ASTM A302 Grade B steel covers manganese-molybdenum and manganese- molybdenum- nickel alloy steel plates intended particularly for welded boiler and other pressure vessels.
ASTM A302 Grade B material chemical composition
| Grade | C,max | Mn | P max | S max | Si | Mo | ||
| ≤1in(25mm),incl | >1≤2in.(50mm),incl | >2in.(50mm) | ||||||
| Grade B | 0.20 | 0.23 | 0.25 | 1.07-1.62 | 0.035 | 0.035 | 0.13-0.45 | 0.41-0.64 |
ASTM A302 Grade B pressure vessel steels mechanical properties
| Grade | Tensile strength,ksi,mpa | Yield strength,min,ksi,mpa | Elongation in 8in.[200mm],min,% | Elongation in 2in.[50mm],min,% |
| Grade B | 80-100[550-690] | 50[345] | 15 | 18 |
ASTM A302 Grade B steel heat treatment:
ASTM A302 Grade B steel plate 2in.[50mm] and under in thickness are normally supplied in the as-rolled condition.plates may be ordered normalized or stress relieved,or both.
ASTM A302 Grade B steel plates over 2in.[50mm] in thickness shall be normalized.
When normalizing ASTM A302 Grade B steel plates 4in.[100mm] or over in thickness,the cooling rate may be accelerated by air blasting or liquid quenching to obtain mechanical properties comparable to those developed by normalizing plates in the lesser thicknesses.
If approved by the purchaser,for ASTM A302 Grade B steel plates less than 4in.[100mm] in thickness,cooling rates faster than those obtained by cooling in air are permissible for improvement of toughness,provided the plates are subsequently tempered in the temperature range from 1100 to 1300 oF [595 to 705 oC] .
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