Selection and Use Principles of Electrodes

Selection Principle of Welding Electrode

There are many kinds of welding electrodes, each of which has its application scope. Whether the electrodes are selected properly or not has a great influence on welding quality, labor productivity and product cost. So we should pay attention to the following points when choosing welding rod.

(1) Considering the mechanical properties and chemical composition of Weldments

①For the welding of low-carbon steel, medium-carbon steel and low-alloy structural steel, the corresponding electrode can be selected according to its strength grade. Only when the welding structure is rigid and the stress is complex, the electrode with a lower strength than steel should be selected. However, in the case of welds to be tempered after welding, it is necessary to prevent the strength of the weld from being too low and the content of alloy elements in the weld from meeting the requirements.

②When choosing acidic or alkaline electrodes after determining the strength of the electrodes, it mainly depends on the complexity of the specific shape of the welding structure, the rigidity of the components, the bearing capacity of the components, the weldability of the steel and the presence or absence of DC power supply. Generally speaking, alkaline electrodes should be selected for welds with high requirements of plasticity, impact toughness and crack resistance.

③Welding of dissimilar steels of low carbon steel and low alloy high strength steel. Generally, welding rods matching the strength of lower steel should be selected.

(2) Considering the working conditions and service performance of Weldments

①For weldments with specific requirements in working environment, corresponding electrodes should be selected. Such as low temperature steel welding rod, underwater welding rod, etc.

③Pearlite heat-resistant steel is generally selected by welding rods similar to steel composition, or according to the working temperature of the weldment.

(3) Consider simplifying processes, increasing productivity and reducing costs

①Joint XXI or XX2 electrodes should be used for thin plate welding or positioning welding. This kind of electrode is easy to start arc and not easy to burn through weldments.

② On the premise of satisfying the service performance and operation performance of the welding parts, the welding rods with large specifications and high efficiency should be selected.

③ When the performance is basically the same, the electrode with lower price should be chosen as far as possible.

(4) Electrode diameter

In order to improve the productivity, large diameter electrodes should be selected, but too large diameter will cause defects such as lack of penetration or poor weld formation. Therefore, the diameter of the electrode must be chosen correctly. The diameter of electrode is related to the following factors.

① The welding rod with bigger diameter should be selected for the weldment with bigger thickness; on the contrary, the welding rod with smaller diameter should be selected for the thin part.

②The diameter of flat welding rod should be larger than that of other positions; the maximum diameter of vertical welding rod should not exceed 5 mm; the maximum diameter of upright and horizontal welding rod should not exceed 4 mm, which can reduce the downflow of molten metal.

③When the number of welding layers is in multi-layer welding, in order to prevent the root from being impermeable, the first layer of multi-layer welding bead should be welded with a smaller diameter electrode. Later, according to the thickness of the weldment, the larger diameter electrode can be selected for each layer.

When welding multi-layer welds of low carbon steel and 16Mn medium and thick steel plates, excessive thickness of each weld will adversely affect the weld joint, and the thickness of each layer should be no more than 4-5mm.

Instructions for Use of Copper Electrode

Instructions for the use of copper-aluminium electrodes:

1. Operating temperature should be controlled between 420 and 490 C. Welding aids: oxygen and city gas, liquefied gas or acetylene gas.

2. Before welding, the paint, oxide and oil stain on the metal surface must be cleaned up to ensure the welding quality. Because paint and grease will be carbonized when heated, forming a diaphragm on the metal surface, solder can not flow on the diaphragm, and solder can not form a connection on a rusted surface.

3. Copper and aluminium brazing can be lapped, while aluminium and aluminium brazing can be lapped or docked first. Usually, you can simply put one workpiece on top of another. The fit between metal and metal surface is the gap needed for brazing. If the components are complex, special fixtures can be used. When brazing, it is necessary to ensure that they are in the right position, and that they are always in the right position throughout the heating and cooling process.

4. After the workpiece is fixed, the copper-aluminium welding rod can directly heat the workpiece. The welding temperature is about 420-490 C. The metal on the assembly should be heated as evenly as possible. All you need to do is to carefully put the welding wire on the joint. The heated brazing temperature component will melt a part of the welding wire, and the melted welding wire will be immediately absorbed by capillary action and spread over the whole. Connecting area. The flow of solder is very strong, which makes it easy for you to get high quality solder joints.