Slabbing Mill Research Articles

A Finite Element Approach to Conduct Machinability Studies on Age-Hardened AA6061 Matrix Hybrid Composites

AA6061, a popular structural material, has found widespread usage in the automotive and aerospace domains. The current work explored the effect of the improvement of mechanical properties on the machinability of AA6061 through finite element analysis. Three compositions of AA6061 containing 2 wt.% graphite and 0, 2, 4 wt.% granite dust were fabricated by stir casting. In the current work, a finite element model of a slab milling cutter with eight teeth was designed with high-speed steel (HSS) as the tool material. The LS-DYNA module of ANSYS was used for simulation of the milling operation, selecting two peripheral speeds for the cutter during the machining of the workpiece. Surface milling was carried out on the cast slabs of the three compositions to study chip formation. At higher cutting speeds, there was an increase in the von Mises stress as well as material deformation. An increase in the weight fraction of the ceramic fillers led to a corresponding increase in the von Mises stress and material deformation. The experimental results from face milling of the three compositions showed that the surface roughness increased with an increase in the content of ceramic fillers and a decrease in chip size.

The research of one-stage particle size-reduction process of blocked frozen meat with multiple cutting tools with milling operation method

This article shows experimental data about energy demands of innovative one-stage particle size-reduction process of frozen meat, formed in blocks, with milling operation method. We researched the particle size-reduction of meat blocks (beef and pork) by tools of different construction and shape of cutting edge: a slab mill with small edge and a fitted on shaving milling tool with a hard-faced knife. This study based on results of measuring three-phase active power, used by the cutting electric drive in working condition. The article presents the calculation of the measurements of numerical characteristics (mean value and mean square deviation) of statistical samples of power values with completing particle size-reduction tool with milling tools. The research shows that placing additional sustainer, that fixes a block of meat directly near the cutting zone, leads to decrease of energy demands for the cutting process up to 20% and to lower the dispersion of power values more than three times. The data obtained during the research let work out technical requirement specification for producing a commercial prototype of cutting particle size-reduction. The data allow creating the calculate method of numerical characteristics of a random process for a load of multiple razor tool in working condition. That model is used for designing an intellectual system of management of technological process on the transfer line for meat product producing with using one-stage particle size-reduction of raw materials with the milling method.

Experimental study on micro electrochemical slab milling using disc tool electrode

In this study, a method of micro-electrochemical slab milling with disc electrode is proposed for fabricating micro-groove structures on the surface of the workpiece. The disc electrode is in-situ prepared by micro-WEDM and subsequently used for micro-electrochemical slab milling process. The effects of the main electrochemical parameters, such as electrode feed rate of disc electrode and pulse width of power generator, on the width of the micro grooves and surface quality on 304 stainless steel were discussed. Finally, a micro-groove with a groove width of 254μm and good surface quality has successfully processed using the disc tool electrode with edge width of 170μm and proper process parameters. The proposed method broadens the machining flexibility and capability of micro electrochemical machining technology.

Dynamical processes in a multi-motor gear drive of heavy slabbing mill

A real case study is represented of abrupt failures in a new multi-motor gear drive of vertical rolls in the heavy slabbing mill. Modal analysis is conducted, and the lowest torsional vibration modes are verified by the data from an industrial plant. Conditions of parametric resonances due to variable stiffness of teeth are determined within the range of working speed. The branched gear drive is investigated by the non-linear dynamical model with backlashes. It is shown that instantaneous dynamic loads in driveline are strongly dependent on the difference in gap sizes and phase shift between two intermediate gears in the output gear wheel coupling. Deviation in electrical parameters by 0.5 % is considered as the additional cause of not equal load sharing of parallel motors. Results of this research allowed preventing further failures of the gearbox and optimizing slabbing mill control. The proposed approach can be used in other multi-motor machines.

