GB 1298-1986 Carbon Tool Steels – Technical Requirements
This standard supersedes GB 1298-77. Published by the National Bureau of Standards on June 7, 1986. Effective May 1, 1987.
Issued by the Ministry of Metallurgical Industry, People’s Republic of China. Drafted by Chongqing Special Steel Works, Dalian Steel Works, and Information & Standards Research Institute of the Ministry of Metallurgical Industry.
Scope
This standard applies to hot-rolled, forged, cold-drawn, and bright carbon tool steel bars. The chemical composition requirements also apply to ingots, blooms, and their finished products.
1. Classification
Steel products are classified according to the processing method into hot pressure working steels, cold pressure working steels, and cutting machining steels. The intended processing method shall be specified in the purchase contract.
2. Dimensions, Shapes and Tolerances
2.1 Hot-rolled steel bars: Dimensions, tolerances, and shapes shall comply with Grade 2 in GB 702-86.
2.2 Forged steel bars: Dimensions, tolerances, and shapes shall comply with GB 908-87.
2.3 Cold-drawn and bright steel bars: Dimensions, tolerances, and shapes shall comply with Grade 11 of GB 905-82, GB 906-82, GB 907-82, and GB 3207-82.
2.4 Short lengths: Short lengths shall not be delivered as mixed batches.
3. Technical Requirements
3.1 Grades and Chemical Composition (%)
| No. | Grade | C | Si | Mn | S | P |
|---|---|---|---|---|---|---|
| 1 | T7 | 0.65~0.74 | 0.35 | 0.25~0.40 | 0.030 | 0.035 |
| 2 | T8 | 0.75~0.84 | 0.35 | 0.25~0.40 | 0.030 | 0.035 |
| 3 | T8Mn | 0.80~0.90 | 0.35 | 0.40~0.60 | 0.030 | 0.035 |
| 4 | T9 | 0.85~0.94 | 0.35 | 0.25~0.40 | 0.030 | 0.035 |
| 5 | T10 | 0.95~1.04 | 0.35 | 0.25~0.40 | 0.030 | 0.035 |
| 6 | T11 | 1.05~1.14 | 0.35 | 0.25~0.40 | 0.030 | 0.035 |
| 7 | T12 | 1.15~1.24 | 0.35 | 0.25~0.40 | 0.030 | 0.035 |
| 8 | T13 | 1.25~1.35 | 0.35 | 0.25~0.40 | 0.030 | 0.035 |
Si, Mn values are maximum unless shown as range. S, P are maximum limits.
3.1.1 Special Requirements
- Premium quality (indicated by “A” suffix): Sulfur ≤ 0.020%, Phosphorus ≤ 0.030%
- Open hearth melted steel: Sulfur ≤ 0.035% for quality steel; ≤ 0.025% for premium quality
- Residual elements: Cr ≤ 0.25%, Ni ≤ 0.20%, Cu ≤ 0.30%
- For lead bath quenched wire: Cr ≤ 0.10%, Ni ≤ 0.12%, Cu ≤ 0.20%, total ≤ 0.40%
- For hardenability testing: small amounts of alloying elements may be added upon agreement
3.2 Delivery Condition
Steel products shall be delivered in annealed condition. Upon agreement, may also be delivered in non-annealed condition.
3.3 Hardness
| Grade | Annealed HB | Indentation mm | Quenching Temp (C) | Quenched HRC |
|---|---|---|---|---|
| T7 | – | – | 760-780 water | – |
| T8 | 187 max | 4.40 min | 760-780 water | 62 min |
| T8Mn | 187 max | 4.40 min | 760-780 water | 62 min |
| T9 | 192 max | 4.35 min | 760-780 water | 62 min |
| T10 | 207 max | 4.20 min | 760-780 water | 62 min |
| T12 | 207 max | 4.20 min | 760-780 water | 62 min |
| T13 | – | – | 760-780 water | 62 min |
3.4 Fracture and Acid-Etched Macrostructure
- Annealed steel bars with cross-section ≤ 100mm shall be examined for fracture. The fracture surface shall be uniform with fine grain. No visible residual shrinkage, inclusions, lamination, cracks, blowholes, white spots, or graphite carbon.
- Acid-etched macrostructure may be inspected instead of fracture test upon request. No visible residual shrinkage, inclusions, cracks, blowholes, or white spots on transverse sections.
3.5 Microstructure
Pearlite structure (500x): T7, T8, T8Mn, T9: Grade 3 or better. T10, T11, T12, T13: Grade 4 or better.
Pro-eutectoid carbide network (500x): Cross-section ≤ 60mm: Grade 2 max. >60~100mm: Grade 3 max. >100mm: by agreement.
T7, T8, and hot pressure working steels are exempt from pro-eutectoid carbide network inspection.
3.5.3 Decarburization Depth
- Hot-rolled and forged steel: One-side total decarb depth ≤ (0.25 + 1.5% x D) mm, where D is nominal cross-section size (mm)
- Cold-drawn steel ≤ 16mm: ≤ 1.5% x D; > 16mm: ≤ 1.3% x D
- Cold-drawn steel for high-frequency quenching: ≤ 1.0% x D
- Bright steel: No decarburization permitted
3.6 Hardenability
Upon purchaser’s request and mutual agreement, hardenability may be tested. Required grade or case depth to be specified in contract.
3.7 Surface Quality
- Hot-rolled and forged: No visible cracks, laps, scabs, or inclusions. Defect removal depth: ≤80mm = half tolerance; 80-140mm = tolerance; >140mm = 4% of cross-section.
- Cutting machining: Local defects allowed up to half tolerance for ≤100mm, full tolerance for >100mm.
- Cold-drawn: Clean, smooth surface. Minor defects within half tolerance permitted.
- Bright steel: No decarburization. Comply with YB 247-64.
4. Test Methods
| No. | Inspection | Sampling | Method |
|---|---|---|---|
| 1 | Chemical composition | Per heat | GB 222-84 / GB 223 |
| 2 | Annealed hardness | 3 per batch | GB 231-84 |
| 3 | Quenched hardness | Per batch | GB 230-83 |
| 4 | Fracture | Per batch | GB 1814-79 |
| 5 | Acid-etched macro | 2 per batch | GB 226-76 |
| 6 | Pearlite | Per batch | YB 28-59 |
| 7 | Carbide network | Per batch | YB 28-59 |
| 8 | Decarburization | 3 per batch | GB 224-78 |
| 9 | Hardenability | Per agreement | GB 227-63 |
| 10 | Dimensions | Each bar | Micrometer/caliper |
| 11 | Surface | Each bar | Visual |
5. Inspection Rules
Batches consist of same heat, same size, same processing method, same annealing furnace lot. Retest rules comply with GB 2101-80.
6. Packaging, Marking and Quality Certificate
Shall comply with GB 2101-80.