How to improve TIG welding by choosing the right filler material

TIG (Tungsten Inert Gas) welding is an arc welding process that uses a tungsten electrode to produce the welding arc and inert gas, usually argon, to protect the work area from oxidation and contamination. One of the key aspects in achieving high-quality TIG welding is the selection of the correct filler material. This article will examine the different types of filler materials and their specific applications, in order to help you choose the most suitable one for your project.

Factors to consider when choosing the input material

Before delving into the details of the various types of filler material available on the market, it is essential to understand the main factors to consider when choosing the right filler material for your project:

•  Chemical compatibility: the filler material must be compatible with the base metals to be welded together.
•  Mechanical properties: The filler material must have mechanical properties similar to those of the parts to be welded to ensure strength and durability.
•  Heat tolerance: the filler material must have sufficient heat resistance to withstand the high temperatures of TIG welding without degrading or triggering unwanted reactions.
•  Ease of welding: the filler material must be easy to work with, with a stable arc and good wetting and melting characteristics.
•  Costs: Finally, it is also important to consider the price-performance ratio of the chosen filler material.

With these factors in mind, let's look at the main types of filler materials used in TIG welding and their specific applications.

Filler material for carbon and low-alloy steels

Carbon rods (ER70S-xxx)

This type of filler material is very common in TIG welding of carbon and low-alloy steels, mainly due to its versatility. ER70S are available in different classes, depending on the welding requirements. For example, ER70S-6 is suitable for welding slightly oxidised steels due to the presence of silicon and manganese, which improve arc wetting and crater solidification.

Low alloy steel rods (ER80S-xxx, ER90S-xxx)

For welding low-alloy steels with high mechanical strength, specific filler bars such as ER80S or ER90S are most suitable. These bars include alloying elements such as chromium, molybdenum and vanadium, which impart superior mechanical properties to the welds. They are suitable for structural applications, such as bridges, cranes and lifting equipment, where higher fatigue and impact resistance is required.

Stainless steel filler material

Austenitic stainless steel material (ER308L, ER316L, ER347)

For TIG welding of austenitic stainless steels, specialised stainless steel filler materials such as ER308L (for AISI 304), ER316L (for AISI 316) and ER347 (for AISI 321) are mainly used. These filler materials contain low percentages of carbon to reduce the risk of carbide formation and prevent intergranular corrosion. In addition, the addition of elements such as chromium, nickel and molybdenum improves the corrosion and high temperature resistance of the welds.

Ferritic material for stainless steel (ER430, ER410)

In the case of ferritic stainless steels, such as AISI 430 or AISI 409, specific materials such as ER430 or ER410 can be used. However, care must be taken with the selection of shielding gas and the settings of the welding machine to avoid localised overheating that could cause brittle martensitic structures to form in the weld.

Aluminium filler material

Silicon material for aluminium alloys (ER4043, ER4047)

For TIG welding of aluminium alloys, the most common filler materials are silicon-based rods, such as ER4043 and ER4047. They have good compatibility with pure aluminium alloys and those with higher silicon concentrations. Due to their low melting temperature and short solidification interval, these materials reduce the risk of hot cracking and improve the wettability of the arc and fluidity of the molten metal.

Magnesium material for aluminium alloys (ER5356)

The filler material ER5356 containing magnesium is suitable for TIG welding of aluminium alloys with high mechanical strength, such as AISI 5083 or AISI 6061. This material provides better corrosion and fatigue resistance than ER4043.

Filling material for titanium

Pure Commercial Titanium (CP) and Alpha/Beta Titanium Alloys (ERTi-x)

For TIG welding of titanium and its alloys, specific filler materials called ERTi are used, which are classified according to their chemical composition and mechanical properties. For example, pure commercial titanium (CP) can be welded with ERTi-1, while alpha-beta alloys, such as aluminium-vanadium, can use ERTi-5. It is critical to carefully select the filler material and follow recommended practices for cleaning and gas protection during TIG welding of titanium to avoid surface contamination and weld fragility.

In conclusion, the choice of the appropriate filler material is an important step in successful TIG welding. By knowing the characteristics of the different types of filler material available and their specific applications, you can significantly improve the quality of your welds and ensure the durability and reliability of your project.