1. Chemical composition (cast analysis)
Source: GB/T 28906-2025, Table 4 (wire rod for boron-containing steels for quenching and tempering); PDF page 10. Mass fractions are expressed in %.
| Element | Mass fraction / % |
|---|---|
| C | 0.23-0.28 |
| Si | 0.10-0.30 |
| Mn | 0.90-1.20 |
| P | ≤0.025 |
| S | ≤0.020 |
| B | 0.0008-0.0035 |
| Al_t | 0.020-0.060 |
Table 4 notes: a Si lower limit below 0.10% may be agreed and specified in the contract. If hardenability and mechanical properties meet the requirements, a B lower limit of 0.0005% may be agreed. A Ti/N ratio may be agreed and specified in the contract. Where acid-soluble aluminium is specified, Al_s is 0.015%–0.055%. Under note e, chromium may be added to ensure hardenability and mechanical properties, with the amount agreed between purchaser and supplier.
GB/T 28906-2025, 7.1.5: residual Ni, Cr and Cu shall each be ≤0.20%, and residual Mo ≤0.06%; the explicitly specified alloy-element limits for the grade take precedence. Permissible deviations in product analysis are governed by GB/T 222. The composition basis and finished-wire requirements are listed separately.
2. Finished-wire properties · GB/T 5953-2026
Published on 2026-05-25; effective from 2026-12-01. This page presents that edition. The edition and delivery condition applicable to an order must be specified.
| Delivery condition | Nominal diameter d / mm | Rm / MPa | Z / % | Hardness (reference only for SA, SALD and ASALD) | Rp0.2 / MPa | A / % | Source |
|---|---|---|---|---|---|---|---|
| SA | ≤610 | ≥65 | ≤90 HRBW | Table 3; PDF page 10 |
A blank cell means that the row does not specify a value; it does not mean zero. Do not apply properties from another grade or an HD, SA, SALD or ASALD condition not listed for this grade. For diameters greater than 20 mm, reduction of area Z is reduced by 5% in accordance with the applicable table note. Hardness is for reference only in SA, SALD and ASALD conditions; the HD hardness requirements in Table 2 apply. For delivery in straight lengths or in a polished condition, a 10% variation in mechanical properties is permitted. Mechanical properties may also be agreed between purchaser and supplier (6.5.5–6.5.6).
SA: cold drawing + spheroidizing annealing. SALD: cold drawing + spheroidizing annealing + light drawing. ASALD: annealing + cold drawing + spheroidizing annealing + light drawing. The delivery condition shall be specified in the contract. Table 5 note: reduction of area for d<3.00 mm is for reference only (this page contains no Table 5 property row).
3. Dimensions, shape and coil mass
6.4: nominal diameter 1.00–45.00 mm. For d≤20.00 mm, diameter tolerance is grade 10 in GB/T 342-2017, Table 2; for 20.00<d≤25.00 mm, grade 11 in GB/T 702-2026, Table 9; for d>25.00 mm, by agreement. Out-of-roundness shall not exceed 1/2 of the diameter tolerance.
Polished wire in straight lengths: grade 10 of GB/T 3207-2025 for d≤16.00 mm and grade 11 for 16.00<d≤25.00 mm; for d>25.00 mm, by agreement. Coils shall be orderly and free of distortion that impairs use. Straight lengths are normally 2000–6000 mm, with straightness deviation ≤2 mm/m.
| Nominal diameter d / mm | Minimum coil mass / kg |
|---|---|
| 1.00≤d≤2.00 | 20 |
| 2.00<d≤5.00 | 30 |
| 5.00<d≤6.50 | 50 |
| d>6.50 | 100 |
Each coil shall consist of one continuous length of wire without joints of any kind. Where a nominal coil mass of 100–2500 kg is agreed, the permitted mass deviation is ±15%. The mass of wire in straight lengths is by agreement.
4. Surface quality, upsetting test and microstructure
6.3: the wire surface shall be smooth and free of cracks, folds, scabs, laminations, drawing marks, hairline cracks and rust that impair cold heading or cold forming. Isolated pits and depressions shall be no deeper than 1/2 of the diameter tolerance; isolated indentations and scratches that do not impair use shall be no deeper than 1/4 of the diameter tolerance. Surface coatings are by agreement.
6.6: HD wire shall withstand upsetting to 1/2 of the original specimen height; SA, SALD and ASALD wire to 1/3, without cracks or splits. The upsetting test is not required for d≤5.0 mm. Under 6.7, SA, SALD and ASALD wire shall have a spheroidized microstructure rated at least grade 4 in accordance with GB/T 38770.
5. Decarburization depth
6.8: decarburization is inspected for SA, SALD and ASALD wire with average C≥0.30%. Values below are depths measured from one side of the wire. Polished wire in straight lengths shall be free of decarburization.
| Nominal diameter d / mm | Complete decarburization depth / mm | Total decarburization depth / mm |
|---|---|---|
| d≤7.00 | ≤0.01 | ≤0.10 |
| 7.00<d≤15.00 | ≤0.02 | ≤0.15 |
| 15.00<d≤25.00 | ≤0.03 | ≤0.25 |
| 25.00<d≤32.00 | ≤0.04 | ≤0.32 |
| d>32.00 |
For d>32.00 mm, permissible decarburization depth is by agreement. Decarburization guarantees for annealed wire shall not automatically be applied to HD wire or grades outside the stated conditions.
6. Inspection, packaging and inspection certificate
| Inspection item | Sampling quantity and location | Test method |
|---|---|---|
| Chemical composition | 1 coil (or straight length) per heat; GB/T 20066 | GB/T 4336、223、20123、20125 |
| Tensile test | One end of each of 3 coils (or straight lengths) | GB/T 228.1 |
| Upsetting test | One end of each of 3 coils (or straight lengths) | YB/T 5293 |
| Hardness | One end of each of 3 coils (or straight lengths) | GB/T 230.1 |
| Microstructure | One end of each of 3 coils (or straight lengths) | GB/T 13298、38770 |
| Decarburization depth | One end of each of 3 coils (or straight lengths) | GB/T 224 |
| Dimensions | Every coil (or straight length), over its full length | Measuring instruments of suitable accuracy |
| Surface quality | Every coil (or straight length), over its full length | Visual inspection |
Table 7: when fewer than 3 coils are ordered, sample every coil. Other sampling quantities and locations may be agreed. Referee chemical analysis is in accordance with GB/T 223. Each batch shall have the same heat number, dimensions, heat-treatment condition and delivery condition. Inspection, acceptance, retesting, packaging, marking, storage and inspection certificates are governed by GB/T 2103. Results are evaluated using rounded-value comparison in accordance with GB/T 8170.