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5 Chrome
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This is the new standard of Back-Up Roll for high productivity mills requiring extended campaign lengths and superior wear performance.
These improved properties are achieved through the production of a Monobloc Static Cast Roll with an analysis derived in part from a family of tool steel materials. These rolls are produced to a higher hardness level of up to 73 Shore C through a differential hardening process. The greatly enhanced wear properties produced can be related to a higher percentage of more complex carbides within a matrix of tempered acicular products.
In the differential hardening process, the rolls are first treated to produce the optimum journal/neck structure for meeting the mechanical requirements of the mill. The barrel surface layer is then heated to a controlled depth by means of a special Rotary Selas Furnace. The optimum wear resistant rolling structure is then obtained through a controlled water quench and isothermal hold. Finally, the roll is given a tempering treatment to achieve the appropriate hardness.
As the 5 Chrome Roll will achieve significantly longer total service life, the Monobloc Casting Method is preferred over the Duplex Casting Method to prevent potential shell to core bond problems. The rolls still retain the benefits of the traditional differentially hardened alloy cast steel materials, showing excellent durability, high strength and spall resistance.
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Applications
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| Product |
Type of Mill |
Position |
| Hot Rolled Coil |
4 High Roughing / Finishing |
Back Up Rolls |
| Plate |
4 High Roughing / Finishing |
Back Up Rolls |
| Aluminium |
4 High Roughing / Finishing |
Back Up Rolls |
| Cold Rolled Coil |
4 High Tandem |
Back Up Rolls |
| Cold Rolled Coil |
4 High Temper / DR |
Back Up Rolls |
| Cold Rolled Coil |
4 High Galv / Skin Pass |
Back Up Rolls |
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Typical Mechanical Properties
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N/mm2 |
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| Property |
Barrel Surface |
Journals & Axis |
| Tensile Strength |
1400 |
750 |
| Bending Strength |
1900 |
1030 |
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Typical Hardness Gradient
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Micrograph x 500
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Typical Analysis
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| Code |
Leeb E |
Shore C |
C |
Si |
Mn |
Ni |
Cr |
Mo |
| 5 Chrome |
690-730 |
67/73 |
0.3/0.7 |
0.3/0.8 |
0.3/1.0 |
0.5 max |
3.5/6.0 |
0.5/1.0 |
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The Davy Roll Company Limited
Registered in England, Registration No. 162966, VAT registration 172 3848 50 501.
Registered Office: PO Box 21, Coulthards Lane, Close Works, Gateshead, Tyne and Wear, NE8 3DX.
The Davy Roll Company Limited is a member of the Union Electric Steel Corporation group of companies.
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