Vari Morph Cast Iron-A High IQ Material-Structure, Properties, Ultrasonic Control, Technology and Industrial Application.

Graphite formation should be strictly suppressed for the most abrasion resistant white cast irons, since austenite (γ)+graphite eutectic structure shows lower hardness and selectively wears thus deteriorates the abrasion resistance even though the austenite transform to hard phase such as martensite. On the other hand, a small amount of fine graphite is desired to distribute in rolls for hot steel mills to suppress the scoring. However, strong carbide formers such as Cr, V, Nb have been increasingly added to rolls, in order to crystallise more harder carbides. As γ+carbide eutectic grows, the residual liquid among eutectic cells becomes poor in carbide formers and rich in elements which promote graphite formation. Therefore an appropriate alloy design is essential for the hot steel milling rolls. In this study, the graphite formation mechanisms are discussed for chromium cast iron, high speed steel type cast iron and Ni hard type cast iron.

BACKGROUND: The paper discusses the issues of improving the quality of piston-type hydraulic machines. The base case is the mud pump. The service purpose of the mud pump is to supply mud. The main problem that occurs when operating hydraulic machines of this type is increased wear of the working surfaces of the cylinder sleeves. This is mainly due to the presence of fractions in the drilling mud, which have increased abrasive properties. To increase the durability of the assembly, high-chromium alloyed cast irons of the IChKh-22 type are used as a material for making the sleeve. However, these parts are expensive. It should also be noted that high-quality cast iron has worse foundry properties compared to other types of cast iron (for example, gray cast iron). AIM: Evaluation of the possibility of improving the quality of piston-type hydraulic machines by improving the design of the cylinder assembly. METHODS: To improve the quality of piston-type hydraulic machines, it is proposed to use gray cast iron, which is hardened by heating in contact with a mixture of oxides of alloying elements. Considering the fact that quality is a complex property, it is reasonable to evaluate it based on a comparison of both technical and economic aspects. The complex assessment was carried out using a differential method based on technical and economic indicators: tightness of the connection of the “sleeve-rod” pair, wear rate of the surface layer of the cylinder sleeve, strength, rigidity and cost. The tightness and wear were determined by calculation using experimental data on the properties of the hardened layer, and the strength and stiffness of the bushings were determined using the finite element method. RESULTS: The results obtained show that the proposed variant is not inferior to the basic one in terms of wear resistance and tightness, and is significantly more efficient in terms of cost. Analysis of the options was carried out without taking into account technological aspects such as processing performance and the percentage of defects. As a perspective for further research, these criteria should also be looked at. CONCLUSION: In the course of the research, it was found that the working part of the sleeve, which is made of alloy cast iron, can be replaced with modified gray cast iron. As a result of the assessment of the quality level, it was found that the resulting quality indicator for the proposed option is higher than for the basic one. Although the specific quality indicators characterizing the functional purpose for modified cast iron are somewhat lower, the economic effect of using such bushings is significantly higher than its counterpart. Thus, the resulting indicator characterizing the quality of bushings in general for modified gray cast iron significantly exceeds its analogues.

Conventional Fe-C-Si alloy cast iron shows good properties at low temperature but at high temperature its properties decrease very sharply. So, to protect this behaviour of cast iron, Si was replaced by Al, since both elements have similar graphitizing effect. In the present study, two types of cast iron, Fe-C-Si and Fe-C-Al, were cast in cold set resin bonded sand mould. After casting, the microstructures were studied using standard metallographic techniques. The wear tests were conducted using “CSM High Temperature Tribometer” following pin-on-disk method at 25 °C, 100 °C, 200 °C and 300 °C. The worn tracks were characterized using optical profilometer, SEM etc.. The results show that abrasive type wear was observed in both types of cast iron and always the Fe-C-Al cast has low wear rate compared to Fe-C-Si. However, after at 100 °C temperature, the wear resistance of Fe-C-Si cast iron starts to decrease whereas at lower temperature, it remains almost unchanged. The wear rates for Fe-C-Si alloy cast iron are 12.42, 16.51, 46.75 and 98.87x10-5mm3/N/m whereas the wear rates for Fe-C-Al cast iron are 3.32, 4.23, 4.40 and 8.15x10-5mm3/N/m at 25 °C, 100 °C, 200 °C and 300 °C, respectively.

