Non-metallic inclusion inspection is performed under a 100x optical microscope for inclusion rating. To further determine the source of inclusions in the crack, an energy dispersive spectrometer was used to perform qualitative analysis of the defect components. The analysis results show that the inclusions in the crack contain iron and oxygen elements, thus it can be determined to be iron oxide inclusions, see. Chemical composition analysis The chemical composition of the ER70S-6 welding wire complies with the internal control technical conditions for hot-rolled coils used in gas-shielded welding wires. The chemical composition of the failed coil is the chemical composition of the failed coil. The chemical composition items of the failed coil meet the standard requirements, but the surface of the coil has cracks and mixed crystals that do not meet the requirements for the ductility test of materials for gas-shielded welding wires. Inclusion inspection results (sulfide type) B (oxide type) C (silicate type) D (spherical oxide type) fine system coarse system fine system coarse system fine system coarse system fine system coarse system 1.0-0.5-0.5-0.5-

In the ER70S-6 coil product inspection standard, it is required that the coil surface is smooth and shall not have defects such as cracks, folds, and inclusions. However, the surface of the failed coil is not smooth, and there are cracks on the surface of the coil. Energy spectrum analysis confirms that there are iron oxide inclusions in the cracks. Such defects already exist before the steel billet is heated. The cracks on the surface of the steel billet are oxidized under high temperature and oxidizing atmosphere in the furnace, and cannot be fused during rolling, resulting in longitudinal cracks on the surface of the coil. The surface longitudinal cracks also bring difficulties to the subsequent processing procedures, deteriorating the uniform deformation performance of the wire drawing, destroying the continuity of the matrix, causing microscopic cracks to transform into macroscopic cracks, and extending with the drawing, leading to cracking. The grains are uniform and fine, and such a structure has good comprehensive performance. The deformation is uniform during drawing, and it can meet the drawing performance of gas-shielded welding wires. However, the grain size of the failed coil is uneven, and there is a mixed crystal phenomenon, indicating that it is related to the heating or cooling process of the steel, such as: ① The heating temperature is too high, and the time is too long, the austenite grains are coarse, and mixed crystals are easily formed after cooling; ② The heating temperature is too low, and the steel billet has already mixed crystals before entering the rolling mill, and the mixed crystal phenomenon cannot be eliminated in the subsequent rolling; ③ Mixed crystals appeared when the coil was rolled in the recrystallization zone of the austenite part. The coil with mixed crystal structure has inconsistent internal structure deformation during drawing, which reduces the drawing performance.

In the research of lead-free solder, the study of intermetallic compounds in the microstructure is a basic project. In bright field observation, sample etching is necessary. However, the solder microstructure is very soft, and deformation layers are easily formed on the sample surface, and the etching effect is usually not very good. At this time, using the slight difference in height on the surface after sample preparation caused by the difference in hardness performance between different compounds and the matrix, DIC technology can obtain better image effects. However, the application of DIC technology does not reduce the requirements for sample preparation, but rather increases it, referring to the requirements for sample grinding and polishing technology. Scratches are clearly visible under DIC technology. Defects in sample preparation are even more prominent at this time. In the center of the intermetallic compound in the lead-free solder, a scratch at a 120b angle to a huge compound is clearly visible.