Casting method of spheroidal graphite cast iron valve

Abstract

The invention discloses a casting method of a spheroidal graphite cast iron valve, and relates to the spheroidal graphite cast iron valve. The method comprises the steps of model making, modeling, smelting, pouring, heat treatment and obtaining of a finished product valve casting. Alloy elements are not added, the spheroidal graphite cast iron valve with the supersize can be stably produced, a dedicated slag blocking device is arranged at the front end of a transverse sprue, when molten iron of the transverse sprue is introduced into the front end, the slag blocking effect is achieved, it is ensured that a mold cavity is rapidly and stably filled with the molten iron, oxide inclusions are reduced, a heat preservation top riser is adopted, and is placed on the top of the valve, and castingfeeding, slag discharging and exhausting are facilitated; a chilling block is arranged at the position, on the large and thick section and the portion with the large wall thickness difference, in thecasting, chromite sand is used around an even core and a shaft head in a shaft hole of the casting, the upper portion of an annular belt is paved with chromite sand, it is ensured that the casting canbe subject to directional sequential solidification, and meanwhile, the casting surface quality is ensured, and the method is particularly suitable for making a spheroidal graphite cast iron water and electricity butterfly valve with the supersize and the large section.

Description

technical field [0001] The invention relates to a nodular cast iron valve body, in particular to a casting method for a nodular cast iron valve body. Background technique [0002] As is known, the function of the butterfly valve in the hydroelectric generating set is to adjust or cut off the water flow. The valve body is immersed in water for a long time, the water flow changes greatly and the working environment is harsh. The butterfly valve plays a very critical role in the safe and stable operation of the hydropower station equipment and the system in which it is located. In order to reduce the production cost of the hydroelectric generating set, the life of the butterfly valve is required to be high, but if the valve body fails unexpectedly, the replacement cost and related losses will be huge. It meets the requirements of high fatigue strength and excellent impact toughness, that is, it has certain resistance to fracture and crack growth under specified medium temperatu...

AI Technical Summary

Problems solved by technology

In order to reduce the production cost of the hydroelectric generating set, the life of the butterfly valve is required to be high, but if the valve body fails unexpectedly, the replacement cost and related losses will be huge. It meets the requirements of high fatigue strength and excellent impact toughness, that is, it has a certain resistance to fracture and crack growth under the specified medium temperature and pressure.

At present, conventional valve bodies are mainly forged steel parts or welded parts; forged steel parts are only used to produce valve bodies with small diameters or special working conditions, and the production cost is relatively high; welded parts are mostly used to manufacture high-pressure valves, but they cannot be disassembled. And the production cost is high; replace forged steel parts and welded parts with ductile iron, because nodular cast iron has the characteristics of low production cost, formability not affected by part structure, excellent comprehensive mechanical properties, etc., it has been used to cast some structures with complex structures and high strength. , Parts with high toughness requirements

However, QT450-10 has been used to replace general-purpose forged steel parts and welded parts for some conventional butterfly valve body materials for hydroelectric generator sets, which effectively reduces production costs, shortens production cycles, and creates considerable economic benefits; while for some The weight of the butterfly valve in the hydroelectric generator set is more than ten tons or even higher, the main wall thickness exceeds 100mm, and the maximum size is 5532mm. Distortion, reduction in the number of graphite balls, shrinkage porosity and other defects, and it is difficult to meet the requirements of ultrasonic flaw detection and magnetic particle flaw detection