TPT January 2013

100 / 108

98 January 2013
Article
High chromium casting roll for
straightening steel pipe, welding
pipe and cold roll formed steel
By Yuan Houzhi and Liu Xingyi
(Shandong Province SiFang Technical Development Co, Ltd Jinan 250101, China)
1 General
The roll itself is the key component of the mill and the first aim
of a rolling mill is to meet the different standards demanded
in each country. At present in China various rolling mills and
technical equipment levels have been measured that easily
compete with those built around the world and the technical
level of rolling steel now matches the world’s most advanced
levels of machinery.
In recent years China has introduced and constructed an
increasing number of steel pipe production lines that meet
world-class standards and some of the types of lines are not
found anywhere else in the world. Now China’s steel pipe
production industry is one of the largest in the world and as a
result the consumption of rolls is also the largest in the world.
The production of advanced steel pipe mills and high grade
alloy steel pipe make high demands of the roll itself.
Through cooperation and technical innovation the quality
and production process and productivity are continuously
increasing in the roll manufacturing industry in China.
2 Straightening pipe roll, HFW/
ERW welding pipe roll and cold
roll formed steel roll
The material design of rolls is a basic part of machinery design.
The material used for steel pipe straightening rolls, HFW/ERW
New high chromium alloy casting roll researched and
developed by Shandong Province Sifang Technical
Development Co Ltd (SDSF) for straightening steel pipe,
HFW/ERW welding pipe and cold roll formed steel. It can
successfully meet the production requirements of advanced
steel pipe production mills and high grade alloy steel pipe
production lines and the service quality and service life of
that can be comparable to D2, X155CrVMo121, SKD11
classic forging steel roll and match the world’s most
advanced levels.
The casting roll has significant advantages compared with
the same kinds of forging roll in its manufacturing method
and manufacturing cost and has a marked improvement in
energy resource saving and material saving.
welding pipe roll and cold roll formed steel roll in traditional
design is alloy forging steel.
Usually D2 and H13 are used in the design in America,
X155CrVMo121 and X40CrMoV5-1 in Germany , SKD11 and
SKD61 in Japan, Cr12MoV, 3Cr2W8V, Cr12, 9Cr2Mo and
GCr15 in China.
D2, X155CrVMo121 and SKD11 are about the same with
Cr12MoV. They are cold working die steel with high carbon
and high chromium, and it is a basic kind of cold working die
steel.
In production, D2, X155CrVMo121 and SKD11 forging steel
rolls, which are used in advanced rolling pipe mills, specially
under the condition of speedily cooling and speedily heating,
are all designed to avoid the phenomenon of crack on roll face
and looseness of roll shaft.
Now Cr12MoV forged steel roll is only used in small size roll for
welding pipe production lines in China and the great majority
of mills are still using low class forging steel roll consisting
of Cr12, 3Cr2W8V, 9Cr2Mo and GCr15.[1] These rolls have
poor wear resistance and the service life is only 1/2~ 1/3 of
above mentioned imported forging steel roll. For example,
the sticking steel phenomenon has appeared in the use of
domestic forging steel roll used in mills on stainless steel
welding pipe production lines, and the wear is produced on
the roll surface to use domestic GCr15 roll in 500x500x20mm
square pipe mills when used more than once per month.
The straightening pipe roll, HFW/ERW welding pipe roll and
cold roll formed steel roll belong to special-shaped roll. This
kind of roll is possessed of the features of complex shape,
more size and small batch, etc. Especially when producing
HFW/ERW welding pipe roll and cold roll formed steel roll,
one drawing only produces one or two products, the maximum
weight of product can be up to 8-10 tons per piece andminimum
weight of product can be up to 58kg per piece. This kind of roll
is difficult to produce to use forging tool steel – the inside hole
can not be forged and the utilisation factor of material is lower
than 50 per cent. D2, X155CrVMo121, SKD11 and Cr12MoV
materials have narrow forgeable temperature area and large
forged difficulty so the material has low utilisation factor and
high energy consumption. Because the roll has complex shape
and a big differential on wall thickness, the heat treatment has
greater difficulty.
China national standard “cast iron roll” and “cast steel roll”,
which was applied in 2009 only contains the rolls for rolling