ASME SA-266 Grade 3 forgings

What SA-266 Grade 3 is, and what the aliases mean

ASTM A266/A266M covers carbon steel forgings for boilers, pressure vessels and associated equipment. Four grades are defined. They differ mainly in carbon and manganese content, and in the tensile band each has to meet. Grade 3 sits at the top of the family. It permits more carbon than Grades 1 and 2 and considerably more manganese, which buys strength at the cost of ductility and weldability.

ASME adopts the specification into Section II, Part A of the Boiler and Pressure Vessel Code, where it appears as SA-266/SA-266M. For Code construction, order to SA-266 and to the Code edition your vessel is built to. General requirements sit in ASTM A788/A788M: melting, marking, certification, retesting, product analysis tolerances. Where A788 and A266 conflict, A266 governs.

Reading the aliases on an enquiry

Buyers write this grade several different ways. All of the following describe the same material.

One thing to watch: GR II turns up on some older enquiries. That is Grade 2, not Grade 3. Chemistry and tensile band both change, so confirm it before quoting.

Chemical composition

Product analysis is permitted under A788 and can be ordered as Supplementary Requirement S7. With S11 on the order, residual elements are held to Ni 0.25% max, Cr 0.20% max and Mo 0.08% max on heat analysis. Carbon equivalent is calculated under S15 as CE = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15. The ceilings written into S15 cover Grades 1, 2 and 4, so any CE limit for Grade 3 has to be agreed on the order.

Mechanical properties

Transverse testing, hardness and grain size

A common project requirement is 20 J average over three specimens, 16 J minimum on any single specimen, tested at minus 50 C. Those figures come from the purchaser specification. A266 sets no impact values of its own. Tell us the temperature and energy at enquiry stage, because it affects the steelmaking route and the heat-treatment window, not only the test.

Typical physical properties

Physical properties are typical values for plain carbon steel of this composition and are not acceptance criteria. Allowable stresses for Code design come from ASME BPVC Section II, Part D.

Choosing between Grade 1, 2, 3 and 4

The four grades are not interchangeable. The choice is usually settled by wall thickness and by whether the component will be welded into the vessel.

Where a component will be welded into the vessel and thickness allows, engineers often move from Grade 3 to Grade 4. Manganese stays high, carbon drops to 0.30% max, carbon equivalent falls with it, and preheat and post-weld heat treatment get easier to manage.

Materials it is often compared with

These turn up in enquiries as cross-references. None of them is interchangeable with Grade 3 without approval from the purchaser and, on Code work, the Authorized Inspector.

• ASTM A105, carbon steel flanges and fittings. A different product form with its own size limits.
• ASTM A350 LF2, the usual answer when low-temperature impact testing is mandatory rather than supplementary.
• ASTM A516 Gr.70, the plate equivalent, used where a tubesheet is cut from plate rather than forged.
• EN 10222-2 P280GH and P305GH, the European pressure-purpose forging grades. Close in strength, written to a different acceptance scheme.

Heat treatment and delivery condition

After forging and before reheating, forgings are cooled in a controlled way so that transformation completes and no damage occurs. Every A266 forging is then heat treated by one of these routes.

1. Annealing, marked A Softest condition, lowest residual stress.
2. Normalizing, marked N Refines grain and gives uniform properties through the section.
3. Normalizing and tempering, marked NT The usual condition for Grade 3 tubesheets and nozzles.
4. Liquid quenching and tempering, marked S Permitted when agreed between manufacturer and purchaser. Gives the best impact properties in heavy sections.

Tempering is always subcritical and never below 595 C (1100 F). A multiple-stage austenitizing route is also permitted: full austenitize and quench, reheat into the intercritical range to partly re-austenitize, quench again, then temper between 595 C and the lower critical temperature.

Stress relieving after final machining is a frequent customer requirement on large tubesheets and channel covers, and a 640 C tempering floor appears in many project specifications. Neither comes from A266. Write them into the order and we build them into the routing and the heat-treatment chart.

Repair welding is permitted only at the purchaser's option. Where it is allowed, welders and procedures must be qualified to ASME BPVC Section IX. We quote on the basis of no repair welding unless the order says otherwise.

SA-266 Grade 3 forgings we produce

Everything below is open-die forged to drawing at our works in Jiangyin, then heat treated, machined and inspected in house.

• Tubesheets and tube platesTriangular or square pitch, single or double-sided grooving
• Discs and blocksUpset-disc forged, tangential test orientation
• Hubbed flat headsHub tension specimen to Suppl. Req. S8 on request
• Seamless rolled ringsRadial-axial rolled rings for shells and covers
• Girth flanges and cover flangesMachined faces, bolt holes drilled to drawing
• Channel coversPass-partition grooves machined and stress relieved
• Nozzles and nozzle necksLong welding neck and self-reinforced FVC type
• Shells, cylinders and barrelsForged and bored hollow sections
• Sleeves, bushes and bushingsHollow forged, trepanned or bored
• Hollow bars and hubsBored from solid for sound centre condition
• Round bars and shaftsForged and rough-turned, ends faced
• Housings and casingsNear-net forged, machined to finish dimensions

Size and weight capability

Outside these ranges we say so at enquiry rather than after the order. Send the drawing and we confirm the forging route, the achievable reduction ratio, and whether a test prolongation or a separately forged test block is needed.

