Cold-Mass to Cryostat Mechanical Interface - CERN Accelerator ...

CAS course "Vacuum in Accelerators", 

Accelerators", 

Platja d'Aro d'Aro, 

, 17-24 17 24 May 2006 

Materials of high vacuum technology, 

an overview 

Stefano Sgobba 

TS-MME-MM 

CERN

Outline 

1. General rules for the selection and specification of quality materials materials 

for vacuum technology; an historical perspective 

2. The main families of metals and alloys used in vacuum technology: 

technology: 

from production processes to the final inspections 

⇒ Discussion of 

a) a) Stainless Stainless steels steels 

b) b) Aluminium Aluminium and and alloys alloys 

c) c) Copper Copper and and alloys alloys 

d) d) Other Other and and less less common common materials materials (and (and processes) 

processes) 

Examples of application 

Aspects related to manufacturing, joining, near net shaping techniques 

techniques 

Failure analyses, including corrosion issues... 

3. Conclusions 

30/05/2006 Special CERN Accelerator School 2

General rules 

1. Ease of degassing 

2. Adequate strength at high as well as low T 

3. Thermal expansion coefficients 

1. Ease of machinability and joining 

4. The purity of the material 

2. Sealing glasses, ceramics and other insulators 

5. Exact knowledge of the material properties, critical 

3. Materials selection, to careful yield low control 

outgassing rates 

6. 4. Bakeability 

Very constant properties of the raw materials, to be 

5. Interdependence specially prepared 

of cleaning, joining, construction and 

7. application 

Ease of fabrication and cost of vacuum materials are 

6. Stainless often of steel secondary is the dominant importance material 

(sic !) 

((Espe (O'Hanlon, Espe, O'Hanlon, , Materials Materials A A User's User's of of High High guide guide Vacuum Vacuum to to Vacuum Vacuum technology, technology, Technology, Technology, vol. vol. 1, 1, Wiley, Wiley, Pergamon 

Pergamon 2003) 

2003 

Press, Press, 1966) 1966) 


A look into the historical developments of 

Espe, 1966 

materials for vacuum devices 

Kohl, 1967 

Ti, Zr, Hf and alloys 

Ta, Nb and alloys 


Mo and alloys 

Mo 

Polymers 

W and alloys and alloys 

Copper and copper alloys 

W and alloys 

Precious metals 

Ti, Zr, Hf and alloys 

Nickel and Nickel alloys Precious metals 


Copper and copper alloys 

Mo and alloys 

Aluminum and alloys 

W and alloys 

Stainless Steel 

Precious metalsNickel 

and Nickel alloys 

ckel and Nickel Iron and alloys steels 

Ti, Zr, Hf and alloys Polymers 

Polymers O'Hanlon, 2003 

Mica 

Copper and copper alloysCeramics 


Glass, the miracle maker 

Glass Glass 

Ceramics 

W.H. Kohl, Handbook of Materials and Techniques for Vacuum Devices, 


Irons 

Rheinhold, 1967 

J.F. O’Hanlon, A user’s guide to vacuum technology, 3rd ed., Hoboken, Wiley, 2003 

30/05/2006 Special CERN Accelerator School 4 

Mica 

Carbon and Graphite 

Iron and steels 

Aluminum and alloys 

Ceramics 

W. Espe, Aluminum Materials and alloysof 

high vacuum Micatechnology, 

Oxford, Pergamon, 1966-1968, 3 vol., 

see also: 

H. A. Steinherz, Handbook of high vacuum engineering, New York, Reinhold, 1963 

J. Yarwood, High vacuum technique : theory, practice and properties of materials, 4th ed., London, 

Chapman & Hall, 1967 

K. Diels, Werkstoffe und Werkstoffverbindungen in der Vakuum-Technik, Essen, Classen, 1968

+ cooling 

capillars 

5

+ end covers 

6

fcc 

bcc 

2.a Stainless steels 

δ-Fe 

γ-Fe 

α-Fe 

Stainless 30/05/2006 steel: iron alloys containing Special CERN Accelerator a School minimum of approx. 11 % 8Cr

2.a Stainless steels, steels, 

introduction and ferritic grades 

•ferritic grades, 14.5 % to 27 % Cr 

•resistant to corrosion 

•subject to grain growth during firing 

•ferromagnetic at RT and below 

•brittle at low T 



martensitic grades 

C added to aincrease 

the 

"austenitic loop" 

•martensitic grades, Cr between 11.5 % and 18 %, 

C up to 1.2 % 

•hardenable by HT 

•high strength 

•ferromagnetic at RT and below 

b 

•brittle at low T 


C.Garion, B. Skoczen, S. Sgobba, International Journal of Plasticity, 22, 2006, 1234-1264 

