U.S. patent application number 10/560977 was filed with the patent office on 2007-08-02 for beta-titanium alloy, method for the production of a hot-rolled product from an alloy of this type, and uses thereof.
Invention is credited to George Frommeyer, Sven Knippscheer, Oliver Schauerte, Heinz Sibum.
Application Number | 20070175552 10/560977 |
Document ID | / |
Family ID | 33521276 |
Filed Date | 2007-08-02 |
United States Patent
Application |
20070175552 |
Kind Code |
A1 |
Sibum; Heinz ; et
al. |
August 2, 2007 |
Beta-titanium alloy, method for the production of a hot-rolled
product from an alloy of this type, and uses thereof
Abstract
The invention relates to a beta titanium alloy that has high
strength and good plastic characteristics prior to curing for the
purposes of effective formability and also has high fatigue
strength. The beta titanium alloy accordingly contains (in mass %):
V: 10 to 17%, Fe: 2 to 5%, Al: 2 to 5%, Mo: 0.1 to 3%, and
optionally one or more alloy elements from the group of Sn, Si, Cr,
Nb, Zr according to the following proportions: Sn: 0.1 to 3%, Si:
0.1.ltoreq.2%, Cr: .ltoreq.2%, Nb: .ltoreq.2%, Zr: .ltoreq.2%,
wherein additional contents of C and of elements from the group of
the lanthanides may be present, and as the remainder Ti and
inevitable impurities. The invention also relates to a method by
means of which high-strength components may be produced
cost-effectively from an alloy of this type.
Inventors: |
Sibum; Heinz; (Essen,
DE) ; Schauerte; Oliver; (Lehre, DE) ;
Frommeyer; George; (Erkrath, DE) ; Knippscheer;
Sven; (Mulheim au der Ruhr, DE) |
Correspondence
Address: |
PROSKAUER ROSE LLP;PATENT DEPARTMENT
1585 BROADWAY
NEW YORK
NY
10036-8299
US
|
Family ID: |
33521276 |
Appl. No.: |
10/560977 |
Filed: |
July 2, 2004 |
PCT Filed: |
July 2, 2004 |
PCT NO: |
PCT/EP04/07201 |
371 Date: |
August 16, 2006 |
Current U.S.
Class: |
148/671 ;
420/419; 420/420 |
Current CPC
Class: |
C22C 14/00 20130101;
C22F 1/183 20130101 |
Class at
Publication: |
148/671 ;
420/419; 420/420 |
International
Class: |
C22C 14/00 20060101
C22C014/00; C22F 1/18 20060101 C22F001/18 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 3, 2003 |
DE |
103 29 899.1 |
Claims
1. Beta titanium alloy containing (in mass %): V: 10 to 17%, Fe: 2
to 5%, Al: 2 to 5%, Mo: 0.1 to 3%, and optionally one or more alloy
elements from the group of Sn, Si, Cr, Nb, Zr according to the
following proportions: Sn: 0.1 to 3%, Si: 0.1.ltoreq.2%, Cr:
.ltoreq.2%, Nb: .ltoreq.2%, Zr: .ltoreq.2%, wherein the beta
titanium alloy may additionally comprise contents of C and of
elements from the group of the lanthanides, and as the remainder Ti
and inevitable impurities.
2. Beta titanium alloy containing (in mass %): V: 10.00 to 17.00%,
Fe: 2.00 to 5.00%, Al: 2.00 to 5.00%, Mo: 0.10 to 3.00%, and
optionally one or more alloy elements from the group of Sn, Si, Cr,
Nb, Zr according to the following proportions: Sn: 0.10 to 3.00%,
Si: 0.10 to 2.00%, Cr: .ltoreq.2.00%, Nb: .ltoreq.2.00%, Zr:
.ltoreq.2.00%, and as the remainder Ti and inevitable
impurities.
3. Beta titanium alloy according to any one of the preceding
claims, containing 12 to 17 mass % V.
4. Beta titanium alloy according to any one of the preceding
claims, containing 0.5 to 3 mass % Mo.
5. Beta titanium alloy according to any one of the preceding
claims, containing 0.5 to 3 mass % Sn.
6. Beta titanium alloy according to any one of the preceding
claims, characterised in that at ambient temperature it has a yield
point Rp.sub.0.2 of at least 1,400 MPa.
7. Beta titanium alloy according to any one of the preceding
claims, characterised in that at ambient temperature it has a
tensile strength R.sub.m of at least 1,500 MPa.
8. Beta titanium alloy according to any one of the preceding
claims, characterised in that at ambient temperature it has a
plastic strain .epsilon..sub.p0.2 of more than 4%.
