Oil and natural gas are national strategic reserves. As oil and gas field exploration and production gradually shift to deepwater offshore, deep terrestrial formations, and unconventional replacement resource development, the demand for high-end special steels for oil and gas applications has increased significantly. World Metal Herald and Daye Special Steel, a subsidiary of CITIC Pacific Special Steel Group, jointly launched a special report titled “R&D and Application of High-End Special Steels for Oil and Gas.”
The report explores the achievements in R&D and application of special steels for oil and gas applications in my country, looking to the future. The report aims to safeguard major domestic and international projects and contribute to the sustainable development of the global energy industry.
1.1 Introduction to Boiler and Pressure Vessel Steel Standards
Materials used in domestic petroleum and petrochemical equipment all adhere to boiler and pressure vessel steel standards. The main standards for domestic boiler and pressure vessel steel plates (including steel-steel composite plates), forgings, and pipes are shown in Table 1.
| Category | Standard | Series Standards | Remarks |
| Steel Plate | GB/T 713–2023 | GB/T 713.1 | General |
| GB/T 713.2 | 13 steel grades | ||
| GB/T 713.3 | 7 steel grades | ||
| GB/T 713.4 | 4 steel grades | ||
| GB/T 713.5 | 1 steel grade | ||
| GB/T 713.6 | 8 steel grades | ||
| GB/T 713.7 | 43 steel grades | ||
| Forgings | NB/T 47008–2017 | 23 steel grades | |
| NB/T 47009–2017 | 7 steel grades | ||
| NB/T 47009–2017 | 28 steel grades | ||
| Heat Exchanger Tubes | NB/T 47019–2019 | NB/T 47019.1 | General |
| NB/T 47019.2 | 16 steel grades | ||
| NB/T 47019.3 | 28 steel grades | ||
| NB/T 47019.4 | 4 steel grades | ||
| NB/T 47019.5 | 22 steel grades | ||
| NB/T 47019.6 | 5 steel grades | ||
| NB/T 47019.9 | 14 steel grades | ||
| Pipes | GB/T 13296–2023 | 31 steel grades | |
| GB/T 5310–2023 | 25 steel grades | ||
| Clad Plates | NB/T 47002 | Steel-steel composite |
With the continuous improvement of the performance indicators of boiler and pressure vessel steel, especially the demand for a good balance of strength and toughness, and the reduction of carbon content while maintaining strength, which is beneficial to the weldability of pressure vessel steel, current standards for boiler and pressure vessel steel (such as GB/T713) require the use of external refining processes. For some special materials (such as chromium-molybdenum steel), vacuum degassing is also required. The use of external refining and vacuum degassing technologies for dephosphorization and decarburization significantly reduces the H, O, and N contents in the steel, removes inclusions, improves steel cleanliness, and ensures the excellent overall performance of boiler and pressure vessel steel. There are two main methods for manufacturing steel plates for boilers and pressure vessels: continuous casting, slab rolling, and die casting slab rolling. Both methods require a rolling ratio of at least 3. Currently, most domestic steel mills operate with continuous casting slab opening heights of 320-480mm, producing plates with thicknesses of approximately 150mm or less. For plates thicker than 150mm, some domestic mills use a method that combines ingot forging with slab rolling, enabling production of plates up to 200-250mm thick. 220mm Q345R and 198mm 12Cr2MoR plates produced using this method are already in use in actual projects.
Heat Treatment of Steel Plates
Heat treatment is a crucial process in steel plate production and a key step in determining the microstructure and properties of the plate. The main delivery conditions for boiler and pressure vessel steel plates include hot rolling, normalizing, controlled rolling, quenching and tempering (quenching and tempering), and solution heat treatment (austenitic stainless steel). For most thick plates made from chromium-molybdenum steel and other materials, a normalizing (accelerated cooling allowed) plus tempering heat treatment is used. This heat treatment process ensures hardenability in the core of thick steel plates and achieves uniform microstructure throughout the thickness. Currently, this heat treatment technology is applied to most pressure vessel steel plates. Typically, pressure vessel steel plates are heat-treated offline, but only Q490RW, used in crude oil storage tanks, can utilize online heat treatment technology.
