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3 Differences Between Welding Aluminum and Welding Steel

Industrial welding automotive
Welding is one of the most widely used methods of joining two or more pieces of metal together in a permanent fashion. Historically, the welding industry came into being as a way to fabricate machinery out of steel. Yet in the last 50 years, aluminum has come to take a larger and larger place in the manufacturing, automotive, and aerospace industries.

Steel and aluminum couldn't be more different as far as metals go - a fact that makes them behave much differently during welding. An understanding of these differences is key to obtaining the desired results. This article, then, will provide a useful outline of three of the most important distinctions between welding aluminum and welding steel.

1 - Aluminum Boasts Higher Conductivity

As you probably already know, aluminum has a much lighter weight and density than steel. Nonetheless, it possesses a thermal conductivity approximately five times greater than that of steel. As a result, heat has a much easier time moving through aluminum than it does through steel. This simple fact has quite a lot of ramifications when dealing with welding.

For one thing, it means that aluminum welds will solidify at a much quicker rate than steel welds. This solidification rate presents a particular challenge for welders, who must be experienced enough to lay down a neat and even weld the first time. If not applied carefully, the aluminum near the weld site may also suffer from distortion.

This distortion stems from the fact that, despite its high conductivity, aluminum has a melting point around 1400 degrees Fahrenheit less than that of steel. Nonetheless, high temperatures must be used in order to overcome the metal's conductivity. Less experienced welders often struggle to negotiate the balance between these two factors.

2 - Molten Aluminum Is Harder to See

When working with steel, experienced welders can often tell the progress of a weld by the color of the metal. As the temperature of steel increases and it begins to melt, it takes on a silvery appearance quite distinct from that of unmelted steel. This color change makes it easy for the welder to judge how far along the weld has come.

Unfortunately, assessing the progress of a weld in this manner grows difficult when working with aluminum. Solid aluminum and molten aluminum do not present as distinct of a color or appearance difference. This subtlety increases the risk of a welder overapplying their heat source - and thus ending up with a puddle of molten metal on the ground.

3 - Aluminum Requires More Involved Pre-Treatment

All types of metal require pre-treatment before welding them. The pre-treatment process promotes a cleaner and stronger weld by removing dirt and other surface impurities. To pre-treat steel, workers will use sandpaper or chemicals to remove any grime, rust, or other impurities. The edges of the weld area may also be cleaned using a grinder.

The pre-treatment of steel can be accomplished relatively quickly and easily. Those who omit pre-treatment may even be lucky enough to still end up with good results. Aluminum, however, can be much less forgiving. Those who skip pre-treatment when working with aluminum often end up with welds that will fail under stress. 

Pre-treating aluminum involves more steps than pre-treating steel. In addition to removing any oil, grease, or dirt, workers must also eliminate any oxides on the surface of the aluminum. Degreasers and other chemical substances must be used to thoroughly clean the aluminum. Then workers must carefully buff the surface with stainless steel wire brushes to remove any oxides that may be present.

Welding Experts

Every welding metal responds in a slightly different way. But with the right combination of knowledge and experience, a welder can achieve good results with virtually any metal. Reach out to the professionals at Wilson's Welding Service, Inc. if you would like to learn more about what it takes to achieve excellent welding results.