The best TIG rod for welding stainless steel is typically the ER308L. This filler rod is widely used for welding 304 and 304L stainless steels, which are among the most common stainless steel grades. The "L" in ER308L stands for "low carbon," which helps prevent carbide precipitation during the welding process, reducing the risk of intergranular corrosion.

For welding 316 and 316L stainless steels, the ER316L rod is recommended. It contains molybdenum, which enhances corrosion resistance, especially against chlorides and other industrial solvents.

If you're working with 309 stainless steel or need to weld stainless steel to carbon steel, the ER309L rod is suitable. It has a higher chromium and nickel content, providing a good balance of strength and corrosion resistance.

For high-temperature applications, the ER347 rod is often used. It contains niobium, which stabilizes the weld and prevents carbide precipitation at elevated temperatures.

When selecting a TIG rod, consider the specific stainless steel grade, the operating environment, and the desired mechanical properties. Always ensure the filler rod matches or exceeds the base metal's corrosion resistance and mechanical strength.

The size of the TIG rod for welding stainless steel depends on several factors, including the thickness of the material, the type of joint, and the welding position. Here are some general guidelines:

1. Material Thickness:

   • For thin materials (up to 1/16 inch or 1.6 mm), use a 1/16 inch (1.6 mm) rod.
   • For medium thickness (1/16 inch to 1/8 inch or 1.6 mm to 3.2 mm), use a 3/32 inch (2.4 mm) rod.
   • For thicker materials (over 1/8 inch or 3.2 mm), use a 1/8 inch (3.2 mm) rod.

2. Type of Joint:

   • For fillet welds or lap joints, a slightly larger rod may be beneficial to ensure adequate filler material.
   • For butt joints, match the rod size closely to the material thickness.

3. Welding Position:

   • In flat or horizontal positions, larger rods can be used comfortably.
   • For vertical or overhead positions, smaller rods are easier to control and reduce the risk of excessive heat input.

4. Welding Current:

   • Ensure the rod size is compatible with the amperage settings of your TIG welder. Larger rods require higher amperage.

5. Rod Material:

   • Use a rod that matches the base material. For most stainless steels, ER308L, ER309L, or ER316L rods are common choices.

6. Personal Preference and Skill Level:

   • Experienced welders may prefer different sizes based on their technique and comfort.

Always ensure the rod is clean and free from contaminants to prevent weld defects. Adjust your choice based on specific project requirements and test on scrap material if uncertain.

No, you should not use mild steel TIG rods on stainless steel. Using mild steel filler rods on stainless steel can lead to several issues, including corrosion, weakened welds, and compromised structural integrity. Stainless steel requires specific filler materials that match its corrosion-resistant properties. Using the correct stainless steel filler rod ensures that the weld maintains the desired mechanical properties and corrosion resistance.

To choose the right filler rod for stainless steel TIG welding, consider the following factors:

1. Base Metal Type: Match the filler rod to the base metal. Common stainless steels like 304 and 316 typically use ER308L and ER316L filler rods, respectively.

2. Corrosion Resistance: Ensure the filler rod provides equal or better corrosion resistance than the base metal. For example, ER316L offers better resistance in chloride environments compared to ER308L.

3. Mechanical Properties: Consider the mechanical properties required for the application, such as tensile strength and ductility. Choose a filler rod that meets or exceeds these requirements.

4. Weldability: Some filler rods are easier to weld with than others. ER308L is known for good weldability and is often used for general-purpose applications.

5. Service Conditions: Consider the operating environment, including temperature and exposure to chemicals. For high-temperature applications, a filler rod like ER309 or ER310 may be more suitable.

6. Compatibility: Ensure compatibility with the welding process and equipment. The filler rod should be suitable for TIG welding and match the electrode type.

7. Cost and Availability: Consider the cost and availability of the filler rod. Some specialized rods may be more expensive or harder to find.

8. Standards and Specifications: Adhere to industry standards and specifications, such as those from the American Welding Society (AWS), to ensure quality and compliance.

By evaluating these factors, you can select the appropriate filler rod for your specific stainless steel TIG welding application.

ER308 and ER316 TIG rods are both used for welding stainless steel, but they differ in composition and applications:

1. Composition:

   • ER308: Primarily used for welding 304 stainless steel. It contains approximately 19-21% chromium and 9-11% nickel. This composition provides good corrosion resistance and is suitable for general-purpose welding.
   • ER316: Used for welding 316 stainless steel. It contains 18-20% chromium, 11-14% nickel, and 2-3% molybdenum. The addition of molybdenum enhances corrosion resistance, especially against chlorides and other industrial chemicals.

