US3063560A

US3063560A - Multi-port extrusion die

Info

Publication number: US3063560A
Application number: US789950A
Authority: US
Inventors: David A Edgecombe
Original assignee: Babcock and Wilcox Co
Current assignee: Babcock and Wilcox Co
Priority date: 1959-01-29
Filing date: 1959-01-29
Publication date: 1962-11-13
Anticipated expiration: 1979-11-13
Also published as: GB947492A

Description

3 Sheets-Sheet 1 I I I I I INVENTOR.

DAVID A. EDGECOMBE BY ATTORNEY I 1 1 z I Nov. 13, 1962 D. A. EDGECOMBE MULTI-PORT EXTRUSION DIE 3 Sheets-Sheet 2 Filed Jan. 29, 1959 FIG.2

FIG.3

INVENTOR.

DAVID A.EDGECOMBE ATTOR N EY Nov. 13, 1962 D. A. EDGECOMBE 3,063,560

MULTI-PORT EXTRUSION DIE Filed Jan. 29, 1959 3 Sheets-Sheet 3 D 27 7\ l5 D A IS K 28D 20D 25D J 26D 27D 27D 28D FIG.6

INVENTOR.

DAVID A. EDGECOMBE BY W ATTORNEY United states harem G 63,560 MULTl-PORT EXTRUSION DIE David A. Edgecombe, Beaver Falls, Pa., assignor to The Bahcock & Wilcox Company, New York, N.Y., a corporation of New Jersey Filed Jan. 29, 1959, Ser. No. 789,950 3 Claims. (Cl. 207-17) This invention relates to the extrusion of metal elements utilizing a die lubricant and, more particularly, to a novel multi-port die for simultaneously extruding more than one solid cross-section shape from a single heated extrusion billet of metal having a relatively high melting temperature and requiring the use of a die lubricant, and with a single stroke of the extrusion press.

In the extrusion of solid shapes a heated metal billet is positioned in a container with its end against the upstream face of a metal die having an opening conforming to the desired cross-section of the extrusion. A ram operating under high pressure then forces the billet metal through the die to form the extruded solid shape.

When the metal to be extruded is a ferrous metal or other metal having a relatively high melting temperature as compared to the melting temperatures of such metals and alloys as copper, brass, lead, aluminum and the like, the extrusion billet has applied to its surface a coating of a glass-like refractory lubricating material having a relatively wide range of melting temperatures below but approaching the extrusion temperature of the billet, or which becomes and remains viscous over such range of temperatures, and a plate or block of such lubricating material is placed between the upstream face of the die and the end of the billet. This lubricating material melts progressively or remains viscous to provide a lubricant film between the billet metal and the press parts throughout the extrusion.

An important factor to be considered in any extrusion operation, and particularly in the extrusion of solid shapes, is the so-called extrusion ratio. This is the ratio of the cross-sectional area of the billet metal to the crosssectional area of the die opening. If this ratio is too high, excessive press power is required, and die damage, such as wear and breakage, becomes excessive, in addition to which, other extrusion difficulties, such as stalling of the press and excessive temperature rise in the workpiece, increase with an increase in the extrusion ratio.

For best results, it is desirable to keep the extrusion ratio as low as possible within practical operation limits. The required press operating pressures increase with an increase in extrusion ratios and, for a given maximum available pressure, attempts to extrude at extrusion ratios in excess of a certain maximum value correlated with the available maximum press pressure will stall the press. Another factor to be considered is that the temperature rise resulting from the metal deformation during extrusion is a function of the extrusion ratio and must be kept at a minimum. Practical operating experience with extrusion presses clearly indicates that a low reduction or extrusion ratio results in longer tool life, better surfaces on the extruded products, and less danger of laminations or back end defects in the products.

Considering the foregoing in relation to maximum etliciency of output of the press, it would appear that, particularly in the case of metals requiring lubrication by the aforementioned refractory lubricating material, a desirable practical upper limit of' the extrusion ratio is 30:1, and a desirable practical lower limit is 8:1. Within this broad range, a preferred narrower range of practical extrusion ratios is from 25:1 to 12:1.

