VIII

Process Modeling - Empirical

No

Name

Description

Client / Employer

63

Morgan?s roll force calculation procedure examination to identify weakness

Requested by Morgan?s top management to examine the force prediction procedure. Attention was also focused to examine the algorithm and material data used for Morgan?s roll pass program CAPE. It was found that the procedures used at the time was only valid for the strain rate below 100/s, while the actual rolling process had a strain rate up to 3000/s.

Morgan

64

Analysis of Morgan?s lab mill data acquired from five-year rolling tests

Data was collected in a five-year lab mill test, during which about 1000 samples were rolled. For each rolled piece, over 70 parameters, including free radius, cross section area, forward slip, etc. were measured or calculated. It was one of the primary data sources to develop rolling process models. However, due to certain weaknesses in the experiment design and limited understanding of rolling process, the prior engineers who designed the tests had difficulty deriving meaningful models from such large-scale rolling tests. In the new work the missing parts were added from other data sources (e.g., those from 15-year rolling tests from the institute in Germany, in a four-stand high-speed continuous mill), to make the data fully useful.

Morgan

65

Development of spread model, particularly for high speed rolling

The existing Shinokura formula used in Morgan?s computer aided design was expanded to add more influence factors. Various spread prediction procedure, such as Hensel, Wusatowski, etc. were studied and verified/modified based on the large amount of experiment data. Spread procedures were later also verified by the field data collected from the No-Twist mills (e.g. ASW mill), etc.

Morgan

66

Development of accurate flow stress models for both low and high speed mills

Traditional flow stress models were verified and improved with the flow stress data I collected worldwide, and with mill results and especially field data. To fit high speed mill, traditional models (valid up to the strain rate 100/s) were extended to including the temperature/strain rate interactive factor to allow it to be valid up to the strain rate 500/s and can be roughly used for the high-speed rolling up to the strain rate 3000/s (100m/s). This is the nearest approach to the highest rolling. Neither formula is available nor the flow stress measurable in the range of 3000/s with constant strain rate values. Flow stress models for major grade groups and key grades were determined based on the new formula.

Morgan

67

Development of empirical models for spread estimation, for RD-OV and OV-RD passes

This was the direct modeling of the spread based on Morgan?s lab mill data. Model can be used for the first assessment of the roll pass because it does not need so much geometry calculation as Shinokura formula does. Some colleagues did roll pass design with ΔB = k ΔH to estimate width spread from a height reduction, with k ~ 0.33 for OV-RD and k ~ 0.6 for RD-OV. Therefore, I developed a simple formula to determine value of the k by considering several key parameters.

Morgan

68

Development on steel rolling mill force model, with study on mean flow stress, contact area and shape factor.

Roll separating force during rolling actually depends on three primary factors: the mean flow stress, the projective contact area and the shape factor. Mean flow stress depends on material only (including deformation history), and the shape factor is affected by the strain state and stress state in the deformation zone. Accurate prediction of the rolling force requires that all those three factors be accurately modeled, which was one of my primary areas of the rolling process modeling. I also studied various force prediction procedures for flat rolling, which lead to only different shape factor formulas.

Morgan

69

Development of contact area prediction model, particularly for the shape rolling, for accurate force prediction

The shapes of the contact areas for various rolling processes are complicated and are different in various pass sequence. Mathematical description of the actual shape and the projective contact area is critical for accurate force prediction. Contact area models for various pass sequences, such as RD-OV, OV-RD, SQ-OV, OV-SQ, etc., were developed with the formulation of the actual shapes.

Morgan

70

Development of shape factor prediction model for accurate force prediction

Actual modeling for the shape factor needs to consider friction condition and groove geometry. My modeling for the shape factor started from an universal formula that covers all the pass sequences, created by some German colleagues based on the tens years of measurement and modeling. With rich experience results and mill field data at hand, I did verification, modification and simplification, so I established accurate models for RD-OV, OV-RD, RD-RD (For Morgan Sizing Mills), SQ-OV, OV-SQ, etc. The models fit both the low speed rolling and high speed rolling.

71

Development of forward slip models for RD-OV and OV-RD, for both low-speed and high-speed rolling

Neutral angle models for RD-OV and OV-RD were established based on the lab mill data and followed by necessary modification. On the basis, the forward slips were calculated with Wusatowski procedure. Predicted result fits excellently with the field measurement from ASW NTM, etc.

Morgan

72

Rolling mill friction model development to improve Morgan?s design procedure

The model considers factors such as type of groove, temperature, speed, steel grade, etc. As effects of temperature and steel grade, the metallurgical constituent of the scale and its property were also studied.

Morgan

73

Development of accurate temperature prediction model and models for heat transfer coefficients

The model is based on the energy balance between the stock and rolls. Heat transfer coefficients were based on the past measurement in various researches. Thermal properties were all in temperature dependence.

Morgan

74

ASW NTM data processing and Model verification

Processed ASW data pass by pass; used the models I had developed to re-predict the measured data and so, to verify and improve the developed models.

Morgan

75

Development of the microstructure model for steel hot rolling processes to predict recrystallization, grain size, etc.

