Duplex phase ratio
The duplex phase ratio is the quantitative balance of ferrite and austenite in the microstructure. It should be between 40 and 60 percent to ensure optimal mechanical properties and corrosion resistance.
Physicochemical Mechanism of Action
The duplex phase ratio describes the mixture of ferrite and austenite in the metal. Ferrite is a soft, crack-resistant phase, while austenite is harder and more formable. A balance of these two phases results in a material with balanced properties.
Metallurgical Relevance & Risks in Welding
An unbalanced duplex phase ratio can cause mechanical problems. Too much ferrite makes the material softer and more prone to cracking, while too much austenite makes it harder and more formable but potentially less corrosion-resistant. An optimal range of 40 to 60 percent ferrite ensures a good combination of hardness, formability, and corrosion protection.
Workshop Practice & Action Items
To achieve a duplex phase ratio of 40 to 60 percent, pay attention to the correct welding temperature and cooling pattern. When selecting the steel, choose one with an appropriate content of carbon and other additions. During welding, it is important that the weld does not cool too quickly or too slowly. An optimal cooling time of 10 to 20 seconds can help achieve the desired phase ratio.