NZ615063B2 - Extrusion of high temperature formable non-ferrous metals - Google Patents
Extrusion of high temperature formable non-ferrous metals Download PDFInfo
- Publication number
- NZ615063B2 NZ615063B2 NZ615063A NZ61506312A NZ615063B2 NZ 615063 B2 NZ615063 B2 NZ 615063B2 NZ 615063 A NZ615063 A NZ 615063A NZ 61506312 A NZ61506312 A NZ 61506312A NZ 615063 B2 NZ615063 B2 NZ 615063B2
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- New Zealand
- Prior art keywords
- feed material
- extrusion
- powder
- die
- feed
- Prior art date
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- 238000001125 extrusion Methods 0.000 title claims abstract description 104
- 229910052751 metal Inorganic materials 0.000 title claims abstract description 34
- 239000002184 metal Substances 0.000 title claims abstract description 34
- -1 ferrous metals Chemical class 0.000 title description 6
- 239000000463 material Substances 0.000 claims abstract description 176
- 230000001681 protective Effects 0.000 claims abstract description 43
- 238000010438 heat treatment Methods 0.000 claims abstract description 36
- 238000000034 method Methods 0.000 claims abstract description 29
- CWYNVVGOOAEACU-UHFFFAOYSA-N fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 claims abstract description 16
- 235000012438 extruded product Nutrition 0.000 claims abstract description 15
- RTAQQCXQSZGOHL-UHFFFAOYSA-N titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 76
- 239000010936 titanium Substances 0.000 claims description 61
- 229910052719 titanium Inorganic materials 0.000 claims description 61
- 239000000956 alloy Substances 0.000 claims description 27
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 claims description 27
- 229910052715 tantalum Inorganic materials 0.000 claims description 27
- 229910045601 alloy Inorganic materials 0.000 claims description 26
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 claims description 25
- 229910052758 niobium Inorganic materials 0.000 claims description 25
- 239000010955 niobium Substances 0.000 claims description 25
- REDXJYDRNCIFBQ-UHFFFAOYSA-N aluminium(3+) Chemical class [Al+3] REDXJYDRNCIFBQ-UHFFFAOYSA-N 0.000 claims description 23
- 239000001301 oxygen Substances 0.000 claims description 15
- 229910052760 oxygen Inorganic materials 0.000 claims description 15
- MYMOFIZGZYHOMD-UHFFFAOYSA-N oxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 claims description 15
- IJGRMHOSHXDMSA-UHFFFAOYSA-N nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 12
- 229910052757 nitrogen Inorganic materials 0.000 claims description 6
- 229910001069 Ti alloy Inorganic materials 0.000 claims description 4
- 239000000843 powder Substances 0.000 description 167
- 239000007789 gas Substances 0.000 description 52
- XKRFYHLGVUSROY-UHFFFAOYSA-N argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 34
- 150000002500 ions Chemical class 0.000 description 18
- 229910052786 argon Inorganic materials 0.000 description 17
- 238000001816 cooling Methods 0.000 description 17
- 210000002105 Tongue Anatomy 0.000 description 14
- RYGMFSIKBFXOCR-UHFFFAOYSA-N copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 13
- 229910052802 copper Inorganic materials 0.000 description 13
- 239000010949 copper Substances 0.000 description 13
- 239000004411 aluminium Substances 0.000 description 12
- 229910052782 aluminium Inorganic materials 0.000 description 12
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminum Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 12
- 239000000203 mixture Substances 0.000 description 10
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 10
- 239000007787 solid Substances 0.000 description 10
- 230000035882 stress Effects 0.000 description 10
- 238000004519 manufacturing process Methods 0.000 description 9
- 230000002829 reduced Effects 0.000 description 9
- MCMNRKCIXSYSNV-UHFFFAOYSA-N ZrO2 Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 8
- 238000011109 contamination Methods 0.000 description 8
- 229910052739 hydrogen Inorganic materials 0.000 description 8
- 150000002739 metals Chemical class 0.000 description 8
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 8
- 229910000601 superalloy Inorganic materials 0.000 description 7
- 230000037250 Clearance Effects 0.000 description 6
- 229910000831 Steel Inorganic materials 0.000 description 6
- 229910001315 Tool steel Inorganic materials 0.000 description 6
- 230000035512 clearance Effects 0.000 description 6
- 238000005056 compaction Methods 0.000 description 6
- 239000001257 hydrogen Substances 0.000 description 6
- UFHFLCQGNIYNRP-UHFFFAOYSA-N hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 6
- 230000001264 neutralization Effects 0.000 description 6
- 239000002245 particle Substances 0.000 description 6
- 239000010959 steel Substances 0.000 description 6
- 239000008187 granular material Substances 0.000 description 5
- 230000001965 increased Effects 0.000 description 5
- 239000011261 inert gas Substances 0.000 description 5
- 230000001105 regulatory Effects 0.000 description 5
- 239000000377 silicon dioxide Substances 0.000 description 5
- 238000011010 flushing procedure Methods 0.000 description 4
- 230000005484 gravity Effects 0.000 description 4
- 238000011068 load Methods 0.000 description 4
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Chemical compound [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 4
- 239000011159 matrix material Substances 0.000 description 4
- 238000010008 shearing Methods 0.000 description 4
- 238000005054 agglomeration Methods 0.000 description 3
- 230000002776 aggregation Effects 0.000 description 3
- 230000004075 alteration Effects 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 3
- 230000003247 decreasing Effects 0.000 description 3
- 238000007599 discharging Methods 0.000 description 3
- 239000012530 fluid Substances 0.000 description 3
- 238000005755 formation reaction Methods 0.000 description 3
- 238000000265 homogenisation Methods 0.000 description 3
- OWGOAJKLMXDFPQ-UHFFFAOYSA-N hydride;titanium(4+) Chemical compound [H-].[H-].[H-].[H-].[Ti+4] OWGOAJKLMXDFPQ-UHFFFAOYSA-N 0.000 description 3
- 230000001939 inductive effect Effects 0.000 description 3
- 238000002844 melting Methods 0.000 description 3
- 238000005245 sintering Methods 0.000 description 3
- 229910000048 titanium hydride Inorganic materials 0.000 description 3
- 241000229754 Iva xanthiifolia Species 0.000 description 2
- 229910000691 Re alloy Inorganic materials 0.000 description 2
- 229940035295 Ting Drugs 0.000 description 2
- 238000007792 addition Methods 0.000 description 2
- 239000000654 additive Substances 0.000 description 2
- 230000000996 additive Effects 0.000 description 2
- 239000011230 binding agent Substances 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-M chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 2
- 238000004140 cleaning Methods 0.000 description 2
- 239000011248 coating agent Substances 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 238000009694 cold isostatic pressing Methods 0.000 description 2
- 239000002826 coolant Substances 0.000 description 2
- 239000000789 fastener Substances 0.000 description 2
- 238000005552 hardfacing Methods 0.000 description 2
- 230000003993 interaction Effects 0.000 description 2
- 230000004301 light adaptation Effects 0.000 description 2
- 239000000395 magnesium oxide Substances 0.000 description 2
- 238000003801 milling Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000006011 modification reaction Methods 0.000 description 2
- 239000004033 plastic Substances 0.000 description 2
- 230000002633 protecting Effects 0.000 description 2
- 229910000967 As alloy Inorganic materials 0.000 description 1
- 229910000640 Fe alloy Inorganic materials 0.000 description 1
- 101700015817 LAT2 Proteins 0.000 description 1
- QEFYFXOXNSNQGX-UHFFFAOYSA-N Neodymium Chemical compound [Nd] QEFYFXOXNSNQGX-UHFFFAOYSA-N 0.000 description 1
- 229910052779 Neodymium Inorganic materials 0.000 description 1
- 229910000883 Ti6Al4V Inorganic materials 0.000 description 1
- 229910010380 TiNi Inorganic materials 0.000 description 1
- 229910000756 V alloy Inorganic materials 0.000 description 1
- 238000005296 abrasive Methods 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 238000000137 annealing Methods 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 229910010293 ceramic material Inorganic materials 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 230000003111 delayed Effects 0.000 description 1
- 230000001419 dependent Effects 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000010494 dissociation reaction Methods 0.000 description 1
- 230000005593 dissociations Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000005496 eutectics Effects 0.000 description 1
- 238000004880 explosion Methods 0.000 description 1
- 239000002360 explosive Substances 0.000 description 1
- 230000017525 heat dissipation Effects 0.000 description 1
- 239000001307 helium Substances 0.000 description 1
- 229910052734 helium Inorganic materials 0.000 description 1
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium(0) Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 1
- 229910000765 intermetallic Inorganic materials 0.000 description 1
- 230000001788 irregular Effects 0.000 description 1
- 238000002955 isolation Methods 0.000 description 1
- 238000005304 joining Methods 0.000 description 1
- 239000004482 other powder Substances 0.000 description 1
- 229910002077 partially stabilized zirconia Inorganic materials 0.000 description 1
- 239000008188 pellet Substances 0.000 description 1
- 230000035515 penetration Effects 0.000 description 1
- 230000002093 peripheral Effects 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 230000000135 prohibitive Effects 0.000 description 1
- 238000001953 recrystallisation Methods 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 230000000717 retained Effects 0.000 description 1
- 238000010079 rubber tapping Methods 0.000 description 1
- 239000011163 secondary particle Substances 0.000 description 1
- 229910001285 shape-memory alloy Inorganic materials 0.000 description 1
- 238000007493 shaping process Methods 0.000 description 1
- 230000035939 shock Effects 0.000 description 1
- 229920002545 silicone oil Polymers 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 230000003019 stabilising Effects 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 238000010301 surface-oxidation reaction Methods 0.000 description 1
- 238000005491 wire drawing Methods 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
- B21C23/00—Extruding metal; Impact extrusion
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
- B21C23/00—Extruding metal; Impact extrusion
- B21C23/005—Continuous extrusion starting from solid state material
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F2999/00—Aspects linked to processes or compositions used in powder metallurgy
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/003—Apparatus, e.g. furnaces
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/20—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces by extruding
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B33—ADDITIVE MANUFACTURING TECHNOLOGY
- B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
- B33Y30/00—Apparatus for additive manufacturing; Details thereof or accessories therefor
Abstract
Extrusion of feed materials of a high temperature formable non-ferrous metal susceptible to embrittlement during air processing uses an extrusion system having a rotatable wheel and shoe covering part of the length of a groove around the periphery of the wheel to form an arcuate passageway, the shoe having an abutment which substantially closes a second end of the passageway and an extrusion die spaced from the abutment by a die chamber. The process includes pre-heating the feed material to not less than about 390 degrees C in a chamber defined by a feeder device, maintaining a protective atmosphere in the chamber of the feeder device while the feed material is heated. The pre-heated feed material then is passed to an inlet end of the passageway, and drawn along the passageway, to be forced by the abutment into the die chamber and through an extrusion orifice of the die to provide extruded product. having an abutment which substantially closes a second end of the passageway and an extrusion die spaced from the abutment by a die chamber. The process includes pre-heating the feed material to not less than about 390 degrees C in a chamber defined by a feeder device, maintaining a protective atmosphere in the chamber of the feeder device while the feed material is heated. The pre-heated feed material then is passed to an inlet end of the passageway, and drawn along the passageway, to be forced by the abutment into the die chamber and through an extrusion orifice of the die to provide extruded product.
