Tig Magnesium???? Help

[JWELD]

I am having great difficulty Tig welding auto transmission cases. As soon as a puddle starts to form I get "immediate" burn through. Is it the magnesium content????
I know in order to answer this you need to know all the particulars, however give me some ideas concerning "crack repair".
I do a lot of transmission work so this is critical.

Alao thanks for all inpuit regarding my Synchro 250. Have decided to advance with that machine instead of opting for Dyanasty, for the moment.

[HAWK]

JWELD,

Help us out: case thickness is approximately 5/32" ??
type and diameter of tungsten -try pure or thoriated
tungsten end is balled or pointed balled is preferred
but a slight point may better point the arc-try both
amperage setting-try 1 amp per .001" thickness
balance setting go more toward the positive side
preheat on case 250-300 degress may help-see below

Crack repair: If possible: "V" the crack with a carbide grinding bit on a die grinder rather than a angle grinder wheel to minimize contamination ; drill tiny holes-one at each end of crack to keep spreading to a minimum ; small amount of preheat 300 degrees is plenty-use a temp pencil to check it-this will minimize arc heat absorption in a single spot & possibly burn some contaminants out ; weld in sections-one end for 1/2' , the other end 1/2', then the middle-fill in the spaces. Does your machine have the pulser option? You should not need it, but it may help to agitate the puddle to clean surface as you weld. That is more of an inverter welding trick with the Dynasty-Don't lean too heavy on that one.

[imported_Blackplague]

Trans cases are pretty poor castings.

sometimes i think they are just casted out of recycled beer cans. You and i have transmissions in common. Make absolutely sure the case is clean where your going to be welding. Case oxidation melts at around 3000 deg, where the case starts melting around 1300 deg. Follow Hawks recommendations on the crack. Set your balance to #3 or #4 {you want more cleaning action, because trans cases are Dirty}. Be quick, once the puddle starts forming start adding and keep it moving fast. I wouldn't think you would need more than 175 amps.