15NiCuMoNb5-6-4 (WB36) Seamless Boiler Tube – High Strength Nickel-Copper Alloy Steel for Power Plant Feedwater Heaters

Short Description:

Womic Steel manufactures premium EN10216-2 15NiCuMoNb5-6-4 (WB36) seamless alloy steel tubes using advanced hot-rolling and cold-drawing processes. With strict adherence to the normalized and tempered heat treatment (+NT) delivery condition, our tubes offer exceptional high strength (minimum yield 440 MPa), excellent low-temperature toughness, and superior resistance to stress corrosion cracking, making them the preferred choice for high-pressure feedwater heaters, boiler drums, and power plant pressure vessels.

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1.Womic Steel: Manufacturing Capabilities & Company Strength

Womic Steel Group is a premier manufacturer and global exporter with over 20 years of expertise in producing carbon, alloy, and stainless steel tubular products. Our state-of-the-art facility spans a comprehensive production capability exceeding 10,000 tons per month for seamless pipes.

Production Size Range: Seamless pipes from OD 1/4" to 24" (10.3mm – 610mm) with wall thickness from SCH10 to XXS.

Quality Certifications & Regulatory Compliance:

ISO 9001:2015 Certified Quality Management System.

PED 2014/68/EU Annex I, Section 4.3 Compliance: Womic Steel's boiler tubes meet the essential safety requirements of the Pressure Equipment Directive. CE Marking (or Certificate of Conformity) is available upon request to facilitate smooth customs clearance and project acceptance within the European Economic Area.

EN 10204 3.2 Certification: In addition to standard 2.2 and 3.1 MTCs, we supply products with Inspection Certificate 3.2, validated by EU-authorized third-party bodies (TÜV, LR, BV) for critical boiler applications requiring full traceability.

Third-Party Inspection (TPI) Approvals: Our products and production processes are approved and audited by major international agencies and Classification Societies including SGS, BV, ABS, LR, DNV, and GL.

Global Recognition: Womic Steel is a trusted supplier to Fortune 500 energy companies and global EPC contractors, serving over 80 countries across Southeast Asia, Europe, the Middle East, and the Americas.

2. EN10216 15NiCuMoNb5-6-4 (WB36): Material Composition & Performance

15NiCuMoNb5-6-4 (Steel Number 1.6368), commonly referred to as WB36, is a nickel-copper-molybdenum-niobium alloy steel specifically designed for high-pressure, elevated temperature service in power plant pressure equipment. The designation "15" indicates approximately 0.15% Carbon, "NiCuMoNb" denotes Nickel-Copper-Molybdenum-Niobium alloy system, and "5-6-4" represents the approximate percentage ranges of these alloying elements. WB36 is a fine-grained bainitic steel that offers exceptional high strength (yield ≥ 440 MPa) combined with excellent low-temperature toughness and good weldability, making it the industry standard for high-pressure feedwater heaters, boiler drums, and thick-walled pressure vessels in fossil and nuclear power plants.

Chemical Composition (Cast Analysis, % by mass)

Element	C	Si	Mn	P	S	Cr	Mo	Ni	Cu	Nb	Al
Min %	0.12	0.10	0.70	—	—	—	0.25	1.00	0.50	0.010	0.010
Max %	0.17	0.35	1.00	0.020	0.010	0.30	0.50	1.30	0.80	0.050	0.040

*Note: The combination of Nickel (1.00-1.30%) and Copper (0.50-0.80%) provides excellent strength and toughness. Molybdenum (0.25-0.50%) enhances creep resistance, while Niobium (0.010-0.050%) promotes fine grain structure. Strict control of Phosphorus and Sulfur ensures optimal weldability and toughness.*

Mechanical Properties (Room Temperature)

Property	Value
Delivery Condition	Normalized and Tempered (+NT) at 880-980°C (Normalizing) + 580-680°C (Tempering)
Yield Strength (ReH)	≥ 440 MPa (for T ≤ 50mm)
Tensile Strength (Rm)	610 – 780 MPa
Elongation (A min)	19% (Longitudinal) / 17% (Transverse)

Note: The normalized and tempered (+NT) heat treatment produces a fine-grained bainitic microstructure, providing an excellent combination of high strength, toughness, and resistance to embrittlement.

