Chromium-molybdenum creep-resisting steel for pressure equipment

12CrMo9-10 Forgings (W.Nr. 1.7375, 2.25Cr-1Mo, EN 10028-2)

Published 18 May 2016. Last updated 8 September 2026. Reviewed by the Jiangyin Jiangnan Metal metallurgical engineering team.

Short answer: what is 12CrMo9-10?

EN material number

1.737512CrMo9-10, 12CrMo910

Standard

EN 10028-2Flat products, pressure purposes

Yield ReH, min

355 MPaFlat to t = 250 mm

Tensile Rm

540-690MPa, +NT or +QT

Elongation A, min

18%To t = 250 mm

Impact KV at −20 °C

27 JTransverse, minimum

Chromium

2.0-2.5%Molybdenum 0.9-1.1%

Density

7.85g/cm³ (0.284 lb/in³)

PWHT

690-750°C, mandatory

Single piece

15,000 kgPlant envelope

What 12CrMo9-10 forged products can you buy?

Jiangyin Jiangnan Metal produces 12CrMo9-10 by three routes, chosen by geometry, not by preference. Seamless ring rolling gives rings, shells and girth flanges with a continuous circumferential grain flow, which is what a pressure boundary wants. Open-die forging covers tube sheets, discs, blocks, shafts and heavy sections. Upset forging handles short, large-section hubs, nozzles and flanges. On a Cr-Mo pressure part the forging route usually decides more about the finished cost than the machining rate does, because it decides how much metal is bought and how many reheats the piece needs.

Size ranges are the plant envelope across all grades. Every form is supplied in the +NT or +QT condition, machined rough or finished to drawing, with EN 10204 3.1 or 3.2 certification. Send the finished drawing instead of a billet size: on a heavy-wall Cr-Mo part, choosing ring rolling over a machined solid disc routinely halves the purchased weight.

What is 12CrMo9-10, and why does the grade exist?

Plain carbon steel loses strength quickly above about 400 °C and, in hydrogen at pressure, its carbides are attacked and the steel decarburises and fissures. Adding chromium and molybdenum fixes both problems at once. Molybdenum forms fine, stable carbides inside the ferrite that pin dislocations and slow creep; chromium stabilises those carbides against hydrogen and builds an oxide that resists steam and flue gas. At 2.25% Cr and 1% Mo the combination is strong enough for refinery and boiler service, still weldable, and far cheaper than a 9% chromium steel.

Three properties are what a buyer is actually paying for:

• Creep strength to roughly 550-580 °C. Above about 450 °C the design stress is no longer set by yield strength but by rupture and creep-rate data. This is the temperature band where 2.25Cr-1Mo earns its price over carbon steel and 1Cr-0.5Mo.
• Resistance to high-temperature hydrogen attack. The Nelson curves in API RP 941 put 2.25Cr-1Mo well above carbon steel, which is why it is the standard shell material for hydrocrackers, hydrotreaters and ammonia converters.
• A flat certified strength curve in heavy section. EN 10028-2 gives 12CrMo9-10 a single set of properties (355 MPa yield, 540-690 MPa tensile, 18% elongation) for all thicknesses up to 250 mm, where most grades in the standard step down as section increases.

12CrMo9-10 vs 10CrMo9-10 vs 11CrMo9-10: which one is on your drawing?

These three grades share the 2.25Cr-1Mo chemistry but not the same certified strength, and buyers confuse them constantly. The difference that matters is what happens as section thickness increases. 12CrMo9-10 (1.7375) holds 355 MPa minimum yield right through to 250 mm. 10CrMo9-10 (1.7380) starts at 310 MPa in thin section and falls in five steps to 250 MPa at 150-250 mm. On a 200 mm wall that is a 105 MPa difference in certified yield, more than 40%, between two grades that look almost identical on a chemistry table.

