Formation Analysis of Edge Cracks of 33MnCrTiB Fork Steel
Abstract
:1. Introduction
2. Research Plan
2.1. Production Process
2.2. Research Methods
3. Experiment Results and Analysis
3.1. HRC Hardness Characterization
3.2. Observation and Analysis of Microstructure
3.3. Inclusions Analysis
3.3.1. Macro-Inclusions in Casting Billet
3.3.2. Micro-Inclusions in Rolling Fork Steel
Micro-Inclusions in Severe Porosity Samples
Inclusions in General Porosity Samples
3.4. Mold Flux Analysis
4. Conclusions
- (1)
- A large number of micro-inclusions with size below 10 μm Ti(C,N), CaO–MgO–SiO2–Al2O3–TiO2 and CaS–MnS are found in the porosity steel. It indicates that there are some problems with slagging and calcium treatment process. The more than 50 μm inclusions of CaO–Al2O3–SiO2–TiO2–(MgO), Al2O3, and CaO–Al2O3 oxides are also found in the billets, these large inclusions may become the sources of small cracks in the rolling process.
- (2)
- The unstable crystallizer liquid level and the unqualified mold flux in continuous casting process lead to the slag entrapment on the liquid surface or slag sticking on the billet shell, resulting in CaO–MgO–SiO2–Al2O3–K2O–Na2O inclusions remained in surface cracks.
- (3)
- The process from continuous casting through reheating to rolling was not coordinated, rolling deformation was not uniform, so that the segregation and porosity are difficult to reduce, then porosity deviation from the center occurs to induce new cracks.
- (4)
- The inclusions must be removed in the refining process, especially the large D and Ds inclusions. It is necessary to stabilize the casting speed, and keep the liquid level of the crystallizer stable. A mold flux having a suitable viscosity, a fast melting rate, a low melting point and C content should be selected. The surface defects of the slab need be cleaned in time, and the compression ratio and cooling strength of each rolling process should be strictly controlled to ensure the deformation of the core of the slab.
Author Contributions
Funding
Acknowledgments
Conflicts of Interest
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C | Si | Mn | P | S | Cr | Ti | B | |
---|---|---|---|---|---|---|---|---|
Defective | 0.33 | 0.26 | 1.36 | 0.011 | 0.005 | 0.4 | 0.034 | 0.0013 |
Standard | 0.30~0.35 | 0.17~0.37 | 1.25~1.50 | ≤0.035 | ≤0.035 | 0.30~0.60 | ≥0.015 | 0.0005~0.0030 |
Original Weight | Remaining Weight | Electrolytic Weight | Total Weight of Inclusions | Size Classification, µm | ||||
---|---|---|---|---|---|---|---|---|
<80 | 80~140 | 140~300 | >300 | |||||
kg | kg | kg | mg | mg/10 kg | mg | mg | mg | mg |
4.438 | 0.251 | 4.178 | 2.60 | 6.21 | 0.10 | 0.20 | 1.20 | 1.10 |
O | Mg | Al | Si | S | K | Ca | Ti | Cr | Mn | Fe | Cu | Zr | |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | 50.85 | 1.33 | 12.76 | 23.22 | 3.22 | 3.05 | 1.85 | 0.52 | 3.2 | ||||
2 | 60.39 | 22.58 | 3.21 | 5.03 | 1.71 | 7.09 | |||||||
3 | 50.12 | 0.85 | 23.33 | 12.08 | 1.62 | 3.87 | 3.06 | 5.09 | |||||
4 | 45.98 | 34.43 | 7.55 | 0.98 | 0.95 | 2.31 | 0.51 | 7.28 | |||||
5 | 60.89 | 21.2 | 2.61 | 9.83 | 5.46 | ||||||||
6 | 20.85 | 2.03 | 7.18 | 1.03 | 1.11 | 6.03 | 6.56 | 3.46 | 5.01 | 46.7 | |||
7 | 29.42 | 8.6 | 24.96 | 0.78 | 2.15 | 11.16 | 12.71 | 7.78 | 2.45 | ||||
8 | 24.45 | 3.47 | 25.24 | 0.86 | 18.2 | 18.15 | 2.19 | 7.44 | |||||
9 | 48.79 | 51.21 | |||||||||||
10 | 14.14 | 1.09 | 23.22 | 3.56 | 5.47 | 32.27 | 14.55 | 5.7 | |||||
11 | 44.09 | 55.91 | |||||||||||
12 | 60.67 | 20.78 | 10.03 | 8.52 | |||||||||
13 | 42.75 | 32.08 | 25.17 |
Compositions, wt-% | Physical Performance | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
SiO2 | CaO | MgO | Fe2O3 | Al2O3 | MnO | Na2O | F | C | H2O | Melting Point, °C | Viscosity, Pa·S | |
Supplier A | 28.8 | 25.0 | 1.6 | 2.6 | 10.3 | 0.2 | 3.3 | 5.3 | 21.5 | 0.1 | 1189 | 0.79 |
Supplier B | 28.6 | 24.1 | 3.6 | 0.9 | 6.3 | - | 6.5 | 1.4 | 19.1 | 0.4 | 1166 | 0.69 |
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Zhao, S.; Ge, Y.; Ma, L.; Yan, T.; Lyu, J.; Li, Z. Formation Analysis of Edge Cracks of 33MnCrTiB Fork Steel. Metals 2018, 8, 587. https://doi.org/10.3390/met8080587
Zhao S, Ge Y, Ma L, Yan T, Lyu J, Li Z. Formation Analysis of Edge Cracks of 33MnCrTiB Fork Steel. Metals. 2018; 8(8):587. https://doi.org/10.3390/met8080587
Chicago/Turabian StyleZhao, Shuo, Yangyang Ge, Liang Ma, Tao Yan, Jingcai Lyu, and Zushu Li. 2018. "Formation Analysis of Edge Cracks of 33MnCrTiB Fork Steel" Metals 8, no. 8: 587. https://doi.org/10.3390/met8080587