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Roll pass design in continuous bar mills

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R
rahul kishore

The document discusses various topics related to rolling mills and rolling processes. It defines a rolling mill as consisting of at least two cylindrical rolls used to shape or form metal. It describes different types of mill passes based on shape (definite, intermediate) and roll adjustment (open, closed). It provides formulas to calculate parameters for each pass like roll groove dimensions, roll gap, filled width, area reduction, and bite angle. It discusses concepts like number of passes required, spread calculation, and provides thumb rules and flow charts for roll pass design.

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African Foundries Ltd. Lagos, Nigeria Presented by Rahul Kishore
Basics of Rolling  A rolling mill consist of several, at least two rolls cylindrical or nearly cylindrical bodies which are termed as “roll” and which rest in bearings at their ends.  The normal and average center distance from the center of one roll to the center of other determine the size of mill. Thus 12 inch mill, the distance from center to center rolls is 12 inch.
Types of pass  According to shape wise Definite passes – those having two equal axes in an x, y plane (Squares, Rounds)
Types of pass Intermediate passes – those having one axis larger than the other one (Rectangles – box, Diamonds, Ovals)
Types of pass  According to adjustment of rolls Open passes – The joint between the two rolls is open or the opening of the pass lies in center.
Types of pass Closed passes – The projection of one roll fits into a groove of the other roll.
Pass Design and Groove Details  This calculation gives the following parameters for each pass. Roll groove dimensions. Roll gap. Filled width in pass. Filled area. Area reduction. Bite angle.
Number of passes required  No. of Passes= log of co-eff of elongation/log(1.29)
Thumb rules in rolls pass design Pass Groove angle Bottom angle Relief radius Bottom radius Box pass 8-10 deg 10 Diamond pass >90 deg 18 Square pass 45 deg Around 90 deg 5 Oval pass 60 deg 30 deg 5 Round pass 60 deg 60 deg 0.2 x Bottom radius 0.5 x dia
Geometrical relation in Rolling
Geometrical relation in Rolling • A1 x V1 = A2 x V2= A3 x V3…….=1 A1,A2,A3…….. Area of stand 1, stand 2, stand 3……. V1,V2,V3……..Velocity of stand 1, stand 2, stand 3……. • Shrinkage factor of steel (1.012 - 1.015)
Thumb rules in rolls pass design  Fittings from oval to round must be 0.3 to 0.7.  For ovals width to height ratio must be less than 3.0.
Spread  When the steel is compressed in the rolls it will obviously move in the direction of least resistance, so usually there is not only longitudinal flow but also some lateral flow. This is called ‘Spread”. it is generally accepted that beyond a ratio width/height = 5, spread becomes negligible.
Spread calculation in round
Spread calculation in Oval
Spread  The equivalent rectangular approximation into round oval pass to calculate effective height of the work piece and the area fraction of work piece and the geometry of groove.  H0 – Effective height of outgoing work piece.  Hi – Effective height of incoming work piece.  Hi – Height of incoming work piece.  Reff – Effective Radius of incoming work piece.  Wi – Width of incoming work piece.  Bc – Effective Width of work piece.
Spread  Then maximum spread of a work piece at exit Wmax was then calculated as.
Spread
Spread  Where y is constant and the value for different pass as following Pass y Square - Oval 0.92 Round - Oval 0.97 Square - Diamond 0.83 Oval - Square 1.06 Oval - Round 0.83 Diamond - Square 0.83 Diamond - Diamond 0.95 Oval - Oval 0.95 With original Shinokura procedure, following spread factors for roll pass design is suggested [1]:
Important Formula to Calculate arc  To calculate the radius Given an arc or segment with known width and height:  The formula for the radius is:
Important Formula to Calculate arc Where:-  W is the length of the chord defining the base of the arc .  H is the height measured at the midpoint of the arc's base.
Important Formula to Calculate arc Area
Important Formula to Calculate arc Area  where: C - is the central angle in DEGREES R - is the radius of the circle of which the segment is a part.
Flow Chart to Design Pass For Maximum Elongation
Important formula to calculate nominal Weight of bar Diameter x Diameter Weight = 162.163
Example • The Weight of 16 mm Re- Bar 16 x 16 =264 264/162.163 = 1.578 kg • The Weight of 25mm Re-Bar 25 x 25 = 625 625/162.163 = 3.854 kg
Important formula to calculate area  Where Ae = Effective cross-sectional area of bar L = Length of TMT W = Weight of TMT
Angle adjustment for twister guides
Thank You

