The 10Ni5CrMoV steel examined was a 16 mm thick plate. Specimens measuring 12 mm×12 mm×120 mm were thermally cycled using DM-100A weld simulator with various parameters. The main results are summarized as fo...The 10Ni5CrMoV steel examined was a 16 mm thick plate. Specimens measuring 12 mm×12 mm×120 mm were thermally cycled using DM-100A weld simulator with various parameters. The main results are summarized as follaws. In the coarse-grained austenitized region（ Tm = 1 300℃ ＋ 1300℃ ） ,the microstructure is in good toughness. At the condition of Tm = 1 300℃ ＋ 850℃ and t8/5=43 s, the toughness decreases heavily because M-A constituent and twin martensite appear at the prior aastenite grain boundaries. When Tm= 1300℃ ＋ 850℃ or 1300℃ ＋ 730℃ and t8/5 = 85 s, local brittle zone is formed because of relatively coarse granular bainite.展开更多
The microstructure, composition and shape of precipitated phase under as-cast and finished product state of 5Cr21Mn9Ni4N steel with different rare earth （RE） amount were studied. Mechanical properties of 5Cr21Mn9Ni4...The microstructure, composition and shape of precipitated phase under as-cast and finished product state of 5Cr21Mn9Ni4N steel with different rare earth （RE） amount were studied. Mechanical properties of 5Cr21Mn9Ni4N steels withont RE addition and with RE added by 0. 2% in mass percent were tested respectively. The results indicate that the solid solution amount of RE is about 10^-6 -10^-5 order of magnitude in 5Cr21Mn9Ni4N steel. Dendrite of as-cast condition is refined obviously and dimension of interstitial phase is shortened when RE is added by 0.10%-0.20%. But the microstructure will be coarser if surplus RE is added. Precipitated phase under finished product state distributes evenly in nearly same size with RE added by 0. 2% which leads to a largely improved high temperature mechanical property.展开更多
The oxidation resistance of 5Cr21Mn9Ni4N steel micro-alloying by RE at 700 - 900 ℃ was investigated. The results indicate that oxidation exponent n and oxidation activation energy are increased, and oxidation velocit...The oxidation resistance of 5Cr21Mn9Ni4N steel micro-alloying by RE at 700 - 900 ℃ was investigated. The results indicate that oxidation exponent n and oxidation activation energy are increased, and oxidation velocity constant kp is decreased when 0.2% RE is added in 5Cr21Mn9Ni4N steel. The addition of RE elements does not alter phase constitution of oxidation scale, however it improves the configuration of oxidation scale, and increases thermal stability and adhesivity of oxidation scale, which results in the raise of oxidation resistance of 5Cr21Mn9Ni4N steel at high temperature. The oxidation scale constitutes of refractory steel transfer from manganic oxide mostly to ferric oxide mostly with the increase of temperature, which leads to descend of compactness and desquamation resistance of oxidation scale. The mass increase of ferric oxide in the oxidation scale and the looseness of oxidation scale are the main reason to descend the oxidation resistance of refractory steel.展开更多
The microstructure, morphology of precipitates and retained austenite and the volume fraction of retained austenite in 0Crl6Ni5Mo stainless steel during the tempering process were analyzed using optical microscope （O...The microstructure, morphology of precipitates and retained austenite and the volume fraction of retained austenite in 0Crl6Ni5Mo stainless steel during the tempering process were analyzed using optical microscope （OM）, transmission electron microscope （TEM）, X-ray diffraction （XRD） and scanning transmission electron microscope （STEM）. The results show that the microstructure of the tempered steel is mainly composed of tempered martensite, retained austenite, and delta ferrite. In the case of samples tempered from 500 to 700℃, the precipitates are mainly M23C6, which precipitate along the lath martensite boundaries. The precipitate content increases with the tempering temperature. During the tempering process, the content of retained austenite initially increases and then decreases, the maximum content of retained austenite being 29 vol.% upon tempering at 600℃. TEM analysis of the tested steel reveals two morphology types of retained austenite. One is thin film-like retained austenite that exists along the martensite lath boundary. The other is blocky austenite located on packet at the boundary and the original austenite grain boundary. To further understand the stability of reversed austenite, the Ni content in reversed austenite was measured using STEM. Results show a significant difference in nickel concentrations between reversed austenite and martensite.展开更多
