傾斜板法制備9Cr18半固態坯料二次重熔的微觀組織演變

王永金; 宋仁伯

doi:10.13374/j.issn2095-9389.2020.05.12.003

傾斜板法制備9Cr18半固態坯料二次重熔的微觀組織演變

doi: 10.13374/j.issn2095-9389.2020.05.12.003

王永金^,,
宋仁伯

北京科技大學材料科學與工程學院，北京 100083

基金項目: 中國博士后科學基金資助項目（2019M650482）；中央高校基本科研業務費資助項目（FRF-TP-18-039A1，FRF-IDRY-19-013）；北京市優秀人才培養資助青年骨干個人項目

詳細信息

通訊作者:
E-mail: wangyongjin@ustb.edu.cn

中圖分類號: TG142.1
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出版歷程
- 收稿日期: 2020-05-12
- 刊出日期: 2021-02-26

Microstructure evolution during remelting of 9Cr18 semisolid billet prepared by sloping plate method

WANG Yong-jin^,,
SONG Ren-bo

School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China

More Information

Corresponding author: E-mail: wangyongjin@ustb.edu.cn

摘要

摘要: 研究利用傾斜板法制備的9Cr18半固態坯料在二次重熔過程中微觀組織演變，以期對后續觸變成形提供必要的理論基礎。研究結果表明，采用傾斜板澆注法可以得到優質的9Cr18半固態坯料，其典型組織為初生固相奧氏體（γ₁）球狀晶粒和晶界網狀組織構成，網狀組織為二次奧氏體（γ₂）和M₇C₃碳化物液相共晶組織。球狀晶粒的平均直徑為93.5 μm，形狀因子0.69，半固態坯料球狀晶粒邊界光滑，大小相對均勻。固液兩相中Fe、C、Cr存在著明顯的元素差異。液相組織中Cr、C元素富集，固相中Fe含量較高。采用波浪形傾斜板法制備的9Cr18合金半固態坯料重熔組織形貌優于傳統鑄錠重熔組織。半固態坯料重熔后的組織化學成分更為均勻，晶粒也更圓整，固液界面平滑，且加熱溫度越高，晶粒越圓整，液相率越高。二次重熔后碳化物尺寸明顯減小，平均寬度僅為0.5 μm，長度大大減小使得其形態接近粒狀。
- 傾斜板法 /
- 9Cr18不銹鋼 /
- 半固態坯料 /
- 二次重熔 /
- 組織演變
Abstract: Semisolid processing is a new near-net-shape manufacturing process suitable for fabricating components with complex shapes. Semisolid billet remelting is a key process performed prior to the subsequent semisolid thixoforming. Understanding the remelting behavior will provide significant theoretical guidance for the semisolid thixoforming process. In this study, during remelting, we investigated the microstructural evolution of a 9Cr18 semisolid billet prepared by the sloping plate method. The microstructures of 9Cr18 specimens for a semisolid billet and traditional casting ingot were discussed. The effects of the initial microstructure and remelting temperature on the remelting behavior were also clarified. The microstructural evolution and remelting behavior were observed via optical microscopy, scanning electron microscopy, X-ray diffraction, and differential scanning calorimetry. The results show that an excellent 9Cr18 semisolid billet can be obtained via the sloping plate method. Forced convection through the sloping plate was found to play a key role in breaking the continuous distribution of dendrites. The typical microstructure was found to exhibit a primary solid austenite globular grain (γ₁) and a eutectic structure of secondary austenite (γ₂) and M₇C₃ carbide. The average size of a globular grain was determined to be 93.5 μm and the shape factor was 0.69. The globular grains showed a smooth boundaries. The Fe, C, and Cr elements showed obviously different contents in the solid and liquid phases. The Cr and C elements were enriched in the liquid phase, whereas the Fe content was higher in the solid phase. Compared with the traditional casting ingot, the remelting microstructure of the 9Cr18 semisolid billet prepared by the sloping plate method was more suitable for subsequent semisolid thixoforming. A more even distribution of the chemical composition and more globular grains can be obtained after semisolid remelting. The solid/liquid interface was smooth on the remelted specimen. The width of the M₇C₃ carbide decreased to 0.5 μm after remelting and the morphology became nearly granular. The observed microstructural evolution during remelting of the 9Cr18 semisolid billet contributes to our understanding of the thixotropic behavior in the subsequent semisolid forming process.
- sloping plate method /
- 9Cr18 stainless steel /
- semisolid billet /
- remelting /
- microstructure evolution

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圖 1 波浪形傾斜板制坯裝置示意圖

Figure 1. Schematic of wave-shaped sloping plate device

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圖 2 9Cr18半固態重熔工藝曲線

Figure 2. Temperature–time curve of 9Cr18 semisolid remelting process

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圖 3 9Cr18不同狀態顯微組織。（a）傳統鑄造枝晶組織；（b）半固態球狀晶組織

Figure 3. Microstructures of 9Cr18 specimens: (a) traditional casting ingot; (b) semisolid billet

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圖 4 9Cr18半固態坯料X射線衍射圖譜

Figure 4. XRD results of 9Cr18 semisolid billet

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圖 5 半固態球狀晶組織掃描形貌及電子能譜線掃描分析

Figure 5. SEM image of the globular grains in semisolid billet and EDS analysis

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圖 6 9Cr18半固態組織掃描電鏡及能譜分析。（a）重熔前;（b）重熔后

Figure 6. SEM images and EDS analysis of 9Cr18 semisolid billet: (a) before remelted; (b) remelted

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圖 7 9Cr18半固態坯料重熔顯微組織

Figure 7. Microstructure of remelted billet

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圖 8 9Cr18坯料二次重熔顯微組織。（a～c）傳統鑄造坯料;（d～f）半固態坯料

Figure 8. Microstructures of semisolid remelted specimens: (a–c) traditional casting ingot; (d–f) semisolid billet

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圖 9 9Cr18半固態坯料差熱曲線與固相率計算結果

Figure 9. DSC curve and solid fraction results of 9Cr18 semisolid billet

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圖 10 9Cr18半固態坯料重熔至不同溫度顯微組織。（a）1280 ℃；（b）1300 ℃；（c）1320 ℃

Figure 10. SEM micrographs of 9Cr18 steel remelted to different temperatures: (a) 1280 ℃; (b) 1300 ℃; (c) 1320 ℃

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表 1 9Cr18不銹鋼的化學成分（質量分數）

Table 1. Chemical composition of 9Cr18 steel %

C Cr Si Mn P S Al Ni Fe

0.97 17.33 0.52 0.35 0.02 0.005 0.10 0.16 Bal.

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259luxu-164

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