EP2533917A1

EP2533917A1 - Modular extrusion die

Info

Publication number: EP2533917A1
Application number: EP11742530A
Authority: EP
Inventors: Marco Pasqualon; Morten BRÅTEN; Richard Farral Dickson
Original assignee: Norsk Hydro ASA
Current assignee: Hydro Extruded Solutions AS
Priority date: 2010-02-12
Filing date: 2011-02-09
Publication date: 2012-12-19
Also published as: WO2011099868A1; CA2788660C; US20130047692A1; WO2011099868A8; KR20120135214A; CA2788660A1; CN102712021A; JP2013519527A

Abstract

Extrusion tool or die for the extrusion of metallic material, in particular a material of aluminium or alloys thereof, or other non-ferrous metals such as Cu and alloys thereof. The die is a modular type comprising die plate/s (2, 3) with cavitie/s (4, 5) provided with insert/s (6, 7). The area of the die with strong thermo-mechanical solicitation comprising the die plate/s (2, 3), is made of a nickel, iron or cobalt-based super alloy, whereas the die in the area with strong tribological solicitation comprising the insert/s, i.e. the mandrel (6) and/or the bearing (7) of the die, is manufactured of a wear resistant material which may be a high speed tool steel, a precipitation hardened steel or a high alloy hot-worked steel, or any of suitable steel types provided with a coating such as nano particle or CVD.

Description

Modular extrusion die

The present invention relates to an extrusion tool or die for the extrusion of metallic material, in particular a material of aluminium or alloys thereof, or other non-ferrous metals such as Cu and alloys thereof.

Extrusion is a process used to create solid or hollow objects of a fixed cross sectional profile. The material is pushed through the die of the desired cross section. The two main advantages of the extrusion process over other manufacturing processes is its ability to create very complex cross-sections and finished parts with an excellent surface finish. The dies are, depending of course on the material being extruded and temperature etc., subjected to wear and numerous attempts have been made to improve the life time of extrusion dies for example by selecting suitable die materials, heat treatment and/or coating of the die with different types of coating such as CVD or nano particle type coatings.

From US-04169366 is known an extrusion device for the extrusion of hollow or semi- hollow sections of metal, in particular aluminium. The device has at least one mandrel support projecting into the die opening where the mandrel head is a special insert type which is held in place on a mandrel support by a connecting device.

US-04773251 is related to a 2 part die, whereof one part includes the bearing and the other being the support. The specificity of this solution appears to be that the two die parts are atomically bonded using powder metallurgy technology. Further, the "support" part (the one that does not carry the bearing) is relatively vaguely defined in terms of material selection as a "tough non-ductile heat resistant steel of a composition different from the metallic material of the bearing holding part".

JP-06315716 further relates to an extrusion die with a tool comprising a material made of a Ni base alloy and having hardness after heat treatment of more than HRC 33. The purpose of using such alloy is to prevent the penetration of Zn into the tool, i.e.

preventing Zinc embrittlement.

Still further CN-201287153 shows an aluminium profile extrusion die where the die tools, i.e. the parts forming the extrusion profile opening are replaceable and are made from a wear resistant material.

With the present invention is provided an extrusion die where the lifetime is quite considerably extended and where the cost of replacement and maintenance accordingly is reduced. Tests performed in several aluminium extrusion plants of the applicant shows that the selection of Ni-base super alloys as die material according to the invention reduces sever cracking and improves the die lifetime from one/two hundred extruded billets to thousand and more extruded billets before replacement of die parts or maintenance is needed.

The invention is characterized by the features as defined in the enclosed independent claim 1.

Advantageous embodiments of the invention are further defined in the dependent claims 2 - 7

The invention will be further described in the following by way of example and with reference to the drawings, where:

Fig. 1 shows an example of an extrusion die according to the invention, a) assembled in cross section, b) the same in expanded view, Fig. 2 shows in larger scale a cross section part of one of the die cavities shown in Fig.1 a). Fig. 3 Shows a Manson-Coffin diagram depicting the linear relationship, on a log- log plot, of plastic strain range versus cycles to failure of the most common tool steels, employed for extrusion dies, with the fatigue properties of a superalloy according to the invention. As stated above, extrusion is a process used to create solid or hollow objects of a fixed cross sectional profile. The attached figures show an example of an extrusion tool or die 1 for extruding hollow profiles which will be further explained in the following. The extrusion die 1 as shown in Fig. 1 a) and b) includes one bridge die body 2 and one plate die body 3, each provided with two cavities 4, respectively 5 and each cavity further defining openings with inserts 6, 7. The die as shown in Fig. 1 represents what is defined as being a two cavity die capable of extruding two profiles in parallel at the same time. Extrusion dies may however be of one or three or more cavity type depending on the type, shape (design) and size of the die opening forming the extruded product as well as the capacity of the extrusion equipment (ram and block - not shown in the figures).

