2600mm中板矯正機(jī)設(shè)計(jì)【十一輥中厚板矯正機(jī)】【說(shuō)明書+CAD+SOLIDWORKS】
2600mm中板矯正機(jī)設(shè)計(jì)【十一輥中厚板矯正機(jī)】【說(shuō)明書+CAD+SOLIDWORKS】,十一輥中厚板矯正機(jī),說(shuō)明書+CAD+SOLIDWORKS,2600mm中板矯正機(jī)設(shè)計(jì)【十一輥中厚板矯正機(jī)】【說(shuō)明書+CAD+SOLIDWORKS】,mm,妹妹,中板,矯正,改正,設(shè)計(jì),十一,11,厚板
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遼寧科技大學(xué)本科生畢業(yè)設(shè)計(jì)
原文
The Effect of the Number of Leveling Rolls on the Straightening Process
Curvature Analysis
The output of the strain model can be used to formulate a fundamental understanding of the leveling process .A series of simulations was run for 3/8-inch-gauge material with a yield strength of 50 ksi. The simulations were performed for an 11-roll leveler with five top rolls and six bottom rolls, which has 6-inch-diameter rolls spaced on 10-inch center.
Two parameters were varied during the study: the extent of plastic deformation and the magnitude of the initial flatness defects. The model was run for levels of plastic deformation ranging from 20% to more than 90% of the material’s cross-section. For example, a fraction plastically deformed of 0.50 represents a bend that creates yielding in 50% of the cross-section—the outermost 25% at the top and bottom surfaces. The include stresses in the innermost 50% of the cross-section never exceed the yield stress.
For each level of plastification, the model tracks the strain history for each initial condition through every bend in the leveler, and predicts the exiting flatness condition. The exiting flatness condition represents the predicted deviation of the plate from a horizontal flat surface over a 12-foot length, as prescribed in the ASTM A6 standard for plate. The output of the study is shown in Figures 10~13.
Figure 10 shows the manner in which the predicted curvature varies as the extent of plastic deformation changes for material with an initial radius of curvature of 15 inches. This curvature represents the condition of the inside wrap of a coil with a 30-inch inside diameter. Three initial longitudinal flatness condition are simulated: an initial positive radius of curvature of 15 inches (bowed up); an initial negative radius of curvature of 15 inch (bowed down); and an initially flat region. Three initial conditions are included to examine their influence on the exiting flatness prediction. In the analysis of coil processing, the initially flat condition serves as a control condition. However, it is useful in the analysis of discrete plate leveling because the incoming flatness defects vary from one location to another, and a discrete plate generally has some areas that are initially flat.
Figure 10
The model predictions displayed in Figure 10 show that, at low levels of plastic deformation, the three initial conditions result in three distinctly different exiting conditions. The magnitudes of the initial flatness defects are reduced, but they are still large. The initially bowed-up defect exits the leveler with an upward bow of approximately 5.5 inches over a 12-foot length, even when the roll gap of the leveler is set to generate a plastic fraction of only 0.20.The initially bowed-down defect also exits the leveler with curvature in the same direction as the incoming defect(a downward bow),but the magnitude of the defect is reduced to 3.60 inches .The initially flat condition exits the leveler with a defect that is bowed upward almost 1 inch, reflecting the application of the positive bending curvature during the first bend in the leveler, The low level of plastic deformation imparts a positive curvature is retained after the effect of springback .The remaining bends in the leveler do not apply sufficient plastic deformation to reduce the magnitude of the curvature.
As the extent of plastic deformation increases, the predicted exiting flatness defects decrease in magnitude, and the exiting conditions for the three different initial curvatures eventually converge to the same value at a fraction plastic deformation of 0.62.The point beyond which the curves the different incoming conditions identically coincide is termed the convergence point.