Based on the fact that toughness degradation occurred in 1Cr21Ni5Ti duplex stainless steel during slow cooling in a temperature interval of 400-600 ℃ following brazed welding, a simulated embrittlement treatment was ...Based on the fact that toughness degradation occurred in 1Cr21Ni5Ti duplex stainless steel during slow cooling in a temperature interval of 400-600 ℃ following brazed welding, a simulated embrittlement treatment was utilized to evaluate its emhrittlement tendency. Accumulated experiences have shown that high Ti and A1 contents led frequently to severe toughness deterioration. To elucidate this phenomenon, four heats with various Ti and Al contents were prepared in laboratory-scale melts, which were used to investigate the inherent embrittlement nature. The results have shown that 550 ℃ aging led only to a modest toughness reduction, whereas, aging around 475 ℃ resulted in ferrite embrittlement, regardless of Ti, A1 levels. However, high Ti, A1 levels reduced the austenite phase, which, in the case of its inferior shape and distribution due to insufficient hot deformation, failed to resist cleavagetype cracks initiated in the ferrite phase. Increasing hot-forged areas reduction could modify the shape and distribution of austenite, resulting in the enhanced resistance of the austenite to the cleavage-type cracks, which have been confirmed to be beneficial for brittlement suppression of 1Cr21Ni5Ti duplex stainless steel.展开更多
High strength bolt steel 0Crl6Ni5Mo was charged with hydrogen by means of electrochemical technique to evaluate the hydrogen diffusion behavior. The bolt steels were investigated by a combination of electrochemical hy...High strength bolt steel 0Crl6Ni5Mo was charged with hydrogen by means of electrochemical technique to evaluate the hydrogen diffusion behavior. The bolt steels were investigated by a combination of electrochemical hydrogen permeation, thermal desorption spectroscopy （TDS）, slow strain rate test （SSRT） and microstructure observation. The hydrogen concentration of both 10.9 grade （Rm=950-1 150 MPa） and 12.9 grade （Rm=1 150-1 250 MPa） bolt steels increases with increasing the hydrogen charging current densities and charging time. The 12.9 grade bolt steel has higher apparent diffusion coefficient than 10.9 grade steel, corresponding to the value of 4.7×10 7 mm^2/s. By means of TDS tests, the activation energies of the two experimental steels are 17.74 kJ/mol and 18.92 kJ/mol, respectively. The hydrogen traps of both grade bolt steels are dislocations and crystal lattice. The notch tensile strength of the steels is reduced with the hydrogen concentration carried out by SSRT. The fracture morphologies of the steels after hydrogen charging present ductile dimple and quasi-cleavage characteristic.展开更多
文摘The 10Ni5CrMoV steel examined was a 16 mm thick plate. Specimens measuring 12 mm×12 mm×120 mm were thermally cycled using DM-100A weld simulator with various parameters. The main results are summarized as follaws. In the coarse-grained austenitized region（ Tm = 1 300℃ ＋ 1300℃ ） ,the microstructure is in good toughness. At the condition of Tm = 1 300℃ ＋ 850℃ and t8/5=43 s, the toughness decreases heavily because M-A constituent and twin martensite appear at the prior aastenite grain boundaries. When Tm= 1300℃ ＋ 850℃ or 1300℃ ＋ 730℃ and t8/5 = 85 s, local brittle zone is formed because of relatively coarse granular bainite.
文摘The microstructure, composition and shape of precipitated phase under as-cast and finished product state of 5Cr21Mn9Ni4N steel with different rare earth （RE） amount were studied. Mechanical properties of 5Cr21Mn9Ni4N steels withont RE addition and with RE added by 0. 2% in mass percent were tested respectively. The results indicate that the solid solution amount of RE is about 10^-6 -10^-5 order of magnitude in 5Cr21Mn9Ni4N steel. Dendrite of as-cast condition is refined obviously and dimension of interstitial phase is shortened when RE is added by 0.10%-0.20%. But the microstructure will be coarser if surplus RE is added. Precipitated phase under finished product state distributes evenly in nearly same size with RE added by 0. 2% which leads to a largely improved high temperature mechanical property.