To keep the extrusion ratio within desirable practical ice related to the cross-sectional area of the solid shape that the ratio of the two areas falls within such desirable practical limits. This requires an excessively large stock of billet diameters and matching press toolage. Furthermore, in extruding a relatively small cross-section shape, a relatively small diameter billet must be used, which not only limits the press output rate, due to the low tonnage output per unit of time, but also prevents the use of the much larger diameter billets which are standard for tubular extrusions, for example. Another objectionable factor is that, to adapt a press, normally handling the standard size billets, to handling of such small diameter billets requires provision of special small inner diameter liners for the billet container and small diameter rams. All this not only increases the cost of parts required for the press but also increases the labor cost for press changeovers for different billet diameters. Such alterations are required at more frequent intervals where the billet diameter must be changed for each cross-section shape to be extruded, thus further reducing the press output per unit of time.

For the foregoing reasons, attempts have been made to use multi-port dies for extruding solid shapes. Where the die has two or more ports therein, the cross-sectional area of the die openings is doubled or multiplied. Thus, for the same billet diameter, the extrusion ratio can be correspondingly decreased, thus obviating many of the aforementioned objectionable factors and obtaining corre-. sponding benefits such as proportionately increased yield per billet.

However, when multi-port dies have been used, other difiiculties have been encounterd, such as tearing between the die ports, excessive die wear and damage, and poor quality of the extrusions. These difficulties have been particularly characterisitc of extrusion of the aforementioned ferrous metals and other relatively high melting temperature metals such as titanium, titanium alloys, and the like.

In accordance with the present invention, it has been found that these difficulties in the use of multi-port dies for the extrusion of shapes of steel and other similar difficult-to-extrude metals can be avoided, and satisfactory extrusions produced consistently with a much better yield, by proper positioning of the die ports within critical correlated limits as to the die area enclosed by the ports, the minimum distance between ports, the minimum distance between any part of any port and the container bore, the length of the portions of the ports included in the perimeter of the enclosed area of the dies, and the orientation of the ports. Of equal importance with the foregoing is the use of the refractory glass-like lubricant in proper form for the lubricant plate or block at the up stream face of the die.

The critical correlated limits may be defined as follows:

A=the enclosed area between the die ports, and is In accordance with the present invention, a multiport die is provided in which the foregoing factors have the following relationship:

(1) D should be a minimum of 20% of the inner diameter of the container liner, and should exceed this minimum as much as practically possible.

(2) A/L should have a minimum ratio of 0.85 inch when A is in square inches and L is in inches.

(3) Y should be a minimum of 11% of the inner diameter of the container liner.-

When utilizing multi-port dies incorporating these critical correlated limits, or port parameters, multiple extruded shapes can be formed at each extrusion stroke using large diameter billets with no die damage and with very little wear on the dies. Moreover, there is a high yield from each billet and the extruded shapes have excellent surfaces, with no laminations and no back end defects.

Of equal importance with the die paramters in obtaining these results is the use of the refractory lubricant in proper form. As known to those skilled in the extrusion art, the refractory lubricant block used originally at the upstream face of the die was a piece of plate glass. Because of the relatively high density of the solid glass, necessitating use of a comparatively thin section in order not to guard against too great an excess of lubricant, as well as difiiculties in the positioning of such a plate in the container against the die, the use of such a glass plate has been discontinued, in many cases, and a plug of fiber glass substituted therefor.

Fiber glass plugs have been satisfactory for use where the efiective die port areas have had a relatively large value, as in the case of dies used for extruding relatively thick-walled tubing. However, in the extrusion of shapes of small cross-sectional area, the fiber glass plug has not been satisfactory as the fiber glass tends to bridge and block the die ports due, at least in part, to the very high tensile strength of fiber glass. In addition, the distribution of the lubricant among the ports of multi-port dies has not been uniform.

