Ferrite experiment of duplex stainless steel ordered by Indonesian customer

Since the customer has such high requirements on the corrosion resistance of the material, it is natural that we are required to do pitting experiments after the production of the product, so as to verify the real corrosion resistance of the product.

About the experiment, the customer proposed three kinds of experimental experiments, one is ferrite experiment, the other is pitting corrosion experiment, as well as mechanical properties experiment, among which, mechanical properties experiment is more common, not more details, focus on introducing ferrite experiment and pitting corrosion experiment.

S32205 Stub Ends

First, a relatively simple ferrite experiment is introduced. The test standard is ASTM E 562.

Duplex stainless steel refers to ferrite and austenite account for about 50% each, generally less phase content also need to reach at least 30% of the stainless steel. Duplex stainless steel has excellent corrosion resistance and mechanical properties, thanks to the existence of two phases: ferrite phase + austenite phase. Ferritic stainless steel has large thermal conductivity, small expansion coefficient, good oxidation resistance, excellent stress corrosion resistance and other specific, but there are also poor plasticity, plasticity and corrosion resistance after welding significantly reduced shortcomings; Austenitic stainless steel is resistant to oxidizing acid medium and has the advantages of high toughness and plasticity, but its stress corrosion resistance is poor. At the same time, ferritic stainless steel and austenitic stainless steel have the tendency of intergranular corrosion. Duplex stainless steel, combined with the advantages of ferritic stainless steel and austenitic stainless steel, at the same time because of the ferrite phase, the intergranular corrosion of austenitic phase sensitization temperature difference, when the temperature in a certain phase of sensitizing range, another phase can reduce poor chromium in grain boundary area, and made the duplex stainless steel intergranular corrosion resistant performance is improved. Therefore, the corrosion resistance and mechanical properties of duplex stainless steel can be inferred by measuring ferrite content.

Methods: Standard Test Method for Determining Volume Fraction by Systematic Manual Point Count was used

As the customer has specified the test standard and sample preparation method, our company soon reached an agreement with the customer for ferrite and finally passed the test smoothly.

The pitting experiment will be introduced in the next paper.