【正文】 f the stain.* If Sodium or Chlorine are detected, then the stain is probably from sea water.* If Sulphur is detected, then the stain could be caused by acid rain.* If Calcium or Iron is detected, then the water source could possibly be unclean tap water.These generalizations can only be used as a rough guide when determining where the water staining has occurred.AluminiumSodiumPotassiumChlorine.01 KeVTypical SEM Trace for a salt water caused “Waterstain”. HerringboneWhat is Herringbone?Herringbone is a surface marking along the strip which resembles a string of corporal’s stripes or the backbone of a fish.When does herringbone occur?There are a number of possible reasons:* the coolant may not be lubricating the strip well enough under the extreme pressure of the mill bite。* the strip may have a poor shape either from a previous pass or the present one。* the gauge reduction may be too great。* an earlier annealing treatment may have been missed* work roll finish may be incorrectly ground.What can you do about it?Herringbone is probably not the fault of your rolling technique, so you should follow or report on these matters:* check the position of the coolant to ensure it has the correct levels of additives to give lubrication. The Rolling Superintendent or Foil Metallurgist keeps records of coolant additive levels。* check the previous rolling and annealing history of the coil from the Lot Ticket report any ways in which this differs from the process schedule。* check the Roll Grind Requisition form, ensuring that the rolls have had the correct grinding performed on them. Lines of HolesWhat is lines of holes?Lines of holes are a continuous line of little holes in the metal. It varies in severity and can sometimes occur consistently throughout a coil. Lines of holes often cause strip break during the last single and the final doubling passes.When does lines of holes occur?This defect occurs when the metal has been scratched at any stage of processing or when a source of pickup is introduced to the roll bite.Why do lines of holes occur?When the surface of the strip has been broken, by:* mechanical failure, for example pulling the strip over a seized roll a scratch on the work roll surface。* careless handling of the metal。* the work rolls have been ground with no relief on the ends. This results in small pieces of work roll surface breaking off and being forced through the bite.What can you do about it?Try to protect the metal throughout the process:* check and maintain a high level of cleanliness on the mill regularly。* when you detect lines of holes, the coil should be isolated and put on hold. The coil should not be processed any further。* check the work rolls for signs of spoiling. Roll HolesWhat are roll holes?Roll holes are small marks or holes that repeat at a regular interval along the metal strip. This defect is very difficult to see during rolling.When do roll holes occur?When a roll work bee damaged and the damaged portion imprints a mark onto the metal surface.Why do roll holes occur?The work rolls can be damaged by a number of things:* grit。* dirt。* dust。* an inclusion in the strip.What can you do about them?* make sure the mill is cleaned thoroughly after a PM after a strip break。* make sure the metal stays off the ground。* wear clean gloves when you handle the metal。* remove one wrap from the feed coil if it has been standing for a long time。* if the holes are repeating at an interval of about 1 metre when you measure them along the length of the strip, then the mark is caused by your work rolls change the rolls。* if the holes are about 2 metres apart, they were caused before you received the coil there is nothing you can do about them. ChatterWhat is chatter?Chatter is evenly spaced, two tone lines which run across the width of the strip. If you could see the edge of the strip magnified, it would look similar to the edge of a piece of corrugated iron. You will hear chatter occurring before see it.When does chatter occur?Chatter often occurs during mill acceleration and deceleration, for short periods only. Only when this occurs at longer periods of times does the defect bee a problem.Why does it occur?Chatter is caused by machine resonance. Machine resonance can occur under the following condition:* the coolant is out of specification。* the feed strip is a hard alloy。* the pass line is incorrect。* the drive transfer box is worn。* the drive couplings are worn.What can you do about it?* if you want to finish the coil, try altering the mill speed and unwind tension, then stop rolling and look for the problem。* make sure the coolant is within specification at all times if it is not, stop the mill until you can correct it。* change the product or program until someone alters the mill。* if the pass line is wrong, check the mill shims。* change the work rolls.DESCRIPTION OF ROLL CHATTERTHE LINES ON THE STRIP IF MAGNIFIEDWOULD SHOW VARIATIONS OF GAUGE WHICH WOULD GIVETHE CROSS SECTION A CORRUGATED EFFECT AS SHOWN ABOVE Mill LinesWhat are mill lines?Mill lines are very narrow stripes which run along the strip in the rolling direction. To see them clearly, you need to straight down onto the strip.When do mill lines occur?When the work rolls or backup rolls are damaged.Why do mill lines occur?There are a number of reasons:* there is a scratch on the work roll。* the oxide layer on the work roll is uneven。* there are lines on the work roll caused by the damaged backup roll the backup roll can be damaged by a worn wiper.What can you do about them?* if the defect is present in the following products, you must do a roll change R No. 62715 Leigh Ma