Method of welding stainless steel lined pipe

Welding stainless steel lined pipe involves a few steps that require careful attention to ensure a quality seal. Here’s a general method for welding these types of pipes:

Materia ls Needed:

1. Welding machine (TIG or MIG typically for stainless steel)
2. Stainless steel filler material
3. Welding mask and gloves
4. Wire brush or grinder
5. Welding Gas (Argon for TIG, a mix of Argon and CO2 for MIG)

Procedure:

1. Preparation:

• Pipe Cleaning – The most important step before you start welding is to clean the pipe thoroughly. You can use a wire brush or a grinder to remove any rust, scale, or other contaminants present on the surface of the pipe.

• Pipe Alignment – After cleaning, align the pipes correctly. The pipes should be flush against each other to create a seamless joint. Use clamps if necessary to hold the pipes in place.

• Setting up the Welding Machine – Depending on the thickness of your pipe, set the appropriate power and wire speed (for MIG) or amperage (for TIG) on your welding machine.

2. Tack Welding:

• Begin by tack welding at several points around the pipe joint. This will hold the pipes together and prevent warping during the main welding process.

3. Main Welding:

• Root Pass – The first weld pass is usually the root pass, which is made along the pipe joint. For stainless steel, a common method is to use a backing gas, such as argon, to shield the back side of the weld from oxidation. This is especially important for stainless steel, which can form chromium oxides if exposed to the atmosphere while hot.

• Filler Passes – After the root pass, additional filler passes may be necessary to fully fill the joint. The number of passes will depend on the thickness of the pipe and the desired strength of the joint.

• Cap Pass – The final pass is the cap pass, which should smooth out the weld and ensure a uniform surface.

4. Post-Weld Cleaning:

• After you finish welding, it’s important to clean the weld area again to remove any slag or oxidation. This can be done with a wire brush or a grinder.

• Additionally, you may need to perform post-weld heat treatment, depending on the type of stainless steel and the specific application..

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Remember, safety should be the utmost priority while welding. Always wear appropriate personal protective equipment, including a welding helmet, gloves, and protective clothing.

Also, note that this method is a general procedure and may vary based on the specific type of stainless steel, pipe dimensions, and other factors. Always consider consulting a professional or refer to the specific welding procedure specification (WPS) for your particular application.