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Field emission-scanning electron microscopy(FE-SEM) technique was employed to observe the shape,size and distribution of AIN MnS inclusions in oriented electrical steels. Specimens used for FE-SEM observation were deeply electrolytic etched at room temperature in non-aqueous acetylacetone(AA) solution. The results indicate that the FE-SEM technique has obvious advantage in specimen preparation. Therefore, it can be easily used to identify the AIN MnS inclusions and even copper nano-particles in oriented electrical steels with the same analysis accuracy as that by TEM. This technique is a good substitute for TEM and the associated specimen preparation in the observation of inclusions in electrical steels. It will be a powerful technique for routine analysis in the production of grain oriented electrical steels. 相似文献
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This study has focused on the morphology and distribution of inclusions and precipitates modified by rare earth (RE) elements, which has a decisive influence on microstructure, corrosion properties and impact behaviors in Q355 low alloy steel. Characterized by the method of electrolytic extraction and ASPEX-scanning electron microscopy (ASPEX-SEM), small-sized spherical RE inclusions have been modified to replace elongated MnS and large-sized Al2O3. Q355RE steel after RE alloying has lower corrosion rate and higher value of α/γ, due to the formation of stable and dense rust layers. Q355RE steel also exhibits better resistance to fracture at low temperature, owing to the presence of RE modification to inclusions and its effects on reducing crack initiation and propagation. Nano-scale RE precipitates containing sulfur and phosphorus is observed along grain boundaries by transmission electron microscopy (TEM). The purification of grain boundaries by RE is beneficial to the improvement of corrosion and impact properties. 相似文献
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研究了CSP工艺下稀土冷轧板冷轧后退火过程中的第二相析出行为,模拟了某企业685 ℃×9 h退火工艺,利用光学显微镜和X射线衍射仪分析了退火前后的微观组织和宏观织构的变化;采用非水电解分离法从试验钢中提取第二相粒子,并利用X射线衍射分析了第二相析出物类型;再使用化学法对退火过程中第二相析出量的变化进行了定量分析,并结合析出动力学计算分析第二相析出规律。结果表明,经过该退火工艺后,晶粒从典型的纤维状冷轧组织演变为再结晶饼形晶粒,非{111}织构有所减弱,{111}织构有所增强;试验钢中的第二相类型主要为MnS、Fe3C和AlN,MnS在退火过程中几乎不析出,Fe3C主要在室温到570 ℃升温过程中析出,AlN随着退火温度的升高而不断析出,在685 ℃附近析出最快。 相似文献
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利用光学显微镜和能谱仪研究了42CrMo钢中分别添加S(0.09wt%)和S—RE元素后,钢中夹杂物的组成、形态和变形能力,并分析了硫化物夹杂对钢的力学性能的影响。结果表明,单独加S元素时,钢中主要存在MnS夹杂,MnS在高温具有强的塑性变形能力是导致锻件力学性能各向异性的重要原因;加入RE(0.076%)元素后,钢中出现的稀土硫化物具有较强的抗塑性变形能力,改善了钢的横向力学性能,其横纵向冲击韧度比值由单一加S元素的0.2提高到0.5,从而为钢的实际应用提供了理论依据。 相似文献
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本文研究了几种Cr-Ni-Mo钢的过热特征,提出把断口表面出现延性沿晶小平面作为过热的判据。在高的奥氏体化温度下,某种第二相粒子可以固溶,随后在冷却过程中沿高温奥氏体晶界重新析出,因而产生各种过热现象。MnS粒子的重新析出使普通硫含量的Cr-Ni-Mo钢发生沿晶延性破断,而AlN或VC粒子在高温奥氏体晶界的重新析出也能使低硫的Cr-Ni-Mo钢过热。稀土元素对几种Cr-Ni-Mo钢的过热都有抑制作用。当RE/S达到临界比值(约为4)时,不仅使MnS夹杂物完全转变成稀土硫化物和稀土硫氧化物,而且使高温奥氏体晶粒显著细化,改善韧性。如果RE/S比值远大于4,多余的稀土元素还可能与C,N原子发生交互作用。 相似文献
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利用GNT系万能试验机和Sigma 300场发射扫描电镜研究了稀土Y对TWIP钢(22Mn-1.5Al-0.6C)力学性能及夹杂物的影响。结果表明,添加稀土Y后,试验TWIP钢的强度和韧性均有提高,抗拉强度由725 MPa提高到752 MPa,屈服强度由290 MPa提高到312 MPa,冲击吸收能量由178.9 J提高到207.7 J,而硬度和断后伸长率则小幅降低。稀土Y细化了TWIP钢晶粒,且钢中MnS、Al2O3以及MnS+AlN复合夹杂改性成Y2S3、Y2S3+Y2O3、AlN+Y2S3夹杂。夹杂物分析结果显示,大部分夹杂物的数量和尺寸都有明显的减小,有利于试验钢综合力学性能的提高。 相似文献
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Bo Jiang Meng Wu He Sun Zhilin Wang Zhigang Zhao Yazheng Liu 《Metals and Materials International》2018,24(1):15-22
