2. Core Performance Indicators (Solution-Annealed State, Key Inspection Items for Chemical Heat Exchanger Tubes)
The performance of Inconel 690 is designed around chemical high-temperature corrosion resistance and structural strength of heat exchanger tubes, with no excessive hardness requirements, focusing on ensuring toughness, corrosion resistance and high-temperature stability. The typical indicators are as follows:
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Performance Category
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Typical Values (Solution-Annealed State)
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Inspection Standard / Key Chemical Industry Assessment Points
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Room Temperature Mechanical Properties
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Tensile strength ≥655MPa, Yield strength ≥276MPa, Elongation ≥30%, Reduction of area ≥40%
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Ensuring the structural strength of heat exchanger tubes and resistance to fluid erosion and equipment vibration
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600℃ High-Temperature Mechanical Properties
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Tensile strength ≥415MPa, Yield strength ≥205MPa, Elongation ≥25%
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No obvious strength attenuation at high temperature to avoid high-temperature deformation of heat exchanger tubes
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Corrosion Resistance
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1. No intergranular corrosion in sensitized state (qualified by GB/T 4334-2020 Method A/D)
2. High-temperature water corrosion resistance (corrosion rate ＜0.01mm/a on the water side at 600℃)
3. Chloride stress corrosion resistance (no cracks in 3.5%NaCl solution)
4. Dilute acid/alkali corrosion resistance (excellent corrosion resistance in dilute sulfuric acid, nitric acid and alkali solution at room temperature-200℃)
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The core assessment item for chemical heat exchanger tubes, avoiding medium mixing and equipment shutdown caused by tube corrosion and leakage
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Oxidation Resistance
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Oxidation rate ＜0.1mm/a in static air below 800℃, forming a dense Cr₂O₃ oxide film
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Adapted to heat exchange working conditions with oxidizing atmosphere such as high-temperature flue gas and high-temperature steam
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Weldability
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Weldable with the same alloy/316L/Incoloy 825, no intergranular corrosion at welding joints, no post-weld heat treatment required
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A large number of tube sheet welds in chemical heat exchangers, greatly reducing construction difficulty and cost
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Thermophysical Properties
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Thermal conductivity 15.1-23.9 W/(m·K) (20-600℃), Thermal expansion coefficient 13.5-18.0×10⁻⁶/℃
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Moderate thermal conductivity, thermal expansion coefficient matching heat exchanger tube sheets, reducing thermal fatigue stress caused by temperature fluctuations
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3. Core Competitive Advantages (Compared with Commonly Used Heat Exchanger Tube Materials in the Chemical Industry)
Compared with traditional heat exchanger tube materials such as 316L stainless steel, Incoloy 800H and Inconel 600 in the chemical industry, the core advantages of Inconel 690 are reflected in the targeted optimization for chemical high-temperature corrosion resistance:
▶Ultimate intergranular corrosion resistance: Low carbon design + 30% high chromium content, no intergranular corrosion in the sensitized state, solving the pain point of intergranular corrosion leakage of Inconel 600, 800H and other materials in chemical welding/sensitization working conditions;
▶No post-weld heat treatment required: No risk of intergranular corrosion at welding joints, eliminating the need for post-weld solution heat treatment. The construction efficiency of thousands of welding joints on chemical heat exchanger tube sheets is improved by more than 80%, greatly reducing construction costs;
▶Excellent high-temperature water corrosion resistance: The corrosion rate on the high-temperature water side at 600℃ is much lower than other nickel alloys, making it one of the best materials for chemical high-temperature water/steam heat exchange;
▶Stable high-chromium passive film: A dense Cr₂O₃ passive film is formed on the surface, which is not easy to be damaged in chemical corrosion media such as chlorides, sulfides and dilute acids, with outstanding resistance to pitting and crevice corrosion;
▶Strong thermal fatigue adaptability: The thermal expansion coefficient has a good matching with carbon steel/stainless steel tube sheets, able to withstand frequent temperature rise and fall fluctuations in chemical heat exchange, reducing the cracking of welding joints between tube bodies and tube sheets.
4.Customized Services & Quality Assurance (Exclusive for Chemical Heat Exchanger Tubes)
In response to the requirements of high precision, high corrosion resistance and traceability of heat exchanger tubes in the chemical industry, Inconel 690 high-temperature heat exchanger tubes provide full-process customization and strict quality control:
▶Specification customization: Customization of non-standard outer diameter, wall thickness and length is supported, and precise processing can be carried out according to the design drawings of heat exchangers, adapting to various chemical heat exchangers such as shell-and-tube and tube-type;
▶Surface customization: Surface treatments such as pickling and passivation, electropolishing and sandblasting are available. Electropolishing can further improve the smoothness of the inner wall of tubes, reduce scaling and enhance heat exchange efficiency;
▶Strict non-destructive testing: All heat exchanger tubes undergo Eddy Current Testing (ET), Ultrasonic Testing (UT) and Hydrostatic Test (1.5 times the design pressure). Helium leak detection and intergranular corrosion testing can be added for high-end chemical working conditions;
▶Complete quality documents: Each batch of products is accompanied by Material Test Report (MTR), intergranular corrosion test report, non-destructive testing report and heat treatment records, supporting full-process traceability;
▶Complete industry certifications: Certified by ISO 9001, ASME BPVC, PED 97/23/EC, API 5L, meeting the qualification requirements of domestic and foreign chemical projects.
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