The exiting flatness condition displays an oscillatory with plastification rates greater than 50%.The predicted exiting condition is a bow up for plastification rates below 53%.The exiting flatness condition is perfectly flat at a fraction plastic of 0.53, with entry roll gap of the leveler is set to generate plastification rates between 53% and 64%, the predicted exiting flatness condition is a bow down. The maximum predicted bow in 12 feet is 5/8 inch, and occurs at a fraction plastic of 0.58.The exiting flatness condition again crosses the horizontal axis at 0.64, and an upward curvature is produced for settings between 0.64 and 0.75.The maximum bow up is 1.2 inches, which corresponds to a fraction plastic of 0.70.A third crossover point occurs at 0.75,where perfect flatness is again predicted. Downward curvatures are produced between plastification rates of 75% and 85%, with a peak bow of 2.25 inches occurring at 80% plastic deformation. The fourth crossover point occurs at 0.85, and positive curvature results for entry leveler settings corresponding to plastification rates between 85% and 94%.The peak curvature occurs at a fraction plastic of 0.90,and results in a bow of magnitude 6.1 inches. The final crossover point occurs at 0.94, and higher plastification rates produce negative curvatures of increasing magnitude. For example, a roll gap setting that results in a plastification rate of 96% produces a downward bow of 6.2 inches.
The existence of several “zero points” is an underlying reason why successful leveling is achieved in practice, and explains why experienced operators may use very different settings and yet still obtain the same leveling effect for a particular combination of thickness and yield strength.
Figure 11 shows the variation in the predicted exiting flatness condition for the same material when the incoming flatness condition has an initial radius of curvature of 50 inches. This condition represents the outer wraps of a large coil having an outside diameter of 100 inches. The three incoming conditions simulated are an initial positive radius of curvature of 50 inches(bowed up),an initial negative radius of curvature of 50 inches(bowed down),and the initially flat control condition. The modeled results are virtually identical to those for the initial curvature of 15 inches shown in Figure 10.No convergence in the direction of the exiting flatness condition occurs for very low levels of plastic deformation. The predicted exiting defect is exactly identical for the initially flat region（the control conditions）because the same deformation is applies to the same initial condition. The predicted exiting values for both an incoming positive radius of curvature of 50 inches and a negative radius of curvature of 50 inches are slightly smaller in magnitude than those for the 15-inch radius of curvature example, reflecting the less severe initial flatness defect. The same amount of flatness correction applied to a less incoming defect results in an exiting defect of smaller magnitude. The predicted values decrease in magnitude as the three different exiting conditions eventually converge to the exact same value（the convergence point）at a fraction plastic of 0.62.The predicted behavior is identical to the simulated inside wrap for all plastification rates greater than 62%.Crossover points are again seen at fractions plastically deformed of 0.53,0.64,0.75,0.85 and 0.94.
Figure 11
Figure 12 displays the predicted exiting flatness condition for a discrete plate, rather than a coiled product, of the same material processed on the same leveler. The incoming radius of curvature is 1000 inches, which simulates an initial bow up of 2.60 inches in 12 feet, a bow down of 2.60 inches and an initially flat region. This range of flatness defect is typical of a heat treated plate. The modeled results are generally similar to those for the coiled condition simulations. However, several major differences can be noted between the coiled and discrete simulations：
Figure 12
The magnitude of the exiting flatness prediction is markedly smaller at very low levels of plastic deformation and is positive (bowed up) for all incoming conditions. The initial 2.60-inch bowed-up defect is reduced to 1.74 inches, and the initially bowed-down defect exits as a 0.28-inch upward bow, even when only 20% of the plate’s cross-section is plastically deformed. The positive curvature applied during the first bend reverses the incoming curvature from bowed down to bowed up.
The variation in the predicted exiting flatness condition is significantly reduced for the less severe initial condition. The range of exiting out-of-flat conditions for the plate at a fraction plastically deformed of 0.20 is from 0.28 to 1.74 inches, compared to range of -3.60 to 5.46 inches for the inside wrap of a coil processed at the same leveler settings.
The predicted exiting flatness value is less than 0.50 inch in magnitude for plastification rates between 36% and 54%.
The convergence point also occurs at significantly reduced levels of plastic deformation for the plate simulation (0.48) compared to the coiled product (0.62), and the oscillatory behavior begins earlier, at a fraction plastically deformed of 0.40.
The predicted behavior is identical to the simulated coiled conditions for all plastification rates greater than 62%, and crossover points occur at the same locations (0.53, 0.64, 0.75, 0.85 and 0.94).