1.2 Technical Level of Domestic Pressure Vessel Materials
From 2000 to 2020, rapid development in the petrochemical and coal chemical industries drove the trend toward larger and more complex pressure vessel products. This period yielded fruitful results in the research, development, and application of high-temperature, high-pressure, and corrosion-resistant materials. Key materials for petrochemical equipment, such as domestically produced CrMo steel thick plates and large, thick-walled forgings, nickel-based alloy NS1402, duplex steel, and 9% Ni low-temperature steel, were successfully developed and applied in engineering projects. Overall, my country’s comprehensive technological level for pressure vessel materials has reached world-leading levels, primarily reflected in the following aspects:
1) Low P and S Content and High Purity
Pressure vessel materials generally require low P and S content and high purity. Most domestic steel mills now utilize off-line refining and vacuum degassing processes, and some also utilize electroslag remelting. These mills can utilize various combinations of smelting methods to produce steel plates and forgings with varying performance characteristics. Furthermore, through process measures such as electromagnetic stirring, soft reduction, and argon protection throughout the steel pouring process, the actual S content can be reduced to 0.001% (wt%) and the P content to below 0.005%. Inclusion content can be controlled to a low level, resulting in minimal variation in composition and performance across the length, width, and thickness of the steel plate. Currently, the P and S content levels for high-end chromium-molybdenum steel and low-temperature nickel alloy steel supplied to petrochemical equipment are: P ≤ 0.005%, S ≤ 0.003%.
2) Excellent comprehensive mechanical properties, and meeting the user’s special additional requirements
Steel used in petrochemical equipment generally has high technical requirements. For certain process applications, designers impose additional material and manufacturing requirements, such as simulated post-weld heat treatment and the provision of 100,000-hour endurance strength data. These additional requirements not only require steel mills to strictly control all process steps, including smelting, rolling, and heat treatment, but also ensure that the material possesses excellent comprehensive mechanical properties. Only in this way can they provide materials that meet both the as-delivered performance specified by the standard and the various mechanical properties specified by the user under simulated conditions. Compared with similar imported materials of the same period, these materials produced by domestic steel mills have reached advanced levels in the global steel industry.
3) Adapting to Material Performance Requirements from Low to High Temperatures
Over the past decade, with the implementation of China’s clean energy policy, domestic cryogenic storage technology for liquefied gases, particularly liquefied natural gas (LNG), has rapidly developed. This has driven advancements in low-temperature steel production technology among domestic steel mills. Currently, 0.5% Ni, 3.5% Ni, 5% Ni, 7% Ni, and 9% Ni nickel-based low-temperature steels, as well as Type 400 high-manganese steel, have all met standards. The quality of some products has reached internationally leading levels, meeting the needs of large-scale cryogenic storage tank construction in my country.
Hydrogenation reactors used in petrochemical equipment operate at temperatures exceeding 400°C for extended periods, placing stringent demands on the material’s high-temperature and long-term durability. The production of materials and equipment for hydrogenation reactors represents the advanced technological level of a country’s manufacturing industry. To date, Chinese steel mills have established the actual production capacity for 2.25Cr-1Mo and 1.25Cr-0.5Mo materials with thicknesses up to 200mm, and have achieved localization of extra-thick chromium-molybdenum steel plates. They can also produce 2.25Cr-1Mo-0.25V forgings with maximum outer diameters of 6800-7500mm, maximum unit weights of approximately 250 tons, and wall thicknesses up to 400mm. China is at the forefront of the world in the production, manufacturing, testing, and engineering application of materials for hydrogenation reactors.
4) Meeting the Diverse Needs for Petrochemical Steel Varieties and Specifications
Petrochemical steels are diverse in variety and specifications, requiring a comprehensive suite of plates, forgings, and pipes (piping, heat exchanger tubes, and pipelines) to meet engineering design requirements. Over the past 20 years, not only have the standards, varieties, and performance of steel plates used for pressure vessels and large-scale atmospheric, low-temperature, and room-temperature storage systems experienced rapid development, but standards for supporting forgings and pipes, as well as blasting and rolled composite plates, have also been updated. The number of carbon steel, low-alloy steel, and stainless steel forgings has reached 58 grades. In 2021, the specialized standard NB/T47019 for heat exchanger tubes was released, covering six types of steel and a total of 89 grades. In 2023, the GB/T 5310 and GB/T 13296 pipe standards were released. These updates demonstrate that my country’s pressure vessel steel portfolio is comprehensive and can meet the needs of upgrading petrochemical steel. My country has also made significant progress in the research and application of long-distance pipeline steel. Pipeline steels such as X60, X65, X70, and X80, produced using microalloying and controlled rolling technologies, are widely used in my country. In particular, domestically produced X80 pipeline steel is being used in the West-East Gas Pipeline II project.
