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Tandem Cold Mill

Tandem Cold Mill

Tandem cold-mill solutions from Primetals Technologies stand for high product yields combined with flexible production, low operational costs and simplified maintenance work.

Depending on the product mix, the production capacity of continuous tandem mills from Primetals Technologies can exceed 1.2 million tons per year. The goal is to provide solutions that offer maximum added value for customers. Advanced mill stand actuators contribute to improved yield, user-friendly mill operation, and high-quality strip that lies within the specified tolerance values. Both 6-high and 4-high mill stands with their specific features and benefits are supplied on the basis of detailed analyses of product and customer requirements.

 Technology

Benefits

By joining coils prior to entering the mill, a continuous tandem cold mill results, provides additional benefits such as:

  • Highest production rates
  • Optimized yield
  • Reduced roll consumption
  • Flexible production
  • Tight tolerances for strip thickness, shape, and high surface quality
  • Low costs for operation, maintenance, and minimum down times
  • Fewer operators
  • Reduction in off-gauge material
  • Elimination of strip threading problems

Fig.1- Six-high cold mill stand  |  Fig.2- Five stand continuous cold tandem mill  |  Fig.3- Carrousel tension reel

Features

The Tandem mill consists of three to six mill stands arranged in series to progressively reduce the thickness of the strip in a single pass. A continuous tandem mill has a welder and accumulator looper at the entry end to join successive coils of pickled hot rolled material. This provides a large-scale mill that is capable of full automation to deliver the most advanced levels of quality and operating stability. It provides high production efficiency, and is used in the production of a broad range of steel types, from general construction materials to high-grade materials for automobile panels and other purposes.

Increasingly, for automotive steels, high-tensile materials at thinner gauges are being demanded to save vehicle weight and hence improve fuel consumption. As a result, higher performance is being demanded of the rolling mills. To meet this need, a continuous 5-stand tandem mill directly connected to the pickling line and using 6Hi UCM-Mill (Universal Crown Control mills) for all stands has become the standard. The UCM-Mill features:

  • Work roll bending
  • Intermediate roll bending
  • Intermediate roll shifting
  • Super heavy reduction
  • High strip shape control
  • Stable operation
  • Roll inventory reduction
  • Yield increase (by decreasing edge drop of the strip)

To cope with the high speed of delivery of the rolled strip a carrousel tension reel coils the strip on exiting the mill. This has two mandrels enabling the strip to be cropped on completion of a coil allowing the second mandrel to accept the oncoming strip without stopping the mill. 

 

Fig.4- Advantages of 6-high Universal Crown Control Mill (UCM) on strip flatness

 Automation


Plant productivity and product quality are substantially depending on the quality of plant automation, process control, and available process optimization functions.

To get the best performance out of a plant, Primetals Technologies provides add-on specific optimization solutions for further improvement of production efficiency and strip quality, besides standardized high performance automation system. 

Throughput maximization with:

  • OGO - Off Gauge Optimization for integrated rolling process
  • SOS - Speed Optimization System for throughput optimization 

Excellent Strip quality with:

  • REC - Roll Eccentricity Compensation for uniform and accurate strip thickness
  • CECO - Coil Eccentricity Compensation for uniform and accurate strip thickness
  • AFC - Model based Automatic Flatness control
  • ChatterMon / Mill Chatter Monitoring with automatic process speed adaptation

Production flexibility and special steel grades:

  • Precise mill setup by high-sophisticated Rolling models complying with changing production requirements and high strength steel qualities
  • Neural network based adaptation and setups promising high product flexibility and easy extension of the production to new materials
  • Optimized weld seam rolling supporting flexible production and obtaining minimum off-gauge

 Integrated Plants & Solutions

Integrated Plants & Solutions for tandem cold mill - Experience that Matters

Please follow the corresponding links to learn more about our competences:

 Innovation

​Minimum Quantity Lubrication

Flexible Roll-Gap Lubrication

Minimum Quantity Lubrication® (MQL) represents a new generation of roll-gap lubrication that applies pure rolling oil, very finely dispersed with air, directly onto the work-roll surface. The development consists of a novel design of the spray nozzles for lowest oil/air flow rates. The advantage is intelligent control of the oil film thickness depending on actual process and product parameters. MQL overcomes the existing limitations of classical emulsion technology in terms of flexibility by allowing for rapid lubrication changes to fulfil a range of different lubrication requirements.

MQL was successfully installed and tested on two different industrial tandem cold rolling mills in Europe. On both mills a significant improvement of strip surface cleanliness could be shown by an increase of surface reflexivity of 10%-points on average (Scotch-tape test). Furthermore, energy consumption could be reduced by up to 10% and rolling forces by up to 20% per stand.

MQL represents a technology package which can be simply installed on mills either as additional lubrication technology or to substitute the existing roll-gap lubrication. This allows a product dependent lubrication which fully exploits and extends the cold rolling mill capability.

The robust design of the MQL spray bar ensures low maintenance efforts

Main benefits

  • Significantly improved strip surface cleanliness
  • Reduced energy consumption (lower OPEX)
  • Increased work-roll lifetime

Chatterblock Control

Elimination of Third-octave Gauge Chatter on Tandem Cold Rolling Mills

Rolling mills are prone to many different vibration phenomena, especially when operating at high speeds and when rolling high-strength steels and thin product gauges. The most destructive form is called third-octave gauge chatter, a type of self-excited vibration.

A unique solution, ChatterBlock® Control, fully eliminates third-octave gauge chatter, as proven on a 5-stand tandem cold-rolling mill. With ChatterBlock® Control, chatter-critical products can be rolled at a maximum pass-schedule speed without any quality degradation.

As the leading supplier of vibration consultancy services and solutions, Primetals Technologies has developed ChatterBlock®Control, a unique solution for active chatter damping. ChatterBlock® Control represents an autonomous technology package that can be easily adapted to a mill to free it from unwanted third-octave chatter and thereby increase productivity and raise product quality. 

The ChatterBlock® Control valve block attached to the roll force cylinder

Main benefits

  • Complete elimination of third-octave gauge chatter
  • Proven on a 5-stand tandem cold-rolling mill
  • Increased productivity
  • Improved product quality


Reference Story

TCM for Thin Gauge and High Speed Rolling

Customer:
POSCO-Vietnam PL-TCM (TCM Section) / Phu My, Vietnam

Main Specification:
Material: Low Carbon Steel, High Strength Steel
Strip Thickness: Entry 1.8 to 5.0 mm, Delivery 0.15 to 1.6 mm (For Construction)
Strip Width: 700 to 1,570 mm
Coil Weight: Max. 35,000 kg
Rolling Speed: Max. 1,700 m/min
Mill Type: 6Hi UCM-Mill (No.1 to 5 Stand)

 

 

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