1 ATLAS Upgrade Meeting LBNL Sept 6 th 2012 Richard French, Hector Marin-Reyes, Simon Dixon, Paul...
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1 ATLAS Upgrade Meeting LBNL Sept 6 th 2012 Richard French, Hector Marin-Reyes, Simon Dixon, Paul Kemp-Russell The University of Sheffield Martin Gibson,
1 ATLAS Upgrade Meeting LBNL Sept 6 th 2012 Richard French,
Hector Marin-Reyes, Simon Dixon, Paul Kemp-Russell The University
of Sheffield Martin Gibson, John Matheson, John Hill, John Noviss
RAL Ian Mercer - Lancaster Orbital Welding Development
Slide 2
Started orbital welding in 2007 with the design methodology of:
100% reliable connector-less system. The tube will be galvanically
more stable than the parts joined to it (e.g. grounding, supports).
The exceptions are joints, seals and connectors, these will have
the same electro- potential as the tube. 2 Step back and sanity
check? Correct technology/materials? Tube material, diameter, wall
thickness, equipment portability are all obvious factors of which
joining method to adopt. There are hundreds of subtle influences
that blur these definitions. Assuming ideal tube is no longer 316L
stainless steel of ~200um wall > Now CP2 Ti, 125um wall or
thinner would I choose TIG orbital welding again without our
knowledge of this technique? On paper the equipment specifications
say no nothing other than laser, EB, microplasma diffusion bonding
or brazing should work reliably at this wall thickness to make a
welded joint in CP2 Ti. Non-specialist experts would also suggest
no. IGNORE SPECS TIG WORKS WELL & IS PROVEN WITH HIGH
REPEATABILITY as a result of the last 6 years R&D and work with
specialists in industry. Ive learnt a significant amount about
joining process for both 316L and CP2 Ti materials. Get the
material right - the joining process follows naturally. Get the
process correct and you have highly repeatable joint. 6 years of
materials development and refinement to make 2 bullet points!
Slide 3
TITANIUM DEVELOPMENTS Assuming we are still on the correct side
of sane Achieving the correct material to work with in the first
place. 3
Slide 4
Oxidation of the Ti tubes - complete Removal investigated
through wet and dry etchants Dry etchants Fun stuff Plasma cleaning
of ends Looks like this might work, on short samples a reasonable
result is achieved. For the full circuit mods to the plasma
cleaning machine are required for a UHV seal to the tube. Shot
blasting with glass bead Works fine but requires very careful
cleaning. NONE APPLICABLE TO IN-SITU REPAIR (Scotchbrite)
Attempting to remove this HN03:HF dilute HN03:HF concentrate Wet
etchants Nasty Chemistry HF based solutions and trials carried out
by, Martin Wilson STFC. Repeat/refine Swantek Jerry Lancaster. fin
HTT/ Anipol?NDT ltd. fin SOLVED AND TRANSFERRED TO INSDUSTRY
Slide 5
Tube developments Need to begin pressure drop measurement
component manufacture for realistic results of mass flow etc to
refine tube dimensions (ex & cap). 6Al4V Ti tube procured for
alternative weld trials (is a better material all round) but
impossible to obtain stock in our small dimensions because of low
volume required. Could be made if we know a final quantity but our
consumption is likely still to be too low. Will continue to gather
joining data as will be done and published an ideal but maybe not
realistic GETTING A LEAK TIGHT SEAL ON ODD SIZED TUBE FOR TESTING
IS A PAIN IN THE A##. Everything is custom! Still a bad idea. 2 -
2.5mm OD please! Can only manufacture in 3m lengths due to EU
cleaning chemical rules working on special dispensation but will
need assistance as not much information available. 5 CP2 Ti well
proven and now established in use, oxide issues solved in
production using chemical etch solution (pickling) and cleaning
process ok and proven, inspected & tested at CERN. Now need
final CT images (125um wall) and evaluation from NAMTEC (freebie)
to finalise reporting. # Still not made many items in this material
Exhaust dimensions or on-Stave cooling tube guessed> 2.175 OD x
0.125mm wall (CP2 Ti), shared by IBL/PIXEL = sharing statistics and
reporting. 50um image of tube end small edge defects
Slide 6
Ti tube capillaries Capillaries diameters and wall thicknesses
now being prototyped. Initial problems, 3m length, 150um wall was
difficult to get round (stock sizes). Current capillary dimensions
on offer (easy as drawn from stock) MINIMUM BORE 0.3mm, MINIMUM
WALL 0.150mm, MAXIMUM LENGTH 3000mm 1.2mm OD x 0.90mm ID x 3000mm
0.80mm OD x 0.50mm ID x3000mm 0.60mm OD x 0.30 ID x 3000mm
Prototype capillary tubing fresh from the mill has now reduced wall
to 0.750mm OD x 0.490mm ID x 0.1300mm Wall. 0.670mm OD x 0.405mm ID
x 0.1325mm Wall. 0.595mm OD x 0.330mm ID x 0.1325mm Wall. 130um is
about as low as sensible to pass pressure testing with headroom we
need good old fashioned measurements now to determine the ID.
