Arc energy parameter I for determining weld format

2022-07-23
  • Detail

Arc energy parameters that determine weld formation (I)

welding current I, arc voltage U and welding speed VW are the main energy parameters that determine weld formation. These three parameters are often defined as the specification parameters of automatic arc welding in production. In addition, electrode diameter and dry elongation of welding wire, inclination of electrode (welding wire), inclination of workpiece, groove shape and thickness of weldment, electrode type and polarity, protection conditions, composition of base metal and welding wire and trace elements all have certain effects on weld formation

when other conditions remain unchanged, the weld penetration and increase will increase with the increase of welding current, while the weld width will almost remain unchanged (or slightly increase). This is because:

(1) when the welding current increases, the thermal power and arc force of the arc increase, so the volume and depth of the weld pool shall not increase with the current. The experiment shows that under normal arc welding conditions, the penetration is almost proportional to the welding current after the welding wire diameter, protection conditions and droplet transfer form are determined in the next 10 years

(2) with the increase of welding current in MIG welding, the melting amount of welding wire also increases, so the weld height also increases. In case of TIG welding, there is no such effect

(3) this kind of characteristic is that when the current increases, on the one hand, the arc cross section increases slightly, which becomes a factor leading to the increase of melting width; On the other hand, when the arc voltage is constant, the arc length is slightly shortened, the arc stiffness is increased and the arc is submerged into the molten pool, which reduces the sweep range of the arc spot and becomes a factor leading to the reduction of the weld width. Therefore, the actual melt width remains almost unchanged

when other conditions remain unchanged, the arc voltage increases, the weld width increases significantly, and the penetration and increase will decrease slightly. As shown in the figure. This is because the increase of arc voltage means the increase of arc length, which expands the floating range of arc spots and leads to the increase of melting width. From the perspective of energy, the increase of arc power caused by the increase of arc voltage is mainly used for the increase of weld width and the heat loss of arc column. The arc force on the weld pool is dispersed due to the increase of weld width, so the penetration and increase are slightly reduced

it can be seen that during arc welding, current is the main factor determining the penetration, while voltage is the main factor affecting the penetration width. It must be noted that in order to ensure the stability of the arc process, these two parameters have a certain range and are mutually restricted. The range of current will be determined by the diameter of welding wire or tungsten rod, and a certain current must have sufficient arc length, that is, a certain arc voltage, so as to stabilize the arc and have a stable droplet transfer process. High voltage will cause air holes, which is not allowed. When the current is constant, the allowable voltage range is generally small. On the other hand, due to the difficulties in measurement, the arc voltage usually includes the resistance voltage drop of the extended length of the welding wire. Even if the arc works in the flat part of the arc static characteristics, the arc voltage should be larger when the current increases. Therefore, the actual arc voltage is always determined with the welding current

welding speed has obvious effect on penetration and width. 3. Mixing non proportional stress and yield into one. Although both non proportional stress and yield are indicators reflecting the transition state of the material in the elastic stage and plastic stage, when the welding speed is small (for example, the welding speed of single wire submerged arc welding is less than), the penetration increases slightly with the increase of welding speed, and the penetration width decreases. However, when the welding speed reaches a certain value, the penetration depth and width decrease obviously with the increase of welding speed. This effect of welding speed can also be explained from the two aspects of arc heat and force

⑴ when the welding speed is small, the action direction of the arc force is almost vertical downward. With the increase of the welding speed, the arc column tilts back, which is conducive to the flow of the liquid metal in the molten pool to the tail under the action of the arc force, exposing the bottom of the molten pool, which is conducive to the increase of the penetration

⑵ when the welding speed increases, the weld penetration and weld width will decrease from the point of view of heat input and heat conduction

as a result of the above two factors, the former plays a leading role at low welding speed, and the penetration increases slightly with the increase of welding speed. When the welding speed exceeds a certain value, the latter plays a leading role, and the penetration decreases with the increase of welding speed. The weld width and increase always decrease with the increase of welding speed

from the perspective of welding productivity, the faster the welding speed is, the better. Therefore, the section where the welding speed slows down and the penetration decreases has no practical significance. When the weldment penetration requirements are determined, in order to improve the welding speed, the welding current and arc voltage must be further increased, which means that the arc power is increased. Therefore, the selection of 4 raw materials for welding current and welding speed must consider the comprehensive economic effect. In addition, it will be seen below that there is a limit to simply increasing the power to increase the welding speed

Copyright © 2011 JIN SHI