Contents
Section 01
Why This Comparison Matters
Walk through the P&ID of almost any boiler, hydrogen reformer, or heavy-wall pressure vessel operating above 350 °C and you will encounter forgings made from one of two ferritic Cr-Mo grades: 13CrMo4-5 (EN 1.7335) or 10CrMo9-10 (EN 1.7380). Together these two materials cover the thermal range from approximately 350 °C to 560 °C — the operational core of petrochemical and power-generation plant worldwide.
Yet the decision between them is often made by habit rather than engineering rigour. Specifying 10CrMo9-10 because "it is the stronger grade" without evaluating the application's actual requirements leads to two common errors: over-specification, which adds material cost, complicates welding procedures, and introduces unnecessary PWHT cycles; or under-specification, which risks creep damage, hydrogen embrittlement, or oxidation failure long before the equipment reaches its design life.
This technical guide is written for design engineers, materials engineers, and procurement specialists who need a defensible, standard-backed answer to the question: for this specific application, at this specific temperature and pressure, which grade is correct?
Both grades are covered by EN 10028-2:2009 (flat products) and EN 10222-2 (pressure vessel forgings), among others. Allowable stress values cited in this article follow EN 13445-2 and EN 12952-3 design code tables. Always verify with the applicable code edition and applicable national annex for your project jurisdiction.
Section 02
Chemical Composition: The Alloy Logic Behind the Numbers
The alphanumeric steel designations encode the alloy composition directly. 13CrMo4-5 decodes as: 13 × 0.01% = nominal 0.13% carbon; Cr at a multiplier of ÷4 giving nominal 1.0% chromium; Mo at a multiplier of ÷10 giving nominal 0.5% molybdenum. 10CrMo9-10 similarly decodes to approximately 0.10% carbon, 2.25% chromium, and 1.0% molybdenum.
That two-fold increase in both Cr and Mo content is the root cause of every downstream performance difference between the grades — higher temperature capability, superior Nelson Curve position, stronger long-term creep rupture strength, and more demanding weldability.
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| Element | 13CrMo4-5 (1.7335) | 10CrMo9-10 (1.7380) | Role in the steel |
|---|---|---|---|
| Carbon (C) | 0.10 – 0.18% | 0.08 – 0.15% | Strength base; lower C in 1.7380 partially compensates the higher CE from greater Cr+Mo content |
| Chromium (Cr) | 0.70 – 1.15% | 2.00 – 2.50% | Steam oxidation resistance; carbide stabilisation; critical Nelson Curve position determinant |
| Molybdenum (Mo) | 0.40 – 0.60% | 0.90 – 1.10% | Solid-solution creep resistance above 450°C; M₂C/M₆C carbide stability at grain boundaries |
| Silicon (Si) | 0.17 – 0.37% | ≤ 0.50% | Melt deoxidation; minor oxidation resistance improvement at scale surface |
| Manganese (Mn) | 0.40 – 0.70% | 0.40 – 0.70% | Hardenability through-section; sulphide morphology control (MnS vs FeS) |
| Phosphorus (P) | ≤ 0.025% | ≤ 0.025% | Grain-boundary segregation driver; primary cause of temper embrittlement in CrMo — minimise |
| Sulphur (S) | ≤ 0.010% | ≤ 0.010% | MnS inclusion formation; reduces transverse ductility and Charpy impact — minimise |
The critical mechanism difference is in how each grade responds to sustained exposure above 450°C. In 13CrMo4-5, the lower Mo content means carbide precipitates coarsen and dissolve more rapidly at elevated temperature — a process called overageing — which progressively reduces the resistance to dislocation creep. In 10CrMo9-10, the higher Mo content stabilises M₂C and M₆C carbides at grain boundaries for far longer exposure times, maintaining creep resistance well beyond the temperature ceiling of the lower-alloy grade.