0.330mm ID is the smallest ID possible using this manufacturing
process and UK factories. Larger IDs than 0.5mm possible through to
0.9mm ID. Real testing is needed to enable further refinement, but
its a start.. 6 AIMING TO REDUCE MASS OF WALL TO 0.125mm. Unlikely
to be lower!
Slide 7
Tube stock availability & lead time Production Sample
MaterialOD mmID mmWall umlength m StockDue Offcut Qty P/S/O CP2
Ti3.1752.7752002.2m22P CP2 Ti2.2752.0251253.0m250P CP2
Ti2.2751.9951403.0m18 CP2 Ti1.7751.5251253.0m8 CP2
Ti1.2000.4002003.0m6P CP2 Ti1.2000.9001500.6m417S CP2
Ti1.0000.4502753.0m2P CP2 Ti0.9000.3602703.0m2P CP2
Ti0.8000.5001503.0m18P CP2 Ti0.7500.4901300.6m6S CP2
Ti0.6700.405132.50.6m6S CP2 Ti0.5950.330132.50.6m6S 316L
SS3.1752205.0m14P 316L SS3.1752201.8m5O 316L SS3.1751402.7m18P 316L
SS3.1752201.8m4O 316L SS3.1757502.0m4S 316L SS2.0001402.0m53P
Aluminium3.1753605.0m32P Aluminium3.1756605.0m74P
Aluminium2.4806603.0m69P Aluminium4.7603402.5m69P 7 Capillaries had
too much mass in tube wall for optimal xo performance. Looking at
max burst pressure v watt thickness but large manufacturing
constraint as stock sizes dictating final drawn size of ~130um wall
Can only purchase as international community to persuade Sandvik to
supply stock in small enough volume. ~0.25 Tons. I still doubt that
we can achieve MOQ collectively so a rethink is needed. Need to
finalise a suitable joining solution as EU REACH preventing
production longer than 3m check if international shipping dispenses
company from regs and store tube at CERN? VAT?
Slide 8
PEEK capillaries 8 This is not a serious proposal! Ti
production currently limited to 3m lengths 10m PEEK capillaries
purchased for fun with ingenious finger tight 500bar connectors
PEEK (polyetheretherketone) finger tight fitting are convenient,
inert, and bio- compatible. 1/16 inch O.D. PEEK, stainless steel,
titanium, Tefzel, or PTFE tubing. Compatible with most solvents
(not concentrated sulfuric and nitric acids), PEEK ferrules do not
permanently lock into place on the tubing. ODID 360 m75 m 1/32"0.13
mm 1/16"0.064 mm ODID 1/875 m 1/8"1.59mm 1/8"2.0mm
Slide 9
Orbital TIG joint repeatability CP2 Titanium1/8OD x 0.20mm wall
1042 repetitive welds First 20 welds suffered from same lack of
refinement as 316L process. Testing at CERN for random batch
samples shipped. OXIDE was a problem specific to this batch of Ti
tubes only. Regular cleaning is increasing repeatability. More
attention is paid to the joint preparation. And electrode. WPS
being written (best practice) 9 The process is highly repeatable
for both materials (316L & CP2 Ti) and now highly optimised. I
need to check this again with a number of fixed tubes representing
detector service connections then repeat the process for the CP2 Ti
2.275mm OD x 120um wall when happier with the weld itself. Weld
head angle. Electrode start position. Clearance for weld head
Internal gas purge pressure may be the tricky item to manage
correctly during installation in the cryostat. CP2 Ti weld
joint
Slide 10
10 Flare one end of the tube to bring extra material into the
overlapped joint. = 120m + 120m give a bulbous weld bead (now
controlled to outside of tube by altering angle and depth of
flaring tool) Welded joint wall of ~220um wall at highest measured
point = straight tubeflared tube insert weld ~60m Welding of CP2
Titanium 120m wall tube First butt weld joint in 2.275mm CP2 Ti pin
hole every time. Can successfully join the 2.275mm OD x 120m tube
with orbital welding using the above process. Initial NDT results
are underway (x-ray). Data returned (x-ray only) and have refined
