US2222805A - Manufacture of ferrotitanium alloys - Google Patents

Description

Patented Nov. 26, 1940 PATENT OFFICE MANUFACTURE or FERROTITANIUM ALLOYS 1 Jerome Strauss, New York, N.- Y., and HolbertEarl Dunn, C

rafton, Pa.. assignors to Vanadium Cornotation of America, New York, N. Y., a corporation of Delaware No Drawing.

Application November 25,- 1939,

Serial N0. 306,179

10 Claims. (01. 75- -11) o For the purpose of lowering the carbon content,

The present invention relates to the manufacture of ferrotitanium alloys, and more particularly to the manufacture of medium carbon ferrotitanium alloys. Ferrotitanium alloys containing under .5% carbon are generally classified as low carbon ferrotitanium, those containing from .5% to 5% carbon as medium carbon ferrotitanium, and those containing over'5% carbon as high carbon ferrotitanium. It is to the medium carbon ferrotitanium alloys, namely, those containing 0.5% to 5% carbon, that the present inven-. tion relates.

.This application is a continuation-in-part of our copending application, Serial No. 114,830, filed December 8, 1936.

Ferrotitanium alloys are added to steel in order to deoxidize it. It is desirable, particularly when deoxidizing steel having a low carbon content, to employ ferrotitanium with a carbon content sufliciently low so that it does not unduly increase the carbon content of the steel. It is taining up to 30% or even greater amounts of titanium, with a carbon content below 5%.

In the usual process of producing high carbon ferrotitanium, that is, ferrotitanium containing, say, 7% to 8%.carbon and 15% to 18% titanium, a charge of titanium ore such as ilmenite, steel scrap and coal is melted in an electric furnace. The alloy so produced has a titanium to carbon ratio between about 2:1 and about 2.5:1. For addition to certain types of low carbon steel, such product does not have a high enough ratio of titanium to carbon so that it can be used without unduly raising the carbon content of the steel.

In accordance with the present invention, we

add 'to the ordinary charge commonly employed in the production of high carbon ferrotitanium;

such for example as theichargeabove referred to, materials which lowerthe carbon content and raise the titanium content. In some cases the steel scrap may be omitted from the charge.

we employ materials such as baddeleyite (Z'rOz), beryl (3Be0.AlaOa.6Si0z) or any other form of" refractory materials containing a substantial amount of one or more of the oxides of zirconium or beryllium. For example, we may use zircon (ZrOaSiOa) brazilite .(ZrOa) or zirconium and-titanium bearing beach sands or their partially purified products, which may contain about 15 to 50% ZrOz, 10 to 65% T10: and 10 to 40% $102. The refractory materials containing considerable amounts of silica are particularly applicable where it is desired to pro-. duce ferrotitanium alloys containing substantial amounts of silicon. The preferred refractory we shall refer to baddeleyite for purposes of conciseness, it being understood that any other refractory ,material containing a substantial amount of one or more of the oxides of zirconium or beryllium may be employed in its place.

It is believed that the addition of baddeleyite to the charge serves several important functions.

(1) It produces additional slag which protects the melted or niushy charge from absorbing carbon from the electrode. (2) It aids in forming a refractory skull "or.

bottom of a metallic titanium composition which prevents the melt from picking up carbon from the carbon lining'of the furnace.

(3) It acts to regulate the current flow from the electrode to the charge, making it more uni form, thereby providing hotter metal and a more uniform rate of reduction. It has been established inthe production of: ferrotitanium alloys that the hotter the alloy is, the lower is its car bon content. This lsin spite of the factthat theoretically one would expect a hotter metal to pick up more carbon-than a cooler one.

(4) The constant exposure to the reducing action of localized concentrations of carbon used as reducing agent causes continual reduction of the zirconium content of the baddeleylte to metallic zirconium. The zirconium so reduced from the baddeleyite aids in reducing the titanium ore.