Description
Extrusion of High Temperature Formable Non-Ferrous Metals
Field of the Invention
The present invention relates to a process and apparatus for ion of non-ferrous
metals which enable continuous operation. The invention has particular application to
high temperature formable non-ferrous metals, such as titanium, tantalum and
niobium that are susceptible to tlement during processing in air at elevated
temperatures. As used herein, nce to a metal such as “titanium tantalum” or
“niobium” includes the metal and its . The process has particular application for
the production of titanium rod and wire, but also can be used to produce other
elongate forms of titanium, as well as rod, wire and other elongate forms of other high
temperature formable non-ferrous alloys, including but not limited to tantalum and
niobium.
Background
um wire and rod are extruded from billets produced by the Kroll process. The
Kroll s are batch produced and ive. Wire and rod milling or extrusion from
Kroll billets involve step batch operations which result in low material yields and
low product volumes. It would be desirable to be able to use cheaper feed material, in
particular titanium powder, recycled chips, sponge granules or the like, and to be able
to continuously form te titanium t, such as wire and rod, in increased
product volume, in less processing steps with increased yields and lower process
costs.
Tantalum and niobium are processed via primary and secondary routes. Primary
processing is at very high temperatures and es annealing, melting (or
sintering) under high vacuum to prevent reaction with oxygen and nitrogen that
diffuse into the matrix and result in embrittlement. The primary route involves the
fabrication of billet by vacuum melting methods above 3000°C (2415°C for niobium)
or from cold or hot pressed powder that is sintered at 2000°C under vacuum.
ary processing is typically at room temperature with intermediate
recrystallisation anneals after about 90% reduction to produce small bars for wire
drawing. Conventional processing is thus segmented by batch processes. It would
be desirable, therefore, to produce the final um or niobium wire or rod in a
single ion in a continuous manner and at lower temperatures.
A known process for the production of ium and copper extrusions utilises a
continuous rotary extrusion operation. The main process utilising rotary extrusion is
the “Conform” process. The m process has a number of variants such as those
based on Holton and BWE machines but these hold to the same principles of
continuous rotary extrusion. A recent variant s slightly from conventional
continuous rotary extrusion in that its primary purpose is to provide severe plastic
deformation of feed material without icant alteration of the feed cross section.
The rotary extrusion processes use apparatus of a type consisting of an ion
system having a ble wheel and a fixed shoe which covers part of the length of a
groove around the periphery of the wheel, to form an arcuate eway. The shoe
has an abutment which closes one end of the passageway, while a shaping or
extrusion die spaced from the abutment by a die chamber defines a die orifice. The
feed material at ambient temperature is presented to an inlet to the passageway, at
the end of the passageway remote from the abutment, and on of the wheel
causes the feed material to be drawn along the passageway by frictional engagement
with the wheel exceeding frictional engagement with the shoe. The feed material is
sufficiently subjected to heat and pressure by the frictional engagements to enable
the feed material to be forced into the die chamber by engagement with the abutment
and extruded through the die orifice. Examples of variants of tus of that type
and processes using them are provided in the following US patents:
a) 3765216 and 3872703 to Green, 4101253 to Etherington, 4044587 to Green
et al, 4055979 to Hunter et al and 4061011 to Green deceased et al, all
assigned to United Kingdom Atomic Energy Authority;
b) 4041745 to Moreau, assignor to Trefimetaux;
c) 4552520 to East et al, assignors to Metal Box Public Ltd Co;
d) 4650408 to Anderson et al, assignors to Babcock Wire Equipment Ltd;
e) 5167138, 8 and 5503796, all to Sinha et al, ors to The
Southwire Co; and
f) 7152448 to Zhu et al, assignors to Los Alamos National Security, LLD.
Each of these patents se continuous extrusion of feed material, of elongate solid
feedstock or powder. The metal, when identified, typically is copper and or aluminium
or their alloys, with extrusion commencing with feed al at ambient temperature.
While rotary extrusion processes are used for producing lengths of copper and
aluminium products, this is not without limits on cross-sectional sizes and other
difficulties. However, conditions suitable for operation with copper or aluminium feed
materials have not been found to be suitable for use with high temperature formable
non-ferrous metals susceptible to embrittlement during elevated temperature
processing in air, such as titanium, tantalum and niobium feed materials.
USP ‘253 to Etherington points to the development of fatigue failure of the wheel due
to fluctuating stresses which reach a maximum immediately in front of the abutment
member, but falling to a minimum beyond the abutment . Also, USP ‘745 to
Moreau refers to the large and sometimes prohibitive amount of heat generated by
friction n the feed al and walls of the passageway. Also, dead zones can
form in the vicinity of the die, while energy yield is small due to absorption of motive
energy by heating due to on. Moreau states that for some metals s
drawbacks are serious enough to make the s quite able. We have found
this to be the case when conventional Conform processing is attempted with high
temperature formable non-ferrous metals such as titanium, tantalum and niobium that
are susceptible to embrittlement in elevated temperature processing in air.
US ‘979 to Hunter et al affirms the g of Etherington in relation to straining that
the passageway suffers when its walls are ted to cyclic ing as the
feedstock is compressed. The mechanism is suggested by Hunter et al to be that the
pressure/temperature cycle experienced by the wheel as it rotates, resulting in micro
fatigue cracks in all the groove surfaces. We believe this problem is exacerbated with
um, tantalum and niobium, and other metals to which the t invention
extends, due to the substantially higher pressure levels necessary for its extrusion.
USP ‘520 to East et al outlines the further problem of metal or “flash” extruded
through ary working clearances near the outlet end of the eway. In
addition to necessitating stoppages for removal of the flash, it increases frictional drag
on the wheel and adds to the heat generated by friction and the operating
temperature of various parts of the wheel and shoe members. USP ‘138, ‘428 and
‘796 each to Sinha et al attest to considerable heat generated by the enormous
frictional resistance and ing axial stress encountered by the feed material. Also,
USP ‘138 refers to this real disadvantage in the context of stating that the advantages
of the conform extrusion machine include the provision of a theoretically continuous
extruding process and the use of cold solid or powdered feed material with nce
of any need to t the material prior to its extrusion. That is, the problem of
considerable heat generated by enormous frictional resistance despite the feed
material mutually being at ambient temperature. Also, the conform apparatus is found
according to USP ‘138 to produce extruded products having non-uniform
microstructure and large surface grains which can cause “orange peel” when
subjected to high stress working operations. USP ‘428 and ‘796 add to this problem
recognition that, with extrusion of powder material, the conform apparatus can give
rise to the serious problem of uneven powder flow due to flow turbulence and shear
forces across the passageway. This is due to the shearing forces being higher along
the extrusion shoe, which is fixed relative to the feed al, than along the grooved
rotating wheel. Thus, differential cooling along the passageway can be necessary,
and this would further complicate extrusion from titanium, tantalum and m
powders.
USP ‘448 to Zhu et al extends the range of apparatus providing severe plastic
deformation (SPD) by the technique of equal channel angular ng (ECAP) or
ion (ECAE). Specifically, Zhu et al proposes apparatus providing operation of
the ECAP/ECAE que with the continuous rotary extrusion enabled by Conform
apparatus. The combined apparatus is illustrated as applicable to processing of
aluminium bar. While the apparatus is said to be able to be used with any metal or
alloy work piece, the degree of efficacy of the apparatus with other metals, such as
titanium, and others to which the present invention s, is not apparent.
Also of relevance is the article “Precise Extrusion Technology by Conform Process for
Irregular Sectional Copper” by Tonogi et al, Hitachi Cable Review No-21, August
2002, pages 77 to 82, available at http://www.hitachi-
cable.co.jp/en/about/publish/review/_icsFiles/afieldfile/2005/11/29/2_review13.pdf.
This work points out that, for metals harder than aluminium, problems such as
insufficient tool strength and inferior t y, have limited Conform extrusions
range of application. However, improvements to machinery have made it le to
use Conform extrusion for mass production of copper objects.
Summary of the Invention
The present invention utilises tus of the type described above includes a
rotatable wheel, and a fixed shoe having an abutment and a die orifice as detailed
above. Feed material of a high temperature formable non-ferrous metal is presented
to the inlet at the end of the passageway remote from the abutment, and is drawn
along the passageway by rotation of the wheel for extrusion h the die orifice. As
with extrusion of aluminium or copper and their alloys in such apparatus, the shoe
and abutment attain and are maintained at an elevated temperature by heat
generated by friction and shear deformation of the feed material and, to preserve the
tooling and allow extrusion to initiate, the shoe and abutment are ted.
However, while such heating s extrusion of aluminium and copper, subject to
some limitations such as section, it does not enable effective extrusion of
te product of high temperature formable non-ferrous metals such as titanium,
tantalum and niobium that are susceptible to embrittlement during processing in air.
