A cold rolling mill for cold‑rolled ribbed steel bars is a metal‑processing device for construction and metallurgy sectors. It takes ordinary low‑carbon hot‑rolled wire rod such as Q235 as raw material. Through continuous procedures including cold‑rolling diameter reduction, surface rib imprinting and on‑line heat treatment, the mill produces deformed steel bars with crescent transverse ribs.
This cold rolling mill leverages cold‑work hardening to boost tensile and yield strength of steel bars. Meanwhile, induction heating annealing improves ductility, so finished products deliver better comprehensive performance than conventional hot‑rolled rebars. Manufactured cold‑rolled ribbed steel bars save steel consumption, cut project costs and form strong bonding force with concrete. Builders widely adopt these rebars for cast‑in‑place floor slabs, roof panels, shear walls and prefabricated components. Modern cold rolling mills support high‑speed operation up to 1000 m/min, automatic control and eco‑friendly production. They can produce CRB550, CRB600H and other high‑grade rebars complying with GB 13788‑2024 standard.
Basic Information
- Alternative Name: Cold‑rolled Ribbed Steel Bar Production Line
- Equipment Type: Metal processing equipment
- Application: Building construction, bridges, tunnels, precast components
- Core Processes: Cold rolling diameter reduction, rib imprinting, induction heating
- Executed Standard: GB 13788‑2024 Cold‑rolled Ribbed Steel Bars
Development History
Early cold‑rolled ribbed steel bar technology originated in Europe in the late 1960s. In 1968, Germany, Netherlands and Belgium developed relevant manufacturing equipment. From 1973 onward, this technology gained massive promotion across Europe and North America, together with matched national standards.
China imported this technology in the late 1980s. Domestic enterprises introduced 11 complete sets of equipment from Germany and Italy, and built joint‑venture plants in Anhui, Guangdong and other regions. Those early production lines adopted single‑stand or simple continuous rolling units for LL550‑grade products, yet suffered poor ductility.
Entering the 21st century, China’s booming infrastructure raised market demand for high‑performance rebars. Since 2005, local manufacturers have solved the industry bottleneck of balancing strength and ductility for cold‑rolled steel bars. In 2007, new production lines combining cold and hot rolling came into service to realize fully automatic continuous production and greatly raise elongation performance.
In 2014, the 6th‑generation high‑ductility cold‑rolled ribbed steel bar coil line rolled out. Its rolling speed hit 1000 m/min and reached world‑class level. This technical progress also supported the implementation of GB 13788‑2024 new national standard.
Structure of Cold Rolling Mill
Modern cold rolling mills run as complete production lines with multiple core subsystems.
Pay‑off System
The pay‑off system supplies continuous raw material for the whole line. Most lines adopt double high‑position pay‑off stands: one works in production while the other serves as standby. When one wire rod coil finishes feeding, an automatic butt‑welding device connects coil ends without shutdown. This design largely reduces material‑changing downtime.
Descaling System
The descaling unit removes oxide scale on hot‑rolled wire rod surfaces. Oxide scale will scratch work rolls and damage finished surface quality without proper removal. Advanced units apply repeated roller bending or high‑pressure water washing. Fully‑enclosed housing and dust‑removal modules protect operators and lower dust pollution.
Main Rolling Unit
The main rolling unit acts as the core of the cold rolling mill. It consists of pre‑rolling mill and main rolling mill. The pre‑rolling mill completes preliminary diameter reduction and flattening for subsequent rib forming. The main rolling mill uses actively driven work rolls. Roll surfaces with crescent tooth patterns precisely press transverse ribs onto steel bars. Sealed housing and automatic cooling systems support long‑time stable running.
Control & Heating System
The whole production line applies PLC and touch‑screen for centralized operation. Operators achieve stepless speed adjustment, automatic fault diagnosis and one‑click parameter setting.
To eliminate internal stress from cold deformation and improve ductility, the line equips medium‑frequency or super‑audio induction heating cabinets. Accurate heating and cooling parameters realize on‑line recrystallization annealing. Final steel bars obtain yield strength above 500 MPa and improved elongation property.
Working Principle
Diameter Reduction and Rib Imprinting
The cold rolling mill works based on metal plastic deformation. Hot‑rolled wire rods pass through reduction rolls to shrink to target sizes, for instance from Φ6.5 mm down to Φ5.5 mm. Afterwards, material flows into rib‑imprinting rolls. Roll tooth patterns press two‑sided or three‑sided crescent ribs onto steel bar surfaces.
Deformation shapes bar geometry and strengthens bonding performance with concrete. Cold‑work hardening also raises mechanical strength of base metal.
Strengthening Mechanism
Cold rolling stretches and fractures metal grains, and increases dislocation density. This process improves strength and hardness but reduces plasticity and toughness. On‑line induction annealing follows rolling procedures to trigger metal recrystallization. It relieves partial internal stress and restores ductility, so final products own both high strength and acceptable elongation.
Main Product Classification
Two‑sided Ribbed Bar
This category mainly manufactures high‑ductility CRB600H cold‑rolled ribbed steel bars. Two opposite crescent ribs meet shape requirements of GB 13788‑2024. Special rolling processes guarantee post‑fracture elongation no less than 12%.
Three‑sided Ribbed Bar
Three‑sided ribbed equipment produces CRB550 and CRB650 grade steel bars. Evenly distributed three crescent ribs deliver superior concrete bonding performance. According to new national standard, CRB550 and CRB650 products must adopt three‑sided rib profiles.
Application Fields
Cold‑rolled ribbed steel bars from cold rolling mills serve various construction scenarios. CRB550 bars work as main reinforcement and distribution steel for cast‑in‑place floors, roof slabs, shear wall distribution bars and beam‑column stirrups in residential and public buildings.
For infrastructure projects, these rebars apply to highway pavements, airport runways and tunnel engineering. Besides, CRB650 and CRB800 grades fit pre‑stressed concrete components such as precast hollow slabs and electric poles.