Cold-rolled Sheet "hole" Defects Research

The cold rolled strip extensively useds for manufacturing industries, such as car, homily electrical appliances and motorcycle...etc of drawing formation to take shape piece and surface panel piece. In addition to having very high request to size accuracy, plate profile and mechanics function of cold rolled strip, the customer also has a very high request to cold rolled strip surface quality and especially used for the surface panel piece of the cold rolled strip. The cold rolled strip is requested to have no surface defeats, because of any small of the surface defeats will be enlarge in paint. Any surface defeats will serious influence customer's product.The production of cold rolled strip is to be thick the 150 mm～200 mm of casting slab through the hot rolling, pickling, cold rolling, annealing, skin passing, finishing etc. process form that thickness is the 0.25mm～2.5 mm thick cold rolled strip. The abnormity of any above process will result in cold rolled strip surface defeats, specially when producing thickness is less then 1.0 mm cold rolled strip, the most of defeats in casting slab will also appear on cold rolled strip surface."Hole" defeats is that the cold rolled strip have the steel body discontinuous phenomenon. "Hole" defeats is one of the most serious defeats for the cold rolled strip. Though on a cold rolled strip(the weight is about 8 tons) general the "hole" is less then ten, because the defeats parts can be use after cuted off, not only use a production efficiency greatly for lower, more the seriously certain customer think the cold rolled strip existence a quality problem but brush-off usage, make production factory to suffer a quality crisis, severity influence factory of benefit.This paper aims at to Pan Gang's cold rolled strip at some time to appear of batch quantity"hole" defeats, adopt the X—650 Electronics probes and the EDAX Energy Spectrometer to checkout the appearance of the "hole", to research the organization and composition of the defeats. the conclusion is that the "hole" defeats mainly includes four kinds of types, respectively is:①"Hole" is formed in the rolling extension process because of the residue come into the steel in casting process;②The steel can be tear to pieces in the cold rolling process;③The foreign body formed in casting process can be press into steel to form"hole" in the rolling process④The foreign body on the roller can be press into steel to form"hole" in the rolling process.For resolving that residue how come into the steel in casting process , we have been research the foreign body source. For reducing that the cold rolled strip"hole" defeats we have been field testing . we put forward precautionary measure against the "hole" and "hole" defeats got a good contrail. Quantity of the cold rolled strip with "hole" descends to from monthly more than 1000 tons before manages every month 60 tons the following. The economic benefit and social benefit are huge.