10CrMo9-10

1.7380

Low-alloy chromium-molybdenum steel for pressure equipment at elevated temperature · EN 10028-2:2017 — flat products of weldable steels for pressure purposes with specified elevated-temperature properties · EN 10028-1:2017 — general requirements for flat products for pressure purposes

10CrMo9-10 (1.7380) is the EN 10028-2 flat-product grade corresponding to the established 2¼Cr-1Mo class of creep-resistant pressure steel. Its chromium-molybdenum alloying provides substantially better elevated-temperature strength than carbon-manganese pressure steels, while the normalized-and-tempered or quenched-and-tempered condition controls strength and toughness through thickness. Procurement and fabrication must account for product thickness, delivery condition, transverse mechanical properties, cumulative post-weld heat treatment and, where relevant, temper embrittlement or sour-service testing.

1.7380Material number · The unambiguous numerical designation under EN 10027-2.
Approximately 2.25% Cr and 1.0% MoNominal alloy system · Commonly described internationally as a 2¼Cr-1Mo pressure and creep-resistant steel.
Flat products for pressure equipmentStandardized product scope · EN 10028-2 properties must not be applied automatically to tubes, forgings, bars or castings carrying a similar steel name.
Up to 250 mmStandard thickness range · Room- and elevated-temperature properties vary with thickness; the usual delivery condition changes from +NT to +QT as thickness increases.
450–630 MPaRoom-temperature tensile range · The applicable range depends on nominal thickness.
Possible temper embrittlement around 400–500 °CService-related concern · EN 10028-2 provides an optional step-cooling test for CrMo steels where this risk matters.

Overview

Designation system: EN 10027 steel name and steel number
Product forms: Plate, Sheet, Strip, Other flat products within the dimensional scope of EN 10028
Condition: +NT — normalized and tempered, +QT — quenched and tempered
Density: 7.85 g/cm³ (Representative engineering value; density is not a grade acceptance requirement in EN 10028-2.)

What the designation covers

EN 10028-2 defines 10CrMo9-10 as an alloy special steel supplied as flat product for pressure equipment requiring specified elevated-temperature properties. The designation is not itself a complete component specification: EN 10028-1 supplies the general requirements for ordering, manufacture, inspection, sampling, testing, dimensional tolerances, surface condition and internal soundness.

The steel name describes its approximate composition rather than a guaranteed property level. “10” indicates roughly 0.10% carbon, while the chromium and molybdenum indices correspond to approximately 2.25% Cr and 1% Mo. The material number 1.7380 should be used when an unambiguous identifier is needed.

The same steel name or material number can appear in standards for tubes, forgings, bars or other products. Those standards have their own dimensional limits, heat treatments, testing rules and mechanical-property tables; certification to one product standard does not establish compliance with another.

Composition and metallurgical character

EN 10028-2 cast-analysis limits

Element	Requirement, % by mass
C	0.08–0.14
Si	≤ 0.50
Mn	0.40–0.80
P	≤ 0.020
S	≤ 0.010
N	≤ 0.012
Cr	2.00–2.50
Cu	≤ 0.30
Mo	0.90–1.10

These are cast-analysis requirements. Product analysis is subject to the separate permissible deviations in EN 10028-2. Elements not listed by the grade must not be intentionally added without purchaser agreement, except as needed for finishing the cast.

Chromium improves hardenability, oxidation resistance and elevated-temperature strength; molybdenum is central to creep strength and helps resist softening during high-temperature exposure. In the specified heat-treated conditions, the plate normally has a tempered transformation structure, commonly dominated by tempered bainite, although the actual structure depends on section thickness, cooling rate and processing route. The standard controls composition and mechanical performance rather than prescribing a single microstructure.

For nominal thickness above 150 mm, a maximum carbon content of 0.17% may be agreed. This is an order option rather than the normal 0.14% maximum and should be considered carefully for weldability and heat-treatment response.

