Ring rolling is a hot forming process that produces seamless rings varying in size from a few inches in diameter, and weighing less than one pound, to over 25 feet in diameter and face heights approaching 10 feet. The process and equipment are similar in principle to rolling mills used for plate. In both processes, the metal is rolled between two rolls, which move toward each other to form a continuously reducing gap. In ring rolling, the rolls are of different diameters.
The process is shown schematically in Figure 1-5, Section 1. It begins with a hollow circular preform that has been upset and pierced, similar to preforms used for ring forging, illustrated in Figure 5-8. The preform is placed over the idler or mandrel roll, which is forced toward the drive roll. The drive roll rotates continuously, reducing the wall thickness, imparting the desired shape to the cross section, and increasing the diameter. Contours may be rolled on either the inside surface, outside surface or both as shown in Figure 1-6, Section 1.
For larger rings, the mill may also have radial oriented or "pinch" rolls, illustrated in Figure 5-16, which control the height of the ring. They also help to maintain squareness and alignment with virtually no axial growth. In some cases, such rolls can reduce the height as much as required. They are not, however, generally used to roll contours on either top or bottom surfaces.
Thickness-to-height ratios normally range from 16:1 to 1:16, and special equipment can extend these ranges. Cross sections of typical ring rolled shapes are shown in Figure 1-6, Section 1.
Ring rolling produces seamless rings with forged properties, which results in optimum mechanical properties, and predictable and efficient machinability. Tooling cost is low, set-up time is fast, rolled sections require little or no machining. The process is also highly material efficient. The preform typically utilizes up to 95% of the starting billet. Material losses come from the hole punched in the preform, oxidation in medium to large size rings, and any required machining.
Ring rolling can also be used in conjunction with other forging processes. In the example illustrated in Figure 5-17, a blank is formed by upsetting and piercing. The blank is then forged in impression dies to develop the hub, web and rim. The flange is then formed on the rim by ring rolling. In the final step, the wheel is dished to offset the hub from the rim.
It is important to the designer that the power of the rolling mill determines the deformation at the center of the wall during rolling. Excessively light reductions for each pass can cause dimensional problems. In rolling, the compressive deformation may be confined to the surface, and the mid-wall centers of the workpiece are stretched in tension. Experienced mill operators are familiar with the techniques required to roll to size.
In some cases the ring rolling sources have expanding mandrel or sizing machines, which expand the ring a few percent to improve dimensional control and roundness. Sizing may be performed either before or after normalizing. For rings rolled from aluminum alloys, these expanders are used to actually relieve quenching stresses introduced during solution heat treatment.
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Ring rolling is a hot forming process that produces seamless rings varying in size from a few inches in diameter, and weighing less than one pound, to over 25 feet in diameter and face heights approaching 10 feet. The process and equipment are similar in principle to rolling mills used for plate. In both processes, the metal is rolled between two rolls, which move toward each other to form a continuously reducing gap. In ring rolling, the rolls are of different diameters.
The process is shown schematically in Figure 1-5, Section 1. It begins with a hollow circular preform that has been upset and pierced, similar to preforms used for ring forging, illustrated in Figure 5-8. The preform is placed over the idler or mandrel roll, which is forced toward the drive roll. The drive roll rotates continuously, reducing the wall thickness, imparting the desired shape to the cross section, and increasing the diameter. Contours may be rolled on either the inside surface, outside surface or both as shown in Figure 1-6, Section 1.
For larger rings, the mill may also have radial oriented or "pinch" rolls, illustrated in Figure 5-16, which control the height of the ring. They also help to maintain squareness and alignment with virtually no axial growth. In some cases, such rolls can reduce the height as much as required. They are not, however, generally used to roll contours on either top or bottom surfaces.
Thickness-to-height ratios normally range from 16:1 to 1:16, and special equipment can extend these ranges. Cross sections of typical ring rolled shapes are shown in Figure 1-6, Section 1.
