CA2206310A1 - Machining of a memory metal - Google Patents

Machining of a memory metal

Info

Publication number
CA2206310A1
CA2206310A1 CA002206310A CA2206310A CA2206310A1 CA 2206310 A1 CA2206310 A1 CA 2206310A1 CA 002206310 A CA002206310 A CA 002206310A CA 2206310 A CA2206310 A CA 2206310A CA 2206310 A1 CA2206310 A1 CA 2206310A1
Authority
CA
Canada
Prior art keywords
blank
memory metal
tube
core
casing
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
CA002206310A
Other languages
French (fr)
Inventor
Tomas Thorvaldsson
Ola Forssell
Johan Frodigh
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Sandvik AB
Original Assignee
Individual
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Individual filed Critical Individual
Publication of CA2206310A1 publication Critical patent/CA2206310A1/en
Abandoned legal-status Critical Current

Links

Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B21MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21CMANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
    • B21C23/00Extruding metal; Impact extrusion
    • B21C23/22Making metal-coated products; Making products from two or more metals
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B21MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21CMANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
    • B21C23/00Extruding metal; Impact extrusion
    • B21C23/02Making uncoated products
    • B21C23/04Making uncoated products by direct extrusion
    • B21C23/08Making wire, bars, tubes
    • B21C23/085Making tubes
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B21MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21CMANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
    • B21C33/00Feeding extrusion presses with metal to be extruded ; Loading the dummy block
    • B21C33/002Encapsulated billet
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B21MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21CMANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
    • B21C33/00Feeding extrusion presses with metal to be extruded ; Loading the dummy block
    • B21C33/004Composite billet

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Extrusion Of Metal (AREA)
  • Metal Extraction Processes (AREA)
  • Electrical Discharge Machining, Electrochemical Machining, And Combined Machining (AREA)
  • Forging (AREA)
  • Weting (AREA)
  • Magnetic Heads (AREA)
  • Materials For Medical Uses (AREA)
  • Powder Metallurgy (AREA)
  • Manufacture And Refinement Of Metals (AREA)

Abstract

A NiTi-based tube of memory metal is produced by extrusion, whereby: a) one starts off from a blank of a memory metal; b) a central hole is drilled in said blank; c) a core is introduced into the central hole, whereafter the blank is encased by a casing, and preferably also by two gables, whereby the blank is excluded from the surrounding atmosphere; d) the encased blank is heated and extruded; e) the ends of the extruded blank are removed; and f) also the core and the surrounding casing is removed. In this way, it has been accomplished to produce NiTi-based tubes of memory metal of hitherto unattained length, such as >= 1/2 m.

Description

CA 02206310 1997-0~-28 WO 96/17698 = PCT/SE95/01463 ' Machinin~ of a Memor~T Metal t The present invention relates to a process for the extrusion of tubes of a 5 memory metal, in particular a memory metal of the type NiTi and a tube produced according to this process.
So called memory metals relate to a group of materials which are characterized by their deviating thermo-mechanical properties. To these belong inter alia NiTi-based alloys and copper alloys of so called ~-brass. The compositions~ properties 10 and applications of the memory metals are known by a number of publications in this area (see, e.g.~ Walter S. Owen: Shape memory effects and applications. an overviev~.
Shape memory effects in alloys, edited by Jeff Perkins, 1975, Plenum Press New ~ork;
Process of Int. Symposium on shape memory effects and applications, Toronto~ Canada, 19. - 22.5.1975). The memory metals are characterized in that their phase transformation 15 (transition from a martensitic to an austenitic state and vice versa) takes place within a very limited temperature range in the order of magnitude 30~C.
The reason for extrusion of memory metal being desirable is that these materials are difficult to machine by cutting tools. because of rapid wear of the tool and slow production. Thus~ it would be very advantageous to be able to produce these tubes 20 by e~trusion instead of cutting m~rhinin~, e.g. when producing couplings and bit rings.
However. a heat treatment~ such as an extrusion~ of a memory metal of NiTi-type is very difficult. since this material has a high affinity for oxygen at hi~h temperatures. which leads to a strong oxidation and wasted material.
Thus, a primary object of the present invention is to provide a process that 25 makes possible an extrusion of memory metal in general and of NiTi-based memorv metal in particular.
A second object ofthe present invention is to provide an extruded tube of memorv metal in ~eneral and of NiTi-based memory metals in particular.
For illustrative but non-limiting purposes~ the invention will now be 30 described in more detail with reference to the appended figure which schematically shows the production of a tube accordin~ to the present invention.