According to one aspect of the present invention, there is provided a process for
extruding a high temperature formable non-ferrous metal susceptible to embrittlement
during processing in air at high temperatures using apparatus including an extrusion
system having a rotatable wheel and shoe which is positionable to enable the shoe to
cover part of the length of a groove around the periphery of the wheel to form an
arcuate passageway having a first, inlet end and a second end, the shoe having an
abutment which substantially closes the second end of the passageway and an
extrusion die spaced from the abutment by a die chamber; wherein the process
includes the steps of: pre-heating the feed material to a pre-heat temperature not less
than about 390°C in a chamber defined by a feeder device, maintaining a protective
atmosphere substantially free of oxygen and en in the chamber of the feeder
device while the feed material is heated in the feeder device to the pre-heat
ature, passing the pre-heated feed material from the feeder device to the inlet
end of the passageway, and drawing the pre-heated feed material along the
passageway to cause the ated feed material to be forced by engagement with
the abutment into the die chamber and through an extrusion orifice defined by the die
to provide extruded product. The protective atmosphere preferably comprises argon.
In the feeder device the feed material is heated under a protective atmosphere to the
pre-heat temperature. The feed material may be ted to the die orifice at a
temperature substantially in excess of that solely due to friction and shear
deformation. The pre-heat temperature may be substantially in excess of 390°C and,
depending on the form of the feed material, such as in excess of about 760°C up to
about 1140°C for titanium and up to about 1200°C for tantalum and niobium . The
temperature ably is in the range of about 800°C to 1100°C for each of titanium,
tantalum and niobium. However, where ultra-fine grain (UFG) product is required in
particular with titanium, a at ature not exceeding about 650°C,
preferably not higher than 600 °C, can be cial. Also, where the feed material
ses unconsolidated powder the pre-heat temperature may be from about
400°C to at least about 850°C, such as from about 775°C to 820°C.
In another aspect, the invention provides an apparatus for producing extruded product
of a high temperature formable non-ferrous metal susceptible to embrittlement during
processing in air at high temperatures, the apparatus including:
(a) an extrusion system :
- a rotatable wheel having a groove around the periphery of the wheel;
- a shoe positionable to cover part of the length of the groove of the wheel to
form an arcuate passageway having a first, inlet end and a second end;
- an abutment carried or defined by the shoe for substantially closing the
second end of the passageway; and
- an extrusion die carried by the shoe and spaced from the abutment by an
extrusion chamber d by the shoe;
(b) a feeder device which defines a chamber into which feed material is able to be
received and from which the feed material is able to pass to the inlet of the
passageway of the extrusion system;
(c) a heater associated with the feeder device and operable to heat the feed
material while in the r to a pre-heat temperature of not less than about 390°C;
(d) a connection device associated with the feeder device and connectable to a
pressurized source of protective gas to enable maintenance of an atmosphere of
tive gas in the chamber while feed material is being heated to the pre-heat
temperature; and
(e) a device for feeding pre-heated feed material from the feeder device to the inlet
end of the passageway of the extrusion system y pre-heated feed al is
able to be drawn along the passageway by rotation of the wheel and whereby the pre-
heated feed material is forced by engagement with the abutment into the die chamber
and through an extrusion orifice defined by the die to the produce extruded product.
With both the process and the feeder system of the invention, the pre-heat
temperature can vary with variation in a number of parameters. These include the
specific metal comprising the feed al, the nature of the feed material, the cross-
section area of feed material presented to the wall of the passageway, the extrusion
ratio, the speed of extrusion and the extent of flash loss of material. In the case of the
nature of the feed material, this extends to both the high temperature formable metal
chosen, and the physical form of the feed material. Also, while a substantially
constant pre-heat temperature can be maintained once steady state extrusion is
attained, a higher pre-heat temperature can be cial on start-up, with this
progressively sing as steady state extrusion is approached.
The pre-heat temperature needs to allow for the cooling that can occur as the feed
material passes from the feeder device in which the feed material is pre-heated to the
inlet for the passageway. As with conventional extrusion of aluminium and copper by
the m process, erable heat is generated by friction and shear as the feed
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material is drawn along the eway into the die r, and extruded through
the die. Despite the need for the pre-heating of the feed material, it is necessary as in
the conventional Conform s extrusion of ium and copper to provide
cooling to regulate the temperature at critical locations. Specifically cooling is
provided to control the temperature of the abutment which diverts flow from the
passageway into the die chamber, and to control the temperature of the die. However,
the temperature profile from the inlet to the passageway to the die outlet differs from
that obtained by conventional Conform operation for the extrusion of aluminium and
coppeh
With solid, or compacted powder, rod form feed material, pre-heating of the material
may be to a temperature of from about 800°C to . The lower end of that range
is preferred for CP and blended elemental mixtures of Ti alloys such as from about
800°C to 925°C. On start-up, components of the extruder system rapidly heat up to
an l operating temperature, and need to be cooled to retain acceptable steady
state temperatures. Examples of such temperatures suitable for titanium rod form
feed are set out in Tables 1 and 2.
Table 1
Start-up Temperatures (°C)
_ Typical Preferred
200 — 400 250 — 300
300 — 450 320 — 400
A 300 — 600 450 — 55o
DI 300 — 500 350 — 400
100—400 180— 300
Table 2
Steady-State Temperatures (°C)
Typical Preferred
300 — 400 <350
600 — 700 600 — 630
600 — 950 600 — 650
600 — 800 500 — 650
250 — 400 250 — 290
600 — 1000 600 — 750
In Table 1 and 2:
CR designates the coining roll, with the temperatures taken at the roll bearing
housing. The coining roll is adjacent to the inlet to the passageway (in use only when
extruding from rod forms).
SI designates the shoe insert where forming the die block extension;
A designates the abutment;
DI designates the die insert; and
W designates the wheel, with the temperature W (a) taken about diametrically
opposite the abutment and W (b) taken just in advance of the abutment. W (b) is
ult to measure, but generally is about 100-200°C below the feed material pre-
heat temperature.
With the feed material sing pelletised and olidated powder, the pre-
heating temperature may be from about 400 to 1100°C, preferably from about 775 to
820°C. The temperatures at locations within the extruder preferably are as detailed in
Tables 1 and 2. Temperatures may be modified to a lower range in the case of
titanium such as by temporarily ng with hydrogen.
In general the temperature ranges of Tables 1 and 2 are suitable for each of um
and niobium. However, in each case, the temperature at the abutment can range up
to about 1050°C.
To form UFG extruded rod, in particular with titanium typically from as received
powders or pelletised powder pre-consolidated to 60 to 90% of theoretical density,
preferably 75%, but also from fully solid rod feed, the tooling temperatures may be
about the same as set out in the Tables 1 and 2. Powder based feed material may be
preheated up to 600°C in the feeder device for pre-heating, with 0°C preferred.
To form UFG extruded rod from fully solid rod feed, enough feed length must be
passed through the extruder device at 800-1100°C to allow a coating or tyre over the
extrusion wheel, then rod feed may enter the extruder device at a preheat
ature ranging from ambient to as high as 450°C, but the temperature
preferably is from about 370 to 430°C.
lnput line speeds during extrusion can be within the capability of conventional
m extruders for extrusion of aluminium and copper, ranging up to about 0.33
m/s or higher. The output line speeds for a given input speed is controlled by the
extrusion ratio (ER, that is, (feed radius)2/(product radius)2) and flash losses. It is
found for example that ER values of 0.8, 1, 1.8, 4 and 16 can be achieved in
extruding from solid titanium bar of 12 mm diameter, using a BWE 285 Conform
machine that has been rebuilt but does not differ in any relevant regard from its
al form. ER valves of 0.8 to 4 are possible with the die insert (DI) pre-heat
shown in Table 1. An ER value of 16 would benefit from a higher DI pre-heat such as
about 600°C. In each case the extruded product was of satisfactory quality, and
produced without excessive material loss as flash, giving a product length of ER times
the feed length, after allowance from flash.
For CP um, processing above the alpha transition temperature of 880°C, such as
at about , results in a heterogeneous microstructure. With um , the
transition temperature varies with composition, although apart from beta alloy
itions, a heterogeneous microstructure is also attained when processing in the
beta field.
The above indicated ER values from solid rod also can be achieved with consolidated
powder rod form feed material and with unconsolidated and pelletised powder feed. In
each case there of course is a different respective product length from a given input
feed length due to the idated powder rod form having less than the theoretical
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density and olidated and pelletised powder, which have an even lower mass
density.
With rod form feed material of consolidated elemental alloy powder, or unconsolidated
elemental alloy , processing results in an geneous tructure. The
predominance of CP titanium as a ductile matrix dominates the extrusion behaviour
of elemental titanium alloy powder. This is due to the CP titanium content, as alloy
additions remain substantially as undissolved secondary particles until they are
removed by a subsequent homogenisation anneal and the extrusions take on the
properties of the alloy material. Consolidated and unconsolidated alloy powder of
each of titanium, tantalum and niobium differ from elemental alloy powder in that the
chemistry of the powder starts off with the alloy chemistry and homogeneity. The alloy
chemistry and hence alloy ties in both these cases will alter the optimum
extrusion preheat temperature, extrusion strain and strain rate necessary for quality
product, but the same general rules apply as for fully solid alloy rod feed.
Powder for use in the t invention, such as that of titanium, tantalum and
niobium, whether consolidated into rod form feed material or as olidated feed
material, may be of a range of different types, or even a e of at least two types.
In the case of titanium, the powder may comprise titanium hydride, titanium
hydride/dehydride (H/DH), titanium sponge, atomised powder, pelletised powder,
granules and sponge granules, and other forms of particulate titanium feed, including
recycled feeds of appropriate . H/DH, sponge-like powder and pelletised feeds
have been found to be well suited for use in the present invention. The feed material
most preferably has a low chloride content, such as less than 100 ppm CI, to
eliminate porosity in the extruded product. However, for applications such as
remelting the product wire under high vacuum as with additive manufacturing devices,
chloride levels may not need to be so restricted.
With each form of feed material for the present invention, the metal may be any of the
lly recognised grades, such as ASTM grades 1 to 4 for commercial purity (CP)
titanium, and/or any of the grades 5 to 38 um alloy compositions, or alloy
containing high s of titanium such as the near 50 atomic percent shape
memory alloy TiNi. In the case of consolidated or unconsolidated powder, extruded
product of such titanium alloy grade can be produced from a powder mix of
appropriate proportions of master alloy and elemental powders; such as 60wt.%Al-
40wt.%V alloy powder d with CP titanium powder. Consolidated or
unconsolidated powder may also be of the form of alloy powder. In each form of the
feed material, it may se or provide an alpha, alpha-beta or beta alloy.