inclusions by better cleaning methods. This can be refined much
further as not happy with visual results. ON THE LIMIT OF THE
MACHINE Gas purge issue is due to custom fittings not sealing
correctly on tube OD. Refined but not fantastic. Thrown fittings
away and use soft Si tube (gas contamination) Best welded joint to
date using new tooling to create sleeve joint. Still have a
indentation from post weld cooling [pressure or cleanliness] Will
now start high repeatability trials with this material. 1000
samples (Ti shortage)
Slide 11
Welding system evaluation From my 2007 market survey, the
Swagelok M200 TIG Orbital welding system was the best priced
system: CHEAP BY COMPARISON with other systems. EASY TO USE
software removes operator knowledge WORKED OK FOR BASELINE 316L
TUBE SERVICEABLE & SUPPORTED Has broken once, weve blown it up
once or twice. Original system at Sheffield working fine 2 nd
System based at RAL. CAN NOT WELD 125um CP2 Ti FAILS TO WELD 180um
wall tube. Weld heads all need to be modified to work well.
Software all needed serious messing with. Effort v cost = not so
good. Once the Ti wall went to 125um it caused me problems With
enough time most things work in the end. Biggest issue is high
powered arc starting AV causing potential issues for damage to
electronics 11 Swagelok M200 COTTS Sheffield micro-weld head
Slide 12
Future plans for M200 development 12 Weld head mods at
Sheffield have tried UHP small weld head on loan from manufacturer.
Have constructed digital IO to analogue module to interface to
M200, unsure if was sensible use of effort as virtually removes all
M200 useful functionality. Modified version of the smaller scissor
jawed weld head from Swagelok is working well but needs further
refinement for joining 125um CP2 Ti. Electronics damage slowly
understanding more with the system outputs and quirks, producing a
best practice guide to avoid majority of misfires. Reprogramming
the system outputs (altering M200 welding software) for lower
initial start arc trade off with arc ramp down may be a waste of
time but worth a try. Adding grounding system to drop initial arc
start voltage proving problematic so again, firmware needs altering
inside machine to allow arc to start Keep popping bits of the
machine but it is easy to repair and quite robust. Weld head
internal temperature measurement is in progress. Set up under
construction for use with Tims FEIR camera. Tech effort dependent.
LASER WELDING still on going investigations from Ian Mercer, we did
expect some delay from SPI before final ideas placed on paper.
Hopefully news soon. Ultra pure gas purge system
Slide 13
Understanding system performance Getting to grips with the M200
quirks. Misfires mainly caused by bad practice, poor joint
alignment and laziness. Correct procedure does solve this.
Occasionally there is a weird event. 1000 welds on identical CP2 Ti
stalks has seen 3 misfires = 3 failed joints. 1000+ welds on 316L
tube has seen 5 misfires = 5 failed joints. WHY? Tmperature alters
gas pressure so need to adjust as lab warms up RH should not affect
closed chamber welds measured, undecided as low stats We have no
real way of measuring this. Right now I dont believe the OSD/GUI
showing A/V of the weld = RMS + fudge factor. 13 SO- measurements
needed HOW? Looks nasty on first investigation but possible.
Swaglok M200 has reverse engineering protection in the system
connection of scopes and probes etc cause misfire or failure to
start weld procedure. It pretty simple in reality so weve figured
out how to get round this & can now take measurements.. But
before this..
