| 摘要 |
PURPOSE:To manufacture a square steel tube of high forming accuracy by supporting a steel plate from the inside not only from the outside and bending at right angles and thereby bending accurately as a standard. CONSTITUTION:Side edges 1A, 1B of the steel plate 1 are bent to make some troughs by a roll 24 having the lower side tapered end and a roll 25 having the upper side tapered. Then, side edges 1A, 1B are bent at right angles by cylindrical rolls 26, 27, 28 and a pair of inside rolls 30, 31 to form the edges into U-shaped sectional form. Then, the central part is folded to a crest shape by a roll 32 having lower side V-projections and a roll 33 having upper side V-grooves, and formed to W-shape in sectional form by a roll 34 having two V-grooves and a roll 35 having a V-groove. Next, both side parts 1D, 1E are erected by a roll 36 having lower side V-shaped projections, a roll 37 having upper side V-grooves, and both sides cylindrical rolls 38, 39. Then, the body of a core is inserted into the nearly square steel plate 1, and at the same time, the folded part is pressed by a pressure roll 44 and a lower-side propping roll 45, formed to square sectional form by both-side cylindrical rolls 46, 37 and upper- side small width rolls 48, 49.
|
