SGA Rolls for Demanding Long-Product and Pipe-Mill Stands
LONSUN supplies acicular nodular cast iron rolls, also known as SGA rolls, for section, bar, wire, pipe, tube and universal mill applications. Grade selection connects hardness and strength with pass duty, thermal load, current wear and mill-incident risk.
Discuss Your SGA Roll RequirementSGA rolls use a bainitic-acicular-martensitic matrix alloyed with nickel, manganese and chromium. Compared with standard SGP rolls, this material direction provides higher hardness, wear resistance and resistance to fire cracking. Static monoblock and centrifugal double-pour casting routes are available according to the design.
SGA Grades and Stand Applications
SGA is considered where long-product or pipe-mill duties require a stronger and harder nodular-iron direction than standard pearlitic SGP.
| APPLICATION AREA | TYPICAL POSITION | COMMON REQUIREMENT | DATA TO REVIEW |
|---|---|---|---|
| Medium section, bar and wire mills | Intermediate and finishing stands | Improve wear and pass retention while preserving practical toughness | Pass, speed, load, product mix, stock temperature, cooling and current wear |
| Pipe and tube mills | Forming, sizing, reducing and straightening stands | Maintain geometry and surface stability under repeated contact | Tube size, roll function, speed, contact pattern, cooling and surface requirement |
| Universal mills | Roll sleeves | Match strength, hardness, fit and application load | Sleeve/shaft drawing, interference, mounting method, load and inspection |
Although SGA is harder than standard SGP, the final choice must still account for toughness margin, stand incidents, pass geometry and the agreed casting route.
Material Structure and Technical Reference
Nickel and molybdenum support the acicular matrix direction, while magnesium controls nodular graphite formation. The published ranges below must be tied to the selected grade and acceptance specification.
Chemical Composition
| Symbol | C | Si | Mn | Cr | Ni | Mo | Mg |
|---|---|---|---|---|---|---|---|
| SGA I | 2.90-3.60 | 1.20-2.20 | 0.20-0.80 | 0.20-1.00 | 3.01-3.50 | 0.50-1.00 | ≥0.04 |
| SGA II | 2.90-3.60 | 1.00-2.00 | 0.20-0.80 | 0.30-1.50 | 3.51-4.50 | 0.50-1.00 | ≥0.04 |
Physical Properties
| Symbol | Barrel Hardness | Roll Neck Hardness | Tensile Strength (MPa)* |
|---|---|---|---|
| SGA I | 55-78 HS | 35-45 HS | ≥350/450 MPa |
| SGA II | 60-80 HS | 35-45 HS | ≥350/450 MPa |
* The published tensile-strength cells use paired values (≥350/450 MPa). Confirm which value applies to the selected casting route, together with hardness scale, test location and acceptance method.
Higher hardness does not remove the influence of pass design, alignment, thermal cycling and mill incidents. Review the complete operating and inspection record.
| SYMPTOM | POSSIBLE AREAS TO CHECK | INFORMATION NEEDED |
|---|---|---|
| Rapid or localized wear | Grade/hardness match, contact pressure, slip, pass profile, guides and cooling | Stand, pass, product mix, wear map, tonnage, diameter and grinding loss |
| Thermal checking | Repeated temperature gradient, cooling interruption, stoppage, cobble and crack removal | Crack map, event/cooling log, campaign and grind/NDT history |
| Spalling or peeling | Crack propagation, indentation, local overload, internal indication and redressing quality | Roll ID, incident history, photographs, spall depth, fragments and NDT result |
| Pipe or product surface marks | Roll surface, contact pattern, roughness, alignment, debris and cooling/lubrication | Defect pitch, product side, roll photographs, setup and process trend |
| Sleeve or neck distress | Fit, bearing/chock condition, alignment, fillet geometry, torque and handling | Drawing, assembly method, damage location, load/event data and inspection |
Safety note: visible spalling, deep or growing cracks, sleeve or neck distress, abnormal vibration/noise, coolant loss or a major cobble requires action under the mill’s own safety procedure.
RFQ and Procurement Checklist
A complete RFQ reduces repeated clarification and prevents the quotation from being based only on size and hardness. The buyer’s data and the supplier’s confirmation should form one technical-commercial baseline.
| RFQ ITEM | BUYER PROVIDES | LONSUN CONFIRMS |
|---|---|---|
| Drawing and dimensions | Drawing revision, barrel and neck dimensions, fillets, grooves or pass details, and mounting features | Manufacturing scope, tolerances, machining, working layer where applicable, and drawing exceptions |
| Mill and application | Mill type, stand, roll function, rolled product, steel grade and pass | Proposed SGA grade, hardness and application basis |
| Operating conditions | Rolling force, torque, reduction, speed, stock temperature, cooling and lubrication where used | Material direction, key operating risks and inspection conditions |
| Current performance | Current roll material, hardness, campaign, wear, grinding and incident history | Comparison basis, evaluation method and technical risks to monitor |
| Quality documents | Required chemistry, hardness, microstructure, NDT, dimensions and third-party inspection | Test method, coverage, acceptance criteria and document list |
| Commercial requirement | Quantity, destination, required delivery date, packaging and Incoterm | Price basis, production scope, delivery basis, packing and quotation validity |