For quick reference, here are the most common Chinese carbon steel grades used in fastener and general manufacturing applications, grouped by carbon content and typical use.
Low-Carbon Steels (C ≤ 0.25%)
Low-carbon steels are characterized by good formability, weldability, and ductility. They are typically used in the as-rolled or cold-formed condition without heat treatment.
| Grade | Carbon % | Key Features | Typical Applications |
|---|---|---|---|
| Q195 | ≤0.12% | Low strength, good formability | Wire, nails, light gauge parts, low-strength fasteners (Class 4.6) |
| Q215 | 0.09-0.15% | Slightly stronger than Q195 | General light-duty fasteners, welded structures |
| Q235 | 0.14-0.22% | Most common structural steel, good balance of strength and formability | Class 4.8 bolts, nuts, washers, general construction |
| 08#/10# | 0.05-0.13% | Excellent plasticity and drawing properties | Deep-drawn parts, rivets, small fasteners |
| 15#/20# | 0.15-0.23% | Good strength and weldability | General machinery parts, carburized parts |
| ML08Al | 0.05-0.12% | Cold heading quality, aluminum-killed | Self-drilling screws, small rivets, cold-formed parts |
| ML10 / ML20 | 0.08-0.23% | Cold heading quality, controlled surface | General cold-headed fasteners, Class 4.8-5.8 |
Medium-Carbon Steels (C 0.25-0.60%)
Medium-carbon steels offer higher strength than low-carbon grades and are typically used in the heat-treated condition (quenched and tempered).
| Grade | Carbon % | Key Features | Typical Applications |
|---|---|---|---|
| 30#/35# | 0.27-0.37% | Good strength, machinable | Class 8.8 bolts, shafts, machinery parts |
| 40#/45# | 0.37-0.50% | The workhorse of 8.8-grade—excellent balance of strength and toughness | Class 8.8 fasteners, gears, axles, spindles |
| 50#/55# | 0.47-0.57% | Higher strength, wear-resistant | Heavier-duty fasteners, wear parts |
| ML35/ML40 | 0.32-0.45% | Cold heading quality, killed steel | 8.8-grade cold-headed bolts and nuts |
| ML45 | 0.42-0.50% | Cold heading quality for higher strength | Heavy-duty cold-formed parts, larger diameter 8.8 bolts |
| SWRCH35K (JIS) | 0.32-0.38% | Popular cold heading grade (JIS equivalent) | Widely used for 8.8-grade fasteners in automotive and industrial applications |
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