The Microstructure And Mechanical Properties Comparison Study Between Double-stand Tandem Cold Rolling And Single-stand Cold Rolling For 3104 Aluminum Alloy Sheet

The 3104 aluminum alloy sheet with the high strength, good deep drawing, ironing tensile properties and good corrosion resistance, is widely used for the production of cans. To meet the growing market demand for the yield of aluminum plate strip, tandem cold rolling as the new process way is replacing the traditional single-stand cold rolling, but the evolution law of tandem cold rolling alloy sheet microstructure and mechanical properties in the production process is not yet entirely clear. In this paper, 3104 aluminum alloy tank material produced by Southwest Aluminum company acts as the research object, and was studied by laser microscope(LM), optical microscopy(OM), scanning electron microscopy(SEM) observation and DSC spectrum analysis, and X-ray diffraction, room temperature tensile, microhardness, drawing test, cupping test and other detection methods. The evolution law of microstructure and the mechanical properties of 3104 aluminum alloy sheets produced with the double-stand tandem cold rolling and traditional single-stand cold rolling was compared, and the differences and the mechanism of evolution law was explored, providing experimental data and theoretical support to make the optimized cold rolling production process.The main research conclusions are as follows:(1) With the production of cold rolling, the yield strength and the tensile strength in each stage of 3104 aluminum alloy cold-rolled sheet were increasing. The elongation of single-stand cold rolling sheets displayed gradually decreasing trend, which of double-stand tandem cold rolling sheets reduced for the first two passes and increased slightly after two passes. Both the yield strength and the tensile strength of the double-stand tandem cold rolling finished sheets were lower than the single-stand cold rolling sheets on different directions( 0o, 45 o, 90o), but elongation was higher than that of single-stand cold rolling sheets. The yield strength, tensile strength and elongation of double-stand tandem cold rolling finished sheet was 277 MPa and 311 MPa and 4.5%, respectively, while of the single-stand cold rolling finished sheets was 295 MPa and 321 MPa and 2.7%, respectively.(2) Under two kinds of cold rolling process, mechanical properties of 3104 aluminum alloy cold-rolled sheets in the various stages different directions had obvious differences, showing anisotropy. Cold rolling sheets exhibited typical characterization of "copper type" texture. Texture intensity of double-stand tandem cold rolling finished sheet(max = 11.129) was weaker than that of single-stand cold rolling finished sheet(max = 12.164), which of finished sheet with 2+1+1 cold rolling process was between them. Tandem cold rolling finished products showed lower anisotropy and lower work hardening, which were more favorable to deep drawing preparation cans.(3)The sheets received by two kinds of process had the same organization evolution discipline: with the increase of cold rolling reduction, grain organization got squashed along rolling direction, finally evolved into fibrous tissue. But after the 2nd pass, grains of the single-stand cold rolling sheet were broked more seriouly, smaller and more uniform. Moreover, the large length to diameter ratio became greater and the degree of grain fibros was higher than double-stand tandem cold rolling sheets. With the cold rolling deformation, the whole compounds size of single-stand cold rolling sheet were more refined, inheriting the early distribution features, and the compounds size of the finished sheet became more uniform; but the original particle size distribution of tandem cold rolling sheet would change with the accumulation of deformation, being a smaller whole size and a bigger difference of particle size(polarization), namely the percentage of middle particle sizes were reducted. This performance was most obvious in the finished sheets, resulting in low elongation and uneven fracture toughness nest.(4)The finished product sheets of two kinds process of single-stand cold rolling and tandem cold rolling mainly existed Al6 Mn, Mg2 Si, Al6(Fe Mn) ternary phase, Al9Fe0.84Mn2.16 Si quaternary phase compounds, which was no differet between the two kinds of process. But tandem cold rolling has higher peak. Texture detection eliminated the effect of texture, showing that there were more compounds precipitate in tandem cold rolling finished sheet. After low temperature annealing of 160 oc 4h, 6h and 200 oc 1h, 2h, 3h for 3104 aluminum alloy finished sheets with single-stand cold rolling, the test results showed there were more compounds precipitating further. The second phase particles which was induced precipitation by high strain grew up, little contributing to the strength. Thereafter, due to the tandem cold rolling sheets was staied warm at a long time at a higher temperature after curling insulation. Then, Strain-induced solute atoms of matrix participate attached to the original the second phase particles and the particles became a non-uniform distribution. This phenomenon was no contribution to strength, but can result in sheet soften because of the weaken solid solution strengthen.