US2947622A

US2947622A - Method of making lead-containing steels

Info

Publication number: US2947622A
Application number: US743708A
Authority: US
Inventors: Tenenbaum Michael; James W Halley; Frank W Luerssen
Original assignee: Inland Steel Co
Current assignee: Inland Steel Co
Priority date: 1958-06-23
Filing date: 1958-06-23
Publication date: 1960-08-02
Anticipated expiration: 1977-08-02
Also published as: CH381434A; BE579958A

Description

AU8 2, 1960 M. TENENBAUM ETAL 2,947,622

METHOD oF MAKING LEAD-CONTAINING sTEELs 2 Sheets-Sheet 1 Filed June 23. 1958 Aug. 2, 1960 M. TENENBAUM l-:TAL

METHOD oF MAKING LEAD-CONTAINING sTEELs 2 Sheets-Sheet 2 Filed June 23, 1958 Zi/zy. 5.

METHO OF MAKING LAD-CONTAINING STEELS Michael Tenenbaum, Flossmoor, lll., and James W. Halley, Chesterton, and Frank W. Luerssen, Munster, Ind., assignors to Inland Steel Company, Chicago, Ill., a corporation of Delaware Filed June 23, 1958, Ser. No. 743,708

3 Claims. (Cl. 75-129) This invention relates to steel. More particularly,

this invention is concerned with a novel process of promachineability characteristics compared to unleaded steels. Lead containing steels are commercially available and are widely used where high speed machining of excellent quality is required.

The production of lead containing steels has been effected in a number of ways. One method tried was to introduce lead blocks-to molten steel in a ladleor ingot mold. This method was not satisfactory because nearly all of the lead settled to the bottom with only a small insufficient proportion being dispersed throughout the steel. Even when the lead was added by pouring in small pieces of lead the result was not significantly different. A better method, and one that proved useful commercially, wasto introduce the lead in the form of a continuous stream of small pellets directly into ya stream of molten steel flowing into a mold, such as an ingot mold. Such a method, however, requires careful coordination of the flow of each stream, considerable manual labor and supervision and maintenance of the lead delivering equipment. These and other similar prior art methods of addition were all based on the assumption that lead is completely insoluble in molten steel and that, therefore, it was necessary to break up and disperse the lead particles in the molten steel just before freezing so that they would become entrapped in the steel. In practice, however, globules of lead were frequently found in ingots produced in this way.

A new, simple and efiicient method of introducing lead into steel has now been discovered. According to the present invention this method, in one of the broad aspects thereof, comprises feeding a stream of molten steel to molten lead, separating the molten steel and molten lead into two layers by gravity settling, removing the upper layer comprising steel having a small amount of lead dispersed therein and solidifying the leaded steel so produced.

The method of this invention yields leaded steel remarkably free of lead globules and particles. This is due primarily to the gravity settling which permits lead particles to separate from the steel before the steel is solidi- `tied, as by introduction into an ingot mold. However, it is also apparently the result of a more uniform and thorough distribution of the lead in the steel, perhaps even as a true solution, than was achieved by prior art methods in which lead concentrations were often undesirably localized in certain areas, even though not present as globules.

The invention will now be described further in conjunction with the attached drawings in which:

Fig. l is a plan view of a vessel forV holding and separating the molten lead and steel and conveying the leaded steel to a mold.

Fig. 2 is a sectional view of the vessel of Fig. 1 taken at theline 2 2;

Fig. 3 is a plan view of 4another type of vessel which may be used in the invention to hold the molten lead and effect separation of the, molten steel therefrom; and

Fig. 4 is a sectional view of the vessel of Fig. 3 taken at the line 4 4.

The vessel shown in Figs. l and 2, generally called a tundish, is made of a suitable refractory material.V The vessel l10 ordinarily has a reinforcing. cover 11.` The vessel is shaped to provide a bowl area 12 which' has lip 13 lower than the other sides of the bowl to permit excess molten material in the bowl to ow over the lip 13, down the discharge conduit 14 and out the orifice 15. In the practice of this invention molten lead 16 is placed in the bowl 12 but to a level appreciably below the lip 13. A stream of molten steel `18 is then caused to flow into the bowl and into the molten lead where the steel stream is dispersed. The molten steel, being the lighter of the two metals, rises to form an upper lead-containing steel layer 17 over the molten lead. As the molten steel stream 18 continues to flow, the lead containing steel layer 17 continues to rise until it spills over lip 13, iiows through conduit 14 `and out discharge orifice 15. The leaded steel may then be directed-to an ingot mold.

