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In the present investigation, a worn-out hot strip mill roller of AISI 4140 material has been reconditioned by the deposition of hardfacing. The roller belongs to Arcelormittal Nippon Steel India, which is used to transfer metallic strip. This roller is continuously subjected to wear due to the oxide scale on the slab surface. Its regular maintenance and repair cause significant production loss. Therefore, two hardfacings of martensitic stainless steels with different composition are deposited on the surface of AISI 4140 steel by submerged arc welding and comparative analysis is performed to achieve the superior wear resistance. Further, hardfaced samples are evaluated on the basis of abrasive wear test, hardness, microstructure and worn-out morphology. The results showed that the hardfacing with combination of large volume fraction of martensite and small volume fraction of residual austenite attained the highest value of hardness up to 380 HV whereas the reverse combination showed 332 HV hardness and the minimum mass loss is observed for sample with 380 HV hardness. At the end, the most suitable material for the hardfacing of AISI 4140 is suggested. The outcomes of this work would be beneficial to improve the service life of roller of hot strip mill.

Hot strip mill, one of the most important units of an integrated steel plant, is operated by mill setup model. The conventional mill setup models calculate thermal, reduction and speed schedules of...

Work rolls in the hot strip mill withstand extreme service conditions, especially when electrical steels are rolled, resulting in severe roll wear and fatigue. High-speed steel (HSS) work rolls and rolling lubrication are applied to the mill to improve roll wear and fatigue. Tests show that HSS work rolls manifest good performance in wear, fatigue and oxidation resistance during electrical steel hot rolling. The wear loss of HSS work rolls decreases remarkably, but the heat dispersion deteriorates. The service period of HSS work rolls can be increased significantly, but the fatigue failure risk increases as well. In addition, rolling lubrication is proven to be effective in alleviating roll wear and fatigue, but high temperature reduces the positive effects of rolling lubrication. Roll wear and fatigue are considered to be parallel and mutual effective processes. The applications of HSS rolls together with rolling lubrication contribute the most to the improvement of work roll wear and fatigue during electrical steel hot rolling.

Hot-rolled strips are cooled on the run-out table to achieve the customer-required mechanical properties. Cooling reduces the oxidation, which can assist the coiling operation. The ability to obtain a range of mechanical properties from a single steel grade reduces the use of alloying elements (elements added to a metal or an alloy which are incorporated in the metallic structure and change in the properties of the basic alloy) and the size of the slab inventories. So in this paper, the high-temperature steel strip cooling pattern with the temperature of 870 °C and reaching the temperature of 630 °C using water and air is studied. Moreover, the numerical simulation of the high-temperature strip cooling and its cooling method is carried out. The results are compared with the similar sampler ones. The changes of three key parameters such as change in strip speed and its effect on cooling rate, change in pattern and arrangement of water showers and its effects and change in the cooling water temperature are investigated. It was found that the uniformity of the heat distribution inside the strip was increased, but the temperature of the strip was lower than the required temperature. The middle and up surface temperatures of the strip were performed at a speed of 3.48 (m s−1), which showed a very good match with the actual tested sample.

Some aspects of deformation, precipitation, and recrystallization behavior in medium carbon V-microalloyed and low carbon Nb/Ti-microalloyed steels are presented in the paper. Changes in microstructure are explained together with methods of quantification. The temperature of No-recrystallization (Tnr) is defined as a milestone to show the onset of retardation of recrystallization while the apparent activation energy for hot working shows the extent of this retardation. In the case of high cooling rates, this method is not sufficiently sensitive and Trl (recrystallization limit temperature) and Trs (recrystallization stop temperature) must be evaluated from softening data. Paper presented the possibility to estimate Tnr temperature on six stands finishing train at Hot Strip Mill in HBIS Iron and Steel Serbia, Smederevo as well as the activation energy for static recrystallization, QSRX, derived from Tnr temperatures.