(a) Powder Feed Material
The primary purpose of a powder feeder device is to deliver regulated free flowing
powder feed material, heated up to a temperature as high as about 1000°C (in order
to lower the flow stress of titanium, tantalum or m) to near the apex of the
grooved wheel with minimal contamination to the product. The secondary purpose is
to deliver the heated powder feed material in an occupationally safe manner that does
not result in fire or explosion.
The feeder device may deliver the powder feed al to the wheel groove in a
radial manner (such as by direct gravity feeding) or in a tangential manner (such as
by a ory ). However, to maintain a regulated flow and provide heating to
the titanium, tantalum or m powder, an intermediate feed delivery can be
employed, allowing a tilt adjustment. A hopper containing a sufficient quantity of
powder feed al may travel with a kiln as the latter is tilted. The hopper can also
be elevated, whilst maintaining its angle with the kiln, to alter the depth of the powder
pile in the kiln that emerges from the shoe-shaped spout at the discharge of the
hoppeh
In one form, the feeder device may include an adjustably inclined tubular rotary kiln
having a heating device by which powder feed material is able to be heated as it
passes from an inlet end to an outlet end. The powder preferably is guided by a
spout, which has a shoe-shaped dome at its end, for flow from the outlet end of the
kiln, to a location in the groove of the ng wheel which is adjacent to the inlet end
of the passageway. The feed device may be in the form of a feed hopper operable to
supply powder feed material to the inlet end of the kiln via a shoe-shaped hopper
discharge, to enable the material to flow along the kiln and pass, from the outlet end
of the kiln, to the inlet of the passageway via a spout hopper. The system comprising
2012/000231
the kiln and the feed and spout hoppers further includes a heating device or furnace
and is connectable to a source of inert gas. The system is tiltable through a le
angle from horizontal, such as from 2° to 45°, to allow variation in the speed of
powder flow along the kiln, to raise the inlet end relative to the outlet end. The spout
hopper may be fixed relative to the kiln and extend fonNard at an angle of about 5°
from the vertical and be shaped such that a shoe-dome is at its end to charge the
powder forward and allow the powder to slide unobstructed. The lower surface of the
spout hopper traces the surface contour of the grooved wheel with a gap of no more
than about 0.5 mm. The entire feeder unit may be modular and be set at the feed end
of the extruder at an appropriate height and on to allow powder feed material to
a location in the groove of the rotating wheel, which is adjacent to the inlet end of the
passageway.
The kiln preferably is connectable to a source of a protective or inert gas, such as
argon, to enable the gas to maintain slight over-pressure in the kiln, thereby to protect
the powder from exposure to oxygen and nitrogen in the course of being heated. The
inert gas preferably is supplied to the inlet end of the kiln, so as to flow co-currently
with the powder. With this co-current flow, the inert gas is able to discharge with the
powder from the spout hopper. This provides protection for the heated powder as the
powder is drawn into the passageway, and remains until expelled as the powder is
idated, by sing exposure of the powder to oxygen and en.
The kiln may be made of a range of suitable materials. One suitable material is steel,
preferably stainless steel, such as ferritic ess steel. However, suitable steels are
limited to a maximum powder heating temperature of about 1000°C due to reactions
with the feed material, such as a titanium-Fe eutectic reaction. Alternatively, the kiln
may be made from, or lined with, silica, partially stabilised zirconia or with other
material that does not chemically react with the feed and is thermally shock resistant
such as a suitable ceramic material.
The feed hopper also may be connectable to a source of supply of protective gas,
such as argon. This lly is to flush other gases from the feed hopper. However,
with discharge of powder feed material from the feed hopper to the rotary kiln, the
protective gas is able to flow from the feed hopper with the feed material, and into the
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kiln, precluding the risk of ingress of atmospheric air and contamination by oxygen or
nitrogen.
Powder feed material may be stored in the feed hopper, which preferably is a gravity
hopper with a hopper angle determined according to the powder flow ties. A
funnel deck may be added to the interior of the hopper to act as a lining to allow flow
according to the flow properties of the powder if the hopper angle has been
determined according to a powder of a different type. Otherwise the hopper may be
equipped with vibrating tappers to prevent ng of powder that may occur due to
the use of titanium, tantalum or niobium feed material with flow properties differing
from powders used to determine the hopper angle or funnel deck. Protective gas such
as argon can be fed at the top of the feed hopper and is fed at the upper, inlet end of
the rotary kiln. A control system preferably ensures that the kiln cannot begin to
rotate, be heated or be fed with feed material until the protective gas flow has reduced
oxygen contents below an alarm setting. For e, in the case of titanium powder
feed material, an oxygen level of 4 volume % will allow titanium to burn, and the alarm
setting must be well below that level.
The feed hopper preferably has a sliding gate that fully opens only after tive gas
flow has sufficiently lowered oxygen levels within the rotary kiln and a secondary
sliding gate may then be adjustable to regulate the flow of feed material into the top of
the kiln. The control system preferably ensures that the adjustable sliding gate is not
able to open until the kiln is sufficiently heated and that heating does not commence
until rotation of the kiln has been initiated to allow sliding bearings to take up
movement due to kiln expansion.
Both protective gases such as argon and titanium, tantalum or m powder feed
material are fed into the cold top section of the rotary kiln. Feed al preferably is
fed at a lower point than the protective gas to prevent the gas from disturbing the feed
al powder and creating a powder cloud. A powder cloud may break
containment at the discharge point above the grooved wheel and pose an ion
risk, while it also lowers the efficiency of mass transfer.
WO 19196
When powder feed material is heated in the absence of air, such as above 600°C in
the case of titanium, it may sinter and stick to itself, especially in the presence of
external stress, thereby hindering free powder flow. r, by delivering the
powder feed material from a feed hopper at ambient temperature to the interior of the
rotary kiln, the shearing action of the rotation as well as the force of gravity allows the
continuous flow of powder and allows it to fall into the spout hopper to be delivered to
the d wheel. The shearing action also allows for the feeding of powders or
particulates of various size distributions and morphologies. The rotation and tilt angle
also regulate the mass flow of the powder and thermal transfer to the powder. A
preferred kiln tilt angle of 2° allows a steady powder level through the kiln. A preferred
outlet of the spout hopper is as close to al as possible to provide free movement
of the powder into the groove of the wheel. The ability to tilt the kiln at greater angles
allows for the alteration of thermal and mass flows for a y of powder types with
differing flow properties. At the conclusion of powder flow, a scraper located beneath
the shoe-shaped hopper discharge can be slide forward to clear the kiln of any
residual powder.
Both the feed hopper and spout hopper preferably are held stationary relative to the
rotary kiln. A sliding gas seal is formed at the feed hopper end at the inlet of the
rotary kiln and the spout hopper encloses the discharge end of rotary kiln whereby the
rotary kiln remains tiltable due to a flexible connection between the kiln and spout
hopper. The spout hopper then forms a sliding seal with the grooved wheel of the
extruder. The overpressure of protective gas in the hoppers and in the kiln acts to
prevent the ingress of t atmosphere.
Once the powder feed material leaves the feed hopper it moves by shearing action
from the cold section of the rotary kiln to the hot section, the residence time of the
powder dictating its final temperature. The receiving angle of the spout at the
discharge of the rotating kiln is at least the same as the feed hopper angle, but is
preferred at 5° from the vertical. This angle, and the onal tilt provided by the kiln
prevents powder hang ups in the area. However, a lump breaker ting of a rod
or blade that can be elevated or lowered within the spout hopper allows for the
breaking of lly sintered lumps. The application of a tapper at the spout hopper
further breaks up any agglomerates that may form by sintering, and may take the
form of a vibratory mesh, particularly for combinations of finer s and higher
temperatures, but is usually not required. The tilt of the spout hopper may be fixed
ve to the tiltable kiln with the kiln discharging into the fixed spout hopper. This
allows a constant receiving angle of the spout and permits rge from the spout
for powders with lazy flow behaviour. Further, regulated protective gas inputs to the
hopper also minimises a pressure drop from the top to bottom of the hopper, enabling
even own of the powder pile. The spout hopper preferably forms a leaking seal
over the wheel that allows additional build up of protective gas back pressure within
the kiln. The spout hopper and its spout preferably are also thermally insulated to
prevent heat loss and may also be onally .
Heating of powder feed al can be by use of a variety of different heaters,
depending on the al of construction of the rotary kiln. The heating may be by,
radiative heating or by using any other continuous heating method or system. In one
convenient arrangement, heating may be conducted at two or more locations along
the length of the kiln which ably are located away from a relatively cool inlet
end, towards the outlet end, of the kiln.
The entire feeder assembly and its ents are all at the same earth potential as
all other components, are interlocked to shut off mass flow in the event of protective
gas loss enabling an unacceptable increase in oxygen volume percentage, and the
control system may include sensors for monitoring the oxygen content in the
assembly.
(b) Rod Form Feed Material
Rod or bar form of feed material may be of solid metal or of consolidated powder of in
excess of 60% of the theoretical density. In each case the elongate feed material may
be fed to the er apparatus either as isothermally, or as continuously, heated
lengths. The heating may be by using a RF induction heating arrangement,
continuous electric resistance heating or using any other continuous heating method
or system. The rate of heating preferably is tuned to the throughput of the extruder
apparatus. The heating may be conducted with the elongate feed material held in a
suitable containment vessel. The interior of the vessel first is flushed with a protective
gas, such as argon or other inert gas, and with the elongate material positioned in the
vessel, a positive re of the gas is established, and heating is ced.
A silica tube may act as a nment vessel for protective gas, such as argon, to
stop the feed material from reacting with oxygen and nitrogen at high temperatures.
tive gas is particularly necessary for rods of consolidated powder feed material
that are porous and susceptible to high penetration of interstitial contamination. The
feed material also does not react excessively with a silica vessel at temperatures up
to 1100°C for the t exposure times allowing the feed material to be transported
freely by sliding without sticking to the vessel walls. Other materials could be used for
manufacture or lining of the containment vessel, as long as they did not react
excessively with the metal of the feed material and its alloys and can tolerate the
temperature variations involved in preheating and feeding.
