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The core value of the strontium silicon inoculant is to optimize the graphite morphology and refine the grains. It is especially suitable for cast iron parts with high requirements for graphite distribution and mechanical properties. The specific applications are as follows:
Gray cast iron production (core application field)
In gray cast iron, the graphite morphology directly determines its mechanical properties (such as tensile strength, hardness) and processing properties.
The role of the strontium silicon inoculant is reflected in:
Promote the formation of A-type graphite: inhibit harmful graphite such as D (fine flakes), E (interdendrite flakes), so that the graphite is evenly distributed flakes (A-type), and reduce stress concentration. For example, in the machine tool bed grey cast iron (HT250), after adding 0.3-0.5% strontium silicon, the proportion of A-type graphite can be increased from 70% to more than 90%, and the tensile strength can be increased from 230MPa to 260-280MPa.
Improve the resistance of thin-walled parts to white mouth: Thin-wall castings (wall thickness <5mm) cool quickly, making them prone to hard and brittle 'white mouth tissue' (cementite), resulting in difficult processing. Silicon strontium can delay the formation of cementite through the 'hysteresis crystallization' of strontium, reducing the thickness of the white mouth layer in the thin-walled area from 1-2mm to below 0.3mm. For example, after the cylinder block of the automobile engine (3-4mm at the thin wall) is incubated with strontium silicon, the life of the cutting tool will be extended by 20-30%.
Reduce cross-sectional sensitivity: Thick and large gray cast iron parts (wall thickness > 50mm) are prone to uneven structures between the core and the surface due to differences in cooling speed. Silicon strontium can be uniformly incubated, so that the hardness difference in different thickness parts of the casting can be reduced from ±30HB to less than ±10HB.
Ductile cast iron assists in fertilization 01. In ductile cast iron, strontium silicon is usually used as a 'secondary incubator' and is used in conjunction with spheroidizing agents.
The core functions are:
Refining graphite balls: reduce the size of graphite balls (from φ50-80μm to φ30-50μm), increase the number of balls (from 80-100 pieces/mm² to 120-150 pieces/mm²), and improve the spheroidization rate (from 85% to more than 95%). For example, in wind power flange ductile iron (QT450-10), strontium silicon and barium silicon calcium can increase the elongation from 8% to 10-12%.
Inhibiting the anti-spherization: When the molten iron stays for a long time (>30 minutes), the anti-decayability of strontium silicon can reduce the burning of spherical elements (such as magnesium and cerium) and maintain the stable spherical effect.
Production of special cast iron parts
Wear-resistant cast iron: For example, machine tool guide rail (HT300), strontium silicon can improve the hardness by refining the pearlite structure by 10-15% (from 200HB to 220-230HB), while maintaining good wear resistance.
Low-stress cast iron: Through uniform graphite distribution, the internal stress of the casting is reduced and deformation after processing is reduced.