The purpose of the work is to determine rational schemes for their production by analyzing the technological and design parameters of a number of broadband mills that roll hot-rolled strips less than 2,0 mm thick. It is shown that at present there is a constant increase in the production of extremely thin hot-rolled strips (0,8-1,5 mm thick), which can be used instead of more expensive (by $ 20-30 per ton) cold-rolled strips. The development of the production of hot-rolled strips of such a thickness is limited by a number of problems, in particular, the low temperature of the end of rolling (760-820 °C), which leads to a significant decrease in the ductility of the rolled stock; limiting the rolling filling speed, which does not allow increasing the temperature of the end of rolling the complexity of controlling the cross-sectional profile and flatness of the strips. Using mathematical modeling, it was found that the strip thickness and rolling speed have the greatest influence on the temperature of the end of rolling. The thickness and temperature of the rolls at the entrance to the finishing group of stands have a lesser effect. A decrease in the number of stands in the finishing group increases the temperature of the end of rolling at a constant thickness of the rolls, but when the thickness of the rolls changes in accordance with the number of stands, the effect is significantly reduced. The most favorable technological parameters for the production of extra-thin hot-rolled strips are provided by casting and rolling units, which are characterized, in comparison with broad-strip mills, as a rule, by a greater thickness and temperature of the rolls (or continuously cast slabs) and a smaller number of stands. An increase in the thickness of billets (slabs) requires an increase in the permissible values of the energy-power parameters of rolling, as well as the use of special solutions that will ensure minimal heat loss by the rolls before entering the finishing group of stands. Calculations show that, based on the reliable maximum refueling speed of hotrolled strips (10-11.5 m / s) achieved in the industry, the minimum thickness of strips with high plastic characteristics is: for broad-strip mills - 1.9-2.0 mm; for casting and rolling units, depending on their type - 1.3-1.6 mm.

For the present contribution phase transformations in primary and secondary mill scales discarded from a hot strip mill have been investigated by using synchrotron X-ray absorption spectroscopy and thermal analysis methods. Phase transformations in the scales are influenced by calcination parameters such as temperature, heating rate and isothermal interval. Magnetite, a highly interesting iron oxide for its availability in wide ranges of applications, increases its fraction after calcination at 673 K at a heating rate of 5.38 K × s−1. This is confirmed by both characterization techniques. The calcined primary scale is found almost unchanged due to the existing predominant hematite phase. However, the additional promotion of hematite occurs at a longer isothermal calcination period at 1073 K. The majority of the results corresponded to the literature data and corroborate the assumption for a further purification process of industrial iron oxide by-products.

Universal spindle of Finishing Stand in Hot Strip Mill (HSM) plays a vital role in providing product thickness as per customer requirement. In a rolling mill, upper and lower work rolls are connected with single motor by their respective universal spindle. The spindle allows upward and downward movement of work rolls by allowing its shaft to bend up to ~15o angle. This bending is only possible by universal cross positioned at its both ends. One of the cross bearing located at operator side got failed during operation. All the site evidences were carefully noted down and piled up to find out the root cause of the failure. Metallurgical analysis like microstructure, hardness, inclusion rating and chemical analysis were carried to find out material related issue if any. Quality of lubricants used at different pins of cross bearing was also checked by crackle test. Evidences and metallurgical analysis results suggested that the cross bearing failed due to deterioration of lubricant quality during service. Lubricant deteriorated due to water ingress into cross bearing through its polymeric seal which was not properly applied at the time of its assembly.

Bearings are one of the most widely used and highly stressed engineering components. If properly manufactured, mounted, operated and maintained, they can give excellent service life. However, they may suffer from premature failure due to multitudes of reasons. Current work deals with pinpointing failure mode and root cause analysis of a pinch roll bearing at coil box of a Hot Strip Mill. Macroscopic and microscopic analysis revealed that bearing failed in Rolling Contact Fatigue mode. All metallurgical, mechanical and maintenance factors that might contribute to rolling contact fatigue were analyzed independently. It was concluded that misalignment led to accelerated Rolling Contact Fatigue. Striation marks rarely reported for rolling contact fatigue of bearing steels were observed to confirm fatigue mode of failure. Recommendations for preventing similar failures in future have been provided.

Hot rolled ultra-high strength steel with a gauge range of 3–10 mm (0.118¨–0.395¨) was developed using conventional slab caster and hot strip mill technology at Stelco Inc. (Stelco) to meet standar...

