Hot Mill Research Articles

The Work Roll Bending Control System of the Hot Plate Rolling Mill

This article describes the kinds of thickness deviation arising during hot plate rolling process. The ways to determine thickness deviation by measuring the thickness of the sheet at various points are shown. The reasons of rolls bending under the rolling pressure are found. Examples of using the different structures for the implementation of the roll bending system are shown. The results of the system were considered in the hot rolling plate mill conditions.

Использование системы осевой сдвижки валков для корректировки межвалкового зазора на толстолистовых станах горячей прокатки

The factors are revealed affecting the thickness deviation of the sheet in the hot rolling process. CVC-roll description was shown, their distinct features and advantages for formation of the final shape of the plate. Known CVC-systems on the modern plate hot mills were considered. The main parameters of the work-roll crown were characterized by math formulas, the optimal shape of the rolls and they advantages to get a required flatness of the final plate was shown. The distribution of the roll gap along the length of the roll body was shown according to the horizontal displacement of the work rolls. The ways to eliminate of the most common thickness defects were shown. The most required directions of research were designated.

Technology and equipment modernization of rolling process on wide-strip mill of the first generation

The existing technologies of hot strip production in the mills of different generations are considered in the article on the basis of literary analysis, the major disadvantages are identified and development trends of wide-strip hot mills are determined. The outmoded and physically worn-out equipment is used in continuous wide-strip mills 1700 of Illich Iron and Steel Works in of Mariupol. To prolong the life of the equipment and the maintenance of competitiveness requires the equipment reconstruction and improving the technology of hot rolling of wide strips. The practical recommendations to improve the technology and mechanical equipment for the production of hot-rolled wide strips in condition of WSHM 1700 of Illich Iron and Steel Works in of Mariupol are proposed in the article. The proposed solutions will address the following actual tasks: the expansion of the product assortment, improving its quality with resource-saving and material-saving and, consequently, effectiveness increase of specific industrial enterprises.

The Effects of Cooling Mode on Precipitation and Mechanical Properties of a Ti-Nb Microalloyed Steel

Laboratory experiments of a high-strength Ti-Nb microalloyed steel were conducted with two cooling modes, i.e., a large (35 °C s−1) cooling rate in the initial stage followed by slow (8.5 °C s−1) cooling rate (termed as FFC) and a slow (8.5 °C s−1) cooling rate in the initial stage followed by large (35 °C s−1) cooling rate (LFC) during cooling process. Based on the results of laboratory experiments, an industrial trial was performed with similar steel on a continuous hot strip production mill. The grain size in LFC sample (2.83 μm) is smaller than that in FFC sample (3.80 μm), and the volume fraction of precipitates in LFC sample (1.04%) is more than that in FFC sample (0.81%). Both results of laboratory experiments and industrial tests confirm that the strengthening effect of the LFC mode is much better than that of the FFC mode from the viewpoints of both fine-grain strengthening and precipitation strengthening. The present study provides a new approach to improve the property of microalloyed steels produced by continuous hot rolling technology.

Flux-cored wires for surfacing of steel hot mill rolls

Flux-cored wires for surfacing of steel hot mill rolls

Fuzzy Adaptive Direct Generalized Predictive Control Algorithm in the Application of AWC Control

Using the characteristics of prediction model, rolling optimization and feedback correction, a AWC system based on generalized predictive control was designed, and its control performance was simulated based on a hot strip continuous mill. The results show that generalized predictive controller achieves better control effects than the normal PID on response time and steady precision with matching model; when model mismatching is caused by inaccuracy of plastic coefficient and pure delay time, the normal PID is overshot or even oscillation, but the control performance of the generalized predictive controller is not influenced by model parameter variations .

Effect of Diffusion Annealing on Defects Reduction of 6.5wt% High Silicon Steel Composite Plate after Hot Deformation

6.5wt% high silicon electrical sheet is hard to be obtained through conventional different rolling processes due to its remarkable brittleness at room temperature and appearance of ordered phases in the alloy substrates, especially it has very excellent soft magnetic properties. In this study, 6.5wt%Si three-layer composite panels were prepared by advanced technology of laminar composite. The defects, bonding strength, and distribution of elements of the coating and core layers are analyzed by the photographs of metallographic phase and SEM. Experimental results show that the high silicon composite plate could carry out lager plastic deformation on the traditional hot mill after the inner layer which is10%Si ferrosilicon alloy was coated. The defects generated during hot deformation were reduced and uniform distribution of elements were achieved through proper diffusion annealing process. This article provides a short process method to produce 0.3-0.5mm 6.5wt%Si thin sheet.