Whether or not the functions and manner of operation ascribed to the use of badqeleyite are entirely fulfilled in actual practice. -we have skull or bottom is as follows:

found that its use results in a. medium carbon ferrotitanium.

In addition to adding baddeleyite or other refractory material to the charge, we preferably add material containing manganese or silicon, or both. The use of a material containing manganese or silicon is not indispensable in carrying out the process but is of considerable advantage, particu-' larly where the ferrotitanium alloy is to contain high percentages of titanium. The manganese may be supplied in the form of manganese ore or ferro-manganese. The silicon may be added as commercial silica rock or silica sand or ferrosilicon. We believe these materials act as fluxing agents, since they definitely aid in increasing the titanium content of the ferrotitanium and in regulating the content of titanium to maintain it more uniform from tap to tapthan is the case in other prior processes. We believe that these materials act in the following manner to increase the titanium content of the alloy and maintain the titanium content more constant from tap to tap. When a charge of titanium ore such as ilmenite, steel. scrap and carbonaceous reducing agent, in the proportions of about Pounds Ilmenite 320 Steel scrap 290 Rice coal 210 is melted in an electric furnace without the use of either baddeleyite or manganese or=silicon, the ferrotitanium alloy, as previously stated, will con tain approximately 15 to 18% titanium and 7% to 8% carbon, the titanium to carbon ratio being about 2.5:1. This is a highcarbon ferrotitanium. In the production of such high carbon ferrotitanium, or in fact in the production of a medium carbon ferrotitanium, a certain proportion of the charge forms a skull or bottom on the carbon lining of the furnace. This bottom contains about 50% titanium, 10% carbon and 35% iron; that is, the titanium bears a ratio to the carbon of more than 4:1, which is a much higher ratio than the ratio of titanium to carbon in the alloy actually tapped from the furnace. An actual analysis of a Per cent Titanium 51.06 Silicon .98 Carbon 12.39 Aluminum 1.51 Iron 33.80

Total 99.74

We have found that the addition of a material containing manganese or silicon or both to the charge has the effect of fiuxing or lowering the melting point bf this high titanium bottom, so that a portion of it may be melted and mixed with the molten alloy above it, thereby increasing the ratio of titanium to carbon of the tapped alloy. This operation of lowering the melting point and flushing out the high titanium to carbon ratio bottom or skull is referred to herein as bringing up bottom.

The addition of baddeleyite to the charge appears to aid in the formation of the skull or bottom of high titanium to carbon ratio material, which formation of skull or bottom is referred to herein as laying down bottom. By the proper regulation of additions of baddeleyite and manganese orv silicon, the bottom may be eitherlaid down or brought up, or continuously laid down and continuously brought up so as to produce the the following is a typical mix charged into an 800 kilowatt carbon-lined electric furnace operating at 48 volts, using a single electrode with a bottom return, the furnace being of a type commonly employed in the manufacture of high carbon ferrotitanium: 1

Pounds Ilmenite 320 Steel scr p 290 Baddeleyite 210 Rice co l The \ferrotitanium alloy tapped after melting this charge at a temperature of at least about 2000 0., say 2100 to 2250 G, contains about 15% to 18% titanium and about 3% to 5% carbon, the ratio of titanium to carbon being from about 3:1 to 6:1. In addition, the alloy also contains small amounts of silicon, manganese and zirconium. The production of this alloy is maintained until a suflicient thickness of skull or bottom has been produced so as to effectively prevent the alloy from absorbing carbon from the carbon lining of the furnace. The subsequent charges are then modified by the addition thereto of manganese ore or other manganese-containing or siliconcontaining material. If manganese ore is employed, itmay be used in the amount of about 40 pounds when a charge as described is used. It will be seen that the charge which is used after the bottom has been formed contains both baddeleyite and manganeseore, in addition to the usual charge of titanium ore, steel scrap and carbonaceous reducing-agent. The bottom or skull previously formed will be substantially the composition previously referred to, except for the introduction of a small amount of zirconium, containing about 50% titanium, 10% carbon, 5% zirconium and 30% iron, the ratio of titanium to carbon in the bottom being approximately 4:1 to 5:1. The addition 'of the manganese ore brings up-some of this bottom, so that the alloy tapped from the furnace contains approximately 17% to 25% titanium and from 2% to 5% carbon, the ratio of titanium to carbon usually approximating 4:1 to 8:1. In addition, the alloy also contains small amounts of silicon, manganese and zirconium. The additions of baddeleyite and manganese-containing material are regulated to maintain the protecting skull or bottom in the furnace and to produce the desired composition of ferrotitanium alloy.

