"METALTEHNOMASH" Metallurgical technology for mechanical engineering

Defects on the strips surface (stickers, spots of adhesion, scratches and marks), as well as loss of stability of coil (slippage under its own weight or the formation of a defect "coil bore collapse") are associated with irrational stress-strain state of coils when they were wound.

In this relation it is an important task of improving and developing new methods and computer system for calculating the SSS of coils, allowing:

predicting the SSS of coils during and after winding in cold rolling mill, as well as during coils annealing;
determining the optimum conditions of winding and annealing in bell furnaces with minimal probability of turns welding during coils annealing or slippage of coils in the subsequent unwinding in the process of tempering.

Creation of effective methods providing optimal stress state of coils during strips rolling and winding on the mill 2030

Period: 2001-2002
Customer: JSC NLMK

The aim of the work is to develop new elements of the technology of strips cold rolling and winding in coils, taking into account the patterns of winding temperature changes, and ensuring the quality of the strips surface.

Additional information

THE MAIN SECTIONS OF WORK:

1. DEVELOPMENT AND SOFTWARE IMPLEMENTATION ON PC OF BASIC NON-ISOTHERMAL MODEL AND ALGORITHM FOR CALCULATING THE TEMPERATURE FIELD AND STRESS-STRAIN STATE OF THE DENSELY WOUND COIL DURING WINDING, AFTER REMOVAL FROM THE DRUM WINDER, DURING COOLING AS WELL AS HEATING AND COOLING IN THE BELL-TYPE FURNACES
1.1 Elements of the mathematical formulation of the problem
1.1.1 Thermal problem
1.1.2 Determination of the stress-state of coil
1.2 An algorithm for solving the problem

2. MECHANISM OF THE INFLUENCE OF ROUGH SURFACE CONDITIONS OF COLD-ROLLED STRIP TURNS STICKING IN COILS DURING ANNEALING AND SURFACE DEFECTS FORMATION
2.1 Results of the specific problems solution
2.1.1 Inter-turns pressure in the isothermal coil
2.2 Analysis of simulation results

3. ANALYSIS OF LABORATORY AND PILOT EXPERIMENTAL STUDIES. FORMALIZATION OF CRITERIA (CONDITIONS) OF GRIP, ADHESION, WELDING

4. EXPERIMENTAL STUDY OF TEMPERATURE INFLUENCE OF STRIPS WINDING IN THE COILS IN COLD ROLLING ON THE FORMATION OF STRIP SURFACE DEFECTS

5.STUDY THE EFFECT OF STRIP WINDING AND ANNEALING CONDITIONS ON COILS TURNS ADHESION-WELDING. DEVELOPMENT AND NUMERICAL EVALUATION OF NEW TECHNICAL SOLUTIONS
5.1 Effect of extended controlled cooling under the bell in bell-type furnaces
5.2 Effect of temperature over the radius of coil and determining the optimal distribution law
5.3 Effect of the variation of the strip tension at the initial stage of the coil winding. Development of a rational law of tension variation
5.4 Effects of places of speed ramps along the coil radius on the inter-turn pressure and a tendency to turns welding during annealing
5.5 Effect of length of the strip, rolled at low speed, and location of braking and acceleration places of the mill along the length of the strip (the radius of the roll)
5.6 Effect of weld passing speed
5.7 Effect of strip width

6. DEVELOPMENT OF NEW ELEMENTS OF TECHNOLOGY

APPENDIX. The program package "Coil Temper" on CD-ROM

Thermo-graphic images of the temperature distribution along the length of strip wound in coils in accordance with speed diagrams of rolling and winding

Designed mode of strips rolling and winding, allowing
reducing inter-turn pressure in the coil
Graphs below of inter-turn pressures by the coil radius

Modeling and development of coils annealing conditions
Mode of recrystallization annealing in bell-type furnace: the temperature of shielding gas Tgas, temperature of the first T (N = 1) and the last T (N = Ne) strip turn in the coil and the temperature of the strip in the median turn along the radius of coil T (N = Nmidl)

Temperature field in a coil

stage of heating

stage of cooling

Development of new efficient technology of creating the optimal bulk stress state of coils during rolling, strips winding in mill 2030 and during the bell annealing, taking into account data on the distribution of temperature and flatness by the length and width of the strips

Period: 2003 - 2004
Customer: JSC NLMK

The aim of the work is to improve the technology of cold rolling, winding in coils, annealing, and strips tempering based on the data of temperature and flatness distribution by the length and width of strips, ensuring quality of the strips surface.

