研究了激光焊接热输入对纳米析出强化钢焊接接头熔深、显微组织及纳米力学性能的影响。利用体视显微镜和扫描电子显微镜对焊接接头的熔深、显微组织进行了分析，通过纳米压入实验对激光焊接接头各区域的纳米硬度和弹性模量进行了研究。实验结果表明：随着焊接热输入增加焊缝熔深逐渐增大，两者之间呈一元线性关系；当焊接热输入低于94 J/mm2时，焊缝为全马氏体组织；当焊接热输入超过125 J/mm2时，焊缝中出现贝氏体组织和铁素体组织；且随着热输入的增加，贝氏体和铁素体含量有所增加。随着焊接热输入的增加，焊缝区的纳米硬度逐渐降低，其原因为热输入增大致使贝氏体和铁素体的形成。焊接热输入对焊缝的弹性模量影响不明显，弹性模量在200 GPa左右。

Influence of heat input on the penetration, microstructure and nano mechanical properties of laser welding joint is studied. The penetration and microstructure of joints are tested by stereo microscope and scanning electron microscope. The nanohardness and elastic modulus of joints are tested by nanoindentation. The result shows that the penetration increases with the increase of heat input, there is a linear relationship between penetration and heat input. Microstructure of weld seam is consist of full martensite when the heat input is below 94 J/mm2. Bainite and ferrite appear in the weld seam when the heat input is over 125 J/mm2, the volume of bainite and ferrite increases with the increase of heat input. With the increase of the welding heat input the nanohardness decreases gradually, the reason for the decrease is the formation of bainite and ferrite. The influence of welding heat input on the elastic modulus is not obvious, the modulus of elasticity is around 200 GPa.