Integration of Adaptive Neuro Fuzzy Inference Systems and principal component analysis for the control of tertiary scale formation on tinplate at a hot mill

Scale is highly detrimental to surface quality for tinplate products. There are a large number of process variables at a typical hot mill and principal component analysis is a well-known technique for reducing the number of process variables. This paper estimates the principal components associated with the hot mill process variables and puts these through an Adaptive Neuro Fuzzy Inference System (ANFIS) to find those hot mill running conditions that will minimise the amount of scale observed on the bottom of the rolled strip. It was found that the variation observed in all the hot mill process variables could be captured through the use of just six principal components, and that using just three of these in an ANFIS was sufficient to identify those operating conditions leading to coils being produced with a consistently low scale count. Specifically, it was found that the best operating conditions for the hot mill were when the first component was lower than −0.098 the second lower than 0.8058 and the third higher than −0.482. These ranges in turn corresponded to certain hot mill temperatures that depended to some extent on the base chemistry of the incoming slab.

Explicit Indirect Predictive Control Algorithm in the Application of AWC Control

Using the characteristics of prediction model, rolling optimization and feedback correction, a AWC system based on explicit indirect predictive control was designed, and its control performance was simulated based on a hot strip continuous mill. The results show that explicit indirect predictive control achieves better control effects than the normal PID on response time and steady precision with matching model; when model mismatching is caused by inaccuracy of plastic coefficient and pure delay time, the normal PID is overshot or even oscillation, but the control performance of the explicit indirect predictive control is not influenced by model parameter variations [1].

Optimization of Model Adaption Based on Multi-Samples in Hot Strip Mill

In order to improve the thickness precision, the model adaption method is of great concern which is a necessary component in the thickness control system. The sample concept is first taken into the model adaption in hot tandem mill, from which the learning coefficients are updated by a series of samples. Comparing to the single sample in traditional method, the new method can consider the variance in the length direction. And the source data is more comprehensive, the robustness is increased with flexible proportion coefficients. The thickness precision in stable production process is enhanced to 35μm. On-line result shows practical value and on-line application prospect.

Fabrication of 6.5wt%Si Composite Plate by Coat Casting and Hot Deformation Processes

The high silicon electrical steel composite plate, which contains Q235 low carbon steel and 10%Si ferrosilicon alloy, is fabricated by coat casting and hot rolling. The bonding strength, microstructure and distribution of elements of the coating and core layers are analysed by the photographs of metallographic phase and EDS. Experimental results show that the high silicon composite plate could carry out lager plastic deformation by conventional hot mill after the 10%Si ferrosilicon alloy coated by Q235 low carbon steel in the vacuum induction furnace. The uniform distribution of elements could be achieved through the diffusion annealing process after the stage of hot rolling processing. This study provides a referable method to produce the 6.5wt% high silicon electrical steel plates.

