US2377403A - Addition agent for treating molten iron and steel - Google Patents

Description

Patented June 5, 1945 ADDITION AGENT FOR TREATING MOLTEN IRON AND STEEL Walter Crafts, Niagara Falls, N. Y., assignor to Electro Metallurgical Company, a corporation of West Virginia No Drawing. Application October 23, 1940; Serial No. 362,415

2 Claims.

The invention relates to an agent suitable for the treatment of molten iron and steel to promote a fine grain structure and freedom from deleterious impurities.

During manufacture, steels become contami- Aluminum additions, in the amounts, for the purposes, and in the maner described above, tend to produce a steel containing deleterious types and quantities of non-metallic inclusions. It has been proposed to substitute for the aluminum other agents, such as vanadium, or titanium, but none of these elements is entirely satisfactory. Vanadium is usually too expensive to add in an amount suflicient to produce the desired results, and titanium as heretofore used tends to produce a steel containing numerous objectionable nonmetallic impurities.

According to the present invention. a steel that is substantially free from deleterious, gaseous or solid non-metallic impurities and that has improved mechanical properties (including improved impact strength) and excellent fine grain characteristics may be produced by adding to the steel while it is molten in the ladle or otherwise shortly before casting, a novel addition agent containing at least one metal selected from the group consisting'of titanium, zirconium, vanadium, and columbium, in aggregate percentage between 25% and 60% (preferably 35% to 55%) at least one metal selected from the group consisting of beryllium and boron, in aggregate percentage between 0.1% and but preferably under 5%; and the remainder iron.

The constituents of the addition agent are pref,- erably prealloyed in the form of a master alloy; but they may be unalloyed or only partially alloyed, and used in the form of a briquet of comminuted material. Also, some of the constituents thereof may suitably be in the form of easily reducible or decomposable compounds such as nitrides, nitrates or mixtures thereof.

The addition agent may be added to the steel in any well known manner, for example in the furnace, in the ladle, or in the molten stream during pouring. When adding the addition agent to the steel either in the ladle or in the molten stream, an agent containing less than about 65% iron should ordinarily be used in order to minimize the chilling effect of the iron. If the agent is added to the steel in the furnace, the iron content of the agent may be greater than 65%.

The degree of grain refinement or deoxidation of the steel per unit of addition agent added will vary, not only with the combination of elements selected, but also with the type of steel being treated, so that the total amount of agent to be added to the steel for best results must be determined by trial. Ordinarily, this totalamount of agent will be less than 5%, and most frequently less than 1%.

While the addition agents of this invention are especially useful in the treatment of steels which are to be hot worked, the invention is also applicable to the treatment of steels which are to be employed as castings.

Steels treated according to the invention are sound, substantially free from excessive nonmetallic inclusions, and possess improved ductility and shock resistance.

I claim:

1. A composition of matter, suitable for use as an addition agent for treating molten ferrous metal, consisting substantially of at least one' metal of the group consisting of titanium, zirconium, vanadium, and columbium, in an aggregate percentage between 25% and at least one element selected from the group consisting of beryllium and boron, in an aggregate percentage between 0.1% and 10%; and the remainder iron.

2. Composition of matter, as claimed in claim 1, in which the aggregate percentage of titanium, ziconium, vanadium, and columbium is at least 35% and the aggregate percentage of beryllium and boron is under 5%.

WALTER CRAFTS.