5) The material’s application scope is broader.
Since steel used in petrochemical equipment is subject to high temperatures, high pressures, and corrosive media, comprehensive research is required to assess the material’s high-temperature performance, durability, low-temperature brittle fracture, and corrosion resistance, tailored to the operating environment. This ensures the safety of the equipment during operation. In recent years, domestic steel mills have continuously conducted experimental research in these areas. For example, the high-temperature endurance strength test time for 2.25Cr-1Mo-0.25V forgings and thick plates at 454°C has exceeded 30,000 hours. They are also studying the relationship between temper embrittlement and hydrogen embrittlement of this type of material; the relationship curve between Q345R steel plate thickness, heat treatment status and minimum operating temperature; the critical cracking temperature and concentration of super austenitic stainless steel in a chloride ion environment; the relationship between reversed austenite and low-temperature toughness in 9%Ni steel; and the matching technology between domestic steel plates and welding materials. The implementation of this work not only reflects the steel mills’ emphasis on basic research on steel for petrochemical energy, but also helps users accurately predict potential problems with the materials during use and take corresponding measures. At the same time, it can more accurately provide a wider range of applications and usage conditions for the materials.
2. Future Outlook for Steel in the Petroleum and Petrochemical Industry
2.1 New Material Requirements for Petrochemical Equipment Development
The petrochemical industry is currently undergoing a period of transformation. On the one hand, it will develop towards scale, integration, digitalization, and environmental friendliness. On the other hand, the national “3060” carbon reduction policy is prompting a shift in my country’s energy industry policy towards green energy. Therefore, the development of a new generation of “green energy materials” should be considered on the steel industry’s agenda. The key characteristics of green energy materials are high purity, excellent corrosion resistance, superior weldability, and long-term service life. Current development trends indicate that green energy primarily includes hydrogen energy and related industries, CCUS, and the comprehensive utilization of LNG and liquid ammonia. The traditional petrochemical industry is also gradually transitioning to clean energy. Large-scale green hydrogen is replacing coal-to-hydrogen and natural gas-to-hydrogen production in refineries. Natural gas-to-hydrogen is purified to supply hydrogen to refueling stations. Electric heating is replacing gas and oil-fired heating furnaces in refineries. These green processes are gradually replacing traditional processes. These green processes have significantly different material requirements from traditional refinery processes.
2.2 Overall Considerations for Future Demand for Petrochemical Equipment Materials
Currently, the material quality, variety, and specifications covered by domestic pressure vessel steel standards can meet the demand for petrochemical equipment materials. However, given the challenges of processing low-quality crude oil, applying new processes and technologies, transitioning to green refineries, and rapidly developing new energy industries in my country’s petrochemical industry over the next 5-10 years, there is a need to further improve the quality of current pressure vessel materials. Materials experiencing operational problems should be upgraded and replaced. Research and development of new materials suitable for engineering applications under extreme service conditions of ultra-high and low temperatures, as well as ultra-high pressures, should be expedited. New varieties of high-grade materials (such as nickel-based alloys) should be developed. A new generation of petrochemical equipment materials should be developed that improves strength, reduces wall thickness, and maintains performance. This is primarily reflected in the following aspects.
2.2.1 Product Quality Improvement
1) High strength, excellent weldability, and a good balance of strength and toughness;
2) High-purity material (low levels of impurities such as As, Sn, and Sb);
3) High-cleanliness material (low levels of P, S, H, O, and N);
4) Consistent composition and properties from head to tail of the steel plate;
5) Excellent surface quality of the steel plate.
2.2.2 New Material Development
1) Low-alloy steels with a normalized (allowing for rapid cooling) and tempering temperature of 350-550°C are suitable for future use in low-quality crude oil processing and coal chemical equipment in the petroleum, petrochemical, and coal chemical industries.
2) Nickel-based alloys with a temperature of 500-800°C are suitable for future use in petrochemical equipment operating under ultra-high temperature conditions in the petrochemical industry.