The carbon equivalent (CE) of 13CrMo4-5, typically 0.55–0.65 for forged sections, is substantially lower than that of 10CrMo9-10 (0.70–0.85). This directly enables lower preheat temperatures, a wider PWHT window, and lower risk of cold hydrogen cracking in the heat-affected zone. Engineers who default to the higher-alloy grade for perceived safety may inadvertently introduce greater fabrication risk for below-480°C applications.
Section 03
Temperature Capability & Creep Resistance: Where They Diverge
Creep — the slow, time-dependent plastic deformation of steel under sustained stress at elevated temperature — is the life-limiting failure mode for all pressure-retaining components operating above approximately 370°C. The engineering design criterion is not room-temperature tensile strength but the 100,000-hour creep rupture stress at the operating temperature, which is what the EN 13445 permissible stress tables encode.
At 450°C, the EN 13445 permissible stress for 13CrMo4-5 (N+T, 16–40 mm thickness) is approximately 82 MPa. The equivalent value for 10CrMo9-10 at 450°C is approximately 94 MPa (indicative values — consult current EN 13445-2 edition for design) — a modest 15% advantage that in most designs will not justify the additional fabrication complexity. However, at 520°C, 13CrMo4-5 is not listed in the EN 13445 tables at all — it is beyond its safe pressure-equipment envelope — while 10CrMo9-10 retains a permissible stress near 70 MPa. By 550°C, only the 2.25Cr-1Mo grade remains viable of the two.
The design life implication of operating near the temperature ceiling
Pressure equipment is designed for 100,000-hour (approximately 11.4-year) creep lives, with actual plant lives of 25–40 years achieved by operating well within the permissible stress envelope. Operating 13CrMo4-5 even momentarily above 500°C during process upset or startup consumes creep life at a rate orders of magnitude faster than the design basis assumes, because creep rate rises exponentially with temperature. Unexplained wall thinning in CrMo steam piping revealed during outage inspection is frequently traceable to sustained over-temperature episodes rather than corrosion — a distinction that matters enormously for remaining life assessment.
If any documented operating scenario — including startup, heat soak, steam temperature exceedance, or heat exchanger tube leak — takes the metal temperature above 470°C for sustained periods, specify 10CrMo9-10. The material cost premium of 15–30% is substantially less than the cost of an unplanned shutdown, a fitness-for-service assessment, or a pressure-component replacement on an operating plant.
Section 04
Mechanical Properties at a Glance
Both grades are standardly supplied in the Normalised + Tempered (N+T) condition for forgings. Quenched + Tempered (+QT) is available from qualified manufacturers where enhanced through-thickness hardenability is required for heavy-section components above 100 mm thickness. The following typical minimum values per EN 10222-2 apply for forgings in the 16–100 mm thickness range:
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| Property | 13CrMo4-5 · 1.7335 · N+T | 10CrMo9-10 · 1.7380 · N+T |
|---|---|---|
| Tensile strength Rm | 440 – 590 MPa | 480 – 630 MPa |
| 0.2% proof stress Rp0.2 | ≥ 275 MPa | ≥ 280 MPa |
| Elongation A5 | ≥ 20% | ≥ 19% |
| Charpy KV at +20 °C | ≥ 40 J avg · ≥ 28 J min | ≥ 40 J avg · ≥ 28 J min |
| Typical hardness (N+T) | 135 – 185 HB | 145 – 200 HB |
| Density | ≈ 7.85 g/cm³ | ≈ 7.85 g/cm³ |
| Thermal expansion coefficient (20–300°C) | 12.5 × 10⁻⁶ /°C | 12.2 × 10⁻⁶ /°C |
At room temperature, the two grades are nearly identical in their typical room-temperature mechanical properties. The divergence that matters for engineering selection only emerges above 450°C, where creep rupture data — not tensile data — is the governing criterion. Selecting between 13CrMo4-5 and 10CrMo9-10 on the basis of room-temperature tensile strength alone is the most common and consequential error in pressure equipment material selection.
