Casting method for reducing macroscopic segregation of cast ingot

Abstract

Disclosed is a casting method for reducing macroscopic segregation of a cast ingot. The method is characterized in that real casting time tp of the cast ingot is controlled to meet the following requirement: 1 / 10t<tp<t, wherein t is the time needed by the cast ingot to solidify completely in a common casting technique. The method includes the following concrete steps: step1, obtaining the time t needed by the cast ingot to solidify completely in the common casting technique through experimental determination or numerical simulation, step2, casting the cast ingot in a casting mould by using a casting ladle, and step3, controlling the real casting time tp to meet the requirement by adjusting casting speeds or adjusting the size, the position and the number of holes of the casting ladle till casting is finished. The method has the advantages that the casting speeds are low, solute convection is reduced, and local solidification speeds are improved; therefore, the method is beneficial to grain refinement and suppression on the macroscopic segregation, and suitable for casting various cast ingots, especially large-sized cast ingots.

Description

technical field [0001] The invention relates to a steel ingot casting method, in particular to a casting method aimed at reducing the macro segregation of an ingot, and belongs to the technical field of metal thermal processing. Background technique [0002] Large forgings are the core components of the new generation of nuclear power, thermal power and other energy equipment. With the development of new energy construction, the demand for large forgings is increasing. Based on the idea of ​​"improving efficiency, reducing consumption, protecting the environment, and being safe and reliable", the new generation of nuclear power, thermal power and other equipment has put forward strict requirements for forgings such as "large-scale", "integrated" and "high-performance". Casting into ingots is the first link in the thermal processing of large forgings. The heaviest ingots exceed 600 tons, and the performance is required to remain stable for decades. Due to the huge size, the...

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Problems solved by technology

However, this method cannot control the position of the steel ball in the steel ingot; some scholars have proposed to add ventilation pipes at the bottom of the ingot mold and the middle and lower part of the ingot mold, and to strengthen external heat dissipation through compressed gas, such as the Chinese patents whose authorized announcement numbers are CN201223932Y and CN201231310Y , but the method described in the patent has no obvious effect on large ingots, because when the external heat dissipation conditions are good, the heat dissipation bottleneck of large ingots lies in the ingot itself; The composition of the bag: the bottom is higher than the normal level, the top is lower than the normal level, and the pouring interval of each bag is changed to suppress macrosegregation, such as "Numerical simulation of delayed pouring technique for a360t heavy steel ingot" by Li Dianzhong ("13th International Conference on Modeling of Casting, Welding and Advanced Solidification Processes (MCWASP), 2012, Vol33), this method can suppress macro segregation to a certain extent, but large ingots have a large amount of molten metal, and the metal flow between ladles is fused with macro segregation On the whole, it will still be very large, and there is no basis for the amount of pouring in each bag, and there is no theoretical basis for the time interval. At present, the effect is very little. Although the idea is reasonable to adjust the composition content in the solidified liquid phase, the liquid phase still occupies a large volume after the fusion of the two components due to the large size of the large ingot, so the subsequent solidification still remains Can produce large macrosegregation

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