Modification of Non-Metallic Inclusions in Stainless Steel by Addition of CaSi
Abstract
:1. Introduction
2. Materials and Methods
2.1. Materials
2.2. Electrolytic Extraction and Investigation of Inclusions
3. Results and Discussions
3.1. Characterization of Inclusions after Extraction in Different Electrolytes
3.2. Classification of Non-Metallic Inclusions in 316R and 316Ca Steels
3.3. Particle Size Distribution of the Inclusions Observed in 316R and 316Ca Steels
3.4. Mechanism of Inclusion Transformation
4. Conclusions
- Similar compositions of oxide inclusions in 316Ca steel were obtained after EE by using 2% TEA and 10% AA electrolytes.
- The 316L steels contained four types of inclusions: (1) elongated MnS (Type I), (2) MnS sulfides with hard oxide cores (Type II), (3) undeformed irregular oxides (Type III), and (4) elongated oxides with a hard oxide core (Type IV).
- In the reference sample, the oxide composition was mainly Al2O3–MgO–MnO. However, after Ca treatment of 316L steel, about 46% of the observed inclusions were oxide inclusions (Types III and IV), which correlated to gehlenite and to a mixture of gehlenite and anorthite, which are favorable for the machinability of steel.
Author Contributions
Funding
Acknowledgments
Conflicts of Interest
References
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Steel Grade | Ca-treated | C | Si | Mn | Cr | Ni | S a | O a | Ca a | Al a |
---|---|---|---|---|---|---|---|---|---|---|
(mass %) | ||||||||||
316R | No | 0.02 | 0.38 | 1.60 | 16.82 | 11.18 | 70 | 20 | - | 40 |
316Ca | Yes | 0.01 | 0.46 | 1.58 | 16.86 | 11.14 | 90 | 59 | 28 | 40 |
Steel Grade | Sample | Observed Area, Aobs (mm2) | Dissolved Metal, Wdis (g) | Dissolved Depth (µm) | Number of Observed NMIs, n | Size Range (µm) |
---|---|---|---|---|---|---|
316R | R | 0.898 | 0.1563 | ≈188 | 435 | 2–98 |
316Ca | A | 0.898 | 0.0935 | ≈85 | 180 | 3–124 |
Typical SEM Images | 316R | 316Ca | ||||
---|---|---|---|---|---|---|
L (µm) | AR | Composition | L (µm) | AR | Composition | |
5–98 | 7–30 | MnS > 90% | 14–124 | 7–25 | MnS 90–100% and (Al, Ca)O < 10% | |
2–36 | 1–8 | MnS 30–90% and (Al, Mg, Mn)O 10–70% | 3–33 | 1–7 | MnS 30–90% and (Al, Ca, Si)O 10–70% | |
2–10 | 1–3 | Al2O3 48–75% MgO 2–24% MnO 9–29% TiOx 1–21% | 3–15 | 1–3 | CaO 33–41% Al2O3 24–31% SiO2 30–33% MgO 2–4% TiOx <1% | |
none | - | - | 4–28 | 2–14 | Oxide (CaO 26–39% Al2O3 16–30% SiO2 28–39% MgO 0–5% TiOx 0–14%) and MnS |
Samples | Inclusion Type | L (μm) | W (μm) | De (μm) | AR | fv × 104 | Nv (mm−3) | Frequency (%) |
---|---|---|---|---|---|---|---|---|
316R | Type I | 33.2 ± 24.8 (5–98) | 2.6 ± 1.4 (1–7) | 6.0 ± 3.5 (1–16) | 7–30 | 6.7 | 2667 | 9.2 |
Type II | 5.0 ± 3.8 (2–36) | 1.8 ± 0.7 (1–7) | 2.4 ± 1.1 (1–10) | 1–8 | 3.7 | 24,933 | 86.4 | |
Type III | 5.4 ± 2.2 (2–10) | 3.6 ± 1.5 (2–8) | 4.0 ± 1.6 (2–9) | 1–3 | 0.7 | 1267 | 4.4 | |
Type IV | - | - | - | - | - | - | ||
316Ca | Type I | 43.0 ± 32.4 (14–124) | 3.7 ± 1.1 (2–5) | 8.1 ± 3.2 (4–14) | 7–25 | 4.1 | 1003 | 5.0 |
Type II | 7.0 ± 4.8 (3–33) | 2.6 ± 0.8 (1–5) | 3.6 ± 1.3 (2–10) | 1–7 | 3.5 | 9811 | 48.9 | |
Type III | 6.2 ± 3.0 (3–15) | 3.3 ± 0.9 (2–6) | 4.1 ± 1.3 (2–8) | 1–3 | 2.1 | 4460 | 22.2 | |
Type IV | 10.7 ± 5.2 (4–28) | 2.3 ± 0.6 (1–4) | 3.8 ± 1.1 (2–7) | 2–14 | 1.7 | 4794 | 23.9 |
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Du, H.; Karasev, A.; Sundqvist, O.; Jönsson, P.G. Modification of Non-Metallic Inclusions in Stainless Steel by Addition of CaSi. Metals 2019, 9, 74. https://doi.org/10.3390/met9010074
Du H, Karasev A, Sundqvist O, Jönsson PG. Modification of Non-Metallic Inclusions in Stainless Steel by Addition of CaSi. Metals. 2019; 9(1):74. https://doi.org/10.3390/met9010074
Chicago/Turabian StyleDu, Hongying, Andrey Karasev, Olle Sundqvist, and Pär G. Jönsson. 2019. "Modification of Non-Metallic Inclusions in Stainless Steel by Addition of CaSi" Metals 9, no. 1: 74. https://doi.org/10.3390/met9010074