Ductile infinitely chilled cast iron has good wear resistance and heat resistance and is suitable for rolling environments under high temperatures and high pressure. The ductile graphite structure of ductile iron can provide a certain degree of toughness, which helps the roll not easily break when under pressure. It has good cooling and hardening properties, can quickly dissipate heat during the rolling process, and maintains the hardness and shape stability of the roll, thereby ensuring the dimensional accuracy of the rolled products. SGIV rolls can withstand the wear of metal blanks under high-speed friction, extending the service life of the rolls. SGIV rollers are suitable for bar rolling mills and can meet the rolling needs of metal bars of different diameters and materials, including ordinary carbon steel, alloy steel, etc. SGIV rolls can improve the production efficiency and product quality of the rolling mill, and reduce downtime during the production process and the frequency of roll replacement, thereby reducing production costs.
Hardness HSD: 55-70
Nickel composition %: 0.5-1.0
Suitable for racks: Roughing
Usage: Roughing and intermediate stands of bar and wire mills, section mills
| Chemical Composition % | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Symbol | C | Si | Mn | P | S | Cr | Ni | Mo | Mg |
| SGⅣ | 2.90-3.60 | 0.80-2.50 | 0.40-1.20 | ≤0.25 | ≤0.03 | 0.20-0.60 | 0.50-1.00 | 0.20-0.80 | ≥0.04 |
| SGⅤ | 2.90-3.60 | 0.80-2.50 | 0.40-1.20 | ≤0.20 | ≤0.03 | 0.30-1.20 | 1.01-2.00 | 0.20-0.80 | ≥0.04 |
| Prosperities & Application | ||||
|---|---|---|---|---|
| Symbol | Hardness | Tensile Strength | Dimension | Application |
| HSD | MPa | MM | ||
| SGⅣ | 55-70 | ≥320 | ￠300-1300 | Roughing and intermediate stands of bar and wire mills, section mills |
| SGⅤ | 60-70 | ≥320 | ||
SGIV rolls combine two microstructural ideas in one casting. The working layer follows an infinite chill design: hardness declines gradually from the surface inward instead of dropping off sharply after a thin outer shell. A hard carbide-bearing matrix does the cutting-edge work of resisting the hot bar, and it stays effective as the pass surface is dressed or turned down over the roll's campaign.
Spheroidal graphite nodules are distributed through this matrix. Unlike flake graphite, rounded nodules do not act as built-in crack starters. They blunt and redirect micro-cracks, which gives the roll a degree of toughness that conventional chilled irons struggle to match. The result is a roll with a hard, stable working face supported by a more forgiving body. This balance is why SGIV is positioned among the dependable Bar Rolling Mill Rolls for stands that see both abrasion and shock loading.
The carbide-rich working layer resists the constant sliding contact between roll and hot bar. Groove profiles hold their shape longer, so each roll delivers more tonnage before it has to be changed.
Bar rolling subjects roll surfaces to repeated heating by the stock and cooling by water. SGIV maintains its hardness through these cycles and shows good resistance to heat checking, helping surfaces stay smooth instead of developing deep thermal cracks.
Nodular graphite improves the roll's ability to absorb bite shocks and uneven loading. This lowers the risk of chipping or breakage when a cold end, an off-gauge billet, or a sudden load spike enters the pass.
Efficient heat transfer from the roll surface helps limit thermal distortion. Stable groove geometry means more uniform bar diameter and cross-section from the first piece to the last in a campaign.
A hard, uniform roll face wears evenly, which reduces groove roughening and the surface marks it would otherwise transfer to the product.
Fewer roll changes mean less downtime, less labor for stand changeovers, and reduced roll consumption per ton of steel. For mills running continuous schedules, these savings compound quickly.
SGIV is developed specifically for bar mills and can be applied across the rolling sequence:
Where billets arrive hot and thick, toughness and thermal shock resistance protect the roll against heavy reductions.
Balanced wear and strength support stable pass geometry as the section is progressively reduced.
Wear resistance and surface integrity matter most here, since the final bar dimensions and surface quality are determined in these passes.
In terms of product range, the rolls handle bars of different diameters and are suited to common grades such as plain carbon steel and various alloy steels. Because the infinite chill layer provides usable hardness at depth, grooves can be recut and passes re-dressed without quickly exposing a softer layer. This is valuable for mills that change sections frequently or run several bar sizes on the same stands. Roll dimensions, groove layouts, and hardness targets can be matched to the specific mill configuration and product mix.
Standard chilled rolls often have a hardness profile that falls quickly with depth and a brittle body. SGIV uses an infinite chill structure with nodular graphite, giving more consistent hardness through the working layer and better resistance to cracking.
They are intended for a broad range of bar diameters. Final suitability depends on the stand position, groove design, rolling temperature, and mill power, so it is best to select the grade and specification according to your actual rolling conditions.
Effective and even roll cooling, correct mill alignment, properly maintained guides, and timely pass dressing all matter. Good practice in these areas lets the material's wear and thermal properties work as designed and keeps campaign lengths predictable.
