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Forged steel cold rolling rolls include work rolls and back up rolls. The main purpose of forged steel work rolls is to roll metal sheets in the cold rolling process. This type of roll uses advanced smelting equipment (electric arc furnace), refining equipment (electroslag remelting and ladle refining) and forging equipment (3150t hydraulic press) to manufacture alloy forged steel roll blanks with excellent metallurgical quality. In terms of heat treatment, computer control technology is applied Ensure roll hardness and roll body hardened layer depth have good reproducibility. In terms of heat treatment process, sufficient preparatory heat treatment and specific induction quenching (continuous and integral), cryogenic treatment and tempering are used to obtain a high-hardness and uniform working layer on the roll. The depth of the hardened layer can reach more than 30mm, with sufficient Wear resistance, toughness and accident resistance.
1. List of chemical compositions of work rolls
Steel grade | Chemical composition/% | |||||||||
C | Si | Mn | Cr | Mo | V | Ni | Cu | S | P | |
9Cr2 | 0.80-0.95 | ≤0.40 | ≤0.40 | 1.30-1.70 | — | — | — | — | ≤0.030 | |
8Cr2MoV | 0.80-0.90 | 0.15-0.40 | 0.30-0.50 | 1.80-2.40 | 0.20-0.40 | 0.05-0.15 | ≤0.25 | ≤0.025 | ||
9Cr2Mo | 0.85-0.95 | 0.25-0.45 | 0.20-0.35 | 1.70-2.10 | 0.20-0.40 | — | ||||
9Cr2MaV | 0.20-0.30 | 0.10-0.20 | ||||||||
9Cr3Mo | 2.50-3.50 | 0.20-0.40 | — | |||||||
8Cr3MoV | 0.78-1.10 | 0.40-1.10 | 0.20-0.50 | 2.80-3.20 | 0.20-0.60 | 0.05-0.15 | ≤0.80 | ≤0.25 | ≤0.025 | |
8Cr5MoV | 0.78-0.90 | 0.40-1.10 | 0.20-0.50 | 4.80-5.50 | 0.20-0.60 | 0.10-0.20 | ≤0.020 | |||
2. Surface hardness of work roll body
No. | surface hardness（HSD） | Recommended use |
1 | ≥95 | Work rolls for skin pass and finish mills |
2 | 90-98 | Work rolls for metal plates and strips |
3 | 75-90 | Work rolls for preliminary [rough] rolling of metal plates and strips Cold rolling intermediate rolls for metal plates and strips |
3. Surface hardness of work roll neck
No. | surface hardness(HSD) |
1 | 30-50 |
2 | 50-65 |
3 | 75-90 |
4. The two edges of the work roll body surface are allowed to have soft zone areas that are lower than the hardness requirements. The width of the soft zone is defined as "the distance measured from the edge of the cylindrical surface of the roll body along the generatrix to the point where the hardness meets the pattern requirements." For work rolls, the soft belt width of work rolls that require surface hardness of 95HSD or above is allowed to be increased by 20% from the value in the table.
Allowable soft strip width on both edges of work roll body：
Roll length mm | ≤300 | 301-600 | 601-1000 | 1001-2000 | ≥2001 |
The allowed soft band width is no greater than | 25 | 45 | 50 | 55 | 65 |
5. Hardened layer depth of cold rolling work roll body
Roll length/mm | hardness range(HSD) | Hardened layer depth/mm, not less than | ||
2%Cr | 3%Cr | 5%Cr | ||
≤300 | ≥95 | 6 | 15 | 15 |
90～96 | 8 | 20 | 20 | |
75～90 | 10 | |||
301～500 | ≥95 | 7 | 20 | 25 |
90～96 | 12 | 25 | 30 | |
75～90 | 14 | — | ||
>500 | ≥95 | 8 | 20 | 25 |
90～96 | 13 | 25 | 35 | |
75～90 | 15 | |||
6. Surface quality of cold rolling work rolls
6.1 No cracks, visually visible pits, non-metallic inclusions, pores and other surface defects that affect use are allowed on the working surfaces of the cold rolling work roll body and roll neck.
6.2 The surface roughness of the cold rolling work roll body and roll neck should comply with the drawings. The roughness not noted on the drawing should generally reach Ra1.6.