열연 슬라브 압연에서 워크롤 표면 원주방향 인장응력 감소를 위한 냉각 방법

The work roll surface temperature rises and falls repetitively during hot slab rolling because the work roll surface is cooled continuously by water. This study focused on Std. No. 7 to determine a cooling method which significantly reduces the tangential tensile stresses on the work roll surface of the hot slab mill at Hyundai Steel Co. in Korea. A series of finite element analyses were performed to compute the temperature distribution and the tensile stresses in the circumferential direction of the work roll. The virtual slab model was used to reduce the run time considerably by assigning a high temperature to the virtual slab. Except for the heat generated by plastic deformation, this is equivalent to the hot rolling condition that a high temperature slab (material) would experience when in contact with the work rolls. Results showed that when the virtual slab model was coupled with FE analysis, the run time was found to be reduced from 2000 hours to 70 hours. When the work roll surface cooled with a certain on-off patter of water spray, the magnitude of the tangential stresses on the work rolls were decreased by 54.1%, in comparison with those cooled by continuous water spraying. Savings of up to 83.3% in water usage are possible if the proposed water cooling method is adopted.

Influence of slab milling process parameters on surface integrity of HSLA: a multi-performance characteristics optimization

An attempt has been made in this paper to determine the optimal setting of slab milling process parameters. Four process parameters, i.e. cutting fluid, cutting speed, feed and depth-of-cut each at three levels except the cutting fluid at two levels, were considered. The multi-performance characteristics of the process were measured in terms of surface integrity defined by surface roughness, surface strain and micro-hardness of the work-piece. Eighteen experiments, as per Taguchi’s L18 orthogonal array, were performed on high-strength low-alloy steel. Grey relational analysis, being a widely used technique for multi-performance optimization, was used to determine Grey relational grade. Subsequently, Taguchi response table method and ANOVA were used for data analysis. Confirmation experiment was conducted to determine the improvement in the surface integrity using this approach. Results revealed that machining done in the presence of cutting fluid, at a cutting speed of 1,800 r.p.m. with a feed of 150 mm/min and depth-of-cut of 0.23 mm, yielded the optimum multi-performance characteristics of the slab milling process. Further, the results of ANOVA indicated that all four machining parameters significantly affected the multi-performance with maximum contribution from depth-of-cut (33.76%) followed by feed (24.02%), cutting speed (16.29%) and cutting fluid (13.21%).

Russian

Russian

Tool behavior at alternating thermo-mechanical loads during milling of compounds out of aluminum and spheroidal cast iron

The mass of high-performance components can be reduced by the use of materials with a high ultimate strength. However, due to increasing demands on the performance of such components this design strategy reaches its limits, especially if certain parts of the components demand special physical properties. Therefore, in a load-dependent strategy hybrid components out of compounds are used. Through this, suitable materials are placed in the highly loaded component areas. This contribution presents results of experimental investigations of the tool behavior when milling compounds. The focus is on tool wear during face slab milling of a compound out of an aluminum alloy and a spheroidal cast iron. In order to distinguish between the thermal and mechanical influences on the tool wear, different material combinations are used. The influence of tensile strength is studied during the milling of materials with the same heat conductivity (GJS400/GJS600), while the influence of the heat conductivity is examined with materials with comparable tensile strengths (AW2030/GJS400).

Geometric Modeling of Fluted Cutters

Geometries of cutting tools are usually represented by two-dimensional models. This paper outlines the construction of detailed computer aided design models for a variety of fluted cutters that includes slab mills, end mills, and drills; and establishes a new three-dimensional definition for the geometry of fluted cutters in terms of biparametric surface patches. This work presents unified models of both plain and helical slab mills, end mills (with different end geometries), and drills (with a variety of point styles). The surfaces meant for cutting operations, known as flutes, are modeled as helicoidal surfaces. To model the flutes, sectional geometry of tip-to-tip profile is developed and then it is swept according to a sweeping rule, determined by the type of the cutter under consideration. The slab mill consists of flutes and two planar end surfaces, while the end mills and drills have shanks and end geometries also (in addition to the flutes). The geometric models of shank and end geometries are separately developed. The transitional surfaces of these cutters are modeled as bicubic Bézier surfaces or biparametric sweep surfaces. The proposed models employ a novel nomenclature that defines the form of cutting tools in terms of three-dimensional rotational angles. The relations required to map the proposed three-dimensional angles to conventional angles (forward mapping) and their reverse relations (inverse mapping) are also developed for all three types of fluted cutters. The new paradigm offers immense technological advantages in terms of numerous downstream applications.

