Strip rolling method and strip rolling mill

A strip rolling method applied to a multi-roll strip rolling mill of not less than four rolls including at least a top and a bottom backup roll and a top and a bottom work roll, comprising the steps of:

• measuring thrust counterforces in the axial direction of the rolls acting on all the rolls except for the backup rolls in one of the top and the bottom roll assembly or preferably in both the top and the bottom roll assembly;
• measuring roll forces of the backup roll acting in the vertival direction on the backup roll chocks of the backup roll in the top and the bottom backup roll on the side of measuring the thrust counterforces;
• calculating a target increments of roll positioning devices of the strip rolling mill according to the measured values of the thrust counterforces and the roll forces of the backup roll;
• and
• controlling a roll forces according to the target increments of roll positioning devices of the strip rolling mill.

A strip rolling method applied to a multi-roll strip rolling mill of not less than four rolls including at least a top and a bottom backup roll and a top and a bottom work roll, comprising the steps of:

• measuring thrust counterforces in the axial direction of the rolls acting on all the rolls except for the backup rolls in one of the top and the bottom roll assembly or preferably in both the top and the bottom roll assembly;
• measuring roll forces of the backup roll acting in the vertival direction on the backup roll chocks of the backup roll in the top and the bottom backup roll on the side of measuring the thrust counterforces;
• calculating asymmetry of the distribution of a load, which acts between a workpiece to be rolled and the work roll, in the axial direction of the roll with respect to the rolling mill center while consideration is given to a at least thrust force acting between the backup roll and a roll in contact with the backup roll;
• calculating a target increments of roll positioning devices of the strip rolling mill according to the result of the calculation;
• and
• controlling reduction according to the target increments of roll positioning devices.

A multi-roll strip rolling mill composed of not less than four rolls having a top and a bottom work roll and also having a top and a bottom backup roll, the strip rolling mill comprising:

• a measurement device for measuring thrust counterforces in the axial direction of the roll acting all the rolls except for the backup rolls;
• a measurement device for measuring roll forces of the backup rolls acting in the vertival direction on the backup roll chocks of the top and the bottom backup roll;
• and
• a calculating device connected to the measurement devices for measuring the thrust counterforces and also connected to the measurement devices for either measuring the roll forces, calculating asymmetry of distribution of a load, which acts between a workpiece to be rolled and the work roll, in the axial direction of the roll with respect to the rolling mill center while consideration is given to at least thrust forces acting between the backup rolls and the rolls in contact with them, or calculating asymmetry of the distribution of a load acting between the top and the bottom work roll in the axial direction of the roll with respect to the rolling mill center.

A strip rolling method applied to a multi-roll strip rolling mill of not less than four rolls including at least a top and a bottom backup roll and a top and a bottom work roll, comprising the steps of:

• prior to rolling operation tightening the top and the bottom backup roll and the top and the bottom work roll by roll positioning devices under the condition that the backup rolls and the work rolls come into contact with each other;
• measuring thrust counterforces in the axial direction of the roll which acts on all the rolls except for the backup rolls;
• measuring roll forces acting in the vertical direction of on all of the backup roll chock of the top and the bottom backup rolls;
• setting an absolute value of the force of roll balance devices or roll bending devices, which give forces to the chocks for which thrust counterforces are to be measured, at a value not more than ½ of the force of the roll balanced condition, preferably at zero;
• finding one of or both of the zero point of the roll positioning devices and the deformation characteristic of the strip rolling mill according to the measured values of the thrust counterforces and the roll forces of the backup rolls;
• and
• conducting roll forces setting and/or roll forces control according to the thus found values when rolling is actually carried out.

A strip rolling method applied to a multi-roll strip rolling mill composed of not less than four rolls including at least a top and a bottom backup roll and a top and a bottom work roll, comprising the steps of:

• measuring thrust counterforces in the axial direction of the rolls acting on all the rolls except for the backup rolls in one of the top and the bottom roll assembly or preferably in both the top and the bottom roll assembly;
• measuring roll forces acting in the vertical direction on the backup roll choce of the top and the bottom backup roll;
• calculating a target increments of roll positioning devices of the strip rolling mill according to the measured values of the thrust counterforces and the roll forces of the backup rolls;
• setting an absolute value of the force of roll balance devices or roll bending devices, which give forces to roll chocks, for which counterforce are to be measured, at a value not more than ½ of the force of the roll balanced condition, preferably at zero;
• and
• controlling roll-gap on the work side and that on the drive side target increments of roll positioning devices of the strip rolling mill.

