| This paper has studied the effects of the composition, metallurgical structure and the second phase of the 5383 aluminum alloys on their properties. The difficult problems such as the hot-rolling cracking, the too-low of the specified non-proportional extension strength and the distortion and curling up in the machining of the plates have been solved; the industrialized large production has been realized. The production process of the 5383H116 has been studied, which has laid out the foundation of the application of the 5383 aluminum alloys on the shipbuilding. The material microstructures have been observed through the optical, transmission electronic and scanning electronic microscopes; the phase components and distribution have been analyzed also. The optimal production process for 5383 aluminum alloys is as follows: in the furnace the methods of degassing and cleansing such as the combined fluxing with argon and chlorate, and the sprinkling a fluxing on the melt surface etc. are employed ; in the casting the methods of the filtrations with the woven glass cloth and the ceramic foam, and the SNIF fluxing are unitedly used; the casting uses semi-continuous type, of which the temperature range is 685℃~695℃and the speed is 45 mm/min ~60mm/min; the homogenization of the slabs is that the temperature is raised to 440℃at the heating rate of 30℃/h and held for 5 hours, then heated to 510℃at the heating rate of 20℃/h and held for 2 hours; the edges of the slabs are planed and their major surfaces are scalped; the hot rolling temperature is 450℃~480℃; and for the 5083H116, the cold rolling with the wrought rate of 18%~20% is needed; the temperature of stabilization is 201℃~230℃and its holding time is 2 h. It can be guaranteed that the quantity of Mg2Si with the dimensional range 0.5μm ~5μm can be controlled within the limits of 150 ~2000 particcles/mm2; the percentage of the quantity of Mg2Si over 5μm in dimension to the total quantity of Mg2Si over 0.5μm in dimension should not overpass 20%. The quantity of the various phases over 0.5μm in particle dimension such as AlFeMnSi, Al(Mn,Fe), AlFeCr, CrSi, Al3Zr, Al3( Zr, Ti) has to be less than 2500 particles/mm2. The surface fraction with the particle dimension over 0.5μm is less than 2%.The percentage of the quantity of particles dimension over 5μm to the total quantity of particles dimension over 0.5μm should not overpass 20%. The strengthened effects on the 5383 aluminum alloys are insignificant when they are added Zr or Ti separately. The strengths of the 5383 aluminum alloys, however, can be increased obviously by the composite micro-alloying with the Zr and Ti, of which the increases of the tensile and The specified non-proportional extension strength can be reached to the 22MPa and 20MPa respectively. When 5383 alloys are treated by the composite micro-alloying with the Zr and Ti, the composite particles of Al3 ( Zr, Ti). Will be formed. The primary Al3 ( Zr, Ti) has the powerful grain refinement action; the secondary Al3 ( Zr, Ti) point particles forcefully penetrate the dislocation and sub-grain boundaries. Therefore the recrystallization of the 5383 alloys are inhibited effectively. The composite micro-alloying with the Zr and Ti can greatly intensify the effects of the trace Ti on the strengthening of the fined grain, substructure and precipation generated in the 5383 alloys. Since the price of Ti is cheaper than Zr, the added quantity of Zr can be lowered by the composite micro-alloying with the Zr and Ti, and the cost of the 5383 alloys can be descended. In the industrial large-scale production of 5383 alloys, the cleavage fracture takes place easily when they are hot rolled at higher temperature (510℃~540℃). The alloys are possible to generate the cleavage fracture, even if they are hot rolled at normal temperature (450℃~480℃), when the content of the trace impurity of sodium in the alloys is over 0.0001% (mass percentage). This is caused by the pollution of the sodium in the industrial production. It is known, through observing the 5383 alloys cracked ingots, that the cleavage surfaces are on the equally proportional surfaces of the {100} and {110}. The area of the brittle cleavage surfaces is up to 50%~60%. The specified non-proportional extension strength with the 5383 alloys can be ensured by selecting the appropriate annealing temperature. The plates curling-up deformation from machining is mainly caused by the residual stress in the plates, which can be solved by the stretching deformation method studied in this paper.
|
PDF Full Text Request