Impact Properties (Low Temperature Toughness)

Property	Value
Test Temperature	0°C (standard) / -20°C (upon request)
Minimum Impact Energy	40 J (average) / 30 J (individual)

*Note: WB36 maintains excellent low-temperature toughness, making it suitable for feedwater systems where thermal cycling and cold start-up conditions exist.*

High-Temperature Creep Properties

Temperature (°C)	300	350	400	450
Yield Strength (MPa)	≥410	≥395	≥375	≥350
Creep Rupture Strength (100,000h)	—	—	200	160

*Note: WB36 is optimized for service in the 300-450°C range, typical of feedwater heater and boiler drum applications.*

3. Dimensional Range & Standards Compliance

Womic Steel supplies 15NiCuMoNb5-6-4 (WB36) tubes across a wide dimensional spectrum, fully compliant with the latest EN 10216-2:2024 standards.

Item	Specification
Standard	EN 10216-2:2024 (Seamless tubes for pressure purposes – Non-alloy and alloy steel tubes with specified elevated temperature properties)
Grade	15NiCuMoNb5-6-4 (1.6368) / WB36
Outer Diameter	10.3mm – 610mm (1/4" – 24")
Wall Thickness	2.0mm – 60.0mm (SCH10 – XXS)
Delivery Condition	Normalized and Tempered (+NT)
Inspection Categories	TC1 / TC2 (EN 10204 Type 2.2 Test Report)

3.Available Dimensions & Specifications

Size

SCH40S

SCH5S

SCH10S

SCH10

SCH20

SCH40

SCH60

XS/80S

SCH80

SCH100

SCH120

SCH140

SCH160

SCHXXS

1/8”

10.29

1.24

1.73

2.41

1/4”

13.72

1.65

2.24

3.02

3/8”

17.15

1.65

2.31

3.20

1/2”

21.34

2.77

1.65

2.11

2.77

3.73

4.78

7.47

3/4”

26.67

2.87

1.65

2.11

2.87

3.91

5.56

7.82

1”

33.40

3.38

1.65

2.77

3.38

4.55

6.35

9.09

1 1/4”

42.16

3.56

1.65

2.77

3.56

4.85

6.35

9.70

1 1/2”

48.26

3.68

1.65

2.77

3.68

5.08

7.14

10.15

2”

60.33

3.91

1.65

2.77

3.91

5.54

9.74

11.07

2 1/2”

73.03

5.16

2.11

3.05

5.16

7.01

9.53

14.02

3”

88.90

5.49

2.11

3.05

5.49

7.62

11.13

15.24

3 1/2”

101.60

5.74

2.11

3.05

5.74

8.08

100

4”

114.30

6.02

2.11

3.05

6.02

8.56

11.12

13.49

17.12

125

5”

141.30

6.55

2.77

3.40

6.55

9.53

12.70

15.88

19.05

150

6”

168.27

7.11

2.77

3.40

7.11

10.97

14.27

18.26

21.95

200

8”

219.08

8.18

2.77

3.76

6.35

8.18

10.31

12.70

15.09

19.26

20.62

23.01

22.23

250

10”

273.05

9.27

3.40

4.19

6.35

9.27

12.70

15.09

19.26

21.44

25.40

28.58

25.40

300

12”

323.85

9.53

3.96

4.57

6.35

10.31

14.27

12.70

17.48

21.44

25.40

28.58

33.32

25.40

350

14”

355.60

9.53

3.96

4.78

6.35

7.92

11.13

15.09

12.70

19.05

23.83

27.79

31.75

35.71

400

16”

406.40

9.53

4.19

4.78

6.35

7.92

12.70

16.66

12.70

21.44

26.19

30.96

36.53

40.49

450

18”

457.20

9.53

4.19

4.78

6.35

7.92

14.27

19.05

12.70

23.83

29.36

34.93

39.67

45.24

500

20”

508.00

9.53

4.78

5.54

6.35

9.53

15.09

20.62

12.70

26.19

32.54

38.10

44.45

50.01

550

22”

558.80

9.53

4.78

5.54

6.35

9.53

22.23

12.70

28.58

34.93

41.28

47.63

53.98

600

24”