The austenite growth behavior of non-quenched and tempered steels (casted by continuous casting and molding casting processes) was studied. The austenite grain size of steel B casted by continuous casting process is smaller than that of steel A casted by molding casting process at the same heating parameters. The abnormal austenite growth temperature of the steels A and B are 950 °C and 1000 °C, respectively. Based on the results, the models for the austenite grain growth below and above the abnormal austenite growth temperature of the investigated steels were established. The dispersedly distributed fine particles MnS in steel B is the key factor refining the austenite grain by pinning the migration of austenite grain boundary. The elongated inclusions MnS are ineffective in preventing the austenite grain growth at high heating temperature. For the non-quenched and tempered steel, the continuous casting process should be adopted and the inclusion MnS should be elliptical, smaller in size and distributed uniformly in order to refine the final microstructure and also improve the mechanical properties. 相似文献
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High-strength low-alloy steels subjected to high heat input welding are susceptible to failure due to low toughness caused by grain coarsening. The effect of TiN on grain refinement in the simulated heat-affected zone (HAZ) was investigated. Because of small amount of Ti addition, abundant dispersed nanoscale TiN precipitates were formed. The TiN precipitates tended to be stable at high temperature and effectively retarded the austenite grain growth by refining the grain size during thermal cycle. Furthermore, the TiN also covered on the surface of Al–Ti complex oxide with MnS and caused low interface energy with ferrite. The acicular ferrite grains nucleated on complex inclusion in austenite grains at intermediate temperature and induced the austenite grain transform to the fine-grained mixed microstructure of acicular ferrite and bainite. The crystallographic grain size became small in the simulated HAZ due to the effective pinning effect and acicular ferrite formation. 相似文献
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《Acta Materialia》2007,55(19):6553-6560
After semi-solid treatment and rapid quenching, bearing steel 100Cr6 exhibits a martensitic structure with a large amount of retained austenite along the grain boundaries. The toughness values are significantly lower than after conventional hardening, even when the alloys are post-processed by an additional heat treatment step. Slow cooling from the freezing range results in a reduced amount of retained austenite and improved toughness properties. The low impact toughness values of the rapidly cooled conditions are associated with the appearance of intergranular fracture, while the slowly cooled condition fails in a transgranular manner. The structural development and the mechanical behaviour are explained by severe segregation of the main alloying elements during solidification, but also by sulphur enrichment in the remaining liquid phase. Chain-like precipitates of MnS are formed along the grain boundaries, similar to the well-known ‘burning’ phenomenon of low-alloyed steels. 相似文献
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采用金相显微镜、扫描电镜等对GOST-2钢-60℃低温冲击韧性不合格车轮进行检验分析,结果表明:其主要原因是磷含量高、MnS夹杂多、存在带状组织,且晶粒尺寸较大。在生产中通过加入铝钒元素细化晶粒,并采用低氧钢、低磷钢及超低硫钢冶炼工艺和钙处理等措施,消除了钢中的条状夹杂物,改善了车轮的低温冲击韧性,显著提高了产品的合格... 相似文献
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Yu Liu Xiangliang Wan Yong Wang Wan Zheng Yanhui Hou 《Science & Technology of Welding & Joining》2019,24(1):43-51
The particles and microstructure characteristics of coarse-grained heat-affected zone (CGHAZ) in Al–Ti–Mg killed steels with different Al contents were investigated. The results show that inclusion in high Al steel consists of Al–Mg oxide surrounded with a layer of MnS. However, inclusion in low Al steel is Al–Ti–Mg oxide covered with a layer of MnS, effectively promoting the formation of acicular ferrite. The precipitates of both steels are (Ti, Nb)N, the finer and more dispersed inclusions and precipitates in low Al steel can effectively inhibit austenite grain growth by grain boundary pinning during the thermal cycle. The fine-grained microstructure is obtained in CGHAZ of the low Al steel due to the pinning effect of finer particles and the high density of acicular ferrite. 相似文献