In accordance with the present invention, successful die port lubrication in multi-port die extrusion of shapes, and particularly those of small cross-sectional area, is effected by using a plate or disk of glass powder agglomerated by a suitable binder, disks of the composition disclosed in my prior application Serial No. 512,128, filed May 31, 195-5, now Patent No. 2,946,437, being particularly satisfactory. The lubricant disk of the present invention differs somewhat in shape from those of said application, being designed to have a more conforming engagement, with the upstream faces of the multi-port dies having the port parameters of the invention.

For an understanding of the invention principles, reference is made to the following description of typical embodiments thereof as illustrated in the accompanying drawing's. In the drawings:

FIG. 1 is an axial sectional view of the die, container and ram of an extrusion press, corresponding generally to the line 11 of FIG. 2;

FIG. 2 is an elevation view of the upstream face of the die shown in FIG. 1, the outer circle indicating the inner diameter of the container liner, i.e. the diameter of the container billet receiving passage;

FIGS. 3, 4 and -6 are elevation views similar to FIG. 2 of the upstream faces of other multi-port dies embodying the invention; and FIG. is an elevation view of the upstream face of a die having the same number and shape of ports as the die of FIG. 4 but illustrating an improper orientation of the ports.

Referring to FIG. 1, suitable apparatus for extruding solid shapes, utilizing a multi-port die embodying the invention, illustrated, by way of example, as comprising a hydraulically operated horizontal extrusion press including a relatively massive cylindrical container 10 having a liner 11 therein in which is telescoped a liner insert 12. The inner diameter of liner insert 12 is substantially equal to that of the billet to be extruded.

The downstream end of liner insert 12 is formed with a frusto-conical seat 13 which is engaged by a frustoconical surface 14 on a die holder ring 15 having a frusto- 4. conical inner periphery 16. Ring 15 is secured to a movable die carrier (not shown) by means including a locking ring 17, and is engaged by an annular bolster block 18 locked in the die carrier. Inner peripheral surface 16 serves to seat a two part die assembly including a multiport die 2 0A, embodying the invention, and a multi-port backing member 21 having a frusto-conical outer peripheral surface seating against surface 16. It will be noted that the inner diameter of ring 15 at the container engaging end is somewhat less than that of liner insert 12, so that the outer periphery of die 20A is spaced from the inner surface of liner insert 12. As seen in FIG. 2, die NA (and backing ring 21) has a keyway 22 which receives a key or rib 23 on surface 16 to hold elements 26A and 21 against rotation relative to die holder ring 16.

A disk or plug 30, of granulated refractory lubricating material which becomes and remains viscous over a wide range of temperatures below but approaching the extrusion temperature, and which is bonded into a preformed shape by a suitable binder, is placed against the upstream face of die 20A. The presently preferred granular lubricating material is glass, and the specific construction and composition of disk 30 will be described more fully hereinafter.

After disk 30 is positioned against die 28A, a billet 35 is charged into liner insert 12 and against disk 30. Billet 3 5 may have its external peripheral surface coated with refractory lubricating material, such as glass, as indicated at 36. Such lubrication of the billet periphery may be effected prior to the billet being charged into the press, for example, by rolling the highly heated and relatively heavy billet over a relatively thick layer (i 4" to of granular refractory lubricating material spread substantially uniformly on a fixed heat resistant uniplanar surface over an area having a width at least equal to the length of the billet and a length at least equal to the circumference of the billet. The heavy, heated billet, rolling toward the press over the layer of granular lubricant, picks up the particulate or granular material and the latter melts to form a viscous lubricating layer on the outer peripheral surface of the billet.

Extrusion of billet 35 is effected by a ram 31 operated by hydraulic pressure of a high value, as for example 2500 tons. Ram 31 is shown as a tubular ram which is adaptable for extruding either solid shapes or tubes, and has a mandrel holder 32 concentric therewith and relatively movable to project a mandrel through a die for tubular extrusions. The mandrel (not shown) can be unscrewed from its holder 32 and, for solid extrusions is so removed. As shown in FIG. 1, a collared pin 33 is then screwed into holder 32 and its projecting end supports a dummy block 34 held thereon by a snap ring 3-7. Dummy block 34 forms the means actually engaging the outer end of billet 35 to extrude the billet through die 20A.

