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EN
Nodular cast irons are used in a wide range of industrial applications, especially in the automotive industry. SiMo-type of nodular cast iron is suitable for high-temperature applications, for example the exhaust manifolds of the combustion engines; SiCu-type of nodular cast iron is used in various components of tribotechnical units. These automotive components often work in a corrosive environment. Therefore, the aim of this paper is to compare the corrosion resistance of two types of the nodular cast irons (SiMo-type and SiCu-type). Corrosion resistance was determined by the exposure immersion test at ambient temperature. Specimens of both types of nodular cast iron were immersed in 3.5 % NaCl solution (to simulate sea water) and gradually removed from the solution after 1, 2, 4 and 8 weeks. Subsequently, the weight loss (g) and the average corrosion rate (g m-2 day-1) were calculated. Experimental results show that nodular cast iron alloyed by Si and Mo has higher corrosion resistance than the nodular cast iron alloyed with Si and Cu. Moreover, the mechanical properties (evaluated by tensile test, impact bending test and hardness test) and fatigue properties of both types of nodular cast iron has been compared in the paper.
EN
Chunky graphite has been recognized for a long time as one of the major problems in production of heavy section nodular cast iron. A great number of studies have been conducted to describe the chunky graphite formation, but a clear understanding of its appearance and a safe mastering of the melt preparation to avoid chunky graphite are not yet available. In the present work the cooling curves were recorded in large cone blocks and standard TA cup. According to measured data from the cone block, melt characteristics and heat transfer coefficient between casting and mould were adjusted in the ProCAST® simulation software. For a near-eutectic nodular cast iron test melt with 0.7 wt.% Ni, relationship between the area of the cone block affected by chunky graphite and simulation software results has been observed, i.e., thermal modulus and time to solidus.
EN
In recent years, the research of nodular cast iron has been focused on increasing fatigue resistence. In the paper, two types of alloyed nodular cast irons have been investigated – SiMo-nodular cast iron alloyed by 4% of silicon and 1% of molybdenum and SiCu-nodular cast iron alloyed by 4% of silicon and 1.5% of copper. SiMo-nodular cast iron is suitable for high-temperature applications, for example the exhaust manifolds of the combustion engines. SiCu-nodular cast iron is used in various components of tribotechnical units. These components are often loaded by fatigue. The mechanical and fatigue behaviour of both nodular cast iron types has been studied by means of tensile test, impact bending test, hardness test and fatigue tests. Fatigue tests were realised at low frequency cyclic push-pull loading up to 10 million cycles. The relationship between the amplitude of stress and number of cycles to failure was investigated and the fatigue strength was determined. Mechanical and fatigue properties of both nodular cast iron types are correlated with the microstructure of specimens.
4
Content available remote Influence of changes in machinability of nodular cast iron on manufacturing costs
EN
Attempts to explain changes in the efficiency of nodular cast iron machining caused by the dispersion of its mechanical properties affecting on the intensity of tools wear (such as VHM drills) have been presented. It has been also assessed to what extent changes in mechanical properties of tools, within the limits of the standards, can change the machining efficiency in quite intensive machining conditions of the automotive industry.
PL
Podjęto próbę wyjaśnienia zmian efektywności obróbki żeliwa sferoidalnego; było to spowodowane rozrzutem jego właściwości mechanicznych, odbijającym się na intensywności zużywania się narzędzi (w tym wypadku wierteł z węglików spiekanych). Oceniono, na ile zmiany właściwości mechanicznych narzędzi – mieszczące się w granicach norm – mogą wpływać na efektywność obróbki w dość intensywnych warunkach skrawania w przemyśle motoryzacyjnym.