Table compiled by Jiangyin Jiangnan Metal Co., Ltd. from EN 10028-2. Values for 13CrMo4-5 at t ≤ 60 mm vary slightly between editions of the standard; always work to the revision in force at your contract date. 11CrMo9-10 (1.7383) is the third member of the family and is the designation most often met on European forging enquiries. Check which of the three your specification actually names.

What are the equivalents of 12CrMo9-10?

Buyers meet this steel under at least a dozen names, because the 2.25Cr-1Mo family was standardised separately in Europe, the United States, Japan, China and the former Soviet bloc. The designations in Table 2 all describe closely related chemistry, and Jiangyin Jiangnan Metal accepts purchase orders under any of them, issuing a certificate that lists every specification the heat satisfies. They are not, however, interchangeable in their acceptance requirements: the product-form specification decides the test regime, not the chemistry.

Table compiled by Jiangyin Jiangnan Metal Co., Ltd. from published national standards. Cross-references in this family are close but not exact: carbon, silicon, residual limits and heat-treatment requirements differ between specifications, and some ASME grades carry class distinctions that change the certified strength. Always name the governing specification and its revision on the order.

What is the chemical composition of 12CrMo9-10?

The composition below is the EN 10028-2 requirement for grade 12CrMo9-10, material number 1.7375, and it is what we buy raw material against unless the order specifies a tighter band. Chromium and molybdenum carry the creep strength and the hydrogen resistance; the tight limits on phosphorus, sulphur and residuals are what keep the steel tough after years at temperature.

Table compiled by Jiangyin Jiangnan Metal Co., Ltd. from EN 10028-2. Every heat is supplied with a ladle analysis on the mill certificate; product analysis is added on request. For hydrogen and heavy-wall service, add tin, antimony and arsenic to the reported elements. They are not in the standard, but they control the temper-embrittlement factors.

What are the mechanical properties of 12CrMo9-10?

The characteristic feature of 12CrMo9-10 is that its specified properties do not change with section thickness. EN 10028-2 gives one row for the whole range up to 250 mm, in either the +NT or the +QT condition. Most grades in the standard step down as thickness increases; this one does not, and that is why it is chosen for heavy-wall reactor and exchanger parts.

Table compiled by Jiangyin Jiangnan Metal Co., Ltd. from EN 10028-2. Longitudinal impact values are higher than the transverse minima shown. Hardness is indicative, not a specification requirement. Test results on our certificates are independent and traceable to calibrated equipment.

Strength at temperature, and where the design number really comes from

Room-temperature yield is what appears on the certificate. It is almost never what sizes the part. Above roughly 450 °C the allowable stress for 2.25Cr-1Mo is governed by creep, by 100,000-hour rupture strength and by the stress that produces a defined creep rate. That number comes from the pressure equipment code, not from a supplier datasheet.

• Below about 400 °C: design is governed by yield and tensile strength. 12CrMo9-10 behaves like any low-alloy steel here and usually more steel than the duty needs.
• 400-480 °C: the transition band. Short-term properties still matter; creep begins to appear in long-life assessments; hydrogen partial pressure starts to drive the material choice.
• 480-580 °C: the grade's home ground. Creep governs completely. This is hydroprocessing reactor, steam header and reformer territory.
• Above 580 °C: creep strength falls away. Move to 13CrMoV9-10 (1.7703), 12CrMoV12-10 (1.7767) or the 9Cr grade X10CrMoVNb9-1 (P91, 1.4903), which carry roughly 30% more yield in thin section and far better rupture strength.

Use EN 13445, EN 12952/12953, ASME VIII Division 1 or 2, or whichever code governs your equipment, for the allowable stress. Treat every temperature figure on this page as a screening value.

Physical properties

Typical published values for 2.25Cr-1Mo steel, compiled by Jiangyin Jiangnan Metal Co., Ltd. for screening and weight estimation. They are not specification requirements and not design allowables. Where a physical property enters a design calculation, take it from the governing code.

