US1137681A - Process of refining steel and producing high-phosphorus slag. - Google Patents

Description

UNITED s'rarns PATENT OFFICE.

ALBERT voetnn, or Mar anna-Germany, ASSIGNOR r0 'rnn FIRM or DEUTSCH- LUXEMIBURGISCHE BERGWEBKS- UND HT'J'TTEN-AKTIENGESELLSCHAFT, or nonr- MUNZD, GERMANY.

PROCESS OF BEFINING' STEEL AND PRODUCING HIGH-PHOSPHORUS SLAG.

No Drawing.

To all whom it may concern Be it known that I, ALBERT VfiGLER, a citizen of the German Empire, residing at Dortmund, Germany, have invented certain new and useful Improvements in Processes for Refining Steel and Producing High- Phosphorus Slag, of which the following 1s a specification. 1

This invention relates to a process for producing a high grade steel and slag containing a high percentage of soluble phosphates in an open hearth or electricfurnace.

In practice it has been found that the chances of obtaining ahigh percentage of soluble phosphates are most favorable in the first part of the refining process and that this high percentage of soluble phosphate 1s always lost toward the end of the process in the finishing of the charge.

Now the present process has for its'object to effect a complete conversion of the phosphoric acid into its soluble form during the treatment of iron for the purpose of obtaining steel of .any desired quality in one and the same hearth, without removing the metal bath. from the furnace prior to finishing and without interrupting the process at any stage.

According to this invention the process mainly consists in retaining the slag upon the metal bath until it is sufficiently enriched with phosphoric acid, then removing the finished slag by blowing while the metal bath remains in the furnace for the refining process.

Now in carrying out the process in a stationary furnace certain operating difficulties are encountered. Among these may be mentioned in the first place that it is difiicult to produce the tapping hole for the slag,which is frequently in a veryfoaming condition, and that this is moreover dangerous for the workmen who are in charge of this operation. Further it is not always easy to provide the tapping hole at such height as to insure the complete removal of the slag without residues remaining in the furnace. These difficulties and drawbacks are obviated according to the present invention by carrying out the process in a tiltingfurnacei In a furnace of this kind the bath may at any time be brought to such a level that on the one hand the slag may be completely and quickly removed with the aid of blast, and

Specification of Letters Patent.

on the other hand the metallic charge may at any convenient moment be prevented from flowing out by a return movement of the furnace. Thus the slag may be obtained without any content of iron whatever, whereby its quality is highly improved.

In all metallurgical processes it is of the greatest importance to shorten andto restrict as much as possible all auxiliary operations such as the removal of slag. Now according to the present invention the time for the removal of theslag is considerably shortened when the process carried out in a tilti'ngfurnace is so conducted that the tilting is effected simultaneously with the blowing operation. It has been found that in effecting the tilting and blowing simultaneously the whole mass of slag is immediately brought into liquid condition and passes through the tapping hole in the form of a Patented Apr. 27, 1915.

Application. filed April 10, 1912. Serial No. 689,855.

it has been found to have the desired per- 7 centage of soluble phosphates, whereas the term finishing slag denotes that slag which remains in the furnace after the metal has been tapped off.

Whereas hitherto the finishing slag produced in the known process and always containing'a certain amount of phosphates had to be removed from the furnace, accord ing to the present process the finished metal bath may be tapped off from beneath the finishing slag while this slag itself remains in the furnace. It is therefore possible to recover the content of phosphates in the finishing slag by using it for enriching the content ofphosphates in the primary slag of the subsequent charge for producing the finished slag of this charge. Apart from the recovery of the content of phosphates in a high grade form and the production of a high quality steel, the losses in time, heat, and iron due to the usual tapping or coating of the slag are also entirely overcome owing to the slag remaining in one and the the same furnace.