γ 

α' 

α'

AISI 304, the "18-8" or "18-10" 

stainless (18%Cr, 8-10%Ni) 


austenitic grades 

formed by an addition of a 

fcc element (Ni, Mn) Mn) 

to the 

FeCr system 

γ-loop loop expanded 

γ-phase phase enhanced and 

enlarged 

formation of ferrite can be 

suppressed (austenite austenite 

former elements) 

elements 

transformation to 

martensite can be reduced 

or suppressed (increasing 

increasing 

alloying elements) 

elements 

Ni, Mn (C, N...) 




vacuum applications: 304L, 316L, 316LN 

× 

30/05/2006 Special CERN Accelerator School 

× 

× 

Source: ASM Metals 

Handbook, vol. 3, 9th 

ed. (1980) 

School 12


austenitic grades, low C 

Why low C (304L, (304 , 316L, 316 , 316LN)? 316 N)? 

"Sensitization 

Sensitization" " of base metal, metal, 

HAZs and welds 

M 23 

(Cr 23 

23C6 (Cr23C6 

) 

Cr depleted zones 


D. Peckner, I.M. Bernstein, 1977 

A.K. Jha et al., Engineering 

Failure Analysis, in press


austenitic grades, low C 

UNS 21904, Cr20Ni7Mn9N, C=0.03% 

S. Sgobba et al., al., 

Bull. Cercle Et. Mét, , 

10, 1995, p. 13.1 ff. 

ff 




stabilized grades: 321, 347, 316Ti 

316Ti 

J. Källqvist and H.-O. 

Andrén, Mat. Sci. Eng. 

A, 270, 1999, p. 27-32 



7.1 x 

100 x 

1 

4 

100 x 

1 

3 

2 


2 

Oversized (1,2,3) and 

thick (4) B type 

inclusions up to class 2 

100 x 

100 x 

4 

3

7.1 x 


inclusions 

4 

1 

3 

2 

RD ⇔ 

5/30/2006 Follow-up Follow up meeting of 

EB Cooling Blocks MPR 

18


inclusion content 

For any wrought product (plate, tube, bar), an unfavourable inclusions alignment 

will be anyway present in the rolling or drawing direction 

Multidirectional 5/30/2006 forging might not be Follow-up Follow applicable up meeting of 

due to the diameter needed of 


the capable product 

19

The standard ASTM E45-97 E45 97 



20

Investigations of TS-MME TS MME-MM MM 

on the materials supplied to date 

Original magnification : 100 x 

inclusion type B class 2½ 



EDMS 673464: 

27 mm outer Ø, 

4 mm wall 

thickness 

316L tubes 

sample 1 

delivered 

14/10/05 

21

The CERN reference specification 

for vacuum applications 



22

Leaking location 

app. 2 mm app. 2 mm 


app. 2 mm 


10 -5 torr l/sec 

courtesy of A. Poncet

Electrical 

C ↓ 

Arc Furnace: 

functions P ↓ solely as a meltdown 

(to a limited unit extent) 

Tapped as free as possible 

of slag into the ladle 

Degassing, Pure gaseous deoxidation oxigen 

(down blown to 8-15 onto ppm), the metal; 

dehydrogenisation for a pressure of (down 0.02 

to 0.8 bar ppm) abs., desulfurization 

C down to 

(from 0.015 240 % ppm before to 10 Cr 

ppm), losses removal beginof 

Non- 

Metallic Inclusions (NMI) 


Variant: 

PESR, at a working 

pressure of 42 bars, 

to allow nitrogen 

alloying 


Courtesy of Breitenfeld 

Edelstahl /AT 


γ-stabilizers 

CERN 316LN 


welding metallurgy 

CERN 316LN 

Element Content wt% 

Cr 16.00 - 18.50* 

Ni 12.00 - 14.00* 

C 0.030 max. 

Si 1.00 max. 

Mn 2.00 max. 

Mo 2.00 - 3.00* 

δstabilizers 

N 0.14 - 0.20* 

P 0.045 max. 

