Unit 7

Hot rolling, Cold rolling

Hot rolling

Slabs are first reheated in reheating furnaces. There are two types of reheating furnaces: pusher furnaces and walking beam furnaces. They differ mainly in the way the slabs are transported through the furnace. In the pusher-type furnaces, the charging machine pushes the slabs transversely through the furnace. In the walking beam furnaces, water-cooled walking beams move the slabs longitudinally through the furnace. The slabs are ready to be rolled when they have reached a temperature of 1200 ˚C.


Exercise 1:

Please select technical terms from the text below and translate them:

Hot rolling
Slabs are first reheated in reheating furnaces. There are two types of reheating furnaces: pusher furnaces and walking beam furnaces. They differ mainly in the way the slabs are transported through the furnace. In the pusher-type furnaces, the charging machine pushes the slabs transversely through the furnace. In the walking beam furnaces, water-cooled walking beams move the slabs longitudinally through the furnace. The slabs are ready to be rolled when they have reached a temperature of 1200 ˚C.

Ikona iDevice Answer Key: Exercise 1
Suggested answers:

–

–

–

–

–

–

  

Prior to rolling, the scale layer of oxides formed on the slabs during reheating in the furnace has to be removed. This is done by the scale breaker which cleans the top and underside of each slab with a water jet. After this, the slab is transported by the roller table to the roughing stand and then onto the finishing mill. Just in front of the finishing train there are cropping shears that remove the head and the tail of the sheet. After the cropping shears, the sheet passes through a second scale breaker which removes the oxide scale that has again been formed on the steel. Each stand in the finishing mill reduces the thickness of the sheet until the final thickness required has been attained.

Exercise 2:

Please translate the following text into Czech:

Prior to rolling, the scale layer of oxides formed on the slabs during reheating in the furnace has to be removed. This is done by the scale breaker which cleans the top and underside of each slab with a water jet. After this, the slab is transported by the roller table to the roughing stand and then onto the finishing mill.

 

Ikona iDevice Answer Key: Exercise 2
  

Exercise 3:

Please translate the following text into Czech:

Just in front of the finishing train there are cropping shears that remove the head and the tail of the sheet. After the cropping shears, the sheet passes through a second scale breaker, which removes the oxide scale that has again been formed on the steel. Each stand in the finishing mill reduces the thickness of the sheet until the final thickness required has been attained.

Ikona iDevice Answer Key: Exercise 3
  

Because the sheets get progressively thinner, the strip speed increases from stand to stand. After rolling, the strip is cooled with water until the right temperature has been reached and finally it is coiled. After further cooling, the product can be sold as hot rolled coil or sheet (mill finish or unpickled), or sent to the cold rolling mill.
Ikona iDevice Exercise 4:
To do exercise 4, please scroll down to the end of the unit. It precedes exercise 7. Do the exercise and return back.
  

Cold rolling

After hot rolling, the strip carries a layer of oxide scale. This scale consists of a chemical compound of iron and oxygen and it is hard and brittle. To prevent these oxides being pressed into the sheet during subsequent processing, they have to be removed prior to cold rolling. This is done by pickling, during which the strip is passed through a warm acid bath. Some mills use hydrochloric acid and some sulphuric acid. Immediately after pickling, the steel strip is carefully rinsed and dried.

Ikona iDevice Exercise 5:
Please translate into Czech:

Hydrochloric acid - ( – triviální název)

Sulphuric acid -

Pickling -

Acid bath -

  

Pickling requires continuous and even contact between the pickling acid and the treated material. This means that the strip has to move through the pickling baths at as constant speed as possible. Coils are therefore joined head to tail at the entry to the pickling shop to produce a continuous strip. The join is made by means of a butt weld, whereby both ends are heated and then butted together. Subsequently the weld is planed to remove the excess thickness. The strip is then passed to the entry loop accumulator, which acts as a storage buffer between the discontinuous entry section and the continuous pickling section. After pickling, there is an exit accumulator to accommodate speed differences between the pickling process and the downstream treatment.

Exercise 6:

Please translate the following text into Czech:

Pickling requires continuous and even contact between the pickling acid and the treated material. This means that the strip has to move through the pickling baths at as constant speed as possible. Coils are therefore joined head to tail at the entry to the pickling shop to produce a continuous strip. The join is made by means of a butt weld, whereby both ends are heated and then butted together. Subsequently the weld is planed to remove the excess thickness. The strip is then passed to the entry loop accumulator, which acts as a storage buffer between the discontinuous entry section and the continuous pickling section. After pickling, there is an exit accumulator to accommodate speed differences between the pickling process and the downstream treatment.

Ikona iDevice Answer Key: Exercise 6

  

After pickling, rinsing and drying, the strip can be cut to the required width by the side trimmer. Subsequently, the strip is oiled, cut and coiled. The oil not only served as a protection against rust, but also acts as a lubricant during subsequent cold rolling. The shears cut the strip when the coil has reached the required size. The strip can be cut at the weld, or another location to obtain the required coil weight. The pickled coils can be sold as coils or sheets or can be passed on for further cold rolling.
Ikona iDevice Exercise 7:
To do exercise 7, please scroll down to the end of the unit. It precedes "Points to remember". Do the exercise and return back.
  