熱間圧延における高生産性圧延技術の開発

熱間圧延における高生産性圧延技術の開発

Design and Development of Coupling for Unequal Torque System

The problems occurs at the steel industries, as the overall subject of this paper is the frequent failure of output shaft of gear motor at the pay-off reel and design and development of new type of coupling which will operates according to the situation of the nature of the rotation of pay-off reel rotation and the nature of the rotation of the 4HI cold rolling mill and which will perform efficient working under maximum torque condition without fail. As the mechanism used in the coupling is a ratchet pawl mechanism which work is to provide only one directional rotation and restrict the other. Also the use of spring loaded inserts to, which when reverse motion required, mechanism to engage the coupling hence the newly designed coupling is best suitable as per the nature of the rotation of the pay-off and 4HI cold rolling mill. Keywords: Pay-off reel, 4HI cold rolling mill, Gear motor, Coupling, Ratchet and pawl mechanism. I. Introduction The gear motor is used in cold rolling mill to give motion to the Pay-off reel which is movable with automatic guide table also un-wrapping the coil and the beginning of the process. Pay-off is the standby unit to reduce feeding time of the coil to the cold rolling mill. A cold rolling mill, also known as a reduction mill or mill, has a common construction independent of the specific type of rolling being performed. Cold rolling occurs with the metal below its recrystallization temperature (usually at room temperature), which increases the strength via strain hardening up to 20%. It also improves the surface finish and holds tighter tolerances. Commonly cold- rolled products include sheets, strips, bars, and rods, these products are usually smaller than the same products that are hot rolled. Because of the smaller size of the work pieces and their greater strength, as compared to hot rolled stock, four-high or cluster mills are used. Cold rolling cannot reduce the thickness of a work piece as much as hot rolling in a single pass. Cold-rolled sheets and strips come in various conditions: full-hard, half-hard, quarter-hard, and skin-rolled. Full-hard rolling reduces the thickness by 50%, while the others involve less of a reduction. Skin-rolling, also known as a skin-pass, involves the least amount of reduction: 0.5-1%. It is used to produce a smooth surface, a uniform thickness, and reduce the yield point phenomenon. It is also used to break up the spangles in galvanized steel. Skin-rolled stock is usually used in subsequent cold-working processes where good ductility is required. Other shapes can be cold-rolled if the cross-section is relatively uniform and the transverse dimension is relatively small. Cold rolling shapes requires a series of shaping operations, usually along the lines of sizing, breakdown, roughing, semi-roughing, semi-finishing, and finishing. If processed by a blacksmith, the smoother, more consistent, and lower levels of carbon encapsulated in the steel makes it easier to process, but at the cost of being more expensive. II. Force analysis of shaft of gear motor The shaft of gear motor goes failure at the weakest section due to overloading, a tangential load act by the metal sheet i.e. torque of cold rolling mill that comes over the Pay-off reel up to 30000 Nm, self-torque 1281 Nm, and bending loading. Also it was found that casing of gear motor goes failure, i.e. it broke. The Gear motor is of 5.5KW and 41 rpm and that of Cold rolling mill driving motor is of 1000KW and initial rpm of motor is 200mpm i.e. meter per minute. The shaft of gear motor goes failure in duration of 1-2 months and each motor cost up to 60,000 Indian rupees. Due to periodic failure of gear motor, company changed the gear motor with separate gear box and motor. One of the reasons of failure is lack of concentration of worker while working. In Continuous process industry many types of roll are used for various applications; however process rolls used are classified in to two as working & conveying. Working rolls are used for changing the product being process. This included cold rolling mill, hot rolling mill rolls used for reduction of sheet thickness & shape. Printing press rolls used for transferring pattern to product. Corrugation rolls used for changing the profile of sheet. Conveying rolls are mainly having application of transferring product from one place to other. This type rolls are smaller diameter and are generally non driven to large diameter used for transferring sheets, paper, and textile products in continuous process industry. The gear motor is used in pay-off reel to wound the metal coil, that motor is connected with Pinch roll of pay-off reel by claw coupling. One lever provided for

Разработка регулятора толщины мехатронной системы управления формой раската в плане при профилированной прокатке на толстолистовом стане

The thickness control, as a part of plan view pattern control mechatronics system, with variable coefficients depending on the stand springing is offered in this article. The experimental stress-strain curves of the stand are given. Compensator methods of influence of various external factors on the system setting accuracy are considered. Approbation results of introduced regulator on the hot plate mill 5000.

Study on Forward Slip Model for Aluminum Hot Tandem Rolling

Forward slip is an important parameter in the schedule of aluminum hot finish mill. Its precision directly affects the mass flow of the strip through the stands, the pre-set roll speed and the adjustment time of the tension. In this paper, a practical forward slip model is established based on the analysis of reduction, output thickness, work roll radius, friction coefficient and strip temperature. The result is obtained by the least-squares regression. All these are based on a large number of field data which come from 1+4 aluminum hot rolling mill in Henan.

Reducing production loss by prolonging service life of rolling mill shear pin with ultrasonic nanocrystal surface modification technology

Premature failure at the shear pin of stainless hot rolling mill caused by increasing productivity and fluctuation of roll torque raises significant downtime cost. To reduce downtime cost, UNSM (Ultrasonic Nanocrystal Surface Modification) treatment is applied to the neck groove of shear pin as the alternative to existing solutions. This treatment prevents premature failure, increases service life and reduces the number of replacements. Proper process variables of UNSM technology which give the strongest fatigue strength are determined by comparing with S-N curve of rotary bending test result. Surface roughness, hardness and compressive residual stress on three kinds of test specimens are analyzed together with SEM analysis of fracture surface. Real shear pins are produced by the property of highest fatigue strength and installed to the hot mill stand for validation. They come to pass as twice as the original operation cycle.

