INCONEL690 (UNS N06690/W. Nr.2.4642) is a high Chromel, which has excellent corrosion resistance to many corrosive water media and high temperature atmosphere. 690 alloy not only has corrosion resistance, but also has high strength, good metallurgical stability, and good processing performance. The large amount of chromium content endows the alloy with excellent resistance to oxidizing chemicals and high-temperature oxidizing gases. The high content of nickel endows the ability to resist stress corrosion cracking in chlorine containing environment and sodium hydroxide solution.
The properties of INCONEL690 alloy are suitable for various applications in nitric acid or nitric acid/hydrofluoric acid solutions. For example, exhaust gas reheaters used for nitric acid production and heating, nitric acid/hydrofluoric acid solution heating coils and tanks used for pickling stainless steel and nuclear fuel reprocessing. The resistance of alloy to sulfur-containing gas makes it an attractive material for radioactive waste disposal of vitrification equipment such as Coal gasification unit, burner and vitrification equipment used to treat sulfuric acid duct, furnace petrochemical processing, co flow heat exchanger, incinerator, and glass.
In various high-temperature water, Alloy 690 exhibits low corrosion rate and excellent resistance to stress corrosion cracking. Therefore, 690 alloy is widely used in steam generator tubes, baffles, tube plates, and hardware for nuclear power generation.
The characteristics of Inconel 690 alloy pipes include composition characteristics, physical properties, mechanical properties, welding properties, structural stability, corrosion resistance in various media and Appropriate technology conditions. This article reviews the compositional evolution of Inconel 690 alloy abroad over the years and the role of various constituent elements, with a special emphasis on the possible good effects of a certain amount of nitrogen on the grain control of Inconel 690 alloy, reducing grain boundary chromium depletion, and improving the resistance to intergranular stress corrosion cracking. The manufacturing process of Inconel6 90 alloy is provided, including parameters for smelting, processing, and heat treatment processes. The dissolution and precipitation patterns of carbides in Inconel 690 alloy during solid solution treatment and TT treatment, as well as their impact on service performance, were emphasized.
The influence of various elements on the properties of Incone1690 alloy:
Incone1690 alloy (hereinafter referred to as 690 alloy) is a type of Cr containing approximately 30wt% Austenitic nickel based corrosion-resistant alloy is widely used as a material for heat transfer tubes in nuclear power plant steam generators due to its excellent stress corrosion cracking (SCC) resistance. 690 alloy contains a small amount of S, N, and a small amount of Ti, C and other alloy elements, which are prone to microsegregation during solidification, resulting in harmful phase precipitation, affecting the Hot working performance and corrosion resistance of the alloy. Therefore, in order to further optimize the composition of 690 alloy and improve its comprehensive performance, this article uses optical microscopy (OM), electron probe microanalyzer (EPMA), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) to systematically study the elemental segregation and phase precipitation behavior during the solidification process of nitrogen containing 690 alloy. The effects of melt superheating temperature and melting rate on the evolution behavior of nitrides in 690 alloy were also studied and discussed.
The solidification behavior of 690 alloy with N content ranging from 0.001 to 0.110wt% was studied using the "isothermal solidification quenching method". The results indicate that N element does not affect the liquidus temperature of Alloy 690, but reduces the solidus temperature. When the N content increases from 10ppm to 1100ppm, the solidus temperature decreases from 1362OC to 1354oC. Ti, Cr, Ni, and Fe undergo microsegregation during the solidification process, where Ti and Cr are positively segregated elements while Ni and Fe are negatively segregated elements. As the N content increases, the concentration of Cr in the residual liquid phase increases, while the concentrations of Ti and Ni decrease. However, the effect of N content on Fe concentration is not significant. C and S have a clear tendency of segregation in the final coagulation zone.
The N element affects the types of precipitates formed during the solidification process of 690 alloy. The precipitates in low N content (10-200ppm) 690 alloy are TiN, Ti (C, N), Ti4C2S2, and (Ti, Cr) S, while the precipitates in high N content (300-1100ppm) 690 alloy are TiN, (Ti, Cr) N, CrS, Cr2C, and Cr7C3.
TiN or Ti (C, N) type nitrides are the main solidification precipitates in Alloy 690. As the overheating temperature increases and the melting rate decreases, the volume fraction of micro scale TiN precipitated during solidification significantly decreases. As the overheating temperature increases, the average size of TiN decreases and its morphology changes from regular block like to fine granular. The effect of melting rate on the average size and morphology of TiN is not significant. After homogenization annealing and cold compression deformation, a large amount of submicron scale Ti (C, N) is dispersed and precipitated during the recrystallization annealing process of the 690 alloy solidified sample. The precipitation amount increases with the increase of overheating temperature and decreases with the increase of melting rate. The dispersed sub micron scale Ti (C, N) cannot effectively prevent grain growth, but can improve the strength of the 690 alloy matrix.
Research on Cold Working and Intermediate Heat Treatment Process of Inconel690 Alloy:
The evolution of microstructure and properties of 690 alloy during cold working and intermediate heat treatment was studied. The results showed that the cold rolling deformation, annealing temperature, and holding time all had a significant impact on the grain size and hardness of 690 alloy. The uniformity of grain size after annealing after 30% cold rolling deformation was significantly better than that after 50% and 70% deformation. The suitable intermediate annealing process for 690 alloy was 1060 ℃ × 10min or 1100 ℃ × 3 minutes
Forging method for Inconel690 alloy bars:
The forging method of Inconel 690 alloy bar belongs to the field of metal pressure processing. The raw material of the forging bar is Electro-slag remelting steel ingot, the forging heating temperature is 1200 ℃± 10 ℃, and the heat preservation time of furnace Negage before forging is calculated from the size of the steel ingot. The deformation of billet opening elongation is controlled at 20% -30%, the feeding amount L is controlled within the range of 0.5-0.8h, the final forging temperature is above 950 ℃, and the billet is forged into a square bar with a cross section. After billet opening, the billet is returned to the furnace for heating and heat preservation; The intermediate deformation is applied along the diagonal direction of the cross section of the billet, and the deformation amount is controlled within the range of 20-50%. The feeding amount L is controlled within the range of 0.5-0.8 hours, and the final forging temperature is greater than 900 ℃. The final fire deformation amount is controlled above 35%, and the final forging temperature is greater than 800 ℃. The I-690 alloy rod forged by the present invention has high uniformity of structure, fewer deformation passes, and can effectively reduce production costs.
