Precautions for Monel alloy welding


1.Material selection and manufacturing welding are in accordance with the ASME Boiler and Pressure Vessel Code and ANSI Pressure Pipeline Code .

2. The chemical composition of the metal of the welded parts and welded materials must comply with the provisions of the standard. The base material should be in accordance with the ASTM technical provisions of the relevant articles B165, B164, B127. filler material should be in accordance with ASME A-42 filler material for the specified ER-NiCu-7 or ER-ENiCu-4.

3. The weld bevel and the surrounding surface of the stain (oil ester, oil film, rust, etc.) should be cleaned with a cleaning solution.

4. When the temperature of base material is less than 0℃, it is required to preheat to 15.6-21℃, and the weld bevel of the material is heated to 16-21℃ within 75mm.

5. The weld bevel prefabricated mainly depends on the welding position and the thickness of the material, Monel alloy requires the bevel angle of the weld than other materials, the blunt edge than other materials to be small, for the monel alloy plate thickness of 3.2-19mm, the bevel angle is 40 °angle with a blunt edge 1.6mm, the root gap of 2.4mm, less than 3.2mm weld on both sides to be squarely cut or slightly cut bevel, not cut bevel. The weld sides are first machined by mechanical methods, or other appropriate methods, such as arc gas planing or plasma cutting, arc cutting. Regardless of the method, the side of the weld should be uniform, smooth and burr-free, the bevel shall not have slag, rust and harmful impurities, if there are cracks slag and other defects need to be polished and then carefully checked before welding.

6. The provisions of the parent material plate thickness, the recommended material thickness (4-23mm) up to 19mm allowable weld, other thicknesses can also be welded but require the attachment of a detailed sketch.

7. Welding before the welding rod to dry treatment, drying temperature control at 230 - 261 C.

8. Welding conditions: the surface of the welded parts can not be welded due to rain and moisture, rainy days, windy days can not be open-air welding, unless set up a protective shed.

9. No heat treatment is required after welding.

10. Most of the welding technology is with metal arc welding (SMAW), can also be used gas shielded tungsten arc welding (GTAW), automatic welding is not recommended. If automatic welding is used, then argon arc welding, the use of welding rod does not swing welding process, in order to make the weld metal fluidity performance, can be slightly swing to help the flow of weld metal, but the maximum swing width does not exceed two times the diameter of the welding rod, on the use of SMAW method of welding simple parameters are:Power supply: direct, reverse connection, negative operationVoltage: 18-20VCurrent: 50 - 60AElectrode: generally φ2.4mm ENiCu-4 (Monel 190) electrode

11. Spot welding should be fused at the root of the weld channel.

12. After the weld is formed, no edge is allowed to exist.

13. The butt weld should be reinforced, the reinforcement height should not be less than 1.6mm and not more than 3.2mm, the projection should not be more than 3.2mm, and not more than 3.2mm of the pipe bevel.

14. After welding each layer of the weld, must be weld flux and adhesion with stainless steel wire brush to remove clean, before welding the next layer.

15. Defect repair: When the quality of the weld problem, the application of grinding and cutting or arc gas will be dug out defects until the original metal color, and then re-welded according to the original welding procedures and technical provisions, do not allow the hammering method to close the weld metal cavity or fill the cavity with foreign objects.

16. Carbon steel overlay welding Monel alloy shall use p2.4mm welding rod, because the welded Monel alloy layer should be at least 5mm thick, in order to avoid cracks, should be divided into at least two layers of welding. The first layer is the transition layer of Monel alloy mixed with carbon steel. The second layer above the pure Monel alloy layer, after processing to ensure that there is pure Monel alloy effective thickness layer of 3.2mm, each welded layer to be cooled to room temperature, with a stainless steel wire brush to remove the welding flux before welding on a layer.

17. Thickness greater than 6.35 mm of Monel alloy plate, butt welding to be divided into four or more layers of welding. The first three layers available fine welding rod (φ2.4mm) welding, the last few layers available coarse welding rod (φ3.2mm) welding.

18. Monel alloy welding between the AWS ENiCu-4 welding rod ER NiCu-7 wire, carbon steel and Monel alloy welding with EN NiCu-1 or EN iCu-2 welding rod other provisions and the same as the above terms.

quality control

To ensure the quality of welding, non-destructive testing methods inspection means to control the quality, such as radiation, magnetic particle, ultrasonic, penetration and other inspection means for inspection. All welds should also be inspected for appearance defects, such as surface cracks, biting, alignment and weld penetration, etc. At the same time, the type of welding, weld forming should also be checked. All root welds should be inspected for coloring, and if defects are found, they should be reworked before the remaining welds are inspected.

Post time: Feb-13-2023