Rod forms when isothermally or continuously heated within the containment vessel
are delivered to the extruder apparatus. A feeder unit preferably feeds lengths of rod
forms to that tus for continuous extrusion. Rod forms of consolidated powder
may be loaded into a cold g zone as suitable lengths, with protective gas
purged and then loaded into a hot zone for preheating. The feeding of these
consolidated powder lengths may be automated, with continuous feed to the hot zone
at volume through puts that match the extrusion output of the extruder apparatus. The
extruded product from extrusion of rod forms of consolidated powder is able to be fully
dense or very close to fully dense and with no nt remnant of joining between
successive s. Feed rods of solid feed material also are able to be fed as
continuous lengths, so a feed valve and flushing chamber need not be used. The rod
forms of each type are to be left in the hot zone until heated through. The dwell time
to the environment temperature allowed the lengths of consolidated powder to
partially sinter and be at first pushed and then dragged through the extruder as a
single length. As the feed exits the hot zone and enters the rotary ion tooling,
the oxygen in the neutral atmosphere may rise slightly to about 30 ppm. A counter
flow of protective gas such as argon through the tooling may be uced to further
reduce interstitial contamination during the period the sliding gate is open.
2012/000231
To ensure homogenous product the variation in the preheat temperature along the
feed length preferably is < 150°C for feed material, such as CP titanium, preferably
i20°C, until a steady state prevails.
The rod-form g system is interlocked to maintain a neutral protective
atmosphere with oxygen levels below 4 volume % (for fire prevention) and 0 to 32
ppm to minimise contamination in the product to not more than a mild surface blueing.
(c) Extruder Apparatus for Powder Feed
The er apparatus can be of a variety of forms, such as detailed in the prior art
discussed above, including the CAE variant of USP ‘448 to Zhu et al.
However, some adaptation is necessary or desirable to facilitate use of the extrusion
apparatus in the context of the process and extruder system of the present invention.
As indicated, the feeder device for powder feed material may discharge close to or
forward of the apex of the grooved wheel. In order to fit the powder feeder device to a
BWE m type of machine and to allow feeding at the wheel apex, any coining
roll housing preferably is removed. In one arrangement, a clamping plate assembly is
attached to a top plate that is mounted to the frame of the extruder apparatus. The
clamping plate assembly may be grooved and provide room for the powder feeder
device to function. Also, the clamping plate assembly can act as a loading point for
the clamping of the shoe of the apparatus. The clamping plate also can allow the
uction of a r flow of tive gas. A hole in the clamping plate allows for
the positioning of the spout hopper.
The spout hopper and the groove in the clamping plate can allow for flood feeding by
constraining the spread of the powder above the wheel and keeping it in the wheel
groove and directed under shoe inserts. A tongue at the rear of the spout hopper
intrudes into the wheel groove and allows only forward movement of powder. The
lower edges of the spout hopper may trace the surface contour of the wheel with a
tooling gap such as of ~0.5 mm, which also ses powder spillage and loss.
The shoe inserts may be of usual form. The gaps between the shoe inserts and the
wheel are the same as usual for extruding from rod forms, with 0.5 mm or less the
flash gap to minimise powder loses prior to consolidation and maximise tyre formation
over the groove. A tongue on the leading end of the entry block preferably is removed
for the powder feed to maximise the receiving volume to the consolidation zone. The
shoe insert tongue in this case performs the function of compaction of the powder
onto the surface of the wheel groove in order to form a good onal interface. This
allows the compacted powder to be driven forward to the die chambers tooling.
It may prove advantageous to install a coining roll in the groove of the clamping plate
in the ty of the spout hopper to maximise the chances of tyre formation,
particularly for spherical particles that of any morphology have the highest flow rate,
lowest residence time and lowest surface area for inter-particle locking during
compaction. This can be achieved readily enough by exchanging the clamping plate
assembly or modifying the shoe inserts for a coining roll. A driven coining roll would
also provide positive a to the powder to allow forward movement into the groove
and lessen powder ge.
Because the clamping plate encloses the powder feed above the wheel, it is a simple
matter to direct additional streams of protective gas, such as argon, to ensure
atmosphere protection of the powder is ined. The frame area around the
ion wheel preferably is encased in baffles to ensure a positive pressure of the
gas is supplied around the wheel during extrusion.
(d) Extruder Apparatus for Rod Form Feed
As with the use of powder feed material, the er apparatus for rod form feed
al can be of a y of forms, such as detailed in the prior art discussed
above, including the ECAP/ECAE variant of USP ‘448 to Zhu et al. Again, some
adaptation is necessary or desirable to facilitate use of the extrusion apparatus in the
context of the process and extruder system of the present invention. In reference to a
BWE configured Conform device, the important components of the ion
apparatus are the (i) grooved wheel, (ii) shoe inserts, (iii) abutment/die chambers, (iv)
g roll and (v) scraper blades. The critical tooling component of the abutment
tooling most preferably is ctured from super alloy, tungsten rhenium alloy, or
other material that can withstand high stress and temperatures up to 700°C to
minimise tooling deformation and wear.
(i) The grooved wheel may be fabricated from tool steel, such as H13 tool steel.
The groove may be a smooth U-shaped groove, such as about 15 mm deep and
about 13 mm wide to be suitable for receiving 12 mm er rod feed. The
“stickiness” of high temperature formable non-ferrous metal, such as titanium,
um or niobium preheated to 2 580°C is sufficient to allow adherence of the feed
material to the wheel and the formation of a tyre of the feed material in the wheel
groove, as is highly beneficial in ing successful extrusion
(ii) During extrusion the shoe insert tooling can heat to a temperature as high as
700°C, and it preferably is manufactured from a high temperature resistant material,
such as Rene 95 super alloy. Inserts ctured from H13 steel were found to be
sufficient for runs totalling only tens of meters of product. The temperature of the shoe
inserts may be ted by controlled application of a cooling fluid to the rear of the
tooling inserts. The shoe inserts have a tongue that protrudes into the wheel groove
that has side nce of 0.5 mm. The tongue of the entry block serves to straighten
and guide the rod to the . The function of a die block extension tongue is to
deform the rod feed more firmly into the groove to increase the frictional interface
between the feed and the wheel groove. It does this by having a taper that decreases
the distance between the top of the tongue and the bottom of the wheel groove the
closer the feed gets to the abutment. The tongue of the entry block is essentially
superfluous when extruding from rods of compacted powder as the g roll forms
these functions. The entry block may be slotted to allow the lowering of the coining
roll to the bottom of the wheel groove. The clearance for feeding between the entry
block tongue and wheel groove may be about 12.3 mm decreasing to about 12mm for
the groove dimensions detailed above. Similarly, the feeding gap between the die
block extension tongue and wheel groove may be about 12 mm decreasing to 8.0 to
mm. The clearance of the sides of the entry block shoe insert and the top of the
wheel may be about 1.0-2.3 mm decreasing to 0.5 mm and the clearance between
the die block extension shoe insert and the top of the wheel maybe about 0.5 mm.
(iii) The abutment/die chambers tooling may be manufactured as a single piece for
optimum heat dissipation of the nt, but preferably the abutment may be used
as an insert into the die chambers. The temperature of the abutment can be regulated
by controlled application of a cooling fluid to the rear of the abutment. The abutment
tooling preferably is ctured from high strength high temperature resistant
material such as Rene 95 super alloy, or a tungsten-rhenium alloy such as W-25%Re-
) for high hot strength. Similar high temperature stable materials should
suffice, including magnesia lly stabilised zirconia, which is also reasonably
chemically stable with titanium and other high temperature formable non-ferrous feed
materials, such as tantalum or niobium, susceptible to embrittlement during
processing in air at high temperatures. Wear resistance is more al for the die
chambers than high strength, so Rene 95 die chambers most preferably have wear
facing inserts such as of magnesia partially stabilised zirconia (Mg-PSZ) or a coating
of partially stabilised zirconia, or r wear resistant layer with low reactivity with
titanium and other feed materials, such as tantalum and niobium and a good thermal
and lattice match to the super alloy. The Rene 95 abutment and die chambers tooling
preferably is subjected to a subsolvus solution treatment and aged to produce a
precipitation hardened and fine grained microstructure for the optimum strength and
wear resistance. The clearance between the wheel and the die chambers should be
set between 0.1 mm and 0.5 mm (flash gap), preferably 0.3 mm. The reduction die, or
die insert inside the die chambers, preferably was a 120° included angle for titanium
or 45° included angle for tantalum and neodymium, and may be manufactured from a
tool steel, such as H13 tool steel. Hard facing of the insert die about the included
angle and land improves product quality and tool ity.
(iv) The coining roll preferably is manufactured from a tool steel such as H13 steel,
and adjusted such that the coining roll could be lowered as far as geometrically
possible to the bottom of the wheel groove. Forced g of the coining roll gs
is also preferred.
(v) The r blade surfaces responsible for ng flash may be
manufactured from H13 tool steel, but this is only good for tens of meters of extrudate
product, so should be ably manufactured from a superalloy, such as Rene 95,
or coated with a wear ant layer, such as PSZ or other hard wear resistant layer
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with tolerable reactivity with titanium and other feed materials, such as tantalum and
niobium. The gap between the scraper blades and the top of the wheel should be the
same as the gap between the die chambers near the die insert orifice and the top of
the wheel or preferably 0.125 mm greater. If the gap between the die chambers and
the wheel is greater than about 1.1 mm, there is danger of the tyre being pulled free
of the wheel groove by the scraper blades and the wheel ceasing its rotation due to
seizing.
Extruding rod forms of cold tically pressed (Cleed) or otherwise pre-
compacted powders requires adjustment of the gap between the coining roll and
bottom of the grooved wheel to allow hot compaction of the rod to 75-100% density,
preferably 100%, and to achieve sufficient frictional interface of the rod with the wheel
groove to enable the rod to be driven fonNard to the nt and extruded through
the die insert.
(e) Extrudate Discharge
With each type of feed material, the extrudate is at a temperature in excess of 600°C
when it exits the die. The extrudate requires cooling, maintenance of atmosphere
tion and isolation from the operators. To fulfil these functions, an te
rge vessel filled with flowing protective gas, such as argon preferably is
employed as an outlet from the extruder assembly. The extrudate can be grabbed
once it safely exits the discharge vessel and is at a cool enough temperature. Once
grabbed it can, be placed under tension to keep it ht and spooled without either
ive surface contamination or danger to the operator.
