# Presentation: 493124

## 3rd Harmonic He Vessel Welding

**Helium Vessel-to-Cavity No. 3**

- 22 June 2008

## Helium Vessel to Cavity #3 Welding

**Overview of Welding Sequence**
**	****1.  EB weld titanium helium vessel to large Ni55Ti conical end cap.**
**	****2.  EB weld titanium stepped end ring to small Nb55Ti conical end cap.  This weld has an additional weld pass that differs from other dressed cavities.**
**	****3.  TIG weld titanium stepped end ring to titanium helium vessel**.

## Vertical Welding Fixture Setup

**Vertical Welding Fixture Setup**

- Place 9-cell niobium cavity with
- main coupler end down and large end-group clamped to “Leveling Plate” on fixture.
- Add helium vessel support threaded rods.

- Leveling Plate

- Clamp Block

- Small End-Group Flange
-                (Ni/Ti)

- Large End-Group Flange
-                (Ni/Ti)

- Support Rods

## Helium Vessel Placement

- Lower vessel and align vessel step to cavity end-group step. Secure with spring washers and thumb nuts.
- _Hand tighten thumb nuts only!!_
- Insure proper clocking of the helium vessel with respect to the cavity.

- Thumb Nut

- Flat Washers

- Spring
- Washer

## Helium Vessel to Cavity #3 Welding

**STEP 1:  EB weld titanium helium vessel to large Ni55Ti conical end cap on large end group flange**
**	****A.  Tack weld in four places at 90 degree increments -- E beam horizontal (perpendicular to cavity axis).**
**	****B.  Remove support rods.**
**	****C.  Place four additional tack welds between the original four tacks.  Execute circumferential EB weld with E-beam horizontal (perpendicular to cavity axis).**

## E-Beam Weld – Ti Vessel to Large End-Group Flange

**E-Beam Weld – Ti Vessel to Large End-Group Flange**

- 1A. Perform electron beam tack weld on large end-group flange.

- Location and angle
- of electron beam
- weld. Tack in (4)
- places equally
- around flange.

## E-Beam Weld – Ti Vessel to Large End-Group Flange (Cont.) 

- 1B. Remove support rods.
- Add four additional equally
- spaced tack welds.
- 1C. Perform electron beam weld on large end-group flange.

- Spring
- Washer

- Remove support rods
- and perform 360 degree
- continuous weld.

## Ni55Ti conical end cap

**Ni55Ti conical end cap**

**Ti helium vessel**

- Weld
- Direction

## Helium Vessel to Cavity #3 Welding

**STEP 2:  EB weld titanium stepped end ring to small Ni55Ti conical end cap**
**	****A.  Seat stepped end ring on lip of small conical end cap.**
**	****B.  Add fixturing to apply sufficient pressure to end ring so as to maintain proper fit and alignment during tack welding.**
**	****C.  Tack weld in four places at 90 degree increments with E-beam vertical (parallel to cavity axis).**
**	****D.  Remove fixturing.  Add four additional tack welds**
**	****E.  Execute circumferential EB weld with E-beam vertical (parallel to cavity axis).**
**	****F.  Execute circumferential EB weld with E-beam perpendicular to the axis of cavity.**

## Fixture Setup for E-Beam Weld at Small End-Group Flange

- Add threaded rods and “Bottom Block” assembly.

## Fixture Setup for E-Beam Weld at Small End-Group Flange (Cont.)

**Fixture Setup for E-Beam Weld at Small End-Group Flange ****(Cont.)**

- 2A. Lower stepped flange end ring and seat on small end-group flange.

## Fixture Setup for E-Beam Weld at Small End-Group Flange (Cont.)

**Fixture Setup for E-Beam Weld at Small End-Group Flange**** ****(Cont.)**

- 2B. Add “Plunger Holder” and “Spring Plungers” to add pressure to stepped flange
- end ring to maintain proper
- fit and alignment during tack
- welding.

- Plunger Holder

- Spring Plungers.
- Each plunger provides
- 1.3 – 2.7 lbs. of down force.
- This is not enough load to
- de-tune the cavity.

## E-Beam Weld – Ti Vessel to Small End-Group Flange

**E-Beam Weld – Ti Vessel to Small End-Group Flange**

- Location and angle
- of electron beam
- weld. Tack in (4)
- places around flange
- between spring plungers

- 2C. Perform electron beam tack weld on small end-group flange.

## E-Beam Weld – Ti Vessel to Small End-Group Flange (Cont.)

**E-Beam Weld – Ti Vessel to Small End-Group Flange (Cont.)**

- 2D. Remove hardware.
- 2E & 2F. Perform electron beam welds on small end-group flange.

- Remove “Plunger Holder”
- and perform a 360 degree
- continuous weld.

## E-Beam Weld – Ti Vessel to Small End-Group Flange (Cont.)

**E-beam (primary)**

**E-beam**

**NbTi small conical end cap**

**Titanium spacer ring**

**Approximate location of original joint**

**E-Beam Weld – Ti Vessel to Small End-Group Flange**** (Cont.)**

## Helium Vessel to Cavity #3 Welding

**STEP 3:  TIG weld titanium stepped end ring to titanium helium vessel**
**	****A.  Based on estimated TIG weld shrinkage, adjust fixturing to deflect bellows such that after weld the bellows will assume a neutral position. (Unless shrinkage is too severe)**
**	****B.  Insert titanium filler ring in gap between stepped end ring and helium vessel.**
**	****C.  Install assembly in glove box and execute argon purge to desired level (< 20 ppm oxygen).**
**	****D.  Tack weld in multiple spots always trying to maintain uniform deflection around circumference.**
**	****E.  Complete TIG weld in segments with goal of  maintaining uniform deflection around circumference (possibly use additional titanium filler rod to increase weld integrity).**
**	****F.  Place multiple fillet welds in segments, working up towards a complete circumferential weld.**

## TIG Weld

**TIG Weld**

- Move to an argon purged glove box and perform final TIG weld of titanium stepped ring to titanium helium vessel. Weld to be performed in a “free” state.
- A filler ring is added to fill  the gap between the stepped ring and the helium vessel. The filler ring helps with alignment and supplies filler material to complete the weld.
- A fillet weld on top of the filler ring completes the assembly.

-  360 degree
- continuous
- TIG weld.

- Helium Vessel
-    (Titanium)

- Small End- Group Flange
-      (Ni/Ti)

- Filler Ring
- (Titanium)

- Stepped Flange
- End Ring
- (Titanium)

## TIG Weld (cont.)

- Small End-
- Group Flange

- Stepped Flange
- End Ring

- Helium Vessel

- Spacer / filler
- ring

- TIG fillet weld
- (0.062” dia rod)