US2644746A - Process for refining steel with pure oxygen - Google Patents

Description

July 7, 1953 H. HAUTTMANN PROCESS FOR REFINING STEEL WITH PURE OXYGEN Filed Aug. 22, 1950' Mama/Z Patented July 7, 1953 PROCESS FOR REFINING STEEL WITH PURE OXYGEN Hubert Hauttmann, Linz (Danube), Austria, as- ,signor to Vereinigte Oesterrei'chische Eisenund Stahlwerke Aktiengesellschaft, Linz (Danube) Austria Application August 22, 1950, Serial No. 180,808

In Austria August 31, 1949 The use of pure oxygen in the refining of steel has been known since the introduction of the Bessemer process. The reasons why oxygen has not been more Widely used are firstly the high production costs of oxygen, which until quite recently made its application impracticable for the refining of steel; and secondly, the inadequacy of available methods for introducing the oxygen into the melt. Thus, for instance, attempts to use oxygen in bottom-blow converters failed because the tuyres or the refractory material became choked, and water-cooled, copper tuyeres had an insufficiently long life. The same applied to attempts at introduction .of the oxygen by side blowing.

These disadvantages can be obviated if, as already suggested by Bessemer, the oxygen is introduced into the bath from above. C. Schwarz, German Patent 735,196, Class 183, Group 8, ex-

pected to obtain a sufficient speed of reaction by using exceptionally high gas velocities, above the speed of sound and blowing the oxygen from above to a considerable depth into the steel bath.

Experiments have meanwhile shown that the ill-success of attempts made hitherto to introduce the oxygen into the steel by top blowing are due to the fact that the slag covering the steel, or the reaction products resulting from the action of the oxygen, prevent a direct contact between the surface of the steel and the jet or flow of oxygen directed thereon, if the pressure used is insufiicient to ensure penetration. Even when the oxygen jet was directed obliquely, it roved impossible to free the surface of the steel, since with an obliquely directed jet the motion of the slag is such that it is continuously drawn to and over the point of contact.

The method of directing the oxygen jet with supersonic velocity on to the bath and maintaining its kinetic energy at a sufficiently high value to ensure penetration through the slag cover deep into the bath, as attempted by C. Schwarz, obviously increases the cost of using oxygen to a not inconsiderable extent. Were it possible to reach the bare surface of the steel with lower pressures and using other means, an appreciable economic advantage would be obtained.

It has been found that the area of contact of a vertically directed gas jet with the bare surface of a steel bath can be kept free from slag without using such high kinetic energies that the jet penetrates deeply into the steel, if a rotary motion is imparted to the issuing gas jet by a suitably formed nozzle or tuyere. The rotating gas jet causes the slag cover at the point of impact to 4 Claims. (01. 75450) rotate similarly while simultaneously the scum resulting from the reactions presents an aerodynamically sufiicient impact surface to ensure transmission of the rotary motion of the gas jet, to the slag. The centrifugal force generated by this rotation, causes the slag to be driven away from the impact area, the impact energy of the jet obviously aidin this process.

As soon as the surface of the metal has been laid bare by this eifect of the centrifugal force, an exceedingly rapid reaction takes place between the oxygen and the metal of the bath, without the gas jet penetrating into the metal.

The nozzle requires to be of particular shape and differs in this respect from existing, known types of nozzles for producing gas J'ets with a rotary motion (e. g. U. S. Patent No. 723,501 of Thofehrn) because with them the issuing gasthe oxygenis completely reabsorbed on the way between the nozzle and the surface of the metal. Already upon leaving the nozzle, the jet encounters splashes of iron and ferrous slag from the boiling steel, so that only a part of the gas reaches the impact area and there reacts immediately with the steel. It has, therefore, been found advisable to obtain the rotary motion by the use of a number of circularly arranged, obliquely blowing nozzles. A spirally-blowing nozzle can be used alternatively if the nozzle is located quite close to the surface of the metal.

The accompanying drawingshows two forms of the nozzle suitable for operating the process of the present invention.

Fig. 1 is a sectional view of the first form of nozzle, along the line MO' of Fig. 2.

Fig. 2 represents an end view of the nozzle head.

Fig. 3 shows a second form of nozzle in vertical section.

Fig. 4 is an end view corresponding to Fig. 3.

In the example represented by Figs. 1 and 2, the nozzle head B is provided with obliquely directed ducts or passages A. The nozzles are arranged in the head B in such manner that the projections of their axes b (Fig. 2) are tangent to the impact circle a.

In the second example-according to Figs. 3 and 4, the jet is caused to rotate by guide blades or vanes D provided at the mouth of the nozzle head C, the shape of the said guide blades or vanes being such as to cause the issuing jet to rotate.

I claim:

1. A process for refining steel with pure oxygen, comprising directing a stream of oxygen onto the surface of the melt and rotating said stream about its axis to cause rotation of the slag at the point of impact and free the surface of the metal to enable direct contact between the oxygen and the melted metal.

2. A process for refining steel with pure oxygen, comprising directing a stream of oxygen onto the surface of the melt and spirally rotating said stream about its axis to cause rotation of the slag at the point of impact and free the surface of the metal to enable direct contact between the oxygen and the melted metal.

3. A process for refining steel with pure oxygen, comprising directing a plurality of spirally disposed jets of oxygen under pressure and rotatin said jets about their axes onto the surface of the melt to cause rotation of the slag at the point of impact and free the surface of the metal to enable direct contact between the oxygen and the melted metal 4. A process for refining steel with pure oxygen, comprising directing a plurality of circularly disposed, obliquely directed spiral like jets of oxygen under pressure and rotating said jets about their axes onto the surface of the melt to cause rotation of the slag at the point of impact and. free the surface of the metal to enable direct contact between the oxygen and the melted metal.

HUBERT HAUTTMANN.

References Cited'in the file of this patent UNITED STATES PATENTS Number Name Date 33,949 Lane Dec. 1'7, 1861 1,032,654 Brassert July 16, 1912

Claims (1)

1. A PROCESS FOR REFINING STEEL WITH PURE OXYGEN, COMPRISING DIRECTING A STREAM OF OXYGEN ONTO THE SURFACE OF THE MELT AND ROTATING SAID STREAM ABOUT ITS AXIS TO CAUSE ROTATION OF THE SLAG AT THE POINT OF IMPACT AND FREE THE SURFACE OF THE METAL TO ENABLE DIRECT CONTACT BETWEEN THE OXYGEN AND THE MELTED METAL.

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