US3672038A - Method and apparatus for producing extruded steel shapes - Google Patents

Abstract

A method and apparatus for producing extruded steel shapes, characterized in that no rolling or forging of a billet is required prior to the time that the billet is placed in an extrusion press container. The entire system consists only of a refining furnace, a continuous casting machine for casting a bar which is cut into desired lengths, a consumable electrode furnace which uses the bars from the casting machine as electrodes to be melted, and the extrusion press itself which extrudes sections of the ingot formed by the consumable electrode furnace while requiring only a light surface treatment of the billets prior to extrusion. In this manner, the capital investment in a mill for producing bars of various shapes is reduced considerably.

Description

United States Patent Lombard I [54] METHOD AND APPARATUS FOR PRODUCING EXTRUDED STEEL [4 1 June 27, 1972 OTHER PUBLICATIONS 1-1. F. Moore, Shot Peening and the Fatigue of Metals,"

SHAPES published by American Foundry Equipment Co, 1944, page 9. [72] inventor: Daniel L. Lombard, Youngstown, Ohio Primary Examiner john R Campbell [73] Assignee: Lombard Corporation, Youngstown, Ohio Assistant C- Rei ey Attorney-William J. Ruano [22] Filed: May 5, 1970 I 211 App]. No.: 34,838 [57] ABSTRACT A method and apparatus for producing extruded steel shapes, characterized in that no rolling or forging of a billet is required [52] U.S. Cl ..29/527.6, 29/155 R, 29/DIG. 36, prior to the time that the billet is Placed in an extrusion press 29/DIG' 164/76 container. The entire system consists only of a refining fur- [5 1] Int. Cl. ..B23k 19/00 "ace, 3 continuous casting machine f casting a bar which is Field 0I Search 155 155 1316- 35, cut into desired lengths, a consumable electrode furnace 29/D1G. 47; 164/76 which uses the bars from the casting machine as electrodes to be melted, and the extrusion press itself which extrudes sec- [56] References Cit d tions of the ingot formed by the consumable electrode furnace while requiring only a light surface treatment of the billets UNITED STATES PATENTS prior to extrusion. In this manner, the capital investment in a ll f d d 2,648,895 8/1953 Davis ..29/1ss R g fi f Shapes re 2,617,179 11/1952 Burke ..29/DIG. 47

3,576,070 4/ 1971 Parsons ..29/527.6 SCIaims, 1 Drawing Figure I38 40 54 i Q=@,|2 I i A Q 1 1 M lllllllllll j ffl 2, n s, 1 1

1 5' illj I: :1 30 T "J U H Li J PATENTEDJUNN I972 INVENTOR. DANIEL L. LOMBARD ATTORNEYS METHOD AND APPARATUS. FOR PRODUCING EXTRUDED STEEL SHAPES BACKGROUND OF THE INVENTION As is known, the extrusion process is well suited for the production of tubes or solid shapes of stainless steels and other high-strength alloys for which orders are usually for small quantities. Such small quantities ordinarily cannot be rolled economically. The cost of extrusion dies for a special shape is insignificant in comparison with the cost of rolls; and a die change can be made on the extrusion press in a few minutes. It is therefore, a simple matter to make changes in the design of a section to be extruded, while thecost of such a change to a rolled section might be prohibitive.

In the extrusion process, a billet to be extruded is heated and then inserted into an extrusion press billet container having a die at one endthereof. Glass or other high temperature extrusion lubricant is used as a die and container lubricant during the extrusion process which occurs when a press stem is forced into the end of the container opposite the die.

In the past, the preparation of the billet for the extrusion press necessitated the use of expensive'rolling mill equipment which required a considerable capital investment. The steel form which the blooms where fonned was ordinarily cast into ingots; the ingots thereafter rolled into blooms; and the blooms then rolled into rounds which were cut into billets. Due to the fact that dirt and scale were rolled into the surface of the rounds in the rolling process, it was usually necessary to machine the billets prior to being extruded in the extrusion press. In addition to the rolling mill equipment, reheating furnaces were required prior to each rolling step. Needless to say, all of this required an extremely large capital investment and did not facilitate the production of small quantities of different types of steels, meaning that large quantities of steels of different types had to be carried in inventory.