The process is carried out in the following manner: The furnace is charged in a known manner with scrap and pig iron either in a cold or liquid condition with the necessary additions of lime and ore. As soon as the charge is in molten condition, and the slag has become sufficiently liquid and has attained the proper percentage in soluble phosphates, it forms the finish-ed slag and is immediately removed from the furnace by blowing it off with the aid of compressed air or gas or a mixture of air and gas, simultaneously tilting the furnace. In order now to finish the metal, which has remained in the furnace after the finished slag has been blown off, the furnace is tilted back into its initial position, the blowing air is turned off and news/additions of lime and ore are made for the purpose of removing from the metal any residual phosphorus that had remained therein after the removal of the finished slag. TV hen the metal is in its finished condition. it is tapped off by tilting the furnace from beneath the slag which has been produced by the additions above referred to. During the tilting operation as the metal is run off this slag gradually descends so that after the whole of the metal has been removed, the whole of the slag remains in the furnace without any part of it passing away with the metal. 1e furnace is now returned to its normal position and a fresh charge of pig iron and ore with the necessary additions is made. Now during the further working of the fur 'nace with this fresh charge the slag which remained in the furnace, or finishing slag after the metal bath has been tapped ofi', is now used to enrich the new slag forming on the fresh charge whereby again a high grade slag rich in phosphates is obtained as a valuable product in the process. In this manner the process may be continued constantly yielding a high grade steel of the quality of Martin steel, and at the same time a slag which is at least equivalent to Thomas slag.

What if claim is 1. The process for the manufacture of steel low in phosphorus and a slag high in soluble phosphates in an open hearth or electric furnace, comprising partially refining the molten metal with a basic slag until the slag is high in phosphorus, then removing the phosphated slag from said furnace while retaining the steel in the furnace, adding a fresh charge of basic slag forming material substantially free from phosphorus to said partially refined steel and completing the refining process thereby removing phosphorus from said steel and forming a partially phosphated slag, and then removing the refined steel while leaving the partially phosphated slag in said furnace for the partial refining of a subsequent charge of steel.

2. A process for the manufacture of high grade steel and of slag rich in soluble phosphates in an open hearth or electric furnace, consisting in retaining in the furnace a partially phosphated slag from a prior operation, adding to the furnace a charge of unrefined metal and partially refining said metal with said slag until the latter has attained the desired percentage in soluble phosphates, then removing the finished slag by blowing while the metal bath is retained in the furnace for the finishing operation, and then completing the refining of the steel with a different slag.

3. A process for the manufacture of high grade steel and of slag rich in soluble phosphates in an open hearth or electric furnace consisting in retaining the slag on the metal bath until it has become suihciently liquid and has attained the desired percentage in soluble phosphates, then removing the finished slag by blowing, while the metal bath is retained in the furnace, making fresh ariditions of slag-forming materials for removing from the metal any residual phosphorus, tapping off the finished metal from beneath the finishing slag, leaving this lat ter slag in the furnace in order again to enrich it with phosphoric acid by the next charge to form the finished slag of this charge which is blown ofi' metal. bath is retained finishing operation.

4*. A process for the manufacture of high grade steel and of slag rich in soluble phosin the furnace for the phates in a tilting furnace consisting in retaining the slag on the metal bath until it has become sufficiently liquid and has attained the desired percentage in soluble phosphates, then removing the finished slag by blowing while the metal bath is retained in the furnace, making fresh additions of slag-forming materials for removing from the metal any residual phosphorus, tilting the furnace fortapping oft the finished metal from beneath the finishing slag, tilting back the furnace into its initial position, leaving the finishing slag in the furnace in order again to enrich it with phosphoric acid by the next charge to form the finished slag of this charge which is blown ofi again while the metal bath is retained in the furnace for the finishing operation.

5. A process for the manufacture of high grade steel and of slag rich in soluble phosphates in a tilting furnace consisting in retaining the slag on the metal bath until it has become suiiiciently liquid and has attained the desired percentage in soluble phosphates, then removing the finished slag by blowing and simultaneously tilting the again while the slag, tilting back the furnace while the metal is retained in the furnace, tilting back the furnace into its initial position, making fresh additions of slag forming materials for removing from' the metal any residual phosphorus, tilting the furnace again for tapping oifthe finished metal from beneath the finishing furnace into its initial position, leaving the finishing slag in the furnace in order again to enrich it with phosphoric acid by the next charge to form the finished slag of this charge which is blown off again while the metal bath is retained in thefurnace for the finishing operation. v

6. InVthe making or refining of steel in a furnace, the -method which consists in treating the steel in successive heats with slags each of which overlaps from one heat to the next.

7. In the making or refining of steel in a furnace, the method which consists in providing a heat of metal with a dephosphorizing slag consisting in part of a previously used finishing slag, pouring this slag ofi when the desired dephosphorizing has been effected without removing the metal, and providing a newfinishing slag for said metal. I

In testimony whereof I afiix my signature in presence of two witnesses.

ALBER voeLER.

Witnesses AUG. V