Slide 14
We made something new 14
Slide 15
New welding system development Over the past 5 years in
conjunction with our industrial partner Sheffield has developed an
fully automatic TIG welding system that produces accurate low
current narrow bead welds sourced from our partners aerospace
joining knowledge. It was obvious that nothing like this was
commercially available. From the use of high frequency pulsing
interposed within the pulsed weld current gives the system its
unique characteristic and is capable of joining two razor blade
edges together without distortion. The benefit of this technique is
that increased arc force or penetration is achieved with a lower
input current which is crucial to thin wall Ti tube welding by
allowing for improved heat management on critical welds whist still
attaining full penetration. Has additional grounding to prevent
high arc start voltages through work piece Production version fully
tested in Sheffield available to ATLAS Upgrade for R&D. Looks
to be capable of joining >125 um Ti using minimal power how
thin? No idea at all (yet) ~0.3A, 30v on 250um CP2 Ti tube
(automatic weld) 15
Slide 16
16 Waveform arc v profile PLEASE DO NOT REPRODUCE
Slide 17
System Details Initial Current 0.1 60 Amps Upslope time 0.0 20
Seconds Downslope time 0.0 20 Seconds Finish Current 0.1 60 Amps
Finish time 0.0 25 Seconds Pre purge gas 0.0 100 Seconds Post purge
gas 0.0 100 Seconds Main Current 0.1 60 Amps Background Current 0.1
60 Amps Main time 0.01- 5 Seconds Background time 0.01- 5 Seconds
InterPulse Current 0.0 60 Amps Time per level 0.01- 99.9 Seconds
Supply 230Volts 13 Amps 50Hz 17 2.275mm OD tube weld cassette &
head with arc start grounding Current set up in old lab, 3 TIG weld
systems 2 auto, 1 manual. First weld set to offer the ability to
weld single crystal and difficult to weld alloys such as Inconel
738, 713, MAR-M 247, PK33 and Titanium without a chamber or
trailing gas shield. Pulsing switched off 60 Amps at 14 Volts (10
minutes welding 5 minutes cooling) Pulsing switched on 50 Amps (60
A Main, 40A Background) (10 minutes welding 1 minute cooling) 50
Amp Auto TIG version (130 Amp too big for ATU)
Slide 18
Weld head 18 Set up of electrode distance with shim needs
refining Additional clamp for grounding during arc start Remember
start position and direction
Slide 19
19 New system programming/test 2 years work in 6 hours! Joints
made with 0.4A & ~14v no pulsing
Slide 20
20 Weld Parameter Sheet ParametersValues Joint typeTube-Tube,
Tube,rod? MaterialTi, SS? Diameter (mm) Wall thickness (mm) Tube
length (mm) Electrode Gap/Arc Gap/Set (mm) Electrode diameter (mm)
Electrode type2% Th02, 2% La02? Electrode length (mm) Electrode
Angle (deg) Electrode UsageNew, # Welds? Tip Angle Weld HeadOrbit,
Manual (turntable)? Levels1, 2,..? By simplifying the weld build up
as individual parameters, we can make accurate reproducible joints.
This approach is essential to automatic welding
Slide 21
Generic weld system measurements Initial set up (principle so
may refine) Torch micro-positioner & rotary table Can enclose
in environmental chamber to match head conditions. FTIR window for
arc profile Some nice shunts for both A/V (plug and play to USB
with some of our own software) monitoring both positive &
negative outputs (electrode negative TIG system) Power analyser
measuring consumed power at 4 points in the system, mains input,
pre start cap, pre main weld IC, ramping IC. Will refine as
understood. Using timestamp and data values linked via pc to both
measurement systems we should see the variations. We will then
induce failure to measure and understand what happens. We can then
plug in the separate work-piece ground and remeasure. Doubles up to
measure electrode tip angle effects on arc profile and subsequent
power / heat input to tube. 21 Turntable Manual torch micro-
positioner & fast scope USB shunts
Slide 22
22 System measurement schematic Input measured by power
analyser Output by shunts Timestamp and data collected together in
LabVIEW programme NOT tried out in anger
Slide 23
23 System measurements Single & 3 phase measurement Input
voltage/current measurement Output voltage/current measurement
Triggers at arc start Configures to open and closed chamber weld
heads or torch Synchronised data taking Hopefully learn nothing
nasty!
Slide 24
Electrodes for TIG Will drive you crazy. Swagelok items have to
achieve CE certification. They are not fantastic for our use. Need
to understand tip/length reproducibility v performance. Custom
electrodes made in-house at Sheffield outperform standard items.
