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There are two types of rolling. With hot rolling, heated metal goes through a rolling machine where it is worked into a sheet or bar. With cold rolling, sheet steel is made thinner at normal temperatures, and its surface is made smooth and uniform. Tsubaki products are used in both hot and cold rolling.
Tsubaki chains are used in important areas, such as opening/closing heating furnace doors. In addition to trusted, proven heavy duty chains, RF chains play an active role as they are compatible with heavy duty chains and proven in many applications.
Chains for use with conveyors for conveying semi-finished products such as slabs and billets should be designed by considering the shape, temperature, and conveying atmosphere of the objects to be conveyed. Tsubaki proposes optimum specifications based on its wealth of experience.
Tsubaki Toughrollers are ideal for moving, transferring, and conveying heavy objects. The rollers have a low center of gravity and are compact and highly circular, enabling conveyance of heavy objects with little force.
Tsubaki Pin Gear Drive Units play an active role in moving steel rolling trolleys. They allow for long strokes not possible with hydraulic cylinders and contribute to space savings. The pin rack is built as a unit of a given length. Use of the angle type allows for easy installation and tooth engagement adjustment.
Tsubaki Troi Drive, which uses a compact, double-enveloping worm gear is ideal for rolling machines. Designed with an efficiency-focused optimum tooth shape, the Troi Drive provides high efficiency operation. The large number of teeth that simultaneously mesh reduces uneven rotation.
Tsubakis lineup of jacks consists of three types: trapezoidal screw, ball screw, and high-lead ball screw. Trapezoidal screws include a stainless steel type and a left-hand screw type as standard. That's why Tsubaki jacks are available with short delivery times for various layouts and environments.
In surface treatment lines such as CAL and CGL, when the seams between coils on the inlet side are welded or the coiled steel on the outlet side is cut for continuous surface processing, or when flow is intermittent, the looper tower carriage is raised and accumulated steel sheets are smoothly fed. Tsubakis trusted, proven G8 Series Heavy Duty Drive Chain is used successfully for raising the carriage.
Various models are available: Heavy Duty Chain (RS-HT) offers enhanced tensile strength thanks to increased plate thickness over RS Roller Chain; Super Chain offers enhanced maximum allowable load (transmission capacity); and Super-H Chain using the same profile as Super Chain provides substantial improvements in both tensile strength and maximum allowable load by increasing plate thickness.
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Alligatoring in strip rolling, in which the central plane of the strip in the thickness direction of the strip fractures during rolling and the front end of the strip splits into two parts along the central plane of the strip like the jaws of an alligator, is one of the fractures in rolling. Alligatoring is also called crocodiling. Alligatoring in strip rolling is known to occur in hot rolling and in materials of limited ductility such as aluminummagnesium alloys. Although alligatoring in strip rolling was often observed in industrial rolling mills (Kasz and Varley, 1949), few researches on alligatoring in strip rolling were performed in laboratory rolling mills.
Schey (1966) obtained not only the experimental result on edge cracking in strip rolling but also the experimental result on alligatoring in strip rolling. An aluminummagnesium alloy containing 8% Mg was used, and alligatoring in strip rolling was observed when the (strip thickness)/(length of contact) ratio was equal to 0.66. A photograph of alligatoring in strip rolling was shown in Schey (1980). Although alligatoring in strip rolling was mentioned to be related to the (strip thickness)/(length of contact) ratio, further researches on alligatoring in strip rolling are required because of limited experimental results.
A discussion of the homogeneous compression assumption is also necessary here. This phenomenon has been studied experimentally by visio-plasticity methods in addition to observing the deformation of pins inserted into the rolled metal. Figure 4.4 shows in part (A) that the originally straight lines bend, while in (B) they do not and the original planes remain planes.
In the second case, the compression of the strip during the rolling pass is referred to as homogeneous compression. Schey (2000) differentiates between the two possibilities, depending on the magnitude of the ratio of the average strip thickness in the pass, have=0.5(hentry+hexit), and the length of the contact, L=Rh, where R is the radius of the flattened but still circular work roll (this idea will be discussed later, in Chapter 5, dealing with mathematical modelling of the process) and h=hentryhexit, of course. When have/L is larger than unity the deformation in inhomogeneous and the originally straight planes bend as shown in Figure 4.4A. When the ratio is under unity, the effects of friction on the rolling forces and torques are significant and the homogeneous compression assumption may be made with confidence.