Instead of forming the bottom of high titanium to carbon ratio material as described by eliminating the manganese-containing material from the first charge or charges, we may provide a bottom for the carbonlined furnace by lining the furnace with material produced in a separate operation. For example, we may operate a furnace in the usual manner, that is at a temperature of the order of 2000 C. or above, to produce a high Pounds llmenite 320. Steel scrap 290 Baddeleyite 80 Manganese or 40 Rice coal 210 Subsequent charges may be of the same or similar compositions, varying slightly according to the analysis of ferrotitanium alloy desired.

Irrespective of the particular manner in which the skull or bottom of high ratio titanium to carbon material is originally formed, the baddeleyite may be omitted from the subsequent charges where it is not desired to maintain the carbon content relatively low. Thus, by the use of manganese ore alone in the charge, but without the use of baddeleyite, an alloy may be produced containing from 17% to 25% titanium and from 6% to 10% carbon. This alloy has the desired high percentage of titanium, but the carbon is too high for some purposes, the ratio of titanium to carbon being from about 2.5:1 to 3.5:1. On the other hand, where it is desired to maintain the carbon relatively low and it is not necessary to have the titanium over, say, 18%, the baddeleyite may be used in the charge without the manganese-containing material. It will be seen that the addition of baddeleyite alone produces a medium carbon alloy, that the use of manganese alone produces a high titanium alloy, and that the use of both baddeleyite and manganese in the charge produces an alloy having high titanium and medium carbon.

Where it is desired to increase the silicon oonleyite and manganese ore, in addition to the other ingredients of the charge, we may produce a ferrotitanium alloy' containing from about 10% to 40% titanium, preferably from about 15% to 30% titanium, about .5% to 5% carbon, about .5% to 10% manganese, about 1% to 10% silicon, and about .5 to 15% zirconium, the balance of the alloy being substantially iron. The presence of.

manganese in these alloys to an extent where it becomes a substantial alloy constituent rather than an incidental impurity results in dense brilliant alloys free from slag inclusions, oxide and nitride products.

In addition to the function of manganese or silicon, or both, in the production of ferrotitanium alloys in regulating or raising the titanium content of the alloys, the presence 'of substantial amounts of manganese and silicon .in the alloys is of benefit when the .alloys are used for treating steel. We have found, for example, that the addition to steels or irons of a fermtitanium alloy containing substantial amounts of both-manganese and silicon produces effects in respect to cleanliness, deoxidation and crystallization in the irons and steels which are markedly diflerent from those obtained when the ferro alloys of these elements are used independently.

In the course of a series of consecutive taps of an average weight of 250 pounds each,

0% of the production analyzed under 1.0% C.

8% of the production analyzed between 2-3% C.

50% of the production analyzed between 3-4% C.

25% of the production analyzed between C.

8% of the production analyzed between 5-6% 83% of the total production analyzed under 5% carbon. I

While we have specifically described the preferred procedure in carrying out our invention, it is to be understood that the invention may be otherwise embodied or practiced within the scope of the following claims.