Section 05
Weldability: The Practical Difference That Affects Project Cost
Weldability is where the two grades diverge most significantly for construction and maintenance operations — and where 13CrMo4-5 holds its clearest, most practically impactful advantage.
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| Parameter | 13CrMo4-5 (1.7335) | 10CrMo9-10 (1.7380) |
|---|---|---|
| Carbon equivalent (CE, typical) | 0.55 – 0.65 | 0.70 – 0.85 |
| Minimum preheat (t > 25 mm) | 150 – 200°C | 200 – 300°C |
| Maximum inter-pass temperature | 350°C | 350°C (strictly enforced) |
| PWHT temperature range | 690 – 710°C | 700 – 760°C |
| PWHT minimum hold time | 1 h/25 mm, min 1 h | 1 h/25 mm, min 2 h |
| Filler metal classification | Low-hydrogen (E7018 / ER80S-B2 equiv.) | Low-hydrogen (ER90S-B3 / E9018-B3 equiv.) |
| HAZ hydrogen cracking risk | Low to moderate | Moderate to high |
| Hardness limit post-PWHT (NACE MR0175 ref.) | ≤ 22 HRC (sour service — verify with applicable standard) | ≤ 22 HRC (sour service — verify with applicable standard) |
The higher carbon equivalent of 10CrMo9-10 elevates the risk of cold hydrogen cracking in the heat-affected zone (HAZ) if preheat, inter-pass temperature, or post-heat requirements are not rigorously maintained. For large-diameter pressure vessel nozzle forgings or heavy valve bodies being site-welded into existing pipework — particularly at low ambient temperatures or in confined conditions — the logistical difficulty of sustaining 250–300°C preheat throughout the entire welding sequence is real and significant.
In large-scale construction where field welding is unavoidable, 13CrMo4-5's lower preheat requirement and broader PWHT temperature window translate directly into faster weld joint completion, reduced temporary heat equipment requirements, and a materially lower risk of procedure non-conformance. If your design temperature is verifiably below 470°C, substituting 10CrMo9-10 for perceived "safety" may introduce more fabrication risk than it eliminates.
Post-weld heat treatment for 1.7380 requires tighter furnace temperature control: below 700°C, tempering of the HAZ is incomplete and the PWHT does not achieve its metallurgical purpose; above 760°C, partial re-austenitisation in thin sections can occur, forming fresh martensite on cooling and defeating the PWHT entirely. Temperature recorder charts and furnace calibration certificates should be required as part of the quality record for any critical 1.7380 weld.
Section 06
Hydrogen Service & the Nelson Curve: The Single Most Important Selection Factor in Refinery Applications
For any equipment in hydrogen-containing service — hydrogen reformers, hydrotreaters, hydrocracker reactors, catalytic reformer effluent exchangers, and associated high-pressure piping — the governing material selection tool is the Nelson Curve, published in API RP 941. The Nelson Curve maps the combinations of operating temperature and hydrogen partial pressure that lead to High-Temperature Hydrogen Attack (HTHA).
HTHA is the irreversible reaction of atomic hydrogen (which diffuses into steel at elevated temperature) with iron carbide (Fe₃C) to produce methane gas. Methane cannot diffuse back out; it accumulates at grain boundaries, building internal pressure that causes fissuring, blistering, and decarburisation of the steel matrix. HTHA damage is typically undetectable by conventional UT until it is well advanced, and once initiated, the damage cannot be reversed by heat treatment or other remediation.
