Titanium-bearing nonmetallic inclusions in manganese ferroalloys

Petrographic data indicate the chemical and mineralogical composition, topography, and morphology of various titanium-bearing nonmetallic inclusions of the type TiS, MnS-TiS, TiS-α-SiC, and TiS-MnS-TiC, as well as nonstoichiometric titanium sulfides and titanium carbonitrides.     

Nitrogenation of Fe-Al alloys. III: Absorption of hydrogen in nitrogenated Fe-Al alloys

Nitrogenation of Fe-2 pct Al alloys produces a large number of A1N particles and a large density of dislocations in the ferrite. We have measured the amount of nitrogen absorbed reversibly as a function of nitrogen activity at 500°C by alloys nitrogenated under different conditions. We have also measured the reversible hydrogen absorption at room temperature as a function of hydrogen fugacity and with varying amounts of preadsorbed nitrogen. Some preparative treatments produce some AIN-ferrite interface that can reversibly adsorb nitrogen at 500°C and hydrogen at 24.5°C upon sites not occupied by nitrogen. In the absence of such interface, the nitrogen absorption isotherms and the nitrogen-free hydrogen absorption isotherms are adequately described by a model based upon the thermodynamics of stressed bodies. However, the observed decrease of absorbed hydrogen caused by preabsorbed nitrogen is not explicable by the simple idea that a site occupied by nitrogen is unavailable to hydrogen.     

Nature and diagnostics of nonmetallic inclusions in steels

The chemicomineralogical nature of nonmetallic inclusions (NIs) in a number of steel grades prepared by traditional melting, elecroslag refining, and casting has been studied. Suboxides and phases having variable nonstoichiometric compositions are found to comprise nonmetallic inclusions. Their role in the formation of the properties of steel is demonstrated.     

Phase relationships in the iron-rich Fe-Al alloys

X-ray diffraction study of isothermally annealed powder specimens of Fe-Al alloys with 18.75 to 32 at. pct Al indicates that the α + FeAl two-phase field closes at around 662‡C where both phases have the same composition: 23.9 at. pct Al. X-ray diffraction and magnetic data show that any twophase field that may exist between the FeAl and Fe₃Al phases must be extremely narrow. It is probable that there is no two-phase field and that the transition is of a higher than first order type.     

Interaction of metal matrix with nonmetallic inclusions in rail steel

The stress at the boundary between nonmetallic oxide inclusions and the matrix may be calculated, for different loads, by simulation of the system consisting of the matrix and inclusions. On that basis, the nonmetallic inclusions may be ranked in terms of the risk of contact-fatigue defects. The phase composition and geometry of the nonmetallic inclusions in rail steel are determined by the reduction of the rail steel and are extremely important for high rail performance.     

连铸大方坯非金属夹杂物研究

通过定量金相法和化学电解法对连铸生产时不同浇铸部位连铸坯内部非金属夹杂物的分布情况进行了详细分析,结果表明,连铸时首炉第1支连铸坯的夹杂物明显多于其它连铸坯;铸坯中的硫化物夹杂以硫化铁为主;氧化物夹杂以二氧化硅为主;在连铸坯的内外弧1/4处及左右宽度的1/4处夹杂物分布最多.     

