Arc Welding Operation Solutions

Arc welding operation solutions

In the scope of industrial production, arc welding is widely used, whether it is a construction site or a machinery manufacturing workshop, it is inseparable. However, many front-line workers and purchasing personnel do not know that poor welding quality, weak welding, and easy cracking are usually not technical problems, but caused by wrong selection of welding rods and methods. Metal composition is the core basis for determining the welding plan.

Carbon steel welding depends on the carbon content

When selecting a welding method , how to choose a riveting welding method and welding materials based on the metal composition , the carbon content is the primary consideration. The carbon content of low carbon steel is less than 0.25%. This material has the best welding performance, and ordinary arc welding can easily complete the work. In 2025, more than 70% of welding tasks in the domestic construction steel structure industry will use low carbon steel materials, such as Q235 steel.

When welding medium carbon steel to high carbon steel, special caution is required. Steel with a carbon content exceeding 0.45% is prone to cold cracking and must be preheated to 200 to 300 degrees Celsius before welding. In 2024, a machinery factory in Shandong failed to adjust the process according to the carbon content, causing a batch of drive shaft welding parts to all crack and be scrapped.

Alloy steel must match special welding materials

Elements such as chromium, molybdenum, and nickel exist in alloy steel and will directly affect the strength of the weld. For low-alloy steels like 16Mn, J506 or J507 electrodes must be matched to ensure joint performance. Ordinary J422 welding rod cannot be used as a substitute, otherwise the weld strength will decrease by more than 32%.

When stainless steel is welded, the requirements for metal composition matching are more stringent, and there is a higher degree of severity. The chromium content of 304 stainless steel is 18% and the nickel content is 8%. In this case, A102 or A132 electrodes must be used for welding operations. In 2025, a food equipment factory in Jiangsu used the wrong welding materials, which caused intergranular corrosion in the welds. Eventually, a leakage accident occurred in the entire batch of storage tanks just two months after they were put into use. How to choose riveting methods and welding materials based on metal composition , liquid leakage occurred.

Look at the shape of graphite before welding cast iron

The carbon in cast iron exists in the form of graphite, and the form of graphite determines the difficulty of welding. The graphite in gray cast iron is flake-like, and white structure is easily formed during welding. It cannot be machined after welding. The graphite of ductile iron is spherical, and its weldability is relatively better, but special nickel-based electrodes must be used.

The cold welding method is the most commonly used method when welding cast iron. It does not require preheating, but the welding rod must be Z308 or Z408. In 2024, a foundry in Hebei chose the riveting welding method and welding materials based on the metal composition when repairing a large machine tool bed. Because it did not use nickel-based welding rods, many cracks appeared in the weld bead, and the repair cost tripled.

Non-ferrous metals should be distinguished between aluminum, copper, titanium and magnesium

When welding aluminum alloys, the magnesium and silicon content must be considered. When the magnesium content of the 5052 aluminum-magnesium alloy reaches 2.5%, ER5356 welding wire must be used in the welding process. If ordinary ER4043 welding wire is used, it will cause thermal cracks in the weld. In 2025, there was an auto parts factory in Zhejiang. Due to the wrong welding wire selection, thousands of aluminum alloy brackets had to be reworked.

When welding copper and copper alloys, you should pay attention to the oxygen content. What happens? Red copper refers to the kind of copper with high oxygen content. When it is welded, it is easy to generate pores. In this case, a phosphorus copper electrode or a deoxidized welding wire is needed. When it comes to brass, there are different situations. The zinc contained in brass is prone to evaporation when exposed to high temperatures. This evaporation will produce toxic gases. In view of this, operations must be carried out in an environment with good ventilation.

Dissimilar metal welding follows the low matching principle

When welding different metal materials, the selection of welding materials needs to follow the principle of low matching, that is, the mechanical properties of the welding materials should be close to the base metal on the lower strength side. For example, when welding Q235 steel and stainless steel, the 309 series electrode arc welding operation solution should be selected. This electrode can adapt to the respective thermal expansion coefficients of the two materials at the same time.

Another situation that is particularly prone to electrochemical corrosion is the welding of dissimilar metals. In 2025, there was a shipyard in South China. When welding the hull, the wrong welding materials were used, which caused serious corrosion of the aluminum-steel joints. It only took three months for water leakage to occur. Choosing the correct transition layer welding materials can avoid such problems.

A method to quickly determine metal composition on site

If a spectrometer does not exist, the carbon content can be preliminarily determined by polishing sparks. Steel with streamlined sparks and few forks has low carbon content, while steel with high carbon content has many spark forks and a large amount of explosions. Experienced welders can quickly determine the material type based on the spark shape.

A more accurate method is to use a portable alloy analyzer. The market price of this equipment has dropped to about 20,000 yuan in 2015. It can read the metal composition in three seconds. After a steel structure manufacturing company in Henan introduced this equipment, the rate of welding material selection errors was reduced from the original 12% to less than 1%, saving more than 500,000 yuan in costs due to rework every year.

Have you ever experienced welding quality problems caused by incorrect selection of welding materials in your factory or construction site? Welcome to share your relevant experiences in the comment area, and don’t forget to like it and forward it to more friends who need to choose welding materials.