Measured by reduced heat damage, deeper penetration of weld = ~35%
less arc power needed need to work out how to cut tungsten to
length accurately without shattering electrode (causes premature
wear / arc failures) Struggling for clean space electrode prep
contaminates area and reduces weld performance. New lab taking time
refurbishment very slow. 24 Tube/Electrode preparation area Current
issues are debris contamination so need some form of extraction
building does not permit ventilation to outside world (Dyson?)
Should store electrodes dry drawers needed Bake out before use
oven? Separate grinding machines (or wheels) for different
materials final choice = 1 wheel only Tube cutting proving
laborious Tube facing tool performance satisfactory TOO MUCH STUFF
FOR ONE PLACE TIG grinder (wet) Tube cutter Tube facing
Slide 25
Decision time Theoretically there is only one of me, my time is
split many ways and I need to be more efficient. Assuming that
125um wall tube is desirable Id sooner put effort into new system
testing and give up with pushing the M200 past its limits and use
this for tube wall >200um (services). I reckon we have ~50
separate measurements to make for each weld to fully quantify and
understand each. Ive not made the time to document this work but
have reasonable notes. Im in danger of forgetting as pace picks up.
Odd ODs cause huge tooling costs in fittings, weld heads etc.
Pressure drop work is now ~ 1 year behind where we wanted to be. We
have many of the components but not enough to move forwards to
allow us to decide on tube IDs (EX &Cap). Laser welding has
gone very quiet needs a push. 25
Slide 26
Next 12 months overview Assuming we have minimal decisions made
so rather vague or exceptionally obvious Stave, Stavelet cooling
circuits Re-stock of cooling circuits and stavelet circuits.
Include pressure testing > DATABASE entry. Re-stocking of tube
material and bending trials on capillary tubing Pressure drop
measurements Components part produced design finalisation required
CO2 plant booking expired. This area has stalled and we are in
trouble here. TIG Orbital Welding. Reprogramming M200 and using
grounding system from new system Gas purge over long distance and
multiple manifold measurements/effects on weld quality.
Measurements of electrode tip angle arc gap and power v weld
quality Finalised electrode seeking mass production or tooling to
make in house. Continuing to refine Swagelok weld head for heat
sinking and improved tube alignment. Bring online the InterPulse
system and test on 2.275mm OD 125um wall CP2 Ti. Laser welding
Hopefully news soon. Material reduction Changing bulbous sleeve
joint to butt weld on 125um tube with tooling from PIPE ltd.
Reducing mass in capillary tube wall production limits. Fittings
Vac brazed stubs full statistical trial. CP2 ti fittings material
sourced from Sandvik. Need to check cost out v custom fitting from
Swagelok or Fti plus the effort put in at QMUL. Re-manufacture of
6LV VCR thin wall fittings as run out. Thermal shock etc in the
pipe line at some point hardware almost completed at RAL. Burst
testing of circuits to see where calculated headroom is v actual
mass reduction maybe. 26
Slide 27
ADDITIONAL INFORMATION Alternative joining technique Vacuum
Brazing of CP2 Ti to 316L Stave 250 drawings of cooling tubes at
z=~1.3m 27
Slide 28
28 Overview Stainless Steel to Titanium joining (temp
connection) Copper to Titanium (pressure drop measurements) ATLAS
Upgrade dissimilar metal joining activities Richard French, Paul
Kemp-Russell: Sheffield Keith Birmingham: Aerobraze Europe Neil
Austin: VBC Group Ltd (brazing division) Trevor Smith: Firmachrome
Ltd Peter Cookson: Bodycote
Slide 29
Connectors Swagelok VCR in 316L works well as temporary
fitting. Used 316L weld on VCR either with a TIG weld or Vac Brazed
joint. Mass of nut is an issue, also nuts are sliver plated inside
to prevent galling which has proved problematic for vac brazing.