Delivery condition and room-temperature properties

Transverse mechanical requirements at room temperature

Nominal thickness t, mm	Usual delivery condition	Minimum proof strength Rp0.2, MPa	Tensile strength Rm, MPa	Minimum elongation A, %	Minimum transverse KV2 at +20 °C, J
t ≤ 16	+NT	310	480–630	18	31
16 < t ≤ 40	+NT	300	480–630	18	31
40 < t ≤ 60	+NT	290	480–630	18	31
60 < t ≤ 100	+NT or +QT	280	470–620	17	27
100 < t ≤ 150	+QT	260	460–610	17	27
150 < t ≤ 250	+QT	250	450–600	17	27

EN 10028-2 Table 3 values are applicable to the transverse direction. Additional impact values at 0 °C or −20 °C are not basic requirements for this grade and must be agreed. A 40 J impact requirement may also be ordered by agreement.

Informative heat-treatment guidance in EN 10028-2

Operation	Guideline temperature
Normalizing or austenitizing	920–980 °C
Tempering	650–750 °C

These ranges are guidance for achieving the specified delivery condition, not a universal fabrication heat-treatment procedure. Actual cycles depend on plate thickness, furnace practice, quenching medium and required properties.

The thickness effect is substantial. As plate thickness increases, the specified proof strength falls and +QT becomes the usual condition because faster cooling is needed to obtain adequate through-thickness transformation and properties. Any substitution between +NT and +QT should therefore be checked against the ordered thickness range, certification and fabrication heat history rather than treated as a paperwork difference.

Elevated-temperature strength and creep data

Minimum 0.2% proof strength at elevated temperature

Nominal thickness t, mm	50 °C	100 °C	150 °C	200 °C	250 °C	300 °C	350 °C	400 °C	450 °C	500 °C
t ≤ 16	288	266	254	248	243	236	225	212	197	185
16 < t ≤ 40	279	257	246	240	235	228	218	205	191	179
40 < t ≤ 60	270	249	238	232	227	221	211	198	185	173
60 < t ≤ 100	260	240	230	224	220	213	204	191	178	167
100 < t ≤ 150	250	237	228	222	219	213	204	191	178	167
150 < t ≤ 250	240	227	219	213	210	208	204	191	178	167

Values are minimum Rp0.2 in MPa from EN 10028-2. They are material properties, not design-code allowable stresses.

Selected EN 10028-2 creep reference data

Temperature	1% plastic creep strain, 10,000 h	1% plastic creep strain, 100,000 h	Creep rupture, 10,000 h	Creep rupture, 100,000 h	Creep rupture, 200,000 h
450 °C	240 MPa	166 MPa	306 MPa	221 MPa	201 MPa
500 °C	147 MPa	103 MPa	196 MPa	135 MPa	120 MPa
550 °C	83 MPa	49 MPa	108 MPa	68 MPa	58 MPa
560 °C	73 MPa	41 MPa	96 MPa	58 MPa	50 MPa

Annex C identifies these as mean reference values and preliminary information for the purchaser. They are not guaranteed acceptance values and must not replace allowable stresses or creep design rules from the governing pressure-equipment code.

Selection for elevated-temperature service must use the applicable construction code, design life, joint efficiency, corrosion allowance, cyclic duty and environmental limits. The presence of creep data in the material standard does not by itself define a maximum service temperature or authorize a particular design stress.

Welding, forming and post-weld heat treatment

10CrMo9-10 is specified as weldable, but its alloy content and hardenability make welding practice more demanding than for carbon-manganese pressure plate. A qualified welding procedure should control hydrogen input, preheat, interpass temperature, heat input, consumable classification, cooling and post-weld heat treatment. Exact limits are functions of thickness, restraint, process, consumable, design code and required impact performance; they should not be inferred from the grade name alone.

EN 10028-2 cumulative stress-relieving parameter

P = Ts × (20 + log10 t) × 10^-3

Ts is the stress-relieving temperature in kelvin and t is holding time in hours. Annex B gives Pcrit = 19.2 for 10CrMo9-10, with illustrative combinations of 685 °C for 1 h or 675 °C for 2 h. This is guidance for assessing excessive thermal exposure, not a general PWHT prescription.

Excessive or repeated PWHT can reduce room-temperature strength and alter toughness. The purchaser should tell the plate manufacturer the intended cumulative stress-relieving severity when it may exceed the standard's guidance, and simulated heat-treated test coupons should be considered where the final properties must be demonstrated after fabrication. Repair cycles and future field heat treatments belong in the cumulative heat-treatment assessment.

