Control Of Liquid-Drop Surface Shape In Melt

The samples of great mass arbon steel can not be melt using a high temperature confocal laser scanning microscopy (HTCLSM). Because only arc surface of the tiny liquid-drop top can be observed, it is difficult to obtain uniform definition images. There exists the question that the image definition is decreased at low magnification or the actual control is difficult within existing solutions, it indicates the non-uniform question of image definition is not completely solved. In this paper, the surface shapes of tiny metal liquid-drop under vacuum are studied utilizing a home-made experimental equipment. The aim of making the top surface of tiny metal liquid-drop to be a flat surface is achieved, which prvides a method for obtaining definition uniform images in the HTCLSM system.The high temperature vacuum furnace and the image monitoring system were home-made, and the highest temperature of the vacuum furnace reaches 1650℃. The sample in the melting process is not oxidized and its surface is bright and clean. The temperature measurement system can exactly measure the actual temperature of tiny liquid-drop, and the temperature data can be synchronously displayed on the monitor and be saved in a computer hard disk. The resolution of image-forming system is higher, so the metal droplet of diameter less than 1 mm can be clearly shot within 350 mm working distance. The shot images can be enlarged 50 times, which lays a foundation for exactly measuring the contact angle. The image-forming system holds a video function, so the melting process and the tiny change of liquid-drop shape are recorded in the form of a video in the computer hard disk and they can be called and analyzed at any time.The experimental results show that the shape of the liquid-drop for Fe-0.05%C-0.28%Si steel will be changed at 1600℃, when the carbon steel sample of 0.5g is laid on the Al₂O₃ sloping of 15 degrees. Though the radius of curvature of the liquid-drop top surface is obviously enlarged, the effect of improving the top surface shape of the liquid-drop only depending on the gravity flow of tiny liquid-drop is finite. Larger flat surface on the top surface of liquid-drop can be gained through placing a pressure plate on the top, while a horizontal surface can not be obtained. For the carbon steel sample of less than 0.8g, the hanging drop is automatically formed in the melting process under the condition that the gap between the solid sample and Al₂O₃ single crystal plate is 0.3mm, and the shape retains invariant when it is hold for 20 min at 1600℃. The contact surface between the sample and Al₂O₃ single crystal plate is 24mm². It is found that the transmissivity of Al₂O₃ single crystal plate is very good and the surface state of tiny liquid-drop can be distinctly shot through Al₂O₃ single crystal plate.