Melt purification is a common technical basis for improving the quality of aluminum and a key technology for improving the quality of aluminum. The presence of gases and non-metallic inclusions in the melt has a significant effect. It mainly includes: the subsequent processing and forming properties of the blank, the physical properties of the final product, mechanical properties, corrosion resistance, structural integrity and appearance quality.
Second, factors affecting melt quality
1 External materials: raw and auxiliary material quality, waste category and proportion of addition;
2 smelting and online processing:
Melt temperature, standing time, refining in the furnace, slag slag operation, furnace cleaning degree, aluminum liquid converter/casting, flow tank hygiene and drying degree, tool drying degree;
Degassing, filtering, refining additives;
3 Casting process: distribution bag, metal flow, metal temperature, operation is not standardized.
Three impurity classification
1 Gas impurity: H2
2 Basic impurities: Na, Ca, Li, etc.
3 Non-metallic impurities: commonly referred to as inclusions
Al2O3, spinel, MgO, FeO, MnO;
AlN, TiB2, (Ti, V) B2, Al4C3;
MgCl2, NaCL2, CaCl2 salts;
4 Liquid impurities: low melting point chlorides, fluorides and mixtures thereof.
How to judge the quality of the melt
1 High quality products must be used for the ultimate purpose of reducing or eliminating non-metallic inclusions in the aluminum melt;
2 There are many methods for melt processing at home and abroad, but the effect of the treatment requires an accurate evaluation price system;
3 In-melt inclusion evaluation is the comprehensive judgment and analysis of the melt processing system used. Based on the comprehensive and systematic quantitative analysis of the whole process melt treatment, the evaluation criteria are established to make the filter selection and The use of more scientific, seeking to optimize the performance of aluminum products in the most economical and reasonable way.
Five methods for evaluating inclusions in melt
1 At present, the main evaluation methods are off-line analysis. After the melt is sampled before and after filtration, the inclusion content is measured and compared. The conventional methods include quantitative metallography, chemical analysis, image scanning (IA), volumetric method, and scanning electron microscopy. (SEM), laser diffraction particle size analysis (LDPSA), non-destructive ultrasonic method (CUS), laser microprobe mass spectrometry (LAMMS), X-ray diffraction (XPD), photoelectric scanning, Auger electron spectroscopy Law (AES) and so on. Although the offline analysis has high accuracy, the detection result lags behind the casting process, and only the filtering efficiency at the sampling time can be expressed, and the low filtration efficiency change cannot be tracked and adjusted.
2 Western developed countries have developed a variety of new evaluation techniques for production sites in response to strict quality requirements for high-end aluminum products.
11LiMCA11 liquid metal cleanliness analyzer, invented by ABB Canada.
22PoDFA device, invented by Canadian Aluminum Corporation;
33LAIS method, invented by United Carbide Corporation;
The 44Prefil-Footprinter device was invented by ABB Canada.