2. Corrosion Resistance:

   • ER308: Offers good corrosion resistance but is less effective in environments with chlorides or marine conditions.
   • ER316: Superior corrosion resistance, particularly in chloride-rich environments, making it ideal for marine applications and chemical processing.

3. Applications:

   • ER308: Suitable for general stainless steel welding, including automotive, food processing, and architectural applications.
   • ER316: Preferred for more demanding environments, such as marine, chemical, and pharmaceutical industries, due to its enhanced resistance to pitting and crevice corrosion.

4. Mechanical Properties:

   • Both rods provide good mechanical properties, but ER316 offers slightly better performance in high-temperature and corrosive environments due to its composition.

5. Cost:

   • ER316: Generally more expensive than ER308 due to the addition of molybdenum and higher nickel content.

In summary, the choice between ER308 and ER316 depends on the specific requirements of the welding application, particularly concerning corrosion resistance and environmental conditions.

To prevent TIG weld contamination on stainless steel, follow these steps:

1. Material Preparation: Clean the stainless steel surface thoroughly to remove any dirt, oil, or oxide layers. Use a stainless steel wire brush or chemical cleaners specifically designed for stainless steel.

2. Use of Clean Tools: Ensure all tools, including brushes and grinders, are clean and dedicated to stainless steel to avoid cross-contamination from other metals.

3. Shielding Gas: Use high-purity argon or a mixture of argon with a small percentage of hydrogen or helium as the shielding gas. Ensure proper gas flow to protect the weld pool from atmospheric contamination.

4. Tungsten Electrode: Use a clean, properly ground tungsten electrode. Thoriated or ceriated tungsten is recommended for stainless steel. Avoid touching the tungsten to the workpiece to prevent contamination.

5. Filler Material: Use filler rods that match the base material in composition. Store filler rods in a clean, dry environment to prevent contamination.

6. Welding Environment: Weld in a clean, controlled environment to minimize exposure to contaminants. Avoid drafts that can disturb the shielding gas coverage.

7. Back Purging: For full penetration welds, use back purging with argon to protect the underside of the weld from oxidation.

8. Heat Control: Maintain appropriate heat input to prevent overheating, which can lead to oxidation and loss of corrosion resistance.

9. Post-Weld Cleaning: After welding, clean the weld area to remove any discoloration or oxide layers. Use pickling paste or passivation solutions to restore the stainless steel's corrosion resistance.

10. Inspection: Regularly inspect equipment and materials for signs of contamination or wear that could affect weld quality.

The recommended amperage for TIG welding stainless steel depends on several factors, including the thickness of the material, the type of joint, and the welding position. Generally, the amperage settings for TIG welding stainless steel can be estimated based on the material thickness:

1. Thin Materials (up to 1/16 inch or 1.6 mm): For thin stainless steel, a lower amperage range of 20 to 50 amps is typically recommended. This helps prevent burn-through and ensures a clean weld.

2. Medium Thickness (1/16 inch to 1/8 inch or 1.6 mm to 3.2 mm): For medium thickness stainless steel, an amperage range of 50 to 100 amps is suitable. This range provides adequate penetration and control over the weld pool.

3. Thicker Materials (over 1/8 inch or 3.2 mm): For thicker stainless steel, higher amperage settings ranging from 100 to 200 amps or more may be necessary to achieve proper penetration and fusion.

Additional considerations include:

• Electrode Size: The size of the tungsten electrode also influences the amperage setting. Smaller electrodes (e.g., 1/16 inch) are used with lower amperage, while larger electrodes (e.g., 3/32 inch or 1/8 inch) can handle higher amperage.

• Welding Position: Welding in different positions (e.g., flat, vertical, overhead) may require adjustments in amperage to maintain control over the weld pool.

• Joint Type: The type of joint (e.g., butt, lap, corner) can affect the amperage setting, as different joints may require different levels of penetration and heat input.

• Pulsing: Using a pulsed TIG setting can allow for better control over heat input, especially on thin materials, by alternating between high and low amperage.

Ultimately, the exact amperage setting should be determined through testing and adjustments based on the specific welding conditions and desired weld quality.