Ti-Mg复合脱氧对钢热影响区组织和冲击性能的影响

利用Gleeble-1500热模拟试验机进行焊接热模拟实验,研究16Mn钢经微Ti和Ti-Mg处理后焊接热影响区组织及冲击性能的变化,并利用扫描电镜和能谱分析法观察和分析实验钢的夹杂与冲击断口形貌.Ti和Ti-Mg复合处理试样的热影响区显微组织分别主要是晶界块状铁素体+晶界侧板条铁素体和晶内针状铁素体+晶界块状铁素体.经Ti处理后钢中夹杂物主要为5μm左右的TiO_x+MnS复合夹杂,经Ti-Mg复合脱氧后钢中夹杂物主要为2μm左右Ti-Mg-O+MnS组成的复合夹杂,且后者明显细化了钢中夹杂物尺寸.Ti-Mg复合脱氧试样中存在大量细小夹杂颗粒,一方面可钉扎裂纹,另一方面诱导形成了使大量针状铁素体,大焊接热输入条件下Ti-Mg复合脱氧试样热影响区冲击韧性明显强于单独Ti处理的试样. 

Effect of Ti-Mg complex deoxidation on the microstructure and impact properties of HAZ in steel

The effects of micro Ti and Ti-Mg on the microstructure and impact properties of welding heat affected zones(HAZ)in 16 Mn steel were studied by welding thermal simulation on a Gleeble-1500 hot simulator. The composition of inclusions and the Charpy impact fracture morphologies of the test steels were analyzed by scanning electron microscopy with energy dispersive spectrometry. The microstructures of HAZ in the Ti and Ti-Mg treated steels are mainly grain boundary allotriomorphic ferrite(GBF) + ferrite side plate(FSP) and GBF + intragranular acicular ferrite(IAF),respectively. Inclusions in the HAZ of the Ti-treated steel are TiO_x+ MnS with the size of about 5 μm,while inclusions in the HAZ of the Ti-Mg treated steel are Ti-Mg-O + MnS with the size of about 2 μm. The particle size of the latter tested steel is smaller than that of the former one significantly. The HAZ of the Ti-Mg-treated steel has a lot of fine particles which pin cracks and induce the formation of a large number of IAF,leading to that the impact properties of the Ti-Mg-treated steel is better than those of the Ti-treated steel after experiencing large heat input welding.