La/CeO_2稀土对熔敷金属拉伸断口形貌与力学性能的影响

Influence of La/CeO_2 on Tensile Fracture Morphology and Mechanical Properties of Deposited Metal

钛铁矿型焊条成本低,焊接时电弧稳定,焊缝成形美观、熔渣覆盖度好,熔敷效率较高,对焊缝中的锈、油污等不敏感,但抗裂性能差,影响焊接质量。针对钛铁矿型焊条熔敷金属抗裂性差的问题,将12种不同含量的稀土镧(La)及氧化铈(CeO2)过渡到钛铁矿型焊条药皮中,在螺旋式压涂机上将其压涂成钛铁矿型电焊条。按照国家标准制取试板并截取冲击及拉伸样坯,对12种熔敷金属进行了冲击试验和拉伸试验。采用扫描电镜(SEM)对含La/CeO2稀土的拉伸断口形貌进行观察,用能谱仪(EDS)分析断口夹杂物化学成分组成。结合熔敷金属的宏观力学性能,分析熔敷金属断裂的相关信息。结果表明:不含稀土的熔敷金属拉伸断口韧窝较浅,尺寸小些,熔敷金属抗拉强度、延伸率和-20℃下的冲击功分别是467.9 MPa,27%和27 J。其他加入稀土的断口可见韧窝变大变深,夹杂物尺寸变小。但La和CeO2加入的量要适当,不是越多越好,当La,CeO2在药皮中的含量分别是0.5%和0.1%时,和不加入稀土的配方相比,熔敷金属的抗拉强度提高了6.36%,延伸率提高了25.1%,冲击功提高了54.4%,成本仅提高了6.3%,具有较大的推广价值。

The ilmenite type welding electrode had low cost, stable electric arc during welding, beautiful weld, good slag coverage, higher deposition efficiency, low sensitivity to rust and oil in welding, but it had disadvantage in crack resistance, which could influ- ence the quality of welding. Considering the poor crack resistance of deposited metal in ilmenite type welding electrode, 12 different content types of rare earth La/CeO2 were transferred into electrode coating, then pressured to the type of ilmenite welding electrode on the spiral pressure machine. Test plates were made according to national standards and the specimens of impact and tensile were intercepted, 12 types of the deposited metal were used to the test of impact and tensile. Tensile fracture morphology with I-a/CeO2 was observed through scanning electron microscope（SEM） ; the chemical components of the inclusion on the fractures were analyzed by ener- gy-dispersive spectroscopy （EDS）. Relevant information about the fracture of deposited metal was analyzed, combined with the macro- mechanical properties of the deposited metal. The results showed that the deposited metal tensile fracture without rare earth had smaller and shallow dimples. The tensile strength, elongation and impact energy under -20 ~C of the deposited metal were 467.9 MPa, 27% and 27 J, respectively. Other dimples on the fracture were bigger and deeper while the size of the inclusion was reduced, compared with the formula without rare earth addition. But, the amount of La and CeOz must be appropriate ; it did not mean the more the better. When the amount of La/CeO2 in coating was 0. 5%/0.1%, compared with the formula without rare earths, the tensile strength of deposited met- al improved 6.36%, elongation 25.1%, impact energy 54.4%, but cost only 6.3%, so it possessed great promotional value.