Innovation Spuzic

1

University of South Australia

Roll Pass Design based on Knowledge Discovery from Rolling Mill Records

by Dr Sead Spuzic

School of Engineering

2

Keywords

• roll pass design (RPD)

• statistical analysis

• roll life

• generic function

• optimisation

• productivity

• savings

• Contemporary trends are characterised by the increasing demands on:

• Mechanical and metallurgical attributes

• Improved morphometric tolerances

• Increased flexibility in the manufacturing operations

• Higher productivity

• Improved sustainability

• The complexity of the applied RPD depends on the level of expectations:

• Enable energy effective schedules• Duration effective schedules• More exact morphometry• Thermo-mechanical processing of the final

microstructure

• Roll grooves can be designed in a variety of ways

at the same cost, but with significant economic consequences for both the maintenance and the operations

• RPD needs to take into account the kinetics of the groove meridians (i.e. the gradual change of the groove shape due to roll wear)

Rolls are expensive tools

Roll wear, one of the principal factors, cannot be understood

and controlled unless we understand effects of parameters

that can be really measured

9

• Gradual wear of grooves leads to an increasing frequency of adjustments along the rolling line (i.e. the production delays). Ultimately, the rolls are replaced.

• As the process continues the grooves wear unevenly

and this causes the changes in pressure and metal flow

distribution

• Ultimately, the process

has to be interrupted

because the product

is out of the tolerances

10

• A prerequisite for understanding RPD logics is to

intelligently translate the process parameters into

mathematical forms.

• A key for rolling process optimisation must be

sought in roll pass design (RPD), a principal

factor that delimits process efficiency, product

quality and resource consumption.

Translation of records into Data

• Identifying effective method to translate the RPD records into the matrix format

• Finding effective method to incorporate maintenance and production KPI’s into the matrix format

Final step is a reverse translation into RPD parameters

• Identify the characteristic trends and anticipated boundaries

• Non-leaner optimisation will be used to identify the optimum values for each parameter

F Y( )1

σY 2π..

Yc

2µY.Yc

YexpYcµY

2

2σY2.

d.

z Y( ) e

YµY2

2σY2.

13

An introductory example of generic function

a, b, c, d, and e, are RPD parameters.

With regard to the pass geometry, a number of additional parameters are needed.

14

An introductory example of generic function

15

An introductory example of generic function

a = 6.8

b = 0.05626

c = -0.99264

d = 0.08189

e = 0.00792; f = 0.326; g = 9.823; p = 2; ∆y < 0.03 mm

16

An introductory example of application

17

An introductory example of application

Let us consider a situation when a mill produces a series of square sections (e.g. from square 10 mm to

square 30 mm)

Frequently, one or several members are difficult to control or otherwise show a poor performance.

18

An introductory example of application

Then it is rational to analyse whether some of the parameters deviate from trends shown by the whole assortment. The parameters corresponding to the square 16 mm do not fit well with the trend lines corresponding to the complete series.

Methodology

20

Conclusions

• Reductions in the natural resource consumption require technological changes in the large-scale industrial processes. This prompts for application of knowledge extraction in hot steel rolling mills.

• Industrial and scholarly accumulated databases can be analysed statistically to extract useful RPD models.

• Roll pass design can be improved by finding the patterns in data sets accumulated by the product and tool users and manufacturers.

21

Conclusions

• Pilot tests confirm that generic functions can be used to enhance analysis of a broad spectrum of pass geometries.

• The Hybrid RPD can be used

•to calibrate promising trials at the commencement of new mills and products,

•to optimise the existing schedules,

•to define the emergency RPD routes,

•for urgent modifications to compensate for system disturbances, etc.

22

Benefits

• rolling process will become more stable (more reliable); adjustments will become less frequent and faster,

• overall life of tools (rolls) will increase, the depth of necessary redressing of rolls will decrease,

• resource consumption will decrease due to less interruptions to the overall process,

• productivity, yield and reliability will increase,

• production costs will decrease,

• sustainability of the overall process will improve.

23

Benefits

• The life of the rolls will increase. Depending on the mill, the costs for the set of rolls range in the order of 103 to 105 AUD.

• Total count of production delays and their individual durations will be reduced. Any stoppage in a rolling mill process typically costs between AUD 10,000 and 30,000 per hour, depending on the mill type. It is important to keep in mind that these delays recur since mills operate continuously in shifts.

24

Benefits

• The productivity will increase. This can be translated in dollar amount only when the performance and costs particulars about the observed mill are included. Any improvement in productivity impacts directly on decrease in costs. These savings are accumulative.

• The amount of consumables (energy, water, fuel, etc.) needed for production and maintenance will decrease.

Better control of campaigns allows for further summative savings.

• The investments for the improvement in existing RPD are

low – groove changes are routinely made in mill practice.

Thank you