A spheroidal graphite cast iron having an excellent impact strength at low temperature and a method for producing the same are provided. The present disclosure relates to the spheroidal graphite cast iron comprising: C: 3.5 mass % to 4.2 mass %; Si: 2.0 mass % to 2.8 mass %; Mn: 0.2 mass % to 0.4 mass %; Cu: 0.1 mass % to 0.7 mass %; Mg: 0.02 mass % to 0.06 mass %; Cr: 0.01 mass % to 0.15 mass %; and the balance: Fe and inevitable impurities, wherein Mn+Cr+Cu is 0.431 mass % to 1.090 mass %, a graphite nodule count is 230/mm.sup.2 or less, and a pearlite fraction is 30% to 85%.

A high rigid spheroidal graphite cast iron, comprising: 2.0 mass % to less than 2.7 mass % or more than 3.0 mass % to less than 3.6 mass % of C, 1.5 to 3.0 mass % of Si, 1.0% or less of Mn, 1.0 mass % or less of Cu, 0.02 to 0.07 mass % of Mg and the residual Fe and inevitable impurities, wherein a carbon equivalent (a CE value) calculated by the mathematical expression (1): CE=C (mass %)+Si (mass %)/3 in terms of C and Si contents is 2.8 to 3.2% within a first range from 2.0 mass % to less than 2.7 mass % of C and is 3.6 to 4.2% within a second range from more than 3.0 mass % to less than 3.6 mass % of C, and the Young's modulus is 170 GPa or more.

A high rigid spheroidal graphite cast iron, comprising: 2.0 mass % to less than 2.7 mass % or more than 3.0 mass % to less than 3.6 mass % of C, 1.5 to 3.0 mass % of Si, 1.0% or less of Mn, 1.0 mass % or less of Cu, 0.02 to 0.07 mass % of Mg and the residual Fe and inevitable impurities, wherein a carbon equivalent (a CE value) calculated by the mathematical expression (1): CE=C (mass %)+Si (mass %)/3 in terms of C and Si contents is 2.8 to 3.2% within a first range from 2.0 mass % to less than 2.7 mass % of C and is 3.6 to 4.2% within a second range from more than 3.0 mass % to less than 3.6 mass % of C, and the Young's modulus is 170 GPa or more.

A method of manufacturing a cam piece for a continuously variable valve duration and a cam piece manufactured therefrom, and more particularly, to material and heat treatment conditions of a cam piece, may include manufacturing a cam piece by casting; heating the cam piece; maintaining a heating temperature; and salt-bathing the cam piece, in which the cam piece includes 3.2 to 4.2 wt % of carbon (C), 2.2 to 3.4 wt % of silicon (Si), and the balance iron (Fe), and may have a carbon equivalent value of 4.4 to 4.6.

A method of manufacturing a cam piece for a continuously variable valve duration and a cam piece manufactured therefrom, and more particularly, to material and heat treatment conditions of a cam piece, may include manufacturing a cam piece by casting; heating the cam piece; maintaining a heating temperature; and salt-bathing the cam piece, in which the cam piece includes 3.2 to 4.2 wt % of carbon (C), 2.2 to 3.4 wt % of silicon (Si), and the balance iron (Fe), and may have a carbon equivalent value of 4.4 to 4.6.

A cylinder liner of the present invention is a cylinder liner mounted on a cylinder block and formed of flaky graphite cast iron, at least a nitrided layer is provided on an inner periphery of the cylinder liner, and a cross hatching section is formed on the inner periphery, a roughness curve of the inner periphery has a plateau honing shape, a ten-point average roughness Rz of the inner periphery pursuant to JIS B0601:1982 is 4.0 μm or less, and an average value of an area ratio of pits generated in the inner periphery is 8% or less.

A cylinder liner of the present invention is a cylinder liner mounted on a cylinder block and formed of flaky graphite cast iron, at least a nitrided layer is provided on an inner periphery of the cylinder liner, and a cross hatching section is formed on the inner periphery, a roughness curve of the inner periphery has a plateau honing shape, a ten-point average roughness Rz of the inner periphery pursuant to JIS B0601:1982 is 4.0 μm or less, and an average value of an area ratio of pits generated in the inner periphery is 8% or less.

Casting of iron or steel is performed by assembling a charge (1) of plate-like charge elements (1a, 1b, 1c . . . ) with known compositions and dimensions by placing them on top of each other, and of an alloying component entity (2) with known composition, such as alloying component pieces or an alloying component cartridge, by means of which the composition of the charge is balanced to the desired precise composition. The charge is melted in a furnace (5) and cast to form a casting with an exactly known composition.

Casting of iron or steel is performed by assembling a charge (1) of plate-like charge elements (1a, 1b, 1c . . . ) with known compositions and dimensions by placing them on top of each other, and of an alloying component entity (2) with known composition, such as alloying component pieces or an alloying component cartridge, by means of which the composition of the charge is balanced to the desired precise composition. The charge is melted in a furnace (5) and cast to form a casting with an exactly known composition.

A ferrosilicon inoculant for gray cast iron containing between 0.1 to 10% by weight strontium, less than 0.35% by weight calcium, 1.5 to 10% by weight aluminum and 0.1 to 15% zirconium, The inoculant, method for producing the inoculant, method for inoculating the melt and a gray cast iron inoculated with the inoculant are covered.