文摘The oxidation resistance of 5Cr21Mn9Ni4N steel micro-alloying by RE at 700 - 900 ℃ was investigated. The results indicate that oxidation exponent n and oxidation activation energy are increased, and oxidation velocity constant kp is decreased when 0.2% RE is added in 5Cr21Mn9Ni4N steel. The addition of RE elements does not alter phase constitution of oxidation scale, however it improves the configuration of oxidation scale, and increases thermal stability and adhesivity of oxidation scale, which results in the raise of oxidation resistance of 5Cr21Mn9Ni4N steel at high temperature. The oxidation scale constitutes of refractory steel transfer from manganic oxide mostly to ferric oxide mostly with the increase of temperature, which leads to descend of compactness and desquamation resistance of oxidation scale. The mass increase of ferric oxide in the oxidation scale and the looseness of oxidation scale are the main reason to descend the oxidation resistance of refractory steel.
文摘The microstructure, morphology of precipitates and retained austenite and the volume fraction of retained austenite in 0Crl6Ni5Mo stainless steel during the tempering process were analyzed using optical microscope （OM）, transmission electron microscope （TEM）, X-ray diffraction （XRD） and scanning transmission electron microscope （STEM）. The results show that the microstructure of the tempered steel is mainly composed of tempered martensite, retained austenite, and delta ferrite. In the case of samples tempered from 500 to 700℃, the precipitates are mainly M23C6, which precipitate along the lath martensite boundaries. The precipitate content increases with the tempering temperature. During the tempering process, the content of retained austenite initially increases and then decreases, the maximum content of retained austenite being 29 vol.% upon tempering at 600℃. TEM analysis of the tested steel reveals two morphology types of retained austenite. One is thin film-like retained austenite that exists along the martensite lath boundary. The other is blocky austenite located on packet at the boundary and the original austenite grain boundary. To further understand the stability of reversed austenite, the Ni content in reversed austenite was measured using STEM. Results show a significant difference in nickel concentrations between reversed austenite and martensite.
文摘Based on the fact that toughness degradation occurred in 1Cr21Ni5Ti duplex stainless steel during slow cooling in a temperature interval of 400-600 ℃ following brazed welding, a simulated embrittlement treatment was utilized to evaluate its emhrittlement tendency. Accumulated experiences have shown that high Ti and A1 contents led frequently to severe toughness deterioration. To elucidate this phenomenon, four heats with various Ti and Al contents were prepared in laboratory-scale melts, which were used to investigate the inherent embrittlement nature. The results have shown that 550 ℃ aging led only to a modest toughness reduction, whereas, aging around 475 ℃ resulted in ferrite embrittlement, regardless of Ti, A1 levels. However, high Ti, A1 levels reduced the austenite phase, which, in the case of its inferior shape and distribution due to insufficient hot deformation, failed to resist cleavagetype cracks initiated in the ferrite phase. Increasing hot-forged areas reduction could modify the shape and distribution of austenite, resulting in the enhanced resistance of the austenite to the cleavage-type cracks, which have been confirmed to be beneficial for brittlement suppression of 1Cr21Ni5Ti duplex stainless steel.
基金the funding of this work by Luoyang Sunrui Special Equipment Co.,Ltd.in Luoyang(China)
文摘High strength bolt steel 0Crl6Ni5Mo was charged with hydrogen by means of electrochemical technique to evaluate the hydrogen diffusion behavior. The bolt steels were investigated by a combination of electrochemical hydrogen permeation, thermal desorption spectroscopy （TDS）, slow strain rate test （SSRT） and microstructure observation. The hydrogen concentration of both 10.9 grade （Rm=950-1 150 MPa） and 12.9 grade （Rm=1 150-1 250 MPa） bolt steels increases with increasing the hydrogen charging current densities and charging time. The 12.9 grade bolt steel has higher apparent diffusion coefficient than 10.9 grade steel, corresponding to the value of 4.7×10 7 mm^2/s. By means of TDS tests, the activation energies of the two experimental steels are 17.74 kJ/mol and 18.92 kJ/mol, respectively. The hydrogen traps of both grade bolt steels are dislocations and crystal lattice. The notch tensile strength of the steels is reduced with the hydrogen concentration carried out by SSRT. The fracture morphologies of the steels after hydrogen charging present ductile dimple and quasi-cleavage characteristic.