EN
Effects of charge composition on microstructure, mechanical and fatigue properties of nodular cast irons have been studied. For experiments, five melts of nodular cast iron were used – three types of unalloyed nodular cast irons (with different ratio of steel and pig iron in a charge and different additives for regulation of the chemical composition) and two types of alloyed nodular cast irons (SiMo- and SiCu- nodular cast iron). The microstructure of the specimens was evaluated according to a norm and by automatic image analysis. The mechanical properties were investigated by the tensile test, impact bending test and Brinell hardness test. The fatigue tests were carried out at sinusoidal cyclic push-pull loading at ambient temperature. The best mechanical properties were reached in the nodular cast iron alloyed by Si and Cu, what is related to its microstructure.
EN
The paper presents the initial results of investigation concerning the abrasion resistance of cast iron with nodular, vermicular, or flake graphite. The nodular and vermicular cast iron specimens were cut out of test coupons of the IIb type with the wall thickness equal to 25 mm, while the specimens made of grey cast iron containing flake graphite were cut out either of special casts with 20 mm thick walls or of the original brake disk. The abrasion tests were carried out by means of the T-01M tribological unit working in the pin-on-disk configuration. The counterface specimens (i.e. the disks) were made of the JT6500 brand name friction material. Each specimen was abraded over a distance of 4000 m. The mass losses, both of the specimens and of the counterface disks, were determined by weighting. It was found that the least wear among the examined materials was exhibited by the nodular cast iron. In turn, the smallest abrasion resistance was found in vermicular cast iron and in cast iron containing flake graphite coming from the brake disk. However, while the three types of specimens (those taken from the nodular cast iron and from grey cast iron coming either from the special casts or from the brake disk) have almost purely pearlitic matrix (P95/Fe05), the vermicular cast iron matrix was composed of pearlite and ferrite occurring in the amounts of about 50% each (P50/Fe50). Additionally, it was found that the highest temperature at the cast iron/counterface disk contact point was reached during the tests held for the nodular cast iron, while the lowest one occurred for the case of specially cast grey iron.
7
Content available Analysis of Cooling Curves of Nodular Cast Iron
EN
The solidification of cast iron is a complex process with characterized entrance and marginal conditions. Thermal analysis is one of the processes that allows us to observe the solidification of alloys. There is a possibility of gaining information about the melted cast iron quality and predicting the final properties of the cast by evaluating the scanned cooling curves by solidification (stable and metastable system). This article deals with the study and analysis of cooling curves taken from production conditions of a foundry during ductile cast iron production. The aim is to discover the reproduction and reliability of the thermal analysis results of cast iron. The study of the progress of the cooling curves and their first derivation to follow the reactions of the curves to changing factors in the production process.
8
Content available remote MMA Repair Welding of Nodular Cast Iron GJS 350-22
EN
The article presents results of the MMA repair welding of nodular cast iron GJS 350-22. Casting defects were simulated mechanically (through milling), whereas repair welding was performed using selected filler metals (low-carbon filler metal, austenitic filler metal, Monel alloy and nickel alloy) and the manual metal arc welding method (MMAW). Test welds were subjected to visual, penetrant, macro and microscopic tests as well as hardness measurements and were compared in terms of the colour with that of the base material. The tests made it possible to identify the effect of the repair welding process on structural changes in the HAZ area and the susceptibility to crack generation both in the HAZ and in the weld. The tests also enabled the determination of structures of repair welds and their usability when repairing iron casts. The hardness measurements confirmed effects related to structural changes triggered by repair welding in the HAZ and in the weld. In turn, the comparative tests concerning the colour of the weld and that of the repaired cast iron enabled the selection of a filler metal satisfying the above-named criterion. The tests revealed that the highest properties of the repair weld in terms of structural changes were obtained using nickel-based filler metals.