CA 02206310 1997-0~-28 The used memory metal according to the exemplified embodiment consists of a NiTi-based alloy with an addition of niobium. The amounts can suitably vary from 35 to 60 % by weight Ni, 35 to 60 % b.w. Ti and 1 to 30 % b.w. Nb, preferably from 40 to 60 % b.w. of Ni and Ti, respectively and 1 to 20 % b.w. of Nb. In the concrete example, the concentrations of both Ni and Ti were 45 ~- 2 % b.w. and Nb was 10 + 4 %
b.w., plus naturally occurring hll~uliLies.
In accordance with the invented process, one starts off from a solid bar 1 of memory metal, see step a). Through and concentrically with this bar. a hole 2 is drilled in a conventional manner, which hole thus should be centered around the central axis of the bar, in accordance with step b). If the bar 1 is not perfectly round or is uneven and/or rough on the outer surface, then a turning operation should be effected in order to attain sufficiently good surface smoothness and cylindricity. This is suitable in order to later attain a good fit in the cap S; cf. lln~lerne~th In this case, the turning should be perforrned after the central drilling.
After the central drilling, possible turning and degreasing, e.g. by a suitable alcaline solution~ the pre-prepared blank 3 is capped in, primarily for the exclusion of the oxygen of the air; see step c). However~ before this encasing takes place~ a core 4 of suitable fit and of the same length as the blank 3 is suitably introduced into the hole 2 .
Preferably~ there is a gap between the blank and the core for the introduction of a suitable release agent~ such as talcum or a talcum-cont~ining mixture. Such a core 4 is used instead of an internal mandrel at the extrusion~ since the encasing prevents the use of such a mandrel. Further~ a sleeve or cap S of equally good fit is threaded over the envelope surface of the blank 3~ which cap has the same length as the blank 3. After this.
two gable pieces 6 and 7 are welded to and around the end surfaces of the casing 5. The front gable 7~ as seen in the direction of extrusion~ is suitably rounded off around the edge. which is beneficial for the extrusion.
The materials used for the the core 4. the casing 5 and the gables 6, 7~
respectively. can of course vary within broad limits~ but at the tests the following alloys were used. % bv weight being meant:

CA 02206310 1997-0~-28 Wo 96117698 PCT/SE95/01463 Table 1 Steel C Si Mn Cr Ni Casing+gables SS21720,20 0,30 1,5 <0,3 Core 15M13~2* 0.75 - 13 -* De.~ign~tion of Sandvik; also called Hadfield steel In order to become extrudable, the ready blank or block 8 consisting of the blank 3, the core 4, the casing 5 and the gables 6, 7, were heated to about 1 040~C and lubricated with glass on the outside. However, the extrusion temperature may vary. to a large extent depending upon the memory metal alloy, and may suitably lie between 900 and 1150~C, preferably between 1000 and 1050~C.
After this, the thus pre-prepared extrusion block was extruded according to step d). The dimension of the ready tube may vary within wide limits~ depending upon the dimensions of the blank, the casing, the core and to which dimension one extrudes.
For instance. if a thick-walled casing is used, then a ready-extruded tube of a smaller diameter is obtained. Further. a thicker core gives a more thin-walled tube. If one extrudes to a small diameter, of course a lon~er tube is obtained than if one extrudes to a large diameter.
After extrusion, the ends are cut according to step e). Generally it mav be said that a typical extension factor before and after extrusion (i.ealso after cutting) is from 7 to 18 times, preferably from 10 to l S times.
After cutting. cooling and straightening (e.g.! by press or roller straightening). the casing 5 is removed. which can be effected in different ways. Usually.
the surface of the tube 3' has to be turned clean to become sufficiently smooth. which involves that the casing 5 can be turned away in the sarne working operation. The casing can also be picL;led awav in a suitable pickling bath.

