S30408焊接接头低温力学性能试验

摘要

Tensile and impact tests at-196 ～ 20 ℃ were conducted out to obtain the low-temperature tensile properties and impact toughness of the S30408 base metal and welded joint.The experimental results show that the yield strength and tensile strength of both base metal and welded joint significantly increase with temperature decreasing due to the cryogenic strengthening effect.The Charpy absorbed energy and lateral expansion tend to degrade when temperature decreases.The welding zone has the worst impact toughness because it contains the largest amount of the ferrite content.The reduction of the impact toughness in the welding zone is related to the decreasing in the crack propagation resistance at cryogenic temperatures.The inhomogeneous ferrite distribution in the welded joint leads to non-uniform micromechanical properties which causes a plastic constraint on the deformation,and consequently results into a weak ultimate bearing capacity of the welded joint.%为了研究国产奥氏体不锈钢S30408在低温下的力学性能变化规律,通过-196～20℃下的低温拉伸试验和冲击试验,获得S30408焊接接头与母材的低温拉伸性能和冲击性能数据.试验结果表明:焊接接头与母材的屈服强度和抗拉强度随温度降低呈现明显的增加趋势,低温强化效应显著;夏比冲击吸收能量和侧膨胀值则随温度降低呈现下降趋势;焊缝处铁素体含量最高,冲击韧性最差,且焊缝处冲击韧性的降低与其本身在低温下抵抗裂纹扩展能力的降低有关;铁素体分布的不均匀性致使焊接接头存在微观力学性能的差异,对接头处变形产生塑性拘束,削弱了焊接接头的承载能力.