High nickel content makes the rolls have good corrosion resistance and thermal stability, making them suitable for high-temperature and high-pressure rolling environments. The acicular bainite structure has good strength and toughness and can withstand high pressure and impact loads, ensuring the stability and safety of the rolling process. The spherical graphite structure of ductile iron provides better lubricity and wear resistance, reduces friction with the metal blank, and extends the service life of the roll. This material has good chilling and hardening properties and can maintain good hardness and shape stability at high temperatures to ensure the dimensional accuracy of rolled products. High-nickel acicular bainite ductile iron rolls have wear resistance and can withstand the friction and wear of metal blanks during high-speed rolling, extending the service life of the rolls. The SGAII roll can improve the production efficiency of the rolling mill, and reduce downtime during the production process and the frequency of roll replacement. The roll is suitable for various finishing mills and intermediate rolling mills and can meet the rolling needs of metal billets of different sizes and materials.
Hardness HSD: 60-80
Nickel composition %: 3.51-4.5
Suitable for racks: refined and rolled
| Chemical Composition % | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Symbol | C | Si | Mn | P | S | Cr | Ni | Mo | Mg |
| SGAⅠ | 2.90-3.60 | 1.20-2.20 | 0.20-0.80 | ≤0.01 | ≤0.03 | 0.20-1.00 | 3.01-3.50 | 0.50-1.00 | ≥0.04 |
| SGAⅡ | 2.90-3.60 | 1.00-2.00 | 0.20-0.80 | ≤0.01 | ≤0.03 | 0.30-1.50 | 3.51-4.50 | 0.50-1.00 | ≥0.04 |
| Prosperities & Application | ||||||||
|---|---|---|---|---|---|---|---|---|
| Symbol | Hardness | Tensile Strength | Dimension | Application | ||||
| HSD | MPa | MM | ||||||
| SGAⅠ | 55-78 | ≥350 | ￠300-1000 | Blooming and slabbing mills; large, medium, small section mills, wire mills, and narrow strip mills;pre-finishing stands of high-speed wire mills. | ||||
| SGAⅡ | 60-80 | ≥350 | ||||||
SGAII takes the bainitic design a step further by raising nickel to 3.51-4.5%, above the level used in SGAI. Nickel slows matrix transformation, favoring fine, needle-like bainite that develops evenly even in heavy roll sections, so the working layer behaves consistently from the surface inward.
Hardness is available across 60-80 HSD: the upper end suits wear-dominated stands, while the lower end suits positions where shock matters more. Centrifugal casting contributes a dense working layer, and the finished barrel is supplied as Precision Machined Mill Rolls, with diameters, journals, and groove positions held to the tolerances the mill requires.
Spheroidal graphite completes the structure. The nodules keep the body ductile and interrupt crack growth, so the added hardness does not turn into brittleness.
Higher achievable hardness and a uniform structure slow groove widening. Pass profiles stay close to their original shape through more tons of product, making campaign length easier to plan.
Continuous high-speed rolling pushes surface temperature up. The nickel-stabilized matrix resists softening and thermal fatigue, so roll surfaces stay smooth instead of crazing early.
Bainite supplies strength, and graphite nodules stop cracks before they spread. The roll tolerates pass overloads and uneven bites with lower risk of chipping or fracture.
Stable groove geometry converts directly into stable product size, so mills rolling tight-tolerance sections or wire make fewer adjustments across a campaign.
Longer campaigns mean fewer changeovers and less idle time. As roll consumption per ton falls, the higher alloy content is repaid through lower operating cost.
Placement follows the severity of duty, from heavy breakdown work to high-speed precision passes.
Blooming and slabbing mills demand strength and resistance to impact under large reductions. The bainitic structure and ductile body carry high separating force without sacrificing wear performance.
Large, medium, and small section mills and narrow strip mills present complex grooves and uneven loading. SGAII keeps profile accuracy and surface quality steady across these varied products.
Wire mills and the pre-finishing stands of high-speed wire mills combine speed, heat, and tight size control. Accurately finished grooves on Precision Machined Mill Rolls help hold wire dimensions consistent at line speed.
Billet size and material vary from mill to mill, so hardness level, barrel dimensions, and groove design should be matched to stand position, rolling speed, and cooling conditions.
Not automatically. Nickel adds cost and must be balanced with carbon, other alloys, and casting practice. The 3.51-4.5% range suits stands where deeper hardenability and heat stability justify it, while lighter-duty stands may be well served by a lower-nickel grade.
Start from the stand. Wear-dominated, high-speed positions lean toward the upper range, and positions with heavier shock lean lower. Rolling speed, reduction, cooling, and product tolerance should also be taken into account.
Yes. The hard layer extends to a useful depth, so grooves can be recut several times. Precision Machined Mill Rolls, together with the same care when regrooving, keep each new pass accurate.