Use and prospects of plate casting-rolling modules

Mini-mills and CRMs have come into use for several reasons. The energy crisis in the 1970s intensified the effort tc develop and introduce energy-saving technologies such as the hot-charging of slabs into the reheat furnaces of hot-strip milh (HSMLs) in slabbing-mill -- HSML complexes. This practice was widely introduced in the USSR in the t970s. For example the percentage of slabs charged hot into the furnaces of the 1680 mill at the "Zaporozhstal'" combine increased 88%. Ener~ was also saved by transit (direct) rolling, with slabs being sent directly from the slabbing mill to the HSML and by-passing the reheat furnaces. These methods were later incorporated into continuous-caster -- HSML complexes and were used to the greatest effect on the largest scale in Japan. However, use of the given technologies required the development of various devices, accessories, and transport equipment, beginning with the continuous caster and ending with the finishing group of stands. Also, modifications had to be made to the production process along the entire line. By the middle of the 1980s, a fundamental reconstruction of the entire production cycle (the rebuilding of individual mills or even whole shops, since the problem of further reducing energy, labor, and material costs was not being resolved) was needed at large metallurgical combines with an annual production of 4 million tons or more. However, such reconstruction required an enormous amount of money.

Vibrations and Surface Generation in Slab Milling

In slab milling the quality of the machined surface is directly influenced by the dynamic behaviour of the machine tool. In addition to the cycloidical microgrooves, the dynamic relative motion between the workpiece and tool is superimposed on the machined surface. In general these vibrations cannot be directly identified by investigating the machined surface. By the application of a special purpose milling cutter, microgrooves are generated which are identifiable and from which the relative motions in the cutting zone can be determined by surface topography measurement. It is shown how the groove structure is produced as a function of the kinematics of the process and the relative motions in the zone of cutting. An example based on experimental investigation is used to illustrate the procedure used to determine these relative motions based on analysis of the workpiece surface.

Lipid Oxidation of Edible Peanut Pastes during Storage with Variation of Environmental and Processing Factors1,2

Abstract Storage studies were performed for a period of 127 days to evaluate factors of processing and storage environments affecting rancidity development of peanut paste. Factors of milling (stone slab or plate-type attrition mill), ethylenediaminetetraacetic acid (none or with 100 ppm EDTA additions), oxygen (vacuum or atmospheric packaging), light (dark or fluorescent illumination) and temperature (4C or 45C) were incorporated into a 2(5–1) fractional-factorial design. Rancidity developments were monitored using thiobarbituric acid reactive substances (TBARS) number and peroxide values. Initially dominant, the positive effect of oxygen on peroxidation was subsequently outpaced by the effect of temperature. Throughout the study, the effect of temperature on peroxidation levels was consistently positive and statistically significant. Significant positive interactions of the two effects continued from the second week to the end of the first month and a late appearance of negative interactions between light and temperature were noted. Elevated levels of TBARS were shown after 8 weeks without consistent association to the particular design factors.

Modelling of the interaction of slabbing mills during the simultaneous rolling of slabs in both roll-pairs

During the simultaneous rolling of one slab in both roll-pairs (horizontal and vertical) of a slabbing mill, there occurs the development of various vibrations in each drive. Rolling is possible only under the condition of change in the positions of the neutral points on the arcs of contact. The result of a change in the distance between these neutral points is an apparent change in the length of the metal between the horizontal and vertical rolls, and thus an apparent change in the coefficient of elasticity of the metal between the two stands. On this basis a method has been adopted for the modelling of the interaction between two continuous rolling mills, designed for the rolling of a rigid charge (i.e. of a large cross-section such as a slab, a bloom, a plate, etc.).

