ASME SA-266 Grade 4 is a carbon steel forging grade for boiler and pressure vessel components. Its requirements are identical to ASTM A266/A266M Grade 4. The grade is defined by 0.30 % maximum carbon, 0.80 to 1.40 % manganese, and a tensile strength of 485 to 655 MPa. The wider manganese range is what separates Grade 4 from Grade 2. It gives better hardenability, so thick sections such as heavy tubesheets and large channel covers develop their properties through the full wall.
Jiangyin Jiangnan Metal Co., Ltd. is an integrated steel melting and open-die forging works at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China, operating since 1997. Unlike a forging shop that buys billet, this plant melts its own steel, so the chemistry for a SA-266 Grade 4 order is aimed at the forging it will become and the certificate traces back to the melt number. We forge the grade into tubesheets, discs, shells, rolled rings, girth flanges, channel covers and nozzle forgings. The data below is what our engineers work from when quoting it.
Chemical composition
| Element | Symbol | Grade 4 | Grade 2 for comparison |
|---|---|---|---|
| Carbon | C | 0.30 max | 0.30 max |
| Manganese | Mn | 0.80 to 1.40 | 0.40 to 1.05 |
| Phosphorus | P | 0.025 max | 0.025 max |
| Sulfur | S | 0.025 max | 0.025 max |
| Silicon | Si | 0.15 to 0.35 | 0.15 to 0.35 |
| Iron | Fe | Balance | Balance |
Manganese is the only element that differs between the two grades, and it is the reason to specify Grade 4. Product analysis tolerances given in ASTM A266 apply when a check analysis is called for. The specification does not limit carbon equivalent. If your welding procedure needs a CE ceiling, state it on the enquiry. Because the heat is melted here, we can aim the chemistry rather than accept it as delivered.
Mechanical properties
| Property | Grade 4 | Grade 1 | Grade 3 |
|---|---|---|---|
| Tensile strength | 485 to 655 MPa 70 to 95 ksi |
415 to 585 MPa 60 to 85 ksi |
515 to 690 MPa 75 to 100 ksi |
| Yield strength, min, 0.2 % offset | 250 MPa 36 ksi |
205 MPa 30 ksi |
260 MPa 37.5 ksi |
| Elongation in 50 mm (2 in.), min | 20 % | 23 % | 19 % |
| Reduction of area, min | 33 % | 38 % | 30 % |
| Brinell hardness, reference, non-mandatory | 137 to 187 HBW | 121 to 170 HBW | 156 to 207 HBW |
| Property | Grade 4 | Grade 1 | Grade 3 |
|---|---|---|---|
| Elongation in 50 mm, min | 19 % | 20 % | 18 % |
| Reduction of area, min | 25 % | 30 % | 25 % |
Tensile and yield requirements do not change after quenching and tempering. Only the ductility acceptance limits move. Grades 2 and 4 share one column in the ASTM tensile table because they differ in chemistry, not in strength class.
Typical physical properties
| Property | Value |
|---|---|
| Density | 7.85 g/cm³ (0.284 lb/in³) |
| Modulus of elasticity | about 200 GPa (29,000 ksi) |
| Poisson's ratio | 0.29 |
| Thermal conductivity | about 51 W/m·K |
| Austenitic grain size | typically controlled to No. 5 or finer, checked to ASTM E112 |
Physical properties are indicative and are not acceptance criteria under ASTM A266. Use the code-listed allowable stresses in ASME BPVC Section II Part D for design.
Heat treatment
ASTM A266 permits four heat treatment routes. Normalizing and tempering is the usual choice for Grade 4 pressure vessel forgings. Quenching and tempering is used when section thickness or required toughness calls for it.
| Route | Typical practice | When we recommend it |
|---|---|---|
| Annealing | Full anneal, furnace cool | Maximum machinability, low residual stress, thin sections |
| Normalizing | Austenitize, still-air cool | Grain refinement on light to medium sections |
| Normalizing and tempering | Normalize, then temper at 595 °C (1100 °F) or above | Default route for tubesheets, channel covers, shells |
| Liquid quenching and tempering | Water or polymer quench, temper at 595 °C or above | Heavy sections and demanding low-temperature toughness |
- Tempering is carried out below the lower critical temperature and never below 595 °C (1100 °F). Many purchasers specify a floor of 640 °C. We hold whatever your procedure calls for and record it on the chart.
- The works runs 14 heat treatment furnaces. Car-bottom furnaces take work up to 8,000 x 2,000 x 2,000 mm, and two well-type furnaces 15 m deep allow long sections to be quenched vertically without distortion.
- After forging and before reheating for heat treatment, forgings are cooled under control so that transformation completes and no cooling damage occurs.
- Stress relief after final machining is applied when the purchase order or the construction code requires it. This is routine on large tubesheets, where machining releases significant residual stress.
- Every cycle is recorded on a calibrated chart recorder. The chart is issued with the certificate.
