I am welding carbon steel coiled tubing, one of the test we run is tensile strenth. The tubing is 1.75 OD and 0.109 thick. Our proceedure calls for the use of chill blocks, 100% argon and ER70S-6 filler wire. The amperage range is 70 to 90 amps. A max interpass temp. of 135 degree's. I keep falling just shy of the required tensile strenth requirments. Any suggestions.