A stabilizer is a stabilizer including: a main body cylinder portion which is elastically deformable and a pair of connection plate portions respectively connected to a pair of left and right suspension devices, wherein the connection plate portion includes a pair of base material portions located on both sides in the connection plate portion in a plate thickness direction T and an alloy oxide region which is disposed between the pair of base material portions and in which alloy oxides are scattered, and wherein crystal grains constituting the pair of base material portions straddle the alloy oxide region in the plate thickness direction and the pair of base material portions are joined.

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.

This spring used for a suspension device for a vehicle is provided with: a metal wire material which constitutes a spring section and which has a cover layer provided on the surface thereof; and a seat section which is subjected to a load acting on the spring section, is formed from an elastically deformable material, and is bonded to the cover layer by an adhesive. The difference between the hardness of the seat section and the hardness of the adhesive is greater than the difference between the hardness of the adhesive and the hardness of the cover layer.

A hollow stabilizer (1) according to the invention is formed in a hollow shape and includes a bent portion (1c1, 1c2, m1-m5). With a thickness of an inner side of the bent portion (1c1, 1c2, m1-m5) being larger than a thickness of an outer side of the bent portion (1c1, 1c2, m1-m5), a hardness of the outer side of the bent portion (1c1, 1c2, m1-m5) is higher than a hardness of the inner side of the bent portion (1c1, 1c2, m1-m5) through quenching by cooling down after heating by electrical heating.

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.