Weld Types - Lap Weld UVU CRT 2009

Lap Weld  Many automotive structural panels are assembled using a lap joint.  Technicians must make test welds visually inspect destructively test “before welding on the vehicle” UVU CRT 2009

Lap Weld Example These are the crimping tools. Notice the offset jaws One side of the rail is crimped to fit flush inside the other. Relief cuts are also made at the seams. UVU CRT 2009

Lap Weld Fit Up The crimp allows the panels to fit flush. This is the backside of the rail showing the overlap. UVU CRT 2009

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

Lap Weld – In Class Assignment  Joins two pieces of overlapped metal  Used for sectioning rails and pillars  Always follow manufacturers recommendation UVU CRT 2009

Getting Ready to Weld  Set one 3”x5” coupon on top of the other.  Overlap ½ way.  Mark 1” to 1.5” in the center of the coupon.  The crimp is not necessary on these coupons. 1” to 1.5” Overlap ½ way UVU CRT 2009

Gun Position  The proper gun to work piece angle for a lap joint is 70 degrees off the surface.  Angle the wire into the top piece 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 Lap Weld “Task Performance Sheet”  Set up and tune the welder.  Set up and mark the coupons for the weld.  Perform the Lap Weld.  Visually inspect the weld.  Destructively test the weld. UVU CRT 2009

Visual Inspection Length = 1” to 1.5” Bead width = 3/16” to 3/8” Height = 0” to 1/8” Check for penetration on back of coupons Melt Through = 1/16” max. 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 I-Car’s WQT Gauge Weld Bead LengthWeld Bead Width UVU CRT 2009

Lap Weld Visual 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  Secure bottom coupon in vise.  Bend top piece back and forth until the coupons separate.  The metal should break along the length of the weld. UVU CRT 2009

Destructive Test Notice the torn section – This is a sign of a good weld The weld is good if the metal breaks off from the top piece. Metal from top piece UVU CRT 2009

Weld  When the welds pass the visual and destructive test observe the final voltage and wire speed setting.  Have the instructor check off your task performance sheet.  Complete your final weld series in the flat vertical and overhead position.  Turn these in for final grading. UVU CRT 2009

References  Miller Electric Mfg. Co. Education  Lincoln Electric Co. Lincoln Welders  Inter Industry Conference on Automotive Collision Repair. I-CAR Online Training UVU CRT 2009