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Roll pass design in continuous bar mills

  • 1. African Foundries Ltd. Lagos, Nigeria Presented by Rahul Kishore
  • 2. Basics of Rolling  A rolling mill consist of several, at least two rolls cylindrical or nearly cylindrical bodies which are termed as “roll” and which rest in bearings at their ends.  The normal and average center distance from the center of one roll to the center of other determine the size of mill. Thus 12 inch mill, the distance from center to center rolls is 12 inch.
  • 3. Types of pass  According to shape wise Definite passes – those having two equal axes in an x, y plane (Squares, Rounds)
  • 4. Types of pass Intermediate passes – those having one axis larger than the other one (Rectangles – box, Diamonds, Ovals)
  • 5. Types of pass  According to adjustment of rolls Open passes – The joint between the two rolls is open or the opening of the pass lies in center.
  • 6. Types of pass Closed passes – The projection of one roll fits into a groove of the other roll.
  • 7. Pass Design and Groove Details  This calculation gives the following parameters for each pass. Roll groove dimensions. Roll gap. Filled width in pass. Filled area. Area reduction. Bite angle.
  • 8. Number of passes required  No. of Passes= log of co-eff of elongation/log(1.29)
  • 9. Thumb rules in rolls pass design Pass Groove angle Bottom angle Relief radius Bottom radius Box pass 8-10 deg 10 Diamond pass >90 deg 18 Square pass 45 deg Around 90 deg 5 Oval pass 60 deg 30 deg 5 Round pass 60 deg 60 deg 0.2 x Bottom radius 0.5 x dia
  • 11. Geometrical relation in Rolling • A1 x V1 = A2 x V2= A3 x V3…….=1 A1,A2,A3…….. Area of stand 1, stand 2, stand 3……. V1,V2,V3……..Velocity of stand 1, stand 2, stand 3……. • Shrinkage factor of steel (1.012 - 1.015)
  • 12. Thumb rules in rolls pass design  Fittings from oval to round must be 0.3 to 0.7.  For ovals width to height ratio must be less than 3.0.
  • 13. Spread  When the steel is compressed in the rolls it will obviously move in the direction of least resistance, so usually there is not only longitudinal flow but also some lateral flow. This is called ‘Spread”. it is generally accepted that beyond a ratio width/height = 5, spread becomes negligible.
  • 16. Spread  The equivalent rectangular approximation into round oval pass to calculate effective height of the work piece and the area fraction of work piece and the geometry of groove.  H0 – Effective height of outgoing work piece.  Hi – Effective height of incoming work piece.  Hi – Height of incoming work piece.  Reff – Effective Radius of incoming work piece.  Wi – Width of incoming work piece.  Bc – Effective Width of work piece.
  • 17. Spread  Then maximum spread of a work piece at exit Wmax was then calculated as.
  • 19. Spread  Where y is constant and the value for different pass as following Pass y Square - Oval 0.92 Round - Oval 0.97 Square - Diamond 0.83 Oval - Square 1.06 Oval - Round 0.83 Diamond - Square 0.83 Diamond - Diamond 0.95 Oval - Oval 0.95 With original Shinokura procedure, following spread factors for roll pass design is suggested [1]:
  • 20. Important Formula to Calculate arc  To calculate the radius Given an arc or segment with known width and height:  The formula for the radius is:
  • 21. Important Formula to Calculate arc Where:-  W is the length of the chord defining the base of the arc .  H is the height measured at the midpoint of the arc's base.
  • 22. Important Formula to Calculate arc Area
  • 23. Important Formula to Calculate arc Area  where: C - is the central angle in DEGREES R - is the radius of the circle of which the segment is a part.
  • 24. Flow Chart to Design Pass For Maximum Elongation
  • 25. Important formula to calculate nominal Weight of bar Diameter x Diameter Weight = 162.163
  • 26. Example • The Weight of 16 mm Re- Bar 16 x 16 =264 264/162.163 = 1.578 kg • The Weight of 25mm Re-Bar 25 x 25 = 625 625/162.163 = 3.854 kg
  • 27. Important formula to calculate area  Where Ae = Effective cross-sectional area of bar L = Length of TMT W = Weight of TMT
  • 28. Angle adjustment for twister guides