Referring to FIGS. 1 and 2, the die 26A is illustrated as having three ports 25A arranged to extrude centrally ribbed bars, each port being bounded by a lead-in or entry throat 26A. The minimum distance between any part of a port and the inner surface of liner insert 12, which is identical with the periphery of holder ring 15 at its container end, is indicated at Y and has a value of 1.1". As the inner diameter of liner insert 12 is 7.250, 11% thereof is 0.7975". Thus Y is substantially in excess of 11% of the inner diameter or bore of liner insert 12.

The area enclosed by the ports 25A is defined by inner edges 27A of these ports and straight lines 28A joining the ends of the inner edges of adjacent ports. This 'area is shaded and indicated at A, and has a value of 11.7525 sq. in. The minimum distance between ports. is indicated at D and has a value of 1.5". This is above the allowable minimum limit of 20% of the bore diame ter of liner insert 12, which is computed as 1.45. The length of the three inner edges 27A of ports 25A is 8.4", which is the L factor.

For die 20A, the following relations hold:

D is 1.5, or greater than 20% of the bore diameter of liner insert 12 (1.45").

A/L is equal to 11.7525/ 8.4, or about 1.4 inches, which is in excess of the allowable minimum of 0.85 inch.

Y is equal to 1.1 which exceeds 11% of 7.250 (0.7975"). Die 20A thus has parameters in accordance with the invention. The ports in FIGS. 3-6 have their parts and spacing numbered similarly to those in FIG. 2 except for the substitution of letters B to E for the letter A.

Referring to FIG. 3, a two-port die 20B embodying the invention is illustrated. Die 2013 has a pair of ports 253 each arranged to form a contoured solid shape such as, for example, a molding. The minimum distance between any part of a port and the liner insert 12 is indicated at Y as the radial distance extending between the periphery of holder ring and an outer corner of the ports 25B, and is at least 11% of the diameter of the container bore. Specifically, the inner diameter of liner insert 12 is 7.250", Y is 1.1", and 11% of 7.250" is 0.7975. Y is thus in excess of the allowable minimum. The area enclosed between the two ports is indicated by the shaded area A bounded by the inner edges 27B of ports 25B and the two straight lines joining the inner corners of the two ports to each other. For die 2013, A is equal to 7.72 sq. in.

The minimum distance between ports 25B is indicated at D and, in the case of die B is 2.450", which is above the allowable minimum of 1.450" representing 20% of the liner insert bore which, as stated, is 7.250". The length of the portion of the die orifices bounding area A is equal to the sum of the lengths of the facing edges of ports B and, in this case, is 5.620" which is the L factor.

Hence, for die 2013, the following relations hold:

D is 2.450", or greater than 20% of the bore of the liner insert (1.450).

A/L is equal to 7.72/5.620, or 1.37 inches, which is in excess of the minimum of 0.85 inch.

Y is equal to 1.1, which exceeds 11% of 7.250, or 0.7975.

When it was attempted to extrude the shape for which die 2013 was designed, using a liner insert of the same bore diameter as liner insert 12, and a single port die, a defective extruded product of very poor quality was obtained. However, in extruding the same shape with the same diameter billet but using 2-port die 20B, an extrusion of excellent quality is obtained. Moreover, the extrusion ratio is cut in half with corresponding savings in power.

FIGS. 4 and 5 illustrate the importance of proper orientation of the ports to obtain the largest possible entry area for flow of lubricant to the area A, as well as illustrating the application of the invention principles to a 3-port die having ports differing in shape from those of the 3-port die 20A of FIGS. 1 and 2. In both the die 20C of FIG. 4 and the die 20D of FIG. 5, the shape and area of the die ports 25C and 25D are identical but the orientation of ports 25C differs from that of ports 25D. 1

The following factors apply to die 20C of FIG. 4: s,

Liner insert dia.=7 25(y' Y=1.15" D=l.6 L=8.100" A=8.84 sq. in.

A/L=1.09 inches It will be noted that D is in excess of 20% of the diameter of the liner insert and Y is in excess of 11% thereof. Also A/L is substantially in excess of 0.85 inch.

