Nickel-based alloy Nickel201 material and welding process introduction
Nickel201 material introduction
Nickel 201 alloy is industrially pure forged Ni with good mechanical properties, especially excellent plasticity and toughness; good hot working properties, the optimal hot working temperature is 870 ℃ ~ 1 230 ℃; good ductility, easy to cold work and form, and its behavior is similar In mild steel. Annealing can be carried out in a wide temperature range above the recrystallization temperature. The annealing temperature is 705 ℃ ~ 925 ℃. If the temperature is too high, the crystal grains will easily grow. Nickel 201 alloy is resistant to corrosion and generally maintains a bright metallic luster in indoor atmospheres, corrodes slowly in outdoor atmospheres, and has very low corrosion rates in marine and rural atmospheres. And the C content is very low, and there is no brittleness caused by C or graphite at high temperatures. It is mainly used to process equipment and components such as reducing halogen gases, alkaline solutions, non-oxidizing salts, organic acids, etc. Its service temperature is preferably lower than 315°C during use.
Industrial pure nickel has excellent corrosion resistance in most media, and its resistance to alkali corrosion is second only to silver; it has very strong corrosion resistance to acidic and alkaline organic compounds; it has high strength and plasticity , especially at high temperatures above 800 ℃, it can still maintain excellent thermal stability and thermal strength; it has excellent processing performance in both cold and hot states, and it is a metal material used in various harsh corrosive environments. At the same time, nickel has strong corrosion resistance, and neither strong acid nor strong alkali can react violently with nickel. Therefore, nickel and nickel alloys are widely used in core electronic devices, oil exploration and development, large-scale advanced water-cooled reactors and high-temperature nuclear power plants, aerospace, military industry and other fields.
Nickel201 chemical composition
Nickel201 laser welding process
(1) Under different laser welding process parameters, complete penetration can be achieved, and the weld seam is well formed, the structure is uniform, and the melting width is inversely proportional to power and speed.
(2) The microhardness of the weld is lower than that of the base metal, and the microhardness of the heat-affected zone is higher than that of the base metal. The microhardness value from the weld to the base metal first increases and then decreases.
(3) The tensile test results show that the tensile strength of the welded joint is significantly lower than that of the base material, and changes smoothly. The tensile specimens of the welded joint are all broken at the interface between the weld and the heat-affected zone.
(4) Try to use smaller laser power and lower welding speed for welding, which can reduce the tendency of weld grains to become coarse, improve the mechanical properties of the weld, and thereby improve the strength of the weld.
Nickel201 welding method
Nickel 201 welding methods mainly include electrode arc welding, manual tungsten arc welding, gas metal arc welding and submerged arc welding. Manual tungsten arc welding has been widely used in the welding of nickel-based alloys. It is especially suitable for thin plates, small cross-sections, back covers where the joints cannot be back welded, and structural parts where residual slag is not allowed after welding. Manual tungsten argon arc welding has a strong protective effect and can effectively isolate the surrounding air, making the metallurgical reaction in the welding project simple and easy to control, and providing good conditions for obtaining higher quality welds. The arc is very stable, even under small current conditions. It can still burn stably at low temperature (less than 10 A), and is especially suitable for welding of thin plate materials.
Nickel201 post-weld inspection and surface treatment
(1) After the welded joint is cooled to room temperature, check that there are no pores, slag inclusions, undercuts and other defects on the weld surface.
(2) Use an angle grinder to grind the weld surface reinforcement to be flush with the original weld surface and make the transition to the edge fusion smooth.
(3) No cracks were found in the coloring inspection on and around the weld surface.
Nickel201 welding performance
(1) Nickel 201 has good weldability, equivalent to chromium-nickel austenitic stainless steel. The organizational structure is single-phase austenite, with low thermal conductivity and high expansion coefficient. The welding heat-affected zone has a tendency of grain growth. The plasticity and corrosion resistance of the weld and heat-affected zone will be reduced, and the weld metal is prone to heat formation. Cracks and pores.
(2) The preferred welding method for Nickel 201 is tungsten argon arc welding. The arc of tungsten argon arc welding is stable, it is easy to achieve single-sided welding and double-sided forming, the weld is well formed, and there is no spatter, so it is suitable for thin plate welding. The welding material should be a nickel-based alloy welding wire that has the same chemical composition and mechanical properties as the base metal.
(3) Strictly clean the nickel 201 plate and welding wire before welding. Compared with carbon steel, the groove angle and assembly gap must be increased. The back weld bead must be protected by argon gas. At the same time, the welding line energy should not be too high and the interlayer temperature should not be too high. over 100 ℃.
