24 research outputs found
THE INFLUENCE OF CHEMICAL COMPOSITION OF HIGH-CHROMIUM CAST IRONS ON THE MACHINABILITY
No full textPurpose. This research is aimed to obtain the regression dependence of the machinability on the chemical composition of pig iron (C, Cr, Mn and Ni) in cast state. Methodology. The method of active experiment planning was used to build a mathematical model. Cast irons of composition 1.09…3.91 % С; 11.43…25.57 % Cr; 0.6…5.4 % Mn; 0.19…3.01 % Ni were studied. Cutting tools with plates 10х10 mm out of ВК8 according to State Standard 19051-80 were used for turning. Cutting modes: cutting depth – 0.8 mm, longitudinal feed – 0.15 mm/rot., spindle’s rotation frequency during turning – 200…360 rot./min. Lubricating and cooling liquids were not applied. Evaluation of iron workability was produced by determining the linear tool flank wear per unit length of the cutting path. Findings. Mathematically probabilistic equation of the regression dependence of the cutting tool’s wear on the C, Cr, Mn and Ni content in the machined cast iron were obtained. It was established that with the increase of Cr content in the cast iron to 14.8 % the cutting tool’s wear decreased as a result of formation of carbide eutectic which destroyed the doped ledeburite continuous frame. Further increase of chromium content promoted appearing of chromic carbides with high microhardness which considerably increased the tool’s wear. The conducted research shown that the minimum cutting tool’s wear 0,18 mkm/m was observed during the machining of cast iron containing: 1.09 % C, 14.8 % Cr, 2.3 % Mn and 1.2 % Ni; and the maximum wear is 48,96 mkm/m – when the content was: 3.91 % C, 11.43 % Cr, 5.4 % Mn and 0.19 % Ni. The tool’s wear reached 47.61 mkm/m during the treatment of cast iron containing 3.91 % C, 25.57 % Cr, 5.4 % Mn and 0.19 % Ni. Originality. Mathematically probabilistic model of the dependence of the cutting tool’s wear on the C, Cr, Mn and Ni content in the machined cast iron has been elaborated by the author. Practical value. The model allows optimizing the compositions of wear-resistant cast irons for castings which require the significant mechanical machining. Cast irons compositions were recommended for different exploitation conditions
PECULIARITIES OF PROCESSES OF CARBIDE FORMATION AND DISTRIBUTION OF Cr, Mn AND Ni IN WHITE CAST IRONS
No full textDuring crystallization of castings from white cast iron, carbides Me3С, Me7С3, Me23С6 were formed depending on chromium and carbon content. Impeded chromium diffusion caused formation of thermodynamically unstable and non-uniform phases (carbides). During heat treatment process stable equilibrium phases were formed as a result of rearrangement of the carbides’ crystal lattice, replacement of iron, manganese, nickel and silicon atoms by chromium atoms. The allocated atoms concentrated, forming inclusions of austenite inside the carbides. Holding during 9 hours at 720 °С and annealing decreased the non-uniformity of chromium distribution in the metallic base of cast iron containing 11,5 % Cr, and increased it in the cast iron containing 21,5 % Cr. Holding during 4.5 hours at 1050 °С and normalization decreased the non-uniformity of chromium distribution in the metallic base of cast iron containing 21,5 % Cr, and increased it in cast iron containing 11,5 % Cr
Morte, música e sexualidade na Ópera Turandot de Puccini