Hot rolling is an essential industrial process in the production of sheet steel, a widely used product in manufacturing and construction. The hot strip mill is a complex unit including many processes and control loops and its modeling is a challenging task owing to the variety of phenomena that occur within the mill. Model validation is also challenging owing to a scarcity of measurements. In this study, a computer simulative emulation that can analyze the dynamic behaviors of the tandem hot rolling process with original non-linear rolling models has been developed and validated against a linear model and measured data. Moreover, the influence coefficients of rolling process parameters were calculated by analyzing the rolling data.

In hot rolling, metal oxides formed on steel surface can generally be classified as primary, secondary and tertiary oxide scales, corresponding to the reheating stages, the roughing stages and the finishing passes of continuous mills, respectively. The tertiary oxide scale grows into the final products on the hot-rolled steel strip during the finishing rolling and the subsequent cooling down to ambient temperature. We provide here a systematic overview of the oxidation mechanism, microstructure and microtexture development of the tertiary oxide scale. Mechanism of oxidation and Fe3O4 precipitation in tertiary oxide has been given as the fundamental theory. Three main sections has been divided in this review. The first section includes experimental investigations on microstructure evolution from the formation of oxide scale during hot rolling, then through continuous cooling, to Fe3O4 precipitation behaviour in storage cooling of hot-coiled strip. By using electron backscatter diffraction (EBSD) to characterise both the steel substrate and the oxide scale concurrently, the second section has further dealed with the texture-based analysis of oxide scale: phase identification, orientation analysis and coincident site lattice (CSL) boundaries. The third section has provided the general type of crystallographic texture and its evolutions in deformed Fe3O4 and steel substrate. Finally, the upcoming challenges have been addressed in this intriguing and promising research field.

The production of hot-rolled sheets of high-strength and wear-resistant special structural steels by direct quenching from the rolling heat is a cost effective and energy-saving alternative to traditional production via downstream quenching the previously cut-to-length plates. Reaching the required strength and toughness parameters in combination with best flatness of the sheets requires strict compliance with the pre-set rolling and cooling conditions over the entire strip width. Using two high-strength low-alloyed steels, plant trials have been carried out to study the effect of the cooling conditions and the coiling temperature on mechanical properties, impact toughness and flatness of cut-to-length sheets made of hot-rolled strip. The results showed that by applying optimized cooling pattern and low coiling temperatures, high-strength steel sheets with outstanding mechanical properties and good flatness can be produced.

Because of suitability for hot-dip zinc-coating, there is some concern about the use low silicon (Si) content in normalized or normalizing rolling S355J2+N structural steel with minimum specified yield strength of 355 MPa. However, decreasing Si content leads to a decrease of solid solution hardening, whereas decrease in strength should be compensated by alternative mechanism. One possible solution is the use of microalloying with niobium (Nb). Based on available results obtained on own and competitive material, we projected and produced S355J2+N hot-rolled coils (HRC). The results show that the produced material fully satisfies the requirements of the EN 10025-2/2004 quality standard. Furthermore, strength values in normalized conditions were lower than those in normalizing rolling condition.

In aluminum strip production, profile formed in hot rolling is critical to flatness control in the subsequent cold rolling, and selective work roll cooling is marked by the flexible control of complex high-order shape defects. Therefore, a setup system of selective cooling is developed to achieve the whole cross-section profile control in hot rolling. It includes a real-time work roll thermal model based on finite deference method and a strip profile predictive model based on RBF network. A spray pattern is obtained using an iteration method, as the "basic pattern" for the setup, for the situation when roll thermal contour need to be maintained. Based on the predicted profile error, adjustment of the basic pattern is made by fuzzy inference to get the final setup spray pattern, under which the profile error can be reduced during the threading.

The occurrence of dynamic recrystallization in the intermediate stands of the Finishing Mill of a Hot Strip Mill promotes substantial softening of the rolling stock, a situation that can cause operational problems and even scrapping of the strip. The aim of this work was to identify the specific process conditions that can lead to this situation, which was carried out through the application of a microstructural evolution model. It was verified, for the specific conditions of the Cubatao Works of Usiminas, that this problem generally occurs during the processing of thin hot coils, with a relatively low Nb content and under rolling temperatures slightly lower than the normal range.

