850mm hot rolling mill

1. Equipment Overview
This is an 850mm hot rolling mill, manufactured by China First Heavy Machinery Co., Ltd. (CFHI) in 2006 and taken offline in October 2022. This is a large-scale wide hot rolling equipment package, covering the entire hot rolling process from slab roughing and finishing to coil winding. CFHI is a leading enterprise in China's heavy equipment manufacturing sector, with hot rolling equipment known for advanced design, precision manufacturing, and reliable operation. The line has an annual production capacity of 1.4 million tons, representing a medium-scale but fully configured hot rolling line.

2. Manufacturer Background
China First Heavy Machinery Co., Ltd. (CFHI) is one of the largest heavy equipment manufacturers in China, with world-class manufacturing capabilities in metallurgical rolling equipment, nuclear power equipment, and large forgings. CFHI's hot rolling lines, cold rolling lines, and levelers enjoy excellent reputations in domestic and international markets, with products known for high precision, good rigidity, and long service life.

3. Core Highlights — Large-Scale Heavy-Duty Design + All-DC Drive
This hot rolling line embodies the characteristics of large-scale heavy-duty equipment:

• The vast majority of main motors adopt DC drives, offering high starting torque, wide speed range, and strong overload capacity;

• Total line drive power exceeds 25,000kW, with an extremely ample power system;

• Finishing stands adopt 4-Hi four-high structure with HAGC (Hydraulic Automatic Gauge Control) ensuring finished thickness accuracy;

• The roughing mill adopts 2-Hi two-high structure with mechanical screwdown, with a maximum rolling force of 12000kN.

4. Raw Material Specifications

• Slab width: 750mm (mild steel), 650mm (stainless steel);

• Slab thickness: 150mm, 180mm, 200mm;

• Slab length: 6900mm;

• Materials: Stainless steel (200 series, 300 series, 400 series), mild steel, high-carbon steel.

The line can process a wide range of materials, from plain carbon steel to high-end stainless steel, demonstrating broad material adaptability.

5. Finished Product Specifications

• Finished width: 400-750mm;

• Finished thickness: 1.2-12mm—covering from 1.2mm thin gauge to 12mm thick gauge, with an extremely wide range;

• Coil diameter: Minimum 520mm, maximum 1500mm;

• Coil weight: Maximum 8 tons.

6. Roughing Zone (R1 + E1 + E2)

R1 (Roughing Mill) :

• Type: 2-Hi (two-high) , with simple structure and good rigidity, suitable for large-reduction breakdown rolling;

• Work roll diameter: Φ1050/950mm (new 1050mm, replaced when worn to 950mm);

• Barrel length: 900mm;

• Maximum rolling force: 12000kN (approximately 1200 tons of force);

• Motor power: 5500kW (DC), voltage 1050V;

• Screw-down method: Mechanical screwdown—reliable structure suitable for roughing with large reductions.

E1 (Edger 1) :

• Type: Vertical edging mill for width control and side rolling of slabs;

• Work roll diameter: Φ750/700mm;

• Barrel length: 400mm;

• Maximum rolling force: 1500kN;

• Motor power: 638kW (DC), voltage 660V;

• Equipped with hydraulic AWC (Automatic Width Control) and SSC (Short Stroke Control) for precise width control.

E2 (Edger 2) :

• Work roll diameter: Φ500/450mm;

• Barrel length: 310mm;

• Maximum rolling force: 500kN;

• Motor power: 162kW (DC), voltage 440V.

The two edging stands in series achieve precise width control during roughing, ensuring finished width accuracy.

7. Finishing Zone (F1-F7) — 7-Stand 4-Hi Continuous Finishing
The finishing zone consists of 7 continuous stands (F1-F7) , all adopting 4-Hi (four-high) structure:

• Work roll: Diameter Φ480/430mm, barrel length 900mm;

• Backup roll: Diameter Φ850/730mm, providing robust support to work rolls;

• Maximum rolling force: F1-F5 at 8000kN each, F6-F7 at 6000kN each (reduced deformation at final stands);

• Motor power: 2400kW each (DC), voltage 870V;

• 7 finishing stands total motor power: 16800kW;

• Screw-down method: HAGC (Hydraulic Automatic Gauge Control) with fast response and high control precision.

Finishing Mill Technical Features:

• Work roll barrel length 900mm, effective rolling width 750mm, with ample margin;

• 4-Hi structure provides high rigidity, ensuring shape and thickness accuracy under 8000kN rolling force;

• HAGC system enables real-time precise roll gap adjustment during high-speed rolling, ensuring finished thickness tolerance;

• 7-stand continuous arrangement—the strip passes through all stands in a single pass, reducing thickness progressively.

8. Coiling Area
The coiling area is equipped with 2 down coilers, responsible for winding finished strips into coils. The dual-coiler configuration enables"one active, one standby"or alternating operation, reducing downtime for coil changes and improving continuous production efficiency.

9. Total Drive Power Summary

Total main motor power of the entire line reaches 23,100kW. Including roller table motors, hydraulic systems, and auxiliary equipment, the total installed power exceeds 25,000kW. This is a medium-wide hot rolling line with an extremely ample power configuration.

10. Product Coverage — Broad Adaptability for Stainless Steel + Carbon Steel
The line can produce an extremely wide range of materials:

• Stainless steel: Covering 200 series (such as 201), 300 series (such as 304), and 400 series (such as 430) mainstream stainless steel grades;

• Mild steel: Q195, Q235, and other plain carbon structural steels;

• High-carbon steel: Tool steel, spring steel, and other high-carbon content grades.

Stainless steel hot rolling has higher requirements for temperature control, rolling force control, and surface quality control. The line's ability to stably roll stainless steel reflects its high level of process control.

11. Thickness Coverage — 1.2-12mm Wide Range Capability
The finished thickness coverage from 1.2mm to 12mm is another major advantage of this line:

• 1.2mm thin gauge: Represents thin-gauge hot-rolled strip, usable directly as cold rolling raw material or for thin sheet applications;

• 12mm thick gauge: Falls into the hot-rolled medium plate range, usable for structural components and pressure vessel manufacturing;

• The wide coverage from thin to thick enables the line to flexibly respond to different market demands.

12. Equipment Age and Condition
This equipment was manufactured in 2006 and taken offline in October 2022, with approximately 16 years of actual service. In hot rolling lines, 16 years represents the mid-to-late phase of the equipment lifecycle. However, considering that CFHI equipment is typically designed for longer service life (up to 25-30 years), this equipment still has considerable remaining service life. The October 2022 shutdown means the equipment was not long-idle but was in operation until shutdown, with relatively transparent condition.

13. Large-Scale Equipment Characteristics
This hot rolling line represents the typical characteristics of large hot rolling equipment:

• Roughing mill single motor 5500kW: The largest single motor power among all equipment introduced so far;

• Finishing mills 7 stands × 2400kW: High-power configuration of 7 continuous stands ensures stability for high-speed, large-reduction rolling;

• 12000kN roughing rolling force: Ensures large-reduction breakdown capability for thick slabs;

• Annual capacity 1.4 million tons: Standard capacity for medium-scale hot rolling lines.