Temper embrittlement: the requirement that has to be on the order before the heat is melted

2.25Cr-1Mo steel loses toughness over years of service in the 340-570 °C range, and no heat treatment applied afterwards can undo it. Phosphorus, tin, antimony and arsenic diffuse to the prior austenite grain boundaries and raise the ductile-to-brittle transition temperature, sometimes by more than 50 °C over a design life. That shift is why heavy-wall hydroprocessing reactors carry a minimum pressurisation temperature: the vessel is fine hot and brittle cold, and the operating procedure has to keep the two apart.

The control is metallurgical and it happens at the melt shop, not the forge. Two composition factors are used:

• J-factor = (Si + Mn) × (P + Sn) × 10⁴, with all elements in weight percent. Typical limits are J ≤ 100 for heavy-wall hydrogen service, J ≤ 180 for less demanding duty.
• X̄ (X-bar) factor = (10P + 5Sb + 4Sn + As) / 100, with elements in ppm, result in ppm. The usual limit is X̄ ≤ 15 ppm. This one governs the weld metal as often as the base metal.
• Step-cooling test to API RP 934-A, which simulates decades of service in a matter of days and reports the transition-temperature shift directly. Required on most new hydroprocessing equipment.

Jiangyin Jiangnan Metal buys the heat against these limits when they appear on the purchase order. They cannot be added later: once a heat is melted with 0.012% phosphorus and 0.015% tin, its J-factor is fixed. This is the single most common reason a 2.25Cr-1Mo forging order has to be re-melted, and it costs the schedule far more than it costs the price.

How is 12CrMo9-10 forged and heat treated?

12CrMo9-10 air-hardens. A 300 mm block left on the shop floor to cool from forging heat will transform to hard, brittle bainite, and it will crack. Sometimes hours later, sometimes on the first machining cut. Everything in the route below follows from that one fact and from the need to keep the grain structure fine enough to pass the impact requirement in transverse direction.

1. Raw material EAF + LF + VD as standard, with ESR remelt where the specification or the section calls for it. Heat number traced, ladle analysis verified, and residuals reported when temper-embrittlement limits apply.
2. Soak 1,150-1,200 °C, held long enough to bring the whole section to temperature. Surface-heating a heavy billet is the usual cause of a burst centre.
3. Forge Finish above roughly 850 °C. Aim for at least 3:1 reduction to break down the cast structure and close centreline porosity; ring rolling gives circumferential grain flow around the pressure boundary.
4. Controlled cooling or isothermal anneal Never free-cool a heavy section. Either transfer hot to a furnace for an isothermal anneal, or slow-cool under control. This step decides whether the part machines or cracks.
5. Normalise 900-960 °C, air cool. For +QT, austenitise 900-950 °C and quench in water or oil with a recorded transfer time.
6. Temper 680-750 °C, holding roughly one hour per 25 mm of ruling section, then cool in still air. Temper below A_c1 (about 790 °C) with margin.
7. Simulated PWHT on test coupons Coupons are given the same number of PWHT cycles and the same total holding time the fabricator will apply, so the certified properties are the properties the vessel will actually have.
8. Machine Rough or finish to drawing, with in-process dimensional records and stress relief between heavy cuts where the geometry needs it.
9. Test and examine Tensile, Charpy V-notch at the specified temperature, hardness, grain size, ultrasonic examination to EN 10228-3 or ASTM A388, magnetic particle examination to ASTM E709 or ISO 9934.
10. Certify EN 10204 3.1 as standard, 3.2 with third-party witness. Marked with heat number, specification and drawing number, then preserved and packed.

Welding, machining and forming 12CrMo9-10

Welding

12CrMo9-10 is weldable, but only with a qualified procedure and never without preheat and post weld heat treatment. The steel air-hardens, so an unpreheated heat affected zone forms hard martensite and bainite that will crack, often days later, once dissolved hydrogen has had time to diffuse to the notch. The practice below is standard for the grade.