Figure 13 shows the variation in the predicted exiting flatness condition for 3/8-inch-gauge discrete plate when the incoming flatness condition has an initial radius of curvature of 2000 inches. This condition simulates even smaller incoming defects, including an initial bow up of 1.30 inches, a bow down of 1.30 inches and an initially flat region. The magnitude of these flatness defects is typical of the distortion seen in an as-rolled and air-cooled distortions plate. The predicted exiting flatness conditions at low plastification rates for this case are very small, are all bowed upward, and show little variation between the three different incoming conditions. The initial 1.30-inch bowed-up defect is increase to 1.37 inches at 20% plastification because the applied curvature, but this value is smaller in magnitude than the similar exiting defect for the 1000-inch radius of curvature (1.74 inches).The initially bowed-down defect exits as a0.62-inch upward bow, large in magnitude than the initial 1000-inch curvature (0.28 inch), but close to both of the values for the other initial conditions.
Figure 13
The convergence point is reduced even further (0.46), and the variation between exiting values never exceeds 0.75 inch for the various incoming conditions. The divergent tails of the left end of the curve, which were more than 9 inches apart in Figure 10, are converging to a single line as the incoming flatness defect is reduced. The initially bowed-down condition decreased in magnitude, became positive, and is now approaching the same value with which the initially flat condition exits the leveler (0.99 inch). The initially bowed-up condition also decreased in magnitude as the incoming radius of curvature decreased, and is also converging to the value for the initially flat condition. The predicted behavior is identical to the previous examples for all fractions plastically deformed greater than 0.62, with crossover points at the same five locations. However, as the magnitude of the incoming curvature decreases ,the curve flatness out below 0.62,and the exiting value for a 38% plastification rate approaches zero90.26,0.22 and 0.19 inch for the initially bowed-up, flat and bowed-down conditions, respectively ).
Figures 10-13 show that the predicted exiting flatness can vary significantly below the convergence point. In this region, the severity of the incoming flatness condition has significant influence on the magnitude of the exiting condition. The applied plastic deformation is not sufficient to correct the incoming condition. The predicted flatness above the convergence point is identical for all incoming flatness condition, regardless of their magnitude. The applied curvature exceeds the incoming curvature. The exiting curvature is determined by the bending action of the leveler, not by the severity of the incoming flatness defects.
The results predicted by the model for an 11-roll leveler have been verified by field trials. They have also been verified for both tilting cassette levelers and machines with independent roll adjustment. The model predicts similar results for both different gauges and different yield strengths.
The Effect of Additional Leveler Rolls
The oscillatory behavior displayed in Figures 10-13 can be explained by examining the influence of the individual leveling rolls on the straightening process. Figure 14 shows a schematic of the leveler rolls superimposed on the predicted flatness curve for an incoming flatness defect with an initial radius of curvature of 2000 inches(see Figure 13).The first three-roll triplet, which includes the first top roll of the leveler, controls the exiting flatness for low levels of plastic deformation, in the range of 0.20-0.28.It applies an upward bend to the plate, and the plate exits the leveler with bow in the upward direction, The second three-roll triplet, which includes the first two top rolls and the second roll, influences the exiting flatness in the fraction plastically deformed range of 0.28-0.38.In this range ,the downward bend reduces the magnitude of the exiting upward bow, and the plate exits leveler with an upward bow of reduced magnitude.
Figure 14
The third triplet, consisting of the second top roll and the second and third bottom rolls, controls the exiting flatness when the deformation levels are in the range of 0.38-0.48.The upward curvature imparted to the plate by this bend increase the magnitude of the exiting upward bow.
Setting the entry roll gap to increase the applies deformation to levels above 0.48engages the next downward bend. This bend reduces the magnitude of the exiting upward bow until, at a fraction plastically deformed of 0.53,the plate exits the leveler with perfect flatness. Higher levels of plastic deformation cause the plate to exit with a downward bow of increasing magnitude, until a level of 0.58, corresponding to a downward bow of 0.625 inch. At this point, the next top roll, by is application of a positive bending curvature, reduces the magnitude of the exiting downward bow. Its influence creates the second crossover point at 0.64.Higher levels of plastic deformation cause the plate to exit with a bow up of increasing magnitude, peaking at a value of 1.2 inches at a fraction plastically deformed of 0.70.