A note on the effect of nodularization characteristics on the workability of quenchp-hardened and tempered cast irons

Microstructures and martensite transformation start (Ms) temperatures of the synthetic weld heataffected zone of two types of nodular graphite cast irons, FCD40 and FCD60, are investigated. The thermal cycles of the test pieces, 3 mm in diameter and 10 mm in length, are simulated to those of real arc welding; test pieces are rapidly heated to a temperature about 1100°C in 4 seconds, then cooled to room temperature. Implant cracking tests using smoothed 6 mm in diameter specimens FCD40 are also carried out with and without preheating.When the peak temperature of the specimens were made higher, the Ms temperature became lower; from about 300°C to below 200°C. Though two types of cast irons had different matrices at room temperature, the Ms temperatures of those were nearly same. This means that, in spite of very short holding time, the minimum carbon content of matrices of both irons become nearly equal, when they are heated to high temperature near melting point. This concept was proved from the results of the implant tests of FCD40 showing same critical strength of welds, about 28OMPa, and martensitic fracture structure as previous work for FCD50 and FCD60.

Since ductile cast iron was invented, cast iron has been used for various purposes. However, because of its poor corrosion resistance, the use of cast iron in corrosive environments was restricted. As pre-viously reported, the authors succeeded in obtaining a prominent protective film on steel by silicon impregnation (so-called siliconizing).In the present work, 3 kinds of specimens, i.e. nodular cast irons having ferrite and pearlite matrix, respectively, and gray cast iron, were siliconized by means of a mixed gas of silicon tetrachloride and oxygen free argon in accordance with the silicon impregnation of steel. The results obtained were summarized as follows.(1) Microscopic examination showed that porous films were formed on nodular cast iron with ferrite matrix, and particularly, on gray cast iron. On the contrary, when nodular cast iron with pearlite matrix was siliconized at a relatively high temperature for a short time, the film obtained had comparatively less pores in number.(2) Immersion tests of the siliconized cast irons in dilute sulfuric acid showed that the siliconized film protected the underlying cast iron core from the attack of acid though it was porous. Above all, the film which had been formed on nodular cast iron with pearlite matrix by siliconizing at a high temperature for a short time showed the best corrosion resistance.

Mechanical properties of cast irons are mainly determined by two factors of microstructures, graphite morphology and type of matrices. Both graphite morphology and matrices affect electromagnetic properties very complicatedly. The authors have investigated electromagnetic properties of flake graphite cast irons and ductile cast irons focusing on the their microstructures, and applied electromagnetic nondestructive evaluation method such as eddy current method, nonlinear eddy current method and DC potential drop method to characterize microstructures of various kind of cast irons. In this presentation, we review relationship between electromagnetic properties and microstructures. Issues discussed include graphite forms in fake graphite cast irons which is important to estimate damping and wear properties of flake graphite cast irons, ferrite and pearlite ratio in ductile cast irons which decides the hardness, and chill contents of both flake graphite cast irons and ductile cast irons. Finally, we discuss feasibilities of some applications of electromagnetic nondestructive evaluation methods to characterize graphite forms and matrices of cast irons.

A new efficient method of casting tubular billets by directional solidification without the use of a core is proposed making it possible to obtain a fine-grained dense structure of cast iron due to intensive onesided heat removal and excess supply to the solidification front of superheated liquid phase during the entire billet formation time in a metal water-cooled mold (crystallizer). It is shown that the method makes it possible to obtain a prescribed final cast iron structure by creating a certain cooling regime for castings outside the mold. In the positive effect of directional solidification of the melt inherited by iron a decisive role is played by the formation of a dense structure and a more dispersed carbide eutectic with a favorable carbide morphology, which determines the good cast iron wear resistance. The results of studies confirm that the new casting method provides production of workpieces with a prescribed phase composition and improved physical, mechanical, and operating properties. The effect is considered of various factors of the formation of workpieces from different types of cast iron: gray alloyed with lamellar graphite, high-strength and high-chromium, and also Niresist cast iron, on the structure, properties and service life of components for critical purposes of general, mining and oil refining engineering.

