下拉式热型连铸工艺中的阻流研究

Study on Flow Resistance in Downward OCC Process

为了解决下拉式热型连铸过程中金属液静压头过高容易拉漏,从而迫使连铸速度必须降得很低这一问题,在铸型上游设置了过滤网式、窄缝式和小孔式三种不同形式的阻流器,分别进行阻流试验,以期降低压头。试验结果表明,过滤网式阻流器由于孔径过大,剩余压头太低,基本没有阻流作用。窄缝式阻流器主要利用摩擦阻力达到阻流,即使窄缝长度达50 mm,宽度为0.3 mm时,剩余压头也只有2～3 mm,阻流效果不显著。小孔式阻流器主要利用表面张力达到阻流,当小孔直径为0.5 mm时,剩余压头可达8 mm,可以显著降低铸型上游金属液的压头,从而防止下拉式热型连铸的拉漏。

In the downward Ohno continuous casting process(OCC), the liquid metal hydrostatic head is relatively high so that the liquid metal is extremely prone to break out, which leads to very low casting speeds. In order to solve this problem,three different types of flow resistant devices including filter screen, narrow slit and small hole types were mounted in the upstream of the mold. The flow resistance tests were carried out to reduce the pressure head. The test results show that the filter screen flow resistance device basically has no flow resistance due to the large pore dimension and low residual pressure head. The narrow slit flow resistance device uses the friction force to achieve flow resistance. Even if the narrow slit length is50 mm and the narrow slit width is 0.3 mm, the residual pressure head is merely 2-3 mm, the flow resistant effect is not significant. The small hole flow resistant device uses surface tension force to achieve flow resistance. When the hole diameter is 0.5 mm, the residual pressure head is up to 8 mm, which can reduce the pressure head of the upstream metal liquid of the mold and prevent the break out in the downward OCC process.