3) High-alloy steels with a temperature of 100°C to -269°C and operating under medium-low or high pressure conditions are suitable for future use in equipment operating under low and ultra-low temperature conditions.
4) High-strength austenitic stainless steels with a strength 2-3 times greater than current austenitic stainless steels are suitable for use in current refinery high-pressure equipment and pipelines, enabling reduced wall thickness and less on-site welding workload.
5) Functional materials for electric heating or energy conversion are suitable for future refineries transitioning from fuel-based to green power-based and environmentally friendly energy sources.
2.2.3 Material Upgrades
1) Research and address the temper brittleness, hydrogen embrittlement, and hydrogen corrosion issues that arise with the long-term use of chromium-molybdenum steel currently used in high-pressure hydrogenation equipment.
2) Address intergranular corrosion damage and chloride ion stress damage in austenitic stainless steel.
3) Apply low-cost, corrosion-resistant (high-sulfur, high-acid) super-austenitic, duplex, and ferritic stainless steels to the petrochemical industry.
4) Apply a comprehensive range of carbon steels and low-alloy steels (such as quenched and tempered steels and materials produced using the TMCP process).
5) Develop high-strength Ni-Mn-N series low-temperature steels that can replace nickel-based low-temperature materials.
2.2.4 High-Grade Nickel-Based Alloy Materials
1) Develop a comprehensive range of nickel-based alloys that can withstand various severe corrosive environments.
2) Develop and apply domestic welding materials for high-end chromium-molybdenum steels, nickel-based alloys, and low-temperature materials that can replace imported ones.
2.2.5 Other Materials
1) New, low-cost materials with constant or low expansion coefficients for low or high temperature conditions;
2) Composite materials of steel and non-metallic materials.
To this end, my country’s steel industry should strengthen basic materials research and develop new materials suitable for petrochemical equipment applications. Furthermore, if my country’s petrochemical equipment industry is to expand internationally, compete with the world’s leading equipment manufacturing industry on the international stage, and integrate into the national development policy of the “Belt and Road Initiative,” it will require even greater technical support from advanced petrochemical materials.
2.3 Development Outlook for Materials for Petrochemical Industry Equipment
2.3.1
New Generation Cr-Mo Steel (High Pressure, Operating Temperatures Above 550°C) for Refining Hydrogenation and Coal Chemicals
Currently, the hydroprocessing reactors in large-scale refinery hydroprocessing units have a maximum diameter of 5800mm and a maximum wall thickness of 350mm. They are manufactured using 2.25Cr-1Mo-0.25V. The heaviest hydroprocessing reactors in China weigh approximately 3000 tons. This heavy equipment presents a series of technical challenges in material smelting, forging, processing, manufacturing, transportation, and installation. To this end, high-end chromium-molybdenum steels with higher strength levels, a good balance of strength and toughness, and superior weldability should be included in the materials R&D plan. Specific requirements include:
1) Strength level of 720-850 MPa;
2) No temper brittleness or hydrogen embrittlement damage;
3) Equipment wall thickness and weight reduced by 20%-30%;
4) Impact energy absorbed at -30°C greater than 200 J.
2.3.2
New Generation of General-Purpose High-Strength Low-Alloy Steels Produced Using the TMCP Process for Large, Medium- and Low-Pressure Equipment and Piping
The increasing size of equipment has led to tower diameters exceeding 8,000 mm, pipeline diameters exceeding 4,000 mm, equipment wall thicknesses exceeding 100 mm, and tower weights exceeding 300-1,000 tons. This has increased material and manufacturing costs exponentially, and has also increased the difficulty of on-site pipeline fabrication (welding, heat treatment, inspection, etc.). The new generation of general-purpose, high-strength, low-alloy steel produced with TMCP, suitable for large-scale medium- and low-pressure equipment and pipelines, holds broad market prospects in pressure vessels and pressure piping. Specific requirements include:
1) General-purpose normalized steel for vessels with a yield strength of 390-420 MPa;
2) TMCP steel for vessels with medium- to high-strength exceeding 490 MPa;
3) Quenched and tempered steel for vessels with a strength of 690 MPa.