SUMMARY OF THE INVENTION In accordance with the present invention, the necessity for expensive rolling equipment in the preparation of steel billets to be extruded is obviated by a process wherein the molten steel is continuously cast into logs or bars which are used as electrodes in a consumable electrode furnace wherein the electrode is melted by controlled feed and electric supply into a molten pool of metal beneath it, the pool continually solidifying at its lower end to build up an ingot. It has been found that an ingot of this type, being of extremely high quality, can be cut into billets for use in a steel extrusion press without the necessity for further processing except a quick shot blast. Thus, with the use of the present invention, no rolling equipment whatever is required; and the machining step is eliminated. This materially reduces the capital investment necessary to produce extruded steel shapes and eliminates the necessity for maintaining large amounts of steel of different types in inventory.

The above and other objects and features of the invention will become apparent from the following detailed description taken in connection with the accompanying drawing which forms a part of this specification.

With reference now to the drawing, the plant layout shown includes a conventional arc furnace wherein the steel is melted and refined. The furnace 10 is a standard swing roof, top loading, direct arc furnace. To facilitate quick changing of alloys without contamination the furnace is provided with interchangeable shells. Between melts, these shells can be interchanged in about one hour. Gas burners, not shown, are included to keep the furnace and spare shells hot during nonmelting periods. The steel, after refining, is poured into a ladle l2 and then transferred by an overhead crane, not shown, to a continuous casting machine 14 which casts the molten steel into the continuous bar 16.

This bar is cut by a flying hot saw 18 into lengths 20 which are stored in a storage area 22 and then passed through a shot blast machine 24 to a second storage area 26. The cut bars in storage area 26, after being shot blasted, are used as electrodes in one of a plurality of a consumable electrode furnace 28.

Such furnaces are well known and usually comprise an electrode of the metal to be melted (which in this case comprises a cut bar from the continuous casting machine 14) extending downwardly into a mold or crucible which receives the molten metal and within which an ingot is formed. The electrode is connected to one terminal of an electric current voltage source; and means are provided for electrically connecting the other terminal of the source to the mold and, hence, to the molten metal. Usually, in starting the melt, a small supply of chips or the like are placed in the mold so that when the arc is struck, such chips are melted to form an initial molten metal supply in the crucible mold. As the arc is maintained between the electrode to be melted and the molten pool of metal beneath it, the end of the electrode is melted due to the heat of the arc. As the electrode is melted, it is deposited in and forms the aforesaid molten pool, the bottom portion of which continuously solidifies as the electrode melts to fonn an ingot which increases in length, starting from the bottom upwardly. In this process, impurities float to and on the top of the molten pool; and assuming that the pool does not solidify during the formation of the ingot, the major portion of the impurities will be excluded from the main body of the ingot.

In certain cases, the electrode is melted within a vacuum; however in many cases it is possible to form a slag layer over the top of the molten pool, as by the addition of oxides. This molten slag layer, which moves upwardly as the ingot is formed, protects the molten metal from contamination. The resulting ingot is, as mentioned above, of extremely high purity and excellent grain structure; and, at the same time, its outer surface is essentially free from dirt and inclusions.

The furnaces 28 are of the double-head type such that when one head is melting, the other head can be used for electrode loading. The ingot at the bottom of each furnace is continuously extracted from the mold by a moving clamphead, except when the clamphead is retracted from an extended position and during the time that the ingot is cut to lengths by an abrasive saw, not shown. During these stationary periods, the melting within the furnace continues uninterrupted. Slag is fed into the furnace from an automatic slag feeder.