Ring rolling produces seamless rings with forged properties, which results in optimum mechanical properties, and predictable and efficient machinability. Tooling cost is low, set-up time is fast, rolled sections require little or no machining. The process is also highly material efficient. The preform typically utilizes up to 95% of the starting billet. Material losses come from the hole punched in the preform, oxidation in medium to large size rings, and any required machining.
Ring rolling can also be used in conjunction with other forging processes. In the example illustrated in Figure 5-17, a blank is formed by upsetting and piercing. The blank is then forged in impression dies to develop the hub, web and rim. The flange is then formed on the rim by ring rolling. In the final step, the wheel is dished to offset the hub from the rim.
It is important to the designer that the power of the rolling mill determines the deformation at the center of the wall during rolling. Excessively light reductions for each pass can cause dimensional problems. In rolling, the compressive deformation may be confined to the surface, and the mid-wall centers of the workpiece are stretched in tension. Experienced mill operators are familiar with the techniques required to roll to size.
In some cases the ring rolling sources have expanding mandrel or sizing machines, which expand the ring a few percent to improve dimensional control and roundness. Sizing may be performed either before or after normalizing. For rings rolled from aluminum alloys, these expanders are used to actually relieve quenching stresses introduced during solution heat treatment.
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Ring rolling is a hot forming process that produces seamless rings varying in size from a few inches in diameter, and weighing less than one pound, to over 25 feet in diameter and face heights approaching 10 feet. The process and equipment are similar in principle to rolling mills used for plate. In both processes, the metal is rolled between two rolls, which move toward each other to form a continuously reducing gap. In ring rolling, the rolls are of different diameters.
The process is shown schematically in Figure 1-5, Section 1. It begins with a hollow circular preform that has been upset and pierced, similar to preforms used for ring forging, illustrated in Figure 5-8. The preform is placed over the idler or mandrel roll, which is forced toward the drive roll. The drive roll rotates continuously, reducing the wall thickness, imparting the desired shape to the cross section, and increasing the diameter. Contours may be rolled on either the inside surface, outside surface or both as shown in Figure 1-6, Section 1.
For larger rings, the mill may also have radial oriented or "pinch" rolls, illustrated in Figure 5-16, which control the height of the ring. They also help to maintain squareness and alignment with virtually no axial growth. In some cases, such rolls can reduce the height as much as required. They are not, however, generally used to roll contours on either top or bottom surfaces.
Thickness-to-height ratios normally range from 16:1 to 1:16, and special equipment can extend these ranges. Cross sections of typical ring rolled shapes are shown in Figure 1-6, Section 1.
Ring rolling produces seamless rings with forged properties, which results in optimum mechanical properties, and predictable and efficient machinability. Tooling cost is low, set-up time is fast, rolled sections require little or no machining. The process is also highly material efficient. The preform typically utilizes up to 95% of the starting billet. Material losses come from the hole punched in the preform, oxidation in medium to large size rings, and any required machining.
Ring rolling can also be used in conjunction with other forging processes. In the example illustrated in Figure 5-17, a blank is formed by upsetting and piercing. The blank is then forged in impression dies to develop the hub, web and rim. The flange is then formed on the rim by ring rolling. In the final step, the wheel is dished to offset the hub from the rim.
It is important to the designer that the power of the rolling mill determines the deformation at the center of the wall during rolling. Excessively light reductions for each pass can cause dimensional problems. In rolling, the compressive deformation may be confined to the surface, and the mid-wall centers of the workpiece are stretched in tension. Experienced mill operators are familiar with the techniques required to roll to size.
In some cases the ring rolling sources have expanding mandrel or sizing machines, which expand the ring a few percent to improve dimensional control and roundness. Sizing may be performed either before or after normalizing. For rings rolled from aluminum alloys, these expanders are used to actually relieve quenching stresses introduced during solution heat treatment.
Return to Table of Contents
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