US1846234A - Refining process for producing pure iron - Google Patents

Description

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Patented Feb 23, Il932 M cam-0W NT LOFFICVE iqnniuiln JOHANVAu corny, or Honor Guam:

'nnrinxnc rnocuss FDR, rnonncmo PURE mom .lll'c'illrnwingg. Application filed November 28, 1927,

This ini'cnrion rr-lclcs to u proccssfor producing snbsiunlinlly a pure viron by ovcrblowing :2. previously pr -2pnre l iron both, subscour-oily reducingsthe sonic by minins of u mixture of certain gases and finally carburizing the sonic by directly inlirod ucing one or more snturutei'l hyl'lroccrbons into bhc both.

In processes for the production of steel, which are .huscd upon the principle of a re-,

lining of the charge, mainly inblust reliningr processes both acid and basic and in hearth furnace processes both acid and basic, fci'romnngnulz se or other Incl-cl alloys are usually employed offer the refining period for purposes oi (lcoxydntion.

"lhecc additions cause at the some time o curbonizulion of the but-h and it is not pos sible to make the steel free from oxides and slo ball), which remain from the solid compounds resulting from the reaction between the solid dcoxidction material and the oxygen oi the birth, hitherto was'impossiblc.

The present invention has for its object :1 process according to which itis possible to manufacture iron and steel free from the 11n-- desirable elements phosphorus, arsenic, snl- At the some time lhe phur and the like. metal mannlocnlrcd according to the new process is: free from slugs inevitablev when deoxidized according" to the known processes and it is also lilac clccl-ric steel and electrolytic iron cnlirely safe against the risk of redshorlncss, that is to say free from other gcnrornpounds, I

Till: all processes of manufacturing Steel hitherto in use the blowing and refining has not been continued to eflcctthe complete con1 bust-ion of the nccom lmnying elemcnts, llfi cause the longer the time of refining, the higher rho content of oxygen of the bath which ugzain implies a grrcutcr consumption of costly ferronlloys. At the same time the amount of tho'eleoxillntion-nmtcrial used increoscs the innountof The oxides and slugs rcniaiis'iing in the bath, and also the number l of slag inclusions iii-the finishcd stccl. Thereh ll fore, in ni-miulccluring steel too long arelining or an overblowmg is llVOlClQll. Metallurgists of repute arc of tho opinion filial; the

'overblo'wing in order The removal of these impurities oi the Serial No. 236,371, and in Germany December 14, 1936.,

to remove completely the undesirable elements is purposeless, and that by the basic Bessemer process the content-of phosphorus can only be reduced to 0.05%.

It has been noted, that the refining and blowing in the Bessemer process can with; out danger be carried so for that in the nilieil bath the carbon, pl'iosphorus, manganese and silicon are entirely burnt up, so that the bath only contains iron and ferrous-oxideand that the dangerous ferrous-oxide can be removed by means of a gaseous deoxidation material, The complete removal of the undesirable ele ments (phosphorus, sulphur, arsenic and the like) and the other accompanying elements of the iron by overblowing to a sufficient or;- tcnt therefore is a characteristic featurenfi the invention.

In the case of the acid Bessemer process whercail as is well known, phosphorus cannot be burnt and sulphur cannot be removed because "the slag is acid, the initial raw material must be as free from phosphorus and sulphur as possible. stance carbon, silicon, manganese are burnt by overblowing and finally the bath in the some way as in the basic process consists only of iron and ferrous-oxide.

According to the lawsof the chemical equilibrium it can be shown that; with solid deoxidation materials which again form solid deoxidation products, a purification of the bnthldeoxidation) can be carried only so far as in produce a, certain concentration of the components in quest-ion present in the both. A part of the oxygen remains dissolved in the bath and besides this oxygen, hitherto notrcmovable by any chemical or mechanical means, there remain in the liquid steel also the foresaid residues of the solid The other elements for iii-3J5 the concentration'of the reaction products in the metal bathis permanently zero.

accompanying the iron by overblowing which, as already mentioned, only still con- 1y be avoided, any increase in tains iron and ferrous-oxide is treated with a gas having a powerful reductive action. It is then impossible for oxygen bearing inclusions to remain.

It is easily to be understood that through a metal bath having a high constant of oxyen not every reducing as can be forced.

or instance vapour of nzene which indeed has a very powerful reductive action, would react with the oxygen compounds of the bath according to the following equation 0,11 15Fe0 600 SH O 15Fe that is to say that from one volume vapour of benzene in the converter would result 9 volumes of. carbonic acid and steam.

This enormous increase of volume would cause an explosion and throw the bath out of the converter. An essential feature of the invention, therefore is the employment of a reducing gas burning without increase of volume. Hydrogen although it burns without increase of volume is not proper as a de oxidation-material because its reductive action at higher temperature decreases and at the temperature of liquid iron is imperceptibly small.

It is important that the gaseous mixture introduced suffers no appreciable change in volume when burned, for while an increase causing even a mild explosion must certainvolume would tend to disturb the nice operation of the process and form an element of danger by causing undue boiling up or splashing of the metal. When carbon monoxide is used as a reducing agent in the presence of carbon dioxide and a neutral gas such as nitrogen, the carbon dioxide quenches the tendency of the monoxide to carbonize the bath and prevents explosions, while the neutral gas serves as a diluent and volume balancing means. The desired result attained is that such a mixture burns without'appreciable increase in vol-. ume, reducing the metal without carbonizing the same, and at the temperature of the iron bath, can entirely reduce the ferrous oxide present in the bath.

