TItle：What are the effects of the thickness of the liquid slag layer of the mold and its measurement methods?
Description：Briefly explain the influence of the thickness of the liquid slag layer of the mold on the slab and how to measure it.
Keywords： Crystallizer slag
To achieve a good use effect, the mold powder must have the thickness of the liquid slag layer that meets the actual needs. If the liquid slag layer is too thick or too thin, the slab will have surface longitudinal cracks. If the slab pulling speed is 1.2～1.5m/min, the thickness of the liquid slag layer is less than 5mm, the longitudinal cracks of the slab increase obviously (from 50mm/m to 200mm/m), the thickness of the liquid slag layer is 6-15mm, and the longitudinal cracks almost disappear , The liquid slag layer is greater than 20mm, and the longitudinal cracks have increased.
The thickness of the liquid slag layer is less than a certain value, and the slag ring formed along the periphery of the mold will block the channel between the meniscus liquid slag flowing into the blank shell and the copper wall, so that the liquid slag cannot flow smoothly into the blank shell surface to form a uniform The slag film may cause longitudinal cracks on the surface of the corresponding cast slab. So what is the thickness of the liquid slag required for the liquid slag to pass through the channel downstream of the meniscus without being blocked? According to theoretical calculations, the pulling speed is less than lm/min, the thickness of the liquid slag layer is 5-7mm, and the pulling speed is greater than lm/ min, the thickness of the liquid slag layer is 7-15mm. This is consistent with the critical liquid slag layer thickness measured in production practice.
The method of measuring the thickness of the liquid slag layer in production: tie a steel wire and a copper wire (or aluminum wire) together and insert it into the slag layer of the mold. Because the temperature of the liquid slag is higher than the melting point of copper, the copper wire melts , Measure the length of the melted copper wire is the thickness of the liquid slag layer. Since the molten steel temperature at each point of the slab mold section is different (such as the immersion nozzle area and the mold edge), the thickness of the liquid slag layer is also different, so the thickness of the liquid slag layer at different positions can be measured.