89 / 96
www.read-tpt.com
J
anuary
2015
87
Shandong SiFang Technical Development Co Ltd
Article
New material development and
manufacture of crimping dies in
UOE welded pipe plant
By Li Xin-wen, Zhou Gui-de, Li Jian-xin and Su Qi-shuang from Baoshan Iron & Steel Co Ltd, Shanghai, China
and Shandong SiFang Technical Development Co Ltd, Jinan, Shandong, China
1 Introduction of crimping press
Crimping is one of the major processes of a LSAW (longitudi-
nally submerged arc welding) steel pipe production line, which
results in the bending deformation of both plate sides; after
crimping, both sides become the arc of the curvature radius
close to the finished pipe radius in order to ensure geometrical
dimensional accuracy of the pipe welding seam area.
There has been no crimping process in the early LSAW pipe
production line, such as the world’s first industrial production
line of UOE welded pipe in McKeesport, USA, in 1951. The
second generation of UOE welded pipe mills were built from
1955 to 1967, and a portion of a total of 18 sets of new mills
and one set of reconstructive mill have adopted roller-type
crimping presses. The third generation of UOE mills appeared
between 1968 and 1979, during when the crimping process
developed dramatically from roller-type to die-type, and in total
there are 16 sets of new mills put in use and two sets of old
ones reconstructed all over the world. Since the 1990s, there
have been more than ten large diameter JCO (including PFP)
or RB production lines constructed in the world, of which JCO
lines have adopted the die-type crimping process.
This article introduces the function of the crimping
processing, the technical development and the structure
of the crimping press at first; then narrates the status
in active service of the crimping die, its critical quality
requirements and also its manufacture technical difficulty.
The material and the corresponding manufacture
process, which meet the requirements of the crimping
processing, have been developed through the
characteristics analysis of the former German dies,
such as chemical composition, surface hardness and
geometry size.
After manufacture completion of the new dies, the
testing results show that there are no remarkable
differences in surface hardness, tensile strength and
impact toughness between new dies and former German
dies; after volume production experiment of welded
pipes, there are scarcely any quality defects in the new
dies by offline inspection.
Field practice experience and numerical simulation results
demonstrate that during the UOE process, if there were no
crimping process, both plate margins of about 300mm width
(both sides of the welding seam after O-forming) would be
difficult to improve significantly even after compression ratio
2 per cent of O press and expansion ratio 3 per cent of
expanding machine, resulting in the difficulties of pre-welding
process adjustment, burning through of submerged arc
welding, cold cracking of expanding process and pipe defect
peaks from normal pipe contour. In JCO (including PFP)
processing method, if there were no crimping process, pipe
defect peaks from normal pipe contour would be more serious
than that in UOE processing.
As can be seen from the development of crimping technology,
a roller-type crimping process has been used in the early
crimping technology, which is generally used for thin steel
plates but it does not have an ideal effect on high strength
plate due to the longitudinal extending of plate margins. The
die-type crimping process has been the advanced technology
developed for thick plates, in which two presses of thousands
of tons force crimp plates step by step by pushing both plate
margins upwards with dies of several metres long at the same
time. Desirable shape of the plate margins induced by the
process prevents cold cracking of expanding process and
Figure 1: Structure schematic diagram of crimping press
Roller-type crimping press
Die-type crimping press