Galvanized steel sheet is widely used in construction, home appliances, automobile and other industries. Due to its complex production process and various processes, galvanized steel sheet may produce a variety of quality defects, affecting the surface
beauty and user use. Today, I'd like to share this article to talk about the causes and solutions of slip line defects of galvanized steel sheet. Come and have a look
1. Performance characteristics.
When the lie is visible and not visible, there is a sharp tactile texture in the subsequent processing.
2. Cause analysis.
In the actual production process, the slip line is mainly caused by the following
(1) The flatness setting is unreasonable. After a certain amount of flattening deformation, a large number of movable dislocations are produced. The dislocations get rid of the bondage of C and N atoms in solid solution, and the deformation
can continue under a small stress, thus eliminating the yield plateau. Under a certain flatness, the yield strength decreases with the increase of flatness until it reaches the lowest point, and then the yield platform disappears; with the further improvement
of flatness, the yield strength increases, the work hardening increases, the deformation capacity decreases and the machinability decreases.
(2) Natural prescription. After annealing and flattening, the yield plateau of galvanized steel sheet has
been eliminated. After long-term storage at room temperature, C and N atoms re diffuse around the dislocation to form "Coriolis air mass", which results in the re emergence of yield plateau.
(3) Artificial aging. The yield plateau of galvanized
steel sheet which needs to be sprayed, baked or coated with film heating will reappear at high temperature.
(1) Reasonable setting of flatness can not only eliminate the yield plateau, but also avoid the excessive increase of
yield strength and reduce the formability of materials.
(2) Compared with continuous annealing, the heating and cooling rates of batch annealing process are slow (generally 20% / H40 ~ C / h), and the holding time is long. After annealing, a large
amount of C in the steel precipitates in the form of FEC, and N atoms fully precipitate in the form of A1N, which greatly reduces the number of solid solution atoms in the steel.
(3) Advanced continuous annealing process, such as R-OA technology,
can improve the driving force of FEC nucleation and growth through rapid cooling and low-temperature cooling, so that the solid solution C can precipitate in the form of FEC, and increase the aging resistance.
(4) The slab is heated at a lower temperature
during hot rolling, and combined with the warm coiling process of new technology and new product of gaoyi74-china, the precipitation and growth of A1N, Fe and C are promoted, and the solid solution N content in the steel plate is effectively reduced.
(5) Using ultra-low carbon interstitial free atomic steel, the steel contains very low amount of C and n elements. At the same time, Ti, Nb and other strong carbonitride forming elements can further fix C and N atoms, which can completely solve the