K390和S590刀刃均选择三个淬火温度1100 ℃，1150 ℃，1180 ℃，相同的回火工艺（深冷和550 ℃回火三次），对热处理后的样品进行抗弯强度测试。K390随着热处理温度的上升，抗弯强度先增加后减少，在1150 ℃时强度可达5486 MPa；S590的抗弯强度随着温度的上升而下降，1100 ℃时抗弯强度最高，为5473 MPa。在1100℃时，K390发生准解理断裂，1150 ℃时韧窝明显，随着温度的上升，碳化物长大，裂纹源容易在粗大的碳化物附近萌生，因而导致强度下降。S590断口韧窝数量随淬火温度的上升而逐渐减少，撕裂岭特征减少，逐渐观察不到放射状条纹，断裂方式由准解理断裂向脆性的解理断裂过渡，抗弯强度下降。

Three quenching temperatures of 1100 ℃, 1150 ℃ and 1180 ℃ are selected for K390 and S590 blades, and the same tempering process (cryogenic and 550 ℃ tempering for three times) is used to test the bending strength of the samples after heat treatment. With the increase of heat treatment temperature, the bending strength of K390 increases first and then decreases, and the strength can reach 5486 MPa at 1150 ℃; The bending strength of S590 decreases with the increase of temperature, and the bending strength is the highest at 1100 ℃, 5473 MPa. At 1100 ℃, K390 undergoes quasi-cleavage fracture, and at 1150 ℃, dimples are obvious. With the increase of temperature, carbides grow up, and the crack source is easy to initiate near the coarse carbides, resulting in a decrease in strength. With the increase of quenching temperature, the number of dimples on the S590 fracture surface decreases gradually, the tear ridge feature decreases, the radial stripes are gradually not observed, the fracture mode transitions from quasi-cleavage fracture to brittle cleavage fracture, and the bending strength decreases.