PL
Przedstawiono skutki procesu spawania naprawczego metodą MMA odlewów z żeliwa sferoidalnego GJS 350-22. Symulowane wady odlewnicze były wykonane poprzez proces mechaniczny (frezowanie), a spawanie naprawcze zostało przeprowadzone wytypowanymi spoiwami (spoiwo niskowęglowe, spoiwo austenityczne, stop Monela, spoiwo niklowe) metodą spawania ręcznego elektrodami otulonymi. Uzyskane spoiny naprawcze poddano: badaniom wizualnym, penetracyjnym, makro i mikrostruktury, pomiarom twardości oraz porównaniu barwy napoiny do barwy materiału rodzimego. Na podstawie badań określono wpływ procesu spawania naprawczego na zmiany strukturalne w obszarze SWC i skłonność do generowania pęknięć w tej strefie i w obszarze spoiny. Określono struktury spoin naprawczych oraz ich przydatność w naprawach odlewów żeliwnych. Przeprowadzone pomiary twardości potwierdziły efekty związane ze zmianami strukturalnymi wywołanymi procesem spawania naprawczego w SWC i w spoinach, a badania porównawcze dotyczące barwy spoiny i naprawionego żeliwa pozwoliły na wytypowanie spoiwa pozwalającego spełnić to kryterium. Przeprowadzone badania wykazały, że najlepsze własności spoin naprawczych pod względem zmian strukturalnych uzyskuje się w przypadku spoiw na osnowie niklu.
EN
The study reported in this paper was aimed at establishing the effect of values of parameters characterizing the process of superficial remelting of a nodular iron casting on the quantity of introduced heat, geometry of remeltings as well as parameter λ and hardness of cementite eutectic. The remelting process was carried out using GTAW method, at electric arc length of 3 mm in argon atmosphere, welding current intensities I = 50, 130, 210, and 300 A, and electric arc scanning speeds vs = 200, 400, and 800 mm/min. The measurements included estimation of the quantity of heat introduced to the casting in the electric arc-induced remelting process with the use of flow calorimeter. Widths and depths of remetlings were assessed with the use of metallographic method. As a result of fast solidification, cementite eutectic was obtained in remelted material in which, in the course of cooling down to ambient temperature, austenite was subject to partial transformation into martensite. To characterize the cementite eutectic, value of the structural parameter λ was assessed. Values of the parameter were similar for areas of occurrence of both fibrous and laminated eutectic. Remeltings were examined at half of their depths. Micro-hardness measurements were taken in the same areas. The established quantitative relationships may prove to be useful in practice for the purpose of predicting values of parameter λ and hardness of remeltings in studies aimed at improving resistance of cast-iron castings to abrasive wear.
EN
The paper deals with the influence of charge composition on microstructure and mechanical properties of synthetic nodular cast irons after casting and after heat treatment (ferritizing annealing and isothermal heat treatment). Chemical composition of individual melts was regulated alternatively by carburizer and ferrosilicon (FeSi) or metallurgical silicon carbide (SiC). The results of experiments show that SiC additive positively influences the microstructure as well as mechanical properties of nodular cast iron, especially in specimens from the melts with higher ratio of steel scrap in the charge.
11
Content available Comparison of low and high frequency fatigue tests
EN
The paper presents the results of low and high frequency fatigue tests carried out on nodular cast iron. The specimens of synthetic nodular cast irons from three different melts were studied in the high cycle fatigue region (from 105 to 108 cycles) using fatigue experimental equipments for low and high frequency cyclic loading. Low frequency fatigue tests were carried out at frequency f ≈ 120 Hz using the fatigue experimental machine Zwick/Roell Amsler 150HFP 5100; high frequency fatigue tests were carried out at frequency f ≈ 20 kHz using the ultrasonic fatigue testing device KAUP-ZU. Both fatigue tests were realised at sinusoidal cyclic push-pull loading (stress ratio R = –1) at ambient temperature (T = 20 ± 5 °C).
EN
Three melts of ferrite-pearlitic nodular cast iron with different charge composition were used for fatigue tests. Wöhler fatigue curves and fatigue strength were obtained, and microstructure and fracture surfaces were investigated. The aim of the paper is to determine the influence of charge composition on microstructure, mechanical and fatigue properties of synthetic nodular cast irons and their micromechanisms of failure. Fatigue tests were realised at low frequency sinusoidal cyclic push-pull loading (stress ratio R = −1) at ambient temperature (T = 20 ±5°C). They were carried out with using the fatigue experimental machine Zwick/Roell Amsler 150HFP 5100 at frequency f ≈ 120 Hz. The results of fatigue tests at low frequency cyclic loading are compared with fatigue properties at high frequency cyclic loadin.