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| Operating condition | 13CrMo4-5 — 1Cr-0.5Mo curve | 10CrMo9-10 — 2.25Cr-1Mo curve |
|---|---|---|
| 300°C, 10 bar H₂ | ✓ Safe | ✓ Safe |
| 380°C, 30 bar H₂ | ✓ Safe (within margin) | ✓ Safe |
| 420°C, 60 bar H₂ | ✗ Exceeds 1Cr-0.5Mo curve | ✓ Safe |
| 440°C, 80 bar H₂ | ✗ HTHA risk — do not use | ✓ Safe |
| 470°C, 120 bar H₂ | ✗ Not acceptable | ⚠ Borderline — apply full API 941 safety margin |
| 510°C, 150 bar H₂ | ✗ Not acceptable at any H₂ pressure | Check curve — approaching limit |
The conditions in Table 4 are illustrative only. API RP 941 specifies explicit safety margins that must be applied to the nominal Nelson Curve lines — particularly for equipment where metal temperature measurement accuracy is limited, and for existing equipment that may have experienced prior HTHA damage. Never design to the nominal curve line without applying the prescribed margin. For any hydrogen partial pressure above 30 bar at metal temperatures above 370°C, engage a qualified materials engineer before specifying 13CrMo4-5.
The Nelson Curve position of 10CrMo9-10 (2.25Cr-1Mo) is approximately 30–50°C higher in safe operating temperature at equivalent hydrogen partial pressure compared to 13CrMo4-5 (1Cr-0.5Mo). This difference is the primary — and often sufficient — engineering justification for specifying 10CrMo9-10 in refinery and petrochemical hydrogen service, independently of any temperature-based argument.
Section 07
Industry Applications: Where Each Grade Belongs
13CrMo4-5 (1.7335) — the workhorse for sub-480°C service
Despite being the lower-alloy grade, 13CrMo4-5 accounts for the majority of total CrMo forging tonnage shipped globally. Its combination of adequate elevated-temperature strength up to 480°C, excellent weldability, and lower cost makes it the natural choice for a wide range of EN 1.7335 (13CrMo4-5) forged pressure components, including:
- Boiler drum shells, end caps, and nozzle forgings in subcritical steam generation plants (typical metal temperatures 340–430°C)
- Superheater outlet header forgings and main steam stop valve bodies where live steam temperature stays below 470°C
- Pressure vessel shell forgings, nozzle necks, and transition cones in atmospheric and vacuum crude distillation units
- Heat exchanger channel head and shell flange forgings, floating head covers, and tube sheet blanks in crude preheat trains
- Gate valve, globe valve, and check valve body forgings for steam service up to PN 400 Class 1500
- Blowout preventer (BOP) body blocks and wellhead Christmas tree body forgings in non-sour, non-HTHA service
- Impeller blanks and pump casing forgings for high-temperature process circulation pumps
10CrMo9-10 (1.7380) — essential for high-temperature and hydrogen service
10CrMo9-10 occupies a narrower but technically critical niche. Its higher alloy cost and more demanding fabrication requirements are justified and necessary when:
- Hydrogen partial pressure at operating temperature places the design point above the 1Cr-0.5Mo Nelson Curve (with API 941 margin applied)
- Steam temperature is in the 490–550°C range, common in high-efficiency combined-cycle and ultra-supercritical power plants
- Superheater outlet headers and live steam stop valve bodies in high-pressure steam circuits above 480°C
- Catalytic reformer charge heater manifolds, effluent air cooler inlet headers, and associated flanges
- Reactor inlet and outlet nozzle forgings in fixed-bed hydrotreating and hydrocracking units
- High-pressure hydrogen gas coolers and heat exchangers in hydrogen production plant
- Any application where EN 13445 permissible stress tables do not list 13CrMo4-5 at the design temperature
Section 08
Selection Decision Framework: A Step-by-Step Guide
Work through the following questions in strict sequence. Stop at the first question answered "yes" — that answer determines your grade. Do not continue to subsequent questions once a grade is identified.
Does any operating scenario involve hydrogen partial pressure above 35 bar at metal temperatures above 370°C? If yes → specify 10CrMo9-10 (EN 1.7380). Stop here. The 1Cr-0.5Mo Nelson Curve position of 13CrMo4-5 is not adequate for this condition regardless of temperature.