LOW mass fittings VCR in CP2 Ti could be possible, can only find
reasonable stock in Grade9 Ti to produce. QMUL CNC? Units of
production too low for Swaglok MOQ Vac brazed stubs work well need
statistics Ideally remove the stub preferring tube-tube joint for
low mass and increased reliability - relatively easy to do with a
sleeve jointed TIG weld (common in nuclear reactors etc) not ideal
for dissimilar material joining Can vac braze 316L stainless to
CP2, Grade 9 and 6Al4V Ti without issues (other than getting the
final ones back). Vac brazing ceramic to Ti & 316L next
(ideally write up so far before this) 29
Slide 30
Stainless VCR connector to Ti tube Used to make temporary test
fitting stubs for cooling circuits Method A = cheap idea
Electroless Nickel Plating. Electroless Nickel coating is an alloy
of nickel and phosphorous. Ability to work to close tolerances
without post-plating grinding, whilst holding the original surface
finish. Electroless Nickel can improve corrosion resistance, wear
resistance, lubricity, solderability or be used to rectify and
recover close tolerance undersize parts. The big advantage of
elecroless (chemical) plating over electrolytic plating is it will
adhere to Titanium, in a very controlled manner. We do not need to
plate the entire circuit, just local areas as wherever the solution
touches it will plate. Method B = proven but expensive Vacuum
Brazing using an aerospace proven method Using a silver copper
eutectic braze alloy, coat the Ti with the alloy, assemble the
Stainless VCR fitting to the tube (post electro-polishing) and
place in furnace at a lower temperature somewhere around 850C.
http://www.vbcgroup.com/focus/Brazing-Division/Brazing-Alloy-selection-tables/BrazePrecious.htm
Excellent joint, clean and pressure handling proven up to 250bar.
3.175mm Ti has heavy oxidisation that is proving difficult to
remove. This is needed for the Cusil alloy to adhere to the Ti
tube. Once tube is cleaned (glass bead blasting) good adhesion is
found. 30 Both methods are the active or direct joining of
dissimilar materials with a braze filler metal (BFM). This is ideal
for Ti as the BFM forms a strong permanent joint with the base
materials. What we did not realise is that at certain temperatures
the Ti can suddenly start taking on alloying abilities with the
BFM. This should not have happened when correctly controlled.
Titanium is a strong oxygen-getter, and thus will react with any
oxygen that it can as it is heated from room temperature up to
brazing temperature, therefore, "reacting" too early. This is with
free oxygen or water-vapor in the furnace atmosphere, or with
metal-oxides on the metal surfaces during heat-up (such as when the
metals are not properly cleaned prior to brazing), then the so
called brazing (joining/bonding) of alloy-to-metal may be
completely prevented from happening.
Slide 31
Method A During this process, the bonding was be very
successful but, the difference in the thermal expansion between the
6LV stainless steel Nickel Titanium which it is being joined caused
premature cracking to develop in the brazed joint upon cooling. If
we did not see the cracks at this stage they would present
themselves during subsequent use in service. It is very important
to try to match the expansion characteristics of the metals to
filler to metal joint, so that huge stresses in the joints are not
built up. During the furnace cycle (1100C) something really odd
happened. High temp was down to a miscommunication. The braze alloy
has a initial melting temp of around 400C. The furnace temp was in
the region of 1100C. Therefore we managed to alloy Ni with Ti: 31
Stress cracking CTE mismatched Ni-Ti alloyed tube As the Ti reaches
600C the oxygen in the Ti starts getting thirsty and in the
resulting exchange drags the Ni into the microstructure. As the
assembly cools, it falls apart as the CTE mismatch is beyond what
the structure can cope with. GOOD NEWS we dont necessarily need to
vac braze all our components and can do this with any induction
furnace (have small tube furnace in lab ready). Ni plating works
fine so will drop the cost of the heater block joining for pressure
drop work.
Slide 32
Method B = OK! For mechanical tolerance, achieve a good push
fit in the Ti tube to VCR fitting. Micropolish fitting. Using Cusil
braze alloy from VBC simply clean components and plate the
Stainless Steel component. Mechanically clean Ti, chemically clean
the Ti, assemble components and remember your nuts. Place in
furnace at 850C and cycle once allowing time to cool. Bingo one
joint. Items of weirdness to note: The VCR nut threads are silver
plated to prevent gauling during assembly. This silver is reflowed
during the furnace cycle. 32 NEW REFLOWED 1/8 Ti to VCR 2.275mm OD
Ti to VCR
Slide 33
33 What is length tube sticking out from stave end? Universal
decision for 250. EOS how does this shape up?