609.60

9.53

5.54

6.35

9.53

17.48

24.61

12.70

30.96

38.89

46.02

52.37

59.54

4.Common Boiler,Heat Exchangers Tube Standards&Grade manufactured by Womic Steel

Standard	Steel Grades
Boiler Tubes (Seamless & Welded)
ASTM A178: Electric-Resistance-Welded Carbon Steel and Carbon-Manganese Steel Boiler Tubes	A178 Grade A, Grade C, Grade D
ASTM A179: Seamless Cold-Drawn Low-Carbon Steel Heat Exchanger and Condenser Tubes	A179 Grade C
ASTM A192: Seamless Carbon Steel Boiler Tubes for High Pressure	A192
ASTM A199: Seamless Cold-Drawn Intermediate Alloy Steel Heat Exchanger and Condenser Tubes	T5, T5b, T7, T9, T11, T22
ASTM A200: Seamless Intermediate Alloy Steel Still Tubes for Refinery Service	T5, T5b, T7, T9, T11, T22
ASTM A209: Seamless Carbon-Molybdenum Alloy Steel Boiler and Superheater Tubes	T1, T1a, T1b
ASTM A210: Seamless Medium-Carbon Steel Boiler and Superheater Tubes	A210 Grade A-1, Grade C
ASTM A213: Seamless Ferritic and Austenitic Alloy Steel Boiler, Superheater, and Heat Exchanger Tubes	T2, T5, T5b, T9, T11, T12, T17, T21, T22, T23, T24, T36, T91, T92, T122, TP304, TP304L, TP304H, TP309, TP309H, TP310, TP310H, TP316, TP316L, TP316H, TP321, TP321H, TP347, TP347H, TP347HFG
ASTM A250: Electric-Resistance-Welded Ferritic Alloy Steel Boiler and Superheater Tubes	T1, T1a, T1b, T2, T5, T9, T11, T22
ASTM A556: Seamless Cold-Drawn Carbon Steel Feedwater Heater Tubes	A556 Grade A2, Grade B2, Grade C2
Alloy Steel Pipes & Tubes (Chrome-Moly)
ASTM A335: Seamless Ferritic Alloy Steel Pipe for High-Temperature Service	P1, P2, P5, P5b, P5c, P9, P11, P12, P15, P21, P22, P23, P24, P36, P91, P92, P122, P911
ASTM A369: Seamless Ferritic Alloy Steel Pipe for High-Temperature Service	FP1, FP2, FP5, FP5b, FP5c, FP9, FP11, FP12, FP21, FP22, FP91
ASTM A213 (Alloy Grades): Seamless Ferritic Alloy Steel Boiler Tubes	T1, T1a, T1b, T2, T5, T5b, T9, T11, T12, T17, T21, T22, T23, T24, T36, T91, T92, T122
EN 10216-5: Seamless Stainless Steel Tubes for Pressure Purposes	1.4301, 1.4307, 1.4401, 1.4404, 1.4432, 1.4435, 1.4436, 1.4541, 1.4550, 1.4571
EN 10305-1: Seamless Cold Drawn Precision Steel Tubes	E215, E235, E355
EN 10305-2: Welded Cold Drawn Precision Steel Tubes	E215, E235, E355
German Standards (DIN)
DIN 17175: Seamless Steel Tubes for Elevated Temperature Service	St35.8, St45.8, 10CrMo910, 13CrMo44, 14MoV63, 15Mo3
JIS G3454: Carbon Steel Pipes for Pressure Service	STPG370, STPG410
JIS G3455: Carbon Steel Pipes for High Pressure Service	STS370, STS410, STS480
JIS G3456: Carbon Steel Pipes for High Temperature Service	STPT370, STPT410, STPT480
JIS G3461: Carbon Steel Boiler and Heat Exchanger Tubes	STB340, STB410, STB510
JIS G3462: Alloy Steel Boiler and Heat Exchanger Tubes	STBA12, STBA13, STBA20, STBA22, STBA23, STBA24, STBA25, STBA26, STBA28, STBA29
GB/T 3087: Seamless Steel Pipes for Low and Medium Pressure Boiler	10, 20
GB/T 5310: Seamless Steel Tubes for High Pressure Boiler	20G, 20MnG, 25MnG, 15MoG, 20MoG, 12CrMoG, 15CrMoG, 12Cr2MoG, 12Cr1MoVG, 12Cr2MoWVTiB, 07Cr2MoW2VNbB, 10Cr9Mo1VNbN, 10Cr11MoW2VNbCuBN
GB/T 6479: Seamless Steel Pipes for High Pressure Chemical Fertilizer Equipment	10, 20, 16Mn, 12CrMo, 15CrMo, 12Cr2Mo, 12Cr5MoI, 12Cr9MoI
Usage: Boiler, Superheater, Heat Exchanger, Petrochemical, Power Generation, Natural Gas, Refinery, High-Temperature Service, Corrosive Environments, Mechanical Equipment Manufacturing