When strip rolling is discussed, whether hot or cold, the planes remain planes assumption is very close to reality, with one possible exception. This concerns metal flow in the first few passes of the slab through the roughing train of a hot strip mill where the strip thickness is in the order of 200300mm and the work rolls maybe 1m or more in diameter, leading to a roll diameter/strip thickness ratio in the order of 35. In the finishing train this ratio increases by at least an order of magnitude and the plane-strain assumption becomes acceptable. Venter and Adb-Rabbo (1980) examined the effect of Orowans (1943) inhomogeneity parameter on the stress distribution in the rolled metal. They concluded that the effect is more significant when sticking friction is considered to exist, compared to sliding friction6. The distributions of the roll pressure, with or without the inhomogeneity parameter differed by about 10%.
Some further consideration of the term the width doesnt change by much is necessary here, in light of a recent publication by Sheppard and Duan (2002) who used FORGE3 V3, a three-dimensional, implicit, thermomechanically coupled, commercially available finite-element programme to analyse spread during hot rolling of aluminium slabs. While the authors predictions correspond to experimental and industrial data very well, the slabs they examined cannot be considered to behave according to the plane-strain assumption. In their study the slabs measure 25mm width and 25mm entry thickness, rolled using a roll diameter of 250mm. In the industrial example, the measurements are 1129mm width and 228mm entry thickness. The roll diameter is 678mm. In both cases lateral spread, measured and calculated, is shown to be considerable. When one considers strip rolling, however, in which case the roll diameter to entry thickness ratio is large in comparison to unity in addition to the width/thickness ratio also being large, homogeneous compression planes remaining planes during the pass as well as the assumption of plane-strain flow are quite close to the actual events. In what follows, both assumptions will be made without any further reference. Further simplifications and assumptions will be detailed and discussed in Chapter 5, dealing with the details of mathematical modelling of the flat rolling process.
where N is the total energy dissipation rate, ij represents stress tensor, ij represents strainrate tensor, V represents volume, vs is the relative slipping velocity, v0x and vcx are the velocities on the entry and exit planes respectively, is friction factor, p is unit rolling pressure, 0 and 1 are the front and back tension stresses respectively, s1, s2, and s3 are, respectively, the surfaces on which the frictional force, front and back tensions act. The deformation zone model with the consideration of the noncontact deformation zone at the entry side and the elastic recovering zone at the exit side is illustrated in Fig. 1. The longitudial gauge distribution model can be derived from the continuous and smooth conditions in the whole deformation zone. It may be expressed as follows;
where Cr is the factor related to the length of the non contact deformation zone obtained from the energy principle or given by virtue of experience, H represents the gauge on the entry plane (it is a function of y coordinate), h1 is the roll profile (it is a function of y coordinate), 1 is the projected length of the roll bite without considering the noncontact deformation zone and the elastic recovering zoneo
In the deformation zone, the main unknown displacement function is the transverse displacement function w(x, y). In order to reduce unknown parameters, it is simplified into the product of a known function in the longitudinal direction and an unknown function in the transverse direction, as follows.
The distributions of stresses and volume strain can be obtained by solving the constitutive equations and formula (14). Because the stressstrain relation in each deformation zone is different, it will be discussed seperately.
where H' is the the hardening factor of the material, 'ij, 'kl are the partial stress tensors, ij is the stress rate tensor and ef is the effective stress. With the stress on the elasticplastic common border plane as the initial value, x, y, z and v can be derived from expressions (14) and (17) by numerical method.
Taking the points where unloading process begins as the initial points, x can be obtained by solving equation (21) using numerical method, then y, z and v may be derived from formula (20). Furthermore, x, y and z can also be abtained from formula (18). The solution process extends from the initial points to the exit side. As soon as the calculated z satisfies z = 0, the unloading process ends. At this time, x is the residual stress which we have been searching for.
In hot strip rolling, a slab, usually a steel stock heated above the recrystallization temperature, is passed through the roll gap several times, with the gap being progressively reduced to achieve the desired final dimensions. Mill designers and operators are keenly interested in proper design and control of the hot strip rolling precess. The specific goals to be achieved by process design and control may vary depending on the need of the manufacturers and customers, but product quality as well as production economy is a fundamental consideration in most cases.
Information on metal flow in hot strip rolling is vital for optimization of the quality of the rolled product, since plastic flow can induce phase transformations and alterations in grain structures which can markedly affect mechanical properties of the material. Therfore, developing a method of analysis capable of predicting the effect of various process parameters on metal flow characteristics is essential.