The discharge vessel may be filled with a flowing protective or neutral atmosphere,
such as argon, to minimise contamination. The discharge vessel has a length such
that the need for forced cooling within the vessel is removed or delayed until the
extrudate is at a sufficient low ature. This allows for suitable venting of steam
and possible en formed from water dissociation if forced cooling by water is
used beyond the discharge vessel. atively, water may cool the exterior of the
vessel and hence the extrudate product thus in contact. Titanium can react with water
based coolants and such coolants can contaminate the titanium with hydrogen and
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cause surface oxidation. Above 700°C explosive combustion of dissociated hydrogen
is le. Steam can also travel back up the line and the hydrogen evolved can
react with the powders and contaminate the t. Thus, a contained protective,
neutral gas atmosphere arrangement needs to be employed. The discharge vessel
may have a clamped gas seal that can be opened and the discharged vessel moved
away if required. Such a protective neutral gas atmosphere is desirable with extrudate
of all non-ferrous high temperature formable feed material.
In order that the invention may more readily be understood, description now is
ed to the accompanying drawings in which:
Figure 1 is a schematic side elevation of a feeder device for delivering to an er
assembly rod form high temperature formable non-ferrous metal feed material, such
as titanium, tantalum or niobium;
Figure 2 is a central sectional view through an extruder assembly for operation with a
feeder device as in Figure 1;
Figure 3 is a central sectional view of the abutment/die chamber of the assembly of
Figure 2, shown on an enlarged scale;
Figures 3A 3B and 30 also show tive isometric views of an abutment insert
and a multi-strand version of a die insert used to extrude multiple wires of narrower
diameter;
Figure 4 is a schematic side elevation of a powder feed material feeder device;
Figure 5 corresponds to Figure 2, but with the assembly set up to receive powder
feed material from the device of Figure 4;
Figure 6 is a lly exploded schematic in the perspective view of detail of the
arrangement of Figure 5;
2012/000231
Figure 7 is a schematic representation of the extruder ly of Figure 2 or Figure
, illustrating the arrangement for exiting ed product;
Figures 8 and 9 are respective perspective views of a r device used with the
extruder of Figure 2 and 5; and
s 10 and 11 are perspective views of respective components of the scraper
device of Figures 8 and 9.
With reference to Figure 1, the feeder device 10 shown n operates by ing
rod form non-ferrous, high temperature formable feed material, such as titanium,
tantalum or niobium feed material at the right hand end. The feed material
sses through the device 10 and ultimately issues from the left hand end and
enters extrusion assembly such as shown in Figure 2.
The device 10 has an elongate tubular vessel 12 which has successive sections able
to be isolated from one another. The sections comprise an unheated, or cold loading
zone 14, into which feed al initially is received, an intermediate hot or heating
zone 16, and an outlet zone 18 from which feed material passes to the extruder
assembly. Zone 14 is able to be isolated from zone 16 by a feed valve 20, while zone
16 is able to be isolated from zone 18 by a sliding gate 22. The loading zone 14 is
adapted to hold feed material 24 in an atmosphere of protective gas such as argon.
The zone 14 has a flushing chamber 26 in which the material 24 is able to be isolated
while exposed to the protective gas. The inlet end of the zone 14 has an airlock 28
through which material 24 is able, while feed valve 20 separates zone 14 from
zone 16. Airlock 28 has a connector 30 connectable to a pressurised source of the
protective gas (not shown), as well as a sleeve 32 through which a push rod 34
extends. A continuous flow of protective gas, maintaining a slight over-pressure in
airlock 28 when closed and in chamber 26, is able to be provided via connector 30,
with the gas discharging, under control ining the over-pressure, via an outlet 36
from chamber 26. The over-pressure in chamber 26 assists in maintaining a
protective atmosphere within zone 16, during opening and closing of feed valve 20.
Also, with rod form material 24 of compacted powder, it assists in flushing air from the
porous feed material. The maintenance of a protective atmosphere in zone 16 is
otherwise ensured by inlet 39 connected to a pressurised source of protective gas
(not shown).
The airlock 28 is able to hold a supply of rod form lengths of feed material 24. When
required, the s are advanced in turn by push-rod 34, from airlock 28, into
chamber 26 and ultimately through valve 20 and into heating zone 16. A heater 38 is
associated with zone 16 and is operable to heat each length of feed material 24 so
that each is at a required elevated temperature when material 24 s the
extruder ly. With gate 22 open, the push rod is able to maintain an end to end
series of lengths of material 24 passing to the er assembly.
The zone 16 also has an inlet connector connectable to a pressurised source of
protective gas. Again, the gas is ed so as to maintain a positive overpressure in
zone 16, and also in zone 18. Gas is able to pass from zone 16 to 18 via a small hole
in sliding gate 22. Thus, the gas is able to issue from the outlet end of zone 18 and
continue to isolate the heated feed material from other gases prior to entering the
extrusion apparatus. However, as depicted by the arrow at the left-hand end of Figure
1, further protective gas may be supplied at the outlet end.
The vessel 12 may be made of any suitable material, such as silica, a le steel
lined with silica, or a ceramic. The heater 38 may be of any suitable type, such as an
RF induction heating arrangement, a continuous ic resistance heater, or any
other suitable heater system. The heater 38 may be external to the vessel 12, as
depicted in Figure 1, or internal. The push rod system may be of a magazine type to
flushing r 14 with an oversupply of rods in vessel 12 to maintain a pre-heated
rod feed supply to the feeding speed of the extruder. Alternatively, rapid g may
be employed such as via an RF induction heating source to maintain a pre-heated
feed supply to the extruder.
Figures 2 and 3 show a sectional view through an extruder assembly 40, taken on a
l plane through the middle of the peripheral groove 42 of a wheel 44. As
shown, wheel 42 is rotatable on axle 46 in the clockwise direction in the view of
Figure 2, as shown by the arrow A. Adjacent to wheel 44 assembly 40 includes a
shoe 48 pivotable on shaft 49 to the in-use position shown in Figure 2. In that
2012/000231
position, an upper face of shoe 48 bears against shoe inserts 50 and 52 and die
chambers 54 that are held in place by insert locking plates 51. The shoe 48 is held in
position by a clamping load depicted by arrow B. Around an arcuate extent of shoe
48 facing towards groove 42 of wheel 44, shoe 48 carries an entry block 50, die block
extension 52 and die chambers 54 that fit into groove 42. A coining roll 56 guides the
feed material 24 to the entry block 50 and s oppositely to wheel 44 as shown by
arrow C. The entry block 50 and die block extension 52 guide and draw the feed
material 24 along a tapered passageway they define with groove 42, that is, the
incremental cross section the feed has to fill with the groove is reduced as it
approaches abutment 57 by tongues 55, which are a part of entry block 50 and die
block extension 52 that intrude into groove 42. The abutment 57 closes the end of the
passageway and forces the advancing feed material 24 to divert outwardly into a die
chamber or die chambers expansion cavity 58. The or each chamber 58 holds an
extrusion die 60, retained by annular locking bolt 61 through which product 64
extruded by die 60 issues.
The feed material 24 pushed from feeder device 10 is drawn into assembly 40 by
opposite on of wheel 44 and roll 56 as shown by respective arrows. on of
wheel 44 and roll 56 presents the feed material 24 to the inlet to the passageway
defined by wheel 44 and shoe 48. The rotation of wheel 44 forcefully draws the
material 24 along the passageway and forces the material 24 against abutment 57.
The surface 57a of abutment 57 diverts the feed material outwardly into die chamber
expansion cavity 58 and, from chamber 58, the feed material 24 is extruded h
the orifice 60a of extrusion die 60. The abutment e 57a is in a plane which
preferably is non-radial with respect to wheel 44. The plane preferably is at an angle 0
to a radial line R which is co-incident with the centre line of die 60, to generate a force
component acting to divert feed material from groove 42, and through die chamber 58
and die 60. The angle 0 ably is from about 6° to 21°. An isometric view of an
alternative insert form of abutment 57’, shown in Figure 3A, slides into the die
rs via a dove-tail groove. The insert abutment 57’ is held in place by
ssion within the dove tail groove and by shoe 48. An alternative form of die,
shown as 60’ in Figure 3B and BC may be used for multi-strand extrusions of narrow
diameters of 3 mm and below. The orifice 60a of extrusion die 60 may be ical in
cross section instead of round or even rectangular to se the relative surface
area of such wire extrusions, typically of titanium, that may be exposed to an e-beam
when used as feed within e-beam additive manufacturing facilities, and the same
applies to the orifices of die 60’.
As with conventional Conform extrusion of aluminium and copper, some non-ferrous
high temperature formable feed material is extruded as flash h the narrow gaps
along each side of the passageway between the entry block 50, die block ion
52, die chambers 54 and the side walls of the groove 42. Also, some flash can
extrude between groove 42 and the sides of abutment 57. This material may be
stripped from wheel 44, at a location beyond abutment 57 in the direction of rotation
of wheel 44, by a blade of a scraper 62. A preferred form for blade 62 is shown in
s 8 to 11.
Figure 4 shows a feeder device 70 for feeding powder feed al to the groove 42
of the wheel 44 of an extruder assembly as in Figure 2. Further detail is shown in
Figures 5 and 6. The device 70 has an adjustably inclined tubular rotary kiln 72. The
feeder device 70 may be positioned to the extruder by a schematically represented
modular frame by nt in directions depicted by arrows H and H’. The incline of
kiln 72 may be adjusted by its mountings on the modular frame 89. A feed hopper 74
is located at the upper inlet end of kiln 72, while the lower, outlet end of kiln 72 is
ble within a spout hopper 76 having a shoe-shaped forward section 76c centred
over groove 42. The hopper 74 holds a supply of powder feed material. By operation
of an auto shut sliding gate 80 and g feed gate 82, hopper 74 is able to
discharge into kiln 72 via the shoe-shaped hopper discharge 74a as controlled stream
of the feed material, indicated by the arrow D. Hopper 74 may be raised or lowered
via a slot (not shown but indicated by arrows J) to alter the volume underneath the
hopper discharge 74a to form a constant powder height. The shoe shaped dome of
hopper discharge 74a allows the powder to accumulate and slide without hang-ups
and pauses in flow. At the conclusion of powder flow, a scraper 81 can pass under
the hopper discharge 74a when the latter is moved up in direction J, to clean the kiln
of al powder. on of kiln 72 by a drive system (not shown, but represented
by the arrowed circle E) advances the feed material through kiln 72 so as to be
directed into groove 42 of rotating wheel 44.
