Metal deforming – By use of tool acting during relative rotation between tool... – During rotation of work
Patent
1996-08-27
1998-02-03
Larson, Lowell A.
Metal deforming
By use of tool acting during relative rotation between tool...
During rotation of work
B21B 1904
Patent
active
057132348
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a piercing-rolling method and a piercing-rolling apparatus for seamless tubes, which makes use of inclined rolling mills adopted in the Mannesman tube-making method, a typical method for manufacturing seamless tubes.
BACKGROUND ART
Seamless tubes such as steel seamless tubes are widely used, for example, as steel oil well casings, tubing, and drill pipes, line pipes, steel tubes for heat exchangers, steel tubes for piping, and steel tubes for bearings. Seamless tubes used for such purposes are typically made of carbon steel, low alloy steels containing alloy components such as Cr and Mo, high Cr stainless steels, Ni-based alloy, or titanium. Seamless steel tubes are generally manufactured by the Mannesman-plug mill method or the Mannesman-mandrel mill method. When seamless tubes are manufactured using these methods, the following steps are performed: First, a round bar-shaped billet (hereinafter simply referred to as a billet) is heated in a heating furnace to a predetermined temperature, and the heated billet is pierced using a piercer which is an inclined rolling mill, thereby transforming the billet into a hollow shell. The hollow shell is rolled to elongate by means of a plug mill or a mandrel mill to reduce its wall thickness. Moreover, the outer diameter, among other dimensions, is reduced using a reducing mill such as a sizer or a stretch reducer so as to form a seamless tube having an intended geometry.
The above-mentioned piercer is usually composed of barrel-shaped or cone-shaped main rolls whose center axes are inclined with respect to the pass center of a billet or a hollow shell, a plug serving as an inside restriction tool, and a guide shoe or a disk roll for guiding material to be pierced and rolled (hereinafter simply referred to as a material to be pierced).
FIG. 1 depicts a schematic plan view showing the structure of a piercer which is generally used; FIG. 2 depicts a schematic side view of this piercer; and FIG. 3 depicts a cross section cut along line I--I in FIG. 1. In FIGS. 1 through 3, 10A and 10B are main rolls, and each main roll has a gorge portion 11 of diameter D1 in the middle thereof with respect to the direction of center axis. On the inlet side of the gorge portion 11 (on the left side in FIGS. 1 and 2) there is provided an inlet face 12 having the shape of a truncated cone whose base of smaller diameter defines one end face of the main roll.
On the outlet side of the gorge 11 (on the right side in FIGS. 1 and 2) is provided an outlet face 13 having the shape of a truncated cone whose base of larger diameter defines the other end face of the main roll. The inlet face angle formed by pass line X--X and the inlet face is expressed as .theta. 1, whereas the outlet face angle formed by pass line X--X and the outlet face is expressed as .theta. 2. Thus, each main roll has an overall cone-like shape, and a pair of such rolls are placed in a horizontally or vertically opposing manner, with pass line X--X therebetween.
The center axis of each main roll is three-dimensionally inclined with respect to the pass line. A cross angle .gamma. is determined to be the angle formed by the center axis of a main roll and pass line X--X, as shown in FIG. 1. Also, a feed angle .beta. is determined to be the angle formed by the center axis of a main roll and pass line X--X, as shown in FIG. 2. The paired rolls are arranged in an opposing manner so that the roll spacing Rg at the gorge portion 11 comes to have a predetermined value.
If the cross angle is .gamma. (not zero) and the feed angle .beta. is zero, then the above-mentioned inlet face angle .theta. 1 is equal to the angle formed by pass line X--X and the inlet face 12, and the above-mentioned outlet face angle .theta. 2 is equal to the angle formed by pass line X--X and the outlet face 13.
A plug 2 has a generally bullet-head shape, and is supported at its rear end by the top end of a mandrel bar M connected to a thrust block (omitted in Figures). Plug 2 is held between main rolls 10A an
REFERENCES:
patent: 3719066 (1973-03-01), Okamoto et al.
patent: 4470282 (1984-09-01), Hayashi
patent: 4827750 (1989-05-01), Hayashi
Shimoda Kazuhiro
Yamakawa Tomio
Larson Lowell A.
Sumitomo Metal Industries Ltd.
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