On the surface or inside of the cast-rolled sheet, the defects of metal or metal inclusions that are different from the base metal in the macro or microstructure, and in the ultrasonic inspection will destroy the continuity of the base structure and are an irreparable defect. In severe cases, it will be scrapped.
Defects of Metal Main Reason
The aluminum ingots, master alloys, and waste materials in the raw materials contain impurities such as oil and moisture, which are easy to form oxides and refractory inclusions; the covering agents, slagging agents, refining agents, and refiners in the additives are easy to form potassium, Sodium, chlorine, A12Ti, TiB2, etc. are mixed with graphite rotors, graphite emulsion and combustion media used in thermal spraying, refined gases, combustion media for smelting and launder heating, such as heavy oil, liquefied gas, etc., which are easy to form carbon and aluminum nitride , Chlorine, sulfur and other inclusions.
The furnace, the flow system, the tools are not clean, the casting nozzle is fine, the casting nozzle is peeled, and the slag is easy to form inclusions such as calcium, silica and alumina.
Improper process and operation, such as unclean melt slag, improper mixing, excessively high melting temperature, and excessively long melting time, etc., are likely to form oxidation.
The degassing and filtering effect is not good.
Metal Inclusions Prevention Method
Ensure that the raw and auxiliary materials are clean, and the aluminum ingots, intermediate alloys, and waste materials used are free of oil and moisture; use high-quality additives, graphite emulsion and combustion media.
The furnace should be cleaned regularly to ensure that the furnace, flow system, tools, etc. are dry and clean.
When thermal spraying or graphite spraying is used, the ratio and spraying amount should be adjusted to ensure uniform spraying.
Strengthen the refining and degassing and the filtration and purification of the melt, and improve the filtration accuracy.
Shorten the smelting time as much as possible, lower the smelting temperature appropriately, and avoid mixing oxide scale into the melt during production operations.
The nozzle cavity and aluminum scraps on the roller surface should be cleaned before the vertical plate to minimize slagging. If the casting nozzle is damaged, stop and replace it in time.