• Preheat 200-250 °C, maintained throughout welding, raised at the top of the range for heavy sections and restrained joints.
• Interpass temperature controlled to roughly 350 °C maximum, so the weld metal does not coarsen.
• Matching consumables: E9018-B3 for SMAW, ER90S-B3 for GTAW and GMAW, EB3 wire and flux for SAW. Strict low-hydrogen control: ovens, holding, exposure limits, all documented.
• PWHT at 690-750 °C, mandatory. If PWHT cannot follow immediately, apply a controlled hydrogen bake-out at roughly 300-350 °C before the joint is allowed to cool to ambient.
• For hydrogen service, apply the X̄ limit to the weld metal as well as the base metal, and qualify the procedure with the same number of PWHT cycles the vessel will see.

Machining

Machining is straightforward in the properly tempered condition, comparable to a medium-carbon alloy steel at 160-210 HBW. In an untempered one it is difficult to impossible. If a forging arrives hard, the problem is the heat treatment and not the cutting data. Use rigid setups on thin tube sheets, expect distortion when heavy sections are opened up and locked-in stress is released, and interpose a stress relief between roughing and finishing on tight-tolerance parts.

Drilling tube sheets

A 2,000 mm tube sheet with several thousand holes is its own manufacturing problem. Hole-position tolerance, ligament width, bore finish and squareness all drive whether the bundle will assemble. We drill to the ligament and tolerance stated on the drawing, with H8 bores as our standard where nothing tighter is specified, and we would rather agree the drilling tolerance at enquiry stage than discover it at inspection.

How do 12CrMo9-10 parts fail, and how do you prevent it?

What can Jiangyin Jiangnan Metal forge in 12CrMo9-10?

Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China, employing about 460 people including 9 senior and 32 intermediate engineers. Raw material, forging, heat treatment, machining, testing and inspection are all organised on one site, which is what lets us hold a single thermal history across a set of matched parts, say a tube sheet with its channel cover and girth flanges, instead of splitting them between subcontractors.

Diameter range

80-6,000mm

Single-piece weight

10-15,000kg

Hydraulic press

5,000 tPlus 4,500 t

Open-die hammers

1 / 3 / 5 / 9tonne

Shaft length

≤ 8,000mm

Condition

+NT / +QTSimulated PWHT available

Certificate

EN 102043.1 standard, 3.2 on request

Lead time

8-14weeks typical

Which standards and certificates apply to 12CrMo9-10 forgings?

How do you specify a 12CrMo9-10 forging order?

Eight items. Get them onto the enquiry and the quotation, the heat treatment and the certificate will all match the equipment code the part is being built into.

1. Name the grade and the material number. Write 12CrMo9-10 / W.Nr. 1.7375. "12CrMo910" alone is routinely filled with 10CrMo9-10, which certifies up to 105 MPa less yield in heavy section.
2. Cite the product-form standard. EN 10028-2 is for plate. For a forging, cite EN 10222-2 or SA-182 F22 / SA-336 F22 / SA-541 Gr 22, and say which governs acceptance.
3. State the delivery condition. +NT or +QT. Heavy sections and toughness-critical parts are normally +QT.
4. Give the ruling section. The greatest thickness heat must travel through. It sets the soak time, the test-piece location and, on some standards, the certified properties.
5. Set temper-embrittlement limits for hydrogen service. J-factor, X̄ and whether step cooling to API RP 934-A is required. These must be on the order before the heat is melted.
6. Define simulated PWHT. How many cycles, at what temperature, for what total holding time. PWHT lowers the strength that can be certified, so the coupons must match the vessel.
7. Define NDE and the acceptance class. "UT per EN 10228-3, quality class 3" is a specification. "Ultrasonic test" is not.
8. State certificate, quantity, Incoterm and destination. EN 10204 3.1 or 3.2 with a named inspection body, plus required date and delivery term.

