Welding Aluminum vs. Steel — Tips to Improve Your Results
Welding Aluminum vs. Steel
Welding aluminum has many unique challenges being compared to welding steel.
Carbon steel is well-known for being more tolerant of certain activities, however it doesn’t mean that welding aluminum would be more complicated.
In many of the cases, welding aluminum needs special procedures to be welded. Important factors for welding aluminum include: choosing the correct filler metal, proper storage, and deep cleaning of base material along with proper welding techniques.
Common Characteristics of Aluminum which makes it different from steel during the welding process include: its chemistry, proper technique and reduction of hydrocarbons. The melting point of aluminum is 1,221 degrees Fahrenheit, compared to 2,500 Fahrenheit degrees for steel. It's clear that Aluminum has a lower melting point than steel. Aluminum possesses an oxide layer which melts at 3,700 degrees approximately. This oxide layer is a bit harder than the aluminum itself. This layer helps aluminum to resist abrasion and corrosion. It can act as an insulator while welding, hence it may cause some issues as well.
Challenges of Welding Aluminum
There are some challenges which may occur while welding aluminum. These are thermal conductivity and porosity issues. These two are the biggest variations in aluminum welding as compared to steel.
The soluble hydrogen in liquid aluminum will form bubbles which become trapped in the aluminum metal which leads to porosity.
Another challenge which was mentioned with aluminum welding is that it is five times extra thermally conductive compared to steel. Hence, due to this difference in thermal conductivity, aluminum metal needs much higher heat than steel while welding.
Some useful tips to improve welding aluminum
Selecting Right Filler Metal
It is very important to select right filler metal for aluminum, though it's a bit critical.
While selection the chart includes eight major characteristics which are very crucial, these Characteristics include: crack sensitivity, elevated temperature service, strength, color match after anodizing, ductility, post-weld heat treatment, toughness and corrosion resistance.
By understanding the mentioned characteristics, you may select the metal accordingly for best match, such as if 6061 aluminum is the base metal then good filler must include 4943, 5356 and 4043. It is to be mentioned that 4043 and 4943 GMAW (Gas Metal Arc Welding) wire or a gas tungsten rod can decrease chances of porosity and give weldability by increasing puddle fluidity. And a 5356 product gives great strength and toughness.
Do not weave
A common technique known as weave technique is used to weld steel, you should not use it with aluminum. Instead, for aluminum GMAW should be used for higher heat practice or use a stringer bead to ensure proper fusion and penetration.
Cleaning the metal
Cleaning the base material is very important before welding. It will remove oil, moisture, residue, and dirt. It will reduce the chance of porosity. An aluminum or acetone cleaner will work well to remove hydrocarbons on the surface of material. Do not blow them off with compressed air if shop instruments are being used, it may cause contamination from oils and moisture.
Removing The Oxide Layer
As highlighted above, aluminum has an oxide layer which causes issues in welding, so remove it with a stainless steel brush after cleaning.
Storing Properly
Sheets of aluminum metal should be stored inside. If you don't have a place inside, you may stand the sheets outside vertically instead of putting them on top of each other. It will prevent water from being trapped between the sheets.
Checking The Consumables.
When using GMAW, some issues may be caused with aluminum welding. Those issues can stem from the consumables. To reduce the risk of porosity, good quality gas hoses should be used. Those hoses should be connected tightly to not let any air pull into the line.
Monitoring The Temperatures.
You may take help from an aluminum filler metal guide to check interpass and preheating temperature ranges. Preheating is helpful for reducing the thermal effects, however you should keep in mind that preheating should be kept minimum for aluminum welding.
Conclusion
Starting from the chemistry of metal to the best practices for welding it, you should understand all the key concepts to have a perfect aluminum welding.
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