通电时间对热冲压高强钢点焊接头性能及失效方式的影响

热冲压硼钢电阻率大、焊接热循环升温速度快、峰值温度高、局部冷却速率的不均匀,决定了点焊接头性能差别极大.点焊接头在剪切载荷作用下有界面断裂、焊核拔出和部分焊核拔出三种失效方式.以1.6 mm厚的热冲压硼钢为对象,研究不同通电时间对接头显微硬度、承载性能、失效方式的影响规律,分析失效的形成原因和失效机理.结果表明,上述三种失效方式承载能力和破坏吸能力相差不大,焊核拔出并不能作为评判高强钢点焊接头质量好坏的标准.焊接缺陷、承载时的高度应力集中以及热影响区局部韧性恶化是影响热冲压高强钢点焊接头失效方式的三大主要因素.

Influence of welding time on performance and failure mode of hot stamping boron high strength steel spot-welded joints

The characteristics of large resistivity,high peak temperature in welding thermal cycle,fast rising rate of temperature and uneven local cooling rate determined the heterogeneity in resistance spot-welded joints of hot stamping boron high strength steel,which resulted in three different failure modes of the joints. The effects of welding time on microhardness, bearing performance,failure modes of the resultant joints were studied,and the failure mechanism was investigated. The results show that the capacities of bearing and energy absorption between 400 ms and 600 ms of welding time were equivalent, and the nugget pull-out could not be the standard for evaluating the quality of joints. The welding defects,stress concentration and local toughness deterioration in HAZ were three main factors that affected the failure of the joints.