9. Beta titanium alloy according to any one of the preceding
claims, characterised in that its density .rho. does not exceed 4.8
g/cm.sup.3.
10. Method for manufacturing a product produced from a beta
titanium alloy, comprising the following steps: melting a beta
titanium melt having the composition according to any one of claims
1 to 9 to form a preliminary product in block form, hot-forming the
preliminary product, hot end forming the hot-formed preliminary
product to form a hot end product, solution annealing the hot end
product, cold-forming the hot end product to form an end product,
curing treatment of the end product.
11. Method according to claim 10, characterised in that the hot end
forming process is carried out as a hot-rolling process.
12. Method according to claim 11, characterised in that the
hot-rolling process is followed by a coiling process.
13. Method according to claims 10 to 12, characterised in that the
alloy elements V, Fe and Al are added by alloying in the form of a
master alloy.
14. Method according to any one of claims 10 to 13, characterised
in that the preliminary products are rounded blocks, which are
hot-formed during the hot-forming process to form billets or mill
bars.
15. Method according to any one of claims 10 to 14, characterised
in that the hot end product is a wire or a metal sheet.
16. Method according to any one of claims 11 to 15, characterised
in that the hot end product is solution annealed after the coiling
process.
17. Method according to claim 16, characterised in that the
solution annealed hot end product is cold-formed.
18. Semi-finished product produced from a beta titanium alloy
having the composition according to any one of claims 1 to 9.
19. Use of a beta titanium alloy having the composition according
to any one of claims 1 to 9 for the production of components that
are used in the temperature range from -196.degree. C. to
300.degree. C.
20. Use of a beta titanium alloy having the composition according
to any one of claims 1 to 9 for the production of vehicle
components.
21. Use of a beta titanium alloy having the composition according
to any one of claims 1 to 9 for the production of components used
in plant or apparatus engineering.
22. Use of a beta titanium alloy having the composition according
to any one of claims 1 to 9 for the production of sports equipment.
Description
[0001] Beta titanium alloys with high vanadium contents are
distinguished by high strength and also effective toughness or
ductility. They are conventionally processed in a hot-forming
process to form semi-finished products such as metal sheets, rods,
hollow or solid profile members, and wires, from which
high-quality, light-weight components are then produced.
[0002] The basic principles of the production and characteristics
of beta titanium alloys are described in U. Zwicker, Titan-und
Titanlegierungen ("Titanium and Titanium Alloys"), Springer:
Berlin, Heidelberg, N.Y. (1974). In addition to titanium as the
matrix metal, beta titanium alloys therefore conventionally
contain, as principal alloys elements stabilising the .beta. mixed
crystal, V, Nb, Ta, Mo, Fe and Cr, as well as certain contents of
Zr, Sn, Al and additives of Si.
[0003] A beta titanium alloy and a method for the production of
components from this alloy are also known from DD 281 422 A5. In
the known alloy, the contents of Cr and V are in total 1.5 to 4.5
mass %, while the content of Cr is limited to less than 2.5 mass %.
In addition, the known alloy contains less than 2.0 mass % Fe, 3.8
to 4.8 mass % Al, 1.5 to 4.5 mass % Mo, as well as 1.5 to 2.5 mass
% Sn, 2.8 to 4.8 mass % Zr and less than 0.3 mass % Si. According
to the known method, a melt having a composition of this type is
cast to form bars, which are then hot-formed, in a process carried
out in two stages, to form a component. The component that is
obtained is brought into solid solution by means of a heat
treatment process, in which its temperature is maintained at
10.degree. C. to 40.degree. C. below a value designated in DD 281
422 A5 as the ".beta. transus" real value. After this heat
treatment process, the part is then kept between 550.degree. C. and
650.degree. C. for 4 to 12 hours. The parts treated in this manner
have a yield point R.sub.p0.2 of at least 1,100 MPa and tensile
strength R.sub.m of at least 1,200 MPa.
[0004] Further examples of beta titanium alloys are provided in
AT-PS 272 677, EP 0 408 313 B1 and EP 0 600 579 B1. Common to the
prior art documented in all of these documents is the endeavour to
provide a titanium alloy that may be cast as easily as possible,
while at the same time having good mechanical characteristics and
being able to be produced cost-effectively.
[0005] However, practical experience has shown that the known
alloys, both with respect to their strength and with respect to
their expansion behaviour, do not satisfactorily meet the
requirements set by the processors and users.
[0006] The object of the invention was therefore to provide a
high-strength beta titanium alloy that has good plastic
characteristics prior to curing, for the purposes of effective
formability, and high fatigue strength after curing and may be
produced cost-effectively. A method by means of which high-strength
components may be produced cost-effectively from an alloy of this
type is also to be indicated.