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Comunicação e Expressão. Programa de Pós-Graduação em Literatura.Esta dissertação pretende ser uma análise multiangular da ópera Turandot, de Giacomo Puccini (1858-1924). Deixada incompleta pelo compositor e encenada pela primeira vez em 1926, esta ópera é vista pelos musicólogos William Ashbrook e Harold Powers como marco do fim da grande tradição operística da Itália. O trabalho considera o entrelaçamento das convenções musicais e das convenções discursivas da partitura músico-textual de Turandot, a fim de esclarecer como analogias, referências e contradições musicais podem contribuir para a eficácia da narrativa verbal. O estudo de Turandot levou à reflexão da ópera como gênero e a dissertação está organizada pela gradual exploração das camadas da obra, da mais externa, a ópera em geral, até a reflexão sobre a psicologia de suas personagens, passando pela influência mútua entre música e narrativa nas idiossincrasias de Turandot como construção músico-literária singular. This paper intends to be an analysis from many angles of the opera Turandot, by Giacomo Puccini (1858-1924). Left incomplete by its composer and taken to the stage for the first time in 1926, this opera is regarded by musicologists William Ashbrook and Harold Powers as the ending of Italy's great operatic tradition. This work considers the intertwining of musical and speech conventions from Turandot's musical and textual score, with the objective of clarifying how musical analogies, references and contradictions may contribute to verbal narrative's effectiveness. The analysis of Turandot led to the reflection of opera as genre, so the paper is organized according to the gradual exploring of that opera's layers, from the most external - that is, the opera in general - to the reflection over its characters' psychology, passing by the mutual influence between music and narrative in Turandot's idiosyncrasies as a musical-literary unique construction
Influence of the chemical composition of high-chromium cast iron on the content of chromium in near-carbide zones after annealing at 720 °С
No full textНетребко В. В. Вплив хімічного складу високохромистого чавуну на вміст хрому у зонах біля карбідів після відпалу при 720 °С / В. В. Нетребко // Нові матеріали і технології в металургії та машинобудуванні. – 2022. – № 2. – C. 13-18.UK: Мета роботи. Підвищення корозійної стійкості зносостійких високохромистих матеріалів, що працюють в умовах рідкого абразивного середовища, дозволяє збільшити експлуатаційну стійкість виробів з цих матеріалів, що є важливим завданням матеріалознавства. Однією з основних причин виникнення руйнівних корозійних процесів є нерівномірність розподілу хрому в металевій основі, що призводить до утворення мікрогальванічних пар на поверхні деталей, що знаходяться в електролітичному середовищі. Створення зносостійких високохромистих сплавів, в металевій основі яких не утворюються мікрогальванічні пари, є перспективним напрямком підвищення корозійної стійкості таких матеріалів. Дослідження процесів розподілу хрому після термічної обробки деталей з високохромистих чавунів, а саме формування зон металевої основи біля карбідів було здійснено.
Методи дослідження. Аналітичний огляд публікацій. Металографічний, мікроструктурний та локальний мікро-рентгеноспектральний аналізи. Математичне модулювання процесів.
Отримані результати. Виявлено, що в процесі термічної обробки в високохромистих чавунах утворюються структури із значною ліквацією хрому. Встановлено, що після відпалу виливок при 720 °С мінімальний вміст хрому в металевій основі спостерігається у зонах біля карбідів, а максимальний у центральних частинах зерен. Наявність в металевій основі зон із вмістом хрому більше 12 % (позитивний потенціал) і менше 12 % (негативний потенціал) призводить до утворення мікрогальванічних пар, що є головною причиною пришвидшення корозійного руйнування. Визначена залежність вмісту хрому в зонах біля карбіду після відпалу при 720 °С від хімічного складу чавуну.
Наукова новизна. Запропоновано математичну модель визначення вмісту хрому в зонах біля карбідів після відпалу при 720 °С з витримкою 9 годин від хімічного складу чавуну в системі Fe-C-Cr-Mn-Ni. Це дозволяє прогнозувати вміст хрому у зонах біля карбів та запобігати утворенню мікрогальванічних пар.
Практичне значущість. Отримана залежність (математична модель) може бути використана при розробці складів високохромистих зносостійких чавунів, з підвищеної корозійною стійкістю та оброблюваністю різанням.
