US3115249A

US3115249A - Extrusion system

Info

Publication number: US3115249A
Application number: US746926A
Authority: US
Inventors: Zouraeff Peter; Andrew G Forrest
Original assignee: Reynolds Metals Co
Current assignee: Reynolds Metals Co
Priority date: 1958-07-07
Filing date: 1958-07-07
Publication date: 1963-12-24
Anticipated expiration: 1980-12-24

Description

Dec. 24, 1963 ZOURAEFF ETA!- 3,115,249

EXTRUSION SYSTEM Filed July '7, 1958 2 Sheets-Sheet 1 WWW INVENTORS PETER ZOURAEFF ANDREW a FORREST gmwlwu United States Patent 3,115,249 EXTRUSION SYSTEM Peter Zouraelf, Phoenix, Ariz., and Andrew G. Forrest,

Richmond, Va., assignors to Reynolds Metals Company, Richmond, Va., a corporation of Delaware Filed July 7, 1958, Ser. No. 746,926 2 Claims. (Cl. 207-40) This invention relates to means and method of extrudlng plain carbon, alloy and stainless steels, titanium, titanium alloy and other high temperature materials, and is a continuationin-part of application Serial No. 65 5 ,66'2, filed April 29, 1'95 7, for Titanium Extrusion System, now abandoned.

Various methods of extruding the subject metals have been used, but the products of these extrusion methods have been found to have surface blemishes, and other imperfections, such as laps, seams, cracks and/ or porous conditions, such that it has been found necessary to produce the extrusions in sizes about of an inch thicker on all outside surfaces than specified final dimensions. The excess thickness is then machined and ground down to size, which is an expensive operation.

It is a primary object of the invention to eliminate the disadvantages of prior extrusion methods.

It is a further object to extrude materials in sections having higher quality finishes than formerly possible. By use of the method of this invention, extrusions having surface roughnesses as low as microinches arithmetic average have been produced.

Another object of the invention is to extrude shapes of smaller cross section than can be made by conventional means from the same size tooling.

Still another object is to extrude thinner sections than can be produced by conventional methods from the same size tooling.

A further object is to extrude shapes held to closer tolerances than those produced by other methods.

Yet a further object is to provide an extrusion method which will materially lessen the cost of fabricating high temperature materials.

In accordance with the present invention, the subject metals can be extruded with such improved quality of product that the cross-sectional shape of the extrusion can be made equal, within commercial practice tolerances, to the specified final dimensions, in such cases, for example, as parts for air frames. In the case of some jet engine parts, special design considerations may require some subsequent machining, but even in that case the amount of such machining is substantially reduced as compared to extrusions by present conventional methods.

In addition, the extrusion system of the invention enables thinner web sections to be extruded than are possible by conventional methods. Similarly, extrusions of smaller cross-sectional areas can be produced than are possible by conventional methods with comparable equipment.

The improved results of the invention are obtained by observing the following concurrent limitations regarding (l) the extrusion die, (2) the extrusion lubricant, and (3) the extrusion operating conditions of speed, billet tern-perature and extrusion ratio:

(1) Extrusion die.The die must be sloped and contoured on its inner face against which the billet is squeezed, in order to squeeze the billet progressively down to the size of the die slot as the billet metal approaches the slot. The design of each die must be adapted to the shape of the particular slot, according to known practices of die contouring, for the purpose of avoiding any shearing action such as would result from use of a fiat-faced die. One aspect of the avoidance of shearing action is the avoidance of dead pockets of billet metal which become detached from the main body of metal moving toward the slot, but may subsequently be carried through the slot, and weaken the extrusion because of the tendency of the pocket to become detached from the main body of the extrusion. The pockets also tend to corrugate and thereby cause laps in the metal which passes over the dead pocket on its way toward the die slot.

The dies may be either machined from forged blanks or cast directly to the desired configuration. In order to prolong the working life of the die, it is preferred that its bearing surfaces are of a chrome-cobalt alloy or like hard alloy. In the case of a cast die, this material may be cast directly into the bearing configuration. Since the machining of whole blanks of these hard alloys is very difficult and costly, it is preferred in this practice in the case of machined die that the hard alloy be applied by welding to the bearing areas and then machined or ground to final size. In order to produce complex shapes, it is the preferred practice in accordance with the invention to use a split die made up of different sections which are made separately and then assembled to form the complete die.