[0007] With respect to the material, this object is achieved by a
beta titanium alloy that contains (in mass %): V: 10 to 17%, Fe: 2
to 5%, Al: 2 to 5%, Mo: 0.1 to 3%, and optionally one or more alloy
elements from the group of Sn, Si, Cr, Nb, Zr according to the
following proportions: Sn: 0.1 to 3%, Si: 0.1.ltoreq.2%, Cr:
.ltoreq.2%, Nb: .ltoreq.2%, Zr: .ltoreq.2%, wherein the beta
titanium alloy may additionally comprise contents of C and of
elements from the group of the lanthanides, and as the remainder Ti
and inevitable impurities.
[0008] At ambient temperature, a beta titanium alloy having the
composition according to the invention easily achieves a yield
point R.sub.p0.2 of at least 1,400 MPa, a tensile strength R.sub.m
of at least 1,500 MPa, and a plastic strain E.sub.p0.2 of more than
4%. Its density .rho. does not exceed 4.8 g/cm.sup.3, so components
that are not only extremely strong, but also weight-optimised, may
be produced using a beta titanium alloy according to the
invention.
[0009] This is achieved, firstly, in that the alloy according to
the invention comprises significantly higher vanadium contents than
those provided in beta titanium alloys in the prior art. As a
result of the high V contents, the .beta. phase of the structure is
stabilised and the high-temperature strength increased. In an alloy
according to the invention, the V content is therefore preferably
in the range from 12 to 17 mass %, in particular in the range from
13 to 17 mass %.
[0010] Contents of 2 to 5 mass % aluminium stabilise the a phase of
the structure and cause effective mixed crystal hardening.
[0011] The effect of the iron in the titanium alloy having the
composition according to the invention consists in a stabilisation
of the .beta. phase of the structure, an increase in the
high-temperature strength and an improvement in the mixed crystal
formation.
[0012] Molybdenum in contents of 0.1 to 3 mass %, preferably at
least 0.5 mass %, is contained in a titanium material according to
the invention to stabilise the .beta. phase of the structure and to
increase the high-temperature strength.
[0013] A beta titanium alloy according to the invention optionally
also contains one or more alloy elements from the group of Sn, Si,
Cr, Nb, Zr.
[0014] The presence of tin has a beneficial effect on the mixed
crystal hardening and the high-temperature strength. The Sn
contents are therefore preferably in the range from 0.5 to 3 mass
%.
[0015] In an alloy according to the invention, silicon increases
the high-temperature strength and the oxidation resistance.
[0016] Chromium may be added to the alloy to stabilise the .beta.
phase of the structure and to increase the high-temperature
strength.
[0017] Adding niobium may also have a beneficial effect on the
high-temperature strength and the oxidation resistance of the
alloy.
[0018] Finally, it may also be advantageous, for improving the
mixed crystal formation and the oxidation resistance, to add
zirconium to the alloy according to the invention.
[0019] In addition to the components of which the effect has been
described in detail above, the alloy according to the invention may
contain further components, provided that they do not negatively
affect the characteristics achieved according to the invention.
These include, in particular, contents of carbon and contents of
elements associated with the group of the lanthanides.
[0020] Optimal characteristics of the beta titanium alloys
according to the invention are achieved if the above-specified
limit values are observed to within at least two decimal
places.
[0021] With respect to the method, the above-specified object is
achieved in that the manufacturing of a product produced from a
beta titanium alloy involves the following steps: [0022] melting a
beta titanium melt having the composition according to the
invention to form a preliminary product in block form, [0023]
hot-forming the preliminary product, [0024] hot end forming the
hot-formed preliminary product to form a hot end product, [0025]
solution annealing the hot end product, [0026] cold-forming the hot
end product to form an end product, [0027] curing treatment of the
end product.
[0028] The hot end forming process for the production of strips or
metal sheets may be carried out as a hot-rolling process, which
may, if necessary, be followed by a coiling process.
[0029] The Ti alloy according to the invention may be produced in a
particularly cost-effective manner in that the alloy elements V, Fe
and Al are added by alloying, in a manner known per se, not
individually, but rather in the form of a master alloy. Master
alloys of this type are commercially available.
[0030] The hot end product obtained by means of the method
according to the invention after the hot-forming process consists
of a single-phase, metastable beta titanium, the transus
temperature T.sub.B of which is approximately 788.degree. C. If the
hot end product is produced by means of a hot-rolling process, it
comprises crystals stretched in the rolling direction and possesses
a partially dynamically re-crystallised structure.
[0031] The preliminary product in block form, which is processed
during the method according to the invention, is obtained by means
of re-melting. A Vacuum Arc Re-melt furnace may, in a manner known
per se, be used for this purpose.
