The liquid viscosity will affect the rise of the solid-liquid interface in the h height region of the copper wire graphite setting tube. When the viscosity of molten liquid is high, the interfacial tension between molten liquid and the inner wall of graphite setting tube will increase, and the friction will increase. The solid-liquid interface is not easy to rise with the rise of solidified material, which will cause the separation of solidified material and molten liquid surface and the interruption of continuous casting. The is true when the liquid viscosity is low. Generally, under the action of pressure P, the viscosity of molten liquid is not the main cause of failure of up-lead continuous casting. Only when the height H is not large enough and the pressure P becomes small, the liquid viscosity will become the main reason for the failure of up-lead continuous casting.
The main factors affecting the viscosity of molten liquid are: ① molten temperature. The viscosity of molten liquid will decrease when the temperature is high. But the temperature of the molten liquid should not be too high, generally should not be higher than the melting point of the alloy about 200℃. When the molten liquid temperature is too high, it will make the molten liquid into the graphite setting tube difficult to solidify, so that the up-lead continuous casting failure, and increase the loss. ② Chemical components of molten liquid. Trace elements, such as Ni, reduce the viscosity of the molten liquid.
When the metal or alloy liquid and gas solubility reaches saturation, the temperature is higher, if the melting time or the longer the holding time, the more air content in the melt, due to the exposure of the liquid and contact with air, molten metal during crystallization chamber cooling solidification more prone to defects such as porosity, loose, easily lead to the failure in continuous casting. When the melting temperature is too low, the metal molten liquid is not conducive to flow due to the increase of viscosity, which leads to the solid-liquid level separation in the mold, and also leads to the failure of up-casting. Therefore, the surface of molten liquid is usually covered with a certain amount of coating agent to reduce the amount of suction of molten liquid, but also to prevent metal oxidation.
Liquid and exists in the melting of the scum, these scum in the solidification of metal and between liquid and form a layer of thin film, prevent the solid-liquid surface effective union, or after the solidification of casting rod cross-sectional hole, inclusion and so on, reduce the strength of casting rod, the casting bar row is easy to be pulled on traction, continuous up-casting failure cause. In this case, the molten liquid should be dregs, if necessary, the appropriate use of slag removal agent, slag removal and then lead up continuous casting.
① The cooling speed is mainly related to the flow rate of cooling water. The larger the flow, the faster the cooling speed. When the cooling pipe diameter, water pressure and other parameters are fixed, the flow rate of cooling water is also fixed. At this time, the cooling speed is only affected by the initial temperature of cooling water, but the water flow is often reduced due to sediment such as scale. In addition, the scale sediment layer has the effect of heat insulation, so the scale sediment layer will reduce the cooling speed. In order to avoid scale deposit affecting the cooling speed, scale in cooling water circulation pipe and mold should be cleaned regularly, and softened water or pure water can be used for cooling when conditions permit.
