US3310393A

US3310393A - Metallurgical process

Info

Publication number: US3310393A
Application number: US300102A
Authority: US
Inventors: Leonard L Cogen
Original assignee: Union Carbide Corp
Current assignee: Union Carbide Corp
Priority date: 1963-08-05
Filing date: 1963-08-05
Publication date: 1967-03-21
Anticipated expiration: 1984-03-21

Description

United States Patent 3,310,393 METALLURGICAL PROCESS Leonard L. Cogen, Newark, N.J., assiguor to Union Carbide Corporation, a corporation of New York No Drawing. Filed Aug. 5, 1963, Ser. No. 300,102

1 Claim. or. 75-60) This invention relates to an improved metallurgical method for use when introducing gases, liquids or solids into metallurgical furnaces, vessels and the like.

The invention is particularly directed to the use of an improved material for forming metallurgical lances and blast furnace tuyeres.

Metallurgical lances are now commonplace in the production of steel. These lances are currently used primarily for blowing gaseous oxidants into a molten metal bath within open hearth furnaces and basic oxygen process vessels. An example for such a lance is disclosed and illustrated in U.S. Patent 3,020,035 issued Feb. 6, 1962 to G. W. Hinds et al. As disclosed therein, it has been necessary to provide internal water cooling systems to better enable the equipment to withstand the severe chemical attack of heated iron and slag particles which are continuously thrown against the equipment while it is operating in a highly oxidizing, high temperature atmosphere. Notwithstanding various basic nozzle configurations utilized in addition to other design changes, and water cooling, the life of this equipment is relatively short.

It has been the general practice within the industry to fabricate this metallurgical injection equipment of oxygen-free copper. Usually, only the nozzle end of the apparatus which is actually exposed to the most intense reaction areas within the furnace is fabricated of copper, with the remaining parts formed of steel. The copper nozzle is subjected to severe attack from the splashing and abrasion thereon of heated particles of iron and slag. The rapid wearing away of the copper nozzle is believed to be caused by extremely hot particles of iron striking and adhering to the nozzle surfaces. These iron particles are then burned on the copper surface by the surrounding highly oxidizing atmosphere.

This iron oxidation reaction liberates intense localized heat which is suflicient to cause a scarfing or wearing away of the copper surface. The problem is thus believed to be characterized as a high temperature oxidation of the copper whereby the copper actually diffuses to the surface of the nozzle to continuously form a film of copper oxide, until the nozzle progressively wears away.

While a blast furnace tuyere is not subjected to the same high temperature, highly oxidizing atmosphere that a metallurgical lance encounters, still the problem of wear is similar whenever oxidants such as air, air enriched with oxygen, of pure oxygen, are injected through the tuyeres into the furnace. While the overall atmosphere within the blast furnace is reducing, the immediate localized area adjacent the tuyere discharge nozzle end will have an oxidizing affect on the tuyere nozzle whenever the oxidant is being blown into the furnace.

It is an object of this invention to provide an improved method of refining a molten steel bath when reacting oxygen therewith.

Another object is to provide a satisfactory material for use in fabricating at least the exposed nozzle portion of metallurgical apparatus for injecting gases, liquids or solids into furnaces operating with a high temperature, highly oxidizing atmosphere.

Another object is to provide a suitable and satisfactory material for use in forming at least the discharge nozzle portion of a metallurgical lance, and which will withstand prolonged operation in a high temperature, highly oxidizing atmosphere, when exposed to direct contact with hot iron particles. 1 i

A further object is to provide a material which is suitable and satisfactory for use in forming at least the nozzle discharge end of a blast furnace tuyere and which will withstand prolonged operation when introducing oxidants into a high temperature blast furnace and when exposed during such operation to direct contact with heated iron particles.

The first object is attained according to the present invention, in a method of refining a molten steel bath by reacting oxygen therewith, by blowing the oxygen into the bath through a lance having at least a nozzle discharge end composed of an alloy consisting essentially of 0.05% to 0.2% zirconium by weight and the remainder of initially oxygen-free copper.

The remaining objects are attained according to the invention by the use of a material consisting essentially of 0.05 to 0.2% zirconium by weight and the remainder initially oxygen-free copper.

This alloy may be prepared according to conventional alloying procedures by adding between 0.05 and 0.2% zirconium metal to an initially oxygen-free copper such as, for example, OFHC brand copper.

If other metals are present they should not be subversive to the characteristics of the copper-zirconium alloy.

This copper-zirconium alloy material has been found to possess an extremely high resistance to chemical attack by the iron-oxygen scarfing reaction occurring at its surface, in addition to possessing a high thermal conductivity at elevated temperatures when compared to the thermal conductivity of copper at such temperatures. It is believed that the zirconium diffuses to the surface of the copper whereupon it forms a zirconia-rich surface layer which holds tenaciously to the surface. This layer, it is believed, acts to greatly retard the outward diffusion of the copper.

It is to be noted that merely plating a copper surface with zirconia is ineffective as it is difficult to form a bonding which will provide the same long lasting protective layer.

Many alternative materials have been tried, without success, in an effort to extend the operational life of metallurgical lances. The use of highly oxidation resistant materials such as stainless steel and Monel, for example, were ineffective since such materials did not have suificiently high thermal conductivity at elevated temperatures. The use of oxygen-free copper, on the other hand, did not provide sufficient resistance to the high temperature oxidizing chemical attack by the iron particles, although it did have a high thermal conductivity at elevated temperatures.

The practicability of using the copper-zirconium alloy for fabricating a metallurgical lance was demonstrated by forming the nozzle discharge end of a conventional lance of this alloy. Another nozzle discharge end of identical design was formed of oxygen-free copper. Both lances were inserted in open hearth furnaces operating under the same commercial conditions. The lance with the copper nozzle discharge end-failed after 100 hours of operation, whereas the lance with the copper-zirconium nozzle discharge end did not fail until it had been operating 500 hours. In two similar tests the copper-zirconium nozzles lasted 489 and 501 /2 hours, respectively, while the copper nozzles of identical design lasted but /2 and 113 hours, respectively.

What is claimed is:

In a method of refining a molten steel bath by reacting oxygen therewith, the step of blowing a stream of oxygen through a lance having a nozzle discharge end References Cited by the Examiner UNITED STATES PATENTS 2/1958 McFeaters 266-34 4 V Bieniosek et al 266-41 Vogt 756O Saarivirta et a1 75153 Hudson 26634 BENJAMIN HENKIN, Primary Examiner.