In one embodiment, a method for manufacturing a pipe bend is disclosed, comprising: heating, with an induction coil, a first annular band of a wall of a first end portion of a moving pipe; directing quenching fluid toward an outer and inner surface of the first annular band; heating a second annular band of a wall of a bend portion of the moving pipe; directing the quenching fluid toward an outer and inner surface of the second annular band; decreasing a speed of the pipe while moving the induction coil from stationary and maintaining a relative speed between the pipe and the induction coil substantially constant; heating a third annular band of a wall of a second end portion of the pipe while moving the induction coil; and directing the quenching fluid toward an outer surface and an inner surface of the third annular band while moving the induction coil.

In one embodiment, a method for manufacturing a pipe bend is disclosed, comprising: heating, with an induction coil, a first annular band of a wall of a first end portion of a moving pipe; directing quenching fluid toward an outer and inner surface of the first annular band; heating a second annular band of a wall of a bend portion of the moving pipe; directing the quenching fluid toward an outer and inner surface of the second annular band; decreasing a speed of the pipe while moving the induction coil from stationary and maintaining a relative speed between the pipe and the induction coil substantially constant; heating a third annular band of a wall of a second end portion of the pipe while moving the induction coil; and directing the quenching fluid toward an outer surface and an inner surface of the third annular band while moving the induction coil.

A mandrel 10 for producing a thin-walled bent tube having a bending portion with high strength and a small radius of curvature by rotary draw bending without either cracks in an outside of bend or winkles and buckling in an inside of bend occurring includes a shank 14, a connection mechanism 15 and a mandrel ball 16. In a cross-section orthogonal to an axial direction of the mandrel ball 16 at a central position in the axial direction of the mandrel ball 16, the mandrel ball 16 has a first position 19 and a second position 20 at which a first straight line m that passes through a mandrel ball center 17 meets an outer periphery 21 of the mandrel ball. Further, a ratio (L.sub.1/L.sub.2) between a dimension L.sub.1 from the mandrel ball center 17 to the first position 19 and a dimension L.sub.2 from the mandrel ball center 17 to the second position 20 is in a range of 0.915 to 0.976.

A bender configured to bend a workpiece in a bending operation and its method of use are provided. The bender includes a frame, a bending shoe assembly rotatably mounted on the frame, a control system and a driver in communication therewith, and a springback assembly in communication with the control system and configured to provide information to the control system regarding information on a bend affected to the workpiece. The bending shoe assembly includes a bending shoe into which the workpiece can be seated, and a gripping member mounted on the bending shoe and configured to grip the workpiece during the bending operation. The driver provides rotational force to the bending shoe assembly to rotate the bending shoe assembly relative to the frame.

A bender configured to bend a workpiece in a bending operation and its method of use are provided. The bender includes a frame, a bending shoe assembly rotatably mounted on the frame, a control system and a driver in communication therewith, and a springback assembly in communication with the control system and configured to provide information to the control system regarding information on a bend affected to the workpiece. The bending shoe assembly includes a bending shoe into which the workpiece can be seated, and a gripping member mounted on the bending shoe and configured to grip the workpiece during the bending operation. The driver provides rotational force to the bending shoe assembly to rotate the bending shoe assembly relative to the frame.

An electric resistance welded steel pipe for manufacturing a hollow stabilizer has a Rankford value in a pipe longitudinal direction of from 0.7 to less than 1.0. The electric resistance welded steel pipe is subjected to cold bending and then to a heat treatment including quenching and tempering to manufacture a stabilizer. The cold bending is cold rotary draw bending. When bent with a bend radius of from 1.0 times to 3.0 times an outer diameter of the pipe before cold bending, a flattening ratio is from 0% to 10%, a thickness reduction rate on a bending outside and a thickness increase rate on a bending inside are from 0% to 10%, and additionally, a circumferential length change of a bending center portion is from 0% to 10%. A Vickers hardness of the stabilizer after the heat treatment is adjusted to from 400 HV to less than 580 HV.

An electric resistance welded steel pipe for manufacturing a hollow stabilizer has a Rankford value in a pipe longitudinal direction of from 0.7 to less than 1.0. The electric resistance welded steel pipe is subjected to cold bending and then to a heat treatment including quenching and tempering to manufacture a stabilizer. The cold bending is cold rotary draw bending. When bent with a bend radius of from 1.0 times to 3.0 times an outer diameter of the pipe before cold bending, a flattening ratio is from 0% to 10%, a thickness reduction rate on a bending outside and a thickness increase rate on a bending inside are from 0% to 10%, and additionally, a circumferential length change of a bending center portion is from 0% to 10%. A Vickers hardness of the stabilizer after the heat treatment is adjusted to from 400 HV to less than 580 HV.

A bender configured to bend a workpiece in a bending operation and its method of use are provided. The bender includes a frame, a bending shoe assembly rotatably mounted on the frame, a control system and a driver in communication therewith, and a springback assembly in communication with the control system and configured to provide information to the control system regarding information on a bend affected to the workpiece. The bending shoe assembly includes a bending shoe into which the workpiece can be seated, and a gripping member mounted on the bending shoe and configured to grip the workpiece during the bending operation. The driver provides rotational force to the bending shoe assembly to rotate the bending shoe assembly relative to the frame.

A bender configured to bend a workpiece in a bending operation and its method of use are provided. The bender includes a frame, a bending shoe assembly rotatably mounted on the frame, a control system and a driver in communication therewith, and a springback assembly in communication with the control system and configured to provide information to the control system regarding information on a bend affected to the workpiece. The bending shoe assembly includes a bending shoe into which the workpiece can be seated, and a gripping member mounted on the bending shoe and configured to grip the workpiece during the bending operation. The driver provides rotational force to the bending shoe assembly to rotate the bending shoe assembly relative to the frame.

A metal pipe including a curved portion produced by bending in which a plurality of non-bending surfaces and a plurality of bent portions at which the non-bending surfaces are connected in a bending manner are provided on a circumferential surface on an inside of a center of a curvature side of the curved portion is provided.