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The precipitation behavior of the MnS phase of MnO-SiO2 oxides in Si/Mn deoxidized steels was examined. MnS phase formation in the oxide phase was clearly identified, and the Mn
content in both phases increased with isothermal holding at 1,200°C. With increased cooling rate, both the size of inclusions
and the precipitation ratio of the MnS phase in the oxides decreased. More than 90% of MnO-SiO2 oxides contain MnS phases and MnS precipitation is accompanied by an Mn-depleted zone around the oxides. This zone was created
not just around the MnS, but around the whole oxide inclusion. One can tentatively conclude that the majority of the MnS islands
after isothermal holding are formed by the diffusion of Mn and S from the matrix into the inclusions. 相似文献
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Influence of nonmetallic inclusion characteristics on the mechanical properties of rail steel 总被引:1,自引:0,他引:1
S. K. Dhua Amitava Ray S. K. Sen M. S. Prasad K. B. Mishra S. Jha 《Journal of Materials Engineering and Performance》2000,9(6):700-709
An extensive investigation has been carried out on six commercial heats of pearlitic rail steel to study the influence of
nonmetallic inclusion characteristics on the tensile, fatigue, and fracture toughness properties. The steels investigated
were made through the basic oxygen furnace (BOF)-continuous casting route and rolled in the rail and structural mill into
90 kg/mm2 ultimate tensile strength (UTS) grade rails. While tensile properties (yield strength [YS], UTS, and elongation) of the rail
steels investigated were found to be insensitive to inclusion type and volume fraction at their present level (0.23 to 0.45%),
the fracture toughness and high-cycle fatigue properties were found to be inclusion sensitive. The fracture toughness values
of the steels were found to range between 42.33 and 49.88 MPa √m; higher values, in general, were obtained in heats exhibiting
lower volume fractions (0.15 to 0.19%) of sulfide inclusions. The high-cycle fatigue limit, i.e., stress corresponding to 107 cycles, was found to be higher in cleaner steels, particularly in those with lower volume fractions of oxide inclusions.
This phenomenon was corroborated by scanning electron microscopy (SEM) observations of fracture surfaces, where oxide inclusions
in particular were found to be instrumental in crack initiation. Although fatigue life did not show any direct correlation
with the volume fraction of sulfides, elongated MnS inclusions were sometimes observed at crack initiation sites of fatigue-tested
specimens. 相似文献
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The strength and toughness properties of hot- rolled plates from three commercial heats of a highstrength low-alloy steel
were investigated with respect to their intrinsic microstructural and inclusion characteristics. One heat was argon purged
and contained relatively higher carbon and sulfur, whereas the other two heats, with lower carbon and sulfur levels, were
sulfide shape controlled. The study revealed that although yield and tensile strengths specific to a heat were unaffected
by testing direction, the anisotropy in tensile ductility was greater in steels with stringered sulfides. Despite similar
grain sizes in all the steels, Charpy shelf energy and impact transition temperature were significantly affected by pearlite
content and sulfide morphology and to a lesser extent by pearlite banding. The modification of stringer sulfides to tiny lenticular/globular
oxysulfides resulted in considerably higher shelf energies, lowering of impact transition temperatures, and minimal anisotropy
of impact properties. The macroscopic appearance of splitting on the fracture surfaces of transverse Charpy specimens associated
with low impact energies confirmed failure by a low- energy mode. The presence of pancake- shaped ferrite grains and fractographic
evidence of inclusion stringers inside furrows identified their role in accentuating the splitting phenomenon. 相似文献