Tandem Rolling Process
Tandem cold rolling mills can be basically split into two groups; sheet mills if they reduce hot band to sheet gauge or tin mills if they roll the same incoming material to tinplate stock. Key advantages of the tandem rolling process include cost reduction and good improvements in productivity especially when integrated with a continuous casting process.
Rolling strip is widely used for automobile manufacturing, food packaging, household electric appliances, machinery, light industry, instruments, communications, military affairs and other fields.
In cold rolling, usually no heat is applied to the work piece before forming. Only some special steels like spring steel, tool steel, tempering steel or alloyed steels may be subjected to heat treatment before pickling and rolling. However, frictional energy at the contact surfaces of the work piece is converted to heat. This heat may increase temperatures in rapid adiabatic processes over 100°C.
The processing of steel in cold rolling mills differs considerably from the production in hot rolling mills. The raw material is first descaled (usually pickled, sometimes shot blasted and pickled), then cold rolled and heat treated. Further treatment steps include slitting, skin-pass rolling, coiling and packing.
Tandem cold rolling mills are named by their stand arrangement and designed as “sheet mills” if they reduce hot band to sheet gauge or “tin mills” if they roll the same incoming material to tinplate stock. A typical five stand tandem cold rolling mill is illustrated in Figure 1.
Figure 1: A typical five stand tandem cold rolling mill
The tandem rolling mill consists of several stands that the work material constantly passes through. At each stand the thickness of the work strip is reduced a certain amount. The total reduction between the first and last stand can be significant. There are technical problems associated with tandem rolling, caused particularly by the fact that the speed of the work material increases as it passes through each stand. In manufacturing practice, various control systems are used to keep the entire operation synchronized.
Once the particular technical problems and initial setup investment has been overcome, tandem rolling can provide a great advantages in the cost and productivity of an industrial metal rolling process. Tandem rolling can be even more advantageous when integrated with continuous casting.
Figure 2: Tandem rolling operation
The tandem cold rolling process is composed of treading, acceleration, run speed operation, deceleration and tailing out. Figure 3 illustrates a typical speed diagram for tandem cold rolling. It shows the threading is the first phase of the rolling. Following the threading, dynamic control loops (AGC and AFC) are closed and corresponding actuators are activated.
Then the mill speed is increased during the acceleration phase. Once the mill speed is up to the present maximum mill speed, the speed control system will keep the rolling speed in the vicinity of the maximum speed. This phase is defined as run speed operation. Towards the end of a coil, the mill is decelerated to the preset de-threading speed preparing the strip for tailing out. This session addresses individual phases and the disturbances accompanying these phases and control measures being taken in cold rolling.
Tandem Rolling Process, also known as the tandem rolling process, is an important concept in metallurgy, especially widely used in steel rolling production. Here is a detailed explanation of the Tandem Rolling Process:
I. Definition Tandem Rolling Process refers to the process in which multiple rolling mills are arranged in a certain order to continuously and uninterruptedly process the rolled products. In this process, the rolled products pass through multiple rolling mills in sequence, and each pass through a rolling mill receives a certain amount of reduction, gradually deforming the rolled products to achieve the desired size and shape.
II. Characteristics Continuity: Tandem Rolling Process achieves continuous and uninterrupted rolling of rolled products, greatly improving production efficiency. Efficiency: Multiple rolling mills work together to quickly complete the deformation processing of rolled products, reducing the production cycle. High precision: By precisely controlling the reduction and speed of each rolling mill, high-precision rolling of rolled products can be achieved. High degree of automation: Modern tandem rolling production lines are usually equipped with highly automated control systems, which can realize real-time monitoring and adjustment of the rolling process.
III. Application Tandem Rolling Process has a wide range of applications in steel rolling production, including both hot rolling and cold rolling.
