Rolling mechanism, skew rolling mill and method for rolling ultrafine-grained M50NiL rod

A rolling mechanism for grain refinement of a metal rod, comprising two main rolls and two auxiliary rolls;

• wherein:
• the two main rolls are opposite to each other and the two auxiliary rolls are opposite to each other, and the two main rolls and the two auxiliary rolls are disposed around a rolling line to form a nip zone where a billet is rolled into the metal rod;
• in any cross section of the nip zone with the rolling line as a normal line, a first line connecting central axes of the two main rolls is perpendicular to a second line connecting central axes of the two auxiliary rolls;
• each main roll comprises a first protrusion portion, a first end portion and a second end portion;
• the first end portion and the second end portion are disposed opposite each other along a corresponding roll axis;
• the first end portion has a smaller diameter than the second end portion;
• the first protrusion portion is disposed between the first end portion and the second end portion;
• each auxiliary roll comprises a second protrusion portion, a third end portion and a fourth end portion;
• the third end portion and the fourth end portion are disposed opposite each other along a corresponding roll axis;
• the third end portion has a smaller diameter than the fourth end portion;
• the second protrusion portion is disposed between the third end portion and the fourth end portion;
• and
• the first protrusion portion has a greater diameter than the second protrusion portion;
• a narrow space of the nip zone is surrounded by the two first protrusion portions of the two main rolls and the two second protrusion portions of the two auxiliary rolls;
• the first end portion is disposed adjacent to the fourth end portion;
• and the second end portion is disposed adjacent to the third end portion.