How the order runs, from enquiry to certificate

1. Drawing review and forging design Reduction ratio, test location and machining allowances are fixed before the ingot is ordered.
2. Steelmaking Electric furnace with ladle refining and vacuum degassing, with enough discard to clear pipe and segregation.
3. Open-die forging Forged as close to finished shape and size as practical, hot-worked throughout.
4. Heat treatment Anneal, normalize, normalize and temper, or quench and temper, on a charted furnace cycle.
5. Rough and finish machining Before or after heat treatment as the route requires. Rough turning and boring sequence to Suppl. Req. S1 where specified.
6. Testing and NDT Tension, hardness, ultrasonic and magnetic particle examination, plus any supplementary tests on the order.
7. Marking, certification and packing Heat number, specification, grade and heat-treatment letter stamped. Certificate issued. Seaworthy packing.

Testing, inspection and the document package

How many tension tests a forging needs depends on its weight and its heat-treatment route, and A266 is specific about it. For annealed, normalized or normalized and tempered forgings at 2,250 kg (5,000 lb) or less at the time of heat treatment, one tension test covers one forging per heat in each heat-treatment charge. Above that weight, every forging is tested. Quenched and tempered work is tighter. Above 4,500 kg (10,000 lb) two specimens are taken 180 degrees apart, and any forging longer than 3.7 m (12 ft) is tested at both ends.

What we supply as standard

• EN 10204 type 3.1 mill test certificate covering heat analysis and, where ordered, product analysis
• Tensile and hardness results, with the test location identified
• Full heat-treatment chart with temperatures, soak times and the cooling medium
• Ultrasonic examination report covering the complete mass of the forging
• Magnetic particle examination report on all accessible surfaces, to ASTM A275/A275M
• Dimensional inspection record against the approved drawing
• Marking record with heat number, specification, grade and the A, N, NT or S condition letter

Third-party inspection

We work regularly with Lloyd's Register, TUV, Bureau Veritas, SGS and DNV. Send the approved Quality Assurance Plan with the order and we run stage and final inspection against it, hold and witness points included, and issue EN 10204 type 3.2 certification.

For hubbed flanges and tubesheets ordered for ASME Code application, A266 recommends calling out Supplementary Requirement S12 of A788 together with S8 of A266. Put both on the purchase order rather than finding the gap at inspection.

Where SA-266 Grade 3 is used

• Shell-and-tube heat exchangers. Tubesheets, channel covers, girth flanges, floating head covers.
• Pressure vessels and reactors. Nozzles, nozzle necks, hubbed flat heads, shell courses.
• Boilers and steam drums. Forged connections, headers and end components.
• Refinery and petrochemical plant. Hydrotreater and separator components in non-sour service.
• Power generation. Feedwater heaters, condenser and moisture separator components.
• Fertiliser, LNG and chemical plant. Exchanger components where impact testing is added under S13.

Buying SA-266 Grade 3 from Jiangyin Jiangnan Metal

Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China. The works sits in the Yangtze delta forging cluster, about two hours from Shanghai port. We forge carbon steel, alloy steel, stainless steel and nickel alloys to drawing. Pressure vessel work in SA-266, SA-105, SA-350 and SA-182 is a regular part of what leaves the shop.

• Forging, heat treatment, machining, NDT and certification run under one roof, so the heat-treatment chart and the UT report come off the same routing.
• We quote from drawings, sketches or a written description, and we tell you the forging route we plan to use.
• Third-party inspection is coordinated on request. EN 10204 3.1 as standard, 3.2 where the order calls for it.
• Export packing and documentation for sea and air freight, with regular shipments to Europe, North America, the Middle East, India and South-East Asia.

On Grade 3 the argument is rarely about chemistry. It is about where the test specimen sits, and whether the section will still make 19% elongation after the tempering cycle the customer has asked for. That gets settled at drawing review.

Forging works engineering team, Jiangyin Jiangnan Metal Co., Ltd.

Frequently asked questions

Sources and how to cite this page

• ASTM A266/A266M, Standard Specification for Carbon Steel Forgings for Pressure Vessel Components, ASTM International. Grades, chemistry, tensile requirements, heat treatment, marking and supplementary requirements.
• ASTM A788/A788M, Standard Specification for Steel Forgings, General Requirements. Melting, marking, certification, retesting and product analysis tolerances.
• ASME Boiler and Pressure Vessel Code, Section II, Part A for the SA-266/SA-266M adoption. Section II Part D for allowable stresses. Section IX for welding qualification.
• ASTM A275/A275M for magnetic particle examination of steel forgings, ASTM A370 for mechanical testing, ASTM E112 for grain size.

Values on this page are taken from the specification for working reference. Order and verify against the current edition of ASTM A266/A266M, or the ASME Code edition your project is built to.