Understanding ASTM A516 GR 70 and ASTM A516GR70 for Pressure Vessels
ASTM A516 GR 70 is a carbon steel plate grade engineered for pressure vessels operating at moderate and lower temperatures. Its popularity stems from a robust combination of strength, weldability, and impact toughness that suits boilers, heat exchangers, separators, and storage tanks in oil and gas, power generation, and chemical processing. Typical minimum mechanical properties include a yield strength around 260 MPa (38 ksi) and tensile strength in the 485–620 MPa (70–90 ksi) range, with excellent notch toughness when normalized. In thicker gauges, normalizing heat treatment helps improve through-thickness properties and toughness, especially critical in low-temperature service and vessels subject to cyclic loading.
Designers often specify fine-grained plates with strict control of sulfur and phosphorus to enhance weldability and reduce the risk of lamellar tearing. For sour service or wet H2S environments, supplementary requirements and hydrogen-induced cracking (HIC) testing may be added, while some applications call for vacuum-degassed steel for superior cleanliness. The counterpart designation ASTM A516GR70 (frequently written without spaces) is widely used in project documentation and procurement—both denote the same Grade 70 material per the A516 specification.
Welding of Grade 70 typically uses low-hydrogen processes and consumables to minimize diffusible hydrogen and prevent cold cracking. Preheat is often modest but recommended for thicker sections, and interpass temperature control ensures consistent heat input. Post-weld heat treatment (PWHT) may be mandated by design codes, wall thickness, or service severity to relieve residual stresses. Good fabricability allows rolling, bending, and forming into large vessel shells; quality assurance commonly includes ultrasonic testing, impact testing (Charpy V-notch), and dimensional inspections per design standards like ASME Section VIII.
Applications are diverse: refinery hydrotreaters, amine contactors, and low-temperature separators leverage the material’s balance of strength and toughness. In power plants, deaerators and steam drums rely on ASTM A516 GR 70 due to its reliability under internal pressure. When severe corrosion resistance is required at the wetted surface, Grade 70 bases are frequently clad or weld-overlayed with stainless or nickel alloys, marrying the economics of carbon steel with the durability of corrosion-resistant alloys in a single vessel design.
Austenitic Stainless Sheet and Plate: JIS G4305 SUS304, JIS G4305 SUS316, a240 309s, sa240 317L, a240 316ti, and a240 310s
For sheet and strip in the austenitic family, JIS G4305 SUS304 and JIS G4305 SUS316 define widely used stainless grades. SUS304, comparable to AISI 304, offers the classic 18Cr-8Ni chemistry that blends corrosion resistance, formability, and hygiene—ideal for food processing, architectural cladding, and general fabrication. SUS316 adds 2–3% molybdenum, markedly improving resistance to pitting and crevice corrosion in chlorides, making it a mainstay in marine components, pharmaceuticals, and chemical equipment exposed to halides. In cold-rolled form, both meet tight thickness tolerances and surface finish requirements, with finishes ranging from 2B to BA for demanding aesthetic or hygienic surfaces.
Expanding into plate standards, ASTM/ASME A240/SA240 encompasses heat-resistant and corrosion-resistant variants that solve specialized problems. The low-carbon a240 309s is tailored for high-temperature service; it resists oxidation and thermal fatigue up to elevated temperatures where standard 304 and 316 lose scale resistance. A higher chromium and nickel balance allows 309S to handle thermal cycling in furnace parts, recuperators, and kiln components. For aggressive chloride-bearing media, sa240 317L ups the molybdenum content beyond 316L, boosting pitting resistance equivalent numbers (PREN) and cutting downtime from localized corrosion in brine, pickling, and certain off-shore duties.
Stabilized and high-temperature austenitic options add further nuance. a240 316ti introduces titanium to lock carbon in stable carbides, combating sensitization and intergranular corrosion after welding or prolonged exposure to 450–850°C. This stabilization is invaluable in pressure-retaining pipe spools, exchangers, and exhaust manifolds that see thermal cycling. Meanwhile, a240 310s, with its high nickel and chromium, delivers superior oxidation and scaling resistance, supporting continuous service at very high temperatures where structural integrity and surface condition are critical. These alloys maintain austenitic toughness even at cryogenic temperatures, supporting diverse operating conditions.
