Casting process for high-strength vermicular graphite cast iron materials

Abstract

The invention discloses a casting process for high-strength vermicular graphite cast iron materials. The casting process specifically comprises the steps of a, a furnace charge comprises, by weight, 40%-60% of a steel scrap and 40%-60% of raw iron, and the proportioned furnace charge is put into a medium-frequency furnace for smelting; b, after molten iron smelting is completed, the molten iron refining temperature is controlled to be 1520DEG c-1550DEG c, and heat preservation is carried out for more than 10 minutes; and c, a primary silicon-calcium-barium nucleating agent and a rare-earth magnesium vermicularizing agent are added into a molten iron ladle, wherein the weight of the silicon-calcium-barium nucleating agent is 0.5%-0.8% of the amount of the produced molten iron, and the molten iron undergoes the vermicularizing treatment by adopting an in-ladle pour-over method; d, the ladle stream secondary inoculation process is adopted, the silicon-barium inoculant with the weight accounting for 0.1%-0.2% of the weight of the produced molten iron is added for secondary inoculation; and e, the inoculated molten iron is poured into a sand mold casting mold, the casting time is controlled within 10 minutes, and the casting temperature is controlled between 1400DEG c-1460 DEG c. According to the casting process, the shrinkage porosity tendency of a product is reduced, forming of nucleation when the molten iron is solidified can be promoted, and the performance of the vermicular graphite cast iron materials can be improved.

Description

technical field [0001] The invention relates to the field of engines, in particular to a casting process made of high-strength vermicular graphite cast iron. Background technique [0002] Diesel engine cylinder heads are usually produced with compacted graphite iron, which has the high strength of ductile iron and good castability similar to gray cast iron. The current production method of vermicular graphite cast iron is: pig iron, scrap steel, returned iron and other alloys are added to the intermediate frequency furnace as the furnace material to be smelted into molten iron. 0.3-0.5% silicon-calcium-barium primary inoculant (inoculant particle size requirement 3-8mm), the silicon-calcium-barium primary inoculant is used to cover the rare earth magnesium vermiser, and the vermicularization is carried out by the bag flushing method deal with. After the vermicomposting of the molten iron is completed, it is poured, and 0.05-0.1% of silicon-calcium-barium secondary inoculan...

AI Technical Summary

Problems solved by technology

The performance of the compacted graphite cast iron obtained in this way is low. At the wall thickness of 15-25mm, the tensile strength is usually ≤400MPa, the elongation is ≥1%, the Brinell hardness is 170-200HB, and the creeping rate is ≥80%.

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