1. Chemical Composition
Chemical composition ranges and limits for carbon steel (mass fraction, %)
| Delivery Condition | IFI Steel Grade | C Lower Limit | C Upper Limit | Mn Lower Limit | Mn upper limit | P upper limit | S upper limit | Si requirements |
|---|---|---|---|---|---|---|---|---|
| AlK, SiFg, SiCg | IFI-1018 | 0.15 | 0.19 | 0.65 | 0.85 | 0.020 | 0.020 | See silicon content requirements |
Abbreviations: AlK = aluminum-killed; R = rimmed steel; SiFg = silicon-killed fine-grain; SiCg = silicon-killed coarse-grain; CgP = coarse-grain practice. The "B" in boron steel grades indicates boron-added steel; boron and titanium content requirements shall comply with ASTM F2282.
Permissible deviations for product analysis (%)
| Element | Specified range or upper limit | Permissible deviation (above upper limit or below lower limit) |
|---|---|---|
| C | ≤ 0.25 | 0.02 |
| C | > 0.25 and ≤ 0.55 | 0.03 |
| Mn | ≤ 0.90 | 0.03 |
| Mn | > 0.90 and ≤ 1.65 | 0.06 |
| P | Exceeding the upper limit is permitted only | 0.008 |
| S | Exceeding the upper limit is permitted only | 0.008 |
| Si | ≤ 0.30 | 0.02 |
| Cu | Exceeding the upper limit is permitted only | 0.03 |
| Sn | Exceeding the upper limit is permitted only | 0.01 |
| Ni | Exceeding the upper limit is permitted only | 0.03 |
| Cr | Exceeding the upper limit is permitted only | 0.03 |
| Mo | Exceeding the upper limit is permitted only | 0.01 |
| V | Exceeding the upper limit is permitted only | 0.01 |
| B | Not applicable unless misapplication is indicated | — |
Silicon content requirement (mass fraction, %)
| IFI Steel Grade | SiFg lower limit | SiFg upper limit | SiCg/CgP lower limit | SiCg/CgP upper limit | AlK upper limit | R upper limit |
|---|---|---|---|---|---|---|
| IFI-1018 | 0.15 | 0.30 | 0.15 | 0.30 | 0.10 | Not applicable |
2. Mechanical Properties
Grade: IFI-1018. The listed tensile strength is the maximum value, and the reduction of area is the minimum value.
| Material Condition | Maximum Tensile Strength (ksi) | Minimum Reduction of Area (%) |
|---|---|---|
| Wire Rod/Bar - Annealed | 68 | 62 |
| Wire Rod/Bar - Spheroidizing Annealed | 65 | 65 |
| Steel Wire - Spheroidizing Annealed to Finished Size (SAFS) | 63 | 68 |
| Steel Wire - Intermediate Annealed Process (AIP) | 76 | 60 |
| Steel Wire – Intermediate Spheroidizing Annealing (SAIP) | 68 | 62 |
Note A: For aluminum-killed steel, reduce the maximum tensile strength by 3 ksi and increase the minimum reduction of area by 1 percentage point; for rimmed steel, reduce by 5 ksi and increase by 2 percentage points, respectively. For AIP and SAIP wire with a diameter less than 0.200 in., increase the maximum tensile strength by 50 psi for each 0.001 in. decrease in diameter. The reduction of area test does not apply to wire with a diameter less than 0.092 in.
3. Microstructure and Spheroidization Requirements
The minimum rating for spheroidizing annealed material is G2 or L2; the optimal spheroidization rate shall be no less than 90%. The austenitic grain size of fine-grain steel and the testing method shall comply with the relevant provisions of ASTM F2282.
4. Decarburized Layer Limits
Applicable to killed steel with a carbon content exceeding 0.15%; limits are determined based on the nominal diameter of the specimen.
| Nominal Diameter (in.) | Maximum Depth of Free Ferrite Layer (in.) | Maximum Total Average Affected Depth (TAAD) (in.) | Maximum Depth at Most Unfavorable Location (in.) |
|---|---|---|---|
| ≤ 25/64 | 0.001 | 0.005 | 0.008 |
| > 25/64 and ≤ 5/8 | 0.001 | 0.006 | 0.009 |
| > 5/8 and ≤ 55/64 | 0.001 | 0.007 | 0.011 |
| > 55/64 and ≤ 1 | 0.001 | 0.008 | 0.012 |
| > 1 and ≤ 1-1/2 | 0.001 | 0.010 | 0.015 |
5. Surface Quality and Coating
The oxide scale on hot-rolled material shall be removable by pickling or mechanical descaling. The surfaces of wire rod, bars, and steel wire shall be free from defects that impair usability, such as folds, holes, pitting, scratches, and laps. The type and requirements of the coating shall be determined by the purchaser based on the cold-forming process and the technical agreement of the order.