Dual-Phase Bainitic Structure
A microstructure comprising lower and upper bainite stages, adjusted through specific continuous cooling paths or isothermal holding times.
Bainite forms during cooling from the austenite region when you stop between pearlite and martensite formation. In two-stage bainite, this happens in two steps – first one stage forms, then the other. The structure is a compromise between hardness and toughness, good for parts that need both. If you don't control cooling properly during welding or work too early, the transformation stays incomplete. Then you get a mixed structure that's brittle and prone to cracking. You need to control heat input and cooling time so the part has enough time in the right temperature range to transform cleanly. In practice, that means not cooling too fast after welding, but giving the workpiece the necessary hold time. If you do that, you get a tough, hard structure without nasty surprises.