30/05/2006 S Special 0.015 CERN max. Accelerator School 29 

Fe Remaind er



γ−primary 

solidification 

316LN 

end-covers 

δ−primary 

solidification 

Schaeffler equivalent formulae for Cr eq and Ni eq 

Cr eq = Cr + 1.5Si + 1.37Mo 

Ni eq = Ni + 0.31Mn + 22C + 14.2N 




"mumetal", Ni80Mo0.5Mn0.5; 

S


effect of delta-ferrite 

delta ferrite 

on magnetic susceptibility 

S. SGOBBA, C. BOUDOT, Matériaux et Techniques 95, n°11-12, p. 23 (1997). 

5/30/2006 EMAG 2005, topical seminar 32

Other phase transformationd and their 

influence on magnetic behaviour 

Martensitic transformations 

Antiferromagnetic transitions 

see: 

1) S. SGOBBA and G. HOCHOERTLER : A New Non-Magnetic Non Magnetic Stainless Steel for Very 

Low Temperature Applications, Proceedings of the International Congress Congress 

Stainless 

Steel 1999: Science and Market, Chia Laguna /IT, 6-9 6 9 June 1999, Vol. 2, p. 391-401 391 401 

2) S. Sgobba, Sgobba, 

Magnetic Properties of Materials and Phase Transformations, CERN 

Technical training EMAG-2005, EMAG 2005, 4-14 4 14 April 2005, 

\\cern.ch cern.ch\dfs dfs\\Divisions ivisions\EST EST\Groups Groups\SM SM\Metallurgy 

Metallurgy\Internal Internal\Sgobba Sgobba\Magnetic Magnetic 

materials\Sgobba_seminar_final.ppt 

materials Sgobba_seminar_final.ppt 

5/30/2006 EMAG 2005, topical seminar 33


brazeability to ceramics 

Cu 

304 SS 

o High T (> 500 °C) 

vacuum brazing 

o Metal/ceramic 

matching 

expansion 

coefficient 

(Kovar), and/or 

o Ductility of the 

"unmatched" 

metal 


EB welding 


brazeability to ceramics 

SS 

Kovar 

Al 2 O 3 

Anderson, Ceramic Metal Seal Design, Amsterdam, 1996 

for application to LEIR 

o Anisotropy of ceramics 

o 96% Al2O3 , UTS compression, RT = 2070 MPa 

tensile, RT = 180 MPa 

tensile, 1100 °C = 90 MPa 


2.b) Aluminium and alloys 

Wrought Al alloy designations 

Alloy Group Designation AA 

Pure aluminium 1xxx series 

Al-Cu Al Cu 2xxx series 

Al-Mn Al Mn 3xxx series 

Al-Si Al Si 4xxx series 

Al-Mg Al Mg 5xxx series 

Al-Mg Al Mg-Si Si 6xxx series 

Al-Zn Al Zn 7xxx series 

Al+other element (Li) 8xxx series 

Example 

EN AW-2219 

EN AW-3003 

weld fillers 

EN AW-5083 

EN AW-6082 

(6061) 


6061 4043 


2219 


EN AW-6063 

2.b) Aluminium and alloys, alloys, 

weldability 

Al0.15Cu1.3Mn Al0.15Cu1.3Mn Al0.2-0.6Si0.46-0.9Mg 

EN AW-3003 

EN AW-6063 


(⇒) 


Heat treatable alloys Non heat treatable 

Alloy Alloy Group 

Group 

Pure Pure aluminium 

aluminium 

Al-Cu Al-Cu Al Cu 

Al-Mn Al-Mn Al Mn 

Al-Si Al-Si Al Si 

Al-Mg Al-Mg Al Mg 

Al-Mg Al-Mg Al Mg-Si Mg-Si Si 

Al-Zn Al-Zn Al Zn 

Al+other Al+other element element (Li) 

(Li) 

Designation Designation AA 

AA 

1xxx 1xxx series 

series 


series 


series 


series 


series 


series 


series 


series 


H18 (work 

hardened to 

the hardest 

state) 

O (annealed) 

or H111 (asfabricated) 


Annealing T: 343 °C 

Non heat treatable 


O (solution 

annealed) 


EN-AW 6061 

Toward artificially aged states (T6x tempers) ⇒ 


UTS, YS /MPa El. in 50 mm /% 

300 

250 

200 

150 

100 

50 

0 

2.b) Aluminium and alloys, alloys, 

EN AW 2219 

Properties at RT, affect of aging at high T 

domain of cumulative 

activation of NEG 

0.1 1.0 10.0 100.0 1000.0 10000.0 100000.0 

time at T /h 

YS, aging at 100 °C 








Failure of thin walled Al-alloy Al alloy bellows for the LHCb 

experiment 

• EN AW 2219 bellows 

• machined from forged round blocks 

• welded assembly (2 flanges + 2 bellows + 1 tube) 

