Method for preventing nodular cast iron roller core from loosening

Abstract

The invention discloses a method for preventing a nodular cast iron roller core from loosening, and belongs to the technical field of metallurgy. The production process comprises the working procedures of smelting, molten iron modification treatment, pouring, heat preservation and heat treatment. In the heat treatment process, a high-temperature normalizing and two-stage destressing annealing heat treatment process is adopted, the normalizing temperature is 970-990 DEG C, and the normalizing time is 15-17 hours; the first-stage annealing temperature is 515-535 DEG C, and the heat preservation time is 11-13 hours; and the second-stage annealing temperature is 550-570 DEG C, and the heat preservation time is 11-13 hours. The problem that shrinkage cavities and shrinkage porosity are generated in the centrifugal composite nodular cast iron roller core is solved, the attenuation phenomenon of ultrasonic flaw detection is avoided, and the use requirements of users are met.

Description

technical field [0001] The invention belongs to the technical field of metallurgy, and in particular relates to a method for preventing looseness of the core of a ductile iron roll. Background technique [0002] The quality problems of shrinkage and porosity are often encountered in the casting production of ductile iron rolls, especially the fine porosity inside the roll body. The ultrasonic flaw detection test shows the attenuation of the bottom wave, that is, the reflected wave of the bottom wave is less than 10% in the non-destructive testing test, which exceeds the national standard. , this loose defect will affect the rigidity and strength of the rolls and other performance, and will also cause the rolls used on the production line to break, resulting in a scrap rate of up to 30% in some roll casting companies. Therefore, it is urgent in the industry to develop a kind of The solution to prevent loose core of centrifugal composite roll. [0003] In recent years, althou...

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Problems solved by technology

[0002] The quality problems of shrinkage and porosity are often encountered in the casting production of ductile iron rolls, especially the fine porosity inside the roll body. The ultrasonic flaw detection test shows the attenuation of the bottom wave, that is, the bottom wave reflection wave of the non-destructive testing test is less than 10%, exceeding the national standard. , this kind of loose defect will affect the use performance such as rigidity and strength of the roll, and will also cause the roll breakage of the roll used on the production line, resulting in the rejection rate of some roll foundry enterprises as high as 30%. Solution to prevent loose core of centrifugal composite roll

[0003] In recent years, although various large-scale roll enterprises at home and abroad have adopted measures such as changing the pouring method, adjusting the solidification sequence of molten iron, and increasing the amount of molten iron at the riser to solve the bottom wave attenuation problem caused by the loose core of the centrifugal roll roll, they have not fundamentally solved it effectively. , still cannot avoid the problem of bottom wave attenuation

[0004] Since the above-mentioned measures are to increase the fluidity of molten iron at the macro level and delay the solidification of molten iron to facilitate feeding and eliminate porosity, but for rolls with long roll bodies, especially centrifugal composite rolls, due to the multi-layer centrifugal layer material and the core Combined, the centrifuge layer and the core interact thermally with each other, which has complex temperature field and solidification characteristics, resulting in complex and changeable solidification sequence of molten iron. Therefore, conventional macroscopic methods of simply improving the fluidity of molten iron and delaying solidification are not effective. solve this looseness

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