US1546176A - Titanium steel - Google Patents

Description

Patented July 14, 1925.-

UNITED STATES WALTHER MATHESIUS AND HANS MATHESIUS, CHARLOTTENBURG, GERMANY.

TITANIUM STEEL.

No Drawing.

To all whom it may concern.

Be it known that we, VVAL'rHnR MATHESIUS and Hans lllATI-IESIUS, citizens of the Ger man Republic, residing at Charlottenburg, Germany, have invented certain new and useful Improvements in Titanium Steel, of which the following is a specification.

Former attempts to employ the metal titanium usefully as an alloy steel have been practically unsuccessful, because, with the exception of accidental results which have shown the excellent qualities of a titanium steel, it has not been possible to produce titanium steel in a regular metallurgical process.

After many years of experiments which have been carried out by the applicants, the want of success has been found to be due to the fact that up to the present time the metal titanium has only been used as an addition to carbon steels.

ln consequence of the extraordinarily strong aliinity of titanium for carbon, sulphur and nitrogen, the addition of titanium to carbon-containing iron baths generally resulted in the formation of corresponding compounds of titanium with the abovementioned substances, which, due to their lack of solubility, were precipitated in the iron in a condition such that they affected only to a small extent the mechanical properties of the iron.

By the experiments of the applicants it was first recognized that titanium only affected very advantageously the mechanical properties of iron if, after these substances had been saturated with titanium, there was still a sufficient quantity of this metal present to form iron alloys with titanium, and consequently to allow the particular specific action of the metal titanium on the properties of the iron alloy to appear.

Among such properties are high limits of elasticity and very little wear, under friction.

metal titanium, which, on the one hand, leads I to considerable expense and, on the other hand, the proportion of titanium entering into combination with the metalloids carbon, sulphur and nitrogen unfavourably affects the elastic properties of the steel alloy.

Application filed May 17, 1923. Serial No. 639,703.

Favourable results were, on the other hand, obtained, if alloys were produced in which titanium was predominantly the foreign substance in the iron, or in which the substanceincluded corresponding percentages of the metals manganese, chromium, cobalt, tungsten, molybdenum, vanadium; that is, all these metals can be added, either separately or conj ointly, which are known to improve the quality of steel. (Such metals are hereinafter included in the expression alloying constituent of alloy steel) Such titanium-containing alloys can, ob viously, be made in many different methods. For instance, if electrolytic or other iron, as free as possible from carbon, is melted, the above-mentioned metals are added to the bath and then the necessary quantities of titanium in theform of ferro-titanium free from carbon; or the titanium may be produced in a nascent condition by an exother mic reaction within the bath. This method of producing titanium steel would naturally be expensive.

The following method appears adapted for the manufacture of titanium steel in large quantities and at a relatively small cost. Iron is decarburized as completely as possible in a Martin or an electric steel furnace, preferably provided with a basic lining and with the introduction of a basic slag.

A slag coating of lime, manganese ore and titanium iron ore is used for this purpose in the bath as a carrier of oxygen.

As long as the bath contains carbon, certainquantities of manganese and titanium are introduced into the metal bath by the reducing action of the carbon; also, from the silicic acid present in the slag covering some silicon is reduced and enters the bath. The relation between the quantities of silicon and titanium in the iron bath is naturally determined by the ratio of the silicic acid to titanic acid in the slag covering, although the-silicic acid is considerably more resistant to the reducing action of the carbon than is the titanic acid.

If the bath at the beginning of the relining operation is sufficiently rich in manganese, the presence of this metal facilitates the reduction of the titanic acid.

The amount of the titanium iron ore should be proportioned to the carbon content of the bath as far as possible, so that the iron and manganese oxides of the slag are reduced, thereby oxidizing the carbon out of the metal bath, so that the slag consists chiefly of silicates and titanates of lime.

At this stage of the process a certain quan tity of aluminium is added to the bath; either aluminium as such is introduced below the slag covering or the alloy ferro-aluminium is used for the introduction of the aluminium. The use of ferro-aluminium has the advantage that in consequence of its greater specific gravity the aluminium is automatically immersed below the slag covering.

At the high temperature of the steel bath there is a strong reaction between the aluminiu m that has been added and the slag covering, and consequently it is the titanic acid which is mainly reduced and is thereby introduced into the bath as metallic titanium.

The process carried out in this manner provides a silicon titanium steel almost entirely free from carbon, having the qualities above mentioned. It is characterized more particularly by the fact that in consequence of the action of the titanium and aluminium the steel is practically gas free.

Its characteristic features are, on the one hand, that it is very dense on the other hand, it is inclined to the formation of piping, so that the casting of the steel must be carried out with the usual precautions for obtaining ingots free from piping.

If a titanium steel is to be made which is perfectly free from carbides of titanium, a certain modification is required in the above described process, by which the refining op eration must be carried out with the use of iron ores free from titanium as a slag. When the bath has been completely freed from carbon, the slag covering must be poured off and a fresh slag of titanium iron ore and lime must be melted on the bath. The iron oxides of this slag are reduced by a calculated quantity of petroleum coke or calcium carbide and the aluminium is not introduced into the steel bath until that reaction is complete, if large losses are to be avoided by the reaction of the aluminium with the iron oxide.

The applicants have also found that other similarly acting metals can be used instead of aluminium with good and, to some extent better shown that instead of aluminium for the purposes described, the metal magnesium,

particularly in its alloy with iron, that is, in the form of ferro-magnesium, can be advantageously used. The metal magnesium has an essentially lower boiling point than aluminium. If it is added to the above described metal baths, in consequence of the high temperature, finely distributed vapours of magnesium are formed which pass up into the slag covering and effect within the latter the desired formation (by reduction) of titanium. By the use of magnesium, metal baths are obtained in less time (than with aluminium), and in which the content of light metal is practically entirely replaced by titanium. Other metals of the alkaline earths offer the same advantage, for example, calcium strontium, barium. The same reactions can be carried out with the alkali meta-ls if these are injected in the fluid form by suitable apparatus under the slag covering of the metal baths.

In order to allow the titanium steels to be forged, it is necessary that the amount of titanium therein should not be too high.

"We claim:

-1. As a new product, an iron alloy practically free from carbon and having a content in titaniumsufiicient to form a steel, but below the amount which would render the alloy unforgeable, and in which other metals known to improve the properties of steel are also present.

2. An iron alloy practically free from carbon having the properties of steel due to the presence of titanium.

In testimony whereof we have signed our names to this specification in the presence of two subscribing witnesses.

WALTHER MATHEsiUs. HANS MATHESIUS.

Witnesses E. HOLTGREN, ROBERT SoHAPEn.

results. The experiments have