International standards such as ASME and the European Union have already incorporated these materials, and GB/T 713 has included some steel grades. By adjusting and optimizing the material smelting process based on established low-alloy steels in China, improving and innovating heat treatment processes, and implementing microalloying treatments, my country has developed a series of medium- and high-strength pressure vessel steels.
2.3.3
A new generation of composite materials, produced using a special, novel rolling process, is capable of being bonded to various corrosion-resistant alloys (stainless steel, titanium, nickel-based alloys, copper, etc.), replacing weld overlays on equipment interior walls.
Currently, domestic rolling cladding technology is maturing. The base layer thickness of rolled clad steel plates ranges from 6 to 200 mm, and the clad layer thickness ranges from 1 to 20 mm. The cladding process involves vacuum lamination and continuous rolling. The room-temperature bond strength of the clad steel plates can exceed 300 MPa, with a 100% bond between the base and clad layers. In the petrochemical industry, these materials can partially replace weld overlay structures for container materials. The application of large-diameter rolled clad pipes can effectively address the corrosion issues associated with natural gas transportation in my country. In this regard, rolled composite steel plates and composite pipes offer promising application prospects:
1) Using a special process, the base material can reach a thickness of 200mm, enabling the production of rolled composite plates with various composite materials for pressure vessels, addressing the environmental impact of explosive composite plates.
2) The composite material can be made of a variety of corrosion-resistant materials, such as stainless steel, nickel-based alloys, titanium, copper, and other alloys, adapting to the diverse corrosive environments of the petrochemical industry.
3) Special processes are used to manufacture rolled composite pipes, addressing the corrosion issues of carbon steel pipes used in natural gas extraction.
4) Seamless composite pipes manufactured using special processes can be used in large-diameter natural gas transmission pipelines exposed to corrosive media.
2.3.4
Development and Application of Super Austenitic Stainless Steel, Low-Carbon and N-Containing Austenitic Stainless Steel, Ferritic Stainless Steel, and Super Duplex Steel
With the deterioration of domestic crude oil processing and the admixture of chlorine-containing crude oil, chloride ion corrosion and salt crystallization corrosion on equipment and pipelines in refineries have seriously jeopardized the long-term safe operation of these facilities. The application of super austenitic stainless steel, ferritic stainless steel, super duplex steel, and other materials in the refining and chemical industry will be elevated to a higher level. Specific considerations for this are:
1) Super austenitic stainless steel offers excellent weldability and corrosion resistance, making it resistant to harsh corrosive environments such as seawater, chloride ions, and high sulfur and acid content. Its strength can reach 1.5 times that of conventional austenitic stainless steel. Using super austenitic stainless steel in equipment and piping can reduce wall thickness and weight by approximately 30%;
2) In recent years, low-carbon, nitrogen-containing austenitic stainless steel has been widely used in the petrochemical industry abroad. The lower carbon content and the addition of nitrogen reduce the intergranular corrosion tendency of austenitic stainless steel, while nitrogen imparts the strength properties of conventional stainless steel. Using this type of austenitic stainless steel can also address the problem of weakened weld joints.
3) Ferritic stainless steel is less widely used in the petrochemical industry due to technical difficulties such as composition control, heat treatment, yield rate, and welding. However, compared with austenitic stainless steel, ferritic stainless steel offers advantages in stress corrosion and chloride ion corrosion resistance. With the continuous development of smelting and heat treatment technologies, ferritic stainless steel will have a promising application prospect.
4) New generation precipitation-hardened stainless steels and cast stainless steels will be used in high-strength and wear-resistant components such as compressor cylinders, pump casings, and agitator shafts in petrochemical plants.
5) In recent years, the use of duplex steels (such as 2205 and 2507) in heat exchangers and pipelines in the petrochemical industry has gradually increased. Super duplex steels offer higher strength, better stress resistance, and better chloride ion corrosion resistance than austenitic stainless steels.
6) Low-alloy duplex steels (such as 2102) have low alloying elements (Ni content 3%-7%) while maintaining the corrosion resistance of austenitic stainless steel. They can replace austenitic stainless steel in the petrochemical industry, effectively reducing project investment.