For die 20D of FIG. 5, the corresponding factors are as follows:

Liner insert dia.=7.250" 20% of 7.250"=1.450"

11% of 7.25l0=0.7975

Y=1.1 D=1.35" L=4.425" A=5.01 sq. in. A/L=1.13 inches It will be noted that Y is greater than 11% of the bore diameter of the liner insert, but D is less than 20% thereof. Also, it will be seen that the lines 28D joining the outer ends of the port inner edges 27D are much less in length than the corresponding lines 28C of die 20C of FIG. 4, thus providing a much more restricted area for flow of lubricant into area A than is provided in die 20C. Furthermore, the central lubricant area A of die 20D (FIG. 5) is only 5.01 sq. in. as compared to the 8.84 sq. in. of the area A of the die 20C of FIG. 4. Consequently, with the port orientation of FIG. 5, the lubricant distribution relative to the ports is much less efficient than with the port orientation of FIG. 4. As will be pointed out hereinafter, die 20D washed or ripped between ports 25D, while die 20C is completely satisfactory from the breakage and wear standpoints, and provides high quality extrusions.

The principles of the invention are applicable irrespective of the number of die ports within practical limits of die area relative to total port area. By way of example of this, reference is made to FIG. 6 which illustrates a die 20E having four ports 25E each arranged to extrude a generally angular shape. The factors appurtenant to die 20B are as follows:

Liner insert dia.=7.250" 20% of 7.250"=1.450" 11% of 7.250"=-0.7975

Y=0.95" D=1.85" L=10.800"

A=13.49 sq. in. A/L=1.25 inches From this it will be seen that Y exceeds 11% of the bore diameter of the liner insert 12, D exceeds 20% thereof, and A/ L exceeds 0.85 inch. Die 20E produces high quality extrusions with a minimum of wear.

The criticality of the factors D and A/L will be seen from the following table which lists a number of dies, in some of which both D and A/L" are above the critical minimum and in others of which one or both of these factors is below the critical minimum. In the first case, the dies produced high quality extrusions with no die breakage and minimum of die wear per extrusion. In the second case, either the extrusions were of poor quality or the dies washed or ripped between ports.

Liner Die N0. N0. of Inner A/L D (in in.) D (min) Ports Dia. (in in.) Allow. (in in (m in.)

Dies Nos. 53B, 111, and 117 had ports of the size, shape and general arrangement of the ports shown in FIGS. 3, 5 and 6 respectively with a slightly larger container liner inner diameter. Of the listed dies, dies Nos. 108 and 1 47 wore very rapidly, and dies Nos. 11, 118, 140-, 139, and 147 washed or ripped between ports. The D or A/L factors, or both factors, for these dies'were below the critical minimum limits. Each of the other dies listed above per formed satisfactory and produced high quality extrusions.

As stated, the form of glass for plate or block is important to proper lubrication of the multi-port dies. This plate has a diameter slightly less than that of liner insert 12, for easy placement against the upstream face of the die before lubricated billet is charged into the press, and is of suficient thickness, such as from 1" to 1.5 thick, to provide the quantity of refractory lubricant required for any given extrusion. The die engaging face of plate 30 may be rounded off at its periphery whereas the billet engaging face is preferably flat with a relatively sharp peripheral edge.

Plate or disk 30 is formed from a mixture of glass powder and a binder, such as sodium silicate, compressed in a mold, with the agglomerated glass powder disk being left to dry for 12 to 24 hours in air at a temperature of about 75 F. The following mixture has been found suitable in forming the disk of agglomerated glass powder:

Glass powder parts by weight" 97 Sodium silicate (36 Baum) parts 2 Water do 1 The glass powder is prepared by ball mill grinding. It

need not necessarily be carefully graded with regard to grain size but it has been found that a powder of such grain size that at least 70% and preferably at least 80% of the powder passes through a screen having 50 meshes per lineal inch is satisfactory. Where the metal to be extruded has an extrusion temperature ranging between 2000 and 2350 F., the most suitable type of glass is ordinary window glass, i.e., a soda-lime glass containing about 19% Na O, 5% Cat) and 73% SiO The preferred quantity of glass powder used in making the agglomerated disk is about 100 grams per in. (100 grams per square inch) of the cross-sectional area of the bore of liner insert 12.