In recent years, the finite element based computer simulation techniques have been proven to be an effective tool for predicting detailed aspects of metal flow as well as roll force and roll torque in rolling. Some of related works may be found in the references. Recently, a penalty rigid-visco plastic finite element formulation was proposed by Hwang et al. . It was shown that roll pressure as well as tangential stresses at the roll-strip interface can be accurately predicted by the penalty algorithm for the Coulomb friction model.
Metal flow is influenced by the temperature distributions in the strip, since the flow stress exhibits strong dependence on temperatures. On the order hand, the temperature distributions in the strip are affected by the heat generation due to plastic flow and friction at the roll-strip interface, by the velocity field in the strip, and by the heat loss to the roll, indicating strong correlations between the metal flow characteristics and thermal behavior of the roll-strip system. The heat transferred from the strip to the roll produces high surface temperatures while the bulk temperature of the roll is little affected, resulting in thermal stresses in the thin surface layer of the roll. Thus, proper control of the process parameters affecting the roll temperature is not only important in controlling the metal flow but also in keeping the thermal stress level in the roll within the allowable range.
In this paper, we introduce a new approach for the determination of metal flow, roll pressure, and temperatures in hot strip rolling. The approach is based on the finite element method and capable of dealing with the coupled problem of metal flow, heat transfer in the strip, and heat transfer in the roll, in a rigorous manner. In the approach, a rigid-viscoplastic finite element formulation described in the reference  employed for the metal flow analysis. For the analysis of heat transfer, we present a Petrov-Galerkin finite element formulation. Then, an iterative method for calculating the coupled solutions of velocity field in the strip, temperature field in the strip, and temperature field in the roll is introduced. Using the approach, a series of process simulations are carried out to investigate the effect of various process parameters on the thermal behavior of the roll-strip system and on the flow behavior in the roll gap.
In the theory of strip rolling based on plain strain deformation the lateral deformation of metal is not considered, and the transverse distributions of the rolling pressure and the front and back tension stresses which are related to the flatness of rolled strip can not be analysed. There is a need for the study of the 3dimensional deformation theory of metal to simulate the strip rolling process. For more than ten years, people have put forward a number of methods simulating the 3dimensional deformations of sheet and strip rolling. The main methods of are the 3dimensional finite difference method , and the 3dimensional finite element method. At present, the above mentioned methods have been used to analysed the rolling processes of small width/thickness of sheet or strip only. There have been very few comparisions of the computed results of the transverse distributions of the 2directional friction stresses and the front and back tension stresses with the experimental ones.
In order to overcome the shortcoming of a great deal of computation and the difficulty of solving the problem of large width/thickness, this paper puts forward a third Bspline finite strip method to simulate the cold strip rolling. For the cases of small width/thickness and large width/thickness, the computed results agree with the experimental results well.
The concept for shear strip rolling arose from work related to the thermomechanical processing of directly cast strip steels. While some studies of direct rolling from a laboratory strip caster were performed, most of the work involved reheating thin 2mm strip to produce a large austenite grain size followed by hot rolling. In these experiments the effect of temperature was considered at it was found that the large austenite grain size substantially reduced the Ar3 relative to the Ae3 and hence it was possible to roll at high undercoolings. This was accentuated by the quenching effect of the cold rolls. The overall effect of this (Hodgson et al., 1998) was that an ultrafine grained ferrite surface layer was formed on both the top and bottom surfaces of the strip while the centre of the strip formed much coarser ferrite (Fig.15.4). This result on the surface contradicted all views related to ferrite refinement: one pass, instead of heavy accumulated deformation, and air cooling after rolling, rather than intense quenching.
Further investigation (Hodgson et al., 1999) showed that the key factors were the high level of undercooling combined with a shear zone caused by friction between the thin strip and the work roll. In other experiments (Hickson and Hodgson, 1999) the strip was rolled with the work rolls closed and an intense water curtain directed into the roll gap. As the strip was rolled it was then instantaneously quenched on the exit side of the rolls. This produced a different layered structure, in this case an ultrafine ferrite on the surface and a quenched martensite core, suggesting that the ferrite formed dynamically during the very short time in the roll gap.
