A forged component having a chemical composition including, by mass %, C: 0.30 to 0.45%, Si: 0.05 to 0.35%, Mn: 0.50 to 0.90%, P: 0.030 to 0.070%, S: 0.040 to 0.070%, Cr: 0.01 to 0.50%, Al: 0.001 to 0.050%, V: 0.25 to 0.35%, Ca: 0 to 0.0100%, N: 0.0150% or less, and the balance being Fe and unavoidable impurities, and satisfying formula 1. Metal structure is a ferrite pearlite structure, and a ferrite area ratio is 30% or more. Vickers hardness is in the range of 320 to 380 HV. 0.2% yield strength is 800 MPa or more. A Charpy V-notch impact value is in the range of 7 to 15 J/cm.sup.2.

A method for manufacturing a machine component includes forming a non-linear break notch in a workpiece, freezing the workpiece, and snapping the frozen workpiece apart along the non-linear break notch.

According to a method for production of a fracture-split connecting rod, a connecting rod having one large and one small connecting-rod eye is introduced into a holding jig and therein the connecting rod is fracture-split in the region of the large connecting-rod eye, so that the connecting rod is subdivided into a rod part and a cap part, and then the rod part and the cap part are removed from the holding jig once again, wherein the rod part and the cap part are clamped together with a clamping element, especially before they are removed as a whole from the holding jig.

A connecting rod manufacturing method includes: forming, in an inner circumferential surface of a through-hole formed at an end of the connecting rod, a plurality of first holes as fracture start portions such that the first holes are arrayed in an axial direction of the through-hole and extend in a first direction; forming a plurality of second holes as the fracture start portions, each between adjacent ones of the first holes, such that the second holes are arrayed in the axial direction and extend in a second direction different from the first direction relative to the first holes; and fracture-splitting the end of the connecting rod into a rod part and a cap part using the fracture start portions as start points.

A manufacturing method for a connecting rod includes applying a tensile load to an end portion of the connecting rod as precompression in a cross direction that intersects with a longitudinal direction, the end portion being an longitudinal end portion of the connecting rod and having a through-hole, and fracture splitting the end portion into a rod portion and a cap portion by applying a tensile load to the end portion in the longitudinal direction in a state where the precompression is applied to the end portion.

A connecting rod manufacturing method includes: forming, in an inner circumferential surface of a through-hole formed at an end of the connecting rod, a plurality of first holes as fracture start portions such that the first holes are arrayed in an axial direction of the through-hole and extend in a first direction; forming a plurality of second holes as the fracture start portions, each between adjacent ones of the first holes, such that the second holes are arrayed in the axial direction and extend in a second direction different from the first direction relative to the first holes; and fracture-splitting the end of the connecting rod into a rod part and a cap part using the fracture start portions as start points.

A connecting rod for connecting between a crankshaft and a piston, includes a small end with a cylindrical hole adapted to for receiving a piston pin, a big end having a crank pin bore adapted for receiving a crank pin of a crankshaft and a stem portion extends between the small end and big end. The stem portion can have an I-beam cross-section with a pair of legs and a web extending between the pair of legs. The web includes oppositely facing surfaces defining a thickness that is less than a thickness of the pair of legs. The web includes at least one grooved/recessed portion that is recessed relative to the oppositely facing surfaces of the web.

A connecting rod for connecting between a crankshaft and a piston, includes a small end with a cylindrical hole adapted to for receiving a piston pin, a big end having a crank pin bore adapted for receiving a crank pin of a crankshaft and a stem portion extends between the small end and big end. The stem portion can have an I-beam cross-section with a pair of legs and a web extending between the pair of legs. The web includes oppositely facing surfaces defining a thickness that is less than a thickness of the pair of legs. The web includes at least one grooved/recessed portion that is recessed relative to the oppositely facing surfaces of the web.

Provided is a connecting rod which can be manufactured without increasing the cost, and is provided with an effectively strengthened rod portion. The rod portion includes a pair of ribs (21) extending in parallel to each other in cross sectional view, and a web (22) connected between substantially vertically middle parts of the ribs. Each rib includes a rib root portion (23) located in a vertically central part thereof in cross sectional view, and a pair of rib tip portions (24) located at both vertical ends thereof, and each rib tip portion has a higher hardness than the web by 40 HV or more, and the rib root portion has a higher hardness than the web by 30 HV or more.

After a connecting rod for an engine is formed, it is broken or fractured at a fracture point to allow the connecting rod to assemble around a portion of a crankshaft. However, before fracturing the connecting rod, the connecting rod is provided with a layer of paint across the eventual fracture point such that when the connecting rod is fractured the paint extends across both sides of the fracture point. Also before fracturing the connecting rod, serial numbers or symbols are etched into the paint on either side of the eventual fracture point. These serial numbers are unique to that connecting rod, and have similar indicia on either side of the connecting rod. The combination of the paint and serial numbers increase the ability of an assembly worker to assure matching parts of an original connecting rod are re-attached during assembly about the crankshaft.