A component with a component (1) of low-alloy steel and/or heat-treatable steel is provided, wherein the component (1) is at least partially coated with an aluminum diffusion layer (10) and an aluminum oxide layer (14) is applied to the aluminum diffusion layer (10), wherein the layer thickness of the aluminum diffusion layer (10) is 1-200 ?m, wherein the aluminum diffusion layer (10) has an aluminum content, based on the total weight of the aluminum diffusion layer, of 10 wt. % above the aluminum content of the steel up to a maximum concentration, wherein the aluminum content in the aluminum diffusion layer (10) increases in the direction of the interface (12) between the aluminum diffusion layer (10) and the aluminum oxide layer (14) from 10% by weight up to the maximum concentration, and wherein the maximum concentration is 11-60% by weight.

A high-strength bolt is provided that has high strength and excellent hydrogen embrittlement resistance characteristics. A bolt according to this invention has a chemical composition consisting of, in mass %, C: 0.22 to 0.40%, Si: 0.10 to 1.50%, Mn: 0.20 to less than 0.40%, P: 0.020% or less, S: 0.020% or less, Cr: 0.70 to 1.45%, Al: 0.005 to 0.060%, Ti: 0.010 to 0.045%, B: 0.0003 to 0.0040%, N: 0.0015 to 0.0080% and O: 0.0020% or less, with a balance being Fe and impurities, and satisfying Formula (1) and Formula (2), and with the high-strength bolt having a tensile strength of 1000 to 1300 MPa.

0.50C+Si/10+Mn/5+5Cr/220.85(1)

Si/Mn>1.0(2)

Where, a content (mass %) of a corresponding element is substituted for each symbol of an element in Formula (1) and Formula (2).

A rolled-thread bolt production method includes: forming a steel wire into a workpiece having a prescribed unthreaded-bolt shape; forming a threaded-portion on the workpiece through thread rolling; and performing shot blasting on an entire surface of the workpiece after forming the threaded-portion.

A method for processing a screw body, including a screw body providing step in which a screw body made of a hardenable steel is provided, a primary coating step, in which the screw body is coated with a primary coating that includes zinc, wherein the primary coating step follows the screw body providing step, and a tip hardening step, in which a tip region of the screw body, which is coated with the primary coating, is selectively heated, at least in part and with the ad-mission of oxygen, to a temperature required for hardening, characterized in that the tip hardening step follows the primary coating step. A screw that can be obtained using this method is also provided.

To provide a steel for high-strength bolts, which can exhibit the sufficient delayed fracture resistance under the severe environment, and also has excellent bolt formability. The steel for high-strength bolts of the present invention includes C: 0.10 to 0.30%; and Ni: 0.4 to 0.7%, with the chemical composition being appropriately adjust, and satisfies the following formulas (1) and (2):
0.85[C]+[Si]/7+[Mn]/5+[Ni]/20+[Cr]/9+[Mo]/21.3(1)
[C](0.07[Mo]+0.20[V])0.20(2).

A high-strength screw (1) includes a head (2) and a threaded portion (5) including a thread (6) and a thread end (9) facing away from the head (2) in an axial direction. The threaded portion (5) includes an unhardened portion (12) starting at the thread end (9) and extending in an axial direction. The unhardened portion (12) has a hardness being reduced compared to an axial middle portion (11) of the threaded portion (5).

A connecting rod for a variable compression internal combustion engine, the connecting rod including a crank bearing eye for connecting the connecting rod with a crank shaft; a connecting rod bearing eye configured to connect the connecting rod with a cylinder piston of the internal combustion; an eccentrical element adjustment arrangement configured to adjust an effective connecting rod length, wherein the eccentrical element adjustment arrangement includes an eccentrical element that cooperates with an eccentrical element lever, wherein the eccentrical element is configured to receive a wrist pin of the cylinder piston, wherein the eccentrical element adjustment arrangement includes at least one cylinder with a piston that is displaceably supported in a cylinder bore hole and connected with a support rod, wherein the eccentrical element lever includes two eccentrical element lever segments which are connected by at least one connecting bolt to which the support rod is pivotably connected.

To provide a wire rod for bolts that has excellent acid pickling properties and the resistance to delayed fracture after quenching and tempering, and a bolt using the same. Disclosed is a wire rod for bolts that has excellent acid pickling properties and resistance to delayed fracture, including, in percent by mass: C: 0.3 to 0.6%; Si: 1.0 to 3.0%; Mn: 0.1 to 1.5%; P: more than 0% and 0.020% or less; S: more than 0% and 0.020% or less; Cr: 0.3 to 1.5%; Al: 0.02 to 0.10%; and N: 0.001 to 0.020%, with the balance being iron and inevitable impurities, wherein in a d 1/4 position of the wire rod, where d is a diameter of the wire rod, a ferrite area ratio is in a range of 10 to 40%, with the remaining microstructure being bainite, pearlite and an inevitably formed microstructure, and a C content in a position at a depth of 0.1 mm from a surface layer of the wire rod is in a range of 50 to 100% of a C content in a base material.

A method of machining a screw is provided that is capable of preventing formation of a protruding section at a thread tip section. A thread is formed by cutting on a cylindrical body, and a surface of the thread is plastically deformed by rolling. Because of the cutting, a width between-side surfaces of a thread tip section is in a narrowed state as compared to a normal width. This width is narrowed toward a tip of the thread while a thread body section has a width expanded as compared to a normal width. Consequently, the side surfaces are formed to bulge by an excess thickness portion as compared to normal side surfaces. The rolling plastically deforms both side surfaces to cause the excess thickness portion to plastically flow toward the side surfaces.

There are provided a steel wire rod for ultra-high-strength parts such as automobile engine bolts or structural mechanical parts, and a method for producing the steel wire rod. The steel wire rod having high strength and ductility includes, by wt %, carbon (C): 0.7% to 0.9%, manganese (Mn): 13% to 17%, copper (Cu): 1% to 3%, and the balance of iron (Fe) and inevitable impurities.