Testing, NDT and documentation
Chemical
Optical emission spectrometry to ASTM E415 and infrared carbon and sulphur analysis to ASTM E1019, with positive material identification on request.
Mechanical
Tensile testing to ASTM A370 and ISO 6892 on 600 kN and 300 kN machines, hardness survey, and grain size determination to ASTM E112.
Impact
Charpy V-notch is a supplementary requirement, invoked by your purchase order or by ASME Section VIII Div.1 UG-84. We test to minus 60 °C in our own laboratory. Colder test temperatures are placed with an accredited third-party laboratory.
Ultrasonic
UT covering the complete mass of the forging, to ASTM A388 or EN 10228-3, or to your nominated acceptance standard.
Magnetic particle
MT on all accessible machined surfaces to ASTM E709. Liquid penetrant to ASTM E165 where MT is not practical.
Hydrostatic
Applied where the component and the purchase order call for it, at the agreed point in the manufacturing sequence.
Document package issued with every shipment
- EN 10204 3.1 mill test certificate as standard, 3.2 witnessed on request
- Heat treatment charts
- Chemical and mechanical test reports
- Ultrasonic examination report
- Magnetic particle examination report
- Dimensional measurement record against your drawing
- Traceability from the melt number through forging, heat treatment and machining to shipment
The works holds CCS, BV, DNV, LR and NK classification society approvals. Witnessed inspection is routinely handled with BV, DNV, Lloyd's Register, SGS and TUV, or with your own resident inspector. Stage and final inspection follow the approved Quality Assurance Plan agreed before production starts.
Product forms we forge in SA-266 Grade 4
| Component | Size limit | Set by |
|---|---|---|
| Tubesheets, tube plates, discs, covers | up to 5,000 mm diameter machined | 5,000 mm swing vertical lathe |
| Seamless rolled rings | OD 50 to 6,000 mm | 6 m radial-axial ring mill, 3 m and 1 m mills for smaller sizes |
| Girth flanges, channel covers, cover flanges | up to 5,000 mm diameter | Vertical lathe and ring mill |
| Shafts, round bars, hollow bars | up to 14,000 mm turned length | Horizontal lathe, 15 m well furnace for vertical quench |
| Shells, barrels, cylinders, sleeves, bushings | up to 1,600 mm bore x 10,000 mm | CNC deep-hole drilling machine |
| Blocks, hubs, housings | up to 8,000 x 2,000 x 2,000 mm | Car-bottom heat treatment furnace |
| Nozzles, long welding neck and self-reinforced FVC type | NPS 2 to 48, Class 150 to 2500 | Press and machine shop |
| Single piece weight, any form | 10 kg to 30,000 kg | 60 t maximum heat, 6,300 t press |
Minimum order is 10 kg with no minimum piece count, so a one-off part is quotable. Shape and machining allowance change the practical envelope, so send the drawing and we will confirm against the press, the ring mill and the furnace.
How we make a SA-266 Grade 4 forging
- Melting and refiningElectric arc furnace, ladle furnace and, where low carbon or tight nitrogen control is needed, vacuum oxygen decarburisation. Maximum heat size is 60 tonnes. Chemistry is verified at the furnace against the Grade 4 limits before the heat is released.
- Ingot casting and cuttingCut to a weight calculated from your finished dimensions plus forging and machining allowance.
- Open-die forgingUpsetting and drawing on 6,300 t, 4,000 t and 2,000 t hydraulic presses to break down the cast structure and develop a forging ratio appropriate to the section. Rings are expanded on the radial-axial ring mill.
- Controlled coolingPost-forge cooling to complete transformation and prevent cooling cracks before reheating.
- Heat treatmentNormalizing and tempering, or quenching and tempering, on chart-recorded furnaces.
- Test sampling and mechanical testingTest prolongations removed and tested to the specification, including impact testing when specified.
- Rough or finish machiningTo your drawing, including tubesheet drilling and grooving where required.
- NDT and final inspectionUltrasonic and magnetic particle examination, dimensional check, hardness survey, stamping and third-party sign-off.
- Documentation, preservation and dispatchCertificate package compiled, surfaces preserved, seaworthy packing and marking to your requirements.
Comparable grades and cross-references
| Region and standard | Nearest grade | Notes |
|---|---|---|
| USA, ASTM | ASTM A266/A266M Grade 4 | Same requirements. ASME SA-266 is the code-adopted version |
| Europe, EN 10222-2 | P280GH (1.0426) | Comparable strength class, chemistry and testing differ |
| Japan, JIS G3202 | SFVC2B | Carbon steel forgings for pressure vessels |
| China, NB/T 47008 | 20Mn | Pressure vessel forging grade with comparable Mn range |
| Related ASME and ASTM grades | ASTM A350 LF2, P265GH, P355GH | Different product scope: low-temperature service or plate-derived flange grades |
Do not substitute on the strength of this table. Equivalence must be confirmed by the design engineer against the construction code, because permitted chemistry, mandatory testing and allowable stresses all differ between these specifications.