Binders other than sodium silicate can be employed in forming the agglomerated glass disks. Where the metal billet to be extruded has a relatively low extrusion temperature and, accordingly, where it is desirable to use an agglomerated disk of glass powder having a relatively low melting point, a suitable binder for the glass powder is phosphoric acid. Instead of employing a binder for agglomerating the glass powder into a disk, agglomerated disks may be made by sintering a compacted or uncompacted body of glass powder.

The disk of agglomerated glass powder should have a density of about to 90%, preferably from to 70%, of the density of the glass from which the powder is made. The density of the disk can be readily regulated by the amount of pressure applied during the compacting step. Where the preformed disk is made of agglomerated window glass powder, the disk preferably has a density of about 0.50 to 2.0.

The disk 30, preformed of powdered glass agglomerated with a binder has the advantage, as compared to fiber glass plates or plugs, that the glass powder, in the viscous state during extrusion, flows freely through the die ports even when the latter are relatively small in flow area. On the other hand, under extrusion conditions, fiber glass tends to bridge and plug the ports, particularly those of smaller cross-sectional area. Also, the surface defects characteristic when using fiber glass are eliminated.

Plate 30 has a density substantially less than that of a solid glass plate so that, for a given quantity of glass of definite lateral dimensions, it may be made substantially thicker than the solid glass plate, and thus easier to handle and position in the liner insert against the die face. Glass in the form of a solid plate having the same thickness would be so much in excess of the amount actually needed for lubrication that serious difiiculties would be experienced both in extrusion and in finishing of the extrusions. Other relative advantages of the agglomerated glass powder disk 30 are fully set forth in the above ture metallic products each of which has a transverse cross-section bounded by at least one substantially rectilinear section, said die assembly having a die body which can be tightly assembled to the extrusion end of a billet container having a right circular cylindrical cavity therethrough and adapted to contain in its extrusion end a body of refractory lubricating material becoming viscous over a range of temperatures below but approaching the extrusion temperature and distributed over the area of said die body, the junction of the walls of said cavity with said die assembly being at a circular periphery on the billet side of said die assembly, said die body having a plurality of axially parallel extrusion ports each having an extrusion orifice with a transverse cross-section bounded by at least one substantially rectilinear facing edge and corresponding to the respective cross-section of a desired extrusion product, and said extrusion ports being relatively arranged so that the cross-sectional area measured in square inches of the die surface bounded by the facing edges of said orifices and straight lines joining the outer ends of said facing edges divided by the sum of the lengths of said facing edges measured in inches is at least 0.85 inches.

2. A multi-port die assembly of the character and construction claimed in claim 1 in which the minimum dis tance between the facing edges of adjacent orifices is at least 20% of the diameter of the billet-receiving cavity.

.3. A multi-port die assembly of the character and construction claimed in claim 2 in which the distance radially from each said orifice to the surface of said billet-receiving cavity is at least 11% of the cavity diameter.

References Cited in the file of this patent UNITED STATES PATENTS 2,161,186 Morgan et al June 6, 1939 2,255,236 Willis Sept. 9, 1941 2,723,028 Carter Nov. 8, 1955 2,893,554 Sejournet et al. July 7, 1959 FOREIGN PATENTS 536,606 Great Britain May 21, 1941 607,285 Great Britain Aug. 27, 1948 OTHER REFERENCES Journal of the Mechanics and Physics of Solids, Vol. 5, 19561957, Ed.-in-Chief R. Hill, Dept. Math., The University, Nottingham, England, article by L. C. Dodeja and W. Johnson, pages 281-295.

German Application 1,022,544 printed Jan. 16, 1958 (K1. 7b 10/80).

The Effect of Process Variables on Extrusion Pressures of Lead, Paper No. 58A109, by J. Frisch and E. G. Thornsen, Nov. Sill-Dec. 5, 1958, A.S.M.E. 8 pp.