Misconceptions About Filler Metal Strength

October 28, 2019 10:24 am

Selecting the correct filler metal isn’t always clear cut as different welding applications call for different ones. Here are four misconceptions about filler metal strength to consider and guidelines to right the wrong.

 

Filler metal with a higher typical tensile strength is best

Stronger isn’t always better. “The American Welding Society (AWS; Miami, FL) has established standards that guide the manufacturing and intended use of welding wires and stick electrodes. Filler metal classifications include information on tensile strength. and data sheets produced by filler metal manufacturers provide usability information. However, in many cases the typical tensile strength listed will be higher than what AWS requires for a particular welding wire or stick electrode classification. 

For example, an AWS E71T-1 gas-shielded flux-cored wire may meet an AWS tensile strength spec of 70 ksi (1,000 lb/sq in), but the filler metal manufacturer rates it at 84 ksi with 100 percent CO2 or 90 ksi with 75 percent argon and 25 percent CO2. That is because filler metal manufacturers create products that either meet or exceed AWS requirements.” Always use the AWS classification as the guiding principle for weld design. The tensile strength on the data sheet is not always a good determining factor of the appropriate filler metal strength.

 

Certain types of filler metals are inherently stronger

When comparing filler metals that are equal in AWS tensile strength, that means that the minimum AWS tensile strength is also equal. The only determinant of different weld strength comes down to which application it is being used for. “The current or heat input in the welding process needs to match the thickness of the material being welded.  If an operator uses a short-circuit process with solid wire to weld half-inch-thick material, then the result will likely be a weaker weld. A spray process would better achieve proper weld strength with a solid wire.”

 

Shielding gas and heat input don’t affect filler metal strength

Shielding gas does indeed impact filler metal strength and Chapry V-notch impact values. The mixtures for shielding gas with higher levels of argon produce filler metal that can achieve welds with higher tensile and yield strength.  When CO2 is higher in the mixture, the opposite will occur. You can access recommended argon and CO2 balances from manufacturers so you can predict the outcome in terms of strength. Balance these factors out to gain the desired strength of your finished weld. “A welding operator may use a higher argon level if high heat input has decreased the strength of the weld.

 

The filler metal strength always needs to match the base metal

An operator could match A36 steel that has a minimum yield strength of 36 ksi to a filler metal with similar strength properties.  A AWS A5.XX 70 ksi tensile class filler metal that provides 70 ksi minimum tensile strength and 58 ksi minimum yield strength could be a good option.” Under-matching filler metal strength to the base material is okay when the weldmat design does not require the strength of the base material. and know the.

 

The selection of the correct filler metal for your application will depend on having the right information. Access the full article here to know the filler metal misconceptions.

1 Comment

    li class="comment even thread-even depth-1" id="comment-29659">

    It’s all Greek to me. I welded pipe for 28 years on power plants and refineries and the ratings were all different. The “everyday” rod we used was E6010, with a 60,000 psi tensile strength, then “low hydrogen” 7018, and 9018 on main steam lines, etc. I think the 9018 was used on pipe containing 2% chromium, but that was 35 or 40 years ago. The KSI ratings appear to be metric, which I never did give a shit about, and neither do most Americans. The metric system is fine for people in less developed countries who have a hard time with math. However, now that America is becoming infested with Liberals and Millennials, I suppose something simpler will be required. Maybe job specs saying “use the green rod on green pipe, and blue rod on blue pipes” will make it easier for them.

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