The model was developed by combining the major models (both formulas and data) published worldwide. Quite a portion of my $10,000 research funds was spent for acquiring publications. The model consists of the sub-models to determine: (1) strain or time, for start and 50% completion of the dynamic and static recrystallizations; each of those may consist of two or more ways of prediction; (2) volume fractions of, and grain sizes after, the dynamical and static recrystallizations; and (3) grain growth, equivalent grain sizes at the start and end of a pass, and the equivalent inter-pass time under temperature modification. Over 10 formulas and overt 30 coefficients were used to describe the model of a steel grade. Microstructural models for over 10 steel grades were collected. Models were examined with data collected from publications.

Morgan

76

Development of tension correction model to modify spread, forward slip and roll force

Tension correction to spread and forward slip is critical for roll pass study of existing No-Twist Mill (NTM) because all stands are tied (driven by a single motor) and it is very hard to avoid tension. Without this correction, any field data from the NTM would not lead to any meaningful model. In the development, German results were accepted but Japanese formula (definition of tension and tension correction formulas) were used. However, Japanese results, which were based on products of larger size, didn?t fit the NTM data and thus were filtered out.

Morgan

77

Development on interstand tension determination

The development involved the definition of tension. Many German results on tension effects were based on the definition of tension as the relative difference of the speed. The actual tension, calculated from the specially modified flow stress model was used (even the best flow stress formula available still doesn?t work for a small strain below 0.05).

Morgan

78

Modeling of the free-contours of the stock after rolling

The free contour was modeled based on the measurement in Morgan?s lab mill data. This model was used for accurate calculation of the rolled cross-section area.

Morgan

79

Flow Stress Modeling Program to create flow stress models based on the data in the flow stress database

The program accesses database to read in the flow stresses in various strains, strain rates and temperatures, and calculates flow stress coefficients for temperature, strain and strain rate. The calculation was based on various criteria. See www.meta4-0.com/bli/L2Net/FSModel.htm. The program determines factors m1 to m5 and A1 to A3, and Kf0, through both linear and non-linear regression. It also allow user to select special needs for modeling, such as min-mid-max, best peak strain, best R-square, etc.

Metal Data

80

Extensive data collection on mill test results from reports, publications, etc.; data storage in database

Mill test results on rolling and controlled cooling, collected in past years as published or unpublished reports, published papers, books, Ph.D. dissertations, etc., were processed and stored in the relational database. Great portions of the data were roll pass related measurement, force measurement, controlled cooling data, rolled product properties and a portion of the microstructure data. Further data would be added into the database.

Metal Data

81

Collection of flow stress data for about 2000 steel grades

Flow stress data and models were collected from various available sources. Currently about 2000 models are available on the web. Other data, another 2000 sets, et., would soon be processed and uploaded.

Metal Data

82

A Coordinate Measuring Tool to read data from curves (e.g. flow stress curves)

This application was initially developed to measure flow stress from flow stress curves. The scanned picture with the curves is to be measured for coordinate. Mouse clicking is made against the points on the existing curve to draw another curve, in order to make sure the clicking is not off the line. For every click, the coordinate is recorded. The coordinate is immediate calculated into the physical value based on an initial setup against the coordinate system in the picture. The value from every click is displayed on the form for double-checking. When the Submit button is clicked, the data is sent to the database.

Metal Data

83

Compilation of data list for the metal properties (about 3000)

Compiled data list for the metal properties. Particular focus was on high temperature properties while room temperature properties were also collected.

Metal Data

84

Development of heat transfer coefficient models for rolling, controlled water cooling and controlled air cooling

For interface between rolls and hot metals during rolling, for steel cooling in the air in the function of the travel speed and environment temperature, and for the controlled water cooling depending on water flow volume, water pressure, water temperature and turbulence, etc. For example, for the water box cooling alone, several hundred pages of the field-testing reports were used. High quality models were derived from the rich mill data.

Metal Data

85

Development of spread model for various steel grades during various type of rolling

Some stainless steel may have twice as high as spread as the plain carbon steels, while other stainless steels may have low spread. Different metals have different spread tendency.

Metal Data

86

Development of forward slip model for various steel grades during various types of rolling

This part of the model focused on the steel grade influence on the forward slip. It was the further development based on the unpublished writing of Dr. A. Hensel. Data for over 30 steel grades were developed. Not to be published but is available in the further mill projects.

Metal Data

87

Friction model further development - to create a one-for-all friction model for steel rolling

Different materials have different friction values; for the same pair of the materials, friction depends on surface condition (roughness, amount and type of the lubricants, etc.), groove type, speed, and temperature. Temperature has different effects to friction in different temperature range. Formulas were collected and further developed with available new data.

Metal Data

88

Publishing a book on the computer simulation of steel hot rolling process (Germany 1996)

Compared Experimental and Theoretical Investigations of Forming Technical Parameters in Shape Rolling with Example of the Hot Rolling of Angle Steels. TU Bergakademie Freiberg, Freiberg, Germany, 1996 (in German). ISBN 3-86012-029-8.

89

Wrote a book - Steel Mill: Process Modeling and Computer Application

Broad topics, with fundamentals, technologies and industrial project examples. The book is not yet intended for publishing. Contents may be available for clients or work colleagues. See www.meta4-0.com/bli/home/book2.htm (under updating).

Metal Data

90

Rolling mill resource collection and processing

Collected rolling mill modeling resources for over 20,000 pages; processed over 10,000 pages of the resources

Metal Data