[Introduction: Roller marks are the most common defects in thin plate products, and the information is quite extensive. Therefore, today we only extract the key points and avoid unnecessary details.]
What are roller marks?
Roller marks are indentations caused by damage or foreign matter on the surface of the roller being periodically replicated onto the steel plate as the roller rotates.
Thin plate products come into contact with nearly a thousand rollers in the cold rolling process alone, with roller diameters ranging from a minimum of 3 centimeters to a maximum of over 1.5 meters. (The difference in roller diameter is like the difference in planets in the following figure)
Roller materials include softer polyurethane and chrome-plated hardened rollers; functionally, there are support rollers, pinch rollers, turning rollers, rolling mills, etc.; the causes of roller marks may be roller damage or foreign matter adhesion, with foreign matter including both hard and soft foreign matter.
So many factors combined lead to one result: the morphology and cycle of roller marks are varied and unpredictable.
Characteristics and identification of roller marks:
The core characteristic of roller marks is "periodic replication," which determines its three elements: similar morphology, same position, and equal cycle. (The distance from the edge of the strip is the same, and the periodic spacing between the roller marks is equal)
Sometimes more complex situations are encountered, such as two adjacent roller marks appearing on the same roller. At this time, pay attention to measuring the accurate cycle, similar to the separated measurement in the figure below.
Of course, occasionally there will be more complex situations. However, no matter how the roller marks change, continuously measure 3-4 points. If all three elements are met, then we can confirm it as: upper (or lower) surface, *** mm from the edge of the strip, with a cycle of *** mm roller marks.
Classification of roller marks and their impact on use
Classification
Roller marks can be roughly divided into three categories according to their morphology or cause: convex type, surface damage type, and rolling type. Typical morphologies are as follows:
Is it a bit abstract? Let's further analyze their cross-sectional morphology:
Convex type: Like mosquito bites, the roller marks are gentle, the boundaries are not obvious, and the thickness of the steel plate does not change.
Surface damage type: There are obvious damaged points in the roller marks, penetrating the surface, and there are steep protrusions on the reverse side.
Rolling type: Produced under double-sided high-pressure conditions such as rolling mills, the roller mark boundaries are clear, and there are no obvious protrusions on the reverse side (there may be bright spots).
Impact on use
Convex type: It will be improved after the blanking line straightening machine, and it will continue to be reduced during stamping;
Surface damage type: Because there are damaged points on one side and steep protrusions on the other side, it is difficult to improve in subsequent processing;
Rolling type: Since there are no obvious marks on the reverse side, most of them can be used upside down.
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