Question

when using 100 percent \\(\text{co}_2\\) with carbon steel, adding argon _______________ tensile and yield strength.

• increases
• decreases

Explanation:

Analyze shielding gas oxidation effects

Using the Shielding Gas Metallurgy and GMAW Shielding Gas Effects knowledge points

• Pure \(\text{CO}_2\) is highly reactive at arc temperatures, causing significant oxidation of alloying elements (like silicon and manganese) in the weld pool.
• This oxidation burns off these deoxidizers, reducing their concentration in the final weld metal.
• Adding inert argon to \(\text{CO}_2\) reduces the oxidizing potential of the shielding gas mixture.

Determine mechanical property changes

Using the Shielding Gas Metallurgy and GMAW Shielding Gas Effects knowledge points

• With less oxidation, more manganese and silicon remain alloyed in the solidifying weld metal.
• Higher retention of these alloying elements increases the solid-solution strengthening of the weld.
• Consequently, adding argon to a pure \(\text{CO}_2\) shield increases both the tensile strength and yield strength of the carbon steel weld.

Answer:

• Increases (Correct answer)
• Decreases