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Flexibility and utilization of roll pass sequences in some Swedish wire rod mills
KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
2005 (English)In: Steel Research International, ISSN 1611-3683, Vol. 76, no 9, 635-643 p.Article in journal (Refereed) Published
Abstract [en]

A computer program has been developed to calculate the working range for series of two-symmetrical grooves including oval, round, false round, square and diamond shapes. Eight different pass designs are compared. The geometry of rolling or entry bar height over roll radius is in the range 0.09-0.26 for squares, 0.10-0.23 for false round and 0.06-0.21 for ovals. Square-oval and round-oval have similar flexibility, but in the round-oval sequence, the flexibility can be extended by opening up the gaps and run the rounds as false rounds. In the square-oval sequence the flexibility can be improved by making the squares with larger corner radii but the reduction capability will be reduced. The false round-oval sequence has the best flexibility and the working range can be extended by making "flatter" ovals. Improvement of the roll pass design in Fagersta Stainless AB has made it possible to roll wire rod with higher flexibility and better quality.

Place, publisher, year, edition, pages
2005. Vol. 76, no 9, 635-643 p.
Keyword [en]
Flexibility, Roll pass design, Swedish mills, Wire rods, Working range
National Category
Materials Engineering
URN: urn:nbn:se:kth:diva-8841ISI: 000232488400004ScopusID: 2-s2.0-25444499707OAI: diva2:14304
Available from: 2004-11-30 Created: 2004-11-30 Last updated: 2011-08-31Bibliographically approved
In thesis
1. Roll pass design for improved flexibility and quality in wire rod rolling
Open this publication in new window or tab >>Roll pass design for improved flexibility and quality in wire rod rolling
2004 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The thesis treats roll pass design in wire rod rolling of stainless steel for sequences and series built up by two-symmetrical grooves. It is focused on predicting rolling flexibility, also called working range, as well as product quality. For analysing the flexibility a computer program has been developed. The minimum and maximum roll gap and corresponding bar areas for series of grooves including "oval", "round", "false round", "square" and "diamond" shapes are calculated. Six pass designs used in Swedish mills are analysed. Full-scale rolling is compared with laboratory experiments for the square-oval and false round (round)-oval series. The false round-oval series offers the largest working range and that the flexibility is smaller for pass sequences designed for high reductions. The false round-oval series are also acknowledged as a series for high quality steels and are usually better than the square-oval series having a tendency for defect formation. The thesis also includes high-speed rolling of wire rod in blocks. Here interstand tensions are utilised in order to keep the process stable. For obtaining the required dimensional tolerances of the product they are kept as low as possible. However interstand tensions could be used in order to increase the working range and move the product range towards smaller wire cross sections. For analysing this possibility, a narrow spread technology is utilised. At present time a practical problem is referred to the fixed gearings in the common blocks, which require a certain and given level of interstand tensions and corresponding reductions. This problem can however be solved by means of new block design and modern process control technology. Roll stands can be separately driven and controlled at very high speeds. Thus the eight stand blocks can be subdivided into four plus four passes blocks with a cooling line between enabling also higher productivity without violating the product quality because defect formations caused by a too high rolling temperature. The true working range of a series for a specific steel grade is however not only dependent on the possible spectrum of wire dimensions that can be obtained but might also depend on its ability to decrease or eliminate defects such as surface cracks. Thus, the behaviour of artificial V-shaped cracks in the longitudinal direction has been investigated and compared for the square-oval and false round (round)-oval series mentioned above. In agreement with other research works it was established that efficient rolling conditions for reducing the cracks are obtained when the cracks open up at the same time as their depth is reduced. If the V-shaped crack is closed by contact between its oxidized side surfaces the rolling schedule is not optimal for getting a high quality product. A deeper understanding of the experimental results was obtained by means of an FE-analysis

Place, publisher, year, edition, pages
Stockholm: Industriell produktion, 2004
Trita-IIP, ISSN 1650-1888 ; 04:13
Materials science, wire rod, roll pass design, working range, productivity, swedish wire rod mills, Materialvetenskap
National Category
Materials Engineering
urn:nbn:se:kth:diva-53 (URN)91-628-6232-4 (ISBN)
Public defence
2004-11-19, Sal M311, KTH, Brinellvägen 68, Stockholm, 10:00
Available from: 2004-11-30 Created: 2004-11-30 Last updated: 2012-03-20

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