Hot or cold forming can change the heat-treated structure and properties. Forming temperature, strain, local thinning and any subsequent heat treatment must therefore be established by the fabrication specification and construction code. Mechanical requirements certified on the original plate do not automatically demonstrate the properties of heavily formed or locally heat-treated areas.

Service-related degradation and optional testing

CrMo steels can undergo temper embrittlement during prolonged exposure in approximately the 400–500 °C range. The practical consequence is a shift in the ductile-to-brittle transition temperature, which can become important during shutdown, hydrotest or start-up even when normal operating temperature is high. EN 10028-2 permits an optional step-cooling test; the test procedure and acceptance criteria must be agreed at enquiry and order.

For corrosive H2S-containing environments, an optional hydrogen-induced-cracking test can be specified in accordance with EN 10229 and EN 10028-2 Annex D. This wet sour-service mechanism is different from high-temperature hydrogen attack. Suitability for pressurized hydrogen, refinery hydrogen service or other hydrogen environments requires assessment under the applicable design and service standards; the 1.7380 designation alone is not sufficient evidence of resistance.

Step-cooling, HIC testing, special impurity controls and additional impact requirements are optional unless expressly included in the purchase specification. They cannot normally be added after plate production and certification.

Specifying and purchasing the plate

Items that should be resolved on the purchase order

Item	Why it matters
Product standard and edition	State EN 10028-2 together with EN 10028-1 requirements; do not order only by the material number.
Grade	Use 10CrMo9-10 or 1.7380.
Dimensions and tolerances	Mechanical requirements and delivery condition depend on nominal thickness.
Delivery condition	Confirm +NT or +QT, particularly in thickness ranges where an alternative may be agreed.
Inspection document	Specify the required EN 10204 document, commonly 3.1 where project rules require it.
Impact requirements	State temperature, minimum energy, specimen location and any 40 J requirement beyond the basic specification.
Fabrication heat history	Tell the mill the anticipated cumulative PWHT or request simulated heat-treatment testing where relevant.
Internal soundness and surface quality	Specify the applicable EN 10028-1 options and acceptance levels required by the equipment specification.
HIC or step-cooling test	Specify when required by the service environment or project material specification.
Traceability and marking	Ensure plate identity remains traceable through cutting, forming, welding and component manufacture.

Certificate review should reconcile the heat number, plate number, dimensions, delivery condition, cast analysis, transverse tensile and impact results, test-piece condition and any optional tests with the purchase order. A certificate showing 1.7380 chemistry is not enough if the plate was not manufactured, heat treated and tested to the ordered EN 10028-2 condition.

Sources

BS EN 10028-2:2017 — Flat products made of steels for pressure purposes, Part 2British Standards Institution
DIN EN 10028-2:2017-10 — Flat products made of steels for pressure purposes, Part 2DIN Media
EN 10028-2:2017 — Standard text and tablesCEN / BSI reproduction
EN 10028-2:2017 — Scope and previewiTeh Standards
NEN-EN 10028-2:2017 — Current standard recordRoyal Netherlands Standardization Institute

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1.7380	Identical numerical designation	The EN steel number corresponding to 10CrMo9-10.
10CrMo9-10 under EN 10216-2	Same steel name and material number in a different product standard	Applies to seamless tubes for pressure purposes; tube dimensions, heat treatment, testing and mechanical requirements must be taken from EN 10216-2, not EN 10028-2.
ASTM/ASME A/SA-387 Grade 22	Approximate North American 2¼Cr-1Mo plate counterpart	Not automatically equivalent. Class, chemistry, heat treatment, thickness limits, toughness, testing and design-code acceptance must be compared before substitution.
13CrMo4-5 / 1.7335	Related lower-alloy EN pressure steel	Lower chromium and molybdenum content with different elevated-temperature strength and creep performance; not interchangeable.
12CrMo9-10 / 1.7375	Related EN 2¼Cr-1Mo grade	Has different chemistry and substantially different mechanical requirements. Similar alloy description does not establish equivalence.