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The device 70 includes a heater 84 for heating feed material in kiln 72. The heater 84
is in two stages 84a and 84b which heat the powder in respective sections of kiln 72.
As kiln 72 rotates, the powder tends to be drawn up the side of kiln 72 in the direction
of rotation. This can be controlled by adjusting the rotation speed and inclination of
kiln 72. A shallow angle of inclination of kiln 72 to the ntal, even as low as about
2° allows most even feeding. A funnel deck 73 may be placed as a liner within hopper
74 to maintain powder flow according to the properties of the powder if the hopper
angle 6 has been determined for a different powder currently not in use. Hopper 74 is
provided with an air ed tapping device (not shown, but depicted by double
headed arrow F), to prevent bridging of feed material in hopper 74 if the hopper angle
6 or funnel deck have not been designed for the properties of the feed material. Also,
at the upper end of hopper 74, a connector 88 is provided for connection of a gas
such as argon, to provide a protective atmosphere feed material in hopper 74 and for
its flow into kiln 72. For the same , a supply 90 of protective gas is provided for
flow into and along kiln 72 from the upper end, as depicted by arrow G. The gas,
such as argon, maintains a protective atmosphere throughout kiln 72, with the gas
g with the feed material in its flow through spout hopper 76 to groove 42. Powder
flow from the kiln discharges into spout hopper 76, where it meets the spout hopper
wall 76a inclined at about 5° from the vertical. The powder continues to slide against a
spout hopper tongue 76b, which is a uation if the wall surface 76a, that intrudes
into and matches the profile of the wheel groove 42 with a clearance of no more than
0.5mm. The powder can accumulate in the spout hopper by gravity and forward
movement of wheel 44 and is contained by the lower surface of the spout hopper 76
that s the contours of the wheel 44. (The contour matching is more clearly
shown in the tic Figure 6.) The powder accumulates in the shoe shaped
forward section of the spout 76b and moves forward into the wheel groove 42.
Preferably a lump breaker rod 81a can be ed to break up any lumps due to
sintering as the powder discharges from the kiln. Also, as with hopper 74, there may
be a tapper F’ mechanically connected to spout hopper 76 to further assist with break-
up of sintered agglomerates from particularly fine powders such as H/DH powders
less than 150 microns and/or at pre-heat environment temperatures greater than
approximately 750°C. The tapper F’ may be ted by pressurized air, as with
tapper F of hopper 74.
As shown in Figures 5 and 6, flow of feed al to groove 42 passes opening 92,
93 in respective clamping plate 94 and shoe insert locking plate 95 (a modification of
insert locking plates 51). Also, as depicted in Figure 5, further protective gas such as
argon may be supplied down plate 94, to assist in protecting the feed material as it
passes from the spout hopper to the passage defined between wheel 44 and entry
block 50, die block extension 52, the tongues 55 of entry block 50 and die block
ion 52 and die chambers 54 of shoe 48.
Figure 7 is a sectional view taken on a central plane through wheel 44 in the extrusion
system of Figures 2 and 5. There is shown an outlet duct 96 of shoe 48 through
which extruded product 64 issues beyond the die 60. An adjustable clamp ring 96a is
secured on duct 96. Also, an elongate tubular discharge vessel 97 is secured as a
continuation of duct 96, by a ring 97a at one end of vessel 97 d to ring 96a,
with an O-ring seal between rings 96a, 97a providing a gas-tight seal. Adjacent to the
inlet end of vessel 97 there is an inlet connector 98 connectable to a source of
pressurised protective gas, such as argon, enabling a positive pressure of the gas to
be maintained in vessel 97, with the gas discharging from an outlet pipe 99. The
length of vessel 97 and the cooling effect of the protective gas, which may be cooled
prior to being supplied to vessel 97, are such that product issuing from vessel 97 is at
a temperature enabling it to be safely force cooled such as by water spraying, or
simply air-cooled in being taken onto a spool or the like.
s 8 to 11 show a preferred form of scraper 62, used to remove flash from wheel
44 in the extruder assembly 40 of Figures 2 and 3. The scraper 62 consists of a three
piece elongate body 63 having a head portion 64 on which scraper blades 65 are
mounted. The elongate body 63 consists of two mirror symmetry flanking scrapers
63a and 63b that each have an outwardly ting head portion 64a, 64b and which
together lly enclose the elongate central scraper 63c. The whole assembly
comprising scraper 62 is able to be held in position adjacent to wheel 44, as shown in
Figure 2, by a holder (not shown). Scraper blades 65a, 65b are mounted onto head
portions 64a, 64b of the elongate body portion 63a, 63b while scraper blade 65c
is mounted onto the adjacent end of the te central scraper 63c. While shown as
comprising three components, the scrape blades 65 may comprise a single
component. The blades 65a, 65b, 65c have a flat plate form which is tapered at one
WO 19196
side to define a sharp scraper edge 66. The blades 65a, 65b, 65c are secured to a
recessed end of head portion 64 such as by screw fasteners 67 passing through
openings 68 in blade 65, into threaded holes 68a in head portion 64. Ridges 68 on
blade 65 locate in grooves 69 of head portion 64 to secure blade 65 in relation to
head portion 64.
The elongate body portion of the groove scraper 63c is positioned fonNard of the
flanking scrapers 63a, 63b by a threaded bolt (not shown) so that scraper edge 66
forms a substantially continuous line. The free end of l part 63c is rounded to
enable it to be easily received into groove 42 of wheel 44 when edge 66 is in line.
This allows the top of groove 42 to be trimmed of flash by scraper blade 65c
uous to elongate body portion of the groove scraper 63c and the wheel 44
adjacent to the groove 42 to be trimmed of flash by scraper blades 65a, 65b
contiguous to flanking scrapers 63a and 63b. Thus, the scraper 62 is able to remove
flash from wheel 44, both around the perimeter of each rim and from the side walls
and base of groove 42.
Extrusion from Rod Forms
Feed material comprising rods of non-ferrous high ature formable feed
material, such as of titanium, tantalum or niobium, can be extruded following feed
preheats of 800°C to . The rods may be of t feed material or rods
produced by cold isostatic pressing (CIP), or otherwise compacted, in each case with
or without binders, preferably without. Compaction can be to greater than 60% dense,
but less than 90% dense (preferably 75% dense) from powder feed material such as
from CP titanium powders (or blended elemental mixtures). Cold tic pressing or
pre-compaction allows for the feeding of powders or particulates of various size
distributions such as less than about 850 um and morphologies (e.g. sponge-like and
hydrogenated/dehydrogenated, H/DH in the case of titanium and tantalum powder).
Extrusion occurs when the grooved wheel was preheated to 100 to 250°C
, ably
250°C and the coining roll, die chambers and entry block gs were preheated to
300 to 450°C, ably 400°C and the abutment to 450-600°C, ably 550°C.
Modern Conform machines allow for higher wheel heating and continuous tool
preheating right to the point of extrusion, which would be advantageous. Tooling
preheating for the extrusion of copper and aluminium is used to ve the tooling,
particularly during start up; however for extrusion of non-ferrous high temperature
formable metals, preheating is essential to reduce thermal losses from the feed and
allow extrusion to occur.
The continuously extruded product is readily formable. For example, grade 3 titanium
thus extruded could be swaged at room temperatures with intermediate anneals
between swaging ions to reduce the continuously extruded wire diameter from
6 mm to 3 mm. Similarly, continuously extruded product from blended elemental
grade 5 titanium powders could be swaged at 500°C from 6 mm to 3 mm diameter
from the as extruded and as extruded and nised ions, with the latter
preferred. nisation could occur under vacuum or a neutral atmosphere, for
example argon, at 1000°C to 1200°C for 1 to 2 hours with 1200°C for 1 hour
preferred.
The typical tensile properties of the continuous extruded rods from titanium powder
feeds matched the titanium grade for grades 1 to 4 in the as extruded condition.
Higher d grades required a homogenisation anneal, after which their properties
also matched the grade. Depending on the intended ation, for example um
wire for melting such as ve manufacturing feeder wire or as fastener stock,
dictates the need for further post processing of the wire to e final
microstructures etc.
For extrusion from fully dense CP titanium feed al the preferred preheat
temperature for best t quality was 800°C. For this, and the other feed
materials, the feed material must transition from the heating zone to the Conform
tooling at a fast enough rate to remain sufficiently hot and therefore sufficiently ductile
to allow extrusion to occur. With CP titanium feed material, the tensile properties of
as-extruded product formed from fully dense feed after 800 to 1100°C preheats were
equivalent to the feed material with elongation reduced by 4% and strength slightly
elevated by 1614 MPa due to mild grain refining and slight increases in interstitial
levels (not more than 0.05 wt.% maximum).
The product from rod form feed may have a thin oxide layer on the surface (less than
50 pm in the case of a blue oxide film on titanium extrudate) but the bulk metal of the
extrusion has very similar oxygen and nitrogen levels as the feed. The microstructure
is more homogenous when processing titanium high in the alpha phase field or low in
the beta phase field than when processing higher in the beta phase field. For the
former two cases the bulk of the metal is equiaxed and grain refined (compared to
equiaxed starting material), however, a region of greater refinement occurs at the
periphery. A more homogenous microstructure is achieved when the preheat
ature of um feed material rod-form is within <i50°C along its length. Hot
defects such as metal folding and swirling were also more likely to occur when
extruding from higher in the beta phase field.
The heat generated by the extrusion process produces g temperatures typically
below 500°C in the region near the abutment, about 100 to 150°C below the preheat
temperature at the abutment face (57a, Figure 3) and up to 700°C in the die block
ion, so controlled cooling for each tooling component is required for continuous
runs. Successful extrusion of CP titanium is possible at extrusion stresses (through
the die insert) of 0.5 to 6.0 GPa, depending on the extrusion ratio. Some abrasive and
galling wear of the abutment occurs for the tion of long extrudate lengths that
may be controlled by hard facing the die insert and minimised by controlled cooling.
