<VV> Re: Aluminum Head Weld repairs

[Garth Stapon]

Brad:

This is a tough one and will require preheat of 700 degrees to counteract the heat conductivity of the base metal. Buy a tempil stick from your local welding distributor.

Put the head into an oven or use an oxy fuel torch set in a carburizing condition. The house will fill with the smell of burnt oil, so make sure you wife is out. If you can only get it to 500 F that will be ok, it will just require a little longer arc time to melt the base material. The secret to success on this repair is preheat!

Prior to welding or preheating, clean the material as well as possible. Acetone works well.

Use AC current with pure tungsten electrode or zirconium alloyed tungsten electrode 3/32 " diameter.

Use a the largest possible gas cup that still allows access to the joint. If a gas lens is available use that as well.

Set the panel at 150 amps and use the remote foot control.

Set gas flow at 20 cfh.

Set high frequency on continuous. If wave form control is available set to maximum cleaning as this will help remove oil.

Use a dremel tool to remove porosity. It will likely take three passes to put down solid weld metal due to oil impregnation in the aluminum.  Grind between passes.

Use 3/32 " grade 4043 filler metal as its composition is closer to matching the base metal than 5356. Wipe the aluminum rod with a clean acetone rod prior to welding. 3M scotch pad also works well. (Removal of the oxide layer on the electrode just prior to welding will help.)

4047 is also an effective substitute.

Add lots of amperage to melt the material initially, but once it becomes fluid throttle back the current just to the point where you maintain a weld puddle.  High current levels should not be required for any longer than 3-5 seconds. If preheat is not used, this repair becomes much more difficult!

This repair requires remote amperage control. A hand or foot control is essential.

Build up to 1/4 inch above the normal surface and machine as required.

I hope this help.

Regards, Garth

  ----- Original Message ----- 
  From: Brad Hall 
  To: stapon1 at earthlink.net 
  Sent: Saturday, August 27, 2005 7:01 AM
  Subject: Weld repairs


  Hi Garth,
  While you're on the subject of weld repair, could you describe a weld repair process for Corvair head valve seat repair, ie. welding process to build the seat area back up prior to machining for new valve seat inserts?  Yes, I do have a TIG welder. 
   Thanks.

  Brad Hall - still here in Ontario.