A hollow stabilizer production method of a hollow stabilizer used for a vehicle includes attaching a first mounting member and a second mounting member respectively to one end and another end of a formed steel tube and heating the steel tube. The method includes feeding a carburizing gas into the interior space of the heated steel tube through the first mounting member, and collecting the air and/or the surplus carburizing gas from the interior space through the second mounting member to thereby carburize the steel tube inner surface. The method includes rapidly cooling the heated steel tube to thereby quench the steel tube continuously from the carburization.

A method of manufacturing a suspension coil spring includes forming first shot peening indentations on a surface of a wire by projecting first shots toward the wire and forming a compressive residual stress portion to which a compressive residual stress is imparted from the surface of the wire to a first depth, and projecting ball shots as second shots toward a lower end turn portion by an ultrasonic apparatus. A size of each ball shot is larger than a size of each first shot. The method includes forming second shot peening indentations on a surface of the lower end turn portion, and a deep residual stress portion in the lower end turn portion, a compressive residual stress of the deep residual stress portion imparted from the surface of the wire to a second depth that is deeper than the first depth.

A hollow stabilizer has a tubular shape and is provided with a torsion section that is provided to a vehicle and that extends in the vehicle width direction; an arm section that extends in the front-back direction of the vehicle; and bent sections that connect the torsion section and the arm section. The hardness of the outer surface of the bent inner sides of the bent sections of the hollow stabilizer is 70% or more with respect to the hardness of the outer surface of the arm section.

A method of manufacturing a hollow stabilizer includes a forming step of subjecting an element pipe to a bending process, to form a product shape including bent portions, and a quenching step of quenching the element pipe subjected to the bending process. In the quenching step, a cooling process is performed by immersing the element pipe made of steel in coolant and by spraying the coolant to an outer surface of the bent portion.

A method of manufacturing a suspension coil spring includes forming first shot peening indentations on a surface of a wire by projecting first shots toward the wire and forming a compressive residual stress portion to which a compressive residual stress is imparted from the surface of the wire to a first depth, and projecting ball shots as second shots toward a lower end turn portion by an ultrasonic apparatus. A size of each ball shot is larger than a size of each first shot. The method includes forming second shot peening indentations on a surface of the lower end turn portion, and a deep residual stress portion in the lower end turn portion, a compressive residual stress of the deep residual stress portion imparted from the surface of the wire to a second depth that is deeper than the first depth.

The invention relates to a process for producing a heat-treated hub carrier provided with a wheel bearing, the process comprising the successive steps: a) provision of a hub-carrier blank which is preferably cast, b) solution annealing of the hub carrier, c) quenching of the hub carrier, preferably in water and/or air, d) at least partial machining of the hub carrier, e) insertion of the wheel bearing into a recess of the hub carrier, f) re-annealing or hot ageing of the hub carrier.

The present invention provides a method for manufacturing a torsion beam, the method comprising: a planarization step, in which a protruding portion of an upper mold presses the opposite end portions in the width direction of the blank to be plastically deformed to be flat while the opposite end portions in the width direction of the blank are supported by a side cam to face each other; a welding and bonding step for bonding the planarized opposite end portions in the width direction of the blank via welding; and a quenching step for heating the welded and bonded blank within a range of 900 to 970? C. for a retaining time within a range of 1 to 20 minutes and for cooling down the blank in a treatment liquid including at least one of water and oil in a range of 20 to 90? C.

A hollow stabilizer production method of a hollow stabilizer used for a vehicle includes attaching a first mounting member and a second mounting member respectively to one end and another end of a formed steel tube and heating the steel tube. The method includes feeding a carburizing gas into the interior space of the heated steel tube through the first mounting member, and collecting the air and/or the surplus carburizing gas from the interior space through the second mounting member to thereby carburize the steel tube inner surface. The method includes rapidly cooling the heated steel tube to thereby quench the steel tube continuously from the carburization.

A hollow spring member and hollow spring member production method can be provided, which can save the time and energy necessary for carburization, thus requiring no dedicated carburizing furnace or the like for carburization, and further can make the interior space of a steel tube a rust-prevention atmosphere. A hollow stabilizer for a vehicle includes a steel tube sealed at one end and another end thereof and a carburizing gas sealed in the interior space of the steel tube.

The present invention relates to a tubular anti-roll bar for a vehicle chassis, produced from a metal tubular body, comprising a torsion spring portion, two limbs bent off from the torsion spring portion and a bending portion, arranged between the torsion spring portion and the respective bent limb and having an inside bending radius (IB) and an outside bending radius (OB), wherein the tubular anti-roll bar has a structure with grains with a grain size distribution and an average grain size, wherein the structure has a ratio between the average grain size in the bending portion of the inside bending radius (IB) in relation to the average grain size in the torsion spring portion in the range of 73% to 77%.