The accompanying drawings illustrate a present preferred example of a die used in accordance with the invention, as hereinafter more particularly described.

(2) Extrusion Iubricant.-A thin layer of micaceous particles disposed against the contoured faces of the die is necessary to lubricate the said faces as they squeeze down the billet, in order to prevent galling of the metal as it is forced through the die. The micaceous particles preferably have a particle size of about one micron, and are capable of internal shearing of the particles to provide the necessary lubricating action under the elevated temperatures and pressures within the die during the extrusion operation. The present preferred example of the micaceous lubricant is biotite, and other examples are muscovite and vermiculite. It is necessary to adhere the layer of micaceous particles to the walls of the die in such manner as to insure that they will be there when the preheated billet is compressed against the die walls, and for that purpose the said particles are admixed with an adherent binding agent, the present preferred example of which is a grease formed of a heavy petroleum oil gelled with bentonite clay. This grease has the ability of holding the layer of micaceous particles against the die walls in spite of the tendency of the grease to volatilize when the preheated billet is placed in the die cavity.

Examples of the lubricant and binder of the invention are hereinafter specified with greater particularity.

(3) Extrusion c0nditi0ns.-(a) Speed of extrusion.- The speed of extrusion in terms of movement of the extruded part from the die is approximately constant during the extrusion operation, and for the purposes of the invention the average speed of extrusion during the extrusion operation is in the range of about 40 to about 350 feet per minute, and is preferably about feet per minute. Higher extrusion speeds require excessive power and correspondingly powerful and expensive equipment, and lower speeds take too much time and introduce problems resulting from dissipation of heat during prolonged periods of extrusion.

(b) Extrusion rati0.-The extrusion ratio is the ratio of the cross-sectional area of the cylinder within which the billet is placed for extrusion, to the cross-sectional area of the die slot, and, for the purposes of the invention, is in the range of about 10/1 to about 50/1. Higher extrusion ratios require excessive power, and lower ex trusion ratios are apt to fail to work the metal sufficiently the produce a satisfactory extruded product. In general, an extrusion ratio in the range of about 15/1 to about 25/ 1 is preferred.

(c) Billet temperature.The temperature of the billet L, when the extrusion operation begins must, for the purposes of the invention, be in the range of about 1300 F. to about 24'00 F., depending on the nature of the particular subject metal being extruded, and the temperature rise before the metal passes out of the die slot, which is governed by such factors as the rate of extrusion and other extrusion conditions.

For a better understanding of t e invention, reference is made to the present preferred embodiment thereof shown, for purposes of illustration only, in the accompanying drawings. In the drawings:

FIG. 1 is a cross-sectional view taken vertically through the central axis of an extrusion press and showing the extrusion of a subject metal billet, in accordance with the invention;

FIG. 2 is an end view in elevation of the extrusion die shown in FIG. 1, showing the face of the die against which the billet is pressed;

FIGS. 3, 4 and 5 are enlarged, fragmentary, cross-sectional views taken on the lines 33, 4 4 and 55, respectively, of FIG. 2, and I FIG. 6 is an enlarged side view in elevation taken the line 66 in FIG. 2 and showing the face of one of the two split portions of the die shown in FIG. 1.

Referring now more particularly to the drawings, FIG. 1 shows an extrusion press 10 in which a subject metal billet 12 in the liner 15 of a container 14 is being compressed by a ram 16 and dummy block 18 and extruded through a die 20 to form an elongated extrusion 22. The die 20 is removably mounted in a certain die holder 24 and conventional supporting elements hold the die against axial thrust. Conventional resistance heater elements (not shown) are provided to preheat the liner, and the die is readily removable and replaceable to facilitate cleaning and preheating the die before each extrusion operation.

The die 20 is of split construction to facilitate constructing the die to produce sections such as the I section shearing of the metal.

30 pany, Newark, NJ).

of the illustrated extrusion 22. In accordance with present preferred practice, the die slot 26 is centered in the middle of the die, and is bisected by the split of the die, preferably along the plane of symmetry of the slot, where the slot is symmetrical, as illustrated. The face of the die along which the billet metal flows toward the slot has a generally conical depression 28 sloping from the outer periphery of the die toward the slot, in order to guide the metal toward the slot in such a way as to avoid any The initial lead-in slope changes near the slot, in smoothly contoured curves 30 which are tangent to the lead-in slope 28 and to the final bearing walls 32 of the slot. The metal is thus channeled smoothly along the inside face of the die until it passes out through the slot 25.

