As the development of wind energy, many steel plants start to manufacture steel plates that can exactly meet the requirements of steel wind turbine towers. Therefore, all the famous national steel standards have established their own wind power steel plates standards.

Wind power steel plate is the material that used to manufacture industrial wind turbine towers. The special requirements of steel materials mainly depend on the regional environment. For example, if the wind turbine towers are installed in the cold climates, the minimum temperature in winter is about minus thirty degrees, so the welding of wind turbine tower in low climates must be prevent for brittle fracture at low temperature.

In the following article, we will discuss the detail performance of standard wind power steel materials.

Chinese Wind Turbine Tower Material Grades

Different steel standards has different grades for wind power steel, but the chemical components and mechanical properties of the wind power steels are similar.

Chinese steel standard – GB standard defines steel for wind turbine tower manufacture as Q345C, Q345D, Q345E. And the wind turbine tower flanges are ring forgings that are made of Q345D and Q345E steel. Chinese steel grades consist of several parts, such as the yield strength, quality level.

Take Q345C as an example:

Q refers to the capital letter of Chinese yield strength;

345 refers to the value of steel yield strength, 345N/mm2;

C refers to the quality level of steel.

Moreover, if the steel plate requires through-thickness characteristics, there will be a postfix which refers to its through-thickness characteristics such as Z15, Z25 after the steel grade.

a picture of global steel standard logos

Chinese Wind Turbine Tower Materials Chemical Components

Wind turbine tower steels belongs to low alloy high strength structure steel. The manufacture technology of low alloy high strength steel is mature in China. Therefore, Q345 grade is not the only steel grade option for wind turbine tower manufacture. Except Q345 steel , There are also other low alloy hight strength steel grades that are suitable for wind turbine tower manufacture. The wind farm owners can choose the most cost effective wind turbine tower materials by themselves.

Below, there is the chemical components table for Chinese steel grades that can be used to manufacture wind turbine towers.

Table 1 Wind turbine tower steel materials chemical components

Grade Level Chemical components %
C

≦

 Mn P

≦

 S

≦

 Si

≦

 Nb

≦

 V

≦

 Ti

≦

 Mo

≦

 Cr

≦

 Ni

≦

 Cu

≦

 Als

≦

 N

≦
Q235 B, C 0.17 0.6 – 1.4 0.03 0.025 0.35 0.05 0.06 0.05 0.1 0.3 0.3 0.3 0.015 0.012
D, E 0.025 0.02
Q275 B, C 0.18 0.6 – 1.5 0.025 0.02 0.4 0.05 0.06 0.05 0.1 0.3 0.3 0.3 0.015 0.012
D, E 0.16 0.015
Q345 C, D 0.2 1 – 1.6 0.025 0.015 0.4 0.06 0.07 0.05 0.2 0.3 0.3 0.3 0.015 0.012
E, F 0.18 0.018 0.01 0.009
Q420 C, D 0.2 1 – 1.6 0.025 0.015 0.4 0.06 0.07 0.05 0.2 0.3 0.3 0.3 0.015 0.012
E, F 0.018 0.01 0.009
Q460 C, D 0.2 1 – 1.6 0.025 0.015 0.4 0.07 0.08 0.05 0.3 0.6 0.6 0.55 0.015 0.012
E, F 0.018 0.01 0.009
Q550 D 0.17 1 – 1.8 0.02 0.01 0.4 0.07 0.08 0.05 0.5 0.8 0.8 0.8 0.015 0.012
E 0.018 0.009
Q690 D 0.17 1 – 1.8 0.02 0.01 0.4 0.07 0.08 0.05 0.5 0.8 0.8 0.8 0.015 0.012
E 0.018 0.009

Table 2 Steel state before wind turbine tower manufacture and carbon equivalent of Chinese wind turbine tower steel materials

Grade State Quality Level Ceq (%)  ≦
thickness ≦ 40 (mm) 40 ≧ thickness ≦100 (mm)
Q235 hot rolling

controlled rolling

normalizing rolling

normalizing

 B, C, D, E 0.38 0.40
Q275 B, C, D, E 0.40 0.42
Q345 C, D, E, F 0.43 0.45
Q420 hot rolling

controlled rolling

normalizing rolling

 C, D, E, F 0.48 0.50
Q460 C, D, E, F 0.52 0.53
Q460 quenching

tempering

 C, D, E, F 0.48 0.50
Q550 D, E 0.55 0.60
Q690 D, E 0.58 0.65
Grade State Quality Level Ceq (%)  ≦
thickness ≦ 40 (mm) 40 ≧ thickness ≦100 (mm)
Q275 TMCP

TMCP + tempering

 C, D, E, F 0.34 0.35
Q345 C, D, E, F 0.39 0.40
Q420 C, D, E, F 0.43 0.45
Q460 C, D, E, F 0.45 0.47
Q550 D, E 0.48 0.50
Q690 TMCP + tempering D, E 0.50 0.52

Chinese Wind Turbine Tower Materials Mechanical Properties

Chinese GB standard has a strict steel mechanical property test regulation. For the steel plate with thickness over 12mm, the standard test sample is 10mm ╳ 10mm ╳ 55mm; for the steel plate with thickness under 12mm, the standard test sample is 10mm ╳ 7.5mm ╳ 55mm. Each test group has 3 test samples, and takes the average value as the test results. If there is any one test value is under 70% of the standard, the test staff must take another 3 samples from the same steel plate, and take the average value of the six samples.

Table 3 Wind turbine tower steel materials mechanical properties

Grade Level Yield Strength (N/mm2) ≧ Tensile Strength

(N/mm2)

 Percentage elongation of fracture

%

 Impact absorbed energy (kv2/J) ≧ Bending Test

D=diameter

a= sample thickness
Thickness (mm) Thickness (mm)
≦ 16 16 – 40 40 – 100 ≦ 16 16 – 100
Q235 B, C, D 235 225 215 360 – 510 24 34 D=2a D=3a
E 27
Q275 B, C, D 275 265 255 410 – 560 21 34
E 27
Q345 C, D 345 335 325 470 – 630 21 34
E, F 27
Q420 C, D 420 400 390 520 – 680 19 34
E, F 27
Q460 C, D 460 440 420 550 – 720 17 34
E, F 27
Q550 D, E 550 550 530 670 – 830 16 40
Q690 D, E 690 690 670 770 – 940 14 40

Foreign Steel Standard Similar Steel Grades

For the foreign wind farm owners that might not be so familiar with Chinese steel grades, we also provide a similar steel grades comparison table of different steel standards. Hope the comparison table can help you better choose the suitable steel material for your wind turbine tower manufacture.

Table 4 Main steel standards similar steel grades comparison

GB ASTM EN10025
Q235 A283M Gr.D S235
Q275 A709M Gr.36 S275
Q345 A709M Gr.50 S355
Q420 A283M Gr.E S420
Q460 A709M Gr.70 S460
Q550 Type 8 grade 80[550] S550
Q690 A709M Gr.100 S690