SYSTEM-MODULAR APPROACH TO UPGRADING EQUIPMENT FOR ROLLING MILLS

This study describes workers’ exposure to fine and ultrafine particles in the production chain of ferrochromium and stainless steel during sintering, ferrochromium smelting, stainless steel melting, and hot and cold rolling operations. Workers’ personal exposure to inhalable dust was assessed using IOM sampler with a cellulose acetate filter (AAWP, diameter 25 mm; Millipore, Bedford, MA). Filter sampling methods were used to measure particle mass concentrations in fixed locations. Particle number concentrations and size distributions were examined using an SMPS+C sequential mobile particle sizer and counter (series 5.400, Grimm Aerosol Technik, Ainring, Germany), and a hand-held condensation particle counter (CPC, model 3007, TSI Incorporated, MN). The structure and elemental composition of particles were analyzed using TEM-EDXA (TEM: JEM-1220, JEOL, Tokyo, Japan; EDXA: Noran System Six, Thermo Fisher Scientific Inc., Madison,WI). Workers’ personal exposure to inhalable dust averaged 1.87, 1.40, 2.34, 0.30, and 0.17 mg m−3 in sintering plant, ferrochromium smelter, stainless steel melting shop, hot rolling mill, and the cold rolling mill, respectively. Particle number concentrations measured using SMPS+C varied from 58 × 103 to 662 × 103 cm−3 in the production areas, whereas concentrations measured using SMPS+C and CPC3007 in control rooms ranged from 24 × 103 to 243 × 103 cm−3 and 5.1 × 103 to 97 × 103 cm−3, respectively. The elemental composition and the structure of particles in different production phases varied. In the cold-rolling mill non-process particles were abundant. In other sites, chromium and iron originating from ore and recycled steel scrap were the most common elements in the particles studied. Particle mass concentrations were at the same level as that reported earlier. However, particle number measurements showed a high amount of ultrafine particles, especially in sintering, alloy smelting and melting, and tapping operations. Particle number concentration and size distribution measurements provide important information regarding exposure to ultrafine particles, which cannot be seen in particle mass measurements.

MODERN AUTOMATION TECHNOLOGY IN SERVICE OF INTEGRATED STAINLESS STEEL MILL

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

Estimation of individual dust exposure by magnetopneumography in stainless steel production

Efficiency of the pilger cold rolling of pipes process realization can be increased both by perfection of the rolling process and by a selection of rational parameters of the base technological equipment and the mills functioning regimes. Particular attention should be paid to the increase of reliability of functioning, increase of high-speed and productivity of pipe cold rolling mills (CRMs). Results of the system analysis of dynamics of pipe CRM working stand of various designs presented. A calculation algorithm elaborated and differential equations of the pipe CRM working stand obtained. Pictures of dynamic motions for selected pipe CRM working stand obtained. The analysis of theoretical studies showed, that for stabilization of the stand base elements it is necessary to increase the rigidity of the working stand correspondent elements. It was shown, that the stand rigidity increase reached by arrangement longitudinal bridge of variable thickness, connecting the internal and external structure’ casing. An optimal design roller actuator elaborated. Implementation of the actuator will enable to accomplish the technological process more effectively, since the unit’ elements can adopt all possible inaccuracy of the working stand manufacturing and assembling, as well as housing post deformation. It was ascertained, that the roller actuator of optimal design, above all, plays a role of an emergency gear of the pipe CRM working stand. The studies revealed that increase of productivity and quality of the manufactured products reached mainly by application of the working stand of rational design at the pipe CRM. The industrial running the modified variant of working stand design during eight years to roll hard-deformed steels and alloys confirm its high efficiency at production of precision high quality pipes.

The main objectives of any production are to increase productivity and reduce costs. Rolling production is no exception. This article discusses the modernization of the rolling mill by replacing the tube turning drive. At present, the pipe turns are carried out through a mechanical transmission by taking power from the main drive. The purpose of the article is to develop an automated system for the electric drive of the pipe turning, needed for the implementation of the technological process of cold rolling of pipes. On the basis of the given technological requirements, it is necessary to develop an electric drive of the mill with improved indicators of positioning of the working mechanism, and with the highest speed. This article analyzes the operation of the mill tube turning mechanism, compiles its description, identifies problematic issues and collects data. The main disadvantages of the existing system are identified and a solution is proposed that excludes them. For the electric drive of the pipe rotation, it is proposed to use a high-torque synchronously reactive machine. Application of an electric motor with a high overload capacity in combination with a high-speed control system, not only meets all technological requirements, but also makes it possible to provide the required angle of pipe rotation at high rolling speeds. This study showed that the implementation of this project solves the following tasks: Technical re-equipment of the enterprise – replacement of outdated equipment with a high degree of moral and physical wear and tear with modern equipment with the possibility of automation; Improving the reliability of equipment, reducing operating costs, reducing the time of non-standardized downtime due to breakdowns of equipment, distribution – feeding mechanisms (overtaking clutches, lever and cam units, etc.); Increase in rolling speed and mill productivity due to the use of a high-speed control system.

