Abstract
Influence of Mn on the hardness and impact resistance of Cr-Mo cast steels containing Cr 1.2%, Mo 0.25%, and Ni-Cr-Mo cast steels containing Ni 2%, Cr 1.5%, Mo, 0.4% were investigated. The results obtained were summarized as follows:
(A) Cr-Mo-Mn cast steel: The hardness increased with addition of the Mn increase, and with 1.8% Mn addition the hardness reached to the maximum value. The impact resistance showed the maximum value at Mn content 1.0-1.4%. The first temper-brittleness, which took place at 300-400°C, was marked as the Mn content increased.
(B) Ni-Cr-Mo-Mn cast steel: The hardness increased with increase of the Mn content.
The impact resistance increared slightly with the addition of Mn up to 1%, but with higher Mn addition it decreased rapidly. The first temper-brittleness took place at about 400°C, and it showed a large sensibility as the Mn content increased.
In general the Ni-Cr-Mo cast steel was somewhat lower in strength, but addition of Mn to these cast steel, the strength and toughness was markedly increased due to the quenching properties and uniformity of heat-treatment.
