When welding ferritic stainless steel with carbon steel, it is necessary to consider the respective characteristics of the two materials and select the welding process in a targeted manner, so as to ensure that the welding quality reaches the standard. Let’s take a look at the weldability and process measures of ferritic stainless steel.

Let’s look at the weldability first. During the welding process, due to the effect of the welding heat cycle, the heat-affected zone on one side of the ferritic stainless steel will cause grain growth and cause embrittlement. And as the chromium content in ferritic stainless steel increases and the high temperature residence time prolongs, the embrittlement tendency of welded joints will gradually become more serious. The structure and properties of the uneven mixed zone of the weld on one side of the carbon steel are affected by the concentration of alloying elements, which may produce a hard and brittle martensite structure, thereby reducing the plasticity and toughness of the ferritic stainless steel and causing cracks. tendency. Therefore, the welding performance of these two steels is actually relatively poor.

In order to achieve high-quality welded joints of these two metals, the following necessary measures should be taken in the welding process.

1. For ferritic stainless steel with low chromium content, a special electrode can be used to overlay a transition layer on the side to be welded before welding. It must be preheated before welding, and the preheating temperature is 200- 300℃, and then use corresponding welding rods to weld the transition layer and carbon steel into one body. When welding ferritic stainless steel with high chromium content to carbon steel, in order to prevent hot cracks in the weld, austenitic stainless steel can be used for welding. Materials are welded without preheating under normal circumstances. If preheating is required, the preheating temperature is 150-200°C.

2. Select small heat input for welding parameters, do not swing the electrode and welding gun laterally during the welding process, and use narrow welds.

3. During multi-layer welding, wait for the previous weld to cool to the preheating temperature before welding the next weld. The temperature between lanes should be controlled at 100°C. If the interpass temperature is too high, the weld seam will stay at high temperature for too long, resulting in serious embrittlement.

4. For welded structures with large thickness or stiffness, it is necessary to design reasonable welding joints and groove forms, hoping that the deformation after welding will be small and the welding stress will be small. After each weld or layer of weld is completed, you can gently hammer around the weld with a small hammer to release the welding stress.

5. Tempering treatment should be carried out promptly after welding. In order to make the weld structure uniform and improve the plasticity and corrosion resistance of the weld. The tempering temperature should be controlled below 750°C.

Welding methods such as electrode arc welding, carbon dioxide gas shielded welding and submerged arc welding can be used to weld ferritic stainless steel and carbon steel.