CA 022063l0 l997-0~-28 The core 4' may also be removed in different ways. When producing long tubes, for in~t~nce up to 10 m, the core is removed by extending it by between 10 and 30 %, preferably by about 20 %. Then the diameter of the core llimini.~hes uniformly along its whole length and may then easily be removed, whereby a ready tube 3' remains ? see 5 step f). In order to extend the core, a piece of the tube has to be turned away at each end, in order to grip the part of the core that protrudes by said tl-ming, in a traction m~chine At shorter tube pieces the core may be drilled out instead of being extended.

Example A memory metal accoding to the above composition is prepared to a read~
extrusion block according to steps a-b-c. the block having the following dimensions:
Blank diameter: 71 rnm Blank diameter including casing: 77 mm Core (in "Hadfield steel"): 31 mm Length of blank and casing: 350 mm The block was extruded at 1040~C at a pressing force of 868 Mpa (8850 kp/cm~) and with a pressing speed of 135 mm/s. Thereby. an extruded block with casing with a diameter of 19.1 mm was obtained, the ready tube having a diameter of 172 mm.
The wall thickness of the ready tube was about 4,6 mm and its length was about 4500 20 mm.
The dimension ranges that are possible depend of course on the magnitude of the extrusion press that is used. In the example above, a press with a maximal pressing force of about 1300 Mpa (13 300 kp/cm2) is used. and a maximal starting diameter of 77 mm. Thus. this means that the blank including the casing shall have a diameter that does 25 not exceed 77 mm. On these conditions. the dimension range of the ready tube is from l () to 47 mm. Said minimum diameter implies a tube length of about 20~6 m. while said maximum diameter results in a tube length of about 0.94 m, all under the above mentioned test parameters. Shorter and longer blanks than the above mentioned ones are of course also feasible. for instance down to 200 mm and up to 400 mm. The wall 30 thickness can be ~ aried by optional dimensioning of the core and may suitablv lie between 2 and 15 rnm.
-CA 02206310 1997-0~-28 WO 96/17698 PCTISE95/01~63 If a larger press is used, then the ~limen~ion range can be increased upwards to larger diameters of the finished tube. Thus, with a suitable press. tube diameters of up to about 100 mm may be reached.
The extrusion of the thus ~nc~ce~l NiTi-based memory metal showed S surprisingly good results. Thus, it turned out to be fully feasible to produce tubes from bar material~ which tubes then may be m~(~.hinP~l further to the desired product. This involves inter alia that the necessity of the hitherto required cutting m~hiningdimini.~hes dramatically, or even is entirely elimin~te-l, which brings considerable savings in time and costs. Memory metal of NiTi-type is difficult to machine by cutting?
since it has a large wear resistance. Further. it was observed that the memory metal with gables, casing and core was verv easy to extrude.
The fact that one needs to drill a hole into the bar I is not a major disadvantage, having regard to the fact that, according to the working example, the bar extends only about 30 cm, in comparison with a number of meters after extrusion. In this context it should be underlined that such long tubes of memory metal (e.g., 2 1/2 m) are very difficult to produce by cutting machining due to insufficient centering accuracy when drilling.
Some studies in light microscopy were made of the microstructure of the memory metal before and after extrusion. From these it is inter alia clear that a more homogenous structure was obtained in the extruded tube, with more evenly distributed niobium particles. This evenerdistribution is surprising per se. The function of the niobium particles is to increase the temperature at which the memory metal automaticall~
reestablishes its original shape~ since said particles counteract the reestablishment of the original shape of the metal.
A measurement in a bar before extrusion and in a tube after finished extrusion gave the following results with reference to niobium particles:

Bar: Average length: 79 ~lm Average width: 1,5 llm Tube: Average length: 6~9 ~m Average width: 1,4 ~m W O 96/17698 PCT/SE9~/01463 These measurements show that the average length of the niobium particles is stronly :reduced at extrusion. No extruded tube had an average length for niobium particles of more than 15 ~lm.
A comparative test was also made with an identical blank, which however had not been encased but had only been provided with a core 4. An entirely inferior product was obtained, with a number of cracks. This is supposed to depend on the strong oxidation that is caused by the free access of air.
-

