scholarly journals Characteristics and Transformation Mechanism of Nonmetallic Inclusions in 304 Stainless Steel during Heat Treatment at 1250 °C

Materials ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 5396
Author(s):  
Wen-Sheng Yang ◽  
Shuai Liu ◽  
Shao-Wei Han ◽  
Jia-Wei Wang ◽  
Jing Guo ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Stainless Steel ◽  
Nonmetallic Inclusions ◽  
Ostwald Ripening ◽  
Treatment Time ◽  
304 Stainless Steel ◽  
Isothermal Heat Treatment ◽  
Transformation Mechanism ◽  
Cr2o3 Content ◽  
Average Size

Evolutions of two typical types of nonmetallic inclusions, i.e., inclusions based on CaO-SiO2-Al2O3 and MnO-SiO2-Al2O3 of 304 stainless steel were investigated in laboratory-scale experiments under isothermal heat treatment at 1250 °C for 0, 30, 60 and 120 min. Results show inclusion population density increases at the first stage and then decreases while their average size decreases and then increases. Moreover, almost no Cr2O3 content within the inclusion before the heat treatment, but Cr2O3 content increases gradually along with increasing heat treatment time. Furthermore, the increasing of Cr2O3 content in the inclusions would increase their melting points and reduce their plasticities. The experimental results and thermodynamic analysis indicate that there are three steps for inclusion evolution during the heat treatment process, in which Ostwald ripening plays an important role in inclusion evolution, i.e., inclusions grow by absorbing the newly formed small-size MnO-Cr2O3 inclusions.

Microstructure Evolution in Isothermal Heat Treatment of 0Cr32Ni7Mo4NDuplex Stainless Steel

2014 ◽  
Vol 789 ◽  
pp. 314-319
Author(s):  
Yu Lai Chen ◽  
Hong He ◽  
Fei Fang
Keyword(s):  
Heat Treatment ◽  
Stainless Steel ◽  
Microstructure Evolution ◽  
Volume Fraction ◽  
Decomposition Reaction ◽  
Optical Microscope ◽  
Isothermal Heat Treatment ◽  
Σ Phase ◽  
Temperature Range ◽  
Δ Phase

The microstructure evolution of as-cast 0Cr32Ni7Mo4N hyper duplex stainless steel during the isothermal heat treatment in the temperature range of 800°C-1300°Cwas studied in the present investigation. The morphologies and precipitates were observed and determined by using optical microscope (OM), scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). The results show that eutectoid decomposition reaction (δ→σ+γ2) take place in ferrite (δ) phase during isothermal heat treatment in the temperature range of 800°C-1000°C. Sigma (σ) phase and secondary austenite (γ2) phase coexist as cellular structure. Lamellar Cr2N precipitates in δ phase mostly when isothermal heat treatment at 800°Cand 850°C, while it only appears in γ phase between 900°C and 1050°C. As the annealing temperature rising, the quantity of σ phase, Cr2N and γ2 phase decreases. The volume fraction ratio of ferrite and austenite is stable between 1100°C and 1300°C, and γ → δ transformation is hard to occur.

Effects of Heat Treatment on Mechanical Property and Microstructure of Aluminum/Stainless Steel Bimetal Plate

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
Weng-Sing Hwang ◽  
Tian-I Wu ◽  
Wen-Chung Sung
Keyword(s):  
Heat Treatment ◽  
Mechanical Property ◽  
Stainless Steel ◽  
Bonding Strength ◽  
Annealing Process ◽  
304 Stainless Steel ◽  
Roll Bonding ◽  
Intermediate Layers ◽  
Clad Metals ◽  
1050 Aluminum Alloy

The effects of postrolling heat treatment on the mechanical property and microstructure of 1050 aluminum alloy and 304 stainless steel (SS) clad metals were investigated. Clad metals were made by cold rolling after surface treatments of both sheets followed by heat treatment at 500 °C for various annealing times. The effects of transformation of microstructure at the interface on bonding strength are discussed. The initial clad roll bonding of Al/stainless steel clad metal was bonded by mechanical locking at the interface. The protruding stainless steel in the interface is the diffusion route and forms the better joint with aluminum in the annealing process, which results in the enhancement of the bonding strength. Intermediate layers were formed for over 2 h. It resulted in the weakening of the bonding strength and the fracture surface transforms into a brittle structure. As Al/stainless steel clad metals were under 13% reduction ratio, it had the optimum bond strength with a heat treatment for 1 h at 500 °C.

scholarly journals Evolution of non-metallic inclusions during heat treatment

2020 ◽  
Vol 117 (4) ◽  
pp. 408
Author(s):  
Chengsong Liu ◽  
Bryan Webler
Keyword(s):  
Heat Treatment ◽  
Size Distribution ◽  
Inclusion Size ◽  
Isothermal Heat Treatment ◽  
Number Density ◽  
Inclusion Composition ◽  
Steel Microstructure ◽  
Metallic Inclusions ◽  
Higher Temperature ◽  
Average Size