Optimizing the schedule for ingot transfer from the open-hearth shop to the slabbing mill

Optimizing the schedule for ingot transfer from the open-hearth shop to the slabbing mill

Improvement in the technology for the production of steel for tin plate

In connection with the startup of the tin plate shop at the Karaganda combine, the combine has become the first facility in the sector to master the production of tin plate from steel 08kp. The steel is made in 300-ton converters and teemed into 16.3-ton ingots. The first stage of the technology provides for deoxidation of the steel in the ladle with ferromanganese ladle injection of the steel with argon, teeming from a 300-ton ladle through a slide gate with an 80-mm-diameter channel, and blocking of the ingots with cast-iron caps after the metal has rimmed in the ingot molds for 8-15 min. It was established that the optimum temperatures for the metal are 1540-1550~ before teeming and 1550-1560 before nitrogen injection. When the temperature of the steel is higher than 1560~ it is cooled with a slab before injection at a rate of 1.0-1.5 deg C/min. The optimum degree of oxidation of the steel in the mold is 0.03-0.04%, with the finishea steel having a manganese content of 0~ When the metal is insufficiently oxidized prior to teeming, a rimming intensifier is added to the mold in the amount 150o300 g/tono The intensifier is in the form of granules of ferric oxide from pickling solutions from hot-rolled sheet production and potash or soda. Several problems with the tin plate production practice were discovered during its introduction: a high incidence of inferior-quality metal at the slabbing mill due to surface defects, mainly seams and cracks; a large number of strip tears on the 1400 mill in the tin plate shop. To alleviate these problems, the combine conducted a study to improve the tin plate technology. The principal means of making the improvement were: a reduction in the linear teeming rate through the use of two slide gates with 60-mm-diameter channels; teeming into new ingot molds with more inclined sides; blocking the ingots with lump aluminum after the metal has rimmed in the mold long enough to form a solid skin 50-90 mm thick. While studying the teeming of heats through two slide gates with 60-mm orifices, we refined the duration of teeming and steel temperature and recorded the number of deviations and the instances of reclassification of the metal into other grades. The optimum teeming temperature was determined to be 1540-1550~ i.eo, the same as in the case of teeming through a single slide gate with an 80-mm orifice. Teeming time through two 60-mm slide gates was shortened by 3 min from the time taken in the case of one 80-mm gate (Table I). The time required to fill one ingot mold increased 1 min, while the frequency of deviations decreased from ii.i to 4.8%. This in turn led to a 2.0% reduction in the number of reclassified ingots. Useable output on the slabbing mill increased by 6.9%, while the amount of crop necessary was cut in half. Useable output increased partly as a result of a reduction in the amount of metal reject6 for seams and cracks from 3.0 to 0.7% and from 4ol to 0.3%, respectively. This result was achieved thanks to an increase in the minimum thickness of the dense ingot skin from 8 to 11-12 mm after the linear rate of filling of the mold was decreased and the teeming temperature was optimized. To reduce surface defects on the slabbing mill, we tested and introduced a new type of ingot mold, 16N, for 16.3-ton ingots. The conicity of the inside faces of the mold is 2% greater than on the previous molds. The new mold also has narrow wavy and broad curved faces. Model-17ST ingot molds were used earlier to teem ingots of the same size. These molds had inside faces with a 1.15-1.35% inclination and a smooth surface.