Is the maximum metal temperature — not the nominal design temperature, but the highest temperature the metal can experience in any operating scenario including startup, upset conditions, and steam-side transients — above 470°C for sustained periods? If yes → specify 10CrMo9-10 (EN 1.7380). Above 470°C, EN 13445 creep rupture allowable stresses for 13CrMo4-5 are not sufficient for pressure-retaining service.
Does the EN 13445 permissible stress table for 13CrMo4-5 at your design temperature and wall thickness satisfy your pressure design calculation? If the value is absent or insufficient → specify 10CrMo9-10 (EN 1.7380).
Is field welding a significant activity? Are there constraints on preheat logistics, PWHT furnace access, or WPS/PQR qualification scope? If your design temperature is verifiably below 470°C and hydrogen service is not a factor, 13CrMo4-5 (EN 1.7335) offers a meaningful fabrication cost and schedule advantage that should be weighed explicitly.
Choose 13CrMo4-5 (EN 1.7335) when:
- Maximum design temperature ≤ 470°C in all scenarios
- H₂ partial pressure is within the 1Cr-0.5Mo Nelson Curve (with API 941 margin)
- Field welding is a significant project activity
- Budget and schedule are primary constraints alongside technical adequacy
- Application is boilers, heat exchangers, steam headers, or standard valve bodies
- Existing WPS / PQR is already qualified for 1.7335
- Older equipment drawings specify 13CrMo4-5 and original design basis is sound
Choose 10CrMo9-10 (EN 1.7380) when:
- Design temperature is 470–550°C in any scenario
- H₂ partial pressure exceeds 1Cr-0.5Mo Nelson Curve limits with API 941 margin
- Application is a hydrotreater, hydrocracker, or catalytic reformer
- EN 13445 permissible stress for 1.7335 is absent or insufficient at design temperature
- Superior steam oxidation resistance is required above 480°C
- Client or project specification mandates 2.25Cr-1Mo
- Long-term creep life assurance is critical and design life exceeds 20 years
Section 09
Cost & Procurement Considerations
From a raw material standpoint, 10CrMo9-10 forgings typically carry a premium of 15–30% over equivalent 13CrMo4-5 forgings of the same size and forging complexity. This reflects higher alloy content and the additional metallurgical process control — vacuum degassing, tighter chemical analysis windows — required to consistently achieve the creep properties the grade promises.
However, the total installed cost comparison is more complex. For projects with a large number of welded joints in the CrMo material, the fabrication cost difference often exceeds the material cost difference. The higher preheat requirements, stricter inter-pass temperature management, longer PWHT hold times, and the need for specially qualified welding procedures and operators for 10CrMo9-10 can cumulatively add 8–15% to total fabrication costs on weld-intensive projects compared to a 13CrMo4-5 specification — before accounting for WPS/PQR qualification time if the contractor is not already approved for 1.7380.
For either grade, require EN 10204 Type 3.1 material test certificates showing full ladle and product chemical analysis plus mechanical test results from the production heat. For hydrogen service applications or forgings with section thickness above 200 mm, specify vacuum degassing (LF+VD) in the steel-making route — this achieves hydrogen content below 1.5 ppm, reducing susceptibility to flake formation in heavy sections and eliminating hydrogen as an HTHA crack initiation site. Request the steel-making route confirmation as part of the MTR package.
