Casting method of thick and large castings

Abstract

The invention discloses a casting method of thick and large castings. Coke is used as fuel; metal furnace materials are smelted into smelted steel in a cupola furnace; tapped smelted steel, nucleating agent and electrolytic copper are flushed into a casting ladle; the fixed carbon content in the coke is above 87%, thereby the tapping temperature of the smelted steel in the copula furnace can be ensured to be above 1500 DEG C so as to obtain purified smelted steel; the nucleating agent contains 0.2%-0.5% of silicon-barium nucleating agent, 0.2%-0.4% of 75% ferro-silicon and 0.1%-10% of molybdenum-containing nucleating agent based on the weight of the tapped smelted steel; the silicon-barium nucleating agent and the 75% ferro-silicon have the action of increasing the crystallizing core of the graphite in the smelted steel; the graphite in the smelted steel is fine and is distributed uniformly so that the internal and external performances of thick and large castings are consistent; the electrolytic copper and the molybdenum-containing nucleating agent are added to the smelted steel to promote the generation of pearlite matrix organisms and thin the pearlite matrix organisms so that the strength and hardness of the nucleated cast iron are increased, and the internal and external performance tendencies are consistent.

Description

technical field [0001] The invention relates to a casting method of a casting, in particular to a casting method of a thick casting. Background technique [0002] Castings with a wall thickness of more than 70mm can be called thick castings. In the prior art, the casting method of thick castings is as follows: use coke containing 83% fixed carbon as fuel, and melt the metal charge into molten iron in a cupola , the metal furnace charge contains rust-free high-quality scrap steel, newborn iron, and old iron for machine tool castings. The content of scrap steel is about 30%. After the inoculant is flushed into the groove, it enters the ladle together, and then injects it into the mold cavity to cast the required casting. The content of fixed carbon in the coke is low, the combustion value is low, and the coke is in the form of lumps. The size of each block is not equal, and it is easy to burn insufficiently and unevenly, so the tapping temperature is not high, which is about ...

AI Technical Summary

Problems solved by technology

[0002] Castings with a wall thickness of more than 70mm can be called thick castings. In the prior art, the casting method of thick castings is as follows: use coke containing 83% fixed carbon as fuel, and melt the metal charge into molten iron in a cupola , the metal furnace charge contains rust-free high-quality scrap steel, newborn iron, and old iron for machine tool castings. The content of scrap steel is about 30%. After the inoculant is flushed into the groove, it enters the ladle together, and then injects it into the mold cavity to cast the required casting. The content of fixed carbon in the coke is low, the combustion value is low, and the coke is in the form of lumps. The size of each block is not equal, and it is easy to burn insufficiently and unevenly, so the tapping temperature is not high, which is about 1450 degrees, which affects the subsequent casting temperature, so that the central part and surface part of the thick and large castings are in the metallographic structure and mechanical properties. There is a large difference. After the metal charge is melted to form molten iron, the molten iron is in direct contact with coke, and the carbon content and sulfur content in the molten iron will be significantly increased. Therefore, in order to ensure that the chemical components in the formed casting meet the requirements, it is necessary to Precisely calculate the ingredients in the metal furnace charge. At present, the steel content in the raw material is low, which leads to the imbalance of chemical components in the subsequent molten iron, which affects the cooling and forming of the casting, especially the central part of the thick casting. and surface properties

The inoculant is mainly 75% ferrosilicon. Although 75% ferrosilicon can reduce whiteness, improve graphitization, and improve the hardness and strength of cast iron, it can reduce the difference in the performance of the central part and surface part of thick and large castings. Not obvious

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