The fourth bottom roll, by its application of negative bending curvature, reduces the magnitude of the upward bow, and a third crossover point occurs at a fraction plastically deformed of 0.75.The influence of this roll continues until 2.25 inches, corresponding to a deformation level of 0.80.The fourth top roll controls the exiting curvature from this point, until a fraction plastically deformed level of 0.90,and introduces a fourth crossover point at 0.85.Beyond a plastification of a negative bending curvature, reduces the exiting upward bow and creates a fifth crossover point at 0.94.Higher levels of plastic deformation create a negative exiting curvature of increasing magnitude.
Additional simulations were performed for levelers with a greater number of leveling rolls. The same three incoming flatness conditions were simulated for the same gauge(3/8 inch)and the same yield strength(50 ksi)processed on levelers with identical roll diameters(6 inches)and roll spacing(10 inches).The additional simulations were performed on levelers with 13,15,17 and 19 rolls. The results for the two extreme conditions-the inside wrap of a coil(15-inch initial radius of curvature)and an as-rolled and air-cooled discrete plate(2000-inch initial radius of curvature)-are shown in Figure 15 for the 11-roll leveler(Figures 15a and b),the 15-roll leveler(Figures 15e and f),the 17-roll leveler(Figures 15g and h)and the 19-roll leveler(Figures 15i and j).
Several observations can be made from these simulations and are summarized in Table 1.As the number of leveling rolls increases, the following occurs:
1. The divergence of the left-hand tails of the curves is decreased. The predicted exiting flatness defects are slightly reduced at low levels of plastic deformation.
2. The oscillatory behavior does not begin until higher levels of plastic deformation. The magnitudes of the peaks remain identical, but occur at greater deformation levels. They appear to move to the right of the graphs. For example, the location of the upward bow peak of magnitude 1.2 inches is listed in Table 1. For the 15-inch initial radius of curvature, it moves from a fraction plastically deformed value of 0.70 for the 11-roll leveler to 0.80 for the 15-roll leveler to 0.86 for the 19-roll machine.
3. The convergence point for the three different incoming flatness curves occurs at lower levels of plastic deformation. Convergence occurs for the 15-inch initial radius of curvature at a fraction plastically deformed value of 0.62 for the 11-roll leveler, at 0.52 for the 15-roll leveler, and at 0.50 for the 19-roll machine.
4. The” sweet spot”-the area of relative insensitivity to plastic deformation, or leveler gap settings-is widened. The range for the 11-roll leveler for an incoming radius of curvature of 15 inches is only from a fraction plastically deformed value of 0.50-0.56.It increases to a range of 0.40-0.70 for the 15-roll machine and to 0.38-0.78 for the 19-roll leveler.
Figure 15
Table 1
5. The number of crossover points, or roll gap settings that produce perfect flatness, increases. The number of crossover points equals the number of top leveler rolls. There are five crossover points for the 11-roll leveler, seven for the 15-roll leveler and nine for the 19-roll machine.
Summary
1. A roller leveler straightens material by bending it in both directions via leveler rolls acting together in groups of three.
2. Each additional pair of leveler rolls adds the capability for one additional bend in each direction.
3. The function of take all incoming flatness conditions on the plate, regardless of their direction, and bend them to a bow, or curvature, that is in the same direction. Upon exiting the first bend, all areas have been transformed to one outgoing flatness condition with different magnitudes of severity.
4. The second bend applies a bending action in the opposite direction. Upon exiting the second bend, all incoming flatness defects are uniformly bent to the same curvature.
5. The remaining rolls in the leveler are designed to gradually remove the plate curvature induced by the leveler and deliver a flat product.
6. At low levels of plastic deformation, the incoming flatness defects may be reduced, but they are not eliminated. As the extent of plastic deformation increases, the predicted exiting flatness defects decrease in magnitude, and the exiting conditions for the three different possible initial curvatures eventually converge to the same value. The point beyond which the curves for the different incoming conditions identically coincide is termed the convergence point.
7. The exiting flatness condition displays an oscillatory behavior with plastfication rates greater than the convergence points. This behavior can be explained by the influence of each additional bend in the leveler. As the extent of plastic deformation increases, more leveler rolls apply bending curvature that is sufficient to reduce the magnitude of the flatness condition or to change its direction.
8. The addition of more leveler rolls results in convergence of the various different incoming flatness conditions at lower levels of plastic deformation.
9. The addition of more leveler rolls delays the start of the oscillatory behavior until higher levels of plastic deformation, thus increasing the ”sweet spot” of the leveler, or the range
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