GB/T 28410-2012Structural steel plate for wind power tower (English PDF)

6.4 Mechanical and processing properties

6.4.1 Tensile test

Tensile test properties of steel plates shall be as specified in Table 6.

6.4.2 Charpy V-notch impact test

6.4.2.1 The impact temperature and impact absorbed energy of Charpy V-notch impact

test of steel plates shall be as specified in Table 6.

6.4.2.2 For steel plates with the thickness not less than 12 mm, take standard samples of 10 mm × 10 mm × 55 mm as the impact samples; for steel plates with the thickness less than 12 mm, take samples of 7.5 mm × 10 mm × 55 mm or 5 mm × 10 mm × 55 mm. The impact absorbed energy shall be not less than 75% or 50% of the values specified in Table 6 respectively. The use of samples of larger dimensions is preferred.

6.4.2.3 The impact test result of steel plates is calculated as the arithmetic mean value of a group of three samples. One test value is allowed to be less than the specified value but shall not be less than 70% of the specified value. Or else, another three samples shall be taken from the same steel plate for test; the arithmetic mean value of the test results of 6 samples in succession are not less than the specified value. The test results of two samples are allowed to be less than the specified value, but only one sample whose test result is less than 70% of the specified value.

6.4.3 The reduction percentage of cross section in the thickness direction of Z-direction

steel shall be as specified in GB/T 5313.

6.4.4 When the purchaser requires bending test, bending test shall be as specified in

Table 6. If the supplier can guarantee it, bending test can be omitted.

6.5 Surface quality

6.5.1 The surface of steel plates shall be free from bubbles, scars, cracks, folds, inclusions, tail scales, etc. Steel plates shall not be layered.

6.5.2 The surface of steel plates shall be free from. thin oxide scales and rust which impede the inspection of surface defects; surface roughness which is caused by falling off of oxide scales; scratches, indentations and other local defects. But their depth shall not be greater than half of the tolerance for thickness and the minimum thickness of steel plates shall be ensured.

6.5.3 The surface defects of steel plates are allowed to be repaired and removed by grinding, but the minimum thickness of steel plates shall be ensured, and the removing spots shall be smooth without sharp edges.

6.5.4 Surface quality can be as specified in GB/T 14977, as agreed on by the supplier and the purchaser.

6.6 Special requirements

6.6.1 As agreed on by the supplier and the purchaser, non-destructive testing for be carried out for steel plates. The inspection method can be as specified in GB/T 2970 or JB/T 4730.3. The reference standard and grade shall be stated in agreements or contracts.

6.6.2 As agreed on by the supplier and the purchaser, other items of inspection can also be carried out for steel plates.

Table 6 – Designation and mechanical properties

Designation Quality grade

Lateral lower yielda

ReL/(N/mm2)

>= Tensile strength

Rm/(N/mm2)

Percentage elongation after fracture

A/%

L0 = 5.65

Impact absorbed energyc,d

KV2/J

180° bending test d = bending diameter a = sample thickness

Thickness of steel plates/mm Thickness of steel plates/mm

<= 16 > 16 ~ 40 > 40 ~ 100 <= 16 > 16 ~ 100

Q235FT

B, C, D

235 225 215 360 ~ 510 24b d = 2a d = 3a

E 34

Q275FT

C, D

275 265 255 410 ~ 560 21b

E, F 34

Q345FT

C, D

345 335 325 470 ~ 630 21b

E, F 34

Q420FT

C, D

420 400 390 520 ~ 680 19b

E, F 34

Q460FT

C, D

460 440 420 550 ~ 720 17

E, F 34

Q550FT D 550 530 670 ~ 830 16 47 purchaser shall be entitled to carry out inspection and acceptance on any inspection item specified in this Standard or contracts.

8.2 Batch

8.2.1 Steel plates shall be accepted by batch. Each batch comprises steel plates of the same designation, quality grade, furnace number, thickness, rolling system and heat treatment system. The weight of each batch shall not be greater than 60 t.

8.2.2 Steel plates of TMCP or TMCP + tempering shall be inspected one by one. Steel plates of quenching + tempering shall be sampled and inspected for each heat treatment.

8.2.3 Batches of Z-direction steel shall be as specified in GB/T 5313.

8.3 Reinspection and criteria

8.3.1 Reinspection and criteria of mechanical properties

8.3.1.1 When the impact test results of steel plates fail to meet the specifications of

6.4.2.3, steel plates subjected to sampling shall not be accepted. Then take two sample products from the remaining part of the test unit and select a new group of three samples from each sample product. The test results of the two groups of samples shall pass; or else, the batch of steel plates shall eb rejected.

8.3.1.2 Reinspection and criteria of tensile test of steel plates shall be as specified in

GB/T 17505.

8.3.2 Reinspection and criteria of other inspection items

Reinspection and criteria of other inspection items of steel plates shall be as specified in GB/T 17505.

8.4 Rounding off of test results of mechanical properties and chemical

composition

Unless specified otherwise in contracts or orders, when it needs to be evaluated whether a test result complies with the specified value and that the test result of mechanical property and chemical composition shall be rounded off to the same digital place as that of the specified value, the method for its rounding off shall be as specified in YB/T 0810 Carbon equivalent shall be calculated according to equation before rounding off.