Before the billet is inserted in the container, a thin and substantially uniform layer of the lubricant of the invention is swabbed around the interior surface of the container which will be in contact with the billet. Likewise,

before the die is replaced on the container at the beginning of an extrusion operation, all of the die surfaces which will be in contact with the billet are similarly coated. A present preferred example of the lubricant is a mixture of equal proportions of biotite, having a particle size of one micron or less, and an adherent carrier consisting of petroleum oil mixed with enough bentonite clay to give ,it the consistency of a light grease (such a carrier, known as a bentone grease, is commercially available as Fiske #525 of Fiske Brothers Refining Com- If higher proportions of bioitite are used, or if other methods of application are substituted, such as spraying, the viscosity of the carrier may have to be altered by thinning with more volative petroleum oils or the like. Ranges of proportions of from 35 25% to by weight of biotite, the balance being Table of Examples Billet Extrusion Extrusion Material Preheat, Ratio Speed, Product F. ft/min.

I. Plain Carbon Steels: Exam 1e 1- 2 400 32 1 350 1 SAE 1020 Steel. p round II. llijlloy silbcels:

Xamp e 2-SAE 4340 Stee 2, 400 32:1 350 T sectio .125 thicl' 085. Example 3SAE 4130 Steel 2, 400 32:1 350 Do. m III. Stainless Steels:

Example 44221\I 2, 400 32:1 340 Do. gxample g-gglZ- 2, 400 32:1 320 Do.

xampe 1 7 2,400 18:1 270 L t 5 .2 IV. Hot Work Tool Steels: Soc Ion 2 0 and 1 5 Example 7-Vasco .Tet 1000 1, 950 13:1 320 H hcam-.150 thickness. V SExa npleI I8:TPeerles1su56 (Fisk .1 g, 23:1 286 I beam-.125 thickness. poem 1- omp eta s: xam e 14:1 168 l.3 0 h' l; 9A286 25% Nil-15% Cr). p Aug 0 0 t 10 Dogs VI. Commercially pure titanium: Engine Sections:

Example 10 1, 650 21 1 10 it. x 1.5 sq. in. %xamp}o11.l 1,208 2 1 14 ft. x 1 sq. in. xampe 5 60 t. '21 vn. Alpha-beta titanium alloys: M A qq m (a) 6% A1, 4% V, bal. Ti I-beams:

Example 13 1, 650 26:1 8 it. x 0.7 sq. in. Example 14 1, 800 26:1 80 8 it. x 0.7 Sq. in. Example 15 1,750 21:1 120 8 ft. x 0.7 sq. in. Example 16 1, 650 21:1 240 Engine Section, 10 it. x 1.5 (b) 4% A1, 4% Mn, m1. Ii

Example 17 1,700 26 1 225 I-beam, 8 It. x 0.7 sq. in. Example 18 1,650 21 1 120 Engine Section, 10 it. X 1.5

s (e) 3% A1, 5% Cr, bal. Ti q m Example 19 1, 700 26 1 225 I-beam, 8 ft. X 0.7 sq. in. Example 20 1, G50 21 1 120 Engine Section, 10 ft. x 1.5

s (d) 3% Mn, 1% Cr, 1% Fe and Mo, q m

1% V, bal. Ti-

Example 21 1, 650 20:1 60 Engine Section, 10 it. x 1.5

sq. in. VIII. Alpha Titanium alloys: 57 Al 1 850 34:1 30 t 25% Sn, b2]. Ti Example 22 o a T Sec ion, 8 it. x 0.4 sq. in.

In Examples 1-9 of the above table the various steel samples are commercially well known and are comprised of iron containing other metals alloyed therewith in approximately the nominal percentages by weight as shown gage the billet during extrusion with a lubricant consisting of micaceous particles carried in an adherent grease with the micaceous particles being not more than one micron in size and constituting at least 25% by weight of said lubricant, and compressing the billet against the in the following tabulation: 5

SAE- SAE- SAE- PH-17-4 PH-17-7 Vasco 1020 4130 4340 lot 1000 Peeress 422-M A-286 Mangane se Silicon Molybdenum. Aluminum Sulfur 1 Denotes maximum limit.

