General Information On Repair Of Vehicles With Ultra-Strength Steels - Ah60.00-P-0024-01N
Model 117, 118, 156, 166, 167, 176, 177, 190, 197, 204, 205, 207, 212, 213, 216, 217, 218, 221, 222, 223, 231, 238, 242, 243, 246, 247, 253, 257, 290, 292, 293
Model 453
Model 463
as of model year 2019
Failure to observe instructions when straightening/repairing, separating, preparing adhesive points, joining/connecting, resistance spot welding and MIG soldering can lead to considerable damage to ultra-strength steels and their joints.
Straightening/repairing ultra-high-strength steels
Planishing and straightening work:
- Input of heat above 300°C is not permissible.
- Use a commercially available pulling tool for dent removal on, e.g. the side longitudinal member. Observe the suitability for resistance welding when installing the pulling adapter (e.g. shims) on ultra high-strength steels.
- Straightening work on ultra high-strength steels can only be accomplished in the event of minor damage (dents).
Cutting ultra-high-strength steels
Warming up of bonding points:
- The maximum permissible temperature for heating up the flange connection to be loosened is 200°C.
- The ideal temperature for loosening the flange, e.g. with a chisel, is approx. 100 to 120°C.
- Do not exceed the maximum heat-up temperature of 200°C for an adhesively bonded connection consisting of 3 sheets of metal to maintain its undissolved connection without permanent damage.
- After the component has cooled down, the adhesive resumes its original strength.
- A heat gun is recommended as a heat source.
- Drill out spot welds using special drill bits.
- Mill off spot welds using special spot weld milling cutters.
- Cut using special cutting disks 0 30 mm.
- Use suitable machines for the individual tools.
- Drill rivet holes using special drill bits.
Prepare gluing points
The detailed work description included with glue set must be strictly observed.
Otherwise adhesion problems may occur.
Observe pretreatment of bonding surfaces.
Joining/connecting ultra-high-strength steels
Rivet joints:
- When processing ultra-high-strength materials, only high-strength rivets approved by Daimler AG may be used.
- A riveter with increased draw-off strength is required for this purpose.
Resistance spot welding
The following points must be observed in order to form an optimum weld joint:
- The spot welding tongs to be used (inverter technology) must be approved for these materials.
- The extension of the electrode arms is limited to the short standard electrode.
- To determine the optimum welding parameter settings and the electrode pressure, perform a snap-out test on a sample plate before performing resistance spot welding on the vehicle (see following picture).
- Only this ensures optimum welds.
MIG soldering
MIG soldering is only permissible at repair points described in the Service Information.
Snap-out test on sample panel (old part) on ultra high-strength steels to determine the optimal welding parameter setting
- Determine suitable welding parameters on sample panel (to be removed from old part) in combination with approved spot welders. By completing a spot-weld specimen (with adhesive) and a snap-out test with measurement of the weld nugget diameter using the formula 4x√t (t = panel thickness).
- The weld nugget dia. (a) should be at least 5 mm
The adhesive should be removed from an adhesive cartridge without mixing tube (mixed by hand).