Smith Prediction Monitor AGC System Based on CPSO Self-Tuning Pi Control

In accordance with the feature of pure delay in monitor AGC system for hot rolling mill, a new self-tuning PI Smith prediction controller based on chaotic particle swarm optimization (CPSO) is developed. The algorithmic principle and design method of new controller are given. Based on the typical monitor AGC model of tandem hot mill, the analysis of dynamic performance for traditional PI Smith prediction controller and CPSO self-tuning PI Smith prediction controller is done by MATLAB. The simulation results indicate that CPSO self-tuning PI Smith prediction controller has faster response and higher static accuracy than traditional PI Smith prediction controller.

The Thermomechanical Controlled Processing of High-Strength Steel Plate: A New View of Toughness Based on Modern Metallography

Modern thermomechanical controlled processing (TMCP) of advanced steels is now an important processing route in the production of engineering structures and products that are of value to society. The principles of TMCP are now practiced in the hot mill, cold mill and press forming shops around the world. Successful TMCP means that the proper metallurgical microstructure has been obtained in the required areas of the steel. The ideal microstructure is often defined by the correct phase balance and dimensions either of the parent austenite or final ferritic phase. Technological and economic demands have led to ever increasing levels of strength, especially for applications such as large diameter linepipe. The operative yield strengths in 18mm hot rolled plate have increased from X52(ferrite pearlite) in 1970 to X80(ferrite-bainite) today. The next frontier is the X100-X120 strength range, where bainitic or martensitic microstructures are required. It is clear that achieving a high-strength bainitic microstructure in heavy plate requires a high Carbon Equivalent value (C. E. II or Pcm), a rapid cooling rate, and a low water-end temperature. The requirement of high toughness and good weldability also means a low carbon content. This paper will describe the results of a research program where a steel of C. E. 0.56 and Pcm 0.23 was reheated, rough rolled for grain refinement, finish rolled for austenite pancaking, and direct quenched to below the Bs temperature. It was found that the strength and especially the toughness of the fully processed plates could not be explained using conventional metallographic techniques in conjunction with known structure-property relationships. However, the application of modern metallographic techniques based on FEG-SEM incorporating OIM led to microstructural characterization that more fully explained the observed mechanical properties. Of particular importance were the amount of MA micro-constituent, the crystallographic packet size of the bainite, and the high angle boundary character, especially the CSL boundaries, found in the microstructure. In the future, improved modeling of microstructural evolution and attendant mechanical properties will incorporate these important features.

Physical Simulation of Hot Rolling Steel Plate and Coil Production for Pipeline Applications

Within the techniques and equipments used to simulate industrial thermomechanical processing of High Strength Low Alloy (HSLA) pipeline steels, hot rolling laboratory mill equipped with cooling bed and coiling simulation furnace allows, not only accurate control of strains, temperatures, inter-pass times, and cooling rates but also enough amount of processed material for micro-structural characterisation and mechanical testing. Despite some differences with the industrial rolling, laboratory rolling offers a better simulation of the industrial rolling conditions than other thermo-mechanical simulators in terms of deformation mechanisms and processing constrains. This paper presents the results of simulation of different rolling schedules applied on pipeline grades in order to better understand the influence of the finishing rolling parameters namely: finish rolling temperature (FRT) and cooling routes on the microstructure and mechanical properties. It was observed that FRT and cooling rate have a strong impact on both grain refinement and precipitation behaviour, which leads to significant differences in strength and toughness. Furthermore variations of the above mentioned rolling parameters produce distinct fractions and distributions of austenite transformation products, variations in the final crystallographic texture and trigger diverse strengthening mechanisms (i.e. dislocation hardening). It was found that the accelerated cooling in a combination with a coiling simulation results in formation of microstructures with well developed low angle grain boundaries in comparison to the simulation made with air cooling. As a consequence the strength of the plates after accelerated cooling increases without changes in the Charpy impact toughness. It has been shown that the understanding of the effect of processing parameters on the microstructure of these steels is a key aspect for the optimization of their mechanical properties.

Oxide Structures Formed During the High Temperature Oxidation of Hot Mill Work Rolls

The high temperature isothermal oxidation behaviour of work rolls and the oxide structures resulting from this process are presented. Oxidation of these alloys at 615 °C under various environmental conditions resulted in the formation of oxide crystals of different morphologies, depending on the chemical composition of the alloys and the gases present in the oxidant atmosphere. Particularly, the surface oxidation of high speed steel and high chromium iron for work rolls in hot strip mills included the formation of whiskers, platelets, and crystallites. The composition of the oxidant atmosphere also influenced the oxidation rate of the specimens by promoting the formation of protective or non-protective oxides. The reasons for the development of the different oxide morphologies and the effect that the oxides formed on the surface exert on the behaviour of important tribological variables present in the hot rolling of steel such as friction are discussed.