• for the LHCb experiment 

• leaks detected on a significant fraction of bellows 

see EDMS Nr.: 681631 

30/05/2006 TS department seminar 43


experiment 



experiment 



2.c) Copper and alloys 

"electrical coppers" 

high strength copper alloys 

Cu OF, C10100 

Cu-2%Be, C17200 

Cu OFE, C10200 

Cu-0.3%Be-0.5%Co, C17410 

Cu OFS, C10700 

99.85Cu-0.15Zr, C15000 

99.8Cu-0.15Al 2 O 3 ,C15715 

70Cu-30Ni, C71500 

"70-30 cupronickel" 

Alloys containing: 

Zn 

Pb 

Cd 

Se 

S... 

might result in 

unsuitable vapour 

pressures 

(J. O'Hanlon, A User's 

Guide to Vacuum 

Technology, Wiley, 2003) 



OFE, OF Cu, respectively 

brazeability, 

weldability 




⇓⇓⇓⇓⇓⇓⇓⇓⇓ ⇓⇓⇓⇓⇓⇓⇓⇓⇓ ⇓⇓⇓⇓⇓⇓ 

⇓⇓⇓ 

⇓⇓⇓⇓⇓⇓ 

⇓⇓⇓ 

courtesy of Stainless 


data for: 


• Cu wire 

• CW 90 % 

• to 2 mm diam. 

then 

• annealed ½ h 

at various T 

(source ASM Handbook) 



2.c) Copper and alloys, alloys, 

Glidcop 

• Copper base dispersion strengthened materials, 

materials, 

referred as: 

Oxide Oxide Dispersion Dispersion Strengthened (ODS) (ODS) Cu Cu or or 

GlidCop®® GlidCop Dispersion Dispersion Strengthened Cu Cu 

• GlidCop, GlidCop, 

trademark of SCM Metal Products, Inc., manufacturer 

of metal powders and pastes for powder metallurgy. 

Based on a Cu-Al Cu Al203 system 

• Oxides immiscible in liquid Cu ⇒ PM techniques + 

thermomechanical or HIP consolidation 

Internal Internal oxidation oxidation 

((Mechanical Mechanical mixing mixing (Zwilski ( Zwilski & & Grant, Grant, 1961) 1961) 

((Coprecipitation 

Coprecipitation from from salt salt solutions solutions (Crosby (Crosby & & Desy, Desy, 

1969) 1969) 

(Selective (Selective internal internal oxidation oxidation (Benjamin, (Benjamin, US US Pat. Pat. 3785801, 3785801, 1974) 1974) 


North American Höganäs tech. data sheet no. 

700A (rev. 2003) 

Nadkarni, Mechanical Properties of Metallic Components, 1993, p.297

• GlidCop® GlidCop AL-25 AL 25 

• based on 2.c) a thermally Copper and stable alloys, alloys reinforcement , Glidcop 

(Al 203 ) 

• acts as barrier to dislocation movement and to recrystallisation 

F. Zhu, L. Jiao, N. Wanderka, R.P. Wahi and H. 

• Cu-2% Cu 2%Be Be, , aged 360 °C, C, 6h 

• based on the usual GP ⇒ 

(γγ'') '') ⇒ γγ'' ⇒ γγ precipitation 

(Rioja Rioja and Laughlin, 1980) 

• thermally unstable system 

(diffusion controlled) 

controlled 

Wollenberger, FIM atom probe study of an Al22 033 dispersion 30/05/2006 strengthened copper alloy, Surface Special CERN Accelerator School 54 

Science 266 ( 1992) 337-341 

0.1 μm 

S. Sgobba, Sgobba, 

thèse th se EPFL n° n 1215 (1994)

Bending Magnet 

Radiation 

Courtesy of R. 

Kersevan 

Normal ESRF Crotch-1 (courtesy of R. Kersevan) 

5 mm 

6 mm 


Diam 

4 mm

2.d) Other and less common 

materials (and processes): 

Powder Metallurgy, Near-Net Near Net Shaping 

56

HIPed AISI 316LN end covers 

for CERN LHC project (courtesy of Metso) 

After capsule 

removal by 

pickling and heat 

treatment, before 

machining

PM 316 LN, Microstructure: 

Grain size according to ASTM E112: N° 6 to 7 

100 μm 

100 μm 

S. SGOBBA, F. SAVARY, J. LIIMATAINEN AND M. KUMPULA, A Powder Metallurgy Austenitic 

Stainless Steel for Application at Very Low Temperatures: Proceedings of the 2000 Powder 