2.3.5
Research and Application of Next-Generation Cryogenic Materials
Over the past decade, LPG, LNG, and shale gas have gradually replaced coal and other energy resources. Meanwhile, my country’s coal chemical industry is booming. These areas, such as the storage and transportation of LNG and shale gas, and coal chemical equipment and pipelines, have created a huge demand for cryogenic materials. GB/T 713.3 lists four grades of low-alloy steel plates commonly used for low-temperature applications between -40°C and -70°C, GB/T 713.4 lists four grades of nickel-alloy steel plates for use between -100°C and -196°C, and GB/T 713.5 lists one grade of high-manganese steel for use at -196°C. These grades can generally meet the engineering requirements for cryogenic pressure vessels and large-scale cryogenic storage equipment. However, due to the large volume of steel used in large cryogenic storage tanks, the petrochemical and steel industries will need to work together to reduce steel costs, expand the application of high-manganese steel, develop a new generation of low-cost nickel alloy steels, and address the domestication of nickel alloy steel welding consumables. These efforts include:
1) Research and technological development of low-cost 5.5% Ni low-temperature steel;
2) Research and application of high-manganese steel technology with a yield strength of 800 MPa;
3) Improving the yield rate of high-manganese steel plates to significantly reduce steel plate material costs;
4) Development and application of domestic welding consumables for nickel-based low-temperature steels;
5) Research and evaluation of the performance of low-temperature materials.
2.3.6
Research, Development, and Application of a Comprehensive Range of Nickel-Based Alloy Materials Suitable for Different Corrosion-Resistant Environments
Currently, the petrochemical industry uses relatively few domestically produced nickel-based alloys, with over 85% of these materials imported. Future research and development of nickel-based alloy materials for petrochemical applications is crucial to meet the high-alloy material requirements of equipment such as those processing low-quality crude oil, processing chlorinated crude oil, and flue gas desulfurization. These primarily include Inconel 625, 800, 600, 601, 690, 945, Hastelloy C276, C3, C4, Monel 400, Alloy 20, and other plate materials, as well as large-diameter, thick-walled pipes and seamless steel tubes.
2.4 Future Development Outlook for Hydrogen Energy Materials
Driven by China’s “dual carbon” policy, the development of the hydrogen energy industry has entered a fast lane. In the field of hydrogen storage and transportation, efforts are being made to strengthen basic and applied research in hydrogen storage technologies, including liquid hydrogen storage, metal hydrogen storage, organic liquid hydrogen storage, high-pressure gas hydrogen storage, and pipeline hydrogen transmission, to achieve large-scale industrial application as soon as possible. With the continuous expansion of the hydrogen energy industry chain, large-scale industrial applications, cost factors, and adaptability to various design conditions, hydrogen storage and transportation metal materials will gradually move towards industrial applications. Looking ahead to the future of the hydrogen energy industry chain, the development and application of new materials should focus on the following areas:
1) New materials for hydrogen storage equipment that are free of hydrogen embrittlement, microalloyed, have a tensile strength limit of 1000 MPa, and can be welded;
2 1) High-purity, low-hydrogen-embrittlement Cr-Mo steel seamless hydrogen storage cylinders with a tensile strength upper limit of 950-1200 MPa;
2) 300 series and high-strength austenitic stainless steels with excellent impact and weldability at -269°C and a thickness of 10-80 mm without martensitic transformation, for large-scale liquid hydrogen storage;
3) Metal and non-metal composite materials for high-pressure hydrogen storage vessels to reduce weight and manufacturing costs;
4) High-strength nickel-based alloys or precipitation-hardened stainless steels at -269°C, for liquid hydrogen compressors, expander cylinders, pump casings, etc.;
5) Low-cost, high-strength hydrogen pipeline steel and pipeline accessories;
6) Alloy steels with constant expansion or low expansion coefficients at ultra-low temperatures, for liquid hydrogen isolation components, etc.
Conclusion
The research and application of new petrochemical materials cannot be separated from the support and collaboration of the steel industry. With the adjustment and upgrading of my country’s energy industry’s product structure, the pursuit of environmentally friendly petrochemical refineries, the demand for large-scale refining facilities, improved oil product processing quality, and long-term safe operation cycles, coupled with the rapid development of the new energy industry, the demand for materials used in petrochemical equipment will gradually increase. By establishing a systematic standard system for petrochemical materials, improving material application evaluation standards, and enhancing the quality and technical level of petrochemical materials, it is entirely possible to establish a world-leading Chinese “green energy materials” industry chain, encompassing research and development, production, equipment manufacturing, and in-service performance evaluation.
