Effect of Cooling Path on Microstructures and Hardness of Hot-Stamped Steel
Abstract
:1. Introduction
2. Materials and Experimental Procedure
3. Results and Discussion
3.1. Continuous Cooling Transformation Behavior
3.1.1. Microstructure and Hardness
3.1.2. Start and Finish of Phase Transformation
3.2. Discontinuous Cooling Process
3.2.1. Microstructures
3.2.2. Hardness
4. Conclusions
- In the continuous cooling process, there is a critical cooling rate of 25 for the formation of a fully martensitic microstructure in hot-stamped 22MnB5 steel.
- The secondary cooling rate greatly affects the auto-tempering of martensite transformed. The amount of carbides decreases with the secondary cooling rate. The hardness increases with secondary cooling rate when the cooling rate is lower than 25 , above which the hardness is not sensitive to the cooling rate.
- The primary cooling rate determines whether a martensite structure is formed. A higher primary cooling rate will inhibit the martensite auto-tempering and reduce and refine carbides. The discrepancy in hardness between the primary cooling rate diminishes when the secondary cooling rate is above 25 .
Author Contributions
Funding
Conflicts of Interest
References
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C | Si | Mn | P | S | Als | Ti | Nb | N | B | Cr | Fe |
---|---|---|---|---|---|---|---|---|---|---|---|
0.22 | 0.25 | 1.26 | 0.01 | 0.0018 | 0.031 | 0.029 | 0.028 | 0.0053 | 0.0026 | 0.2884 | Bal. |
Cooling Rate () | Ferrite and Pearlite () | Bainite () | Martensite () | |||
---|---|---|---|---|---|---|
Start | Finish | Start | Finish | Start | Finish | |
0.5 | 726 | 545 | - | - | - | - |
1 | 679 | - | - | 454 | - | - |
3 | 587 | - | - | 387 | - | - |
8 | 554 | - | - | 271 | - | - |
15 | - | - | 503 | - | 226 | |
25 | - | - | - | - | 392 | 208 |
30 | - | - | - | - | 399 | 203 |
40 | - | - | - | - | 394 | 213 |
50 | - | - | - | - | 402 | 215 |
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Xu, Y.; Ji, Q.; Yang, G.; Bao, S.; Zhao, G.; Miao, X.; Mao, X. Effect of Cooling Path on Microstructures and Hardness of Hot-Stamped Steel. Metals 2020, 10, 1692. https://doi.org/10.3390/met10121692
Xu Y, Ji Q, Yang G, Bao S, Zhao G, Miao X, Mao X. Effect of Cooling Path on Microstructures and Hardness of Hot-Stamped Steel. Metals. 2020; 10(12):1692. https://doi.org/10.3390/met10121692
Chicago/Turabian StyleXu, Yaowen, Qiumei Ji, Gengwei Yang, Siqian Bao, Gang Zhao, Xiaodong Miao, and Xinping Mao. 2020. "Effect of Cooling Path on Microstructures and Hardness of Hot-Stamped Steel" Metals 10, no. 12: 1692. https://doi.org/10.3390/met10121692