One of the most frequent decisions made in the field is: should we weld this crack? The answer varies with the part, the material and the crack's cause. A weld placed in the wrong spot not only fails to solve the problem, it can invisibly grow the damage.
The Safe Repair Zone
Damage in non-structural areas — steps, mudguard mounts, secondary brackets — can be safely repaired with an appropriate method. In main load-bearing members such as chassis rails, however, other rules come into play: high-strength steels are sensitive to heat input; uncontrolled welding lowers the strength of material around the crack and carries the damage to the neighbouring zone. Repairs in these zones must be done with weld-prep matching the manufacturer's repair procedure, the correct filler material, and, if required, a reinforcement plate.
Risky Situations
- A crack whose cause is not understood: If a fatigue crack is simply welded shut, it returns at the same spot or right beside it
- Tanker bodies: Welding on a tank that has carried a flammable product, without gas-freeing first, means an explosion risk; this job is done only at authorised facilities
- Axle and brake area: Welding onto an axle body must never be applied without manufacturer approval
- Uncertified workmanship: Repairs on load-bearing structure require a certified welder versed in the procedure
The rule is simple: a repair is not designed until the root of the crack is found, and no weld is made on load-bearing structure without the manufacturer's procedure. Consulting the manufacturer in every doubtful case is worth more than the fastest fix — because getting the repair right the first time is always cheaper than a repeated repair.