5.Manufacturing Process

Production Workflow (Cold-Drawn Seamless Pipe Process):

● Raw Material Inspection: Incoming round billets are verified for chemical composition and surface quality. Material is properly segregated by grade and heat number to ensure full traceability.

● Billet Heating & Piercing: Billets are heated to forging temperature in rotary hearth furnaces and pierced via cross-roll piercing mill to form hollow tube shells.

● Cold Drawing: The pierced hollow shells undergo single or multiple cold drawing passes through precision dies and over mandrels to achieve the required outer diameter, wall thickness, and dimensional tolerances.

● Intermediate Heat Treatment: Between drawing passes, tubes may undergo intermediate annealing or normalizing to relieve work hardening and restore ductility for subsequent processing.

● Final Heat Treatment: Tubes receive final heat treatment (normalizing, annealing, or stress relieving) per applicable standards to achieve specified mechanical properties and grain structure.

● Straightening & Cutting: Precision straightening to meet standard straightness tolerances, followed by cutting to exact ordered lengths with clean, burr-free ends.

● Finishing & Surface Inspection: Visual examination to ensure freedom from surface defects such as cracks, folds, laps, and scabs. End beveling or plain-end finishing as required.

6.Quality Control

Raw Material Checking → Chemical Analysis → Mechanical Test → Visual Inspection → Dimension Check → Bend Test → Impact Test → Intergranular Corrosion Test → Non-Destructive Examination (UT, MT, PT) → Flaring and Flattening Test → Hardness Test → Pressure Testing → Ferrite Content Test → Metallography Testing → Corrosion Testing → Eddy Current Testing → Salt Spray Testing → Corrosion Resistance Testing → Vibration Test → Pitting Corrosion Test → Painting and Coating Inspection → Documentation Review

7.Primary Applications

Seamless boiler tubes are essential components in high-temperature and high-pressure service environments across various industries:

Power Generation: Boiler water walls, economizers, superheaters, reheaters, headers, and main steam pipelines in thermal power plants and combined cycle units.

Industrial Boilers: Steam generation systems, hot water boilers, and waste heat recovery boilers for manufacturing facilities.

Petrochemical & Refining: Heat exchangers, process heaters, cracking furnaces, and high-temperature fluid transfer lines.

Pressure Vessels: Shells, drums, and components for pressure vessels operating at elevated temperatures.

Chemical Processing: Reactors, reformers, and piping systems handling high-temperature gases and liquids.

EPC & Plant Piping: Process and utility piping in oil refineries, gas processing plants, and petrochemical complexes.

8.Packaging & Shipping:

Alloy boiler tubes are packaged and shipped with utmost care to ensure their protection during transit. Here is a description of the packaging and shipping process:

Packaging:

Protective Coating: Before packaging, boiler tubes are often coated with a layer of anti-rust oil or protective varnish to prevent surface corrosion and oxidation during storage and transit.

Bundling: Tubes of similar sizes and specifications are carefully bundled together. They are secured using steel straps or heavy-duty plastic bands to prevent movement within the bundle.

End Caps: Plastic or metal end caps are placed on both ends of the tubes to protect beveled ends, plain ends, and threaded connections from impact damage and debris ingress.

Padding and Cushioning: Padding materials such as foam, bubble wrap, or corrugated cardboard are used to provide cushioning and prevent abrasion or impact damage during handling and transportation.

Wooden Crates or Cases: For thin-walled tubes, precision cold-drawn tubes, or premium export orders, pipes may be packed in sturdy wooden crates or plywood cases to provide enhanced protection against external forces and rough handling.

9.Shipping:

Mode of Transportation: Boiler tubes are typically shipped via trucks, container vessels, or rail freight, depending on the destination, order volume, and delivery urgency. Air freight is available for time-critical shipments.

