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我厂购进的一批LF21,厚1.0mm的M状态铝合金板,在零件加工引伸中出现100％开裂。而且无论怎样调整方位,垂直于轧制方向上都有严重的开裂现象。该铝合金的化学成分(Wt·％)为1.05Mn,0.43Fe,0.1Si,0.02Mg,0.03Zn,0.028Ti,0.004Ni;其σ_b为125N/mm~2,δ为22％。化学成分和力学性能均符合标准的规定。检验其晶粒度时发现,开裂的铝合金板晶粒相当粗大,达3—4级。而过去采用的未出现开裂的铝合金板晶粒细小,比标准规定的一级还细小。众所周知,LF21合金退火时易产生晶粒不均匀现象,特别是在箱式炉中退火更易产生粗大晶粒,致使深冲或弯曲时出现裂纹。而采用盐浴退火则可以得到较细
A batch of LF21 purchased by our factory and the M-state aluminum alloy plate with a thickness of 1.0mm appeared 100% cracking in the part processing extension. And no matter how to adjust the position, perpendicular to the rolling direction has a serious cracking phenomenon. The chemical composition (Wt ·%) of this aluminum alloy is 1.05Mn, 0.43Fe, 0.1Si, 0.02Mg, 0.03Zn, 0.028Ti, 0.004Ni; its σ_b is 125 N / mm 2 and its δ is 22%. Chemical composition and mechanical properties are in line with the provisions of the standard. Test the grain size found that cracking aluminum alloy plate quite coarse, up to 3-4 grade. The past did not appear cracking of the aluminum alloy plate fine grain, smaller than the standard level. As we all know, LF21 alloy easy to produce uneven grain annealing, especially in the box furnace annealing is more likely to produce coarse grains, resulting in deep drawing or bending cracks. Salt bath annealing can be thinner