, due to the violent motion of the bath and to the volume of the tube being far smaller than thatof the bath which thus does not undergo any drop oftemperature. If it would be possible in practice to expose the' entire length of the tube to boiling water, which would give a heat transition of 4000 to -6000 thermal units, then a long life of the tube would be Secured, because in this case the heat conductivity of iron would have an insulating eifect owing to the-high heat transition prevailing on both sides. Now as the present process provides only the application of a comparatively small quantity of water, this method is not feasible. Hence, the heat transition on the water side is at best equal to that on the side of the iron bath and consequently, the tube will be heated up to the mean of the bath and water temperature or more highly. Therewiththe temperature the tube is exposed to arrives in the 110 I range where the properties of strength of iron become nearly zero, so that the tube is no' longer capab'le of resisting the water pressure and mechanical stress and soon will burst. its portions no longer cooled melting off. 4 v

This drawback can be eliminated by the following four measures.

' of the tube so that the time-till its destruction 'may consist in applying makes possible a' practically and economically satisfactory' execution of the process.

d. By introducing water without a tube.

In the accompanyng drawings are iliustrated several embodiments of the means for carryi out the described process, in which drawings Figure l shows a 'water-injecting tube in longiv tudinal section,

Figure 2 is acorresponding cross section, v

Figure 3 is' a cross section through a modified water tube,

Figure 4 isa similar section through another modified tube, v

Figure 5 is the elevation of a third modified tube, and

Figure 6 shows an appliance adapted to carry out the process by means of a movable tube.

A protection of the water tube by reducing or rendering more difficult the heat transition from the bath to the tube, as mentioned above under a can be obtained in various ways attention being paid to the prevailing special conditions, that is to the expansion of the tube and the violent; mechanical stress and blows to which.

the tube is exposed. So for instance a simple insulation by means of tube-shaped fire bricks has proved unsatisfactory. A good protection, however, is obtained by using a hot stickinz thickly liquid slag, which slag coating has to be protected. against solidifying and chipping off by preventing it from cooling during the whole operation. To this end the slag coating preferably is applied to the tube as a liquid slag immediately before introducing the tube, and is completed from time to time by raising the tube during the' operation so 'that new slag will stick thereto from the slag cover ofthe bath; If this protective coating, which in part consists of the content of the bath' itself, possesses the right thickness, a state of balance is obtained between the heat supplied and the heat led oil', whereby the water supply is Secured. Another method to the tube a suitable insulating mass e. g. by means of a spraying gun, or by other means.

Now,- as the tube may be heated up to a comparatively high temperature in spite of the described protection whereby its strength may be considerably reduced, itwill be of advantage to provide means for protecting the tube from bending down. This may be done by fltting the tube with a reinforcing member on the endangered portion such as an U-iron, L-iron or flat iron, as illustrated in Figures 1 to 41:, where an iron bar a, b or c of suitable section is provided within the tube. As such an iron bar perma- .other hand no danger exists nently remains at the temperature of the water supplied that is below degrees, its strensth is maintained. Care must be taken, however, that the iron bar rests on the tube wall only on a few points so that no accumulation of heat and an increased stress of the tube can take place.

An older method of supplying gaseous, vaporous and liquid substances consisted in blowing them in through nozzles provided in 'a wall'of the container, because when the temperature of the bath amounts to considerably more than 1000 degrees, a simple s'upply through metallic or refractory tubes is impossible in the course of time. This supply through nozzles, however, requires a troublesome tilting or rolling of the entire container and, moreover, the quantity supplied can be varied only within narrow limits. Finally, the supply of a .fining means requires special containers or furnaces fltted with the above supplying nozzles.

In contradistinction thereto thepresent method enables these substances to be supplied to a melting bath of high temperature by means' of simple tubes'without the container needing be adapted thereto in any way.

The invention resides on the following perception: v

In spite of the considerably higher heat transition from a bath to the tube than from the agent passing through the tube, a certain time elapses until the tube is heated to its critical temperaure. Furthermore, the destruction of the tube by melting or burning begins at the place of deepest immersion that is at its muzzle, as here the cooling action upon the tube wall is the feeblest due to the supplied agent on this place already being at higher temperature. On the for the tube when to a certain slight extent, in which case the agent in the tube is not heated to any considerable extent. The present method therefore provides an interruption of this heating and recooling of the tube always shortly before the said critical temperature is reached. This is obtained by so far retiring the tube from the bath while the liquid agent .continues to be supplied, that 'a de-accumulationv of the' heat of the tube wall takes place and the agent which then has its original low temperature emcaciously cools also the muzzle of the tube. When for 12: instance the agent is supplied in liquid state, the conditions of heat transltion in the bath itself are approximately equal on both sides, but above the bath the transition of heat within the tube is 20 to 100 times greater than outside. Hence, a violent cooling of the tube wall takes place very quickly.

