What precautions should be taken when using welding materials?

What precautions should be taken when using welding materials? Let’s analyze this together below.

1. Stainless steel welding electrodes are generally available in two types: titanium-calcium and low-hydrogen. Whenever possible, direct current should be used for welding, as this helps prevent electrode redness and promotes deep penetration. Titanium-calcium coated electrodes are not suitable for all-position welding; they are best used for flat and fillet welds only. Low-hydrogen coated electrodes, on the other hand, can be used for all-position welding.

2. Stainless steel electrodes must be dried before use. To prevent defects such as cracks, depressions, and porosity, titanium-calcium coated electrodes should be dried at 150–250°C for 1 hour prior to welding, while low-hydrogen coated electrodes should be dried at 200–300°C for 1 hour before welding. Repeated drying is not permitted; otherwise, the coating will easily flake off.

3. Clean the weld joint thoroughly; ensure that the welding electrode does not come into contact with oil or other contaminants, as this can increase the carbon content of the weld and compromise weld quality.

4. To prevent intergranular corrosion caused by overheating, the welding current should not be too high—typically about 20% lower than that used for carbon steel electrodes. The arc length should be kept short, interpass cooling should be rapid, and narrow weld beads are preferable.

5. When incorporating arcs, ensure that no arcs are introduced at unwelded locations. It is recommended to use arc-shaped plates made from welded components or similar materials to guide the arc.

6. Short-arc welding should be used whenever possible. The arc length is typically 2–3 mm; an excessively long arc can easily lead to hot cracking.

7. Welding Pass: Short-arc welding must be used, and lateral weaving is generally not permitted. The purpose is to reduce heat input and the width of the heat-affected zone, enhance the weld’s resistance to corrosion, and decrease the tendency for hot cracking.

8. When welding dissimilar steels, careful selection of welding electrodes is essential to prevent inappropriate hot cracking or embrittlement of the metal caused by high-temperature heat treatment. Electrode selection should be guided by the relevant standards for stainless steel and dissimilar steel welding, and appropriate welding procedures must be employed.

When purchasing welding consumables, it is essential to select electrode types that are specifically suited to the application and, where necessary, to conduct weldability tests. For thick, large welded components with complex geometries and high structural rigidity, the substantial residual stresses generated during welding can readily lead to cracking in the weld seam; therefore, alkaline low-hydrogen electrodes with excellent crack resistance should be chosen. For weldments subjected to relatively low loads and where the weld area is difficult to clean thoroughly, acidic electrodes that are less sensitive to rust, scale, and oil contamination are recommended. When welding conditions restrict the ability to flip the workpiece, electrodes suitable for all-position welding should be selected. Furthermore, when the base metal has a high carbon content or elevated levels of impurities such as sulfur and phosphorus, electrodes with superior crack resistance and gas porosity resistance—such as low-hydrogen electrodes—should be used.

There are also certain soldering materials for which the liquidus temperature of the material must be given special consideration. For example, when performing stepwise brazing of an assembly—i.e., brazing again in the vicinity of a previously brazed joint—the secondary brazing operation must not disturb the primary joint. The way to prevent this is to use a different brazing filler metal, such that the liquidus temperature of the filler metal used for the secondary joint is lower than that of the filler metal used for the primary joint. In this way, during the secondary brazing, the primary joint will not be melted.