Containerization: Tubes are loaded into standard 20ft or 40ft shipping containers to ensure safe and organized transit. Container loading protects the cargo from weather conditions, moisture, and external contaminants.

Labeling and Documentation: Each package is clearly labeled with essential information including material grade, standard, dimensions, heat number, quantity, and handling instructions. Complete shipping documents are prepared for customs clearance and cargo tracking.

Customs Compliance: For international shipments, all necessary customs documentation—including commercial invoice, packing list, bill of lading, and Mill Test Certificates—is prepared to ensure smooth clearance at the destination port.

Secure Fastening: Within the transportation vehicle or container, bundles and crates are securely fastened and braced to prevent shifting, rolling, or movement that could cause damage during transit.

Tracking and Monitoring: Advanced logistics tracking systems are employed to monitor shipment status and provide real-time location updates to customers.

Insurance: Depending on the order value and customer requirements, marine cargo insurance may be arranged to cover potential losses or damages during transit.

In summary, Womic Steel ensures that all boiler and alloy tubes are packaged with industry-leading protective measures and shipped using reliable transportation methods to reach their destination in optimal condition. Proper packaging and shipping procedures are essential to preserving the integrity and quality of the delivered products.

Womic Steel Advantages & FAQ

Why Partner with Womic Steel?

One-Stop Shop: Complete range from seamless boiler tubes to matching OEM pipe fittings (Elbows, Tees, Reducers, Flanges) in compatible material grades.

Technical Compliance: Full Mill Test Certificates (EN 10204 Type 2.2, 3.1, or 3.2) provided with every shipment, detailing exact chemical composition and mechanical test results.

Value-Added Services: End beveling, threading & coupling, and anti-corrosion coating (FBE, 3LPE, Epoxy, Galvanizing) available in-house.

Competitive Logistics: Strategic partnership with global freight forwarders ensures optimized container loading and cost-effective worldwide shipping.

Inventory & Availability: Extensive stock of standard boiler tube sizes ensures short lead times and rapid response to urgent project requirements.

Choose Womic Steel Group as your reliable partner for high-quality Stainless Steel Pipes&Fittings and unbeatable delivery performance. Welcome Inquiry!

Website: www.womicsteel.com

Email: sales@womicsteel.com

Tel/WhatsApp/WeChat: Victor: +86-15575100681 or Jack: +86-18390957568

Frequently Asked Questions (FAQ)

Q: What is the difference between seamless and welded boiler tubes?
A: Seamless boiler tubes are manufactured from solid billets without a weld seam, offering superior pressure integrity and uniformity. They are preferred for high-temperature, high-pressure boiler applications. Welded tubes are suitable for lower pressure and less critical service conditions.

Q: What heat treatment conditions are available for boiler tubes?
A: Common delivery conditions include Hot-Rolled, Cold-Drawn, Normalized (+N), Annealed, and Quenched & Tempered. The specific heat treatment is applied based on material grade and end-use requirements to achieve optimal mechanical properties.

Q: What does "TC2" mean on a material certificate?
A: TC2 (Test Category 2) per EN 10216 standards mandates specific inspections including elevated temperature tensile testing and 100% Non-Destructive Testing (NDT) on every tube. This level of testing is required for critical boiler and pressure vessel applications.

Q: Can Womic Steel provide 3.2 inspection certificates (Third-Party Inspection)?
A: Yes. We welcome and facilitate inspections by DNV, BV, SGS, TÜV, ABS, LR, or any client-nominated representative during production and prior to shipment. 3.2 certificates are routinely supplied upon request.

Q: What is the maximum length available for boiler tubes?
A: We supply tubes in standard fixed lengths up to 12 meters (approx. 40 feet). Longer lengths for HRSG applications and U-bend tubes for heat exchangers are available upon request with detailed specifications and drawings.

Q: What types of end finishes do you offer?
A: We provide Plain Ends, Beveled Ends, Threaded Ends, and Coupled Ends. Custom end preparation is available to meet specific installation or welding requirements.

Q: Do you provide cut-to-length services?
A: Yes. We offer precision cutting to exact customer-specified lengths with tight tolerances and clean, burr-free ends.

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1.6368 Steel Pipe