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J
uly
2011
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A
rticle
The successful research and development of special sand mould
can raise casting quality.
On the basis of some questions of complex shape, more size
and small batch of roll and poor cast properties of high chromium
alloy material Shandong have explored and innovated new cast
processes and it can achieve high quality forming of complex shape
roll.
From the outside feature of welding pipe roll exported to Oman
and India we can see that the roll possessed of big differential size
section and special-shaped section is difficult to cast by traditional
cast methods.
2.2.3 Researching and developing of heat treatment and
machining process
According to differential working condition and differential
composition high chromium alloy has designed a different heat
treatment process.
Through practice and continuous revision over many years, the heat
treatment system in series has been formed, they can guarantee the
good property of roll.
High chromium alloy has excellent quenching degree and the
quenching depth as air quenching is 300mm.
No ready-made production line can be introduced for machining
high chromium roll, so machining process, drilling holes process,
screwing process and devices are all designed by Shandong.
2.3 Compared with manufacturing processes
Casting formed or forging formed roll block are two different
manufacturing methods. The casting block compared with forging
block is still close to a product’s shape, so it can effectively increase
the utilisation factor of raw material, greatly decreasing energy
consumption. The high chromium alloy casting formed process
is simple compared to forging tool steel formed process, which is
traditional process at home and abroad. This process can save the
forging process and reduce the manufacturing period. Compared
with the forging process of low alloy tool steel at home, every ton of
finished roll can save 1.4 ton standard coal and 350 kilowatt-hour
power.
The content of high-price alloy elements are raised in new
composition design, but the cost increased by the above mentioned
reason is significantly lower when compared to a cheap casting
process with an expensive forging process.
The price of high chromium alloy cast straightening pipe roll, HFW/
ERW welding pipe roll and cold roll forming steel roll are only
1
/
3
–
1
/
2
of price of D2, X155CrVMo121 and SKD11 forging steel roll. The
price is lower than Cr12MoV forging steel roll produced at home
and is equal with ordinary forging alloy steel roll produced at home.
The successful research and development of high chromium alloy
casting formed process can decrease energy consumption, increase
utilisation factor of raw material, simplify production process, reduce
production period and save production cost.
3. Compared with properties
3.1 Compared with utilisation properties
High chromium alloy steel pipe straightening roll, HFW/ERW
welding pipe roll and cold roll forming steel roll have been used
in more than ten advanced production lines of steel pipe and cold
roll forming steel at home and abroad over the last ten years.
The result has proved that the service life is up to the level of D2,
X155CrVMo121 and SKD11 forging steel roll and is two times as
long as X165CrMoV12KU and 9Cr2MoV forging steel roll, is three
times as long as 3Cr2W8V, Cr12 and GCr15 forging steel roll.
Now high chromium alloy roll has been the first selected roll for steel
pipe straightening, and has achieved good feedback after being
used in the mills of HFW/ERW welding pipe and cold roll forming
steel in China and abroad.
The high chromium alloy roll used in the biggest production line of
stainless steel welding pipe in China can overcome the defects of
stick steel and scratching on steel pipe face, which is presented in
traditional forging steel roll producd at home.
The high chromium alloy roll used in 500×500×20mm square steel
pipe mills, which is in biggest demand in China, can effectively
ensure the product’s quality of rolled steel pipe, and the rolls have
been used more than five years and still continuous now.
3.2 Compared with sample property
Separate sampling from X155CrVMo121 finished steel pipe
straightening roll, D2 finished steel pipe straightening roll,
SKD11 finished welding pipe roll, high chromium alloy steel pipe
straightening roll (casting state, eliminated stress temper), high
chromium alloy welding pipe roll (quenching and temper state),
sliced along roll face to inside hole. The serial number is A. B. C. D.
E. See figure 4.
3.2.1 Compared with hardness and quenching degree
To do hardness test to sliced sample along outside to inside, the
results are as follows.
Figure 3:
Welding pipe roll exported to Oman and India
Figure 4:
Five kinds of rolls
after sampling