A strip rolling method applied to a multi-roll strip rolling mill of not less than four rolls including at least a top and a bottom backup roll and a top and a bottom work roll, comprising the steps of:

• measuring thrust counterforces in the axial direction of the rolls acting on all the rolls except for the backup rolls in one of the top and the bottom roll assembly or preferably in both the top and the bottom roll assembly;
• measuring roll forces acting in the vertival direction of the backup roll on the backup roll chocks of the top and the bottom backup roll;
• setting an absolute value of the force of roll balance devices or roll bending devices, which gives forces to the roll chock, for which the thrust counterforces are to be measured, at a value not more than ½ of the force of the roll balance condition, preferably at zero, at least at the time of measuring the thrust counterforces in the process of rolling;
• calculating asymmetry of distribution of a load in the axial direction of the roll acting at least between a workpiece to be rolled and the work roll with respect to the rolling mill center;
• calculating target value of increments of positions devices strip rolling mill according to the result of calculation;
• and
• conducting control of roll gap on the workside and that on the drive side according to the increments of the roll positioning devices.

A strip rolling method applied to a multi-roll strip rolling mill composed of not less than four rolls including at least a top and a bottom backup roll and a top and a bottom work roll also including a strip crown and flatness control means in addition to roll bending device, comprising the steps of:

• measuring thrust counterforces in the axial direction of the rolls acting on all the rolls except for the backup rolls in one of the top and the bottom roll assembly or preferably in both the top and the bottom roll assembly;
• measuring roll forces of the backup roll acting in the vertival direction on the backup roll chocks of the top and the bottom backup roll:
• calculating a strip rolling mill setting condition so that an absolute value of the roll bending force can be made to be a value not more than ½ of a value of the roll balance condition, preferably an absolute value of the roll bending force can be made to be zero by the strip crown and flatness control means other than the roll bending device in the process of setting calculation for obtaining a predetermined strip crown and flatness;
• and
• carrying out rolling by changing the roll bending force from the value of the roll balance condition to the setting calculation value immediately after the start of rolling according to the result of calculation.

A method of calibration of a strip rolling mill for finding a deformation characteristic of the strip rolling mill with respect to a thrust force acting between the rolls of the multi-roll strip rolling mill composed of not less than four rolls including at least a top and a bottom backup roll and a top and a bottom work roll, comprising the steps of:

• giving a load in the vertical direction corresponding to a rolling load to a housing of the strip rolling mill;
• measuring at least one of the loads in the vertical direction given to an upper and a lower portion of the strip mill housing via load cells for measuring a rolling load;
• giving a load, which is asymmetrical with respect to the upper and lower sides, to the housing of the strip rolling mill by giving an external force in the vertical direction from the outside of the strip rolling mill under the condition that the load in the vertical direction is being given;
• and
• measuring the load cell load.

A method of calibration of a strip rolling mill for finding a deformation characteristic of the strip rolling mill with respect to a thrust force acting between the rolls of the multi-roll strip rolling mill of not less than four rolls including at least a top and a bottom backup roll and a top and a bottom work roll, comprising the steps of:

• giving a load in the vertical direction corresponding to a rolling load to a barrel portion of the backup roll under the condition that at least the top and the bottom backup roll are incorporated into the strip rolling mill;
• measuring at least one of the loads in the vertical direction given to an upper and a lower portion of the strip mill housing via load cells for measuring a rolling load;
• giving a load, which is asymmetrical with respect to the upper and lower sides, to the housing of the strip rolling mill via the roll chocks of the top and the bottom backup roll by giving an external force in the vertical direction from the outside of the strip rolling mill under the condition that the load in the vertical direction is being given;
• and
• measuring the load cell load.

A method of calibration of a strip rolling mill for finding a deformation characteristic of the strip rolling mill with respect to a thrust force acting between the rolls of the multi-roll strip rolling mill of not less than four rolls including at least a top and a bottom backup roll and a top and a bottom work roll, comprising the steps of:

• removing out at least one of the rolls other than the backup rolls;
• incorporating a calibration device into a position of the roll which has been removed;
• giving a load in the vertical direction corresponding to a rolling load to a barrel portion of the backup roll;
• measuring at least one of the loads in the vertical direction given to an upper and a lower portion of the strip rolling mill via a load cell for measuring the rolling load;
• giving a load asymmetrical with respect to the upper and lower sides to the housings of the strip rolling mill via the top and the bottom backup roll chock when an external force in the vertical direction is given to the calibration device from the outside of the rolling mill under the condition that the load in the vertical direction is being given;
• and
• measuring the load given to the load cell.

A method of calibration of a strip rolling mill for finding a dynamic characteristic of the strip rolling mill with respect to a thrust force acting between the rolls of the multi-roll strip rolling mill composed of not less than four rolls including at least a top and a bottom backup roll and a top and a bottom work roll, comprising the steps of:

• drawing out rolls except for the backup rolls;
• giving a load in the vertical direction corresponding to a rolling load to a barrel portion of the backup roll under the condition that the rolls except for the backup rolls haven been removed;
• measuring loads in the vertical direction acting on both end portions of at least one of the top and the bottom backup roll via the load cells for measuring the rolling load;
• exerting a prescribed thrust force on a barrel portion of the backup roll under the condition that the load in the vertical direction is given;
• and
• measuring the load of the load cell.