Other grades we forge
Frequently asked questions
What is the difference between SA-266 Grade 2 and Grade 4?
The tensile requirements are identical. Both sit in the 485 to 655 MPa class with 250 MPa minimum yield. The difference is manganese. Grade 2 allows 0.40 to 1.05 % and Grade 4 requires 0.80 to 1.40 %. Higher manganese raises hardenability, so Grade 4 develops and retains its properties more consistently through thick sections. Specify Grade 4 when the section is heavy or the mid-wall properties matter.
Is SA-266 the same as ASTM A266?
Yes, for practical purposes. SA-266 is the ASME Boiler and Pressure Vessel Code adoption of ASTM A266/A266M, published in Section II Part A. The chemistry and mechanical requirements are the same. Use the SA- designation when the material is being supplied for ASME Code construction.
Why does my drawing say Class 4 instead of Grade 4?
ASTM renamed the Class designations to Grades in the 1998 revision. Class 1 became Grade 1, Class 2 became Grade 2, and so on. A drawing calling for A266 Class 4 and one calling for A266 Grade 4 are asking for the same material. Older drawings and legacy procurement systems still carry the Class wording.
Is Charpy impact testing included as standard?
No. Impact testing is a supplementary requirement under ASTM A266, invoked by your purchase order or by the construction code, for example ASME Section VIII Division 1 UG-84. We run Charpy V-notch to minus 60 °C in our own laboratory on a pendulum machine with a low-temperature bath. Below minus 60 °C the test is placed with an accredited third-party laboratory. State the test temperature and the acceptance energy values on the enquiry so they are built into the quotation.
What is the largest SA-266 Grade 4 forging you can make?
The heaviest single piece is 30 tonnes, worked on 6,300 t, 4,000 t and 2,000 t hydraulic presses and backed by hammers from 750 kg to 5 t. Seamless rings roll to 6,000 mm outside diameter on the 6 m radial-axial mill. Downstream sets the practical limits: discs and tubesheets machine to 5,000 mm diameter on the vertical lathe, shafts to 14,000 mm turned length, and the deep-hole drilling machine bores 1,600 mm by 10,000 mm.
Is there a minimum order quantity?
Minimum order is 10 kg, with no minimum piece count, because the limit is set by weight rather than quantity. A single small part is quotable and so is a one-off large ring. In practice very small parts are grouped into a batch to share furnace and setup time, which is why quantity still affects the unit price.
What certification do you supply?
EN 10204 3.1 mill test certificate as standard, covering chemistry, mechanical results, heat treatment charts, UT and MT reports and a dimensional record. EN 10204 3.2 witnessed by BV, DNV, Lloyd's Register, SGS, TUV or your own inspector is available on request. The works holds CCS, BV, DNV, LR and NK approvals. Because the steel is melted here, traceability starts at the melt number rather than at a purchased billet certificate.
What lead time should I plan for?
Typical lead time is 20 to 60 days from order confirmation. Carbon steel grades such as SA-266 Grade 4 sit at the lower end, because the steel is melted, refined and forged without an intermediate remelting step. Third-party witnessed inspection needs scheduling, so flag it at enquiry stage rather than after the order is placed.
Can you machine the forging to finished dimensions?
Yes. We supply as-forged with machining allowance, rough machined to a proof-machined condition suitable for ultrasonic testing, or finish machined to drawing, including tubesheet drilling, grooving and gasket face preparation. Heat treatment, machining and testing are all carried out on site.
About the manufacturer
Jiangyin Jiangnan Metal Co., Ltd. is an integrated steel melting and open-die forging works in Zhouzhuang Town, Jiangyin City, Jiangsu Province, China, operating since 1997. Carbon, alloy, stainless and duplex grades run through an electric arc furnace, a ladle furnace and vacuum oxygen decarburisation. Steel then moves through the presses, the ring mill, 14 heat treatment furnaces and the machine shop without leaving the site. 460 people work here, including 9 senior engineers, 32 intermediate engineers and 140 technicians.
We work from customer drawings and customer specifications rather than a stock catalogue. A typical SA-266 Grade 4 enquiry is answered with a forging weight calculation, a proposed heat treatment route, a test and inspection plan, a price and a delivery schedule, usually within two working days.
Supplier details
Company: Jiangyin Jiangnan Metal Co., Ltd., integrated melting works and open-die forging factory, established 1997
Address: No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China
Telephone: +86 189 2135 9659
Email: sales@steelforgepieces.com
Website: www.steelforgepieces.com
Products in this grade: tubesheets, discs, blocks, rolled rings, shells,
hubs, sleeves, girth flanges, channel covers, LWN and FVC nozzles
Capability: 60 t maximum heat, 6,300 t press, 6 m ring mill, 30 t maximum single piece
Approvals: CCS, BV, DNV, LR, NK
Certification: EN 10204 3.1 and 3.2 witnessed
Business hours: Monday to Saturday, 08:00 to 17:30 China Standard Time (UTC+8)