Abrasion resistant steel plate having excellent low-temperature toughness and method for manufacturing the same

An abrasion resistant steel plate comprising:

• C:
• 0.10 to less than 0.20%, by mass %;
• Si:
• 0.05 to 0.5%, by mass %;
• Mn:
• 0.5 to 1.5%, by mass %;
• Cr:
• 0.05 to 1.20%, by mass %;
• Nb:
• 0.01 to 0.08%, by mass %;
• B:
• 0.0005 to 0.003%, by mass %;
• Al:
• 0.01 to 0.08%, by mass %;
• N:
• 0.0005 to 0.008%, by mass %;
• P:
• not more than 0.05%, by mass %;
• S:
• not more than 0.005%, by mass %;
• O:
• not more than 0.008%, by mass %;
• and
• remaining Fe and unavoidable inevitable impurities as a balance,
• wherein:
• the steel plate includes fine precipitates that are 50 nm or less in diameter and that have a density of 50 or more particles per 100 μm2,
• the steel plate has a lath martensitic structure from the surface of the steel plate to at least a depth of ¼ of the plate thickness, the lath martensitic structure having an average grain size of not more than 20 μm such that the average grain size is the average grain size of crystal grains surrounded by high-angle grain boundaries having an orientation difference of 15° or more, and
• the steel plate has a Brinell hardness (HBW10/3000) of 361 or more.