| 1. |
- Eriksson, Conny, et al.
(author)
-
Working range of roll pass sequences in wire rod rolling with interstand tensions
- 2004
-
In: Ironmaking & steelmaking. - : Informa UK Limited. - 0301-9233 .- 1743-2812. ; 31:1, s. 81-92
-
Journal article (peer-reviewed)abstract
- In the high speed rolling of wire rod in blocks, interstand tensions are utilised in order to keep the process stable. However, interstand tensions influence the rolling process, and especially the spread and forward slip, which are dependent of tensions between the stands. By the influence on spread, the tolerances of the rolled product depend on the tensions and usually the interstand tensions are kept as low as possible in order to obtain required tolerances. A narrow spread technology is used to utilise interstand tensions in order to increase the working range of a pass sequence and move the product range towards smaller sizes. By adapting a certain amount of interstand tensions, smaller sizes can be rolled by a given roll pass schedule. A practical problem in this method is the fixed gearings in the common blocks, which require a certain and given level of interstand tensions and corresponding reductions. In the latest generation of blocks, where the stands are arranged in units, two by two, with each unit driven by a dedicated electrical motor, it is possible to introduce 'inter unit' tensions, and by this method extend the working range of the pass sequence. A special computer program for analysis of interstand tensions has been developed by combining a program TENSION, developed at the Royal Institute of Technology in Stockholm, dealing with the basic principles of rolling with interstand tensions, with the recently published program WORKRAN, which analyses the working range of any roll pass sequence built up by common two-symmetrical grooves. From the analysis and experimental data it is shown that interstand tensions at the level of 10% of the yield stress of the material increase the working range in a six stand block by 2% and reduce the lower limit of the exit section area by about 15%. Higher tension levels have a larger effect both on the extension of the working range and on the reduction of the minimum exit area but it becomes more difficult to control the tolerances at higher tension levels. The influence of interstand tensions on the reduction and on the working range of the pass sequence is mainly obtained by the influence on the round passes, while the oval passes have a counteracting effect on the influence of interstand tensions
|
|
| 2. |
|
|
| 3. |
- Lundberg, Sven-Erik
(author)
-
Evaluation of friction in the hot rolling of steel bars by means of on line forward slip measurements
- 2004
-
In: Scandinavian journal of metallurgy. - : Wiley. - 0371-0459 .- 1600-0692. ; 33:3, s. 129-145
-
Journal article (peer-reviewed)abstract
- In spite of the importance of friction it is still a weak point in the analysis of rolling. Most studies assume that a coefficient of friction (μ) is representative for the roll gap. Forward slip measurements under normal production conditions in a bar mill have been used to evaluate the coefficient of friction, completed by laboratory measurements in a high-temperature test rig, and stability measurements in oval-square and flat-edge oval pass sequences. Coefficients of friction in the range 0.35-0.40 have been evaluated from the forward slip measurements. The rolling speed did not exceed 0.2 m/s and measurements were made in the temperature range 1000-1150°C. No clear influence of temperature on friction could be observed. The stability measurements show similar results. However, no tests have been made at temperatures other than 1000°C, and no influence of temperature on friction can be evaluated. In the high-temperature test rig the influence of temperature on friction is strong at temperatures exceeding 900°C, and probably the mechanism of friction changes in the test rig at higher temperatures, due to the lack of plastic deformation in the contact zone. Further investigations are necessary to formulate a relevant model for friction, valid for the entire range of parameters in a bar or wire rod mill. © Blackwell Publishing, 2004.
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
|
|
| 7. |
- Lundberg, Sven-Erik
(author)
-
Statistical design and evaluation of experiments in steel production
- 2003
-
In: Steel research international. - 1611-3683. ; 74:6, s. 386-395
-
Journal article (peer-reviewed)abstract
- Making experiments under industrial production conditions gives many times difficulties in varying the important parameters in a relevant way in order to significantly influence the process and thus make it possible to measure the result. The common way of varying one parameter at a time, gives rise to many experiments and mostly, large difficulties in the evaluation. The statistical design method, on the other hand, where the parameters are varied systematically and simultaneously, gives possibilities to influence the process in a more efficient way, thus reducing the necessary number of experiments, and at the same time to obtain more reliable results. In spite of the linear approach presented here, it is always possible to evaluate any kind of influence on a process, by choosing the studied parameters in a relevant way. This is simply done by means of a suitable variable transformation before the experimental matrix is set. Analytical evaluation of the experiments often raises a voluminous mathematical treatment of the results. However due to the linearity of the primary functions, the experiments can be evaluated by means of a simplified linear procedure, and even large experimental matrices can easily be evaluated only by means of a simple spread sheet program. By application of the method to industrial problems, a calculation model was developed for the prediction of process parameters for quenching and self tempering of rebar, as a function of requirements and chemical composition of the steel. Alternately the required chemical composition can be predicted when required mechanical properties and quenching parameters are given, or the mechanical properties can be predicted when composition and quenching parameters are given. Another use of the method has been to optimize the finish rolling and coiling temperatures for on line treated high carbon steel wire rod.
|
|
| 8. |
|
|
| 9. |
- Lundberg, Sven-Erik
(author)
-
The "revenge" of the three-high rougher
- 2004
-
In: Stahl und Eisen (1881). - 0340-4803. ; 124:12, s. 141-147
-
Journal article (peer-reviewed)abstract
- Surface defects due to cooling the billet surface in the roll contact in the roughers is a problem in modern wire rod mills. The cooling reduces the ductility and gives rise to defects. Also the heating of the roll surface gives fire cracks in the rolls and bad surface of the rod. The defects can be avoided by making the roughing in reversing stands. For rolling 1 850 kg, 140 mm square billets, the capacity can be 62 to 134 t/h in two-high roughers, and 62 - 167 t/h in three-high roughers. By separating the rolling in an upper and a lower position the space for guides will be improved, and the barrel length can be reduced, giving better tolerances out of the stand. By replacing a worn-out middle roll and shifting the upper and lower rolls, four rolls only make up two roll sets.
|
|
| 10. |
- Lundberg, Sven-Erik
(author)
-
The wire-rod mill of the 21 century
- 2003
-
In: Steel times international. - 0143-7798. ; 27:8, s. 17-20, 26
-
Journal article (other academic/artistic)abstract
- During the past 30 years two conflicting developments have taken place in wire rod production. Steelmaking heats and billet size have grown while the demand on the mill has changed to providing customers with small lots at frequent intervals exhibiting high mechanical and dimensional tolerances. Prof Lundberg shows that larger billet sizes are detrimental to surface finish, this consigning the concept of directly linking caster and mill to low surface quality products. Instead, he advocates melting small 5-25t lots in induction furnaces, decarburising in a tunnel furnace and casting small dimension billet on a wheel caster.
|
|