Drawing callout you can copy

MATERIAL:      12CrMo9-10 / W.Nr. 1.7375 (2.25Cr-1Mo)
SPECIFICATION: EN 10222-2 for forgings  (or SA-336 F22 / SA-182 F22 Cl.3
               / SA-541 Gr.22 - state which governs acceptance)
               Chemistry to EN 10028-2 Table 1, grade 12CrMo9-10
CONDITION:     +QT  quenched and tempered.  Austenitise 900-950 deg C,
               quench, temper 680-750 deg C, 1 h per 25 mm ruling section
RULING SECT.:  ______ mm  (state; test piece at mid-thickness, transverse)
SIMULATED PWHT ON TEST COUPONS:  ___ cycles at 705 deg C +/-15,
               ___ h total holding time, heating/cooling <= 55 deg C/h
               above 300 deg C
MECHANICAL:    ReH >= 355 MPa, Rm 540-690 MPa, A >= 18%
               KV transverse >= 27 J at -20 deg C (3 specimens, avg)
TEMPER EMBRITTLEMENT (hydrogen service only):
               J = (Si+Mn)(P+Sn) x 10^4 <= 100
               X-bar = (10P + 5Sb + 4Sn + As)/100 <= 15 ppm
               Step cooling per API RP 934-A, report dT54 shift
CHEMISTRY:     Report all elements incl. Sn, Sb, As, and Al 0.010-0.040
NDE:           UT per EN 10228-3 quality class 3 (or ASTM A388)
               MT per ASTM E709 / ISO 9934 on all machined surfaces
CERTIFICATE:   EN 10204 3.1  (3.2 with third-party witness if stated on PO)
MARKING:       Heat number, specification, condition, drawing number,
               low-stress stamped or vibro-etched

Seven mistakes buyers make with 12CrMo9-10

1. Writing "12CrMo910" and getting 10CrMo9-10. The names differ by one digit; the certified yield in heavy section differs by up to 105 MPa. Always add the material number 1.7375.
2. Citing EN 10028-2 on a forging. That is the plate standard. The forging route is EN 10222-2 or the ASME equivalents, and it defines the test regime that will actually be applied.
3. Adding temper-embrittlement limits after the heat is melted. J-factor and X̄ are fixed at the ladle. Late limits mean a new heat and a lost quarter of schedule.
4. Not stating the number of PWHT cycles. Every cycle softens the steel. Certifying on one cycle when the fabricator will apply four is how parts pass at the forge and fail at the vessel shop.
5. Ordering a solid block for a ring geometry. Ring rolling typically halves the purchased weight on a shell course or girth flange, and gives a better grain flow around the pressure boundary.
6. Specifying the grade above 580 °C. Creep strength runs out well before oxidation resistance does. Above that, the answer is 13CrMoV9-10 or a 9Cr grade.
7. Leaving the tube-sheet drilling tolerance to be agreed later. Ligament width, hole position and bore finish drive the price and decide whether the bundle assembles. Agree them at enquiry stage.

Ask for a 12CrMo9-10 quotation

Send the drawing, the governing specification and the quantity. We answer within 24 hours with price, lead time and the certificate we will issue. If a web form is inconvenient, write straight to sales@steelforgepieces.com or call 0086-189-2135-9659.

Where is 12CrMo9-10 used?

Two worked examples

Example 1: why the grade choice took 40 mm out of a wall

Given. A shell course for a hot separator, 2,400 mm inside diameter, design temperature 425 °C, design pressure such that the wall works out at 190 mm in a 250 MPa-yield material.

Assessment. At 190 mm section, EN 10028-2 certifies 10CrMo9-10 at 250 MPa minimum yield and 12CrMo9-10 at 355 MPa, a 42% difference between two grades with the same nominal chemistry. Where the code allowable at design temperature scales with the certified yield, the higher-strength grade takes a substantial slice out of the required wall.

