How to Match Thickness of Weld, Diameter of Electrode and Welding Parameters in Hand Arc Welding

Hand arc welding

In order to ensure the welding quality, reasonable process parameters must be selected. The selected welding process parameters are generally referred to as welding process specifications. For example, manual arc welding process specifications include welding current, electrode diameter, welding speed, arc length (voltage) and multi-layer welding layers. The arc length and welding speed are generally controlled by the operator according to the actual situation in operation, and other parameters are determined before welding.

1. Electrode diameter

The diameter of welding rod is selected according to the thickness and position of the weldment. Generally, thick welding rod is used for thick welding and thin welding rod is used for thin welding. The electrodes for vertical, horizontal and upward welding should be finer than those for horizontal welding.

2. Welding current and speed

Welding current is the main factor affecting the quality and productivity of welded joints. Excessive current, rapid metal melting, deep penetration, large metal spatter, while prone to burn through, undercut and other defects; too low current, prone to non-penetration, slag inclusion and other defects, and low productivity. When determining welding current, factors such as electrode diameter, thickness of weldment, joint type and welding position should be taken into account, among which the main factor is electrode diameter. Generally, small current is selected for fine electrode and large current is selected for coarse electrode. When welding low carbon steel, the relationship between welding current and electrode diameter can be determined by the following empirical formulas: in I= (30-60) d, I is welding current (A), D is electrode diameter (mm).

Welding speed refers to the distance that the electrode moves per unit time along the weld length direction, which has a great influence on the welding quality. If the welding speed is too fast, it is easy to produce defects such as shallow penetration, small penetration width and incomplete penetration of the weld; if the welding speed is too slow, the penetration and width of the weld will increase, especially for thin parts, which are easy to burn through.

The general principle of determining welding current and welding speed is: on the premise of guaranteeing the welding quality, as far as possible, to use a larger welding current value, as fast as possible under the premise of guaranteeing penetration and good weld formation, in order to improve productivity.

Important Technology and Parameters of Manual Arc Welding

The diameter of the electrode is mainly determined by the thickness of the weldment, the welding position, the number of bead layers and the form of the joint. When the thickness of the weldment is large, a larger diameter electrode is selected. Large current welding can be used in flat welding, and the diameter of welding rod should be selected accordingly. In cross welding, vertical welding or up welding, the diameter of electrode is smaller because the welding current is smaller than that of flat welding. For multi-layer bottom welding, smaller diameter electrodes are used, and larger diameter electrodes can be used for final receipt.

3. Welding Current

The welding current is mainly determined by the thickness of the weldment, the type of the joint, the welding position, the type of the electrode and the diameter of the electrode.

The welding current is 10%-20% lower than that of flat welding in vertical, horizontal and upward welding. Stainless steel and alloy steel electrodes have high resistance, high thermal expansion coefficient and high welding current. When the welding current is large, the coating of the electrodes will fall off because of redness, which will affect the welding quality. In welding, the welding current should be reduced accordingly.