EN: Purpose. Increasing the corrosion resistance of wear-resistant high-chromium materials operating in a liquid abrasive environment makes it possible to increase the service life of products made from these materials, which is an important task in materials science. One of the main reasons for the occurrence of damage during corrosion processes is the uneven distribution of chromium in the metal base, which leads to the formation of microgalvanic pairs on the surfaces of parts in an electrolytic environment. The creation alloys of wear-resistant high-chromium, in the metal base of which microgalvanic vapors are not formed, is a promising direction for increasing the corrosion resistance of such materials. Investigation of chromium distribution processes after heat treatment parts of high-chromium cast iron, namely the formation of metal base zones near carbides.
Research methods. Analytical review of publications. Metallographic, microstructural and local X-ray microanalysis. Mathematical modeling of processes.
Results. It was revealed that during the heat treatment in high-chromium cast irons, structures with significant segregation of chromium are formed. It has been established that after annealing of castings at 720 °C, the minimum chromium content in the metal base is observed in the zones near carbides, and the maximum in the central zones of the graids. The presence zones with a chromium content of more than 12 % (positive potential) and less than 12 % (negative potential) leads to the formation of microgalvanic couples, which is the main reason for the acceleration of corrosion damage in the metal base. The dependence of the chromium content in the zones near the carbides after annealing at 720 °C on the chemical composition of cast iron has been determined.
Scientific novelty. The mathematical model is proposed for determining the chromium content in the zones near carbides after annealing at 720 °C with an exposure of 9 hours from the chemical composition of cast iron in the Fe-C-Cr-Mn-Ni system. This makes it possible to predict the chromium content in the zones near the carbides and prevent the formation of microgalvanic pairs.
Practical value. The dependence (mathematical model) obtained can be used in the development of compositions of high-chromium wear-resistant cast irons with increased corrosion resistance and machinability
INFLUENCE OF THE CAST IRON’S CHEMICAL COMPOSITION ON THE INTERPHASE DISTRIBUTION OF CR AFTER ANNEALING AT 690 °C
No full textPurpose. The article is aimed to determine effect of the chemical composition of Fe-C-Cr-Mn-Ni cast iron on the chromium content in the metallic base, carbides and the coefficient of interphase distribution of chromium after annealing at 690 ° С (КРСr690). Methodology. Cast irons containing 1.09–3.91% C; 11.43–25.57% Cr; 0.6–5.4% Mn; 0.19–3.01% Ni and 0.8–1.2% Si were investigated. The analysis of chromium distribution was carried out using mathematical statistics methods. Cast iron was melted in induction furnace with a capacity of 60 kg. Findings. The use of methods of active planning of the experiment 24-1 allowed us to establish regression dependencies of the chromium concentration in the base and carbides, as well as its interphase distribution coefficient on the С, Mn, Cr and Ni content in the cast iron. Chromium, after annealing, was mainly concentrated in carbides. The chromium content of the base varies from 3.94% at 3.23% C, 5.4% Mn, 11.43% Cr and 3.01% Ni to 17.43% at 1.09% C, 0.60% Mn, 25.57% Cr and 1.32% Ni. The minimum value of the distribution coefficient of CRC690 was 2.1 in cast iron, of composition 1.09% C, 0.6% Mn, 11.43% Cr and 0.19% Ni, maximum 9.4 at 3.91% C, 0, 6% Mn, 11.43% Cr and 3.01% Ni. The distribution of chromium was determined by the amount and type of carbides formed. During annealing, the carbides’ composition was formed as a result of carbide-forming elements contention and replacement of iron and manganese atoms by chromium atoms. Originality. Authors obtained regression dependences of the chromium content in the base, carbides and its interfacial distribution coefficient on the chemical composition of Fe-C-Cr-Mn-Ni cast iron after annealing at 690 ° C. Practical value. The obtained dependencies allow predicting the chromium content in the metallic base and may be used during the elaboration of the new wear resistant cast irons compositions, as well as in the choice of heat treatment regimes