In .order to protect the tube from destruction, it has therefore to be raised and lowered periodically, the maximum amount of immersion being determined according to the stream velocity .of the agent, the dimensions of the tube, the frequency of the perlod's, and the temperature of the bath. i

In raising the tube always portions of the bath 14 will adhere to the tube the heat of which portions will be led off so that the attack of the bath heat first strikes this protective layer whereby a further protection of the tube is obtained. To attain an emcacious protection of 14 this kind that is by a portion of the bath itself, it has proved advantageous to flrmly wind asbestos cord around the tube on the portion to be dipped before using it, in order to cause the insulatmg bath layer more easily to stick.

dipped only error instance the supp y of the iquid agent an ordinary melting Iurnace. the depth oi of hioh permits a dipping stroke ot cm.. is established by means of ta" is wound on these tubes tor a length 'of 1 m., this winding being doubled near the muazie for alength of 15 em. with a supply ot liquid ot aslitersperminutaastrokeoisotoio cin., and a dpping trequency of to per minute'the tubes withstand destruction, as tests ve proved. ;In

6 one form o; apparat's !or practicing method is illustrated.

the vessel containing the metal bath w the tube ,f is dipped' which is proo' -its length to be dipped with the insu- ,suchasasbestosorthelike. Precombustion air isadmitted intothe space the bath in the vessel through p rta p channel q surrounding the top o! the The preheated air is supplied to the q through an inlet pipe h leading from preheater Ic. The eon'bustion gases pass oi! the vessel through a flue i leading through preheater Ic, where their beat is imparted to cold air supplied to the preheater. In order allowthetubettoberai'sedandlowered e preventing the exit oi!` waste gases around theopeningsinthetopotthevessel In mg. s there is shown, by way of example, a hydraulic deviee comprising a cylinder 13 and pisten 14 connected by rod 15 with the tube f. A pressure fluid is admitted to the cylinder below which periodically admits the pressure iluid !rom pipe'' through port 19 to s e s and alternately tained by increasing the heat abmrbing capacity of the tube by introducing the water into the bath by means o! scrap in the form of billet pieces asusuallysuppliedtothebath. Tothisend these 'pieces are provided with a suitable bore.

Furthermo-e, an emcacious protection oi' the asoresorlime,andsupneoessaryiiningwater.

following asatisi'yingresutmoreparticuo! limited' depth. Iu order apowertul'deeompositionof hydrogenandoxygenthemuazle !Igureksodesignedthatthe Asbestoseordotmmindiameter.-

'arises in the tube causing a premature destruction. To this end the'contraction coemcient to so be applied has to be so determined that the passage area o! the tube is not narrowed.

Finally a reduction ot the dipping depth oi' the tube due to burning or melting oi! can be lessened by giving the tube a coiied shape, as also shown in Figure 5, whereby further a desirable more violent agitation oi the bath is obtained due to the water leaving the tube tangentially.

What we claim and desire to secure by Letters Patent is:- I

1. Process of treating an iron bath to convert it into steel, which comprises introducing water inliquid stateinto the bathinsuchamanner as to cause decompositon thereot, and burning the combustible gases of dec'omposition by supplying combustion air immediately' above the surface o! the bath.

'2. Process of treating an iron bath to convert it into steel, which comprises introducing water 3. Proeess o! treating an' bath to convert it. into steel. which oomprises introducing water inliquidstateintothebathin suchamanner as to cause decomposition-thereot, and burning the combustible gases of deeomposition by supplying combustion air immediately above the surface o! the bath, and preheating the combustion air by the waste heat of the process.

4. Process of treating an iron bath to convert it into steel, which comprises coating an ordinary iron tube with a hot liquid slag, introducing one end oi'-said tube into the bathabeiore the slag cools, and feeding water in liquid form through said tube into the iron bath.:

5.`Process of treating an iron bath to convert it into steel, which comprises coating an ordinary m iron tube with a hot liquid slag, introducing one end of said tube into the' bath before the slag cools, ieeding water in liquid form through said tubeintothebath,maintaininga coveringoi slagon the bath, and intermittently renewing the slag coating* on said-tube by withdrawing the tube i'rom the bathinto the covesing of slag.

6. Process of treating an iron bath to eonvert it into steel, which comprises spraying a hot liquid slag coating onto 'an ordinary iron tube, introducing one end of said tube into the bath before said'coating cools and ieeding water in liquid !om thro said tube into the bath.

'1. Process of treating an iron bath to convert it into steel, which 'comprises injecting liquid water into the bath'through a tube inserted into the bath, periodically partially -withdrawing the tube from the bath while maintaining the flow of water through the tube," and re-inserting the tube to the tull depth atter it has cooled.

8. Process o! treating an iron bath toeonvert it into steel, which comprises winding a cord ot retractory material around an ordinary iron tube,

'dippingoneendotsaidtubeintothebatm teed ing water in liquid form througipsaid tube into the bath. and periodically raising the tube to cause substaneesfrom thebathtoadhere thereto.

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