Repair Of Vehicles With Ultra-Strength Steels General Information - Ah60.00-P-0024-01N
Model 117, 118, 156, 166, 167, 176, 177, 190, 197, 204, 205, 206, 207, 212, 213, 214, 216, 217, 218, 221, 222, 223, 231, 232, 236, 238, 242, 243, 246, 247, 253, 254, 257, 290, 292, 293, 294, 295, 296, 297
Model 453
Model 463
as of model year 2019
Model 464
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:
- Do not heat above 300°C.
- A commercially available pulling tool is required to planish, e.g. the side longitudinal member. Observe suitability for resistance welding when installing the pulling adapter (e.g. washers) 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 the flange connection to be released is 200 C.
- The ideal temperature for releasing the flange, e.g. using a chisel, is approx. 100 to 120 C.
- To preserve 3-sheet adhesive bonding without permanent damage, the maximum heating temperature should not exceed 200°C.
- 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, use only high-strength rivets approved by Mercedes-Benz AG.
- 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 electrode arm (inverter technology) to be used 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 Workshop Information System (WIS).
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 fabricating a weld specimen (with adhesive) and conducting a snap-out test with measurement of the weld nugget diameter using the formula 4x√t (t = panel thickness).
- The weld nugget diameter (a) should be at least 5 mm.
The adhesive should be removed from an adhesive cartridge without mixing tube (mixed by hand).