US1529669A - Method of making chrome steel having various carbon contents - Google Patents

Description

Patented Mar. 17, 1925.

UNITED STATES v PATENT OFFICE.

NAPOLEON PETINOT, OF NEW YORK, N. Y., ASSIGNOR TO UNITED STATES FERRO ALLOYS CORPORATION, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

METHOD MAKING CHROME STEEL HAVING VARIOUS CARBON CONTENTS.

No Drawing.

ticularly it relates to the manufacture of chrome steel rades having such carbon contents as may e desired, particularly as carried out by means of the basic open hearth processes. k

The general practice in making alloy steel, which is familiar. to those skilled in the art of making steel by means of the 2 open hearth process, is as follows:

A charge of pig iron and iron scrap is made in such proportion that when the bath is melted, the carbon content in it will be from about one per cent to 1.50%. To this charge is added limestone, and iron ore. Then the metal of the charge is held in the furnace, and the carbon is gradually oxidized on account of the oxidizin atmosphere existing there. Usually there is a slight silicon content in the bath, which comes from the pig iron or from the scrap, and this usually varies from .75% to 1.25%. Such slight silicon content is oxidized first so that there is no silicon present in the molten bath, and the bath is an oxidized bath.

It is further recognized by the art that any addition of ferrochrome made in lump form will become oxidized. during the time it is melting and being diffused through the molten bath therebycreating a loss in chromium of from 10% to 40%. The extent of this loss depends on the degree of heat existing in the molten bath, or more generallyspeaking, it depends on the amount of iron oxide contained in it.

It is the principal object of my invention to provide a process, which will substantially prevent such loss of chromium, and at the same time provide an inexpensive and efiicient method of making the chrome steel of any desired grade and of any desired carbon content.

Other advantages than those above set forth will be apparent to those skilled in Application filed January 30, 1924. Serial No. 689,566.

the art of making steel by means of the open hearth process.

In carrying out my invention, I follow the initial step of the previous practices of the art, and prepare a charge of pig iron and iron scrap in such proportion that when the bath is melted, the proper amount of carbon desired will be present. I then make an addition to the bath of ferrosilicon of the grade known in the trade as Bessemer ferrosilicon, having a silicon content varying from 10% to 20%. This .ferrosilicon is cast in sha e form in a permanent mold as described in United States Letters Pat ent No. 1,274,360, issued to me July 30, 1918. Suflicient ferrosilicon must be added to the bath to deoxidize it, andin practice, I have found that from one pound to two pounds of silicon added as ferrosilicon is necessary to accomplish this end. When sufiicient silicon has thus been added that fact will be apparent since then the bath'will lay quiet instead of boiling; Since the atmosphere is oxidizing, if the bath is kept as such for a long time, the silicon addition will not only deoxidize the bath but the bath of carbon steel will eventually reoxidize. This deoxidation will tak place according to the equation oxidizes the bath but inasmuch as it has been added in excessive quantities, it will prevent 'any possible reoxidation. The lump ferrochrome which floats in the bath will first become mushy; then it will melt, but it will notoxidize for the reason that the silicon has more aifinity :t'or oxygen or oxide, and consequently will oxidize first, It. is for this reason that the excessive amount of ferrosilicon is necessary.

The addition of the ferrosilicon with the loo.

content of from 10% to 20% will protect the chromium fromoxidation thus giving a better yield. This is the great advantage of my invention. Obviously, as soon as the chromium is melted other additions of ferro allo s such as ferromanganese may be made as esired either into the furnace or to the ladle and then the heat is tapped.

In practicing my process, I add enough silicon not only to deoxidize the bath but also to protect from oxidation the addition of chromium. The condition that enough silicon has been added to thoroughly deoxidize the bath is easily recognized since when that has been done the. .bath then lays quiet or is dead In practice I usually add ferrochrome from five minutes to fifteen minutes after the to ferro'silicon addition has ing a silicon content of from 10% to 20% to kill all boiling action in the furnace and then add ferrochrome to the bath.

2. A process of the character described comprising the addition to a bath composed of pig iron and iron scraphaving the desired carbon content of sufficient ferro'silicon having a silicon content of from 10% to 20% to deoxidize the bath and also to protect from oxidation the added chromium, then adding the desired amount of ferrochrome.

A process of the character described comprising the addition to a bath composed of pig iron and iron scrap having the desired carbon content of suflicient ferrosilicon having a silicon content of from 10% to 20% to deoxidize the bath and also to protect from oxidation the added chr0- mium, then adding the desired amount of ferrochrome, then after the chromium is melted adding other ferro alloys as desired, and then tapping the heat.

In testimony whereof, I have hereunto signed my name.

NAPOLEON PETINOT.