The present invention refers to a vermicular cast iron alloy specially designed for blocks and heads of internal combustion engines that have special requirements for mechanical strength and machinability; said vermicular alloy has a microstructure that results in high values of mechanical properties, such as a minimum strength limit of 500 Mpa, a minimum yield limit of 350 MPa, along with good machinability; also, wherein the ferritization factor must be such that it is between 3.88 and 5.48. This set of properties makes it possible to design new engine blocks and heads with complex geometry, high mechanical properties, without compromising machinability, making it attractive both from a technical and economic point of view.

A spheroidal graphite cast iron meeting N.sub.(5-)≥250, N.sub.(5-20)/N.sub.(5-)≥0.6, and N.sub.(30-)/N.sub.(5-)≤0.2, wherein N.sub.(5-) represents the number (/mm.sup.2) of graphite particles having equivalent-circle diameters of 5 μm or more, N.sub.(5-20) represents the number (/mm.sup.2) of graphite particles having equivalent-circle diameters of 5 μm or more and less than 20 μm, and N.sub.(30-) represents the number (/mm.sup.2) of graphite particles having equivalent-circle diameters of 30 μm or more, among graphite particles observed in an arbitrary cross section of at least 1 mm.sup.2.

A spheroidal graphite cast iron meeting N.sub.(5-)≥250, N.sub.(5-20)/N.sub.(5-)≥0.6, and N.sub.(30-)/N.sub.(5-)≤0.2, wherein N.sub.(5-) represents the number (/mm.sup.2) of graphite particles having equivalent-circle diameters of 5 μm or more, N.sub.(5-20) represents the number (/mm.sup.2) of graphite particles having equivalent-circle diameters of 5 μm or more and less than 20 μm, and N.sub.(30-) represents the number (/mm.sup.2) of graphite particles having equivalent-circle diameters of 30 μm or more, among graphite particles observed in an arbitrary cross section of at least 1 mm.sup.2.

Bearing bushings which are exposed to highly elevated temperatures during operation, corresponding high-temperature-resistant bearing bushings and exhaust-gas turbochargers having at least one such bearing bushing, include an iron material having a material composition which, apart from iron, has at least carbon, silicon, manganese, nickel, chromium, molybdenum and tungsten alloy constituents in certain amounts. This material composition ensures sufficient temperature resistance and self-lubricating properties with simultaneously good machining properties and a moderate price.

Bearing bushings which are exposed to highly elevated temperatures during operation, corresponding high-temperature-resistant bearing bushings and exhaust-gas turbochargers having at least one such bearing bushing, include an iron material having a material composition which, apart from iron, has at least carbon, silicon, manganese, nickel, chromium, molybdenum and tungsten alloy constituents in certain amounts. This material composition ensures sufficient temperature resistance and self-lubricating properties with simultaneously good machining properties and a moderate price.

A self-lubricating rolling bearing is provided. The chemical compositions in the inner rings and the outer rings of bearing are 3.4-3.7% C, 2.7-2.9% Si, 0.3-0.5% Mn, 0.3-0.5% Cr, ≤0.05% S, ≤0.05% P, 0.03-0.045% Residual Mg, and the remainder Fe. The total percent of the chemical compositions is 100%. The material for the inner and outer rings of the rolling bearing introduced in the invention is austempered ductile iron (ADI). In the microstructure of ADI, the diameter of the graphite nodules is less than 0.02 mm, the number of graphite spheres per square millimeter is more than 400, and the microstructure of the metal matrix in the ADI can be showed clearly only when it is observed on the microscope with a magnification more than 500. Eventually, the self-lubricating rolling bearings are made from the ADI.

A self-lubricating rolling bearing is provided. The chemical compositions in the inner rings and the outer rings of bearing are 3.4-3.7% C, 2.7-2.9% Si, 0.3-0.5% Mn, 0.3-0.5% Cr, ≤0.05% S, ≤0.05% P, 0.03-0.045% Residual Mg, and the remainder Fe. The total percent of the chemical compositions is 100%. The material for the inner and outer rings of the rolling bearing introduced in the invention is austempered ductile iron (ADI). In the microstructure of ADI, the diameter of the graphite nodules is less than 0.02 mm, the number of graphite spheres per square millimeter is more than 400, and the microstructure of the metal matrix in the ADI can be showed clearly only when it is observed on the microscope with a magnification more than 500. Eventually, the self-lubricating rolling bearings are made from the ADI.

A composite roll for rolling comprising an outer layer and an inner layer integrally fused to each other; the outer layer being made of an Fe-based alloy comprising by mass 1-3% of C, 0.3-3% of Si, 0.1-3% of Mn, 0.1-5% of Ni, 1-7% of Cr, 1-8% of Mo, 4-7% of V, 0.005-0.15% of N, and 0.05-0.2% of B; the inner layer being made of graphite cast iron comprising by mass 2.4-3.6% of C, 1.5-3.5% of Si, 0.1-2% of Mn, 0.1-2% of Ni, less than 0.7% of Cr, less than 0.7% of Mo, 0.05-1% of V, and 0.01-0.1% of Mg; the inner layer comprising a core portion fused to the outer layer, and shaft portions integrally extending from both ends of the core portion; at least one of the shaft portions containing 200/cm.sup.2 or more of hard MC carbides having circle-equivalent diameters of 5 μm or more.

The present invention relates to a diesel engine piston which is cast in one piece and which consists of almost fully pearlitic cast iron with spheroidal graphite as the piston material. Moreover, the present invention relates to the use of such a diesel engine piston for “light vehicle” diesel engines, “heavy duty” diesel engines and “large bore” diesel engines.

An inoculant for manufacturing cast iron with lamellar, compacted or spheroidal graphite is disclosed. The inoculant has a particulate ferrosilicon alloy having 40 and 80% by weight of silicon, 0.5-5 wt % of calcium and/or strontium and/or barium, 0-10 wt % of rare earths, 0-5 wt % of magnesium, less than 5% by weight of aluminium, 0-10 wt % of manganese and/or zirconium, and the balance being iron, wherein the inoculant additionally contains 0.1-10 wt % of particulate bismuth oxide particles and optionally 0.1-10 wt % of one or more particulate metal sulphides and/or one or more particulate iron oxides, where the particulate bismuth oxide is mixed or blended with the ferrosilicon particles, or is simultaneously added to cast iron together with the particulate ferrosilicon particles.