Two types of compacted vermicular graphite (CVG) cast iron having ferritic and pearlitic structures have been studied to determine the effects of CVG on fatigue strength, fatigue crack growth rate and fracture appearance of cast iron. The results obtained were compared with those of two types of spheroidal graphite (SG) cast iron (corresponding to JIS FCD) having ferritic and pearlitic structures. The significant conclusions obtained are as follows: The fatigue limit of the CVG cast iron was lower than that of the SG cast iron independent of matrix structure. This tendency was prominent for ferrite matrix. However, the fatigue limit ratio of the CVG cast iron was not less than that of the SG cast iron regardless the shape of graphite. The fatigue crack growth rate of the CVG cast iron was higher than that of the SG cast iron. This trend was significant for the CVG cast iron having ferritic matrix. This could be due to the fact that the fatigue crack propagation in the CVG cast iron occurs through a zig-zag path between graphites more than that in the SG cast iron when compared at the same level of Kmax.

ISO 185/JL/300 is a higher-tensile-strength gray cast iron that has a pearlitic matrix; it has a tensile strength of 300–400 MPa (44–58 ksi), when determined on test pieces machined from separately cast, 30 mm (1.2 in.) diameter test bars. It provides high strength while still maintaining good thermal conductivity compared with other types of cast iron. This grade approaches the maximum tensile strength attainable in gray cast iron. Applications therefore tend to be confined to those where thermal conductivity requirements in service preclude the use of one of the other higher-strength materials such as spheroidal graphite cast irons, which have inferior thermal properties. This datasheet provides information on composition, physical properties, and tensile properties. It also includes information on casting and heat treating. Filing Code: CI-82. Producer or source: International Organization for Standardization.

It is common knowledge that at low and ultra-low temperatures, many metals and alloys are prone to cold brittleness, which leads to the destruction of bridges, pipelines, gas-pumping compressors and other equipment. As such material, it is advisable to use high-strength, cold-resistant cast iron with nodular graphite (HCV). The importance of manufacturing technology development, properties research and implementation of cold-resistant high-strength cast iron is shown. The effect of heat treatment on its mechanical properties was studied. HF castings, compared to billets from steel casting and rolling, have a number of significant advantages. The cold resistance of structural steels does not exceed minus 40 °С. HF differs favorably from steel in terms of its casting properties, its lower cost (by 15–20 %), stronger wear resistance, higher corrosion resistance, and better machinability by cutting; lower HF density (by 8–10 %) allows to reduce the mass of parts compared to the mass of steel parts; the damping ability to extinguish vibration mechanisms arising during operation is much higher in HF than in steel. We performed a whole complex of robots on the specified topic and as a result developed technologies for obtaining unalloyed cold-resistant high-strength cast iron with spheroidal graphite – HHF – capable of working up to -80 °C; -100 °C; -150 °C, and also implemented for mass production of castings. HHF has a unique combination of physical, mechanical, operational and technological properties, namely: high strength and plasticity, high cold resistance (down to minus -100 °С, -150 °С), very high damping capacity (this is a very important factor for wind turbine parts); high corrosion resistance, manufacturability of castings during their production, as well as cheapness compared to other structural materials. This type of cast iron is an ideal structural material for responsible highly loaded parts of wind energy installations (WEE) in both northern and high-altitude versions. In order to develop and verify the effectiveness of the technology for obtaining HVC, numerous tests of HVC metal samples on mechanical properties at normal and subzero temperatures were carried out. At the same time, certain regularities were obtained, which are described in numerous publications on this subject. Prospects for development and fields of its use are described.