Fig. 2 shows in larger scale and in cross section one of the die cavities 4, 5 shown in Fig.1 a). The two die bodies 2, 3 are, in an assembled condition whereby a mandrel part 10 on the bridge die body 2 partly protrudes into the opening of the cavity 5 in the die plate 3 such that an opening 11 is formed between the mandrel and cavity opening 5 in the die 3. The material being extruded is pressed through this opening 1 1 thereby forming the shape of the final, extruded hollow product.

With the present invention the mandrel 10 is made of a separate mandrel insert 6 attached to the bridge die body 2 by means of a screw 8.

On the other hand, according to the invention, the opening in the die plate 3 is made of a separate bearing insert 7, as well being attached to the die plate 3 by means of second screws 9. In stead of being connected by means of screws 9, the bearing insert 7 may as an alternative be thermally shrunk fit into a recess in the die plate 3 opening 5.

The fundamental idea of the present invention is the selection of different materials and the combined utilization of these in the appropriate zones of the extrusion die, fitting with the thermo-mechanical solicitations on one side and the tribological solicitations on the other side.

In the area of strong thermo-mechanical solicitation (Creep - Low Cycle Fatigue regime), the first "modulus" of the die which includes the bridge body 2 and/or die plate body 3 depending as stated above on whether it is a hollow or solid profile, is made of a

Superalloy . In particular the Superalloys are based either on a) Nickel, b) Cobalt or c) Iron. The Nickel, Cobalt and Iron based Superalloys ranges may respectively be defined as follows: Nickel based superalloys: Ni (min 39 % max 78 %), Fe (min 0% max 36%), Cr (min 12% max 25%), Al (min 0% max 5%), Co (min 0% max 20%), Mo (min 0% max 10%), Nb (min 0% max 5%)

Cobalt based superalloys: Co (min 34% max 50%), Ni (min 10 % max 29 %), Fe (min 3% max 26%), Cr (min 3% max 22%), Al (min 0% max 6%), Nb (min 0% max 3%), W (min (0% max 15%)

Iron based superalloys : Fe (min 42% max 74%), Ni (min 0 % max 38 %), Cr (min 0% max 20%), Al (min 0% max 5%), Co (min 0% max 15%), Mo (min 0% max 5%), Nb (min 0% max 5%)

Above defined Superalloys, or high-performance alloy, are alloys that exhibit excellent mechanical strength and creep resistance at high temperatures, good surface stability, and corrosion and oxidation resistance. Superalloys develop high temperature strength through solid solution or precipitation strengthening: to a first approximation the elevated temperature strength of a superalloy depends upon the amount and distribution of the strengthening intergranular second phase, which is γ' in the case of Nickel-based Superalloys and carbides in the case of cobalt-base Superalloys.

Superalloys retains strength over a wide temperature range, attractive for high temperature applications where steels would succumb to creep as a result of thermally- induced crystal vacancies.

Creep resistance is dependent on reducing the speed of dislocations within the crystal structure. The body centred cubic gamma prime phase [Ni3(AI,Ti)], present in nickel and nickel-iron Superalloys, presents a barrier to dislocations. Chemical additions such as Aluminium and Titanium promote the creation of the gamma prime phase (γ'). The gamma prime phase size can be finally controlled by annealing. Many other elements, can be present; Chromium, Molybdenum, Tungsten, Aluminium, Zirconium, Niobium, Rhenium, Ccarbon or Silicon are a few examples.

Regarding at the Cobalt base Superalloys, considerable amount of refractory elements are employed in solution strengthened structure, such as chromium, molybdenum or tungsten. These solutes have inhibiting recovery capacity and they obstruct the dislocations movement. Carbides, precipitated at grain boundaries, block the grain boundaries sliding and produce along high rupture life.

Other crucial material properties are fatigue life, phase stability, as well as oxidation and corrosion resistance.

Generally, solid-solution-strengthened alloys are expected to have strong resistance to fatigue cracking due to an increased resistance to slip and an enhanced strain hardening capacity. In general, high temperature fatigue may be thought of a cyclic creep rupture process. For this reason, the relationships between microstructure, creep deformation and fracture, previously described, are applicable.

Focusing on the corrosion and oxidation resistance, the strong resistance against environmental effects is provided by the formation of a protective oxide layer which is formed, by elements such as aluminium and chromium, when the metal is exposed to oxygen and encapsulates the material, and thus protecting the rest of the component.