Hot rolling: Hot rolling tandem production lines are usually used to produce hot-rolled strip steel, hot-rolled steel plates, and other products. After the rolled products are heated to a certain temperature in the heating furnace, they are sequentially rolled through roughing mills, finishing mills, and other rolling mills to obtain the desired hot-rolled products. Cold rolling: Cold rolling tandem production lines are mainly used to produce cold-rolled thin plates, tinplate, galvanized sheets, and other cold-rolled products. The cold rolling tandem production line usually includes uncoilers, multi-stand tandem mills, coilers, and other equipment, which further process hot-rolled products into cold-rolled products through a continuous and efficient rolling process.
IV. Technical challenges and solutions In the tandem rolling process, there may be some technical challenges, such as temperature control of the rolled products, rolling force balance, roller wear, etc. To address these issues, the following solutions can be adopted:
Optimize heating system: By setting the heating temperature and time of the heating furnace reasonably, ensure that the rolled products reach the appropriate temperature range before rolling. Precisely control rolling parameters: By real-time monitoring and adjusting the reduction, speed, and other parameters of each rolling mill, maintain the balance and stability of rolling force. Regularly replace rollers: Regularly check the wear of the rollers and replace severely worn rollers in a timely manner to ensure the quality of rolling.
V. Conclusion Tandem Rolling Process, as an efficient and precise rolling process, plays an important role in steel rolling production. With the continuous advancement of technology and the upgrading of equipment, the production efficiency and product quality of the tandem rolling process will be further improved.
The rolling process is one of the key technologies in metal processing, especially when producing flat products such as plates and strips. The process gradually reduces the thickness of the metal and achieves the desired mechanical properties through continuous rolling through a series of rolls. Here is a detailed overview of the rolling process:
Key concepts of rolling
Definition:
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- Rolling: A continuous process in which metal is gradually reduced in thickness by passing through multiple sets of rolls (or stands) arranged in series.
Purpose:
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- Thickness reduction: Achieve precise and uniform thickness of metal strip.
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- Improve mechanical properties: Increase strength, hardness and surface finish.
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- Improve production efficiency: Achieve higher output and continuous operation.
Stages of the rolling process
Preparation:
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- Material preparation: Preheat the metal to the appropriate temperature to ensure ductility and reduce rolling forces.
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- Initial rolling: Sometimes a single-stand mill is used for initial thickness reduction before the metal enters the rolling mill.
Rolling:
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- Multi-stand: The metal passes through multiple rolling stands (usually 4-7). Each stand has work rolls and support rolls.
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- Thickness reduction: Each set of rolls gradually reduces the thickness of the metal. The gap between the rolls is adjusted to achieve the desired reduction.
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- Speed coordination: The speed of the rolls in each stand is carefully controlled and synchronized to maintain tension and prevent defects.
Cooling and lubrication:
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- Cooling: Use water spray or other methods to cool the metal, maintain proper temperature and prevent overheating.
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- Lubrication: Use lubricants to reduce roll and metal friction, improve surface quality and extend roll life.
Finishing:
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- Final adjustments: The final stand is fine-tuned to ensure accurate thickness and surface finish.
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- Coiling: The rolled metal is coiled for easy handling and transportation.
Advantages of rolling
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- High productivity: Continuous operation achieves high output and high efficiency.
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- Uniform thickness: Multiple stands ensure consistent and accurate thickness control.
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- Improved material properties: Work hardening and controlled deformation improve mechanical properties.
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- Surface quality: Surface finish is better than single stand rolling process.
Applications
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- Automotive industry: Produces body panels and structural components.
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- Construction: Manufactures building materials such as roofing and siding.
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- Packaging: Manufactures metal cans and containers.
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- Consumer goods: Manufactures electrical and electronic housings.
Challenges and considerations
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- Roller wear: Metal contact causes roll wear, which requires regular maintenance and replacement.
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- Tension control: Maintaining proper tension prevents defects such as wrinkling or breaking of the metal strip.
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- Temperature management: Proper cooling and lubrication prevent overheating and ensure product quality.
In summary, the rolling process is an efficient and effective method,
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