无缝钢管中非金属夹杂物特性研究

峰位于4869 eV位置,对应于元素锡的四价氧化态。锡泥中含有的主要成分为SnO2。     

钙处理对铝镇静钢中非金属夹杂物变性效果的影响

通过对LF前-LF后-中间包-连铸工艺生产40Cr钢各环节系统取样,以及电子显微镜对夹杂物的形貌、尺寸及组成的分析,发现40Cr铸坯中含有大量CaO(CaS)-Al₂O₃-MgO类复合夹杂.采用Factsage计算得到的CaO-CaS-Al₂O₃三元相图对钙处理后CaO(CaS)-Al₂O₃夹杂形成过程进行了理论计算;并对实际发现的CaO(CaS)-Al₂O₃-MgO类复合夹杂物的面扫描分布进行描边处理,探讨了该类夹杂物的组成和形成过程.经Factsage理论计算发现,CaO-CaS-Al₂O₃三元相图中液相区各成分质量分数为CaO 32%~58%、CaS 0%~5%以及Al₂O₃42%~65%,钙处理后CaO含量有逐渐增加,CaS含量有逐渐减小趋势.结合夹杂物的面扫描分布发现,CaO(CaS)-Al₂O₃-MgO类复合夹杂物的组成为xCaO·yAl₂O₃+mMgO·nAl₂O₃+Al₂O₃+CaS,钙处理后Ca能够使Al₂O₃变性为CaO-Al₂O₃,但同时夹杂物中也有很高的CaS成分,随着钙处理的充分进行,CaS将由内及外向CaO-Al₂O₃逐渐转变.     

Production of continuous-cast pipe blank without large nonmetallic inclusions

The quality of metal in continuous-cast pipe blanks is investigated, for different steel-production technologies. The presence of large nonmetallic inclusions is largely due to disruptions in the continuouscasting technology. Other significant factors are nonoptimal modification of the nonmetallic inclusions and problems in ladle treatment. Measures ensuring acceptable content of nonmetallic inclusions are developed and tested.     

Crystallographic textures in rolled and annealed Fe-Ga and Fe-Al alloys

The feasibility of obtaining [001] preferred texture in polycrystalline Fe₈₅Ga₁₅ and Fe₈₅Al₁₅ magnetostrictive alloys containing 1 mol pct NbC using a low-cost conventional thermomechanical processing approach is shown in this work. Thermomechanical processing conditions examined consisted of a sequence of hot rolling, two-stage warm rolling at 400 °C with intermediate anneal at 900 °C and texture anneal in the temperature range of 900 °C to 1300 °C for time periods up to 24 hours. Textures present prior to and after texture annealing were characterized using orientation imaging microscopy in a scanning electron microscope. In the case of Fe₈₅Ga₁₅ alloy with 1 mol pct NbC, the deformation-induced texture after a two-stage warm rolling consists of mixed {100} 〈110〉 and {111} 〈110〉 type partial textures. Texture annealing of the Fe₈₅Ga₁₅ alloy with 1 mol pct NbC at 1150 °C for 2 hours changes the texture to a predominant texture that is close to {001}〈100〉. On increasing the annealing time to 24 hours, the texture shifts toward {110}〈100〉. While texture anneal at both 1150 °C and 1300 °C produces a [001] or near-[001] preferred orientation along the rolling direction in the Fe₈₅Ga₁₅ alloy with 1 mol pct NbC, 1150 °C-24 hour treatment was found to provide the strongest [001] orientation among the conditions examined. Similar trends are observed for the case of Fe₈₅Al₁₅ alloy with 1 mol pct NbC.     

The electron metallography of ordering reactions in Fe-Al alloys

The microstructural changes during the α→ FeAl, FeAl → Fe₃Al, and α→ Fe₃Al transitions were studied by transmission electron microscopy. The ordering of ferromagnetic α was observed to occur in a classical manner by the nucleation and growth of particles of the FeAl or Fe₃Al type phases. However, the ordering of paramagnetic α to FeAl and paramagnetic FeAl to Fe₃Al occurred by a mechanism which showed many of the characteristics expected of a second or higher degree transition. These included critical point fluctuations in the degree of long-range order which also appeared to be greater in the vicinity of antiphase domain boundaries. The FeAl phase was also observed to partially disorder in the initial stages of the FeAl → α + FeAl transition and this effect appears to account for the anomalous magnetic behavior of some FeAl alloys.     