Namely, but non-exhausitvely, the alloys hereafter identified in table 1 by their UNS, ISO or AFNOR norms are examples falling into the above described families. The table contains, for indicative purpose one of the well-established trade-name of the alloys.

Well-established commercial name Norm (UNS - ISO - AFNOR)

INCONEL® alloy 600 UNS N06600

INCONEL® alloy 601 UNS N06601

INCONEL® alloy 617 UNS N06617

INCONEL® alloy 625 UNS N00625

INCONEL® alloy 625LCF® UNS N06626

INCONEL® alloy 706 UNS N09706

INCONEL® alloy 718 UNS N07718

INCONEL® alloy 718SPF™ UNS N07719

INCONEL® alloy X-750 UNS N07750

INCONEL® alloy MA754 UNS N07754

INCONEL® alloy 783 UNS R30783

INCONEL® alloy HX UNS N06002

NIMONIC® alloy 75 UNS N06075

NIMONIC® alloy 80A UNS N07080

NIMONIC® alloy 90 UNS N07090

NIMONIC® alloy 105 ISO NW 3021 NIMONIC® alloy 1 15 AFNOR NCK 15 ATD

NIMONIC® alloy 263 UNS N0726

NIMONIC® alloy 901 UNS N09901

NIMONIC® alloy PE1 1 AFNOR Z 8 NCD 38

NIMONIC® alloy PE16 AFNOR NW 1 1 AC

NIMONIC® alloy PK33 AFNOR NC 19 KDU

Waspaloy UNS N07001

INCOLOY® alloy 903 UNS N19903

INCOLOY® alloy 909 UNS N19909

INCOLOY® alloy MA956 UNS S67956

INCOLOY® alloy A-286 UNS S66286

UDIMET® alloy 188 UNS R30188

UDIMET® alloy 500 UNS N07500

UDIMET® alloy L-605 UNS R30605

UDIMET® alloy 700 SAE AMS 5846

UDIMET® alloy D-979 UNS N09979

UDIMET® alloy R41 UNS N07041

UDIMAR® alloy 250 UNS K92890 /UNS K92940

UDIMAR® alloy 300 UNS K93120

MP35N UNS R30035

Table 1 : primary list of High temperature performance Superalloys covered by the present invention. Additionally to the previous, the following alloys listed in table 2 and identified by their commercial names and detailed chemical compositions are also among the explicitly covered materials used for the first "modulus", i.e. the high thermo-mechanical solicitation area of the die. The materials listed in table 2 are part of the Ni-base Superalloys defined above : Denomination Ni Fe Cr Al Co Mo Nb Ti W Y203 Ce Si

NIMONIC® alloy

86 65 0 25 0 0 10 0 0 0 0 0,03

NIMONIC® alloy

101 48 0 24,2 1 ,4 19,7 1 ,5 1 3 0 0 0

UDIMET® alloy

520 56 0 19 2 12 6 0 3 1 0 0

UDIMET® alloy 1 ,2

720 56 0 16 2,5 14,7 3 0 5 5 0 0

Table 2 : Ni-base Superalloys of detailed chemical composition and identified by their well-established trade-name.

Additionally to the previous, the following alloy identified by its trade-name and chemical composition is also among the explicitly covered materials used for the first "modulus", i.e. the high thermo-mechanical solicitation area of the die. The material presented in

table 3 is part of the Ni-base Superalloys defined above :

Table 3 : Chemical composition of Ni-base Superalloy AEREX350

On the other hand, in the area of strong tribological solicitation, i.e. friction and wear due to passing alloy being formed, the second modulus of the die which is/are the insert/s, i.e. the so-called bearings of inserts 6 and 7 (area of the die where the extruded profile takes its final shape) is manufactured of a wear resistant material. Such material could be any known wear resistant die material such as a high speed tool steel, a precipitation hardened steel or a high alloy hot-worked stee and alloys being obtained by a standard forging process, a spray forming technique or by powder metallurgy technology or any of such steel or material types provided with surface hardening through nitriding or similar process or by a surface coating technology such as chemical vapour deposition (CVD), Plasma assisted/Enhanced chemical vapour deposition (PACVD/PECVD), Physical vapour deposition (PVD) or other spraying processes (Flame Spray, Cold spray/high velocity, Plasma spray, high velocity oxyfuel Spray, etc..)

The selection of a material different from a nickel, iron or cobalt-base Superalloy belonging the above described groups for the die inserts is a fundamental requirement of the concept of the present invention. This particular combination is crucial for the overall performance of the concept since 1 ) the Superalloy in the die body parts 2 and 3 has superior high temperature mechanical properties but low tribological wear properties while 2) the wear resistant materials in the insert bearing areas 6 and 7 have superior tribological wear properties but low high temperature mechanical properties.

