Welding Stainless Steel and Aluminum Together: Techniques and Setup

Welding stainless steel and aluminum together may seem like an impossible task due to their different material properties. However, with the right techniques and equipment, it is indeed possible. This article will guide you through the process including the necessary equipment, setup, and welding techniques.

Introduction to Dissimilar Metal Welding

Welding stainless steel and aluminum together is often referred to as dissimilar metal welding. Dissimilar metals have different thermal properties and chemical compositions, making this type of welding more challenging. However, the specific combination of metals (stainless steel and aluminum) can be welded successfully using a TIG (Tungsten Inert Gas) welder, although it requires careful preparation and suitable parameters.

Equipment and Materials Needed

TIG Welder: Ensure your welder is capable of AC (Alternating Current) and DC (Direct Current) settings. Tungsten Electrode: Use a 2 lanthanated tungsten electrode for both metals. Filler Rods: Use filler rods designed for each metal: 4047 or 4045 for aluminum, and ER308L for stainless steel. A hybrid filler rod such as ER309L is also suitable for welding dissimilar metals. Shielding Gas: Use pure argon for aluminum and a mix of 75% argon and 25% helium for stainless steel.

Cleaning the Metals

Proper cleaning is essential for successful welding. Both stainless steel and aluminum surfaces must be free from oxidation, oil, and other contaminants. This step helps in achieving a strong and durable weld.

Setup for Welding

Polarity Settings

Stainless Steel:

Set the welder to DCEN (Direct Current Electrode Negative).

Aluminum:

Set the welder to AC (Alternating Current).

Additionally, you can use AC for the aluminum side and DCEN for the stainless steel side, but this setup may depend on the specific thickness and type of metals.

Tungsten Preparation

Sharpen the tungsten electrode to a point to enhance arc stability. A larger taper may be necessary for thicker materials.

Gas Flow Rate

Set the shielding gas flow rate between 15-20 cubic feet per hour (CFH). Adjust as needed based on the welding environment.

Amperage Settings

For aluminum, typically set the amperage at 1 amp per 0.001 inch of thickness.

For stainless steel, adjust similarly but ensure you have enough heat to penetrate both materials.

Weaving vs. Linear Technique

Cavone's weaving technique is often recommended for dissimilar metal welding. Start by creating a puddle on the aluminum side, then introduce the filler rod while moving towards the stainless steel side. Maintain a consistent arc length and angle to ensure a smooth blend.

Tack Welding

Begin with tack welds to hold the pieces together securely before performing the main weld.

Post-Weld Treatment

After welding, clean the joint and inspect for any defects. Grinding or polishing may be necessary to achieve the desired finish.

Considerations and Challenges

Thermal Expansion: Be aware of the differing thermal expansion rates, which can lead to warping or cracking. Weld Strength: The joint may not have the same strength characteristics as a weld between similar metals. Consider the application and load requirements. Testing: If the joint is critical, test the weld for integrity and strength.

Welding dissimilar metals like stainless steel and aluminum can be challenging. Practice and experience will help improve your technique, but with careful preparation and the right tools, it is possible to achieve strong and durable welds.