The path of the current
When using the correct welding rod diameter, the correct welding current, welding speed will receive the shape, size required to achieve the fastest time.
The selection de depends on the weld metal, the weld position and the type of solder joint. Generally, large deformations are often used for spot welding to take advantage of their high embankment rates.
When welded in a horizontal weld position, welded, welded metal welds tend to run out of welds due to the gravitational pull of the earth, which can be controlled by using a small welding rod to reduce the size. Welding, welding electrodes and welding speeds also help to adjust the size of the welding puddle.
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Welded solder joints need to pay attention to the choice of welding rod diameter as follows:
– The welding rod used for welding the first turns must be of sufficiently small diameter to facilitate the welding of the rod, adjusting the liner shape and avoiding puncturing.
– Large welding rods are used to weld the final layers to take advantage of their deep penetration and high embankment rates.
The experience and skills of the welder play the most important role in the use of welding rods, with the skill of the welder who can control the size of the weld pool.
Welding current: Ih
Manual arc welding can be performed with either AC or DC currents when the electrodes are selected according to their characteristics.
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The type of electric current, polarity and the composition of the cathode coating affect the melting speed of the welding rod. With any type of welding rod the melting speed is directly related to the thermal energy produced by the arc, which in part burns the base metal, and the rest melts the solder.
– DC current:
DC currents have a more stable arc, smoother metal shatter, and less metallicity due to their unchanged polarity during welding even though the rods are designed for AC.
+ Commonly solder rod is used inverted DCNP it for deep penetration but extremely favorable DCPP has a faster flow rate.
+ DC currents suitable for soldering in vertical, ceiling and welding positions with short arc because DC current does not cause short circuit when the metal shifts to the bridge shape.
However, DC currents often occur due to electromagnetic induction.
AC Current: The AC current for manual arc welding has two advantages: no arc deviation and low cost.
+ No deviation of the arc will result in the choice of more powerful currents, the connection of the working poles, mounting of materials, armor details do not seriously affect the technology.
+ With the same AC power cheaper than DC.
+ Each type of electrode diameter that can be soldered at different current ranges to suit different lengths of base metals and different types of welding electrodes.
+ With the increase of the current, the rate of embankment will increase with each type of welding. This change is shown in the following figure:
The diagram shows the relationship between current intensity and fill speed for welding rods of 4.8mm diameter
For each type of electrodes, the choice of electrodes depends on many factors such as the welding position and type of bonding, the currents are large enough to achieve the flow rate and the porosity. For example, when standing, welded current must be selected at the lowest point in the permissible range.
– The arc length is the distance between the tip of the molten electrode to the surface of the molten melt, which plays an important role in ensuring the quality of the weld.
Metallic melting at the tip of the electrode is shifted to the intermittent weld so that when each drop of liquid metal enters the welding pool, the arc voltage immediately changes even the arc length does not change, However, this change will be limited when the current and arc length are appropriately selected.
– The arc length varies with electrode type, diameter, drug type, current strength and welding position.
– The arc length increases with the use of diameter electrodes and large currents. Often the arc length is not greater than the core diameter of the electrode.
The arc length is too short which causes the arc to be unstable and can cause a short sharply during metal shifting; if too long it will reduce the arc concentration, thus causing a sharp shot. It melts when it moves into a welding pool. Therefore, the performance of the embankment will be reduced, in addition to the ineffective gas and slag protection will cause air and gas in the weld metal.
– When adjusting the arc length requires the welder to have good skills related to understanding, experience, visual perception and ingenuity.
With welding and welding of welding rods according to the welds when welding large diameter electrodes, the welding rod may be lightly flushed to the weld where the arc length is determined by the thickness of the drug layer.