Weld Types – Butt Joint with Backing

Butt Joint with Backing A Butt Joint with Backing is the basis for many automotive structural sectioning welds. UVU CRT 2009

Butt Joint With Backing Example Rail ready for welding. Right and left rail section with plug holes and center insert. UVU CRT 2009

Butt Weld with Backing You should now have an understanding of what a butt joint weld is and where it is used. The next step is to tune the welder and perform a butt weld that will be evaluated visually and destructively. UVU CRT 2009

Butt Joint with Backing Joins two pieces of closely butted metal with a backing piece. Requires a Root gap of 3 metal thicknesses. Too small of a root gap will limit penetration. UVU CRT 2009

Fit Up and Clamping Root Gap Two Top Pieces Backing is out of the same metal UVU CRT 2009

Butt Joint with Backing Set two coupons on top of the backing Set the proper root gap Mark 1” to 1.5” in the center Secure coupons for weld 1” to 1.5” Root Gap 3x metal thickness UVU CRT 2009

Gun Position The proper gun to work piece for a butt joint with backing is 90 degrees to the surface. 90 90 UVU CRT 2009

Tune the Welder Make sure to “Tune the Welder” by making practice welds on the same material that will be used for the final weld. Make the necessary voltage and wire speed adjustments and check for proper penetration before beginning the final weld. UVU CRT 2009

Lab Assignment Print off the Butt Weld “Task Performance Sheet”. Set up and tune the welder. Set up and mark the coupons for the weld. Perform the Butt with Backing Weld. Visually inspect the weld. Destructively test the weld. UVU CRT 2009

Check for penetration on back of coupons Visual Inspection Length = 1” to 1.5” Melt Through = 1/16” max. Bead width = 3/16” to 3/8” Height = 0” to 1/8” Check for penetration on back of coupons UVU CRT 2009

Using I-Car’s WQT Gauge I-Car has provided a gauge to help in visually inspecting welds for: bead length width height penetration defects UVU CRT 2009

Using gauge to check: Bead length Bead Height UVU CRT 2009

Gauge also checks: Weld Penetration UVU CRT 2009

Record The Results After the visual inspection is complete record the results on the task performance sheet and have the instructor verify your results. Now the destructive test will need to be performed. UVU CRT 2009

Destructive Weld Test Bend the top pieces toward each other. Clamp in Vise. Chisel off backing piece. There should be continuous fusion on all three pieces. UVU CRT 2009

Notice the torn section – This is a sign of a good weld Destructive Test Notice the torn section – This is a sign of a good weld UVU CRT 2009

Final Weld When the welds pass the visual and destructive test observe the final voltage and wire speed setting. Record the destructive test results on the task performance sheet. Complete your final weld series in the flat vertical and overhead position. Turn these in for grading. UVU CRT 2009

References Miller Electric Mfg. Co. Education. http://www.millerwelds.com/education/library.html, 2006. Lincoln Electric Co. Lincoln Welders. http://www.lincolnelectric.com/, 2006. Inter Industry Conference on Automotive Collision Repair. I-CAR Online Training. http://www.i-car.com/, 2006. UVU CRT 2009