Metallurgy World Congress, Nov. 12-16, 2000, Kyoto, Japan, vol. 2, p. 1002-1005 

59

Original magnification 200 x 

Inclusions 

Mainly globular-type 

150 μm 

60

99.85Cu-0.15Zr, UNS C15000 

99.97+ % Mo

Bimetallic structures 

HIP diffusion bonding, CuZr/Mo Coextrusion, Cu/Ni/Mo 

10 mm

Stainless Stainless steels steels 

3) Conclusions 

o 304L, general purpose ⇒ 5 sFr/kg sFr/kg 

o 304L, vacuum A material applications (metal, alloy) is not ⇒ 8.50 only sFr/kg sFr a "chemical 

/kg 

o 316LN, vacuum applications ⇒ 16-18 16 18 sFr/kg sFr/kg 

composition" or a designation 

o 316LN, blanks ⇒ 50 (up to 135) sFr/kg sFr/kg 

a) a) elaboration 

elaboration 

o P506, 316L convolutions ⇒ 40-80 40 80 sFr/kg sFr/kg 

b) b) definition definition and and extent extent of of the the controls controls 

Coppers Coppers 

c) c) certification 

certification 

Special Special materials materials d) d) or or price price bimetals bimetals 

o OFE Cu ⇒ 23-30 23 30 sFr/kg sFr/kg 

(drawn) 

o Mo, 99.97% (CLIC) ⇒ 1800 38 sFr/kg sFrsFr/kg 

sFr /kg /kg (3D forged) 

o Mo/CuZr Mo/ OF Cu CuZr Selection bimetal (CLIC) as a function of the ⇒ application 

40000 10 sFr/kg sFr/kg 

sFr/m, sFr/m (basis) 

, ∅ 85 mm 

o Ti ETP grade Cu 2, CNGS end a) a) leak leak windows tightness tightness over over a a ⇒ thin thin 54 8 sFr/kg sFr wall wall sFr/kg sFr /kg (velo ( velo (basis) 

windows, windows, LHC LHC 

o Nb OFS (ILC Cu cavities) interconnection ⇒ examples examples 270 27 sFr/kg sFr sFr/kg sFr /kg /kg(tubes) 

(tubes) 

o CuBe, CuBe, 

high (low) Be b) b) orientation orientation of of the the fibers fibers ⇒ 60-70 60 70 (25) sFr/kg sFr/kg 

(strips) 

o Glidcop c) c) integration integration through through severe severe ⇒ 42 $/kg 

welding welding operations 

operations 

(bellow (bellow convolutions vs. vs. end end flanges) flanges) 

Al Al alloys alloys 

Low T, requirement of non-magnetism non magnetism require special 

o plates EN AW 1050 ⇒ 5 sFr/kg sFr/kg 

special 

o plates EN care EN care AW 5754 ⇒ 7 sFr/kg sFr/kg 

o plates EN AW 6082 a) a) beam beam screen screen of of LHC LHC ⇒ 6.50-8 6.50 8 sFr/kg sFr/kg 

o special forgings, EN b) b) AW RF RF contacts, contacts, 6061, velo Co Co content content windows ⇒ 18 sFr/kg sFr/kg 



Proper selection should keep into account: 

a) a) availability availability (Ti (Ti grade grade 2 2 plates plates for for the the CNGS CNGS end end 

windows, windows, EN EN AW AW 2219...) 2219...) 

b) b) ease ease of of fabrication fabrication into into a a given given form form (EN (EN AW AW 6082...) 6082...) 

Selection as a function of properties and further 

operations 

Corrosion issues 

a) a) strength, strength, ductility ductility as as a a function function of of T T (cryogenic 

(cryogenic 

applications, NEG NEG activation, activation, baking...) baking...) 

b) b) weldability weldability (Al--alloys...), 

(Al alloys...), machinability (pure (pure Cu...) Cu...) 

a) a) thin thin walled walled components components (LHCb ( LHCb velo velo windows, windows, 

bellows, bellows, ATLAS ATLAS Pixel Pixel cooling cooling circuit...) circuit...) 

b) b) use use of of halogen--activated halogen activated fluxes fluxes to to be be avoided avoided in in a a SS SS 

environment 



Consider the material aspects at the beginning of a 

project: 

a) a) availability availability (more (more than than 1 1 y y delay delay for for a a special special SS, SS, 

P506 P506 for for the the beam beam screen) screen) 

b) b) interest interest of of considering considering alternative alternative techniques, 

techniques, 

including including near near net net shaping shaping(PM 

(PM for for the the end end 

covers covers of of LHC LHC dipole dipole magnets) magnets) 

New projects will eventually force into less 

conservative solutions: 

bimetals bimetals by by HIP HIP assisted assisted diffusion diffusion bonding, bonding, explosion explosion 

bonding bonding (CLIC, (CLIC, ILC)... 

ILC)...

Cold-Mass to Cryostat Mechanical Interface - CERN Accelerator ...

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