The abutment profile needs to match the profile of the groove to maintain an even
flash gap and prevent side wear of the abutment. The rake angle between the
abutment face and the centreline of the extrudate is appropriate at 21° but can be
reduced to 6° to better suit feed material, such as um, and reduce galling wear of
the abutment surface. A reduction in the rake angle also reduces the stress through
the abutment from about 1.2 to 1.0 GPa. The addition of hydrogen to the titanium
powder by using titanium hydride powder or enated titanium can reduce the
flow stress and further reduce extrusion and nt stress. It is necessary however
to vacuum anneal such product to remove residual hydrogen. Improved l
control of the abutment is also ed to maintain abutment ss and reduce
wear, such as through controlled water cooling after extrusion has begun. Water
cooling was found to remove 350°C of temperature from the abutment, which reduced
to 150°C of removed ature when helium gas was used as the cooling .
A wear resistant facing insert on the abutment or a thermal and wear resistant barrier
layer such as P82 is preferred to increase abutment 57 wear life for super alloy tools
such as Rene 95. A higher strength, high temperature, high thermal conductivity
alloy, such as a tungsten- based W-25Re-4HfC as the material for critical parts such
as the abutment insert 57’ are suggested to increase product volumes per tool.
Tooling wear from super alloy tools, particularly for runs of tens of metres and
inadequate tool cooling, results in contamination within the product and sites for beta
phase stabilisation for titanium.
It is possible to produce a grain refined um alpha structure by processing fully
dense coarser grained feed low in the alpha field. For CP titanium grain sizes not
more than about 3 pm are possible by preheating the leading end for at least a length
of one wheel ference and leaving the trailing end at room temperature. The hot
leading end coats the wheel and the cold end continues through the tooling to
produce a highly grain refined alpha structure.
Flashing rates increase with lower t temperatures and are also tive of
higher loads. To reduce flashing rates, the gaps through which flashing occurs
between the shoe insert tooling and wheel surfaces were reduced to 0.2 to 0.5 mm;
the latter more common due to machine tolerances.
Under typical conditions, ion of feed material cannot be stopped mid-run by
allowing the feed al to cool and harden in the wheel groove and die, then
restarted by preheated feed being fed back to the extrusion wheel. The tooling and
resident feed material metal needs to be reheated to greater than 500°C to allow
ion to be restarted, or, after a uous extrusion run, the die chambers
tooling needs to be removed, a fresh die chambers tooling placed in the machine for a
new extrusion run and the original die chambers cleaned. Material that remains in the
grooved wheel does not need to be removed as long as the tyre thickness remains
within the flash gap tolerances and necessary purity levels. This al can be
flushed through but s at the surface and into the bulk of the extrudate and can
result in an heterogeneous tructure. Such material would probably have to be
further mechanically worked, such as by repeat passing and possibly a post
mill anneal, to achieve final properties.
To generate sufficient frictional ace between the CIPed rods and the wheel
groove, the coining roll was set at a height that was sufficient to hot compact the feed
to at least 90% density within the groove. The feed material thus upset within the
groove and with an intimate frictional interface with the groove, was able to be
extruded through about 85° shear at the abutment. Ignoring strain s due to the
85° shear, the extrusion ratio from the green diameter to the extrusion product was
0.8 to 4.0. The density of the product was greater than 99%. Great l of the flash
gaps to 0.2 to 0.3 mm, controlled heat flow through the wheel 44 by reduced cooling
by using a fluid of less thermal capacity than water such as silicone oil and additional
external heating of insert die 60 to at least 400°C at start up was necessary to
achieve extrusion ratios greater than 6.4 for a single pass through the system. A
multi-strand die insert 66’ (Figures 38 and 3C) may be preferred for extrusion ratios of
16. Scaling down of the feed input, such as by reducing the ions of groove 42,
abutment 57 and shoe insert tongues 55 also allows for the production of er
gauge material.
As with the fully dense rod feed, processing the cold isostatic pressed rods high in the
beta phase field resulted in a heterogeneous and coarse microstructure. ion
high in the alpha and/or low in the beta phase fields for titanium feed material is
required for process optimisation. Product from powder feeds can benefit from a post
mill anneal to return ductility.
The heat generated near the abutment is higher when extruding from fully dense rod
than is the case for extruding from powder compacted rod feed material at equivalent
feed preheats. The required extrusion power is also greater when extruding from fully
dense feeds compared to lly dense, however fully dense feeds require less
energy to produce equivalent product s because extrusion from less dense
feeds requires greater time.
Powders compacted, such as by cold isostatic pressing, to e bars from powder
blends of CP titanium and Al-40V master alloy without binders to Ti-6Al-4V
compositions can be extruded using CP titanium as a soft matrix to produce a
composite ure of CP titanium as the majority phase and sed particles of
master alloy intermetallics. There is little diffusion between the soft matrix and
intermetallic particles in the as extruded product. The remnant master alloy particles
can be d following a beta nisation treatment at 1000 to 1200°C for 1 to
4 hours to produce a coarse grained structure for r wrought forming to narrower
gauge. The homogenisation temperature depends on the coarseness of the master
alloy particles (D50 of 64 to 25 um attempted) in the blended powder.
Extrusion from Free Flowing Powder
Non-ferrous high temperature formable powder feed to the rotary extruder may be
red via the powder feeder unit as elemental or blended elemental powder
mixtures in as-received or pelletised conditions. Heating residence time is controlled
by feeder rotation and tilt, allowing for the full range of powder morphologies to be
delivered to the extruder. Powder feed material that was fed via the powder feeder
unit to the extruder in the case of titanium powder, included -140 um
hydrogenated/dehydrogenated powder pelletised to flake, discs or cuboids (+1 mm, -
4 mm); or as raw powder (085 mm, +0.355 mm) and -140 um. Other powder
morphologies and sizes are also possible.
Powder mass and heat flows were matched to the mass output of the er.
Extrusion is possible for g powders preheated to 510 to 1000°C. At the lower
end of this preheating range the microstructure of the extrusions was ultra grain
refined with the grain size less than 3pm, in the case of CP titanium extrusions.
Preferred extrusion atures are alloy dependent, but for CP titanium, a preheat
temperature high in the alpha field is preferred (at about 800°C). At close to 600°C
titanium powders, particularly when subject to an external , have a cy to
stick or sinter together into an agglomeration. The mass flow from the powder feeder
must be regulated, therefore, to maximise powder build up to the compacting zones
under the shoe inserts by controlling the degree of flood feeding by matching the
wheel rotation speed to the powder delivery speed to the wheel and prevent
agglomeration and blockage. Agglomeration and blockage may be further reduced
and finer powders at higher temperatures successfully delivered by the application of
a tapper at the spout . Extrusion is le at wheel surface speeds of
0.02m/s to 0.32m/s, with 0.16 to 0.33 m/s preferred. Fast initial wheel speed may be
needed to form a tyre and then the speed of the wheel may be reduced to more
closely match the mass flow to the top of the wheel with the mass flow out of the die
insen.
Extrusion for CP titanium ed from free g H/DH powder of tap density
greater than 30 to 50% of tical when the ratio of powder pellet or powder D50 to
groove width was greater than 0.33 and did not occur when the ratio was less than
0.046 at 510°C.
Extrusion from ratio values of <0.046 to 0.33 is possible at higher preheats as this
results in increasing the stickiness and frictional interaction of the titanium granules
with each other and the walls of the wheel groove. Further, precompaction by the
introduction of a driven coining roll may allow ion from ratio values less than
0.046 by increasing frictional interaction between the granules and the groove wheel
surfaces as well as sing the density of the powder in the groove. Increasing the
density of low density powders (10 to 30% of theoretical) by pre-compaction or other
method such as milling or some combination is also beneficial.
Finally, it is to be understood that various alterations, modifications and/or additions
may be introduced into the constructions and arrangements of parts previously
described without departing from the spirit or ambit of the invention.
Received 24/10/2012
Claims (3)
1. A process for extruding feed materials of a high temperature formable non- ferrous metal that is susceptible to embrittlement during in air processing, using apparatus ing an extrusion system having a rotatable wheel and shoe which is positionable to enable the shoe to cover part of the length of a groove around the periphery of the wheel to form an arcuate passageway having a first, inlet end and a second end, the shoe having an abutment which substantially closes the second end of the passageway and an extrusion die spaced from the abutment by a die chamber; 10 wherein the feed material is ed from titanium, tantalum, niobium, and an alloy of any of titanium, tantalum and niobium and the process includes the steps of: pre-heating the feed material to a pre-heat temperature not less than about 390°C in a chamber defined by a feeder device, ining a protective atmosphere substantially free of oxygen and nitrogen is heated in the feeder 15 in the chamber of the feeder device while the feed material device to the pre—heat temperature, inlet end of passing the pre-heated feed material from the feeder device to the the passageway, the pre— drawing the pre-heated feed al along the passageway to cause 20 heated feed material to be forced by engagement with the abutment into the chamber and through an extrusion orifice defined by the die to provide ed product, and the extruded product is passed from the die orifice and cooled. is substantially in 25
2. The process of claim 1 wherein the pre-heat temperature excess of a ature solely due to friction and shear deformation of the feed material generated by rotation of the wheel and extrusion.
3. The process of claim 1 or claim 2, wherein the feed material is titanium or a 3O titanium alloy, and n the or alloy containing near 50 atomic percent titanium pre-heat temperature is in a range in excess of about 760°C and up to about 1140°C, such as from 800°C to 1100°C. D SHEET 1131: A /A1.171.)an Received 24/
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AU2011900864 | 2011-03-10 | ||
AU2011900864A AU2011900864A0 (en) | 2011-03-10 | Continuous ti extrusion | |
PCT/AU2012/000231 WO2012119196A1 (en) | 2011-03-10 | 2012-03-07 | Extrusion of high temperature formable non-ferrous metals |
Publications (2)
Publication Number | Publication Date |
---|---|
NZ615063A NZ615063A (en) | 2014-07-25 |
NZ615063B2 true NZ615063B2 (en) | 2014-10-29 |
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