Provided is a method capable of producing a plated black heart malleable cast iron member having a plating layer with excellent adhesiveness to a black heart malleable cast iron member, while having less burden on the environment, compared to conventional methods.

Provided is a method capable of producing a plated black heart malleable cast iron member having a plating layer with excellent adhesiveness to a black heart malleable cast iron member, while having less burden on the environment, compared to conventional methods.

The black heart malleable cast iron according to the present embodiment comprises a matrix of ferrite and lump graphite included in the matrix, the black heart malleable cast iron comprising 50 ppm or more and 100 ppm or less of boron, and 65 ppm or more and 200 ppm or less of nitrogen in a mass ratio, wherein a grain size of the matrix is 8.0 or more and 10.0 or less in terms of grain size number, numerically determined by comparison between a metallographic photograph and a standard grain size chart.

The black heart malleable cast iron according to the present embodiment comprises a matrix of ferrite and lump graphite included in the matrix, the black heart malleable cast iron comprising 50 ppm or more and 100 ppm or less of boron, and 65 ppm or more and 200 ppm or less of nitrogen in a mass ratio, wherein a grain size of the matrix is 8.0 or more and 10.0 or less in terms of grain size number, numerically determined by comparison between a metallographic photograph and a standard grain size chart.

A centrifugally cast composite roll for hot rolling comprising an outer layer made of an Fe-based alloy having a chemical composition comprising by mass 2.6-3.6% of C, 0.1-3% of Si, 0.3-2% of Mn, 2.3-5.5% of Ni, 0.5-3.2% of Cr, 0.3-1.6% of Mo, 1.8-3.4% of V, and 0.7-2.4% of Nb, 1.4 ≤V/Nb ≤2.7, a V equivalent (Veq=V+0.55 Nb) being 2.60-4% by mass, and the balance being Fe and impurities, and an inner layer made of an iron-based alloy and integrally fused to the outer layer.

The present disclosure provides a method for controlling an amount of silicon added to ductile cast iron, a method for casting ductile cast iron, and a cast product, which relate to the technical fields of metallurgical and cast iron alloys. The method for controlling an amount of silicon added to ductile cast iron includes smelting ductile cast iron using scrap steel as a raw material. After the scrap steel is melted into molten iron, a copper alloy is added so that the molten iron has a copper equivalent of 0.8% to 1.0%, wherein the copper equivalent is controlled by formula (II). Then, ferrosilicon is added so that the content of silicon added to the molten iron satisfies formula (I).

The present disclosure provides a method for controlling an amount of silicon added to ductile cast iron, a method for casting ductile cast iron, and a cast product, which relate to the technical fields of metallurgical and cast iron alloys. The method for controlling an amount of silicon added to ductile cast iron includes smelting ductile cast iron using scrap steel as a raw material. After the scrap steel is melted into molten iron, a copper alloy is added so that the molten iron has a copper equivalent of 0.8% to 1.0%, wherein the copper equivalent is controlled by formula (II). Then, ferrosilicon is added so that the content of silicon added to the molten iron satisfies formula (I).

A ductile iron composition including, by weight: about 3.4% to about 4.0% Si; about 3.0% to about 3.5% C; about 0.5% to about 1.0% Cr; about 0.02% to about 0.05% Mo; up to about 0.01% S; up to about 0.5% Mn; and balance iron and incidental impurities.

The composition has a a ferritic body center cubic microstructure and has a graphite nodule density of greater than 100 per mm.sup.2. A method for forming a ductile iron composition is also disclosed.

Provided is a black heart malleable cast iron and a method for manufacturing the same which can significantly shorten the time required for graphitization, as compared with the prior art. The black heart malleable cast iron includes a matrix of ferrite and lump graphite included in the matrix, and includes at least one selected from the group consisting of (i) 0.0050% by mass or more and 0.15% by mass or less of bismuth and 0.020% by mass or more of manganese, and (ii) 0.0050% by mass or more and 1.0% by mass or less of aluminum and 0.0050% by mass or more of nitrogen. In addition, the grain size of the matrix is 8.0 or more and 10.0 or less in terms of grain size number, numerically determined by comparison between a metallographic photograph of the matrix and a standard grain size chart.

Provided is a black heart malleable cast iron and a method for manufacturing the same which can significantly shorten the time required for graphitization, as compared with the prior art. The black heart malleable cast iron includes a matrix of ferrite and lump graphite included in the matrix, and includes at least one selected from the group consisting of (i) 0.0050% by mass or more and 0.15% by mass or less of bismuth and 0.020% by mass or more of manganese, and (ii) 0.0050% by mass or more and 1.0% by mass or less of aluminum and 0.0050% by mass or more of nitrogen. In addition, the grain size of the matrix is 8.0 or more and 10.0 or less in terms of grain size number, numerically determined by comparison between a metallographic photograph of the matrix and a standard grain size chart.