A coil spring for a vehicle suspension according to one embodiment includes a lower end turn portion, an upper end turn portion, and a cylindrical effective portion between the lower end turn portion and the upper end turn portion. In at least one of the upper end turn portion and the lower end turn portion, a taper portion having a taper length and a taper thickness for controlling a force line of the coil spring is formed. The taper portion is formed such that the thickness is reduced in a tapered way from a thickness varying portion provided in the middle of the end turn portion toward a distal end of the wire along its length. The thickness varying portion is arranged at a position close to the force line.

A tubular spring, such as a coil spring, a torsion-rod spring, and/or a stabilizer for a motor vehicle, may include at least one metal tube element having a tube internal cross section, a tube internal diameter, a tube external diameter, a tube internal wall, and a tube wall thickness. At least one metal foam may be disposed in the tube internal cross section of the at least one metal tube element of the tubular spring in at least one part-region. In particular, the metal foam may be connected in an at least partially materially integral manner to the tube internal wall of the metal tube element. The at least one metal tube element may have an at least partially martensitic structure.

A coil spring for use in a link-motion-type suspension includes a lower end turn portion, an upper end turn portion, and an effective portion of a cylindrical shape between the lower end turn portion and the upper end turn portion. Further, the coil spring includes a bowing control portion including a taper portion formed in at least one end turn portion of the lower end turn portion and the upper end turn portion. The taper portion has a shape whose thickness is reduced from the middle of the end turn portion toward a distal end of a wire along its length, and bowing of the effective portion is suppressed by absorbing a change in the inclination of a spring seat by the taper portion.

A coil spring according to one embodiment includes a lower end turn portion which is in contact with a lower spring seat, an upper end turn portion which is in contact with an upper spring seat, and an effective portion between the lower end turn portion and the upper end turn portion. The coil spring is cylindrical about an axis of the effective portion in its free shape which is not compressed. Further, with respect to a coordinate system in which a force line is assumed as a Z-axis, the coil spring is cylindrical with a constant pitch in a direction along the Z-axis in its compressed shape which is compressed to a specified height.

A coil spring for a vehicle suspension according to one embodiment includes a lower end turn portion, an upper end turn. portion, and a cylindrical effective portion between the lower end turn portion and the upper end turn portion. In at least one of the upper end turn portion and the lower end turn portion, a taper portion having a taper length and a taper thickness for controlling a force line of the coil spring is formed. The taper portion is formed such that the thickness is reduced in a tapered way from a thickness varying portion provided in the middle of the end turn portion toward a distal end of the wire along its length. The thickness varying portion is arranged at a position close to the force line.

A press-formed product includes a main body part having a first end part and a second end part respectively on both ends, and a protruded part that protrudes outward of bending from a bent part of the main body part. On a surface of the top plate part of the main body part, a groove part is provided in a domain on the first end part side from a root of the protruded part. A first vertical wall part extending from the first end part of the main body part to the protruded part has a corner part connecting the main body part and the protruded part. An angle that is formed by a part which is on the main body part side from the corner part and a part which is on the protruded part side from the corner part is an acute angle.

A press-formed product includes a main body part having a first end part and a second end part respectively on both ends, and a protruded part that protrudes outward of bending from a bent part of the main body part. On a surface of the top plate part of the main body part, a groove part is provided in a domain on the first end part side from a root of the protruded part. A first vertical wall part extending from the first end part of the main body part to the protruded part has a corner part connecting the main body part and the protruded part. An angle that is formed by a part which is on the main body part side from the corner part and a part which is on the protruded part side from the corner part is an acute angle.

A stabilizer bar for a chassis of a motor vehicle comprises a torsion spring portion and two arms bent away from the torsion spring portion; wherein the arms each comprise a formed end portion with a through-opening and a tubular portion, wherein the torsion spring portion comprises a hardened structure with a strength of at least 1000 MPa; and wherein the formed end portions comprise a hardened structure with a strength of at least 800 MPa. A process of producing a corresponding stabilizer is further disclosed.

A steel, having a high corrosion resistance and low-temperature toughness, for a vehicle suspension spring part, the steel includes 0.21 to 0.35% by mass of C, more than 0.6% by mass but 1.5% by mass or less of Si, 1 to 3% by mass of Mn, 0.3 to 0.8% by mass of Cr, 0.005 to 0.080% by mass of sol. Al, 0.005 to 0.060% by mass of Ti, 0.005 to 0.060% by mass of Nb, not more than 150 ppm of N, not more than 0.035% by mass of P, not more than 0.035% by mass of S, 0.01 to 1.00% by mass of Cu, and 0.01 to 1.00% by mass of Ni, the balance being Fe and unavoidable impurities, with Ti+Nb0.07% by mass, wherein crystal grains of the steel after hardening have a prior austenite grain size number of 7.5 to 10.5, and the steel having a tensile strength of not less than 1,300 MPa.