1. Evaluation of copper plating color and lustre
Due to the fact that there is no uniform evaluation standard of copper color in China, the scoring system is used to characterize the color of copper plating. After copper plating and sizing, the combination of outdoor natural light and indoor microscope observation can be divided into 6 levels.
Grade 0: no replacement reaction occurs. The surface of the welding wire is black or white bright metallic luster. Under the microscope, the iron matrix or coating is broken, and the coverage rate is less than 50%.
Grade 1: the coating is dark brown or slightly copper colored. Under the microscope, the coating is basically intact, and the plating coverage rate is about 80%.
Grade 2: the coating is bright yellow, but the color is white. Under the microscope, the coating is uniform and intact. It is qualified for welding wire plating.
Grade 3: the coating is golden yellow. Under the microscope, the coating is uniform and dense.
Grade 4: the coating is golden and pinkish pink. Under the microscope, the coating is uniform and delicate, which is a good coating state.
Level 5: the coating is near pink, superior to grade 4.
2. Determination of the binding force of the coating
Considering that the welding wire will be rubbed with the nozzle of the welding torch during the use, it is necessary to evaluate the bonding force of the copper plating wire.
Combining force evaluation: the finished product welded wire is bent into the same angle curve, and the same time after repeated friction on the same paper, the copper plating wire is observed.
1 level: the copper layer in the bend is all peeled off;
Level 2: the copper layer is a large number of flaking and elliptical.
Grade 3: the copper layer has a small amount of spalling, showing a round dot, exposing a small amount of iron substrate.
Grade 4: the copper layer is basically not spalling, and the iron wire matrix is basically unexposed.
Grade 5: the copper layer is not spalling completely, and the copper layer is well covered, and the iron wire matrix is completely unexposed.
3. Determination of decopper
The copper plating wire is self winding with its own mandrel. After winding, due to the increase of the lateral extension, if the copper bonding force is not good, the copper coating will be cracked and copper removed.
The results are as follows: when self winding is self winding, it is tightly wound over 5 turns and is observed under 50 times of microscope. If the outer part of the welding wire is wound, the scale is more than 50% or the skimmed cotton rod is wiped, the peeling copper skin is judged to be decopper. On the contrary, the cracks and scales do not exceed 50% and no copper peel is removed after the cotton is polished.
4, determination of antirust property
The welding wire is suspended above the beaker with warm water at 60 degrees centigrade. After 15min, the welding wire is removed and the average value of the corrosion pits on the surface of the 2mm long wire for one week is observed as a criterion.