Bar Rolling Process and Equipment Selection
1. Selection of Bar Rolling Process Layout
For hot-rolled bars, the bar rolling process layout scheme is mainly divided into continuous rolling and the semi-continuous rolling.
1.1 Semi-continuous Rolling
A two-roll reversing mill + continuous rolling mill (6 or 8)are arranged generally. The two-roll mill has a front and rear turning-over device for steel and a manipulator. The continuous rolling mill is generally flat/vertical, or vertical/flat arranged. The reason why it is vertical/flat arranged is that we do not have to turn steel when the incoming material is a rectangular blank.
1.2 Continuous Rolling
Roughing mill (4 or 6 rolling mills, 4 rolling mills are preferred) is arranged first, then the first medium rolling mill and the second medium rolling mill, the last are the finishing mill and the reducing and sizing mill.
2. Billet Selection
Forging billet, rolling billet, continuous casting billet, ingot and electro-rolling billet are mainly used in the production of alloy steel bars. Billet selection is mainly based on steel grades, compression ratio and other requirements.
2.1 Requirements of Steel Grades for Billets
Forging and rolling blanks: (ledeburite and martensite), high-tech, joint (cold die), stainless (martensite, dual-phase steel).
Continuous casting billet: carbon bonding, bonding, (carbon worker), spring, bearing (ring), stainless (Austenite, ferrite).
Ingot (or slag): bearing (bead), alloy die (ledeburite and martensite).
3. Rolling Mill Selection
3.1 Rolling Mill Size
In general, the mill is selected as few as possible (the mill size model) to reduce the number of spare parts. Usually, a unit is consists of the same kind of rolling mill. The selection of the mill size is mainly based on the principle that the maximum passing of the unit is through the rolling stock, and the maximum rolling stock is easy to bite. However, it is not allowed to choose too large to avoid waste, and at the same time, it is necessary to reserve a certain margin for future development. The selection of rolling mills should not be too large, because the dimensional accuracy of small-sized rolling mills with large rolling mills is not guaranteed.
3.2 Mill Roll Length
Roll length of rolling mill generally considers two aspects: first, roll body stiffness. If the roll body is too long, it will affect the stiffness, which is not conducive to the dimensional accuracy of the rolled piece. Second, roll matching. The length of the roll can be matched with the number of grooves, which is helpful to reduce the consumption of ton steel and save rolls.
3.3 Rolling Mill Machine Layout
The rolling mill layout of the bar rolling process should consider the shearing head and tail, stripping area, hot rolling, tension-free looper control, and the maximum length of the rolled piece in reversible rolling process should also be considered in semi-continuous rolling.
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