Weld color
The color of the weld oxidation: The material being welded is heated to very high temperatures (about 1000°C) during the welding process. The steel and tin react with the surrounding air to form oxides. These oxides are dark blue along the weld. In the form of a black band, the higher the temperature of the solder joint, the thicker the oxide layer and the darker the color. However, the oxidation only occurs slowly, and the solder joint rapidly cools by transferring heat to the surrounding plate.
If the nitrogen protection device is installed near the outlet of the welding wheel, sufficient nitrogen can prevent the oxidation reaction of hot metal and air. About 50mm away from the welding area of ​​the welding wheel, the temperature of the welding point will be reduced below the oxidation reaction point, so that the appearance of the weld with the same color and tint can be maintained.
When using a nitrogen protection device, the color of the weld is usually related to the nitrogen protection device's regulation and the purity of the nitrogen, not the welding heat of the weld. The thicker the plate to be welded, the faster the welding speed, the less effective the nitrogen protection.
When using copper additional wheels, in this cooling process, the welding copper wire is closer to the inner surface of the weld, which can take away the heat of the weld and shield the surrounding air, so even if no nitrogen protection is used, then Has a partial shielding effect, especially near the ends of the can body.
Due to the use of nitrogen protection and copper wire additions, the color of the weld will change regardless of variations in strength and quality of the weld. Therefore, the quality of the weld cannot be evaluated correctly. Without the use of nitrogen protection devices, the temperature and degree of fusion of the weld seam can be evaluated accordingly. For example: the color of the weld is deepened from blue to black, which may indicate a change in the amount of weld seam overlap. Or there are some welding machine adjustment defects that need to be confirmed by other inspection methods. This shows that the quality of the weld can be visually observed by observing the uniformity of the color of the entire weld.
Defects The notable weld features, which are usually not simply defined as weld defects, are subdivided into end face defects and general defects. Therefore, the quality of the weld ends can be detected using special methods such as: reverse side And rewind testing will be used to reliably confirm the quality of welding in this area.
The weld features listed below will be seriously discussed here:
Trailing FISHTAIL
Short circuit SHORTING
Comma COMMAS
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