Influence of nonmetallic inclusions in rail steel on the high-temperature plasticity

The influence of nonmetallic inclusions in Э76Ф rail steel on the high-temperature plasticity is considered. In terms of the shear strain, a plasticity maximum is observed in all three zones of the continuouscast billet: the crust, the columnar-crystal zone, and the central zone of the billet. The high-temperature torsion of samples heated to 950–1250°C with 10-min holding is studied for continuous-cast billet of electrosmelted rail steel. Oxides and silicates are present in the crust; oxides and oxysilicates are found in the columnar-crystal zone; and sulfides, oxides, silicates, and alumosilicates are found in the central zone of the billet. The concentration of inclusions that impair the plasticity is greatest in the central zone of the billet.     

Investigations of inclusions in ferrochromium alloys

Abstract

Ferrochromium alloys are commonly added during different stages of steelmaking processes according to the specific steel grade being produced. Depending upon the ferrochromium quality, the addition can also lead to a supply of deleterious inclusions to the liquid steel. Therefore, the number, size, morphology and composition of inclusions in LCFeCr and HCFeCr alloys were investigated. The alloy samples were first treated with electrolytic extraction, followed by filtration to gather the inclusions on a film filter. Thereafter, the characteristics of the inclusions and clusters were investigated in three dimensions by SEM in combination with energy dispersive spectroscopy. The results show that the main inclusion types found in LCFeCr alloys are different to those found in HCFeCr alloys. More specifically, the inclusions in LCFeCr alloys were found to consist of Si–Cr–O and Cr–O oxides as well as intermetallic Cr–Fe inclusions. Moreover, the inclusions in HCFeCr alloys were found to consist of Cr–Mn–S, Cr–C–N, Si–Al–Ca–Mg–O and Ca–O–P inclusions. Overall, the inclusions can be divided into two categories depending on the melting point. Furthermore, the possible transformation of different inclusions after their addition to the liquid steel is discussed.     

钙处理对20CrMnTiH齿轮钢中非金属夹杂物的影响

铝脱氧齿轮钢中易生成大量的高熔点Al₂O₃类夹杂物,容易导致水口结瘤及钢材性能恶化,目前较常采用钙处理将钢中高熔点的Al₂O₃类夹杂物改性为低熔点的钙铝酸盐类夹杂物。合理的钙处理可以减轻水口结瘤并提高连铸过程钢液的可浇性,工业试验研究了喂钙前钢液中T.Ca含量、喂钙速度、喂钙量、净空高度及渣厚等参数对齿轮钢中钙收得率的影响,并在1.5 m·s?1的喂钙速度条件下研究了不同喂钙量对钙处理过程中齿轮钢中非金属夹杂物改性的影响。研究结果表明,当喂钙前钢液中T.Ca的质量分数小于10×10?6,喂钙速度为1.5 m·s?1,适当降低喂钙量和净空高度和渣厚,钢液中钙收得率均高于20%。当钢液中T.Ca的质量分数高于17×10?6时,钢中生成大量高熔点CaS型夹杂物,三元相图中夹杂物的平均质量分数远离液相区。随着齿轮钢中T.Ca含量的增加,夹杂物的平均尺寸和数密度逐渐增加。热力学计算结果与工业试验钙处理对钢中非金属夹杂物改性效果具有较好的一致性。      

Formation of nonmetallic inclusions in the carburization of steel by high- and low-ash reagents

The solution of high-ash carburizing agents (dry-quenching dust, coke breeze) and low-ash agents (MU-95) in molten steel is studied. Relatively stable C–O and C–O–Fe complexes are formed on solution. When high-ash carburizing agents are introduced in the melt, the liberation of volatiles leads to decrease in their particle size, increase in the open pore volume, and faster exchange of carbon and iron between the phases. Carbon from low-ash carburizing agents dissolves mainly through the outer surface of the particles. The oxygen present forms C_xO_y complexes with the remaining carbon, on account of strong C–O bonds. Consequently, the assimilation rate of the carburizing agents is reduced. The solution of the inclusions may be accelerated by introducing optimal quantities of rare-earth elements that reduce the carbon–oxygen complexes.