In order to design variants of routes for the production of cold-rolled pipes from titanium alloys, it is necessary to: use in each pass of the route all possible variants of equipment for cold rolling of metal, be limited to uniform dimensions of the diameters and wall thickness of the blanks, limit the dimensions of the initial blank to the range of blanks and use deformation modes that ensure maximum use plastic properties of metal. The purpose of the study is to analyze the method of route calculation, technological maps, technology, main and auxiliary equipment for the production of pipes from titanium alloys on mills of cold rolling of pipes with rollers. On the basis of these data, develop an algorithm for calculating routes and technological maps for the production of pipes on mills for cold rolling of pipes with rollers and the corresponding software complex. The work uses an improved method of calculating the rolling route for the production of cold-rolled titanium alloys from pipes on a cold rolling mill with rollers. On the basis of practical data, analytical dependences of the absolute compression along the diameter on the diameter of the finished pipes were constructed. Two variants of regression lines are considered: linear, power. Statistical analysis of dependencies makes it possible to choose the function that adequately reflects the experimental data, that is, the calculation of which with rounding to integers gives the minimum error. Derived formulas of dependence of the maximum possible thickness of the pipe wall on the wall thickness of the workpiece according to the type of steel, the thickness of the pipe wall and the workpiece, and the standard size of the mill for cold rolling of pipes with rollers. The developed algorithms and software make it possible to solve the issue of designing routes for the production of cold-rolled pipes from titanium alloys on the mills of cold rolling of pipes with rollers on the basis of mathematical models of deformation processes.

The aim. Subsequent development of procedure for calculation of the kinematic parameters of the process of tube deformation in the cold tube pilger roll rolling mills with purpose of decreasing the value of axial forces. Methods. The new method (procedure) for the choice of the rational relationship of values of the forced rolling radius and the roll barrel radius in the mill KPW (method of the work minimum) had been assumed as the basis of development of the procedure for calculating the kinematic parameters of the tube deformation process in the cold tube pilger roll rolling mills. The outcome. The main dependencies known for now, which are used for calculating the value of the natural rolling radius and the roll barrel radius had been considered in the present paper, as well as the main practice used for decreasing the value of axial forces in the CTR mills. A procedure had been proposed for calculating the kinematic parameters of the tube deformation process in the mills of the cold tube pilger roll rolling (the method of the work minimum). Basing on the outcomes of industrial exploitation of the given method one drew the conclusion as to effectiveness of the proposed procedure. The scientific novelty. Basing on existing dependencies, the development of procedure had been proposed for calculating the rational relationship of the forced rolling groove radius and the roll barrel radius in the cold tube rolling mills. The procedure is based on the intimate analysis of axial forces, which are determined proceeding from all the basic parameters of the process. The practical importance. The given method allows optimizing not only the maximum values of axial forces at the direct and reverse stroke of the stand, but also the intensity of forces distribution along the cone of deformation. The method (procedure) had been used while calculating a number of roll pass designs for rolling tubes of titanium alloys in the mill KPW–25.

The objective of the present study was to determine whether workers in stainless steel production with low exposure to various forms of chromium show an increase in micronucleated nasal cells or an excess of nasal symptoms or disease. Altogether, 48 workers employed in a stainless steel production chain were studied, 29 of them in the steel melting shop with exposure to hexavalent chromium (Cr(6+)), 14 in the sintering and crushing departments of the ferrochromium plant with exposure to trivalent chromium (Cr(3+)) and five in the mine with exposure to chromite ore (Cr(3+)). Thirty-nine workers from the cold rolling mill, with very low exposure to chromium, served as referents. All the subjects were never smokers with a minimum of 14 years employment in the same department. There were no significant differences between the exposure groups and the referents regarding the mean frequency of centromere-negative or centromere-positive micronuclei (studied by pancentromeric fluorescence in situ hybridization), nasal diseases and symptoms or mucociliary clearance of the nasal cavity. No statistically significant differences in the incidence of cell atypia or inflammatory cells were detected between the exposed workers and the reference group, except for an increase in lymphocytes among the chromite ore workers. Anterior rhinoscopy indicated slight inflammatory changes in nasal mucosa and secretion more often in the Cr(6+) and Cr(3+) groups than in the referents, the Cr(6+)-exposed workers showing more livid or oedemic epithelium. In conclusion, the stainless steel production workers, with low exposure to dusts or fumes containing hexavalent or trivalent chromium, did not show clinical changes in the nasal mucosa or an increase in nasal cell micronuclei or symptoms of nasal diseases, except for slight changes in the nasal epithelium and secretion.

