Best preparation practices for welding 4130.

August 30, 2018 @ 4:08:pm

Photo of Best preparation practices for welding 4130.

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Best preparation practices for welding 4130.

Though it is not very common in the auto racing industry it is always best practice to remove the decarb or oxide layer from your 4130 around weld area.

What is the decarb layer?

The decarb layer on 4130 is a type of mill scales that forms during the heat-treating process. While in the blast furnaces the carbon molecules to rise to the surface and mix with the oxygen in the air causing oxidation on the surface of the material. This is also common on Mild Steel DOM tubes as well. This decarb layer can vary in thickness based on allowable specifications of materials. Typically, 4130 has a minimal to zero measurable decarb. With that said, it is best to clean / remove this layer.

Why is it best practice to remove the decarb layer?

If the decarb layer is not removed the weld can be contaminated. Failure to remove the decarb layer will result in floaties in the weld puddle. You also increase the chances of undercutting the weld. This is more prevalent when the decarb layer is heavier. Removing the decarb layer will also allow the metal to wet out quicker.

How do you remove the decarb layer?

You should use a scotch brite pad, wire brush or other abrasive to remove the black or dark decarb layer at least 1” back from the weld. The material then should be wiped down with an acetone or other solvent, like Solvent 200, to remove all grease and oils that may contaminate the weld. Make sure to where nitrile gloves as the natural oils from your fingers can also contaminate the weld.

The above is recommended for a high quality and safe component. As in most projects. The better the preparation, the better the end product.