The inoculants are divided into the following types: ferrosilicon inoculants, silicon barium inoculants, silicon calcium inoculants, etc.
Ferrosilicon inoculants not only used in steelmaking industry, but also as metallurgical materials commonly used in cast iron industry. The ferrosilicon particles can be used by cast iron manufacturers to replace inoculants and nodularizers. The price is much lower than steel, and it is easier to be melted. It is a ferroalloy product with strong casting ability. The ferrosilicon inoculant with good quality has uniform particle size and good inoculation effect during casting, which can promote the precipitation and spheroidization of graphite. It is a necessary metallurgical material for the production of ductile iron; #75 ferrosilicon is widely used, and #45 ferrosilicon is extremely used few.
Features of ferrosilicon inoculants
It is economically cheap; in terms of structure, it reduces white spots, improves the uniformity of cross-section structure, promotes A-type graphite, increases the number of eutectic groups, and reduces segregation; in terms of performance, it improves strength and toughness.
Ferrosilicon particle inoculant dosage
The amount of use should be determined according to the actual situation, which has a great relationship with the conditions of the primary iron and the molten iron after melting, and should be adjusted according to the actual situation. In general, the addition amount for gray cast iron is 0.2~0.5%; for ductile iron, the general addition amount is 0.5~1.1%; for cast iron horizontal continuous casting ductile iron, the general addition amount is 0.8~1.5%.
Silicon barium inoculant
Silicon-barium inoculant is a bulk metallurgical material made by mixing silicon powder and barium powder according to the required ratio and making steel in a high-temperature furnace. It is an additive in the casting process of foundries, which can promote graphitization and reduce whitening tendency, improve the morphology and distribution of graphite, increase the number of eutectic groups, and refine the characteristics of the matrix structure. It has a good effect in a short period of time (about 5-8 minutes) after inoculation treatment. The particle size of the silicon-barium inoculant should be uniform and moderate in size, so as not to affect the inoculation effect. The molten iron after inoculation should be fully stirred before slag removal.
The amount of silicon-barium inoculant added is generally controlled at 0.3%-0.6%. Do not blindly increase the amount of inoculant. Excessively high inoculant amount will increase the viscosity of molten iron and the tendency of slag inclusion, keyhole, and shrinkage.
The use of silicon barium inoculant
Silicon barium inoculants are mainly used in the inoculation of ductile iron and gray cast iron molten iron. The silicon-barium inoculant strongly increases the graphitization core, refines the graphite, promotes the A-type graphite in the gray iron casting, and improves the strength. For the ductile iron casting, it can make the graphite in the ductile iron fine and round, and improve the nodularization level. Resistant to fading while preventing the associated nodular fading. The wall thickness sensitivity is small and the tissue is uniform. Significantly reduce the whitening tendency, reduce the relative hardness, improve the machinability of castings, and be used as inoculants and nodularizers in the cast iron industry.
0-0.25mm: used for inoculation in the mold (precise inoculation, higher efficiency)
0.2-1mm: used for inoculation with flow (the control of inoculation amount is more accurate)
1-3mm, 3-8mm are used for inoculation in the bag (the inoculation time must be controlled at more than 70% of the tapping time)
8-15mm for inoculation in furnace
Calcium silicon inoculant
The graphitization ability of silicon-calcium inoculant is 1.5-2 times greater than that of 75FeSi inoculant, and the number of eutectic groups is significantly increased.
When using silicon-calcium inoculants, it is necessary to understand why Ca is added. Ca is an alkaline earth element and is very active. Therefore, he can react with gas atoms or non-metallic elements in molten iron, such as O, S, N, C, H. In general, these elements themselves will inhibit graphite nucleation, or change the graphite growth morphology. Therefore, one of the main roles of Ca is actually equivalent to a cleaning element. In addition, compounds formed with elements such as S not only remove these harmful elements, but also form the crystallization core of graphite and improve the morphology of graphite. It must be emphasized that the silicon-calcium inoculant contains 2.4% Al, and its effect is the same as that of Al in the previous ferrosilicon inoculant. Therefore, calcium silicate is a very effective and stable inoculant. However, the disadvantages are fast decay, large amount of slag, light specific gravity and large pollution. In order to improve these problems, low-Ca inoculants have appeared, and their Ca content is generally lower than 16% Ca.
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