The cast ingots from the consumable electrode furnaces 28 are then passed through a second shot blast machine 30 which insures absence of surface contamination of the ingot prior to extrusion. The slot blast machine 30 is preferably of the airless blast wheel type. After shot blasting is completed, the ingots are power driven out of the shot blasting machine and stored in a storage area 32.

From storage area 32, the ingots are passed through a billet saw 34, which saws them to desired lengths, and are then stored in storage area 36 from where they pass to a billet heater 38 and thence to extrusion press 40. Provision is made in the billet heater 38 for maintaining a minimum atmosphere, whereby scale buildup is minimal. The heated billet is automatically conveyed to the billet loader, not shown, on the extrusion press 40. Note that there is no provision for billet surface preparation other than shot blasting prior to extrusion.

When the billet is positioned on the billet loader of the extrusion press 40, an expendable carbon dummy block is placed at the rear of the billet; and both the billet and the carbon dummy block are placed in the extrusion press container. An expendable carbon dummy block is used in this case to provide for extrusion of the entire billet of material to result in maximum yield. In addition, it eliminates the necessity of having a shear or saw on the extrusion press.

The extruded bar emerges onto a power operated runout table 42 which guides the extrusion during the operation and automatically withdraws the material from the press. A transfer mechanism, not shown, is included to transfer the extruded bar from the runout table to a cooling rack 44.

The extruded workpieces on the cooling rack 44 are dropped onto a batching transfer table therebeneath where they are accumulated and transferred, as a batch, to one of two heat treating furnaces 46 or 48. The extrusions will be forwarded to furnace 46 or 48, depending upon the type of steel involved. That is, either a tool steel or a stainless steel.

From the furnaces 46 and 48, extrusions are transferred to a storage area 52 and are then passed through a third shot blast machine 54. This shot blast machine is again of the airless blast wheel type. After passing through the shot blast machine 54, the extrusions are transferred to a stretcher-detwister 56.

In certain cases, it may be possible to extrude the continuous cast product after sawing at 18 and shot blast at 24, without the necessity for consumable electrode melting. This, of course, would depend upon the quality of the continuous cast product as well as the quality requirements of the finished, extruded product.

Although the invention has been shown in connection with a certain specific embodiment, it will be readily apparent to those skilled in the art that various changes in form and arrangement can be made to suit requirements without departing from the spirit and scope of the invention.

1 claim as my invention:

l. A process for producing extruded steel sections characterized in that no rolling or forging of the billets is required prior to extruding, which process comprises the steps of melting steel, producing cast ingots from the molten steel, cutting the ingots into billets, shot blasting the billets only without further surface treatment, heating the billets, and extruding said billets through a die.

2. The process of claim 1 wherein said cast ingots are produced by consumable electrode melting steel electrodes.

3. The process of claim 2 including the step of initially melting steel, continuously casting the melted steel, and cutting the cast shapes thus formed into said electrodes which are consumable electrode melted.

4. The process of claim 2 wherein said billets comprise sections of a consumable electrode cast ingot, and including the step of treating said billets prior to extrusion by shot blasting only.

5. The process of claim 2 wherein the consumable electrode cast ingots are substantially continuously removed from the furnace in which they are cast.

I. 10! t It

Claims (5)

1. A process for producing extruded steel sections characterized in that no rolling or forging of the billets is required prior to extruding, which process comprises the steps of melting steel, producing cast ingots from the molten steel, cutting the ingots into billets, shot blasting the billets only without further surface treatment, heating the billets, and extruding said billets through a die.

2. The process of claim 1 wherein said cast ingots are produced by consumable electrode melting steel electrodes.

3. The process of claim 2 including the step of initially melting steel, continuously casting the melted steel, and cutting the cast shapes thus formed into said electrodes which are consumable electrode melted.

4. The process of claim 2 wherein said billets comprise sections of a consumable electrode cast ingot, and including the step of treating said billets prior to extrusion by shot blasting only.

7. The process of claim 2 wherein the consumable eleCtrode cast ingots are substantially continuously removed from the furnace in which they are cast.

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