Considerations on refractory metals, Considerations on refractory metals, including results from a discussion including results from a discussion with Planseewith Plansee

Stefano Sgobba EN-MME-MMCERN

HI-LUMI meetingHI-LUMI meeting, 4/09/2012, , 4/09/2012, brainstorming shielding, beam screen and beam tubebrainstorming shielding, beam screen and beam tube

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Message from Ezio in date 16/05

“Si tratterebbe di 20 magneti di 8 m di lunghezza. Ciascuno con 4 inserti di tungsteno a calotta, raggio di curvatura 64.3 mm, spessore massimo di 2.3 mm, e quindi sottendenti un angolo di 30 gradi. Tolleranze dell'ordine del 0.1 mm.”

1. Shielding material, W1. Shielding material, W

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Remarks from Plansee:Remarks from Plansee:

Suggest to apply heavy W machinable Suggest to apply heavy W machinable alloys, namely WNiCu (non-magnetic) alloys, namely WNiCu (non-magnetic) gradesgrades

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Results from discussion:Results from discussion:

1.1.8 m could not be achieved, length to be filled from short 8 m could not be achieved, length to be filled from short piecespieces2.2.Not extrudable, at least not direct experience in Plansee Not extrudable, at least not direct experience in Plansee (Lutch ?)(Lutch ?)

3.3. The thinnest, the most realistic to be obtained net shaped The thinnest, the most realistic to be obtained net shaped or with limited machiningor with limited machining

4.4. Thick pieces will require more extensive machiningThick pieces will require more extensive machining5.5. Production could go through deep forming of sheets + Production could go through deep forming of sheets +

machiningmachining6.6. In case, alternative machinable W alloys could be In case, alternative machinable W alloys could be

envisagedenvisaged

7.7. Cost: 180 – 250 EUR/kg Cost: 180 – 250 EUR/kg

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2. Beam screen material, Ta2. Beam screen material, Ta

o Readily weldable by EBReadily weldable by EBo Weldable in TIG and laser, but Weldable in TIG and laser, but

very sensitive to embrittlement very sensitive to embrittlement from interstitial impurities such from interstitial impurities such as O, H, C, Nas O, H, C, N

o Requires perfect gas shielding Requires perfect gas shielding (e.g. glove box enclosure)(e.g. glove box enclosure)

o Low CTE, approx. half of AISI Low CTE, approx. half of AISI 300 austenitic SS, to be 300 austenitic SS, to be compensated due to the compensated due to the presence of components in presence of components in 316LN or similar316LN or similar

o Young modulus similar to Young modulus similar to austenitic SS, 183 (191) GPa at austenitic SS, 183 (191) GPa at RT (4 K) RT (4 K)

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Yield strength up to 120 ksi (830 MPa) at – 200 °C (Bechtold, 1944, reported by Barrett, 1957) or above 100 ksi (690 MPa) at 77 K (Wessel, 1956, ibidem).

o UTS reported at 20 K: 130 ksi - 900 MPa (Ogden et al., 1961) o Reduction in area keeps high, no ductile-to-brittle transition temperature (DBTT). Elogation at breakdown of 9 % reported at 77 K (ibidem)o At 4.2 K "ductility is retained in tensile tests down to 4.2 K" (Basinski reported by Barrett)

• Valid for very high purity materialValid for very high purity material• bcc refractory metals but belonging to V-A transition element bcc refractory metals but belonging to V-A transition element

groupgroup• Maintains sone cryogenic ductility, contrary to other refractory Maintains sone cryogenic ductility, contrary to other refractory

bcc of VI-A group (W, Mo e Cr) with marked DBTT, even above bcc of VI-A group (W, Mo e Cr) with marked DBTT, even above RTRT

• Welds could be less favourable ("pick-up" of interstitials)Welds could be less favourable ("pick-up" of interstitials)

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Results from discussion with Plansee:Results from discussion with Plansee:

1.1.Ta readily rolled Ta readily rolled 2.2.Good formabilityGood formability3.3.Rolled and welded tube nominally possible Rolled and welded tube nominally possible 4.4.Weld restrictions (EB, or total absence of contamination Weld restrictions (EB, or total absence of contamination during welding...)during welding...)5.5.Fully different approach than actual beam screen: rolling in Fully different approach than actual beam screen: rolling in strips not possiblestrips not possible6.6.Limited ingot sizes, sheets with max. 2 m length for a Limited ingot sizes, sheets with max. 2 m length for a thickness of 1.5 – 2 mm and the usual 600-700 mm widththickness of 1.5 – 2 mm and the usual 600-700 mm width7.7.Usual lengths 0.5 m – 1 mUsual lengths 0.5 m – 1 m8.8.Colamination with Cu (requiring strips) not possibleColamination with Cu (requiring strips) not possible

9.9.Seamless pipes can be processed up to 50 mm diameterSeamless pipes can be processed up to 50 mm diameter

10.10. Sheet to sheet productionSheet to sheet production

11.11. Cost: 800 - 1000 EUR/kg for sheets + additional Cost: 800 - 1000 EUR/kg for sheets + additional operations, compared with P506 SS for beam screen (40 – 70 operations, compared with P506 SS for beam screen (40 – 70 sFR/kg)sFR/kg)

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Conclusions

o Shielding W based components feasible, with more or less machining required

o Outgassing of material (vacuum firing) recommended

o A feasibility study could be proposed to Plansee based on production of few components, to test in particular near net shaping and forming

o For beam screen and cold bore, we suggest to stick to conventional metallic material solutions, taking into account costs, industrial feasibility and post installation processing

o More exotic solutions like Ir:

- high Young’s modulus 556 GPa a RT, 557 at 4 K

- hot formable, including by extrusion (Ohriner et al.)

- limited RT formability, including by rolling (warm or through several annealings)

- weldable by EB

- cost up to above 10000 CHF/kg (CES Granta), spot price up to 23000 cost up to above 10000 CHF/kg (CES Granta), spot price up to 23000 USD/kg o 42000 USD/kg depending on puritiyUSD/kg o 42000 USD/kg depending on puritiy

- fcc but DBTT unless very high purity