Additional information

THE MAIN SECTIONS OF WORK:

1. CREATING A MODEL OF THE TEMPERATURE AND BULK STRESS-STRAIN STATE OF STRIP IN COIL DURING WINDING, AFTER REMOVAL FROM THE DRUM WINDER, CHANGING THE TEMPERATURE FIELD IN A COIL
1.1 Accounting the changes in the parameters and conditions of strip winding by the strip length and width
1.2 Testing the spatial problem
1.3 Effect of profile changes accumulation of the coils outer line during winding
1.4 Spatial effects in the formalization of the conditions of separation in the outer
1.5 Conditions of segments sliding of the drum winder during coil winding and their influence on the stress-strain state of the coil
1.6 Improving the computer system "Coil Temper"
1.6.1 Accounting for the actual strip flatness

2. DETERMINATION OF THERMAL CONTACT INTERACTIONS IN BELL-TYPE FURNACES OF COILS STACK AND PROTECTIVE GAS AT ITS CIRCULATION
2.1 Equations for determining the conditions of thermal contact interaction of coil and protective gas in bell-type furnace
2.1.1 Calculation of the temperature of the protective gas during the annealing of the coils stack in a bell-type furnace
2.2 Equations for estimating the temperature of combustion products and the protective gas in the gap between the surface of the muffle and coils stack
2.3 Approximated analytical solutions of the equations
2.4 An algorithm for solving the complete problem of determining the temperature of the protective gas using the finite analytical relations
2.5 Calculation of the coils temperature change, taking into account heat transfer by radiation from the muffle
2.6 Qualitative analysis of the effect of protective gas composition on its temperature change

3. TYPES AND CONDITIONS OF COILS LOSS OF STABILITY
3.1 Determination of conditions of stability loss of internal turns of coils and formation of defect "bird"
3.2 Definition of terms "sinking" after removal from the drum winder and during cooling under its own weight

4. NEW ELEMENTS OF TECHNOLOGY AND PILOT TESTING
4.1 The effect of the convexity of the transverse profile of the strip and the associated changes in the outer coil profile during winding on a bulk stress state of coil
4.2 Efficient configuration of the support surface of the convection ring
4.3 Possibilities of implementing of power saving mode of annealing on the stage of coils cooling in bell-type furnace due to the intensification of the heating stage
4.4 The optimal ratio between the relative local thickening of the transverse profile on the hot-rolled strip and in the finished cold-rolled strip
4.4.1 Quantitative evaluation of the rational degree of reduction of the relative values of the local thickening
4.4.2 Evaluation of the longitudinal residual stresses
4.4.3 Conditions for the formation of local flatness variation. The critical compressive residual stresses. Loss of stability.
4.5 Defining the conditions of axial withdrawal of turns, depending on the strip wedge
4.6 Determination of areas of relative slippage and scratching of turns along the length of the strips
4.7 A new method of rolled strip production in coils and its experimental-industrial testing
4.8 Experimental and industrial testing

5. RECOMMENDATIONS AND DRAFT AMENDMENTS TO TECHNOLOGICAL INSTRUCTION

The calculated inter-turn pressure during recrystallization annealing (strip width 1200 mm, thickness 0.5 mm)

stage of (at time 35, 36, 37, 38, 39, 40, 41, 42, 43 hours)

stage of cooling (at times 57,58,59,60,61,62,63,64,65 hours)

Analysis of information on the transverse profile of hot-rolled strip
Computer system interface HRSProfileAnalisys, in which the assessment fulfilled of cross-section profile of hot-rolled strip in the light of its transformation in the stands of cold mill:

Experimental confirmation of the formation of strip surface defects
in the places specified in the numerical analysis
(coil unwinding on temper mill)

Calculations of the temperature of the turns layer in the stack of coils
(15 h from the start of recrystallization annealing)

The calculated inter-turn pressure in the coil on the heating stage and the stress contours
by the thickness of the winding coil (15 h after annealing)

The main results:

Increase by 1.5-2.0% of rolled strip output of I group of surface quiality;
Increase productivity by 7% in mill 2030 during rolling strips of thicknesses 0.5 - 0.6 mm;
Reduction by 25% rejection rate by defect of cold rolled strips "stickers".

Performed a complex of works to improve the strip surface state, served as a basis of innovative solutions to the problem described in в scientific papers and thesis.