A stabilizer comprises a main bar that is elastically deformable, a pair of connecting plates respectively configured to be connected to a pair of left and right suspension apparatuses, and transition sections connecting both end portions of the main bar and the pair of connecting plates, a size of one transition section of the transition sections in a plate thickness direction of one connecting plate of the connecting plates gradually decreasing from the main bar toward the connecting plate, wherein the minimum value of the Vickers hardness of the transition section is 200 HV or more.

In a pressing step, a first forged product is pressed by a first die, and thereby, a second forged product including a rough flange having a thickness-changing portion is produced. The thickness-changing portion includes a front part protruding frontward from a side of a rough web part and a rear part protruding rearward from the side of the rough web part. Each of the front part and the rear part includes a first part, and a second part that is thicker than the first part and is located farther from the rough web part than the first part. In the pressing step, at least a part of the rough flange that is above or below the web part (thick part) is pressed by the first die, whereby the material of the first forged product in the part is caused to flow frontward and rearward, and the thickness-changing portion is formed.

The production method disclosed is a method for producing a front axle beam. The production method includes a die forging step and a bending step. The die forging step is a step of forging a steel material with dies to produce a forged product including a rough web part, which is to be formed into a web part, and four plate-shaped rough flange parts protruding frontward and rearward from an upper side and a lower side of the rough web part, respectively. The bending step is a step of pressing at least one specified rough flange part, which is at least one of the four rough flange parts, with a first die to form a bent portion in the specified rough flange part such that the bent portion is bent inward in an up-down direction of the forged product.

A front lower arm is tiltably supported, in a cantilever manner, by an outer surface of each of side-rails provided in right and left vehicle regions and extending in a vehicle front-rear direction. The front lower arm includes: a lower arm body; an inner pivot provided at an inner end of the lower arm body in a vehicle right-left direction and supported by the side-rail; and an attachment portion to which a lower end of a shock absorber is attached, and which is joined to an intermediate section of a front upper corner portion of the lower arm body. The intermediate section is an intermediate section of the front upper corner portion in the vehicle right-left direction. A ball joint to which a knuckle is connected is attached to an outer end of the front lower arm in the vehicle right-left direction.

Provided is a vehicle suspension member securing a strength against external force in a vehicle longitudinal direction. A lower arm includes an arm body, a front bush support part, a rear bush support part, a ball joint support part, a first rib, a second rib, and a third rib. The third rib is disposed in a lateral part connecting the ball joint support part to the rear bush support part. An S-shaped rib center curve of the third rib intersects with a straight line at an intersection. |(1−S2/S1)|≤0.2 is satisfied, where S1 is area of a first region defined by the rib center curve and the first straight line, and S2 is area of a second region.

Provided is a production method of an aluminum alloy forging for an automobile suspension having a disturbance affectable surface with not excessively notch-sensitive. The production method includes, as heat treatment processes, a solution heat treatment process, a quenching process, and an artificial age hardening process. The quenching process is performed by bringing a lower surface of the aluminum forging to be disposed on a ground side when assembled to the automobile into contact with water before an upper surface of the aluminum forging opposite to the lower surface is brought into contact with the water.

A stabilizer comprises a main bar that is elastically deformable, a pair of connecting plates respectively configured to be connected to a pair of left and right suspension apparatuses, and transition sections connecting both end portions of the main bar and the pair of connecting plates, a size of one transition section of the transition sections in a plate thickness direction of one connecting plate of the connecting plates gradually decreasing from the main bar toward the connecting plate, wherein the minimum value of the Vickers hardness of the transition section is 200 HV or more.

This torsion beam manufacturing method is a method for manufacturing a torsion beam which is provided with a uniformly shaped closed cross-sectional portion in which a cross section orthogonal to a longitudinal direction is a closed cross section having a substantial V-shape or a substantial U-shape with a pair of ear portions, and a shape changing portion which leads to the uniformly shaped closed cross-sectional portion and in which a shape of the closed cross section changes progressively away from the uniformly shaped closed cross-sectional portion, the torsion beam manufacturing method comprising: thickening to form a pair of thickened portions in at least the shape changing portion by pressurizing each of the pair of ear portions from outside against swelling of the pair of ear portions in a slate where both outer surfaces of each of the pair of ear portions are supported.

Both weight reduction and inhibition of torsional rigidity deterioration in a structural member requiring a torsional rigidity against a torsional moment are attained.

A structural member has a first end including a first attaching part, a second end including a second attaching part, and an arm extending from the first end to the second end. The arm has a first outside surface, a second outside surface, and an arm surface. The arm has a first rib and a second rib protruding from the arm surface in a thickness direction. The first rib extends in an inclination direction that is a direction directed from the first outside surface toward the second outside surface and is a direction having a component of an arm direction. The second rib is formed so as to intersect with the first rib.

An annular reference surface is formed around a through-hole of an eye portion. A distal-end-side curved portion is formed at a first corner portion, on an outer side of the annular reference surface. The thickness of the distal-end-side curved portion is reduced in a range of a length from the first flat surface toward the distal end surface. A hole-side curved portion whose thickness is reduced toward an inner surface of the through-hole is formed at a second corner portion, on an inner side of the annular reference surface. The length of the hole-side curved portion is less than the length of the distal-end-side curved portion. The hole-side curved portion is curved with a greater curvature than that of the distal-end-side curved portion.