GB1582258A - Rolling of rod or bar - Google Patents

Description

(54) ROLLING OF ROD OR BAR (71) We, DAVY-LOEWY LIMITED, a British company, of Prince of Wales Road, Sheffield S9 4EX, Yorkshire, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a method of, and apparatus for, rolling metal rod or bar in a train of rod or bar mill stands.

When rolling metal rod or bar in a train of mill stands it is usual for the workpiece between adjacent stands to be in tension and the rolling speeds of the various stands are adjusted accordingly to keep the required interstand tensions. Certain metals such as some Al/Ti alloys cannot readily be rolled in a multi stand rolling mill because they are incapable of withstanding high tensile forces.

According to the invention in a method of rolling metal rod or bar it is passed through a train of at least two rod or bar mill stands with the rolls of the first stand of the train driven at constant speed and with excess torque over what is required to roll the rod or bar in that stand and with the rolls of the or each other stand of the train being driven with less torque than is required to roll the rod or bar in said the or each other stand such that between the stands the rod or bar is subjected axially to compression forces which are insufficient to cause buckling of the rod or bar.

Rolling under compression has the advantage of improving the physical properties of the rod or bar. This is particularly true in the case where the metal is derived from a continuous casting machine because the compression forces to the workpiece tend to close up any surface cracks which may be present in the cast metal.

Because the rolls of the or each other stand of the train is driven with less torque than is required to roll the rod or bar in that stand then the rod or bar is forced through the stand by the compressive forces applied to the rod or bar by the first stand in the set.

According to a further aspect of the invention apparatus for rolling metal rod or bar comprises a train of at least two rod or bar mill stands, the first stand being provided with means by which the speed of rotation of the rolls is kept constant and the or each other stand having torque control means which ensures that the torque supplied to the rolls of the or each other stand is less than that required to roll the rod or bar in said the or each other stand.

The speed control means applied to the first stand is well known apparatus and similarly the torque control means applied to the second stand and any subsequent stands of the train is also well known apparatus. Advantageously the drive motor of the or each stand is a hydraulic motor.

In order that the invention may be more readily understood a practical example thereof will now be described with reference to the accompanying drawing.

Apparatus for rolling metal rod comprising 19 mm diameter aluminium alloy comprises six roll stands of which the first three stands 1, 2, 3 are shown in the figure. In order to produce a workpiece of 9 2 mm diameter it has been calculated that the reduction on the stands 1 to 6 is as follows: 1 2 3 4 5 6 13% 32% 26% 25% 17% 9% These reductions give a total of 4:1 reduction and the driving motor 1A for the first stand is provided with a speed control device 1B by which the rolls can be rotated at a predetermined constant speed.It is calculated that the torque, in Newton metres, required on each of the stands to roll the workpiece applied to that stand is as follows: 2 2 3 4 5 6 578 1416 744 523 272 108 The drive motors of the stands, indicated by references 2A and 3A in the figure are each provided with torque control means 2B, 3B by which the torque applied to the rolls of the stands can be adjusted and then held at the predetermined value.

In the arrangement described the torque, in Newton metres, applied to the motors of the various stands is as follows: 1 2 3 4 5 6 1078 1216 644 423 222 58 It can be seen therefore that the torque applied to the first stand is considerably in excess of that required to roll the workpiece at the first stand, but at each of the subsequent stands the torque applied to the stand is less than that required to roll the workpiece at that stand.

Consequently apart from the first stand all the other stands operate with a torque less than that required to roll the workpiece and consequently it is only the fact that the workpiece is forced into the gap between the rolls of the stand by the excess torque on the first stand that the workpiece is rolled. The workpiece between each stand of the train is thus subjected to compression forces. Between the last stand of the train and a coiler the workpiece may be subjected to limited tensile forces but the workpiece has then been reduced to its required value and the material has been worked to such an extent that even those materials which as cast are incapable of withstanding tensile forces are now in a condition in which they can withstand limited tensile forces.