A modiied tundish adapted for production of larger quantities of leaded Vsteel and increased lead settling is shown in Figs. 3 and 4. The vessel 30 of refractory ymaterial is reinforced -With a steel cover 35. It has bowl area 31 which functions as a lead reservoir and steel-lead mixing and settling area. The bowl 31 has-"a dam 32 on one side lower than the other threevsides. The molten steel which ows over the dam 32, goes through conduit 33 and flows out nozzle 34.

In practicing the invention using a vessel as shown in Figs. 3 and 4 a molten pool of lead 36 is provided in the bowl 31 but of insufficient volume to fill it completely; a maximum of one-half to two-thirds is generally satisfactory. A stream of steel 38 is then directed into the pool of molten lead with sufficient force or velocity to be dispersed thoroughly in the lead. By this action and through the steel rising to the surface of the lead, small amounts of lead become uniformly and thoroughly dispersed in the steel. stream 38 causes the lead-bearing molten steel layer 37 to build up until it flows over the dam 32 and. into conduit 33 from which it may be directed into a mold. If desired a stopper may be provided in the conduit to regulate, or stop completely, the iiow of lead-containing molten steel through the conduit.

Obviously, .as leaded steel is produced using vessels such as those illustrated by the drawings, the amount of lead in the reservoir will be reduced. The rate of lead consumption can be readily determined, however, and the necessary quantities -added periodically to maintain a suitable lead supply.

The quantity of lead dispersed in a steel using this process can be varied by changing the velocity of the steel stream, the depth of molten lead in the reservoir and the total volume of lead present. It is generally, however, unnecessary to produce leaded steels containing minimum or maximum amounts of lead. The desired amount of lead, i.e., 0.20 to 0.35%, will normally be dispersed in the steel by following the invention employing considerably varied conditions and equipment.

The following examples are presented to illustrate the invention.

Example 1 To a tundish as in Figs. 1 and 2, 16 long, 81/2" wide and 6 deep there was added 30 lbs. of molten lead at a temperature of 1500 F. to the bowl area. About 300 lbs. of molten steel was poured in a stream into the molten The continuous addition of steel by lead continuously. The layer of leaded steelV spilled over the lip and was discharged into an ingot mold. The lead analysis of the ingot was as follows:

Percent ngot height: Lead analysis, percent Example 2 One thousand pounds of lead in the molten state was placed in the bowl of a vessel or tundsh as shown in Figs. 3 and 4. The tundish was 88 long, 42" wide and 42" high. The moltenk lead was at 2500" F. A total amount of about 14,900 lbs. of molten steel was added in a stream tothe molten lead in about two minutes. The molten steel layer on top of the molten lead continued to build up until it overowed the dam and passed through the` conduit from which it was directed into an ingot mold. The ingot analyzed as follows:

Various changes and modications of the invention can be made and, to the extent that such variations incor- 4 porate the spirit of this invention, they are intended to be included within the scope of the appended claims.

What is claimed is:

l. The method of dispersing small amounts of lead in steel to increase the machineability of the steel which comprises feeding a stream of molten steel to a pool of molten lead, separating the molten steel and molten lead into two layers by gravity settling, removing the upper layer comprising steel having a small amount of lead dispersed therein, and solidifying the leaded steel so produced.

2. The method of dispersing small amounts of lead in steel to increase the machineability of the steel which comprises separately melting steel and lead, adding the molten steel to a pool ofthe molten lead in a stream with sufficient velocity so that it is distributed in the lead, separating the molten steel and molten lead into two layers by gravity settling, removing the upper layer comprising steel having a small amount of lead dispersed therein, and solidifying the leaded steel so produced.

3. The method of producing lead containing steel which comprises partially illing a vessel with molten lead, feeding a stream of molten steel into the pool of molten lead with suicient velocity so that the steel stream is dispersed in the molten lead, separating the molten steel and molten lead in the vessel by gravity into two layers, continuing the introduction of the molten steel stream into the molten lead during separation of said layers so that the upper layer of molten steel containing a small amount of lead dispersed therein overflows the vessel, and directing the lead-containing molten steel which so overows into a mold.

References Cited in the le of this patent UNITED STATES PATENTS 2,854,716 Funk et al. Oct. 7, 1958`

Claims

1. THE METHOD OF DISPERSING SMALL AMOUNTS OF LEAD IN STEEL TO INCREASE THE MACHINEABILITY OF THE STEEL WHICH COMPRISES FEEDING A STREAM OF MOLTEN STEEL TO A POOL OF MOLTEN LEAD, SEPARATING THE MOLTEN STEEL AND MOLTEN LEAD INTO TWO LAYERS BY GRAVITY SETTLING, REMOVING THE UPPER LAYER COMPRISING STEEL HAVING A SMALL AMOUNT OF LEAD DISPERSED THEREIN, AND SOLIDIFYING THE LEADED STEEL SO PRODUCED.