A rolling stand 100 in accordance with the invention is a rolling stand provided with three grooved rolls for rolling a tubular or bar shaped material to be rolled, in which three grooved rolls R 21 to R 23 are arranged in such a manner that an angle formed by pressing directions of any two adjacent grooved rolls of the three grooved rolls R 21 to R 23 comes to 120 degrees. With regard to a cross sectional shape of each of the grooved rolls R 21 to R 23 formed by cutting each of the grooved rolls in a plane which includes a center line of a rotating axis of each of the grooved rolls R 21 to R 23 and is orthogonal to a pass line of a material to be rolled, any one grooved roll R 21 is provided with a first straight portion L 1 extending vertically to the pressing direction in both side flange portions, and the other two grooved rolls R 22 and R 23 are provided with a second straight portion L 2 opposing to the first straight portion L 1 and extending in parallel to the first straight portion L 1 in the flange portions.
1. A rolling stand comprising three grooved rolls, wherein the three grooved rolls are arranged around a pass line center of a material to be rolled, each of the grooved rolls movable in a direction towards and away from the pass line center,
wherein with regard to a cross sectional shape of each of the grooved rolls, the cross sectional shape of any one grooved roll is provided with a first straight portion extending vertically to the pressing direction in both side flange portions of the any one grooved roll, and wherein the cross sectional shape of the other two grooved rolls is provided with a second straight portion opposing to the first straight portion and extending in parallel to the first straight portion in flange portions of the other two grooved rolls.
2. The rolling stand as claimed in claim 1 , wherein the cross sectional shape of the any one grooved roll provided with the first straight portion is further provided with a third straight portion extending in parallel to the movable direction in at least one side flange portion of the any one grooved roll, and
wherein the cross sectional shape of at least one grooved roll in the other two grooved rolls provided with the second straight portions is further provided with a fourth straight portion opposing to the third straight portion and extending in parallel to the third straight portion in a flange portion of the at least one grooved roll.
3. A rolling stand comprising four grooved rolls, wherein the four grooved rolls are arranged around a pass line center of a material to be rolled, each of the grooved rolls movable in a direction towards and away from the pass line center,
wherein with regard to a cross sectional shape of each of the grooved rolls, the cross sectional shape of at least one grooved roll in any one set of opposing grooved rolls is provided with a first straight portion extending vertically to the movable direction in both side flange portions of the at least one grooved roll, and is provided with a third straight portion extending in parallel to the movable direction in the both side flange portions of the at least one grooved roll, and wherein the cross sectional shape of each of the grooved rolls in the other set of grooved rolls is provided with a second straight portion opposing to the first straight portion and extending in parallel to the first straight portion in a flange portion of each of the grooved rolls in the other set of grooved rolls, and is provided with a fourth straight portion opposing to the third straight portion and extending in parallel to the third straight portion in the flange portion of each of the grooved rolls in the other set of grooved rolls.