A method of controlling 1/2r carbon segregation of large round billet of medium carbon crmo steel

Abstract

A method for controlling the 1 / 2R carbon segregation of medium-carbon CrMo steel large round billets. According to the specific process parameters, the "solidification path" model is established as a tool for optimizing parameters. The ratio of mixed crystal area is controlled to determine the superheat of molten steel, and the electromagnetic stirring intensity of the mold is controlled. To prevent the emergence of "hard" stirring mode, the "solidification path" method is used to determine the cooling method, and the secondary cooling electromagnetic stirring is adjusted to ensure the stirring effect. The method of the invention can quickly determine the specific parameters for controlling the 1 / 2R carbon segregation of the medium carbon CrMo steel large round billet under certain equipment and process conditions, thereby avoiding the waste caused by a large number of industrial tests and shortening the test cycle.

Description

technical field [0001] The invention belongs to the technical field of metallurgy and relates to a method for controlling 1 / 2R carbon segregation of a large round billet of medium-carbon CrMo steel. Background technique [0002] The medium-carbon CrMo steel represented by SAE4130-4140 has the advantages of stable composition, low harmful elements, high steel purity, and few surface defects. When used, the heat treatment quality is stable and the hardness is uniform. It is used in high-strength fasteners for wind power and engines. It is widely used in high-strength fasteners and mold industries. Taking SAE4140 as an example, SAE4140 belongs to the American standard (ASTMA29 / A 29M-05), which is equivalent to the Japanese standard (JIS G4053-2008) SCM440 and the Chinese standard 42CrMo. SAE4140 is much stricter than China's 42CrMo standard in terms of composition and performance of finished products, among which the most prominent is the control of finished carbon. The Chines...

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Problems solved by technology

[0003] Many metallurgists are devoted to the research on the formation mechanism and control measures of carbon segregation at the 1 / 2R position of the large round billet continuous caster. Although the mechanism for the formation of this carbon segregation has long been clarified, the progress in the control of carbon segregation at the 1 / 2R position is slow. , there is almost no effective method to fundamentally suppress this segregation

At present, in terms of control methods, there is some consensus. For example, in terms of reducing carbon content targets, preventing carbon increase, stable pouring, and soft argon blowing, many companies implement these measures well, but they cannot effectively control 1 / Carbon segregation at the 2R position

Some control methods are used by many companies, but there are disputes. For example, some think that low superheat pouring is conducive to expanding equiaxed crystals, thereby reducing segregation; thereby reducing segregation

Some control methods have always been vaguely understood and their use limits are not clear. For example, although electromagnetic stirring for crystallizers and secondary cooling electromagnetic stirring have the effect of controlling segregation, the adjustment directions of different enterprises vary widely.

[0004] So far, in the large-scale production of the factory, the search for the influence of various control parameters on the carbon segregation at the 1 / 2R position is still concentrated in the industrial test stage, which costs a lot of money

Especially in the screening and coordination of multiple control parameters, the experimental exploration cycle is long and difficult to implement

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