WB36 steel pipe

What’s WB36 steel pipe?

WB36 steel pipe is a bainitic Ni-Cu-Mo steel pipe micro-alloyed with niobium according German standards DIN WB36. WB36 is also known as 15NiCuMoNb5-6-4 according to EN 10216-2, ASTM A213 T36 and ASTM A335 P36.

WB36 steel pipe (or 15NiCuMoNb5) was first developed by the German Mannesmann Company.Because of it’s high strength characteristic, WB36 pipe can be used for high pressure pipeline of temperature up to 500 ℃, or high thermal power unit parameters, such as supercritical unit of boiler steam drum, steam separator, header, steam generator, steam pipe, and high temperature or high pressure waterworks of nuclear power equipment.

The greatest advantages of WB36 alloy pipe are 100% recovery, environmental protection, energy saving, resource saving. The Chinese government encourages to expand the application field of WB36 high-pressure alloy pipe.

Chemical Compositions(%) of 15NiCuMoNb5

P≤ 0.025

Mechanical Properties of 15NiCuMoNb5

Yield strength( Mpa) at RT – 350℃Ultimate tensile strength
Uniform elongation A₅
  430         353610-760≥16


This grade is mainly used in high-pressure, medium-temperature feedwater lines (close to 400 °C).


WB36 exhibits excellent high-strength properties up to 450 °C. The reduced weight of the feedwater piping components compared with conventional carbon steel allows improved resistance to thermal fatigue and very good heat transfer.

Delivery status
The steel tubes shall be delivered in a heat treated condition.

Length: 5800mm; 6000mm; 6096mm; 7315mm; 11800mm; 12000mm; and so on.

Max length: 16000mm, also U bending can be offered.

The greatest advantages of WB36 alloy pipe is 100% recovery, environmental protection, energy saving, resource saving. The Chinese government encourages to expand the application field of wb36 high-pressure alloy pipe.

At present,The China’s consumption of wb36 pipe for the proportion of total alloy steel pipe only half as much as that of the developed countries. WB36 alloy pipe using field provide a broader space for the development of industry.According to the research of the Chinese special steel association WB36 alloy tube branch, the future of our country high pressure wb36 alloy tube material demand grew by an average of up to 10-12%.


15NiCuMoNb5-6-4 (DIWA373, 15NiCuMoNb5, or WB36) is the material developed by mannesman company in Germany, which is used for nuclear power generating units and high parameter thermal power generating units. It is developed by adding Ni Cu Mo Nb alloy elements on the basis of carbon manganese steel. Because the alloy elements such as Ni, Cu, Mo and Nb are added to the steel, it has the effect of fine grain strengthening and precipitation strengthening, thus greatly improving the high temperature strength and permanent strength of the steel, and the addition of Cu does not reduce the permanent plasticity of the steel.
15NiCuMoNb5-6-4 steel is characterized by strength, yield limit is 40% higher than 20g steel, service temperature is 400 ℃, it can be used as high-pressure pipe with pipe wall temperature up to 500 ℃, or as high-temperature and high-pressure components of high parameter thermal power generating units, such as boiler drum, steam water separator, header, steam generator, steam pipe and nuclear power equipment.

Chemical composition

Grade C Mn Si P S Cr
15NiCuMoNb5-6-4 ≤0.17 0.8-1.2 0.25-0.50 ≤0.03 ≤0.025 ≤0.30
Cu Mo Ni Nb
0.5-0.8 0.25-0.50 1.00-1.30 0.015-0.045 ≤0.02 

Mechanical properties

Grade Yield Strength/MPa Tensile Strength/Mpa Elongation/% Hardness/HB Impact work longitudinal/J Microstructure
20℃ 0℃ -20℃
15NiCuMoNb5-6-4 ≥440 610-780 ≥19 ≤252 ≥95 ≥80 ≥60 F+B+P

Durable strength σ, 15NiCuMoNb5-6-4 (WB36) high pressure boiler tube

Grade 400℃ 420℃ 440℃ 460℃ 480℃ 490℃ 500℃
15NiCuMoNb5-6-4 373 325 273 210 139 104 69

Heat treatment

Normalizing or quenching Temper Stress relief heat treatment
900-980 ° C air cooling 580-640 ° C air cooling 550-600 ° C air cooling
880-930 ° C oil or water cooling 620-700 ° C air cooling

Metallographic structure

The supply state of 15nicumonb5-6-4 seamless steel tube (diwa373, WB36) steel is normalizing (quenching) + tempering. After the final heat treatment of normalizing and tempering, the microstructure is bainite + ferrite + sorbite or bainite + a small amount of ferrite.

Welding material

15nicumonb5-6-4 steel tubes have good welding performance. Manual welding rod l-80 (aws-e11016g), tungsten argon arc welding wire smh-80 (aws-e110s) or corresponding domestic welding materials. In order to avoid welding cracks, preheating (temperature 150-200 ℃) shall be carried out before welding. Stress relief treatment shall be carried out after welding.