Claims (8)

Claims
1. Process for the production of tubes of memory metal, characterized in that a) one starts off from a blank of a memory metal, b) a central hole is drilled in said blank, c) a core is introduced into the central hole, whereafter the blank is encased by a casing, and preferably also by two gables, whereby the blank is excluded from the surrounding atmosphere, d) the encased blank is heated and extruded, e) the ends of the extruded blank are removed, and f) also the core and the surrounding casing is removed.
2. Process according to claim 1, characterized in that the starting blank is cylindrical.
3. Process according to claim 1 or 2, characterized in that the memory metal is NiTi-based.
4. Process according to claim 3, characterized in that the memory metal comprises 35 to 60 % by weight of nickel, 35 to 60 % by weight of titanium and 1 to 30 % by weight of niobium.
5. Tube-shaped product consisting mainly of NiTi-shaped memory metal, characterized in that it is produced by extrusion.
6. Tube-shaped product according to claim 5, characterized in that it contains 35 to 60 % by weight of nickel, 35 to 60 % by weight of titanium and 1 to 30 %
by weight of niobium.
7. Tube-shaped product according to claim 6, characterized in that the average length of the niobium particles is ~ 15 µm.
8. Tube-shaped product according to claim 6 or 7, characterized in that its length exceeds 1/2 m.
CA002206310A 1994-12-07 1995-12-05 Machining of a memory metal Abandoned CA2206310A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE9404243A SE505247C2 (en) 1994-12-07 1994-12-07 Process for manufacturing memory metal tubes
SE9404243-9 1994-12-07

Publications (1)

Publication Number Publication Date
CA2206310A1 true CA2206310A1 (en) 1996-06-13

Family

ID=20396247

Family Applications (1)

Application Number Title Priority Date Filing Date
CA002206310A Abandoned CA2206310A1 (en) 1994-12-07 1995-12-05 Machining of a memory metal

Country Status (9)

Country Link
EP (1) EP0805724B1 (en)
JP (1) JPH10505007A (en)
AT (1) ATE213671T1 (en)
CA (1) CA2206310A1 (en)
DE (1) DE69525658T2 (en)
ES (1) ES2173211T3 (en)
FI (1) FI112609B (en)
SE (1) SE505247C2 (en)
WO (1) WO1996017698A1 (en)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1999022886A1 (en) * 1997-10-31 1999-05-14 G. Rau Gmbh & Co. Method for producing hollow nickel titanium profiles
JP3557092B2 (en) * 1998-04-16 2004-08-25 古河電気工業株式会社 Method for manufacturing NiTi alloy pipe
CN100337764C (en) * 2005-04-27 2007-09-19 中国科学院金属研究所 High speed-ratio hot pressing method for NiTi alloy piping billet and its special mould
JP5123740B2 (en) * 2008-05-26 2013-01-23 新日鐵住金株式会社 Manufacturing method of rail joint plate for connection between no play

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1014063B (en) * 1952-10-01 1957-08-22 Comptoir Ind Etirage Hot pressing process for the production of multilayer metal rods or pipes
SE441336B (en) * 1978-10-26 1985-09-30 Nyby Uddeholm Ab Capsule for the cylindrical presses for extrusion

Also Published As

Publication number Publication date
FI972393A0 (en) 1997-06-05
SE505247C2 (en) 1997-07-21
FI972393A (en) 1997-06-05
SE9404243L (en) 1996-06-08
DE69525658D1 (en) 2002-04-04
EP0805724B1 (en) 2002-02-27
DE69525658T2 (en) 2002-11-28
ES2173211T3 (en) 2002-10-16
SE9404243D0 (en) 1994-12-07
FI112609B (en) 2003-12-31
JPH10505007A (en) 1998-05-19
EP0805724A2 (en) 1997-11-12
WO1996017698A1 (en) 1996-06-13
ATE213671T1 (en) 2002-03-15

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Legal Events

Date Code Title Description
FZDE Discontinued