[0032] The preliminary products may, for example, be rounded
blocks, which are hot-formed during the hot-forming process to form
billets or mill bars. Billets of this type are typically square
with edge lengths of, for example, 70 mm or round with a diameter
of, for example, 60 mm.
[0033] The hot end forming process is typically carried out at
forming temperatures in the range from 950.degree. C. to
1,150.degree. C., in order to achieve an effective reduction of
cross-sectional area and a homogenisation of the composition and
the structure.
[0034] If the hot end forming process is carried out as a
hot-rolling process, an advantageous configuration of the method
according to the invention provides that the hot end product is
solution annealed after the hot end forming process. The solution
annealing process is followed by the cold-forming process. The
solution annealing process typically takes place for 30 minutes at
875.degree. C.
[0035] To further increase the values of the mechanical
characteristics, the hot end product, which may be solution
annealed, is annealed in a re-crystallising manner. For holding
times of 20 to 40 minutes, the temperatures during this annealing
treatment are typically in the range from 775.degree. C. to
875.degree. C.
[0036] Cold-forming, for example by means of cold-rolling, then
takes place. The end product obtained after the cold-forming
process has a yield point R.sub.p0.2 of at least 870 MPa to 900
MPa, a tensile strength R.sub.m of 890 MPa to 944 MPa, and a
plastic strain of 14 to 17%.
[0037] After the rolled product, which has been annealed in a
re-crystallising manner, is then subjected to a curing treatment,
the product that is obtained has a yield point R.sub.p0.2 of at
least 1,400 MPa, a yield strength R.sub.m of at least 1,500 MPa,
and elongation .epsilon..sub.p1 of at least 4%. For a treatment
period of typically 5 hours, the typical temperature of the curing
treatment is approximately 480.degree. C. Provided that these time
and temperature requirements are adhered to, an optimal
characteristic spectrum of the end products produced according to
the invention is achieved.
[0038] Semi-finished products such as mill bars, metal sheets,
rods, profile members or wires, which, owing to their
characteristic profile, are ideal as high-strength components, may
be produced from a beta titanium alloy having the composition
according to the invention. The semi-finished products may, in
particular, be produced cost-effectively by using the method
according to the invention.
[0039] Beta titanium alloys according to the invention have proven
particularly suitable as constructional materials for the
production of components used in rail or road vehicles and in air
and space travel. Examples of components for this use include axle
springs, connecting rods, piston pins, high-strength screws, brake
pistons and brake discs.
[0040] Beta titanium alloys according to the invention are also
particularly suitable, owing to their specific characteristics, for
the production of components used in the fields of general
mechanical engineering, apparatus engineering, plant engineering,
container construction, cryogenics, vehicle construction, or in the
field of sport.
[0041] It has been found that beta titanium alloys having the
composition according to the invention are particularly suitable
for the production of components that are used in the temperature
range from -196.degree. C. to 300.degree. C.
[0042] The invention will be described below in greater detail with
reference to an embodiment.
[0043] Rounded blocks containing (specified in mass %) 15% V, 4%
Fe, 3% Al, 1% Mo, 1% Sn and 0.3% Si, the remainder being Ti and
inevitable impurities, which were then hot-formed, in a forging
process, to form square billets, were melted in a VAR furnace.
During alloying of the melt, the alloy components V, Fe and Al were
jointly added, in the form of an inexpensive master alloy, to the
matrix material Ti.
[0044] After the forging process, the billets were hot-rolled, at
hot-rolling temperatures in the range from 1,100.degree. C. to
950.degree. C., to form wire and were then wound to form coils.
After the hot-rolling process, the wire comprised single-phase,
metastable .beta. titanium (transus temperature T.sub..beta. of
approximately 788.degree. C.) with crystallites stretched in the
direction of the wire axis and a partially dynamically
re-crystallised structure.
[0045] Following the coiling process, the wire was solution
annealed for 30 minutes at 875.degree. C. Following the solution
annealing process, the wire was cold-formed. After the cold-forming
process, the wire was annealed in a re-crystallising manner at
temperatures between 775.degree. C. and 875.degree. C. for a
holding period in the range from 20 minutes to 40 minutes. The wire
annealed in this manner had a yield point R.sub.p0.2 between 870
MPa and 900 MPa, a tensile strength R.sub.m between 890 MPa and 944
MPa, and elongation A between 14% and 17%. The re-crystallisation
annealing process was followed by a curing treatment, in which the
wire was maintained for 5 hours at 480.degree. C.
[0046] At ambient temperature, the wire thus finished had a yield
point R.sub.p0.2 of more than 1,400 MPa, a tensile strength R.sub.m
of more than 1,500 MPa, and elongation A at least in the range from
4% to 5%.
* * * * *