Here are three TIG welds to compare. The first is properly laid with the right amount of shielding gas and amperage. The second illustrates too much amperage (note the flat, molten look). The last shows too much amperage and too little shielding gas. Only the first weld would be considered strong. Also, when welding a T-joint like this the edge will melt faster, so angle the torch slightly away to direct more heat to the flat surface and dab the filler rod where the edge is melting.