Section 10
ASTM / ASME Cross-Reference for Global Projects
Many international projects specify both EN and ASTM grades, or require cross-referencing for ASME design code compliance. The following table gives the established equivalences for both grades:
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| Product form | 13CrMo4-5 (EN 1.7335) equivalent | 10CrMo9-10 (EN 1.7380) equivalent |
|---|---|---|
| Forgings | ASTM A182 F11 / F12 (1Cr-0.5Mo) | ASTM A182 F22 / UNS K21590 (2.25Cr-1Mo) |
| Plates | ASTM A387 Grade 11 / Grade 12 | ASTM A387 Grade 22 |
| Seamless pipe | ASTM A335 Grade P11 / P12 | ASTM A335 Grade P22 |
| Flanges & fittings | ASTM A182 F11 CL1/CL2/CL3 | ASTM A182 F22 CL1/CL3 |
| Bars (welding) | ASTM A29 / ASME SA-29 | ASTM A29 / ASME SA-29 |
EN and ASTM grades are similar in chemistry and intended use, but are not identical in composition limits, heat treatment requirements, or allowable stress tables. Substituting one for the other in an existing design requires explicit approval by the responsible engineer, re-verification of pressure calculations using the applicable design code allowable stresses, and updated material traceability documentation. Never substitute EN for ASTM or vice versa without a formal engineering change.
Frequently Asked Questions
13CrMo4-5 vs 10CrMo9-10: Engineer's Q&A
What is the difference between 13CrMo4-5 and 10CrMo9-10?
13CrMo4-5 (EN 1.7335) contains approximately 1% chromium and 0.5% molybdenum and is suitable for continuous pressure-equipment service up to approximately 480°C. 10CrMo9-10 (EN 1.7380) contains approximately 2.25% chromium and 1% molybdenum, giving it a maximum continuous service temperature of approximately 550°C, a superior Nelson Curve position for hydrogen service (API RP 941), and greater long-term 100,000-hour creep rupture strength above 450°C. Both are specified under EN 10028-2 for pressure-retaining equipment.
When should I choose 10CrMo9-10 instead of 13CrMo4-5?
Specify 10CrMo9-10 (1.7380) when: (1) the maximum metal temperature in any operating scenario exceeds 470°C; (2) the application involves hydrogen partial pressure above 35 bar at temperatures above 370°C (hydrotreaters, reformers, hydrocrackers); or (3) the EN 13445 permissible stress table does not list 13CrMo4-5 at your design temperature, or its tabulated value is insufficient for your design pressure calculation.
Is 13CrMo4-5 easier to weld than 10CrMo9-10?
Yes, significantly. 13CrMo4-5 has a carbon equivalent (CE) of approximately 0.55–0.65 versus 0.70–0.85 for 10CrMo9-10. In practical terms this means: preheat of 150–200°C for 1.7335 versus 200–300°C for 1.7380; PWHT at 690–710°C (simpler temperature control) versus 700–760°C (tighter window, risk of re-austenitisation above 760°C); and a materially lower risk of cold hydrogen cracking in the heat-affected zone if procedure parameters drift. For field welding on large installations, this translates to faster cycle times, lower equipment costs, and lower procedure non-conformance risk.
What is the maximum service temperature for 13CrMo4-5?
The maximum recommended continuous service temperature for 13CrMo4-5 (EN 1.7335) in pressure equipment is approximately 480°C. This is the temperature above which EN 13445-2 permissible stress tables no longer list the grade for pressure design purposes. For transient conditions, the metal should not exceed approximately 490–500°C without a formal fitness-for-service assessment. For service genuinely above 480°C, EN 1.7380 (10CrMo9-10), EN 1.4903 (P91), or other creep-resistant grades must be specified.
What is the ASTM equivalent of 13CrMo4-5 and 10CrMo9-10?
The closest ASTM equivalent to EN 1.7335 (13CrMo4-5) for forgings is ASTM A182 Grade F11 or F12 (1Cr-0.5Mo); for plates, ASTM A387 Grade 11 or 12; for pipe, ASTM A335 P11 or P12. The closest ASTM equivalent to EN 1.7380 (10CrMo9-10) for forgings is ASTM A182 Grade F22 (2.25Cr-1Mo, UNS K21590); for plates, ASTM A387 Grade 22; for pipe, ASTM A335 P22. Note these are equivalences in application intent, not direct substitutions without engineering review.