EN
The paper deals with susceptibility of nodular cast iron with ferritic-pearlitic matrix on cavitation erosion. Cavitation tests were carried out with the use of a cavitation erosion vibratory apparatus employing a vibration exciter operated at frequency of 20 kHz. The study allowed to determine the sequence of subsequent stages in which microstructure of cast iron in superficial regions is subject to degradation. The first features to be damaged are graphite precipitates. The ferritic matrix of the alloy turned out to be definitely less resistant to cavitation erosion compared to the pearlitic matrix component.
EN
The paper presents the microstructure and selected properties of ausferritic nodular cast iron annealed at the temperature 520 and 550°C. This choice was dictated by the temperatures used in the practice of nitriding. Nodular graphite in cast iron was obtained with use of Inmold process. Cast iron containing molybdenum and copper ensuring obtaining an ausferrite in the cast iron matrix without the use of heat treatment of castings was tested. The effect of annealing temperature on the microstructure and the kind of fracture of the ausferritic nodular cast iron was presented. The effect of an annealing temperature on hardness, impact strength and the microhardness of ausferritic nodular cast iron matrix was shown too. The lamellar structure of phases in the cast iron matrix after annealing has been ascertained. There has been an increase in hardness of an annealed cast iron and microhardness of its matrix. The reduction in the impact strength of the cast iron annealed at 520 and 550°C was approximately 10-30%. Both an increase in the hardness of cast iron as well as an decrease in its impact strength is probably due to the separation of secondary carbides during the heat treatment.
PL
Przedstawiono wyniki badań toczenia poprzecznego żeliwa sferoidalnego z użyciem ostrzy skrawających wykonanych z nowoczesnego kompozytu WCCo/cBN. Program badań doświadczalnych obejmował pomiary: składowych siły całkowitej (Fc, Ff), temperatury skrawania (θ) oraz przyspieszeń drgań (Ac, Af). Uzyskane wyniki dostarczają istotnych informacji jakościowych i ilościowych o przebiegu procesu skrawania żeliwa sferoidalnego ostrzami z kompozytu WCCo/cBN.
EN
Presented in the paper are the results of grooving a nodular cast iron part by means of a tool made of modern WCCo/cBN composite. The experimental program included the measurements of: cutting force components (Fc, Ff), cutting temperature (θ) and vibration accelerations (Ac, Af). The research results provide essential qualitative and quantitative information on the process of machining the nodular cast iron part with the WCCo/cBN composite cutting edges.
PL
W artykule przedstawiono wyniki badań zmęczeniowych dwóch typów żeliwa sferoidalnego (perlityczno-ferrytycznego oraz ferrytyczno-perlitycznego) w obszarze wysokiej i ultrawysokiej liczbie cykli. Do badań zastosowano wysokofrekfencyjną maszynę zmęczeniową KAUP-ZU. Przeprowadzono badania powierzchni przełomów, badania koncentrowały się na analizie mechanizmu pękania zmęczeniowego.
EN
This paper presents the results of fatigue tests of two types of nodular cast iron (per pearlite-ferrite and ferrite-pearlite) in the high and ultra-high number of cycles. Fatigue tests were applied at high-frequency using ultrasonic testing equipment KAUP-ZU. Fracture analysis were conducted. The researches were focused on the analysis of the fatigue cracking mechanism.
