Which is more commonly used, Q245R(HIC) or 16MnR(HIC)?
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Q245R(HIC) is more commonly used than 16MnR(HIC), and has become the preferred material for pressure vessels in wet H₂S corrosion environments. 1. Q245R(HIC): The current preferred material. Driver for standard updates: In accordance with GB 713-2008 and subsequent standards, old grades such as 20R and 16Mng have been unified under Q245R, thereby making it the new generation of steel suitable for use in general-purpose containers. Superior overall performance: While maintaining good weldability and workability, Q245R(HIC) achieves a significant improvement in resistance to hydrogen-induced cracking (HIC) and sulfide stress corrosion cracking (SSCC) through strict control of S≤0.003% and P≤0.015%, as well as calcium treatment processes. Wide range of applications: It is widely used in key equipment such as hydrogenation reactors, desulfurization towers, oil and gas tanks, and liquefied gas cylinders, especially suitable for harsh operating conditions featuring medium to low temperatures, medium to high pressures, and humid H₂S. 2. 16MnR(HIC): A traditional material that is gradually being replaced. It has been widely used in the past: it was a common HIC-resistant steel grade in the petrochemical industry, suitable for equipment such as cyclic hydrogen desulfurization towers and cold high-pressure separators. Limitations become apparent: it has a high Mn content (1.20–1.35%), which facilitates the formation of strip-like MnS inclusions, increasing susceptibility to HIC ； Despite optimization through HIC treatment, its overall purity and microstructural uniformity are inferior to those of Q245R(HIC). Standard elimination trend: As Q345R replaces 16MnR, 16MnR(HIC) is also gradually being replaced by new grades such as Q345R(R-HIC), resulting in a continuous decline in its usage frequency. Conclusion: In the design of new projects and equipment manufacturing, Q245R(HIC) has greater advantages due to its standardized specifications, stable performance, and ample availability, making it the industry’s preferred choice ； 16MnR(HIC) is commonly used in the repair of older equipment or in specific small-batch applications.
Indeed, Q245R(HIC) has seen increasing use in wet hydrogen sulfide environments in recent years. Here are two additional practical tips for material selection for reference: 1. In projects involving sulfur-containing oil and gas, 16MnR(HIC) is more commonly used in applications where the temperature exceeds 200°C, as it maintains better high-temperature strength ； 2. If the project is to be exported to the Middle East, it is recommended to confirm in advance whether the GB713 standard is accepted there; some clients may require the use of ASTM A516 Gr.60/65 along with additional HIC testing. The specific selection still needs to be determined based on the design requirements and the owner’s specifications.
This statement is generally true, but it requires certain prerequisites and limitations: in current domestic design of wet H₂S pressure vessels, Q245R (HIC) has indeed largely replaced 16MnR (HIC) as the standard material, though it is not \"more commonly used under all operating conditions.\" The following explains it from three aspects: grade evolution, performance, standards, and engineering applications. I. Evolution of grades: 16MnR → Q345R; Q245R is a low-carbon container steel. 16MnR: an old grade under the previous national standard (GB 150-1998), corresponding to the new grade Q345R; it is a low-alloy high-strength steel with 1.5% manganese content. Q245R: A new national standard low-carbon container steel per GB/T 713, with lower levels of C and Mn, as well as a lower carbon equivalent (CE≈0.36%～0.37%). 16MnR(HIC): A pure steel specifically designed for HIC/SSCC, based on 16MnR (with S≤0.004% and P≤0.015%), which has now been gradually phased out. Q245R(HIC): A hydrogen-resistant steel specifically designed for Q245R, with S≤0.003%～0.004% and P≤0.015%; it undergoes both HIC/SSCC inspections, as well as normalizing treatment plus heat treatment after simulated welding. II. Key differences in wet H₂S environments (why Q245R (HIC) is more common) 1. Fundamental advantages in resistance to HIC/SSCC: Q245R(HIC) has a low carbon and manganese content, resulting in fewer and smaller MnS inclusions, as well as lower sensitivity to hydrogen-induced cracking ； With a low carbon equivalent, the risks of welding cold cracks and excessive hardness are low (it is easy to ensure that the weld hardness is ≤200HB). 16MnR(HIC): Mn≈1.5%, tends to form elongated MnS particles, and hydrogen easily accumulates to induce HIC ； The carbon equivalent is high (≈0.45%), causing the welding heat-affected zone to harden easily, which increases the risk of SSCC; even with strict control of S/P, this issue is difficult to eliminate. 2. Standards and engineering acceptance: The current standards GB/T 713, NACE TM0284, and AMPP SP2154 all recommend low-carbon, low-manganese HIC-resistant steels, and Q245R (HIC) meets these requirements perfectly. Due to its relatively high SSCC incident rate and narrow welding process window, 16MnR (HIC) has been used in very few new projects over the past decade; it is only employed for the repair and replacement of existing equipment. 3. Cost-effectiveness and workability: Q245R (HIC): It has moderate strength (245 MPa level), good weldability, a high qualification rate, and controllable costs; it is suitable for medium-low pressure and medium-low temperature wet H₂S vessels (such as desulfurization towers, high-pressure separators, and sulfur-containing storage tanks). 16MnR (HIC): It has high strength (345 MPa level), but the cost of resisting HIC is high, the rate of welding repairs is high, and its overall economic efficiency is poor; it is used only in applications with higher pressure/temperature levels where it is necessary to reduce the wall thickness. III. Conclusions and Limitations ✅ In the vast majority of wet H₂S pressure vessels (medium and low pressure, ≤200°C), Q245R (HIC) has completely replaced 16MnR (HIC), becoming the absolute standard for design and procurement. ⚠️ Boundary conditions: In high-pressure (≥10 MPa) or high-temperature (≥250°C) wet H₂S environments, Q345R(HIC) (an upgrade from 16MnR (HIC)) can still be used, but stricter control over HIC/SSCC and hardness is required. In extremely harsh conditions (high H₂S partial pressure + chloride ions), stainless steel composite plates or cladding are used, rather than carbon steel HIC steel. In summary, in conventional wet H₂S pressure vessels, Q245R (HIC) has replaced 16MnR (HIC) as the preferred material due to its reliable crack resistance, ease of welding, and good cost-performance ratio ； Q345R (HIC) is considered only for high-pressure/high-temperature conditions.