We claim:

1. In the manufacture of ferrotitanium alloys, a

the steps comprising adding to a charge containing titanium ore and a carbonaceous reducing agent, a relatively small amount as compared to the titanium ore, of a refractory material containing an oxde of a metal of the group consisting of zirconium and beryllium in amount sum- 'cient to materially lower the carbon content of .ing titanium ore and a carbonaceous reducing agent, a relativelysmall amount as compared to the titanium ore, of a refractory material containing an oxide of a metal of the group consisting of zirconium and beryllium in amount willcient to materially lower the carbon content of the ferrotitanium alloy, and melting the charge.

3. In the manufacture of ferrotitanium alloys, the steps comprising adding to a charge containing titanium ore and a carbonaceous reducing agent, a relatively small amount as compared to 'thetitanium ore, of a refractory material containing an oxide of zirconium in amount sufilcient to materially lower the carbon content of the ferro-. titanium alloy, and a material containing a metal of the group consisting of manganese and silicon in amount sufllcient to materially raise the titanium content of the ferrotitanium alloy, and meltng thecharge. i

4. Inthe manufacture of ferrotitanium alloys, the steps comprising adding to a charge containing titanium ore and a carbonaceous reducing agent,- a relatively small amount as compared to the titanium ore, of a refractory material contain'ng an oxide of zirconium in amount s'uflicient to materially lower the carbon content of the i'errotitanium alloy, and melting the charge.

5. In the manufacture of ferrotitanium alloys in a carbon-lined electric furnace, the steps comprising melting a charge containing titanium ore, a refractory material containing a substantial amount of an oxide of a metal of the group consisting of zirconium and beryllium, and a carbonaceous reducing agent, thereby providing a work'ng bottom or interllning of a solidified re- 7 nium alloy and a material containing a metal of the group consisting of manganese and silicon in amount sumci'ent to materially raise the titanium content of the ferrotitanium alloy.

6. In the manufacture of ferrotitanium alloys in a carbon-lined electric furnace, the steps comprising melting a charge containing titanium ore, a carbonaceous reducing agent and a refractory material containing a substantial amount of zirconium oxide, thereby providing a working bottom or interlining of a solidified refractory metallic titanium composition containing a higher content of titanium than the molten bath which is intermittently tapped from the furnace,

and thereafter regulating the laying down and bringing up of bottom by the addition to subsequent charges of regulated amounts of refractory material containing zirconium oxide in amount suflicient to materially lower the carbon content of the ferrotitanium alloy and a material containing manganese in amount suflicient to materially raise the titanium content of the ferrotitanium alloy.

7. In the manufacture of ferrotitanium alloys in a carbon lined electric furnace, the steps comprising adding to a charge containing titanium ore and a carbonaceous reducing agent, a material containing manganese in amount sufficient to materially raise the titanium content of the ferrotitanium alloy, and melting the charge.

8. In the manufacture of ferrotitanium alloys in a carbon lined electric furnace in which a bottom of a refractory metallic titanium composition is provided on the carbon lining, the steps comprising melting a charge containing titanium ore and a carbonaceous reducing agent in said furnace, and regulating the laying down and bringing up of bottom by the addition to subsequent charges of regulated amounts of a material containing a metal of the group consisting of manganese and silicon'in amount sumcient to materially raise the titanium content of the ferrotitanium alloy.

9. In the manufacture of ferrotitanium alloys in a carbon-lined electric furnace, the steps comprising adding to a charge containing titanium ore and a carbonaceous reducing agent, a material containing manganese in amount suflicient to materially raise the titanium'content of the ferrotitanium alloy, and melting the charge at a temperature of at least 2000 C.

10. In the manufacture of ferrotitanium alloys containing at least 10% titanium in a carbonlined electric furnace, the steps comprising adding to a charge containing titanium ore and a carbonaceous reducing agent, a material containing manganese in amount sufficient to materially raise the titanium content ofthe ferrotitanium alloy, and melting the charge at a temperature of at least 2000 C.

JEROME STRAUSS. HOLBERT EARL DUNN.