Stainless steel clad steel plate is composed of two different types of steel plates, including cladding (stainless steel) and base layer (carbon steel, low alloy steel). Since there are two base materials of pearlite steel and austenitic steel when welding stainless clad steel, the welding of clad steel plate belongs to the welding of dissimilar steel. Therefore, corresponding process measures should be taken during the welding process to not only meet the strength requirements of the welding structure of the base layer, but also ensure the corrosion resistance of the coating. If the operation is improper, it will have adverse consequences. The specific precautions during welding are as follows :
1, the same kind of welding rod cannot be used to weld stainless composite steel components. For stainless composite steel welding components, it is necessary to meet the strength requirements of the welding structure of the base layer and to ensure the corrosion resistance of the coating. Therefore, the welding of stainless clad steel has its particularity. The base layer and the base layer should be welded with carbon steel and low alloy steel electrodes corresponding to the base layer material, such as E4303, E4315, E5003, E5015, etc.; for the cladding layer, carbon increase should be avoided. Because the carbon increase of the weld will greatly reduce the corrosion resistance of the stainless composite steel components. Therefore, the welding of the cladding and the cladding should choose the electrode corresponding to the cladding material, such as A132/A137, etc.; the welding of the transition layer at the junction of the base layer and the cladding should reduce the dilution effect of carbon steel on the stainless steel alloy composition and supplement the welding process Burning loss of alloy composition. Cr25Ni13 or Cr23Ni12Mo2 type electrodes with high chromium and nickel content can be used, such as A302/A307.
2. For weldments of stainless clad steel plate, the wrong edge should not exceed the allowable value (1mm). Stainless clad steel plates are usually composed of a base layer and a cladding layer with a thickness of only 1.5 to 6.0 mm. Considering that in addition to satisfying the mechanical properties of the components, the stainless composite steel components also need to ensure the corrosion resistance of the coating in contact with the corrosive medium. Therefore, when assembling the weldment, it is required to align the cladding layer as the basis, and the edge of the cladding layer should not exceed 1mm. This is especially important when pairing stainless clad steel plates with different thicknesses. If the misalignment between the cladding layers is too large, the weld at the root of the base layer may melt some of the stainless steel, which increases the metal alloy elements of the weld at the root of the base layer, causing the weld to become hard and brittle, and at the same time, the stainless steel at the butt joint is thinned. Thickness will reduce the service life, affect the weld quality of the cladding layer, and it is difficult to ensure the corrosion resistance of the welded structure.
3, it is absolutely forbidden to weld the transition layer or welding cladding stainless steel with the welding material of the welding base layer: at the same time, prevent the cladding welding material from being misused on the welding seam of the welding transition layer and the base layer.
4. When the base layer welding material is used to weld the layer on the cladding side, a chalk solution should be coated within 150mm on both sides of the groove to protect it to prevent the base layer nugget material from sticking to the stainless steel surface during the welding process. The oxide film on the surface affects the corrosion resistance of the stainless composite steel. Spatter particles that have adhered must be carefully cleaned up.
5. The root weld of the base layer adopts electrode arc welding. In order to reduce the dilution of alloy elements under the condition of ensuring the penetration, the fusion ratio should be minimized. At this time, a small welding current and fast welding speed can be used. Allow lateral swing. The welding of the cladding should choose a small welding heat input, so that the residence time in the dangerous temperature (450 ~ 850℃) area is as short as possible. After welding, cold water can be used for rapid cooling.
6, if the stainless clad steel is found to have delamination defects before welding, welding is not allowed. The delamination must be removed first, repair welding (ie, overlay welding), and welding after repair.
7. Special tools must be used to clean the base layer and both sides of the cladding. The base layer must use carbon steel wire brushes, and the cladding must use stainless steel wire brushes.
Post time: Jan-06-2021