Abstract: Disclosed is a high-strength bolt having a tensile strength of 1,200 N/mm2 or more and superior in delayed fracture resistance and relaxation resistance, prepared by wire-drawing a bolt steel containing the following elements: C: 0.5 to 1.0% (mass %, the same shall apply hereinafter), Si: 0.55 to 3%, Mn: 0.2 to 2%, P: 0.03% or less (but not 0%), S: 0.03% or less (but not 0%), and Al: 0.3% or less (but not 0%), and containing proeutectoid ferrite, proeutectoid cementite, bainite and martensite at a total areal rate of less than 20% and pearlite in balance; cold-heading the wire into a bolt shape; and then bluing the bolt in a temperature range of 100 to 500° C.

Abstract: A mechanical component 1 composed of a steel is surface-hardened by nitriding, and specifically has a surficial layer 2 raised in the surface hardness by the nitriding, and an inner portion 3 not affected by the nitriding and showing a nearly constant hardness. Vickers hardness of the inner portion 3 is adjusted to 190 to 260 HV, Vickers hardness of the surficial portion 2 measured at a reference position corresponded to a 50 ?m depth from the component surface is adjusted to 340 to 460 HV, and effective depth of hardened layer measured from the component surface 4, where a Vickers hardness of 270 HV is achieved, is adjusted to 0.3 mm or more. This makes it possible to provide a mechanical component which is composed of a steel and surface-hardened by nitriding, and is successfully improved in the strength and bending straightening property, and also to provide a method of fabricating the same.

Abstract: Material for a connecting rod for an internal combustion engine is carburized and quenched, a carburized layer formed on the bearing portion is ground until the portion which exhibits the maximum compressive residual stress, and a shot-peening processing is performed on the ground surface. The invention produces a bearing portion having surface characteristics in which maximum compressive residual stress is imparted, and therefore, remarkable improvement in the fatigue strength in the bearing portion can be obtained. Furthermore, a large number of concavities formed by the shot-peening processing can be efficiently employed as an oil reservoir, so that sliding properties and lubrication can be improved, and the occurrence of problems such as fretting corrosion, galling, and seize can also be solved, and the galling and problems of the seize can be prevented.

Abstract: A high-strength bolt having excellent delayed fracture resistance and stress relaxation resistance in addition to a tensile strength of 1200 N/mm2 or higher is disclosed. A steel material for the high-strength bolt includes C: 0.50 to 1.0% by mass (hereinafter, referred to simply as “%”), Si: 0.5% or less (not including 0%), Mn: 0.2 to 1%, P: 0.03% or less (including 0%) and S: 0.03% or less (including 0%). The steel material has pro-eutectoid ferrite, pro-eutectoid cementite, bainite and martensite structures at less than 20% in total and a pearlite structure as the remainder. The high-strength bolt is produced by drawing the steel material severely to obtain a steel wire, forming the steel wire into a bolt shape through a cold heading, and subjecting the shaped steel wire to a blueing treatment at a temperature within a range of 100 to 400° C.

Abstract: A high-strength bolt having excellent delayed fracture resistance and stress relaxation resistance in addition to a tensile strength of 1200 N/mm2 or higher is disclosed. A steel material for the high-strength bolt includes C: 0.50 to 1.0% by mass (hereinafter, referred to simply as “%”), Si: 0.5% or less (not including 0%), Mn: 0.2 to 1%, P: 0.03% or less (including 0%) and S: 0.03% or less (including 0%). The steel material has pro-eutectoid ferrite, pro-eutectoid cementite, bainite and martensite structures at less than 20% in total and a pearlite structure as the remainder. The high-strength bolt is produced by drawing the steel material severely to obtain a steel wire, forming the steel wire into a bolt shape through a cold heading, and subjecting the shaped steel wire to a blueing treatment at a temperature within a range of 100 to 400 ° C.

Abstract: A non-heat treated soft-nitrided steel part respective contents of C, Si, Mn, P, Cr, Ti, V, N, Al, Pb, S and Ca of which are in specific ranges and which satisfies the following formulas (1) to (3). This part can be produced in a process of hot working, machining and soft-nitriding without any prior heat treatment, and has superior properties such as high fatigue strength and wear resistance. Fn1=−141.5(C %)−19.6(Mn %)+1280(N %)+95.6≦60  (1) Fn2=−103.8(C %)+59.1(Mn %)+850.4(N %)+360.9≧350  (2) Fn3=−13.4(C %)−3.45(Mn %)+112.7(N %)+13.

Abstract: In an engine for a vehicle including a bearing cap integral type oil pan which has a plurality of bearing cap sections integrally provided thereon and which is integrally coupled to a cylinder block, connecting bolts are screwed into the bearing cap sections from the cylinder block to integrally couple the cylinder block and the oil pan to each other. An oil pan chamber, which is an as-cast bore made by drawing a die in an axial direction of a crankshaft, is defined to extend continuously in the axial direction of the crankshaft between the bearing cap sections and a bottom wall of the oil pan. Thus, the oil pan can be produced simply, at a low cost, by a casting process and moreover, it is possible to reduce the weight and size of the oil pan and increase the rigidity of the oil pan.