Welding Methods and Precautions for Cast Iron Components

　　As the name suggests, cast iron pieces are objects made by casting molten iron. Among these, items like swords and other decorative ornaments are primarily produced using this method. Welding of cast iron parts involves joining individual cast iron components together to create entirely new parts. So, let’s now explore the methods and key considerations for welding cast iron pieces.

　　It is well known that iron is an indispensable metal in various fields such as industry, construction, medicine, and science, playing a vital role in societal development. Have you ever heard of the term "cast iron parts"? As the name suggests, cast iron parts are objects precisely created by casting molten iron. Among the most common items made this way are decorative pieces like swords. When it comes to welding cast iron parts, the process involves joining these components together to form entirely new parts. Now, let’s discuss the methods and key considerations for welding cast iron.

　　Welding method for cast iron parts:

　　1. Position the workpiece at an incline to perform uphill welding or semi-vertical welding, reducing the fusion ratio.

　　2. Preheat the area around the bevel before welding to reach a temperature of 200–250°C, reducing the temperature difference between the weld and the workpiece.

　　3. Use cast billet electrodes 308, with diameters of 3.2 mm and 4 mm. Before welding, bake the electrodes at approximately 150°C for 2 hours.

　　4. When welding the 1st, 2nd, and 3rd weld passes, use a D3.2 mm electrode with a current of 90–100 A. For the subsequent two-layer weld, select a D4 mm electrode and apply a current range of 130–160 A. Use direct current with positive polarity.

　　5. After welding each layer and removing slag, heat the area within 200mm around the weld to 300–350°C, hold at this temperature for 30 minutes, and then allow the weld to cool slowly by covering it with asbestos powder.

　　Precautions for welding cast iron parts: On both sides of the bevel, use rapid, non-swinging welding techniques to minimize penetration depth. While welding through the middle, slight tremors may occur—please keep the amplitude of these vibrations as minimal as possible. When repairing thicker workpieces, where the bevel section is larger, employ multi-pass, multi-layer welding. Larger weld cross-sections tend to generate significant shrinkage stresses, increasing the risk of weld cracking or delamination. Therefore, follow a carefully planned welding sequence, utilizing methods such as short-circuit welding, intermittent welding, distributed welding, or segmented backstepping techniques.

　　Short-segment welding involves welding sections approximately 10–40 mm long. Intermittent welding means welding for a certain period, followed by a pause to allow the workpiece to cool down to 50–60°C before proceeding to the next segment—this prevents heat from concentrating in one area. Dispersive welding, on the other hand, entails welding one section at a time, moving sequentially to different areas, which helps minimize temperature differences and reduce residual stresses. Compared to continuous welding, this approach significantly lowers the peak tensile stress during the welding process, thereby effectively preventing the formation of weld cracks. When performing hammering, ensure the temperature remains above 400°C; alternatively, use spherical welding techniques to stretch the weld metal, further relieving stress in the repaired area.

　　The above introduces the welding methods and precautions for cast iron parts. If you'd like to learn more, feel free to contact us anytime! Our company boasts years of experience and eagerly looks forward to having you join us.