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There are many performances that can lead to roll breakage from different mills, stands and roll material. In general, the reasons include following aspects:
- The improper cooling system, such as the lack of cooling water, the sudden water cutting off or too early and fast supply of water after taking no water rolling to roll some specified kinds of steels, will make rolls produce thermal stress, leading to barrel breakage.
- Roll accidents, such as stall, banding, winding, dislocation, rolling cold steel, rolling black head steel and so on, will cause roll breakage. These performances would suddenly increase rolling load to break roll.
- The improper rolling process, such as the unreasonable design of grooves, excessive single pass deformation and so on.
- The internal defects of rolls, such as excessive residual stress, unreasonable micro-structure, low material strength, structure transformation to form internal stress, or loose shrinkage to decrease effective loading area.
- The unreasonable design of roll, such as small diameter of barrel, deep grooves, too small loading area.
- The expanding of cracks, such as too long rolling period, the spread of cold and heat fatigue crack.
To avoid unnecessary roll breakage and extend roll campaign, each enterprise should carry out technical regulations seriously, strengthen technical management, analyse reasons and experience from every breakage cases.
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