Al对δ-TRIP钢电阻点焊性能及显微组织的影响
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摘要
通过对不同Al含量的δ-TRIP钢进行电阻点焊试验,和对点焊接头进行显微组织、抗拉剪性能和显微硬度的分析,得知在电极压力为3 kN、焊接时间为7cyc时,δ-TRIP钢T1、T2的可焊电流区间分别为4.5~5.5、4.0~5.0 kA,并且两者的拉剪力均超过10 kN。研究发现,提高Al含量有利于在熔核区和热影响区获得包含δ铁素体的混合组织,从而避免了形成完全马氏体,改善了与母材之间的硬度差异。通过EDS分析发现,在凝固过程中Al会从液相扩散到δ铁素体中,从而有利于在室温下获得更多较为稳定的δ铁素体。
Resistance spot welding tests were conducted for δ-TRIP steels with different Al contents,and the microstructures,tensile shear strength and microhardness of the welding joints were studied.When the electrode force was 3 kN and the weld time was 7cyc,the proper welding current ranges for δ-TRIP steels numbered as T1 and T2 were 4.5-5.5 kA and 4.0-5.0 kA respectively,and the tensile shear strengths of both steels were higher than 10 kN.The results show that elevated aluminum concentration allows larger amounts of δ-ferrite to be retained in the final microstructure,preventing the formation of fully martensitic microstructure in either the heat affected zone or the fusion zone and reducing hardness difference in the base metal.It has been found,according to EDS analysis,that Al diffuses into δ-ferrite from liquid during solidification,resulting in larger amounts of stable δ-ferrite at room temperature.
Resistance spot welding tests were conducted for δ-TRIP steels with different Al contents,and the microstructures,tensile shear strength and microhardness of the welding joints were studied.When the electrode force was 3 kN and the weld time was 7cyc,the proper welding current ranges for δ-TRIP steels numbered as T1 and T2 were 4.5-5.5 kA and 4.0-5.0 kA respectively,and the tensile shear strengths of both steels were higher than 10 kN.The results show that elevated aluminum concentration allows larger amounts of δ-ferrite to be retained in the final microstructure,preventing the formation of fully martensitic microstructure in either the heat affected zone or the fusion zone and reducing hardness difference in the base metal.It has been found,according to EDS analysis,that Al diffuses into δ-ferrite from liquid during solidification,resulting in larger amounts of stable δ-ferrite at room temperature.
引文
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