Stretch rolling method and stretch rolling unit

A stretch rolling unit (10) comprising two stretching rolls (20) that can be driven in opposite directions, having at least two passes (21, 22, 23, 24) and at least one gripping device (30), which can grip a workpiece (50) at a gripping end (52) and can be brought into at least a first loading position (61) and a first unloading position (62) for the first pass (21, 22, 23) and into a second loading position (61) for the second pass (22, 23, 24),

• wherein the gripping device (30) can be brought into a start-of-rotation position (63) and into an end-of-rotation position (64),
• wherein the stretch rolling unit (10) comprises a rotation device (40) that can bring the workpiece (50) from the start-of-rotation position (63) into the end-of-rotation position (64), by rotating it by 180° about an axis of rotation (42) that lies perpendicular to a main expanse direction (54) of the workpiece (50),
• wherein the gripping device (30) can be moved horizontally toward the stretching roll (20) as well as vertically to a level of the second pass (22, 23, 24) for the second pass (22, 23, 24), and
• (i) wherein a first gripper of the gripping device (30) is configured to bring the workpiece (50) into the start-of-rotation position (63), and a second gripper of the gripping device (30) is configured to hold the workpiece (50) in the end-of-rotation position (64), wherein the start-of-rotation position (63) is different from the end-of-rotation position (64), and wherein the second gripper of the gripping device (30) can take over the rotating workpiece from the end-of-rotation position, without having to newly position itself, and
• (ii) wherein stretch rolling free of gripping ends occurs without a reversal of direction of the stretching rolls between two passes.

A stretch rolling method for the production of railroad axles in which a workpiece (50) is successively passed by a gripping device to at least two passes (21, 22, 23, 24) of a stretch rolling unit (10),

• wherein the workpiece (50) is rotated by 180°, about an axis of rotation (42) that lies perpendicular to a main expanse direction (54) of the workpiece (50), between the first pass (21, 22, 23) of the two passes (21, 22, 23, 24) and the second pass (22, 23, 24) of the two passes (21, 22, 23, 24), and
• wherein the gripping device (30) is displaced horizontally toward the stretching roll (20) as well as vertically to a height of the second pass (22, 23, 23) before the second pass (22, 23, 24), and
• wherein before rotation, a non-rolled gripping end (52) of the workpiece (50) is grasped by the gripping device (30), and after rotation, a rolled end (52) is grasped, and wherein one and the same gripper of the gripping device grips the workpiece, not only at the non-rolled gripping end before rotation but also at the rolled gripping end after rotation, and
• wherein stretch rolling free of gripping ends occurs without a reversal of direction of the stretching rolls between two passes.

A stretch rolling unit (10) for the production of railroad axles comprising two stretching rolls (20) that can be driven in opposite directions, having at least two passes (21, 22, 23, 24) and at least one gripping device (30), which can grip a workpiece (50) at a gripping end (52) and can be brought into at least a first loading position (61) and a first unloading position (62) for the first pass (21, 22, 23) and into a second loading position (61) for the second pass (22, 23, 24),

• wherein the gripping device (30) can be brought into a start-of-rotation position (63) and into an end-of-rotation position (64),
• wherein the stretch rolling unit (10) comprises a rotation device (40) that can bring the workpiece (50) from the start-of-rotation position (63) into the end-of-rotation position (64), by rotating it by 180° about an axis of rotation (42) that lies perpendicular to a main expanse direction (54) of the workpiece (50), and
• wherein the gripping device (30) can be moved horizontally toward the stretching roll (20) as well as vertically to a level of the second pass (22, 23, 24) for the second pass (22, 23, 24), and
• wherein the gripping device (30) has a gripper (32) having a gripping diameter that comprises both rolled and non-rolled diameters of a gripping end (52) to be gripped, and
• wherein stretch rolling free of gripping ends occurs without a reversal of direction of the stretching rolls between two passes.