4、 Welding process and analysis 1 Factors affecting weld shape and performance? (1) Influence of welding process parameters
1) Welding current. When other conditions remain unchanged, the penetration is proportional to the change of welding current. The current is small, the penetration is shallow, and the reinforcement and width are insufficient; Excessive current, large penetration and excessive reinforcement are easy to cause high-temperature cracks.
2) Arc voltage. The arc voltage is proportional to the arc length. When the arc voltage and welding current are the same, if the flux selected is different and the electric field intensity in the arc space is different, the arc length is different. When other conditions remain unchanged, the arc voltage is low, the penetration depth is large, the weld width is narrow, and hot cracks are easy to occur; When the arc voltage is high, the weld width increases and the surplus height is not enough. The arc voltage of submerged arc welding is adjusted according to the welding current, that is, the welding current must maintain a certain arc length to ensure the stable combustion of the welding arc, so the variation range of the arc voltage is limited.
3) Welding speed. The welding speed has an effect on the penetration depth and penetration width. Generally, the penetration depth and penetration width are inversely proportional to the welding speed. The welding speed also has an impact on the weld section shape. Generally, the welding speed is too small, the amount of molten metal is too much, and the weld formation is poor; When the welding speed is high, the amount of molten metal is insufficient and undercut is easy to occur. In actual welding, in order to improve productivity, it is necessary to increase the arc power while increasing the welding speed to ensure the weld quality.
4) Diameter of welding wire. When the welding current, arc voltage and welding speed are constant, the penetration depth is inversely proportional to the diameter of the welding wire, but this inverse relationship decreases with the increase of current density.

Usually, people check the failure causes of the inconsistent flow measured by the electromagnetic flowmeter, and often ignore the cable system between the connecting sensor and the converter. In fact, the failure cases of the connecting cable occurred frequently when the manufacturer went to the site for service debugging or inspection. For example, the following cases are often encountered: (1) cut off the whole attached cable and reconnect it. After one stage of use, moisture is inhaled at the connection and insulation drops; (2) The end of the signal line is not properly handled, and the internal shielding layer, external shielding layer and signal core are short circuited with each other or with the shell; (3) Cables without specified model (or attached); (4) The cable length exceeds the upper limit of the length restricted by the liquid conductivity system; (5) The liquid conductivity is low and the distance between the sensor and the converter is far, so the drive shielded cable is not used as required. Some models of instrument cables have a length of more than 30m, and when the conductivity is less than 10-4S ／ cm, a 2-core dual shielded drive shield layer is required. Among the five cases mentioned above, (3) - (5) only appear in the initial installation and commissioning period, and (2) also appear more in the initial installation and commissioning period.