The paper describes the application of a Self-Organising Map for the analysis and the interpretation of measurements taken by a Non-Destructive Testing system named IMPOC\({}^\circledR \) and related to the hardness of steel coils after the hot rolling mill. This work addresses the problem of understanding whether distinct process conditions may lead to non-uniform mechanical properties along the coil. The proposed approach allows to point out, for each specific steel grade, some process conditions that are more frequently associated to disuniformities.

Aimed at the main factors of hot rolled strip steel product width fluctuation, rolled piece is put forward to plasticity coefficient and entrance width as the input variables of feedforward AWC control algorithm.Expounds a kind of optimization of plasticity coefficient Q feedforward AWC control system principle and plasticity coefficient Q of linear prediction algorithm.Field application shows that the Q prediction feedforward AWC has significant effect on inhibition of hot rolled strip width deviation.

The ultra-fast cooling technology has been developed rapidly in order to develop iron and steel material with high performance. A variety of factors including the strip running speed, water temperature, water spray speed and strip temperature will affect strip cooling aspect during ultra-fast cooling process. These factors, which affect heat transfer coefficient, should be analyzed in order to achieve accurate control of strip cooling path during ultra-fast cooling process. The heat transfer coefficients of the hot rolled strip with various cooling parameters were obtained by numerical calculation method. By comparison, the influencing law that the cooling process parameters had made to heat transfer coefficient were obtained. It was found that strip running speed can affect heat transfer coefficient by influencing residual water distribution on top of the strip surface. Water temperature, water spray speed and strip temperature can also affect heat transfer coefficient with different changing law.

Serious efforts have been made to simultaneously improve the strength and ductility of steels for different applications. However, steel with the ultimate tensile strength (UTS) above 1200 MPa with minimum elongation of 20 pct is still difficult to produce. In the current work, an effort has been made to design such a steel that could be directly produced in any hot strip mill, after accelerated cooling on the runout table followed by coiling. Basically this steel consisted of C, Mn, Si, and Cr and the intended final microstructure at room temperature was about 80 pct carbide-free bainite and 20 pct retained austenite. The steel was exposed to a thermal treatment which is generally experienced by a hot strip coil. This newly developed steel possesses an UTS of minimum ~1370 MPa with minimum ~21 pct elongation. The combination of such encouraging mechanical properties can be primarily attributed to the formation of ultrafine bainite plates (~100 to 130 nm) and a high density of dislocations arising out of the bainitic transformation. The presence of sufficient quantity of retained austenite (minimum 21 pct) in the final microstructure could be the reason for the attainment of outstanding ductility values at such a high strength level.

A non-contact laser ultrasound measuring system for material properties of high-strength steels was developed. This system can measure material properties such as crystal grain size by analyzing high-frequency ultrasound waveforms generated by a pulsed laser. For this purpose, a light equalizing device is applied to the pulsed laser path so that the excited ultrasound can propagate a long distance without being weakened by diffusion. Therefore, the characteristics of the waveform can be captured clearly and analyzed correctly by this system. The advantages of this device were confirmed by numerical simulation of the ultrasonic propagation. The capability of this measuring system was shown by experimental measurement of various high-strength steel specimens. The measured crystal grain sizes showed good agreement with the results of SEM-EBSD observations. The measured crystal grain size also showed good correlation with the tensile test results.

The precision of strip flatness depends on several factors; wear of rolls is one of the main variables that have influence on the surface quality of the strip. The wear of the rolls represents a complex friction condition, sometimes the wear in the backup roll is not analyzed because the strip is not in contact with the backup roll; however, after several campaigns of rolling, the wear in the backup roll becomes dangerous because the pressure distribution is not uniform. Investigation of mechanism of the surface deterioration of the backup roll for the hot strip rolling is very important for the development of the automatic strip shape control system used in hot strip mills. A mathematical model is developed considering the Hertzian pressure distribution between two cylinders with parallel axes. It is used in real time for calculating the wear in the backup roll and in this manner take decisions for preventing finished product reworking or damage of equipments, which result in accidents caused by excessive wear in the backup rolls.