Selection considerations span more than corrosion tables. Fabricators weigh work-hardening rates, formability, and weldability of each grade. 304 and 316 are highly formable, suited to deep drawing and complex shapes. Heat-resistant 309S and 310S generally require higher forming forces and careful tool design. Welding procedures emphasize low-carbon “L” or stabilized chemistries to minimize sensitization, with appropriate filler metals (e.g., 308/316/309/310 families) chosen to match base metal chemistry and service conditions. Surface cleanliness after fabrication—through pickling, passivation, or mechanical finishing—restores chromium-rich passive films and maximizes performance against corrosion in service.
Nickel Alloy Excellence: Alloy C276 Plate and Hastelloy C276 Sheet in Corrosive and High-Risk Environments
When environments combine strong chlorides, reducing acids, mixed oxidizing species, or contaminated streams, Alloy C276 (a Ni–Mo–Cr–W superalloy) sets a benchmark. In plate and sheet form, it stands up to hydrochloric and sulfuric acids, hypochlorites, wet chlorine, ferric/ cupric chlorides, and organic acids that often defeat stainless steels. Its low carbon content mitigates carbide precipitation during welding, preserving corrosion resistance in the heat-affected zone. The alloy’s balanced chemistry provides both reducing and oxidizing media resistance, and superior immunity to pitting, crevice corrosion, and chloride stress corrosion cracking compared with standard austenitic grades.
Practical limits and processing know-how matter. Although Alloy C276 retains strength at elevated temperatures, many process engineers cap continuous service near 400–425°C to avoid phase embrittlement that can erode corrosion performance. Forming operations require higher forces than 300-series stainless, but the alloy remains workable with appropriate tooling and intermediate anneals. Welding with matching fillers (ERNiCrMo-4/ NiCrMo-4) sustains full-system corrosion resistance; preheat is usually unnecessary, and interpass control limits heat input. QA often includes corrosion testing per ASTM methods, along with microstructure verification and low-ferrite weld metallurgy for demanding chemical plants.
Typical use cases include flue-gas desulfurization systems, urea and inorganic acid production, pulp and paper bleach plants, pickling lines, and sour gas service where chloride and H2S co-exist. In scrubbers, Alloy C276 linings or solid plate components weather chloride-laden condensates and acidic condensate recycling that would rapidly pit 316L. In bleach plants, resistance to wet chlorine and chlorinated solvents mitigates catastrophic localized attack. The alloy’s premium cost is offset by longer intervals between shutdowns, fewer leaks, and lower risk of environmental incidents—key drivers in total lifecycle cost analyses.
A real-world scenario illustrates the progression of material selection: A chemical absorber initially fabricated from 316L suffered rapid crevice corrosion at bolted joints within months. A retrofit using Hastelloy C276 steel sheet shims and spray zone shields halted attack at crevice interfaces. A subsequent turnaround replaced critical internals with Alloy C276 steel plate, stabilizing corrosion rates near zero under the same chloride-acid blend. Lessons often guide a material hierarchy—starting with JIS G4305 SUS316 or JIS G4305 SUS304 for mild duty, stepping to sa240 317L in harsher chlorides, and reserving C276 for extreme or mixed media. In parallel, carbon steel vessels in ASTM A516GR70 frequently serve as cost-effective pressure boundaries when internally clad with stainless or nickel alloys, creating a hybrid solution that balances mechanical strength, corrosion resistance, and budget constraints.
Novosibirsk-born data scientist living in Tbilisi for the wine and Wi-Fi. Anton’s specialties span predictive modeling, Georgian polyphonic singing, and sci-fi book dissections. He 3-D prints chess sets and rides a unicycle to coworking spaces—helmet mandatory.