Study On Surface Segregation Control Of High-throughput Continuous Casting And Rolling AlFeSi Alloy Casting Plates

The high-throughput continuous casting and rolling process is to cast a molten aluminum alloy liquid into a continuous casting slab with a thickness of about 19mm from a continuous casting machine,and then directly perform a continuous casting process of three continuous rolling.This process has a short flow and can Low consumption,high production efficiency and other advantages.The casting process of this process is completed in a mold composed of an endless steel belt and two movable rectangular chain metal stoppers in a continuous casting machine.The surface quality of the continuous casting billet,especially the surface segregation,depends on the rigidity of the steel strip as the supporting surface,the surface roughness,the uniformity of cooling,and the composition of the alloy,and will be inherited to the subsequent rolling process and affect the final rolled product Surface quality.The research on the surface segregation control behavior of High-throughput continuous casting and rolling AlFeSi alloy continuous casting slab is of great significance for improving the surface quality of AlFeSi alloy products.This article takes High-throughput continuous casting and rolling AlFeSi alloy as the research object,adopts microscopic metallographic observation,SEM and EDS analysis,XRD analysis and other analytical methods,by adjusting the Fe/Si ratio,total Fe and Si content,casting cooling rate,The thickness of the surface segregation layer and the proportion of the second phase of the surface layer were used to study the surface segregation law of the slab.This paper systematically studied the influence of Fe and Si content on the surface segregation of continuous casting and rolling AlFeSi alloy casting plate.The results show that:When the Fe/Si ratio increases from 0.8 to 2.0,the segregation on the slab surface increases first and then decreases.When the Fe/Si ratio is 1.25,the surface segregation is the most serious.The thickness of the surface segregation layer is about 80?m,and the second phase of the surface layer accounts for 36.7%;when the Fe/Si ratio is 2.0,there is almost no segregation layer on the sample surface,and the second surface layer The proportion is 11.07%.With the increase of the Fe/Si ratio,the main Segregation phase in the surface layer changed from the needle-shaped?-Al₅Fe Si phase to the network-shaped?-Al₈Fe₂Si phase,and then to the needle-shaped and lath-shaped Al₃Fe phase.When the total amount of Fe and Si increases from 0.45%to 1.44%,the surface segregation of the slab increases significantly,the thickness of the surface segregation layer increases from 45?m to 80?m,and the proportion of the second phase on the surface increases from 11.2%to 36.7%;The Segregation phases are all?-Al₈Fe₂Si phase.When the total amount of Fe and Si is 0.45%,the Segregation phase with the surface layer occupying the secondary position is Al₃Fe phase.As the total amount of Fe and Si increases,there is a small amount of?-Al₅Fe Si phase in the surface layer.This paper studied the effect of cooling rate on the surface segregation of the slab through the step test block.The results showed that when the cooling rate increased from 27.8?/s to 248.5?/s,the surface segregation was reduced,and when the cooling rate increased to 108.2?/s In the future,the second phase segregation phenomenon has disappeared on the surface of the aluminum alloy casting plate.As the cooling rate increases,the grain size of the surface layer of the AlFeSi alloy casting plate decreases,and the gap between the grains decreases.The size of the second phase,which is mainly segregated between grain boundaries,decreases,and the number decreases.Based on the above findings,when high-throughput continuous casting and rolling produces AlFeSi alloys,the content of alloy elements is reduced,and the surface segregation tends to be weakened;when producing AlFeSi?8011?alloys with high Fe and Si content,the casting cooling rate is appropriately increased and Fe/Si ratio is adjusted to about 1.7,the segregation is relatively light,and the Segregation phase is the network?-Al₈Fe₂Si phase,which is conducive to the subsequent improvement of the slab quality,and has been tested and verified in production.