Manufacturing method of ultra-large-section low-temperature high-toughness ferrite spheroidal graphite iron casting

Abstract

The invention discloses a manufacturing method of an ultra-large-section low-temperature high-toughness ferrite spheroidal graphite iron casting. The spheroidal graphite iron casting is more than 50 tons in weight, is 400mm or more in wall thickness, and is prepared from the following components: 3.6 to 3.7 percent of C, 0.9 to 1.0 percent of Si<original>, 1.9 to 2.0 percent of Si<final>, less than or equal to 0.1 percent of Mn, less than or equal to 0.03 percent of P, less than or equal to 0.01 percent of S, 0.03 to 0.08 percent of Mg, 0.01 to 0.02 percent of RE, 0.6 to 0.8 percent of Ni and0.003 to 0.005 percent of Sb. During manufacturing, the technical measures of ''high-temperature pure base iron melt, water-cooled metal mold, cold iron, spheroidizing agent 5800, compound strengthening inoculation, alloying and low-temperature box beating'' are adopted, so that the prepared ultra-large-section low-temperature high-toughness ferrite spheroidal graphite iron casting can meet the quality standard of a spheroidal graphite iron casting of which the license number is QT400-18, and can meet the technical requirements of ultra-large-section spheroidal graphite iron castings applied to wind power, nuclear power and the like.

Description

technical field [0001] The invention relates to a method for manufacturing ductile iron parts, in particular to a method for manufacturing an ultra-large cross-section, low-temperature, high-toughness ferrite nodular iron casting with a weight exceeding 50 tons and a wall thickness of up to 400 mm. Background technique [0002] Low-temperature and high-toughness ferritic ductile iron castings with circular super-large cross-section are increasingly widely used in wind power, nuclear power and other fields (such as 100-ton ductile iron nuclear waste tanks, wind power hubs, bases, etc.), but their quality has also been raised. higher requirement. In order to obtain low-temperature impact properties, elongation and fracture toughness that meet the requirements, it is necessary to ensure that the casting has a ferrite matrix, and the spheroidization is good, and distorted graphite such as fragments cannot appear. Compared with normal temperature ferritic nodular cast iron, low ...

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Problems solved by technology

Although my country has achieved certain results in the development of low-temperature ferritic ductile iron, most domestic manufacturers still have not mastered the key technology. Compared with foreign countries, there is still a big gap in market demand: in the 1980s, the German Siempelkamp Company produced a ductile iron pressure frame with a weight of 160t and a maximum wall thickness of 630mm and a spent fuel ductile iron container with a weight of 130t and a wall thickness of 500mm; The French Thystem company developed and produced a TN1300 spent fuel ductile iron container with a weight of 115t and a wall thickness of 400mm. Japan also developed a 100t, 425mm wall thickness 100-ton ductile iron container in 1998. There is still a blank in the manufacture of iron castings

[0003] At present, the main problems in the manufacture of super-large-section low-temperature high-toughness ductile iron are: large-section ductile iron parts are large in size, heavy in weight, thick in wall, large in heat capacity during casting, and slow in solidification, which can easily cause spheroidization and inoculation decline. , which leads to changes in the structure of the casting, especially in the final solidification area of ​​the casting, which is mainly manifested in the large diameter of graphite balls, the reduction of the number of graphite balls, the floating of graphite, the distortion of graphite balls, and the formation of various non-spherical graphite (mainly Pseudo-flaky, worm-like, burst-like and fragmented); at the same time, due to the redistribution of solute elements during solidification, there will also be a series of problems such as serious composition segregation, intergranular carbides, and anti-white holes. The mechanical properties of cast iron become worse, especially the elongation and plasticity are significantly reduced, which restricts the popularization and use of large-section ductile iron

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