What is the Nelson Curve and why does it matter for Cr-Mo steel selection?
The Nelson Curve (API RP 941) is a chart used in materials engineering that maps the combinations of operating temperature and hydrogen partial pressure that cause High-Temperature Hydrogen Attack (HTHA) in carbon and alloy steels. 13CrMo4-5 (1Cr-0.5Mo) lies on a lower Nelson Curve than 10CrMo9-10 (2.25Cr-1Mo), meaning it becomes susceptible to HTHA at lower hydrogen partial pressures for the same temperature — approximately 30–50°C lower. In hydrogen-service plant — refineries, reformers, hydrotreaters — specifying 13CrMo4-5 where the operating point falls above the 1Cr-0.5Mo curve can cause irreversible, un-detectable HTHA damage leading to catastrophic pressure boundary failure.
How much more expensive is 10CrMo9-10 compared to 13CrMo4-5?
10CrMo9-10 (EN 1.7380) forgings typically cost 15–30% more than equivalent 13CrMo4-5 (EN 1.7335) forgings of the same size and complexity, reflecting higher alloy content and more stringent steel-making requirements. However, the total installed cost difference is typically larger: the higher preheat, stricter inter-pass temperature control, longer minimum PWHT hold times, and need for specially qualified welding procedures for 10CrMo9-10 can add 8–15% to total fabrication costs on weld-intensive projects.
What supply condition are EN 1.7335 and EN 1.7380 forgings delivered in?
Both grades are standardly supplied in the Normalised and Tempered (N+T) condition for pressure equipment forgings per EN 10222-2. Quenched and Tempered (+QT) is available from qualified forging manufacturers for heavy sections (typically above 100 mm thickness) requiring enhanced through-thickness mechanical properties. The heat treatment condition must be explicitly specified on the purchase order and is documented on the EN 10204 3.1 material test certificate. EN 10204 3.1 MTRs are available upon request — please confirm at order stage.
Section 11 — Conclusion
Conclusion & Next Steps
The choice between 13CrMo4-5 (EN 1.7335) and 10CrMo9-10 (EN 1.7380) is not a question of which grade is superior — it is a question of which grade is appropriate for the specific temperature, hydrogen partial pressure, fabrication context, and design code requirements of your project.
13CrMo4-5 (1.7335) is the technically correct and commercially optimal specification for the large majority of sub-470°C pressure equipment: power boilers, heat exchangers, steam headers, valve bodies, and pressure vessel nozzles where the 1Cr-0.5Mo Nelson Curve position is adequate. Its weldability advantage in field construction is real, measurable, and should be given explicit weight in every material selection decision in this temperature range.
10CrMo9-10 (1.7380) is required — not merely preferred — when design temperature exceeds 470°C in any operating scenario, when hydrogen partial pressure places the operating point above the 1Cr-0.5Mo Nelson Curve with API 941 safety margin applied, or when EN 13445 permissible stress values for 13CrMo4-5 are insufficient at the design pressure and temperature. In those applications, the higher alloy content and more demanding welding requirements are not inconveniences — they are the technical price of safe long-term operation in a more demanding environment.
Jiangsu Liangyi Co., Limited is a qualified 1.7335 (13CrMo4-5) forging manufacturer, producing open-die forgings, seamless rolled rings, valve body blanks, nozzle forgings, and custom shapes to EN 10222-2, with ISO 9001:2015 quality management, with EN 10204 3.1 documentation available, vacuum-degassed steel options, and DFM review at quotation stage. Send us your drawings and specifications — our engineering team provides a detailed technical review and competitive quote within 24 hours.
Contact our engineering team at sales.com with your drawing, pressure design conditions (temperature, pressure, medium), applicable design code, and required inspection level. We will confirm the optimal grade, supply condition, and EN 10204 certificate type for your application — at no charge and with no obligation.