Consequently, with the present invention is achieved the best possible fit between local material selection and local mechanical and tribological solicitations.

Where the stress is high enough to cause plastic deformation, it's preferable to characterise Low-cycle fatigue by the Coffin-Manson relation

where:

- Δε_ρ 12 is the plastic strain amplitude at half life;

- £f' is an empirical constant known as the fatigue ductility coefficient, the failure strain for a single reversal;

- 2N is the number of reversals to failure (N cycles);

- c is an empirical constant known as the fatigue ductility exponent.

A FEA (Finite Element Analyse) simulations, realized on the area of the die which is thermo-mechanical stressed, demonstrated that the transition bridge to mandrel have stress concentration beyond yield limit (these zones are called "hot spots"): this indicates plastic deformation of the material which also has been verified through inelastic simulations. The cyclic behaviour and the registered lifetimes of the extrusion tools show that plastic tensile and compression strains are present during the extrusion process. For this reason, relative to the presence of a plastic strain, it is proper to adopt the Manson-Coffin relation to discuss the fatigue properties of the die material and to benchmark different die solutions.

Fig. 3 shows a linear relationship, on a log-log plot, of plastic strain range versus cycles to failure. The diagram permits to benchmark the fatigue behaviour of the most common tool steels, employed for extrusion dies, with the fatigue properties of a superalloy. It is clear that the superalloy, on equal terms of plastic strain applied at elevated temperature, shows a higher fatigue life than a tool steel. The results highlight the superior fatigue resistance of the superalloys and confirm the good adaptability of these materials for the realisation of the area of the die with a strong thermo- mechanical solicitation

The present invention as defined in the claims is not restricted to the above two cavity die example for extruding hollow profiles based die inserts 6 and 7, but may be one or a three or more cavity type and also single or more cavity die plate for extruding solid profiles.

The invention as defined in the claims is further not restricted to the design as regards the interconnection of the die parts and inserts by means of screws as shown in the figure and described above, but may be secured to one another or interconnected by shrink fit or other connecting means.

Claims

Extrusion tool or die for the extrusion of metallic material, in particular a material of aluminium or alloys thereof, or other non-ferrous metals such as Cu and alloys thereof, the die being a modular type comprising die bodie/s (2, 3) with cavitie/s (4, 5) provided with insert/s (6, 7),

characterised in that

the area of the die with strong thermo-mechanical solicitation comprising the die bodie/s (2, 3), is made of a nickel, iron or cobalt based super alloy, whereas the die in the area with strong tribological solicitation comprising the insert/s, i.e. the mandrel (6) and/or the bearing (7), is manufactured of a wear resistant material.

Extrusion die according to claiml ,

characterised in that

.the die is a two or more cavity die.

Extrusion die according to claimsl and 2,

characterised in that

the alloy is a nickel based superalloy containing Ni 39 - 78 wt%, Fe 0,0 - 36wt%, Cr 12% - 25 wt%, Al 0,0 % - 5wt%, Co (min 0% max 20%), Mo - 10 wt%, Nb - 5 wt%.

Extrusion die according to claims 1 and 2,

characterised in that

the alloy is a cobalt based superalloy: containing Co 34 - 50 wt%, Nil 0 - 29 wt%, Fe 3 - 26 wt%, Cr 3 - 22 wt%, Al 0,0 - 6 wt%), Nb 0,0 - 3 wt%, W 0,0 -15wt%.

5. Extrusion die according to claimsl and 2,

characterised in that

the alloy is an iron based superalloys containing Fe 42 - 74 wt%, Ni 0,0 - 38 wt%, Cr 0,0- 20 wt%, Al 0,0% - 5 wt%, Co - 15 wt%, Mo 0,0% - 5%, Nb 0,0 - 5 wt%)

6.. Extrusion die according to claims 1 - 5,

characterised in that

the wear resistant material is a high speed tool steel, a precipitation hardened steel or a high alloy hot-worked steel and alloys being obtained by a standard forging process, a spray forming technique or by powder metallurgy technology .

7. Extrusion die according to claimsl - 6,

characterised in that

the wear resistant material is surface hardened by surface nitriding or similar process or is provided with a surface coating based on chemical vapour deposition (CVD), plasma assisted/enhanced chemical vapour deposition (PACVD/PECVD), physical vapour deposition (PVD) or other spraying processes such as flame spray, cold spray/high velocity, plasma spray or high velocity oxyfuel spray.