Effects of Nb on Elevated-Temperature Properties of Fire-Resistant Steel
Objective: Two kinds of fire-resistant steel with different Nb content (Nb-free and 0.03 wt.%) were prepared for studying the effects of Nb addition on the elevated-temperature strength of fire-resistant steel. Methods: Two stages of heat treatment were carried out on the steels to obtain different...
| Main Authors: | , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2022-12-01
|
| Series: | Crystals |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2073-4352/12/12/1842 |
| _version_ | 1797460740217503744 |
|---|---|
| author | Yadong Li Rongchun Wan Xing Wang Hui Zhao Xun Gong |
| author_facet | Yadong Li Rongchun Wan Xing Wang Hui Zhao Xun Gong |
| author_sort | Yadong Li |
| collection | DOAJ |
| description | Objective: Two kinds of fire-resistant steel with different Nb content (Nb-free and 0.03 wt.%) were prepared for studying the effects of Nb addition on the elevated-temperature strength of fire-resistant steel. Methods: Two stages of heat treatment were carried out on the steels to obtain different microstructures. Typical microstructures, dislocation, and precipitates morphology of steels were observed by SEM and TEM. The dislocation density was calculated by the X-ray data from the microstructures. High temperature and room temperature mechanical properties of steels were determined by tensile testing. Results: The results showed that the YS of N2-HR steel (addition of 0.03 wt.% Nb) at RT and 600 °C was higher than N1-HR steel (Nb-free) by about 81 and 30 MPa, respectively. This indicates that Nb is an alloying element as effective as Mo in increasing the elevated-temperature strength of fire-resistant steel. The dominant strengthening mechanisms of Nb addition on elevated-temperature yield strength are precipitation strengthening and bainite strengthening. Conclusions: Theoretical analysis shows that there are two precipitation strengthening stages in fire-resistant steel: (1) increasing dislocation density during hot rolling, and (2) blocking dislocation movement and recovery in tensile testing. The results also show that the effect of fine grain strengthening is not obvious at high temperature, but is obvious at room temperature. |
| first_indexed | 2024-03-09T17:09:21Z |
| format | Article |
| id | doaj.art-6db1b0165db14997b74349cf7980c72d |
| institution | Directory Open Access Journal |
| issn | 2073-4352 |
| language | English |
| last_indexed | 2024-03-09T17:09:21Z |
| publishDate | 2022-12-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Crystals |
| spelling | doaj.art-6db1b0165db14997b74349cf7980c72d2023-11-24T14:11:55ZengMDPI AGCrystals2073-43522022-12-011212184210.3390/cryst12121842Effects of Nb on Elevated-Temperature Properties of Fire-Resistant SteelYadong Li0Rongchun Wan1Xing Wang2Hui Zhao3Xun Gong4School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024, ChinaMaterials Engineering Department, Bohai Shipbuilding Vocational College, Huludao 125100, ChinaXi’an University of Architecture and Technology, Xi’an 710064, ChinaSchool of Materials Science and Engineering, Shenyang Ligong University, Shenyang 110180, ChinaSchool of Materials Science and Engineering, Shenyang Ligong University, Shenyang 110180, ChinaObjective: Two kinds of fire-resistant steel with different Nb content (Nb-free and 0.03 wt.%) were prepared for studying the effects of Nb addition on the elevated-temperature strength of fire-resistant steel. Methods: Two stages of heat treatment were carried out on the steels to obtain different microstructures. Typical microstructures, dislocation, and precipitates morphology of steels were observed by SEM and TEM. The dislocation density was calculated by the X-ray data from the microstructures. High temperature and room temperature mechanical properties of steels were determined by tensile testing. Results: The results showed that the YS of N2-HR steel (addition of 0.03 wt.% Nb) at RT and 600 °C was higher than N1-HR steel (Nb-free) by about 81 and 30 MPa, respectively. This indicates that Nb is an alloying element as effective as Mo in increasing the elevated-temperature strength of fire-resistant steel. The dominant strengthening mechanisms of Nb addition on elevated-temperature yield strength are precipitation strengthening and bainite strengthening. Conclusions: Theoretical analysis shows that there are two precipitation strengthening stages in fire-resistant steel: (1) increasing dislocation density during hot rolling, and (2) blocking dislocation movement and recovery in tensile testing. The results also show that the effect of fine grain strengthening is not obvious at high temperature, but is obvious at room temperature.https://www.mdpi.com/2073-4352/12/12/1842Nbfire-resistant steelprecipitation strengtheningbainite strengtheninghigh temperature strength |
| spellingShingle | Yadong Li Rongchun Wan Xing Wang Hui Zhao Xun Gong Effects of Nb on Elevated-Temperature Properties of Fire-Resistant Steel Crystals Nb fire-resistant steel precipitation strengthening bainite strengthening high temperature strength |
| title | Effects of Nb on Elevated-Temperature Properties of Fire-Resistant Steel |
| title_full | Effects of Nb on Elevated-Temperature Properties of Fire-Resistant Steel |
| title_fullStr | Effects of Nb on Elevated-Temperature Properties of Fire-Resistant Steel |
| title_full_unstemmed | Effects of Nb on Elevated-Temperature Properties of Fire-Resistant Steel |
| title_short | Effects of Nb on Elevated-Temperature Properties of Fire-Resistant Steel |
| title_sort | effects of nb on elevated temperature properties of fire resistant steel |
| topic | Nb fire-resistant steel precipitation strengthening bainite strengthening high temperature strength |
| url | https://www.mdpi.com/2073-4352/12/12/1842 |
| work_keys_str_mv | AT yadongli effectsofnbonelevatedtemperaturepropertiesoffireresistantsteel AT rongchunwan effectsofnbonelevatedtemperaturepropertiesoffireresistantsteel AT xingwang effectsofnbonelevatedtemperaturepropertiesoffireresistantsteel AT huizhao effectsofnbonelevatedtemperaturepropertiesoffireresistantsteel AT xungong effectsofnbonelevatedtemperaturepropertiesoffireresistantsteel |