It is pointed out that there are several possibilities to realize an AC variable speed drive with cycloconverters. The motor can be an asynchronous or a synchronous type and the cycloconverter can be operated with or without circulating current. The author presents the characteristics of the different solutions and compares their performance in rolling mill main drive applications. The comparison is based on real applications in hot and cold rolling mills and on additional simulations. It is shown that the decision for the optimal configurations depends on the individual requirements of the technological process. For example, the required peak load and constant power range may have a remarkable influence on the design of the drive system, depending on the motor type. A short report about practical applications in hot and cold, reversing and finishing rolling mills is given. >

This paper focuses on the application of principal component analysis (PCA) to thoroughly analyse and interpret multidimensional data from a cold rolling process. The analysis includes the effects of variables on the final properties of strips in a cold rolling mill. Unscrambler software was used to analyse and identify hidden variables. Variable correlations were also used to derive correlations between the control parameters. The results of this research will be used to improve the selection of material in order to reduce the occurrence of defects in the cold rolling process and to improve the adjustment of the set points that are performed in every pass or section of the cold rolling process. The hot rolled strips that enter the cold rolling mill are made of different materials and are produced by different strip manufacturers. Some strips break during the thickness reduction process in the cold rolling mill. This paper focuses on two possible causes of breakage: non-uniform strip material properties and failures in the rolling mill process. Two types of rolled strips (those that break and those that do not break) were compared to identify causes of breakage. The results indicate that breakages are caused by material or process failures. PCA was applied to the dataset in order to identify and analyse the relationships between the variables in the process. This information was used to interpret and diagnose the process behaviour. Swarm analysis and relating observations to process behaviour were able to distinguish between different start-up conditions, and between desirable and undesirable process conditions.

In stainless steel production as in almost any kind of industrial activity it is important to know what kind of influence different factors such as process variables and conditions have on the process outcome. In order to productionally, economically and ecologically optimize the refining processes used in the production of stainless steels, one has to know these connections between the process outcomes and the process variables. In an effort to obtain this knowledge, process modelling and simulation as well as experimental procedures and analyses can be used as valuable tools (Heikkinen et al., 2010a).

The EAF Dusts and pickling sludges generated in the stainless steel production contain a lot of valuable metals such as iron, nickel, chromium and manganese. Their compositions are similar to those of laterite nickel ore, and sometimes even better than that at the contents of nickel and chromium. But it is regret that these valuable resources were random piled up or landed fill disposal. In this paper, the typical EAF dusts and pickling sludges and reductant coke powder were mixed in appropriate ratio, and then smelted in a medium frequency induction furnace. In the smelting process, the lime powder and fluorite was added to fluxing, and the ferrosilicon powder was added to strengthen the reduction. The product nickel-chromium-iron can be used as the raw material for stainless steel or cast iron production. The technology has good social and economic benefits.

Reduction in Roll Wear Through Technological Interventions at CRM & SSM of Rourkela Steel Plant

: The area of plastic deformation at a crack tip can be estimated using Irwin's plastic zone correction factor derived from linear elastic theory. The size of the plastic zone is considered to be a measure of fracture toughness, since the resistance of a metal to crack propagation is related to the deformation ahead of the crack tip. The relationship is confirmed between fracture toughness and plastic zone size calculated from elastic considerations for steel, aluminum, and titanium alloys. Within each of the metal systems, the calculated plastic enclave increases with increasing Dynamic Tear (DT) test energy for fracture. However, the plastic zone size is an unreliable indicator of the amount of energy absorbed in the formation of the zone when a comparison is made among different metal systems. For a given size plastic enclave, the energy absorbed by the metal during the deformation process is least for aluminum alloys, while significantly greater for titanium and steel alloys in that order. When brittle alloys are compared, the difference among metal systems in the quantity of energy absorbed to form the zone is considerably diminished.