Above are iron base alloys.

The products identified in the above table have an excellent finish and have dimensions Within commercial practice tolerances, so that subsequent machining is unnecessary in the case of air frame sections, for example, and in the case of engine sections is necessary only to a limited extent due to the special requirements of subsequent fabricating operations on engine sections. The extrusions possess an internal structure capable of satisfactory heat-treatment reponse in the case of certain alloys when produced within temperature limits suitable for that purpose during extrusion; e.g., Examples 5 and 6. In order to take full advantage of billet preheating, and to obtain the best results, the container and die are preferably prehea-ted before the extrusion operation. The container is preferably preheated to about 800 to 900 F. Typical die preheat temperatures for the operations shown in the above table are in the range 400 to 1050" F.

While We have illustrated and described certain present preferred examples of the invention and methods of practicing the same, it will be recognized that the invention may be otherwise variously embodied and practiced within the scope of the following claims.

What is claimed and desired to be secured by Letters Patent is:

1. The method of extruding high temperature metals selected from the group consisting of plain carbon, alloy and stainless steels, titanium and titanium alloys, substantially directly to final dimensions with the surface thereof characterized by the absence of blemishes and having an average surface roughness as low as microinches, which comprises the steps of preheating a billet of the aforesaid 5 metal to a temperature in the range of 1300" F. to about 2400" F., placing said billet next to an extrusion die having a sloped, contoured inner face and provided with an extrusion opening of a size and shape to form the billet substantially exactly to the final dimensions desired, the opening having a cross-sectional area within the range of about V to about of the cross-sectional area of the billet, coating the surfaces of the die which endie to extrude the metal through said extrusion opening of the die at an average rate in the range of about 40 to about 350 feet per minute.

2. The method according to claim I]. in which the micaceous particles are selected from the group consisting of biotite, vermiculite and muscovite, and the adherent grease is a petroleum grease gelled with bentonite clay, said micaceous particles being in the range of from about 25% to about by weight of the lubricant.

References Cited in the file of this patent UNITED STATES PATENTS 140,567 York July 1, 1873 1,066,971 Adams July 8, 1913 2,063,563 Sparks Dec. 8, 1936 2,322,738 Rouse June 22, 1943 2,623,852 Peterson Dec. 3 0, 1952 2,731,145 Kritscher Jan. 17, 1956 2,735,814 Hodson et al Feb. 21, 1956 2,753,261 Goetzel et al. July 3, 1956 2,757,794 Walgren Aug. 7, 1956 2,806,596 Dodds et a1 Sept. 17, 1957 2,821,475 Jafiee et al. Jan. 28, 1958 2,832,468 Krause Apr. 29, 1958 2,837,425 Vordahl June 3, 1958 FOREIGN PATENTS 726,917 Great Britain Mar. 23, 1955 OTHER REFERENCES Metal Flow and the Extrusion Defect, pp. 108-112, American Machinist, May 15, 1950. 9 Hot Squeeze Put on Tough Alloys, p. 67, Steel, March Titanium Metal and Its Future, 1st par. p. 32, Harvard Business School, Cambridge, Mass., March 3, 1952.

The Extrusion of Titanium, by Alvin M. Sabroff et al., Battelle Memorial Institute, WADC Tech. Report 54- 555, March 1955.

Claims

1. THE METHOD OF EXTRUDING HIGH TEMPERATURE METALS SELECTED FROM THE GROUP CONSISTING OF PLAIN CARBON, ALLOY AND STAINLESS STEELS, TITANIUM AND TITANIUM ALLOYS, SUBSTANTIALLY DIRECTING TO FINAL DIMENSIONS WITH THE SURFACE THEREOF CHARACTERIZED BY THE ABSENCE OF BLEMISHES AND HAVING AN AVERAGE SURFACE ROUGHNESS AS LOW AS 10 MICROINCHES, WHICH COMPRISES THE STEPS OF PREHEATING A BILLET OF THE AFORESAID METAL TO A TEMPERATURE IN THE RANGE OF 1300*F. TO ABOUT 2400*F., PLACING SAID BILLET NEXT TO AN EXTRUSION DIE HAVING A SLOPED, CONTOURED INNER FACE AND PROVIDED WITH AN