A wide range of steel compositions was then tested and a common picture emerged of this layered structure, with relatively little difference in the ferrite grain size in the surface layer (Hickson et al., 1999). Finally, a model Fe-Ni alloy (discussed later) was used to show the nature of the deformation structure in the austenite. The centre of the strip consisted of conventional relatively low angle microbands. There was then a transition zone, while the surface layer consisted of high angle cells and evidence of a very complex deformed structure due to the high shear. It was proposed that these regions could be suitable nucleation sites (Hurley et al., 2001), which, combined with the high undercooling and the rapid quenching, gave full 3D impingement within these zones. Such deformation features are less sensitive to composition which would then explain the relatively constant grain size in the sheared zone. However, this process offered little control and also could not produce a fully transformed ultrafine strip, and so most work since has focused on more conventional deformation processes.
The parameters of the cold strip rolling process were measured and calculated, using an advanced finite element model. Elasticplastic deformation of the rolled strip was taken into account. Two approaches were followed: in the first, the roll was assumed to remain rigid, while in the second, its elastic deformation was considered. The coefficient of friction was expressed as a function of the relative velocity between the roll and the rolled strip. In each calculation it was chosen such that the difference between the measurements and the calculations was minimized.
The coefficient of friction dropped as the rolling speed was increased. As well, while the roll forces were determined accurately by using either rigid or elastic rolls, the accuracy of the roll torque computations increased when the elastic deformation of the rolls and the elasticplastic deformation of the strip were accounted for.
Pipe can be manufactured by rolling strip or plate and then welding the seam. Nominal diameters between 20 and 1000 mm, to 40 nb, with wall thicknesses up to 55 mm, 2.165, are regularly produced. Manufacturing can be accomplished in two ways so either a single longitudinal straight weld is formed or a spiral weld is produced. Both methods can produce a high integrity product depending on the welding method and the quality controls implemented. Welding can be: manual arc, submerged arc, MAG, SMAW with coated electrodes, tungsten inert gas (TIG), plasma, LASER or electron beam. Weld beads can be dressed. After welding, the pipe lengths can be heat treated to remove welding residual stresses, adjust the molecular structure in the heat-affected-zone (HAZ) or modify the physical properties of all the material. Typical heat treatments include annealing, solution annealing and tempering. Pipes can be finished by descaling or pickling. The integrity of the weld can be checked by ultrasonic examination or real-time radiography. Final inspection checks include air leak testing under water and hydrostatic testing. Hydrostatic testing can be combined with cold-forming to improve circularity.
This chapter presents the simulation of micro ultrathin strip rolling. The rolling deformation characteristics of foil have been theoretically analyzed. A 2D elastoplastic finite model is established to investigate the roll bite behavior in cold foil rolling process. Contact pressure distribution and roll contour in roll bite are also presented, which demonstrate that foil rolling process is different from conventional strip rolling process. The contact area is composed of five zones which are same as the results of Fleck foil rolling theory. The effect of rolling parameters, such as coefficient of friction, entry thickness and reduction rate on distribution of contact pressure, and vertical displacement are also discussed. Asymmetrical rolling technology is helpful to produce ultrathin products by reducing the rolling force and improving the pass-reduction limit due to cross-shear deformation zone. Numerical investigation on the micro asymmetrical rolling process for ultrathin strip has been conducted. The analysis of surface roughness evolution with rolling conditions has also been investigated, and the effect of speed ratio in rolling has been identified.
Preet & our associates (Engineering Companies) has designed, manufactured and successfully delivered Semi Continuous narrow Hot Strip Mill. Semi Continuous Hot Strip Mill which incorporates the latest proven technology and know-how available in the steel industry. Our experienced team of engineers and design has offered modern solutions that perfectly match the demands of the market. The specifications are mainly based on the capacity requirement. However, careful analysis of the production strategies as well current technology innovations and future trends in the steel industry are also equally considered. Additionally, local factors and constraints also played important role in the design of the plant and selection of the equipment.
The design of the plant is flexible and has been studied to ensure: Easy handling | High productivity | High quality of final products | Low specific consumption | Simple maintenance. On the basis of this and with a low initial investment joint to reduce transformation cost, its possible to have a short time lag between investment and payback. Preet can also support with the following Optional Services on a special request of the buyer, commercial offer of these services can be submitted after freezing the scope: Master Layout Engineering Services. Civil Engineering Services. Structural and Building Engineering Services. Utility Engineering Services. Site Erection Supervision/ Implementation Services. Plant Commissioning Supervision/ Implementation Services.
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