2. Process background
Fig. 1. Softening zone at switch surface (a) in high-temperature state and (b) in low-temperature state.Figure optionsDownload full-size imageDownload as PowerPoint slide
3. Thermal simulation experiments
To understand SR1078 mechanism of the softening zone formation, we designed lab scale experiments to simulate the above process conditions using DIL 805L dilatometer. The samples were taken from the standard 20Mn2SiCrMo bainitic rail and cut into cylinder shape with the size of Ø4 × 10 mm. The Ac1 temperature of the steel is digestion measured as 713 °C using DIL 805L dilatometer. The samples were heated to four different temperatures (550 °C, 700 °C, 750 °C and 850 °C), all at the rate of 10 °C/S and then held for 3 min followed by air cooling to room temperature. The harnesses of as-treated samples were measured by microhardness tester and their microstructures were observed by scanning electronic microscope (SEM).