1. Chemical Composition
Composition source and applicability
Reference composition for the stated standard edition, not heat analysis. Confirm the order standard and the separate requirements for feedstock and finished product.
Source: GB/T 6478-2015 · ML40Cr · p.9
| Element | Mass fraction / % |
|---|---|
| C | 0.38~0.43 |
| Si | 0.10~0.30 |
| Mn | 0.60~0.90 |
| P | ≤0.025 |
| S | ≤0.025 |
| Cr | 0.90~1.20 |
2. Mechanical Properties
Table 4 – Mechanical properties of alloy steel wire intended for quenching and tempering
Reference edition: GB/T 5953.1-2009, Table 4. Under clause 3.2, SALD means cold drawn, spheroidize annealed and lightly drawn; SA means cold drawn and spheroidize annealed. These reference data do not establish compliance with a different edition or the condition of a delivered heat.
| Grade a) | Diameter/mm | SALD | SA | ||||
|---|---|---|---|---|---|---|---|
| Tensile strength Rm/MPa | Rockwell hardness/HRB | Reduction of area Z / % | Tensile strength Rm/MPa | Reduction of area Z / % | Rockwell hardness/HRB | ||
| ML38CrA ML40Cr | ≤6.00 | 530-730 | - | ≥50 | 430-600 | ≥55 | ≤89 |
| >6.00-12.00 | 500-650 | - | |||||
| >12.00-25.00 | 480-630 | ≤91 | |||||
| Note: For steel wire with diameter below 3.00 mm, reduction of area is given for information only. a) The chemical composition of grades may be referenced to GB/T 6478. | |||||||
2.1 For wire delivered in the HD condition, mechanical properties shall be determined by agreement between the supplier and the purchaser.
2.2 The mechanical properties of quenched and tempered steel wire in the delivery condition shall comply with the provisions of Table 3 and Table 4.
2.3 When wire is delivered in straight lengths or in a polished condition, a 10% variation in mechanical properties is permitted.
2.4 For wire with a nominal diameter greater than 25.00 mm, the mechanical properties shall be determined by agreement between the supplier and the purchaser.
2.5 The mechanical properties for grades not listed in the table shall be determined by agreement between the supplier and the purchaser.
2.6 Upsetting: Wire samples shall be cold upset to one-half of their original height without surface cracks or fissures. By mutual agreement, upsetting may also be performed to one-third or one-quarter of the original sample height.
3. Microstructure
Table 6 Permissible range for decarburized layer depth
For spheroidizing annealed wire, the spheroidized microstructure may be inspected upon the purchaser's request and as specified in the contract; the acceptance criteria and test methods shall be agreed upon by the supplier and the purchaser.
| Nominal diameter of wire | Depth of complete decarburization | Total decarburized layer depth |
|---|---|---|
| ≤8.00 | ≤0.02 | ≤0.10 |
| >8.00-15.0 | ≤0.02 | ≤0.15 |
| >15.0-25.0 | ≤0.03 | ≤0.20 |
| >25.0-45.0 | By agreement | By agreement |
3.1 Decarburized layer: Upon the purchaser's request and as specified in the contract, the decarburized layer on the wire surface may be inspected. The permissible depth of the total decarburized layer (ferrite + transition zone) and the complete decarburized layer on one side shall comply with Table 6. Special requirements for the decarburized layer shall be determined by agreement between the supplier and the purchaser. For wire grades with a carbon content not greater than 0.30%, the test method shall be agreed upon by the supplier and the purchaser.
3.2 Carburization: The wire surface shall be free from carburization. Inspection may be omitted if the supplier can provide assurance.
4. Surface quality
4.1 The wire surface shall be smooth and free from cracks, scabs, folds, laminations, drawing marks, and rust. However, individual pits, raised surfaces, indentations, and scratches with a depth not exceeding half the diameter tolerance are permitted. Wire delivered in the annealed condition may exhibit oxidation colors on the surface.
4.2 Requirements for wire surface coatings shall be determined by mutual agreement between the supplier and the purchaser.