17
Content available The micro-mechanisms of failure of nodular cast iron
EN
The contribution deals with a comparison of the micro-mechanisms of failure of nodular cast irons at static, impact and fatigue stress. Several specimens of ferrite-pearlitic nodular cast irons with different content of ferrite in a matrix were used for metallographic analysis, mechanical tests and micro-fractographic analysis. Mechanical properties were found by static tensile test, impact bending test and fatigue tests. The micro-fractographic analysis was made with use of scanning electron microscope VEGA II LMU on fracture surfaces of the specimens fractured by these mechanical and fatigue tests. Fracture surfaces of analysed specimens are characteristic of mixed mode of fracture. Micro-mechanism of failure of nodular cast irons is dependent on the method of stress.
PL
Przedstawiono sposób wyznaczania współczynnika tarcia w procesie skrawania nieortogonalnego ostrzem z narożem zaokrąglonym na podstawie pomiaru trzech składowych całkowitej siły skrawania w układzie narzędzia xyz. Siły działające w strefach kontaktowych wyznaczono przez transformację układu odniesienia do nowego układu lmn, w którym płaszczyzna mn jest prostopadła do powierzchni natarcia ostrza. Wprowadzono mechaniczny model obciążenia ostrza narzędzia ze ścinem, uwzględniający siły działające na powierzchni natarcia oraz – w czasie zużywania ostrza – na powierzchni przyłożenia. Porównano wartości współczynnika tarcia w modelach skrawania ortogonalnego i nieortogonalnego dla procesu skrawania żeliwa sferoidalnego za pomocą płytki skrawającej z ceramiki azotkowej.
EN
Presented is a method to estimate the friction coefficient showing in the non-orthogonal performance of nose cutting tool with reference to the three components of the resultant cutting force in the xyz coordinate system. Forces acting on contact surfaces were found by transformation of this coordinate system into a new system lmn in which the plane mn runs square to the rake face. A new mechanical model of loading applied on chamfered tool in which consideration is given to the forces acting on the rake face and on the flank land during the process of wear was introduced. The values of friction coefficient specific to orthogonal and to non-orthogonal cutting were compared with respect to machining of nodular cast iron using silicon nitride ceramic cutting bits.
EN
The aim of this research was to evaluate the influence of laser alloying with corundum on microstructure and hardness of surface layer of nodular cast iron. The molecular CO2 laser with 2600 W output power and TEM01 mode was used to perform surface modification. An optical microscope and hardness Vickers tester were used to assess the result of the surface modification. The research showed, that it is possible to modify the surface layer of nodular cast iron by laser alloying with corundum. Microstructure of the alloyed zone was similar to the hardened white cast iron. But it was very homogenous and fine-grained. The average hardness of alloyed zone with corundum was nearly 6-times higher than the matrix of the bulk material. Improved hardness of the surface layer by laser alloying with corundum could favor better wear resistance of machine parts treated in this way.
PL
Celem badań było określenie wpływu stopowania laserowego z użyciem korundu na mikrostrukturę i twardość warstwy wierzchniej żeliwa sferoidalnego. W badaniach wykorzystano laser molekularny CO2 z maksymalną mocą wyjściową 2600 W i modem TEM01. Zmodyfikowaną warstwę wierzchnią oceniono z użyciem mikroskopu optycznego i twardościomierza Vickers. Po stopowaniu laserowym uzyskano strefę stopowaną o mikrostrukturze podobnej do mikrostruktury zahartowanego żeliwa białego. Charakteryzowała się ona dużą jednorodnością i drobnoziarnistością. Średnia twardość strefy stopowanej korundem była blisko 6-krotnie większa niż twardość osnowy materiału rodzimego. Zwiększona twardość warstwy wierzchniej może korzystnie wpływać na odporność na zużycie obrobionych w ten sposób elementów maszyn.
EN
The work presents the results of the studies of the effect of the temperature on the microstructure of ausferritic nodular cast iron. The ausferrite in the matrix was obtained by way of a specific combination of molybdenum and copper. The cast iron underwent annealing at the temperatures of 520, 550 and 580°C. The work presents the effect of the annealing temperature on the fraction of austenite in the cast iron matrix. The annealed and non-annealed cast iron hardness is given. The work also proves that an increase in the temperature up to 580°C causes a drop in the cast iron hardness.
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