Dynamic torque variation in the drive of a large slabbing mill

The drives of slabbing mills are exposed to numerous failures during operation; the cracking of flat ends of rolls and universal mill couplings are the most frequent cases. The causes of these failures are not always easy to determine, as they may arise from the effects of at least several factors, such as: (i) excessive static loads caused either by operator error when determining the draft, or by the rolling of insufficiently heated slabs; (ii) high values of dynamic loads caused by torsial vibrations of the system; (iii) material fatique of particular elements of the drive. In the present paper the author was concerned with determining the factors promoting torsional vibrations in the drives of slabbing mills. For this purpose the results of measurements carried out under industrial conditions were employed. A slabbing mill with ø 1150 mm horizontal rolls and with one pair of vertical rolls of ø 900 mm was the subject of investigation. Dynamic loads in the horizontal and vertical roll drives were included in the measurements. By this means the basis of the primary factors influencing the nature of vibrations in these drives has been determined. It has been established that the nature and the magnitude of the dynamic torques in the couplings is directed related to the standard practice used for the process and to the method of operation of the slabbing mill. The highest dynamic loads in the horizontal system occur mainly during the bite. The resonant vibrations caused by slip of the rolls, in the case of unsuitably chosen conditions of bite, are particulary dangerous. Factors connected with simultaneous rolling of the slab in two pairs of rolls are a frequent source of vibrations of the driving systems. This is clearly seen, in particular in the drive of the vertical rolls. By analyzing the causes of the occurrence of the loads under obszervation, the conditions for efficient operation of the rolling mill have been defined. The most important are: ensuring that the bite occurs during the period of acceleration of the rolls; careful selection of the drafts; and maintaining the correct synchronization of the peripheral speed of the horizontal and vertical rolls. It is not recommended to use passes with very small drafts - δ h ≤ 5 mm - in the vertical stand. It is expected that observance, in practice, of the conditions mentioned above will afford very real prospects of lowering the number of cycles of load variation in the rolling-mill driving-system and will lead to an increased life for the elements of the latter.

Development of Hot Slab Surface Defect Detecting Device

Nippon Steel developed a high-accuracy hot slab surface defect detecting device utilizing the high resolving power of photographs as a means of quality assurance in the hot charge rolling and hot direct rolling processes. The first device was installed in the slabbing mill at Muroran Works. It performs the photographing of slab surfaces automatically and at high speed to present inspection images of slab surfaces to the inspector. In addition to serving for quality assurance, this device contributes largely to yield improvement by giving instructions on the amount of scarfing to the hot scarfcr and quality improvement by quickly feeding back information on defects to the steelmaking process.

Algorithms for On-line Computer Control of Steel Ingot Processing

A substantial proportion of steel production is provided in cast ingot form. These ingots are reheated in a soaking pit furnace to provide metallurgically acceptable conditions for the subsequent slabbing process. Substantial savings in processing cost can be realized as a direct consequence of efficient scheduling between successive operations. Efficiency is improved by appropriately choosing from a limited inventory of ingots of known thermal history, and by charging, and firing the furnaces according to strategies which can satisfy the slab mill demand while minimizing cost. An on-line model of ingot thermal behavior has been developed to provide estimates of thermal profile and heat content at each processing stage between teeming and slabbing. This algorithm provides a consistent basis for ranking the utility of various processing options for meeting slab mill demand.Once the charging decision has been made and firing has commenced, it is necessary to monitor and control the reheating process to meet actual demand. An on-line calculation of the thermal state is used to project ingot thermal profiles since these cannot usually be measured directly. The furnace set-point can be modified to insure that the ingots achieve the soaked condition as required by slabbing demand. This paper describes a compact, on-line interactive control algorithm using a suboptimal but practical firing strategy which minimizes fuel cost and slab mill delay.

Optimal decisions for scheduling of ingot processes

The scheduling problem of ingot processing from teeming to the slab mill has been studied to determine a sequence of optimal decisions. A deterministic mathematical model in the framework of linear programming (LP) is derived based on a material balance. The input sequence consisting of symbols assigned to the ingots on the track and the heat production of the melt shop is rearranged in the model equations in the order of their arrival at the soaking pit track by considering their fastest possible travel time. The sequence of the generation of empty pits calculated in the model describe the pit availability constraints. The cost related to the possible matching of these two sequences is optimized relative to the objective of ingot processing. An LP solution can be proved to be integer valued. Most practical constraints which arise in the ingot processing, such as breakdowns of one or more individual units can be handled within the formulation. An example problem is presented to demonstrate the practicality of the approach.

Relationships of the roll speeds of the universal stand of a slabbing mill

Relationships of the roll speeds of the universal stand of a slabbing mill