In welding dissimilar Al/Mg joint there is a tunnel exposed to surface (unfilled groove). What may be the cause?

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Febin Cherian John

If there is a tunnel exposed to the surface in a dissimilar Al/Mg joint, it may be due to several reasons, including:

Improper joint design: The groove geometry and dimensions may not be suitable for the specific Al/Mg alloys being welded, leading to incomplete filling of the groove and the formation of a tunnel. The joint design should be carefully considered to ensure proper fit-up and alignment, and the groove dimensions should be optimized for the specific welding process and material properties.

Insufficient heat input: If the welding process does not provide enough heat to melt and fuse the base metals and the filler material, the groove may not be completely filled, resulting in a tunnel. Increasing the heat input or adjusting the welding parameters may help to improve the weld penetration and fill the groove.

Incompatible filler material: The filler material used in the welding process may not be suitable for the Al/Mg alloys being welded, resulting in poor wetting and incomplete filling of the groove. The filler material should be carefully selected based on the material properties and compatibility with the base metals.

Contamination: The presence of contaminants such as oxide layers, grease, or other impurities on the base metals or filler material may interfere with the welding process and prevent complete filling of the groove. Proper cleaning and surface preparation techniques should be employed to minimize contamination and ensure good adhesion and bonding.

Overall, the formation of a tunnel in a dissimilar Al/Mg joint may be due to several factors related to joint design, welding parameters, filler material, and contamination. Careful consideration of these factors and proper selection and optimization of the welding process can help to minimize the formation of tunnels and improve the quality and integrity of the joint.

Raheem Al-Sabur

The presence of a tunnel or unfilled groove in a dissimilar Al/Mg weld joint can have multiple causes, including:

Inadequate welding parameters: The range of welding parameters used may not be suitable for dissimilar Al/Mg joints, resulting in incomplete fusion and the formation of an unfilled groove.

Poor fit-up: Improper fit-up between the Al and Mg materials can result in gaps or unfilled grooves, which can lead to the formation of a tunnel.

Oxidation: The presence of oxides on the surface of the materials can hinder the formation of a proper weld, resulting in the formation of an unfilled groove.

Regarding the excess material sticking on the tool during the plunge and dwell stages, this can be caused by several factors, including:

Excessive material feed rate: If the feed rate is too high, excess material can build up on the tool, leading to quality issues.

Tool wear: Worn or damaged tools may not be able to efficiently remove the material, leading to the buildup of excess material.

Inadequate cooling: If the tool is not adequately cooled, excess material may stick to it.

To address these issues, it may be necessary to adjust the welding parameters or improve fit-up between the materials. Additionally, cleaning the tool or using a new tool may be necessary to prevent excess material buildup.

Eyob Messele Sefene

The presence of a tunnel or unfilled groove in a dissimilar Al/Mg joint during welding can have several potential causes. Here are a few possibilities:

Inadequate joint preparation: If the joint surfaces were not properly cleaned, prepared, or shaped, it can result in an unfilled groove or tunnel. Welding requires clean and properly prepared surfaces to ensure good fusion between the two materials. Contamination, oxide layers, or uneven surfaces can prevent the filler material from flowing into the joint and filling the groove.

Insufficient heat input: Welding dissimilar metals like aluminum (Al) and magnesium (Mg) requires precise control of the welding parameters, including heat input. If the heat input is too low, it may not provide enough energy to fully melt the base metals and the filler material, resulting in inadequate penetration and an unfilled groove.

Mismatched filler material: The selection of an appropriate filler material is crucial in dissimilar metal welding. If the filler material chosen does not have good wetting properties or compatibility with both aluminum and magnesium, it may not flow properly into the joint, leaving an unfilled groove.

Incompatible welding technique: Different welding techniques, such as TIG (Tungsten Inert Gas) or MIG (Metal Inert Gas), have varying levels of control and heat input. If the chosen welding technique does not suit the specific characteristics of the Al/Mg joint, it can lead to incomplete fusion and an unfilled groove.

Joint design issues: The joint design plays a significant role in the success of welding dissimilar metals. If the joint design is not appropriate for the specific Al/Mg combination, it can result in an unfilled groove. Factors such as groove angle, root gap, and fit-up tolerance need to be carefully considered to ensure proper fusion.

It's important to note that without more specific information about the welding process and parameters used, it's challenging to pinpoint the exact cause of the unfilled groove. Consulting with a welding expert or metallurgist who can evaluate the specific conditions and examine the joint would be beneficial for a more accurate analysis.