In the cold rolling section, the tandem mill reduces the strip to the thickness requested by the client. The further reduction in thickness is achieved by a combination of compression and tensile forces: pressure on the rolls and tension between the roughers. After leaving the last roll stand, the strip is coiled again.
Some mills operate an integrated pickling and tandem process, meaning that the coils can go straight on to be cold rolled immediately after pickling, without interruption.
Ikona iDevice Exercise 8:
Translate into Czech:

Tandem mill -

Rolls -

Rougher -

Roll stand -

 

  

Although the cold rolling in the tandem mills reduces the sheet to the required thickness, the steel has become hardened and cannot be further processed in this “full hard” state. The steel therefore has to be subjected to a thermal treatment, and this takes place in the annealing furnaces.

Exercise 9:

Translate the following text into Czech:

Although the cold rolling in the tandem mills reduces the sheet to the required thickness, the steel has become hardened and cannot be further processed in this “full hard” state. The steel therefore has to be subjected to a thermal treatment, and this takes place in the annealing furnaces.

Ikona iDevice Answer Key: Exercise 9

  

Ikona iDevice Exercise 4:
Read the text below and fill in the missing words:
Because the sheets get progressively thinner, the strip speed increases from to . After , the is cooled with water until the right temperature has been reached and finally it is . After further cooling, the product can be sold as hot rolled or sheet (mill or unpickled), or sent to the rolling mill.
  

Ikona iDevice Exercise 7:
Read the paragraph below and fill in the missing words.
After , rinsing and drying, the strip can be cut to the required width by the side . Subsequently, the strip is oiled, cut and . The oil not only served as a protection against rust, but also acts as a lubricant during subsequent rolling. The cut the strip when the has reached the required size. The strip can be cut at the , or another location to obtain the required weight. The coils can be sold as coils or sheets or can be passed on for further rolling.
  

Ikona iDevice Points to remember:

- Prior to hot rolling, slabs are reheated in reheating furnaces. There are two types of reheating furnaces: pusher furnaces and walking beam furnaces.

- During hot rolling, hot slabs are rolled into thin sheets; their heads and tails are cropped and coiled.

- Hot rolled coils can be subsequently cold rolled. Prior to cold rolling, scales are removed during pickling.

- After cold rolling, coils are in a “full hard” state.


Glossary:

 

English  Czech
Annealing furnace Žíhací pec
Butt weld Tupý svar
Coiling Svinování do svitků
Pickling Moření
Planed Zarovnaný
Rolling stand Válcovací stolice
Rolling train Válcovací trať
Roughing Předválcování
Scales Okuje
Walking beam furnace Kroková pec

Ikona iDevice Gallery:
Zobrazit obrázek Walking Beam Furnace
Walking Beam Furnace
Zobrazit obrázek Hot Rolling of Steel Slabs
Hot Rolling of Steel Slabs
Zobrazit obrázek Laminar Cooling
Laminar Cooling
Zobrazit obrázek Shears and Coiling
Shears and Coiling
Zobrazit obrázek Cold Rolling Rolling Stand
Cold Rolling Rolling Stand
Zobrazit obrázek Pickling 1
Pickling 1
Zobrazit obrázek Pickling 2
Pickling 2
Zobrazit obrázek Pickling 3
Pickling 3

Sources:

Applebaum, M, Everything You Always Wanted to Know About Steel. A Glossary of Terms and Concepts, Summer 1998, Solomon Smith Barney Inc., 2000

Coigne, P., Construction Market, ArcelorMittal Brussels, ArcelorMittal University - Understanding Steel, 2009

Meseure, K., Product range - Flat carbon steel for industry, ArcelorMittal R&D Gent, ArcelorMittal University - Understanding Steel, 2009

Meseure, K., Steel Making, ArcelorMittal R&D Gent, ArcelorMittal University - Understanding Steel, 2009

Meseure, K., Steel properties, ArcelorMittal R&D Gent, ArcelorMittal University - Understanding Steel, 2008

An Introduction to the Hot Strip Mill, John Lysaght (Australia) Limited, 1976

PC Translator. CD-ROM. Korytná:LangSoft & SOFTEX Software, 2007

http://alloytech.com/Default.asp

http://www.arcelormittal.com/fce

http://www.arvedi.it/

http://www.bchistory.org/beavercounty/SteelMakingEtc/SteelMaking.html

http://www.eef.org.uk/default.htm

http://www.evrazvitkovicesteel.com/

http://www.myarcelormittal.com

http://www.onesteel.com/

http://www.pdmsteel.com/index.html

http://www.steel.org/

http://www.steel-training.co.uk

http://www.stemcor.com/default.aspx

http://www.uss.com/corp/index.asp