Nickel is an ideal metal structural material for various harsh corrosive environments such as high temperature, high pressure, high concentration or mixed with impurities in chemical industry, petroleum, non-ferrous metal smelting, aerospace, nuclear energy and other industrial fields. Adding Cr, Mo, Cu, W and other corrosion-resistant metal elements to nickel can obtain a nickel-based corrosion-resistant alloy with excellent corrosion resistance. Compared with other welding methods, the use of submerged arc welding has the advantages of higher welding dilution rate, stable arc combustion, smooth weld surface and no arc glare. In the welding of nickel-based corrosion-resistant alloys, there may be problems such as welding hot crack tendency, weld porosity, and intergranular corrosion tendency of welded joints. Therefore, the following aspects should be paid attention to during processing:
1. Welding wire and flux
In order to prevent the occurrence of thermal cracks, a reasonable assembly sequence should be adopted in the process, and a smaller line energy should be selected, but the key issue is to select suitable welding materials. It can use the same welding wire as MIGA welding, and the flux that matches the alloy and base metal must be selected correctly. Commonly used fluxes are IncoFlux44, IncoFlux5 and IncoFlux6. Flux is hygroscopic and should be stored in a dry container.
2. Joint form
Its typical joint form is consistent with the joint form of MIGA welding. The selection of joint form should minimize molten metal, reduce welding deformation and residual stress, and double V-shaped grooves should be selected as much as possible. All kinds of V-shaped or V-shaped backing plate single-sided welding head are suitable for welding plates with a thickness of less than 25mm. U-shaped groove and double U-shaped groove are suitable for plates over 20m or thicker.
3. Cleaning of welding during processing
This process is an extremely important measure to prevent cracks, especially porosity. Dirt and grease can be cleaned with steam degreasing or acetone, paint can be cleaned with alkali and special detergent, and marking ink can be cleaned with methanol.
4. Preheating and heat treatment in advance
Rolled nickel-based alloys generally do not require pre-welding preheating, and post-weld heat treatment is not recommended, but sometimes post-weld heat treatment is required to ensure that intergranular corrosion does not occur during use. For strengthened alloys that have undergone bending, cold drawing or other complex forming, annealing heat treatment must be done after welding. For strengthened nickel-based alloys with complex structures, in order to effectively reduce welding stress, pre-weld preheating is beneficial, but pre-heating cannot replace post-weld heat treatment.
Our company can provide Inconel 625 Flanges, ASTM B164 Monel 400 Bar and Hastelloy C22 Capillary Tube and other nickel-based alloy products in various grades and shapes. If necessary, welcome to contact us by email.