The microstructure, mechanical and tribological properties for three different materials, high speed steel, high chromium iron and indefinite chill iron, used for hot strip mill work rolls have bee ...

Most of the commercial metallic materials undergo at least one hot deformation stage during fabrication. Hot deformation processing leads to the production of plates, strips, rods, pipes and other shapes at lower overall cost when compared to the cold deformation/annealing route. Comprehensive study of the metallurgical phenomena during hot deformation has enormous potential application in the control of industrial rolling processes. Understanding of the microstructural and mean flow stress evolution lead to sound steel developments and innovative rolling schedules. The models predict parameters such as grain size, fractional softening (static and dynamic) and strain induced precipitation which are useful to improve rolling schedules. Effects such as incomplete softening and strain accumulation can be easily detected as well as their consequences on the final grain size and mechanical properties. In this regard, special attention must be given to steels, the most important metallic material in terms of history, present and future. In this paper, three hot rolling routes will be analyzed in order to produce high strength linepipe steels. Examples were selected on how the use of modelling during development stage can help to meet mechanical properties, mainly toughness and drop weight tear test. Firstly, it is presented a brief overview on mathematical models applied to hot rolling. Thin slab casting/direct rolling, hot strip mill and plate mill are exemplified in the present work. The development of new steel grades can greatly accelerated with the aid of modelling, which is an useful, low-cost technique.

The influence of the hot-rolling parameters used in 2000 continuous broad-strip mills on the structure of high-strength dual-phase steel is investigated. The structure formation and mechanical properties of the steel are simulated by means of Hot Strip Mill Model (HSMM), ThermoCalc, AusEvol+, and AusTran software. A Gleeble-3800 thermomechanical simulator is used for physical modeling of the metal treatment. By adjusting the treatment parameters, dual-phase ferrite-martensite, ferrite-bainite, or ferrite-martensite-bainite steel may be produced.

The superposition of work roll initial crown, the work roll bending and flattening crown, the work roll wearing crown and the work roll thermal crown makes the final hot strip. In this paper, new models based on numerical method have been obtained to predict the roll force, the work roll wearing crown and the work roll thermal crown utilizing experimental data provided by Mobarake Steel Complex. Meanwhile, the work roll bending and flattening crown has been obtained from finite element method as well as elasticity approach. Then, a computer programing has been written to obtain the work roll initial crown in order to get desired strip profile. This program is called Initial Crown Prediction Software (ICPS). Finally, the obtained initial crowns from ICPS were applied for different stands of hot strip mill of Mobarake Steel Complex, and the strip profile shows a good agreement with the desired one for the mentioned mill.

An optimization solution to roll shifting strategy for alternately rolling campaign is presented. All the strips in a rolling campaign are divided into narrow strips and wide ones, and shifting position of narrow strips is obtained by the recursive method, and then shifting position of wide strips is optimized by NSGA-II which is a multiobjective genetic algorithm. For wide strips, a multi-objective optimization model of roll shifting strategy is pro posed, which takes 3 wear contour factors including edge smoothness, body smoothness and edge drop as optimization objectives. The Pareto optimal front of roll shifting strategy can be gained quickly by NSGA-II, which suggests a series of alternative solutions to roll shifting strategy. Analysis shows that the conflict exists among the 3 objectives. The final optimal solution is selected from the Pareto optimal solutions by the weighted-sum decision-making method. Industrial production proves the validity of the solution, and it can improve strip profile of alternately rolling, reduce strip edge wave, and extend the rolling miles of rolling campaigns.

The decrease in hot strength or even rolling load as strain increases in some stands of the finishing hot strip mill with no metallurgical reasons is a relatively common event. Apparently this fact is associated with modification in the tribological conditions between rolling stock and work roll surfaces due to unexpected interactions with scale. The aim of this work is to determine the values of the friction coefficient in the several stands of the finishing hot strip mill at Usiminas-Cubatão, as well to determine quantitative relationships between this coefficient and relevant process parameters, like strain degree and peripherical work roll speed.