Clearly if the mill stands are spaced widely apart and the workpiece is of relatively small cross section there is the danger that the compressive force will be sufficient to cause buckling of the rod or bar between the stands. To this end the stands are located closely together, 500 mm between stand centres being suitable in the example described above.

WHAT WE CLAIM IS: 1. A method of rolling metal rod or bar in which it is passed through a train of at least two rod or bar mill stands and wherein the rolls of the first stand of the train are driven at constant speed and with excess torque over what is required to roll the rod or bar in that stand and the rolls of the or each other stand of the train are driven with less torque than is required to roll the rod or bar in said the or each other stand such that between the stands the rod or bar is subjected axially to compression forces which are insufficient to cause buckling of the rod or bar.

2. Apparatus for rolling metal rod or bar comprising a train of at least two rod or bar mill stands, the first stand being provided with means by which the speed of rotation of the rolls is kept constant, and the or each other stand having torque control means which ensure that the torque supplied to the rolls of the or each other stand is less than that required to roll the rod or bar in said the or each other stand.

3. Apparatus as claimed in claim 2, wherein the drive motors for the rolls of each stand are hydraulic motors.

4. A method of rolling metal rod or bar in a train of rod or bar mill stands substantially as hereinbefore described with reference to the example.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. constant speed. It is calculated that the torque, in Newton metres, required on each of the stands to roll the workpiece applied to that stand is as follows: 2 2 3 4 5 6 578 1416 744 523 272 108 The drive motors of the stands, indicated by references 2A and 3A in the figure are each provided with torque control means 2B, 3B by which the torque applied to the rolls of the stands can be adjusted and then held at the predetermined value. In the arrangement described the torque, in Newton metres, applied to the motors of the various stands is as follows:

1 2 3 4 5 6

1078 1216 644 423 222 58 It can be seen therefore that the torque applied to the first stand is considerably in excess of that required to roll the workpiece at the first stand, but at each of the subsequent stands the torque applied to the stand is less than that required to roll the workpiece at that stand.

Consequently apart from the first stand all the other stands operate with a torque less than that required to roll the workpiece and consequently it is only the fact that the workpiece is forced into the gap between the rolls of the stand by the excess torque on the first stand that the workpiece is rolled. The workpiece between each stand of the train is thus subjected to compression forces. Between the last stand of the train and a coiler the workpiece may be subjected to limited tensile forces but the workpiece has then been reduced to its required value and the material has been worked to such an extent that even those materials which as cast are incapable of withstanding tensile forces are now in a condition in which they can withstand limited tensile forces.

Clearly if the mill stands are spaced widely apart and the workpiece is of relatively small cross section there is the danger that the compressive force will be sufficient to cause buckling of the rod or bar between the stands. To this end the stands are located closely together, 500 mm between stand centres being suitable in the example described above.

WHAT WE CLAIM IS: 1. A method of rolling metal rod or bar in which it is passed through a train of at least two rod or bar mill stands and wherein the rolls of the first stand of the train are driven at constant speed and with excess torque over what is required to roll the rod or bar in that stand and the rolls of the or each other stand of the train are driven with less torque than is required to roll the rod or bar in said the or each other stand such that between the stands the rod or bar is subjected axially to compression forces which are insufficient to cause buckling of the rod or bar.

2. Apparatus for rolling metal rod or bar comprising a train of at least two rod or bar mill stands, the first stand being provided with means by which the speed of rotation of the rolls is kept constant, and the or each other stand having torque control means which ensure that the torque supplied to the rolls of the or each other stand is less than that required to roll the rod or bar in said the or each other stand.

3. Apparatus as claimed in claim 2, wherein the drive motors for the rolls of each stand are hydraulic motors.

4. A method of rolling metal rod or bar in a train of rod or bar mill stands substantially as hereinbefore described with reference to the example.