Would you know what to do if you are asked how to choose the right filler rod to get the job done? In this post about a practical guide to filler rod selection for welding I have outlined some basic requirements that will help you in your day to day work.
Table of contents
- The Basics
- How to find the Electrode or Filler Metal for a Base Material
- My Conclusion:
Okay, let’s say you are serious about up-skilling your knowledge, or you are keen to understand as much as you can about filler rod selection for welding in practical application.
The article in brief summarizes one of the procedures on how to select the filler rods (coated or non-coated) in general for welding procedures and / or production welds.
Hopefully, you are through with the Mandatory Classification Designators, and the Optional Supplementary Designators – the Classification of Filler wires.
The correct metal is needed for the strength, longevity and integrity of the welds.
In other words, an experienced welder, technician or welding engineer will know the classifications of metal needed for a particular application. Certainly, will use them in combination with other welding techniques to produce a strong, defect-free Weld.
Before we begin, ensure that some of the basic factors for filler rod selection are taken into consideration, like, what is:
- The Tensile Strength & Elongation Rating of the Base Metal
- Positions you will be welding
- The Required Regulatory Codes and Specifications
- The Required Joint Design
- The Welding Equipment and its Capacity (Amps)
Once you are done with the above criteria for selection of welding rods, the next step is to determine the right filler metal for the job.
How to find the Electrode or Filler Metal for a Base Material
I hope to elaborate a bit easier here. However, there are posts on practical consumable electrode selection and electrode classifications that you may visit for additional references.
For instance, you want to find the filler wire for a base material, say, SA 335. Also, you have concluded the welding will be a GTAW process by assessing the general criteria for filler selection.
ASME Section IX, Table QW-422
Therefore, the next step would be to refer ASME Section IX, Table QW-422.
This table enlists the Ferrous / non-Ferrous P-numbers, their grouping, the Unified Numbering System (UNS) composition-based system of commercial materials, and the chemical composition for the base metals for qualifications.
In short, P numbers are groupings of base materials with relevant welding characteristics that have been approved for certain pressure boundaries. Moreover, sub-groupings within a P number are group numbers.
As a result, knowing the P-No. helps in identification of base metal for qualification of an entire selection versus qualification of just one.
Chemical composition identifies what are the elements that make up the material. The nominal chemical composition of material, typically the midpoint of the allowed range, too plays a vital role in the filler metal selection criteria.
ASME Sec II Part C or ANSI/AWS A5A
After that, based on our criteria and the table QW-422, refer ASME Sec II Part C or ANSI/AWS A5A (Specification for Welding Rods and Filler Wires). After that, SFA5.28/SFA5.28M Low Alloy Steel Electrodes and Rods for Gas Shielded Arc Welding.
Table 6 – Base metal for Test Assemblies
Subsequently, refer Table 6 – Base metal for Test Assemblies that classifies the electrodes under corresponding ASTM Base Metal Standard. The Base Material SA 387 Grade 22 falls under the same P No. 5A of SA335 P22.
Similarly, the ASTM A 387 Gr 22 Base material as per Specification SFA5.28/SFA5.28M, corresponds to the Table QW-422. Also, the material composition of SA 335, our material in consideration. However, this material applies to the plate form of testing procedures.
Selecting Manufacturer’s Electrode/Filler Wire
Finally, refer to Manufacturers Manuals relevant to Table 6, composition and material details.
If you are following the suggested vendor by scope, for example, “Lincoln Electric” or “ESAB” obtain their data specifications and suggested references. The corresponding filler wire is recommended.
Further, fill in the details in QW-404 of your PQR, or your production welds.
To sum up, these steps are meant to simplify the understanding of the process of filler rod selection for welding. However, you are advised to refer to relevant AWS/ASME Standards for a thorough understanding. That includes, complete listing of mechanical properties, chemical composition of as-deposited weld metal and testing procedures for the relevant electrodes. Also, the processes under consideration in line with the job scope.
On the other hand, I’d love to hear from you on the post! Do let me know in the comments section.
Related Additional Information and References:
AWS 5.1 Specification for CS Electrodes for Shielded Metal Arc Welding
ASME – BPVC Sec IX: Welding, Bracing and Fusing Qualifications & Sec II Part C: Specifications for Welding Rods, Electrodes and Filler Metals