Cast iron billet excelling in workability and process for producing the same

Abstract

The present invention provides tough cast iron and cast iron semi-finished products excellent in workability without heat treatment requiring massive heat energy and long time and a method of production enabling these to be efficiently produced, that is, cast iron of ingredients of white cast iron where particles of spheroidal graphite or flattened graphite are dispersed, cast iron where the ingredients of the white cast iron satisfy, by wt%, (%C)<=4.3-(%Si) DIVIDED 3 and C>=1.7% and where the particles of spheroidal graphite are dispersed at a density of 50 particles / mm<2> or more, or cast iron where the particles of flattened graphite have a width of 0.4 mm or less and a length of 50 mm or less.

Description

technical field [0001] The present invention relates to cast iron excellent in workability, cast iron sheet and a manufacturing method thereof. Background technique [0002] As tough cast iron, there are nodular cast iron obtained by adding graphite spheroidizing agents such as Mg, Ca, and Ce, and graphite spheroidizing treatment, or contracted vermicular graphite cast iron (Compactoba-Mikura鋳鉄) (hereinafter referred to as C / V cast iron) , In addition, there are malleable cast iron obtained by heat treatment of white iron obtained by white casting. [0003] In the above-mentioned C / V cast iron, the graphite does not reach a spherical shape, but exists in the form of graphite such as an intermediate state of a block. In addition, malleable cast iron is an important material for machine manufacturing because it has excellent castability and, by heat treatment, it has excellent ductility and toughness like steel. The malleable cast iron can be classified into white-heart mall...

AI Technical Summary

Problems solved by technology

[0009] In contrast, JP-A-7-138636 discloses a short-term graphitization treatment method, but the precipitated graphite after the treatment is not completely spheroidized

In addition, in rolled cast iron obtained by rolling ductile cast iron or malleable cast iron, since graphite is formed into flakes and distributed in layers during rolling, its workability will deteriorate.

[0010] Furthermore, in the continuous casting of ordinary cast iron, for the purpose of preventing chilling, etc., graphite molds are used, but since the solid-liquid coexistence region of white cast iron is relatively large, continuous casting is difficult, as disclosed in US Patent No. 4074747 This operation is almost never done except for a few

[0011] In addition, as a method of manufacturing a strong thin cast iron plate, we have also considered white casting in a thin plate shape with a twin-roll casting machine as shown in Japanese Patent No. 3130670, and then heat-treating it. Thin cast iron plates made of malleable cast iron are produced, but in this case, as in the case of malleable cast iron, there is a problem of insufficient workability due to the formation of massive graphite and insufficient spheroidization of graphite.

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