THE INFLUENCE OF CHEMICAL COMPOSITION ON THE CORROSION RATE OF HIGH-CHROMIUM CAST IRON
No full textThe influence of the chemical composition on the corrosion rate of high-chromium cast iron was researched. During the castings’ cooling process the replacement of the atoms of nickel, iron and manganese by the atoms of chromium in the carbides took place. As a result, the areas with reduced chromium content were formed near carbides. After decreasing the chromium content in these areas below 12% the corrosion processes activated. Using the mathematical experimental design techniques the regression dependence between the corrosion rate of the cast irons and content of C, Cr, Mn and Ni in them was established. The conducted research showed that the minimum corrosion rate was observed in the cast iron containing: 1.09% C, 25.57% Cr, 0.6% Mn and 1.87% Ni. The obtained results allow predicting the corrosion rate of the high-chromium cast irons alloyed with Mn and Ni and may be used while establishing the new compositions of wear-resistant materials
INFLUENCE OF THE CAST IRON’S CHEMICAL COMPOSITION ON THE INTERPHASE DISTRIBUTION OF MN
No full textPurpose. This paper focuses on obtaining the dependencies of the manganese content in the metallic base (Mno) and its interphase distribution coefficient (KPMn) on the cast iron’s chemical composition in the system Fe–C–Cr – Ni –Mn. Methodology. The cast irons containing 1.09…3.91% С, 0.6…5.4 % Mn, 11.43…25.57 % Crand 0.19…3.01 % Ni have been studied. The active experiment design techniques were applied to build a mathematical model of manganese distribution. Cast iron was smelted in the induction furnace with the capacity of 60 kg, with basic lining.Findings.Manganese, being a carbide-forming element, distributed between carbides and the metallic base. With the use of the mathematical statistics methods, regression dependencies of the manganese concentration in the base and its interphase distribution coefficient on the С, Mn, Cr and Ni content in the cast iron were established. The manganese concentration in the base varied from 0.37 % at 1.09 % С, 0.6 % Mn, 11.43 % Cr and 3.01 % Ni to 5.79 % at1.09% С, 5.4 % Mn, 25.57 % Cr and 0.19 % Ni. The minimum value of the interphase distribution coefficient was 0.16 in the cast iron containing 1.09 % С, 0.6 % Mn, 25.57 % Cr and 3.01 % Ni. When the КРMn coefficient values were lower than 1, manganese concentrated predominantly in the metallic base. The maximum value of the КРMn coefficient was 2.48 at 3.91 % С, 0.6 % Mn, 11.43 % Cr and 0.19 % Ni. The manganese distribution pattern was determined by the carbides’ quantity and chromium and carbon ratio that determined the carbide type. The carbides’ composition was formed as a result of carbide-forming elements contention. Originality. Regression dependencies of the manganese content in the base and its interphase distribution coefficient on the cast iron’s chemical composition in the system Fe–C–Cr – Ni –Mn have been obtained. The dependency of the manganese distribution on the carbide forming processes has been established. Practical value. The obtained dependencies allow predicting the manganese content in the metallic base and may be used during the elaboration of the new wear resistant cast irons compositions
INFLUENCE OF THE CAST IRON’S CHEMICAL COMPOSITION ON THE CONTENT OF CR IN THE BASE AFTER NORMALIZATION FROM 1050 C
No full textThe dependences of the influence of the chemical composition of cast iron in the Fe-Cr-Mn-Ni system on the chromium cotent in the metal base (Cr1050о) and carbides (Cr1050Cr) after normalization from 1050 °C with aging for 4.5 hours were established. During the heat treatment of the castings, a redistribution of the elements between the phases of the cast iron occurred. The maximum chromium concentration in the base after normalization was 19.7% at 1.09% C, 3.1% Mn, 25.5% Cr and 0.19% Ni, and the minimum 2.4% at 3.91% C, 0.6% Mn, 11.43% Cr and 0.19% Ni. The maximum amount of chromium in carbides 78.4% was observed in cast iron containing 1.09% C, 5.4% Mn, 3.01% Ni and 25.57% Cr, and the minimum 43.5% at 3.59% C, 5.4% Mn, 3.01% N and11.43% Cr. The obtained dependencies allow predicting the chromium content in the metallic base and can be used during the elaboration of new compositions for wear-resistant cast iron, as well as at choice of heat treatment regimes
