Duplex pitting resistance equivalent number
Duplex Pitting Resistance Equivalent is a mathematical index used to evaluate the corrosion resistance of high-alloy steels in chloride-containing solutions. It takes into account the mass fractions of chromium, molybdenum, and nitrogen.
Physicochemical Mechanism of Action
The Duplex Pitting Resistance Equivalent (DPRE) is calculated by measuring the mass fractions of chromium (Cr), molybdenum (Mo), and nitrogen (N) in a high-alloy steel. These elements influence the material's corrosion resistance in chloride-containing environments.
Metallurgical Relevance & Risks in Welding
A DPRE that is too low can lead to increased susceptibility to chloride corrosion, which can cause cracking and wear of the weld. Conversely, a DPRE that is too high can increase corrosion resistance but may also impair formability and microstructure.
Workshop Practice & Action Items
When welding high-alloy steels with a specific DPRE, it is important to choose the correct welding process. This includes selecting the appropriate shielding gas and cooling technique. Some recommendations are:
• Use argon-based shielding gas mixtures.
• Ensure that cooling is not too fast to avoid compromising the microstructure.
• Regularly check the material's corrosion resistance after welding.