The task of the carbon monoxide containing gas is therefore exclusively to reduce the ferrous oxide, not to burn phosphorus, manganese or other accompanaying elements which moreover have been removed by overblowing.

Of the various possible methods of manufacturing the pure iron, the following method has proved the best.

In the blast-box of a Bessemer converter 0. second gas inlet is introduced, through which a gas of the above mentioned composition can be forced into the converter.

In the manufacture of pure iron in the blast refining process a charge of pig iron of the same composition as is usually taken in the Bessemer process is refined in usual manner, except that this refining process is not broken off at the customary moment 'when the percentage of carbon, manganese, phosphorus and silicon has reached the amounts usual in the finished but not completely deoxidized Bessemer-steel-bath.

The refining process is carried so far that the percentage of hosphorus has sunk to less than 0.01% and the percentage of manganese and silicon amount to no more than 0.02%. material as pure in phosphorus and sulphur as possible is used, the process then is the same as described in the basic process.

The blast refining time must be fixed in several preliminary tests by means of chemical analysis.

At this stage the air current is cut off and Inthe acid process an initial raw the reducing gas inlet valve is opened. The

reducing gas then enters the iron bath through the last-box and the tu eres. The

gas current is forced. through the ath till all oxygen is removed from the bath that is to say until a test piece taken out of the bath is completely free from red-shortness.

In the open hearth process the charge is also melted and refined in the usual manner and then further refined (over-fined) for a long time. The determination of whether the refining-time is sufiicient is a ain made by means of chemical analysisn melting and refining in the open hearth furnace the time can be worked out according to the direct (ore)-or scrap-method or according to any other method. After the refining is finished the liquid steel is brought into a converter as described above-only in this case of course the blast-inlet can be omitted-and is deoxidized by reducing gas being forced through the bath as above describe To remove the sulphur completely the bath can be worked in the well known manner with a double slag-la er.'

With regard to the p osphorus and sulhur content in the acid open hearth process it must be worked with an initial raw material as in the Bessemer process.

By the use of the new process a perfectly de-oxidized bath of pure molten iron is obtained.

The production of Siemens-Martin steel can be carried out in a similar way.

The pure iron thus obtained, which is not only characterized by its purity but also by its homogenous texture, ductility and power of resisting corrosion, is suitable for extensive use in the technical world, and also with special advantage as a raw material for the man- Efacture of alloyed or unalloyed steel of any ind.

The pure iron obtained by the process above described may be recarbonized if this should be desirable. In the processes already known such. recarbonization has been effected with the aid of manganese or other alloys containing a high percentage of carbon. These at the same time effect the introduction of large quantities of manganese or other metals into the steel bath, the presence of which is either undesirable or else renders the steel useless for the purpose for which it is intended.

Therefore, in the process according to this invention, the final step, namely the recarburization is effected by means of gases or vapors having a carbonizing effect which gases are passed through the bath. It is well known that certain of the saturated hydrocarbons, commonly known as the paraffin series are more readily volatilized than others, and it is an established fact that they have a very etficient carburizing efiect on the iron bath.

In said series the parafiins such as pentane and hexane are representative, being found in commercial form in petrol, benzene and the like, and mixtures thereof, and naturally, such members of the series are examples of those which may be used with the desired ef feet. It is of course understood that, whatever members of the series is used, the same is not normally a gas but is volatilized completely by merely introducing the same in the last step of the process.

I claim l. The refining process for producing iron by blast and open hearth refining methods which, after initially refining a bath of m0lten iron in known manner, consists of the combined sequence of steps, namely, of first over-blowing the iron bath in order to introduce an excess of oxygen and thereby obtain a mixed bath of substantially pure iron and iron oxide, subsequently reducing the bath to practically pure iron by means of a noncarbonizing gas of substantially constant volume, which is actively reductive at the temperature of the bath including a mixture of carbon monoxide, carbon dioxide and nitrogen, and finally carburizing said bath by introducing a saturated hydrocarbon into the same until said bath contains a predetermined amount of carbon.

2. The refining process for producing pure iron by blast and open hearth refining methods which, after initially refining a bath of molten iron in known manner, consists of the combined sequence of steps, namely, of first overblowing the iron bath in order to introduce an excess of oxygen and thereby obtain a mixed bath of substantially pure iron and non-carbonizing gas of substantially iron oxide, and subsequently reducing the bath to practically pure iron by means of a constant volume, which is actively reductive at the temperature of the bath including a mixture of carbon monoxide, carbon dioxide and nitrogen.

, 3. The refining process for producing pure iron by blast and open hearth refining methods which, after initially refining a bath of molten iron in known manner, consists of the combined sequence of steps, namely, of first forming a new slag layer upon said bath in order to protect the same, then overblowing the iron bath in. order to introduce an excess of oxygen and thereby obtain a mixed bath of substantially pure iron and iron oxide, subsequently reducing the bath to practically pure iron by means of a non-caronizing gas of substantially constant volume, which is actively reductive at the temperature of the bath including a mixture of of oxygen and thereby obtain a mixed bath of substantially pure iron and iron oxide,

subsequently reducing the bath to practically.

pure iron by means of a non-carbonizing gas of substantially constant volume, which is actively reductive at the temperature of the bath including a mixture ofcarbon monoxide, carbon dioxide and nitrogen, and finally carburizing said bath by introducing a saturated hydrocarbon into the same until said bath contalns a predetermined amount of carbon.

DR. HERMAN JOHAN VAN ROYEN.

same, then overblowing the iron bath in order to introduce an excess