Isothermal heat treatment can not only modify steel microstructure, but also non-metallic inclusions. In this work, heat treatment experiments were conducted between 1373 and 1573 K (1100 and 1300 °C) to study the evolution of inclusion composition, morphology, and size distribution. Results showed that during the heat treatment at 1473 and 1573 K (1200 and 1300 °C), two main kinds of inclusions initially in the steel, CaS and MgO–Al2O3–CaO–CaS, gradually transformed to (Ca, Mn)S and MgO–Al2O3–(Ca, Mn)S inclusions, and some MgO–Al2O3–CaO inclusions also transformed to MgO–Al2O3–(Ca, Mn)S. At the lowest temperature studied, 1373 K (1100 °C), little change was observed. No significant changes in number density and area fraction of the measured inclusions were observed, while the average size of inclusions increased after the heat treatment. The extent of transformation of CaS, MgO–Al2O3–CaO–CaS and MgO–Al2O3–CaO inclusions increased with decreasing inclusion size and higher temperature.

scholarly journals The Influence of Holding Time on the Microstructure Evolution of Mg–10Zn–6.8Gd–4Y Alloy during Semi-Solid Isothermal Heat Treatment

Metals ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 420 ◽  
Author(s):  
Shuang Nie ◽  
Bingyang Gao ◽  
Xuejian Wang ◽  
Zhiqiang Cao ◽  
Enyu Guo ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Grain Boundaries ◽  
Microstructure Evolution ◽  
Treatment Process ◽  
Ostwald Ripening ◽  
Eutectic Structure ◽  
Holding Time ◽  
Isothermal Heat Treatment ◽  
Heat Treatment Process ◽  
Semi Solid

A semi-solid microstructure of Mg–10Zn–6.8Gd–4Y alloys is acquired via an isothermal heat treatment process, and the effects of the holding time on the microstructure evolution of Mg–10Zn–6.8Gd–4Y alloys are investigated. The results show that the microstructure of the cast alloy is composed of primary α-Mg dendritic grains with a eutectic structure (W-phase and eutectic Mg) distributed at the grain boundaries. The primary α-Mg dendritic grains grow in size with increasing holding time, and they tend to grow into more globular structures in the initial stage; they then become a bit more dendritic, as small branches grow from the grain boundaries after holding the sample at 580 °C for 10 min. Meanwhile, the interdiffusion of magnesium atoms within the eutectic region, and between the primary α-Mg and eutectic structure, leads to the formation of fine and relatively globular eutectic Mg grains in the eutectic structure after holding for 10 min. The eutectic Mg grains begin to grow, coarsen, coalesce, or be swallowed by the surrounding primary grains, causing fluctuations of the general grain size. Over the whole isothermal heat treatment process, two mechanisms—coalescence and Ostwald ripening—dominate the grain coarsening.

Effects of heat treatment on the microstructure and metallurgical properties of the explosively bonded 304 stainless steel—CK45 steel

2016 ◽  
Vol 27 (4) ◽  
pp. 488-506 ◽  
Author(s):  
Mohammadreza Khanzadeh Gharah Shiran ◽  
Seyyed Javad Mohammadi Baygi ◽  
Seyed Rahim Kiahoseyni ◽  
Hamid Bakhtiari ◽  
Mohsen Allah Dadi
Keyword(s):  
Heat Treatment ◽  
Stainless Steel ◽  
Steel Plates ◽  
Standoff Distance ◽  
304 Stainless Steel ◽  
Grain Sizes ◽  
Heat Treated ◽  
Vortex Nature ◽  
Impact Kinetic Energy ◽  
The Impact

In this research, the effects of heat treatment are studied on the microstructure and mechanical properties of the explosive bonding of 304 stainless steel plates and CK45 carbon steel with a constant explosive load and various standoff distances. The samples are heat treated in a furnace for 2-h and 4-h at 250℃ and 350℃. The results imply that by increasing the standoff distance from 4 to 5 mm, the impact kinetic energy increases and severe plastic deformation occurs in the bonding interface. The metallography results indicate the wave-vortex nature of the interface with the increase of standoff distance. In addition, heat treatment for 2 h at 350℃ leads to an increase in the thicknesses of intermetallic compounds in the interface. Also, the hardness decreases from 271 to 171 Vickers, and from 279 to 195 Vickers with 2 h of heat treatment at 350℃ in samples with standoff distances of 4 and 5 mm, respectively. Furthermore, the strengths of the samples decrease from 449 to 371 MPa, and from 510 to 433 MPa, respectively. Hardness and strength changes occur due to changes in the thickness of the intermetallic area and an increase in grain sizes.

Sign in / Sign up

Export Citation Format

Share Document