The aim of this work is to study the wear characteristics of different cast iron types which might be used as mould materials in glass blow molding. Wear testing rig was designed and developed to carry out the wear tests. Three types of gray cast iron with different chemical compositions were cast and heat treated, as well as samples taken (for comparison) from another two existing mould already being in use.Samples for wear testing were taken from the prepared materials and abraded against an automobile friction brake pads. Sliding velocity, friction pressure and contact time were taken as test variables. Weight loss of the tested samples was measured after conducting the wear tests at 600 & 800 0C.Cast iron with (2.98% C, 5.117% Si, and 1.39% Cu) showed the highest hardness in its as cast condition compared to the other types. It showed the best wear resistance after heat treatment (stress relief annealing).Results also showed that some of the tested materials gave a good wear resistance at low temperature (up to 600 0C) but they lost their resistance at high temperature (up to 800 0C). It was concluded that hardness is not the only parameter that controls the wear resistance at high temperature.

Superior wear resistance property of cast iron coatings is strongly linked to their microstructure. Graphite formation in plasma sprayed cast iron deposit is the main reason for this distinct phenomenon owing to its self-lubricant property. Since solidification rate affects graphite formation, optimization of spray conditions such as substrate temperature, chamber pressure, particle size and spray distance are required to slow down the solidification rate. The adhesion property of cast iron coating depends strongly on the adhesive strength between the first deposited layer and the substrate. It is important to improve the adhesive strength of splats by optimization of spray parameters. In this paper, cast iron splats were sprayed on aluminum substrate by plasma spray method using high Si and Al cast iron powders in Ar atmosphere. The effect of particle size and spray distance on splat microstructure (including graphite distribution) and its adhesive strength has been investigated. A correlation between microstructure and solidification rate was also introduced. Spraying by using large particle size leads to an increase in the number fraction of disk splats and a decrease in the splat’s adhesive strength. In contrast, the number fraction of star-shaped splats and their adhesive strength increase by spraying using small particle size. Longer spray distances lead to a decrease in number fraction of disk splats and their adhesive strength. The rear-side observation of cast iron splats sprayed with different spray distances show no distinct difference.

Quenching strain and crack have an intimate relation with internal stress originate from quenching. Experiments were carried out to investigate this relation in cast iron treated by ordinary quenching and high frequency induction heating. The specimens used were flake graphite, and spheroidal graphite cast iron, which contain the typical form of graphite in cast iron, and 0.5%C steel. This relation changes considerably according to the quenching method and the form of graphite in cast iron. Strain and residual stress in specimens treated by ordinary quenching were found passably larger than that in induction heated specimens. Nodular graphite cast iron shows a tendency similar to 0.5%C steel on the stress distribution and strain, but flake graphite cast-iron shows a different tendency from both of them. As a characteristic in stress distribution and its strain of flake graphite cast iron different from the case of nodular graphite cast iron and steel, the value of compressive stress on the tangential direction near the surface is rather small, in spite of the large value of the expansion of the outer diameter, while that of the inner diameter is small, that is, the relative difference of the two values is larger than in the case of nodular graphite cast iron and steel.

Ultrasonic longitudinal wave propagation is studied in out-of-autoclave (OoA) carbon fiber–reinforced polymer composite material with varying levels of porosity contents. A combination of cure pressures and a solvent is used to produce specimens with void contents in the range of 0% to 22%. Ultrasonic measurements are made in through-transmission mode, and the data is processed to study various aspects of wave interaction with porosity in OoA specimens. The specimens with a wide range of void contents have enabled the study of broader trends of ultrasonic center frequency, wave velocity, and attenuation with respect to porosity. Results show ultrasonic center frequency and wave velocity are decreased linearly as the void content increases. The relationship of ultrasonic wave attenuation can be approximated by a logarithmic relationship when considering the full range of void content studied. Strength measurements of specimens with varying void contents are made using the flatwise tensile (FWT) test. It is observed that the strength rapidly decreases with increasing porosity. Correlations made between FWT strength, ultrasonic wave velocity, and attenuation are best described by logarithmic relationships. The data shows a potential for inferring strength knockdowns due to the presence of porosity based on ultrasonic measurements.