The invention relates to a method of heat treating a cast iron having graphite particles, in particular a cast iron having graphite nodules with a substantially spherical geometry. The method comprises the step of subjecting the cast iron to a first austenitizing temperature, in order to obtain a cast iron having an austenite matrix with a substantially homogeneous carbon content. Subsequently, at least part of the cast iron is subjected to at least a second, different austenitizing temperature in order to change, in at least part of the cast iron, the carbon concentration in a part of the matrix surrounding the (spherical) geometry of the graphite particles. The method yields improved controllability on strength properties characteristics for cast irons including malleable irons, in particular for ductile iron.

The invention relates to a method of heat treating a cast iron having graphite particles, in particular a cast iron having graphite nodules with a substantially spherical geometry. The method comprises the step of subjecting the cast iron to a first austenitizing temperature, in order to obtain a cast iron having an austenite matrix with a substantially homogeneous carbon content. Subsequently, at least part of the cast iron is subjected to at least a second, different austenitizing temperature in order to change, in at least part of the cast iron, the carbon concentration in a part of the matrix surrounding the (spherical) geometry of the graphite particles. The method yields improved controllability on strength properties characteristics for cast irons including malleable irons, in particular for ductile iron.

A roll outer layer material contains small-size carbides having a circle equivalent diameter of 3 to 30 m in a number of 500 to 2500 pieces/mm.sup.2 and large-size carbides having a circle equivalent diameter of 50 m or more in a number of 20 pieces/mm.sup.2 or less, preferably having a chemical composition containing, by mass %, C: 2.4% or more and 2.9% or less, Si: 0.2% or more and 1.0% or less, Mn: 0.2% or more and 1.0% or less, Cr: 4.0% or more and 7.5% or less, Mo: 4.0% or more and 6.5% or less, V: 5.3% or more and 7.0% or less, Nb: 0.5% or more and 3.0% or less, and the balance being Fe and inevitable impurities, in which the contents of Cr, Mo, and V satisfy the relationship 1.5(Cr+Mo)/V2.4.

A seal ring comprising a chromium and boron containing cast iron alloy composition is disclosed. The cast iron alloy composition comprises each of boron, chromium and silicon in the following amounts: boron up to 1.5 wt. %; chromium from 8 to 14 wt. %; and silicon up to 3.0 wt. %. The seal ring may be produced by melting a cast iron composition further comprising the foregoing alloying elements; pouring the melted alloy into a mold; cooling the melted alloy to form a cast iron seal ring; and separating the cast iron seal ring from the mold. The seal ring is typically used in the undercarriage of earth-working machines, such as in the drive train or power train of such machines.

A grey cast iron may have within a ferrous matrix: an amount of carbon between 3.60 and 3.90% by weight; an amount of silicon between 1.40 and 1.90% by weight; an amount of titanium not higher than 0.10% by weight; an amount of boron between 0.04 and 0.07% by weight; an amount of vanadium between 0.07 and 0.14% by weight; an amount of manganese between 0.60% and 0.90% by weight; an amount of nickel not higher than 0.20% by weight; an amount of chromium not higher than 0.35% by weight; an amount of copper not higher than 0.35% by weight; an amount of phosphorus not higher than 0.10% by weight; an amount of sulphur not higher than 0.12% by weight; an amount of tin not higher than 0.10% by weight; an amount of molybdenum not higher than 0.10% by weight.

A grey cast iron may have within a ferrous matrix: an amount of carbon between 3.60 and 3.90% by weight; an amount of silicon between 1.40 and 1.90% by weight; an amount of titanium not higher than 0.10% by weight; an amount of boron between 0.04 and 0.07% by weight; an amount of vanadium between 0.07 and 0.14% by weight; an amount of manganese between 0.60% and 0.90% by weight; an amount of nickel not higher than 0.20% by weight; an amount of chromium not higher than 0.35% by weight; an amount of copper not higher than 0.35% by weight; an amount of phosphorus not higher than 0.10% by weight; an amount of sulphur not higher than 0.12% by weight; an amount of tin not higher than 0.10% by weight; an amount of molybdenum not higher than 0.10% by weight.

A nodular graphite cast iron, a method for fabricating a vane for a rotary compressor using nodular graphite cast iron, and a vane for a rotary compressor using the same are provided. The nodular graphite cast iron includes 3.4 wt % to 3.9 wt % of carbon (C), 2.0 wt % to 3.0 wt % of silicon (Si), 0.3 wt % to 1.0 wt % of manganese (Mn), 0.1 wt % to 1.0 wt % of chromium (Cr), 0.04 wt % to 0.15 wt % of titanium (Ti), less than 0.08 w % of phosphorus (P), less than 0.025 wt % of sulphur (S), 0.03 wt % to 0.05 wt % of magnesium (Mg), 0.02 wt % to 0.04 wt % of rare earth resource, iron (Fe) and impurities as the remnants, and includes a bainite matrix structure, nodular graphite, and 15 vol % to 35 vol % of carbide.

A nodular graphite cast iron, a method for fabricating a vane for a rotary compressor using nodular graphite cast iron, and a vane for a rotary compressor using the same are provided. The nodular graphite cast iron includes 3.4 wt % to 3.9 wt % of carbon (C), 2.0 wt % to 3.0 wt % of silicon (Si), 0.3 wt % to 1.0 wt % of manganese (Mn), 0.1 wt % to 1.0 wt % of chromium (Cr), 0.04 wt % to 0.15 wt % of titanium (Ti), less than 0.08 w % of phosphorus (P), less than 0.025 wt % of sulphur (S), 0.03 wt % to 0.05 wt % of magnesium (Mg), 0.02 wt % to 0.04 wt % of rare earth resource, iron (Fe) and impurities as the remnants, and includes a bainite matrix structure, nodular graphite, and 15 vol % to 35 vol % of carbide.

To provide a price-competitive compression ring having excellent thermal conductivity and thermal sag resistance, which can be used in a high-thermal-load environment of high-compression-ratio engines, steel identified by the material number of SKS93 in JIS G 4404 is used, and a piston ring wire is annealed before an oil-tempering treatment such that spheroidal cementite having an average particle size of 0.1-1.5 m is dispersed in a tempered martensite matrix.

Heat resistant spheroidal graphite cast iron having an improved high temperature tensile strength includes carbon (C) in a range of 3.2-3.4 wt %, silicon (Si) in a range of 4.3-4.8 wt %, manganese (Mn) in a range of 0.2-0.3 wt %, molybdenum (Mo) in a range of 0.8-1.0 wt %, vanadium (V) in a range of 0.4-0.6 wt %, chrome (Cr) in a range of 0.2-0.4 wt %, niobium (Nb) in a range of 0.2-0.4 wt %, inevitable impurities, and a remainder of iron (Fe) based on a total weight of the heat resistant spheroidal graphite cast iron. The heat resistant spheroidal graphite cast iron further includes barium (Ba) in a range of 0.0045-0.0075 wt %. A content ratio of chrome (Cr) and barium (Ba) (Cr/Ba) is in a range from about 26 to about 89.