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In ChinaA 540 Grade B21 Class 4 material is SAE A 540/A 540M (2011) Alloy-Steel Bolting Materials for Special Applications Alloy-Steel Bolting Materials for Special Applications.
Chemical composition of A 540 Grade B21 Class 4, A 540 Grade B21 Class 4 mechanical properties, A 540 Grade B21 Class 4 datasheet, A 540 Grade B21 Class 4 equivalent grade, Heat treatment and temperature process of A 540 Grade B21 Class 4.
| SAE A 540/A 540M (2011) Alloy-Steel Bolting Materials for Special Applications | 
| C: | Max | 0.05 | 
| Si: | Max | 0.20 | 
| Mn: | Max | 0.50 | 
| P: | Max | Min | 
| S: | Max | Min | 
| Ni: | Max | remaining | 
| Cr: | 15.00 | 17.00 | 
| Al: | 4.00 | 5.00 | 
| Cu: | Max | Min | 
| Ti: | Max | 0.50 | 
| Fe: | 2.00 | 4.00 | 
| N: | Max | Min | 
| Mo: | Max | 0.50 | 
| B: | Max | 0.006 | 
| Zr: | Max | 0.05 | 
| Rp0.2 (MPa) | 161 (≥) | 
| Rm (MPa) | 968 (≥) | 
| AKV (J) | 12 | 
| A (%) | 14 | 
| Z (%) | 24 | 
| Hardness | HBW 321 | 
| A 540 Grade B21 Class 4 Round bar: | 1mm-800mm | 
| A 540 Grade B21 Class 4 Square bar: | 10mm * 10mm-600mm *600mm | 
| A 540 Grade B21 Class 4 Flat bar: | Thickness:8mm-800mm Width:10mm to 1500mm | 
| A 540 Grade B21 Class 4 Sheet or Plate: | Thickness:3mm-80mm Width:1.5mm to 1500mm | 
| A 540 Grade B21 Class 4 Strip or Coil: | Thickness:0.1mm-3mm Width:1.5mm-1500mm | 
| A 540 Grade B21 Class 4 Forgings: | Shafts with flanks/pipes/tubes/slugs/donuts/cubes/other shapes |