Cracked Boom Welding Tips

The boom and stick on your excavator, backhoe, or other machine with those components take a ton of pounding.  Pun was kind of intended there.  Eventually these pieces will fail.  It starts with a small crack and quickly grows.  Getting a new or used boom or stick isn't cheap so welding the crack is a good option if done right.

The requirements for welding mild steel works for other types of steels.  A welder will usually use an E7018 electrode, however, for higher strength steels, this rod may not provide filler metal strong enough to sustain the required stress.

Here are a few tips to help make sure the welding goes right the first time to help prevent having to re-weld the stick or boom all over again.

  1. Be sure to obtain the proper weld procedures from the manufacturer or someone with experience in welding.
  2. If you're not confident in doing the work yourself, hire a certified welder.  This could save you time and money in the long run.
  3. Be sure the electrodes are clean, and in good condition. For steels having yield strengths in excess of 100 ksi (690 MPa), the electrodes must be baked in an oven at temperatures between 700 – 800 F (370 – 425 C) for at least one hour before being used.  After baking, the electrodes should be kept in a storage oven at 250 F (120 C) until needed.
  4. Weld with small electrodes using stringer beads instead of using a weaving technique. This limits the heat input into the metal which allows the steel to achieve its full strength. A weaving technique could cause reduced strength as well as re-cracking.
  5. Prepare the area for welding by cleaning any paint, oil, rust or other debris.
  6. Remove the crack and check it with magnetic particle or liquid penetrant testing as you won't be able to see the extended crack beneath the surface.
  7. Be aware of the pre-heat and post heat requirements. The material should be evenly heated to the pre-heat temperature through its thickness for three inches (75 mm) to either side of the repair. Preheating to an excessively high temperature can temper the steel reducing its strength.  The temperature should be monitored using temperature indicating crayons on the back side of the joint.
  8. Do not weld in a drafty location, especially when the temperature outside is cold.  Drafts quench the weld metal too quickly, resulting in re-cracking either immediately after welding or a few days later.
  9. Wait at least a couple days before examining the final weld using magnetic particle inspection.  This is because hydrogen cracking occurs once the weld has cooled.

Depending on your time and budget, it could make more sense to get a used or new aftermarket boom or stick for your machine.  ConEquip Parts has both for most makes and models.

We came across this video on YouTube.  This may give you an idea of what is involved in the welding process.

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