This article describes the problems and solutions of rolls in the production of strip steel.
Key words: roll; quality impact; cause; solution
What are the causes of sticky rollers
The cause of roll sticking is excessive local reduction, broken strip fragments, folded strip steel, etc. entering the rolling mill. Generally, the slightly sticky rolls can be used after being manually ground with a grindstone, and the rolls must be replaced when the surface requirements of the strip are high.
What are the requirements for the material of cold rolling rolls
During the cold rolling process, the surface of the roll is subjected to great extrusion and strong wear. During high-speed rolling, steel jamming and over-burning will cause cracks on the roll surface. Therefore, the cold-rolled work roll should have extremely high and uniform hardness, a certain depth of hardened layer, and good wear resistance and crack resistance. The roll has good resistance to overburning and cracking, which are the main factors to prolong the life of the roll.
What are the effects of insufficient roll hardness on the rolling process
The hardness of the roll is not enough, the elastic flattening is large during rolling, and the contact area between the roll and the strip surface increases. To obtain a product with the same thickness, the rolling pressure must be increased, and the high rolling pressure is not good for the adjustment of the shape. The roughness of the roll is large, and the friction coefficient between the roll and the strip surface increases during rolling, resulting in increased friction and increased rolling pressure.
How to use bending rollers to eliminate “waves on both sides” and “waves in the middle”
When there are waves on both sides of the strip during the rolling process, it means that the rolling pressure on both sides of the strip is too large. At this time, positive bending rolls are used to eliminate the waves on both sides. When there are waves in the middle, it means that the original crown or thermal crown of the roll is too high Large, then use negative bending rolls to eliminate.
How to prevent deviation when wearing the belt
First of all, before threading the belt, the pressure must be corrected, the roll gap must be given, the quality of the material, whether there is edge wave, and the running condition of the strip must be observed. If the deviation is found, adjust and press down in time. If the deviation is too fast, it cannot be adjusted and stops quickly. During the rolling process, the deviation of the strip generally occurs when the strip is threaded or flicked. The main reasons for the deviation of the strip are as follows:
1)Due to the reason of the incoming material, the shape of the incoming material is not good, and there are serious side waves, so that the strip edge control device cannot be adjusted accurately and timely, causing the strip to deviate in the first pass. The measures to be taken are rolling speed Don’t be too high, adjust in time to press down the swing adjustment or stop in time. 2) The reason for the operation is that the swing adjustment of the operating pressure is unreasonable, causing the strip to deviate. 3) Electrical reasons: Strip deviation and broken strips are caused by the sudden decrease or disappearance of the tension of the coiler during the rolling process. 4) Due to the serious taper of the roll after grinding, the pressing is inaccurate, and it is more difficult to operate the pressing and swinging during rolling. The light one will produce serious side waves and cause plate shape defects, and the severe one will cause deviation Broken belt. 5) The failure of the strip edge control device, the deviation of the deviation device, the pollution of the lamp tube or the receiving device, etc., will cause the deviation of the deviation device to fail and cause the deviation of the first pass.
What quality defects will occur in roll grinding, and what adverse consequences will occur in the rolling process
1)The taper of the roll body: the reduction cannot be corrected, and it is easy to cause one side wave, and the plate shape is difficult to control. The taper of the roll body is required to be less than0.1mm2) The grinding is not round: the roll body has ellipticity. Vibration occurs during the rolling process, the rolling pressure fluctuates, and the strip thickness varies along the length direction in waves. 3) Convexity: In the process of the unit, the roll is required to be a flat roll. If the roll has a crown, it is easy to produce intermediate waves and second rib waves in the rolling process. 4) The surface roughness of the roll is too large. During the rolling process, the rolling pressure increases, the shape of the plate is difficult to control, and the surface quality of the strip is affected. 5) There are cracks on the roll body, because the cracks have not been trenched and ground. Flaw detection was not carried out on the roll, and protruding rolling marks in the shape of cracks appeared on the surface of the strip during the rolling process.
Causes of roll breakage
1) Reasons for roll manufacturing: The roll neck itself has defects, and this part bears the largest torque. Roll breakage generally occurs at the roll neck. 2) Broken rolls caused by bursting rolls: During high-speed rolling with large rolling force, bursting rolls cause rolls to break. The broken roll part is at the burst part. 3) The roll is broken due to the operation: the pressure is deflected, and the roll is stressed on one side. It is easy to cause the roll to break at the roll neck.