| 5×××aluminium alloy which are products with high technology and high annexation value are widely used in the industry of antomobile, mechanical, aviation, shipping, electronics, et al.5052 aluminium alloy is one of the most widely used products in 5×××aluminium alloy. At present, in home market and foreign market the traditional DC technique is still the chief way of producing 5052 aluminium alloy strip. But the Twin-Roll Cast technique is still not used widely in industry. The TRC technique has many obvious advantages of energy saving and consumption reducing, low investment, short production process, et al. Hence, the exploratory studis of cold roll and annealing for 5052 aluminium alloy slab by TRC were carried out. The aim is to obtain the changing rules of microstructure and properties of 5052 TRC slab. There is of great significance to stablly produce high quality 5052 aluminium alloy strip using the TRC technique.In this paper, by means of DSC analysis, OM, SEM and EDS, the cold rolling process and annealing process of the 5052 TRC slab is investigated and specially the influence of annealing process on microstructure and properties is maily studied, which provide reliable theory basis of practical production of 5052 TRC slab. The main conclusions are as follows:1. There is center segregation in the 5052 TRC slab. The center segregation consists complexly of Al3Mg2, Al-Fe-Si etc phases and some eutectic structure and compounds that containing rare earth elements. In the center segregation Mg element segregation is severe and the aggregation of Fe, Si and rare earth elements is obviously. When the twin-roll casting is carring out, the liquid alloy that enriched alloy elements is drived toward the center part along dendrite spacing, and then the center segregation is formed when the solidification is end. The center segregation is effectively reduced by high temperature homogenizing because the solid solution of Mg element. But the center segregation is not eliminated by high temperature homogenizing. The microhardness of slab is increased by 16% which is up to 74.8HV0.1/20 after high temperature homogenizing and the structure uniformity is improved. The proper homogenizing annealing regularity that is annealing at 580℃for 20h of the slab is obtained.2. The experiment slab was cold rolled by rotating 90 degee and 180 degree and it result in the tensile strength is decreased by 14%. The elongation is increased by 16% and the yield tensile ratio is decreased to about 0.5 when it is rolled by rotating 90 degree. The microstructure and properties of sheet is improved obviously after intermediate annealing. When the annealing temperature is 420℃, the tensile strength is 227 MPa and the elongation is 16%. The best intermediate annealing regularity of the cold roll sheet is annealing at 420℃for 30min.3. The range of recrystallization temperature of cold roll sheet from experiment is 300℃～340℃. With the annealing temperature increasing, the grain growth does not appear obviously, on the contrary, the grain tends to becoming little. After the recrystallization, with the holding time extended the grain growth does not appear obviously too.That is inconsistent with the traditional rules of recrystallization.After the annealing to the cold rolling sheet obtained from the experiment, massively tiny particle whose size is for 1μm disperse in the matrix, which hinder recrystallization grain growth and enhance the tensile strength of the sheet. After the sheet was annealed at 340℃for 1h, the tensile strength is increased above 280MPa and the elongation is 9%, so they concert well and the yield tensile ratio is high.4. With the annealing temperature raising, the corrosion resistance of hydrochloric acid of the experiment sheet is increased while the corrosion resistance of sodium chloride solution is decreased. The rate of weight loss corrosion of hot roll sheet is lower than the experiment sheet and the corrosion resistance is better.5. Under the different annealing temperature condition the anisotropy of the cold rolling sheet after annealing presents typical "∧" shape, and assumes r0 |
PDF Full Text Request