Result. On this geometry the wall came down by roughly 40 mm. That is a lower forging weight, a shorter heat-treatment cycle, less weld metal in the circumferential seams and fewer PWHT hours. Together those savings more than offset the price premium on the grade. Do the arithmetic before defaulting to the grade that is easier to buy. Allowable stresses must come from the governing code; this example illustrates the mechanism, not a design.

Example 2: a rolled ring against a machined disc

Given. A girth flange, 1,600 mm OD × 1,150 mm ID × 250 mm thick, in 12CrMo9-10.

Method. Net volume = π/4 × (1.600² − 1.150²) × 0.250 = 0.243 m³. At 7,850 kg/m³ that is about 1,910 kg finished. Rolled as a ring with 25% stock, the forging is roughly 2,390 kg. Machined from a solid forged disc of the same OD and thickness, the input is about 3,950 kg, and some 2,040 kg of Cr-Mo steel goes to swarf.

Result. Ring rolling cuts the purchased weight by about 40% and puts the grain flow around the circumference rather than across it, which is what a pressure boundary wants. On most 12CrMo9-10 enquiries this is the largest single decision on the order, and it is why we ask for the finished drawing instead of a billet size.

Glossary

12CrMo9-10 frequently asked questions

References

1. EN 10028-2, Flat products made of steels for pressure purposes. Part 2: Non-alloy and alloy steels with specified elevated temperature properties. CEN. The standard that defines grade 12CrMo9-10, material number 1.7375.
2. EN 10222-2, Steel forgings for pressure purposes. Part 2: Ferritic and martensitic steels with specified elevated temperature properties. CEN. The product-form standard for forgings in this family.
3. EN 10216-2 (seamless tubes) and EN 10273 (hot-rolled weldable bars) for the other product forms.
4. EN 10204, Metallic products. Types of inspection documents. CEN. Defines the 3.1 and 3.2 certificates.
5. ASTM A182/A182M, A336/A336M, A387/A387M, A541/A541M, A335/A335M and A213/A213M for the corresponding ASTM and ASME 2.25Cr-1Mo product forms.
6. API RP 934-A, Materials and fabrication of 2.25Cr-1Mo, 2.25Cr-1Mo-0.25V, 3Cr-1Mo and 3Cr-1Mo-0.25V steel heavy wall pressure vessels. American Petroleum Institute. Step-cooling and temper-embrittlement requirements.
7. API RP 941, Steels for hydrogen service at elevated temperatures and pressures in petroleum refineries and petrochemical plants. American Petroleum Institute. The Nelson curves.
8. EN 13445 and ASME Boiler and Pressure Vessel Code Section VIII, Divisions 1 and 2, for design allowable stresses; EN 12952 and EN 12953 for water-tube and shell boilers.
9. EN 10228-3 and ASTM A388/A388M for ultrasonic examination of forgings; ASTM E709 and ISO 9934 for magnetic particle examination; ISO 6892 and ASTM E8/E8M for tensile testing; ISO 148 and ASTM E23 for Charpy impact testing; ASTM E112 for grain size.
10. ASM Handbook, Volume 1, Properties and Selection: Irons, Steels and High-Performance Alloys, and Volume 14A, Metalworking: Bulk Forming. ASM International.

Standards are cited by number only. Always work to the revision in force at your contract date. Property values on this page are specification requirements or published typical figures for screening; they are not design allowables. Test results on our certificates are independent and traceable to calibrated equipment.

About the manufacturer, and how to cite this page

Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China, employing about 460 people including 9 senior engineers and 32 intermediate engineers. The plant runs 1 t to 9 t open-die hammers, 4,500 t and 5,000 t hydraulic presses and radial-axial ring rolling, with in-house heat treatment, machining, mechanical testing and non-destructive examination. Alongside 12CrMo9-10 / 1.7375 we forge carbon, alloy and tool steels, the precipitation-hardening and duplex stainless families, and the nickel and cobalt high-temperature alloys. Quality management is certified to ISO 9001:2015; material is supplied with EN 10204 3.1 certification as standard and 3.2 with third-party witness on request.

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