Rolling
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Rolling is a metal forming process that reduces thickness or changes the cross-section of metal stock by compressive forces from rolls. There are two main types: flat rolling and shape rolling. Rolling can be done hot or cold depending on the temperature of the metal. Key rolling mill configurations include two-high, three-high, and four-high mills. Seamless pipes and tubes are formed through continuous processes without any welds, providing more reliable pressure retention than welded alternatives.
Rolling
- 2. TOPICS Rolling Flat Rolling Shape Rolling Rolling Mills Production Of Seamless Piping & Tubing Munim Shaukat (Lecturer) Mechanical Engineering Department University of Lahore
- 3. Rolling Process of reducing thickness or changing cross section by compressive forces applied through a set of rolls
- 4. A picture of the rolling mill: Adjusting Screw Rolls Rolls Housing/ Stand
- 5. Rolling Rolling is a bulk deformation process in which the thickness of the work is reduced by compressive forces exerted by two opposing rolls. The rolls rotate to pull and simultaneously squeeze the work between them.
- 6. Types Of Rolling Flat Rolling The final shape of the product is either classed as sheet or plate .
- 7. Draft In flat rolling, the work is squeezed between two rolls so that its thickness is reduced by an amount called the draft:
- 8. Calculation Of Draft D = to - tf where d: draft to: starting thickness tf : final thickness As a fraction of the starting thickness: % reduction = % r = (d/ to) * 100%
- 9. Structural Defects In Flat Or Sheet Rolling: Wavy Edges Center cracking Edge cracking Alligatoring
- 10. Shapes Rolling The final product may be a round rod or other shaped bar, such as a structural section (beam, channeletc)
- 11. CLASSIFICATION OF ROLLING AS ANY OTHER METAL FORMING PROCESS, ROLLING CAN BE PERFORMED HOT (HOT ROLLING) OR COLD (COLD ROLLING). MOST ROLLING IS CARRIED OUT BY HOT ROLLING, OWING TO THE LARGE AMOUNT OF DEFORMATION REQUIRED.
- 12. Hot Rolling Rolling is classified according to the temperature of the metal rolled. If the temperature of the metal is above its recrystallization temperature, then the process is termed as hot rolling
- 13. RECRYSTALLIZATION The lowest temperature at which the distorted grain structure of a cold- worked metal is replaced by a new, strain-free grain structure during prolonged annealing. Time, purity of metal, and prior deformation are important factors.
- 15. After casting we achieve three intermediate shapes called blooms, billets, and slabs: Blooms have square cross section 6” x 6” or larger. They are rolled into structural shapes.
- 16. Billets have square cross section 1.5” x 1.5” or larger. they are rolled into bars and rods. Slabs have rectangular cross section 10” x 1.5” or larger. They are rolled into plates, sheets.
- 17. Advantages Of Hot Rolling The possibility of producing a very dramatic shape change in a single working step, without causing large amounts of internal stress, cracks or cold working; Sometimes hot working can be combined with a casting process so that metal is cast and then immediately hot worked. This saves money because we don't have to pay for the energy to reheat the metal.
- 18. Disadvantages Of Hot Rolling If the recrystallisation temperature of the worked metal is high e.g. if we are talking about steel, specialised methods are needed to protect the machines that work the metal. The working processes are also dangerous to human operators and very unpleasant to work near.
- 19. Cold Rolling If the temperature of the metal is below its recrystallization temperature, the process is termed as cold rolling
- 20. Advantages Of Cold Rolling A better surface finish may be achieved Dimensional accuracy can be excellent because the work is not hot so it doesn't shrink on cooling; also the low temperatures mean the tools such as dies and rollers can last a long time without wearing out.
- 21. Disadvantages Of Cold Rolling Higher forces are required to produce a given deformation, which means we need heavily built, strong forming machines .
- 22. Rolling Mills Two-high rolling mill: consists of two opposing rolls. These rolls may rotate only in one direction (non reversing) or in two directions (reversing). Three-high rolling mill: allows a series of reductions without the need to change the rotational direction of the rolls.
- 23. Rolling Mills Four-high rolling mill: Using small rolls reduces power consumption but increases the roll deflection. In this configuration, two small rolls, called working rolls, are used to reduce the power and another two, called backing rolls, are used to provide support to the working rolls. Cluster rolling mill: another configuration that allows smaller working rolls to be used.
- 24. Various Configuration Of Rolling Mills
- 25. What is difference b/w a tube & a pipe The difference between a pipe and a tube is how they are measured, and ultimately what they are used for. A pipe is a vessel - a tube is structural. A pipe is measured ID - a tube is measured OD.
- 26. Production Of Seamless Piping & Tubing Seamless Pipes:- . Seamless (SMLS) Steel Pipe is made from a solid round steel ‘billet’ which is heated and pushed or pulled over a form until the steel is shaped into a hollow tube. The seamless pipe is then finished to dimensional and wall thickness specifications in sizes from 1/8 inch to 26 inch O
- 28. Seamless Tubes:- The process involves the progressive bending of metal strip as it passes through a series of rollers at speed up to 80m/sec. Only bending take place, all bends are parallel. Seam welding process carried out to form a proper tube.and wed flashes are removed by scarfing blades.
- 29. Comparison Of Seamless Pipe & Tube Seamless Pipe Seamless Tube Seamless pipe Welded pipe often provides the most has tighter reliable pressure dimensional retaining tolerances. characteristics. cheaper if easily available than manufactured in the welded pipe. same quantities. More Expensive. Size is greater than Size is less than 3 3 inch dia. inch dia.