Strength Of Gray Cast Iron Research Articles

Laser‐Based Directed Energy Deposition Remanufacturing of Gray Cast Iron using Stainless Steel 316L and Inconel 625 Filler Materials

Directed energy deposition (DED) is identified as an ideal candidate for restoring damaged or worn cast iron components such as agricultural engine blocks, housings, and manifolds. While this laser‐based process offers superior control of the heat input compared to traditional arc‐based repair, gaseous porosity and brittle intermetallic structures reduce the strength and ductility of the fusion zone. Varying combinations of Fe–Ni–Cr alloys have found success in remanufacturing cast iron using laser‐based DED, but little attention has been given to the consequence of filler material composition and form, that is, wire versus powder. This study quantifies structural characteristics in cast iron repairs and offers microstructural and process‐specific insights to support these observations. With appropriate thermal conditions, up to 98.7% of the original tensile strength of gray cast iron may be achieved. These results point toward superior gray cast iron restoration using tunable laser‐based DED.

Estimation of Anomalous Portion in Gray Cast Iron Using Non-Contacting Electromagnetic Sensor

The gray cast iron is used in many mechanical parts due to its excellent damping force, wear resistance and castability. Inspection of the tensile strength of this cast iron is important for quality assurance of the machine products. The areas of reduced tensile strength in the cast iron are defined as abnormal areas in the cast iron. The tensile strength of gray cast iron is affected by its microstructure. The gray cast irons with low tensile strength contain a high percentage of ferrite and a low percentage of pearlite. The electromagnetic properties of the cast iron are affected by the content of these components. In this paper, an electromagnetic sensor is proposed in which the tensile strength of the gray cast iron is measured from changes in these electromagnetic properties. The electromagnetic FEM analysis using a play model method and the verification experiment show that the abnormal part of the tensile strength can be estimated from the difference in the hysteresis magnetic curve and conductivity in the cast iron.

Effect of Ultrasonic Treatment on Microstructure and Properties of Gray Cast Iron

The effect of ultrasonic treatment on the microstructure and properties of gray cast iron was studied. The samples were analyzed by metallographic microscope, scanning electron microscope, Brinell hardness tester, electronic universal testing machine, etc. The results showed that ultrasonic treatment could improve the pearlite content in the microstructure. After ultrasonic treatment, the tensile strength of gray cast iron can be improved to 266 MPa, which is 11.60% higher than that of the samples without ultrasonic treatment. Ultrasonic treatment can refine the size of graphite, which can reduce the stress concentration. In addition, the pearlite lamellar spacing can also be reduced, which is the main reason for improving the mechanical properties of gray iron.

Evolution of microstructure and high temperature tensile strength of gray cast iron HT250: The role of molybdenum

The present work investigated the influence of molybdenum (Mo) content on the microstructure and high temperature tensile strength (HTTS) of gray cast iron (GCI) to achieve improvement of the HTTS of GCI brake drum for heavy-duty trucks and extension of their service life. The specimens of GCI with Mo (0.024%, 0.22%, 0.51%, 0.8%) have been prepared by smelting in a 25 kg vacuum induction furnace and casting in a standard mold. The microstructure was observed by scanning electron microscopy and optical microscopy, while physical properties tested by microcomputer-controlled testing machine and micro hardness tester. The results show that increasing the Mo content from 0.024% to 0.8%, the length of graphite flake decreased from 400 μm to 288 μm; the pearlite interlayer spacing decreased from an average of 619 nm–439 nm. However, the pearlite content also decreased with the increase of the Mo content. A portion of the Mo is in solution in the matrix; this contributes to solution strengthening of the matrix. The remainder of the Mo precipitates in the austenite grains, or the grain boundaries, as carbides. This results in the refining of the pearlite grains. Eutectic cell density increased from 217 cm−2 to 286 cm−2. Both room temperature tensile strength and HTTS increased with increasing Mo content. The findings suggest adding Mo to GCI is an effective way to improve the microstructure and increase its HTTS.

Study of Factors Affecting Tensile Strength of Grey Cast Iron

Tensile strength of a material is the capacity of material to withstand tensile force without failure. Tensile strength is important mechanical property of material which gives direction to use it for proposed application safely. It is very important parameter considered in designing sound product. Grey cast iron carries properties like high compressive strength, castable, good machinability, good abrasion resistance, high thermal conductivity, resist to expand under high temperature. Tensile strength of grey cast depends mainly on carbon content, steel scrap % used, inoculation, graphite morphology, cooling time. Present paper summarizes study of factors affecting tensile strength of grey cast iron. With the study of factors affecting the tensile strength of cast iron it is very helpful to achieve required tensile strength by controlling the factors affecting strength of the material. While studying and experimenting on the behavior of tensile strength, clear idea comes into the picture how the strength is affected.

The Influence of Undercooling ΔT on the Structure and Tensile Strength of Grey Cast Iron.

Inoculation of cast iron has become a commonly used metallurgical process, which is carried out in a foundry in order to improve the mechanical properties of utility alloys. It consists in changing the physicochemical state of the melted alloy. This change is caused by the introduction of cast iron with a low ability to nucleate graphite, shortly before pouring a small mass of the substance—an inoculant that increases the number of active nuclei. It is also justified that the literature often connects an increase in the tensile strength UTS of the inoculated grey cast iron, with changes in the characteristics of the particles of graphite. However, in strongly hypoeutectic cast iron, in which a large number of primary austenite grains crystallize, the interdendritic distribution of graphite is usually the result. It also follows that the nature of the graphite precipitates is determined by the mutual relations between the interfacial distances in eutectic grains and the interdendritic distances in the grains of primary austenite occurring in the Fe–C alloys. The article presents the influence of the inoculant on the characteristics of the precipitation of primary austenite grains in relation to the sulphur content in grey cast iron with flake graphite. The study also showed that primary grains in grey cast iron have a great influence on mechanical properties, such as the tensile strength UTS. In this case, the key is to know the value of the degree of undercooling ΔT. The type of inoculant used affects the ΔT value. The study related the number of N primary austenite grains with the degree of undercooling ΔT and the tensile strength UTS with the number of primary austenite N grains.

New Approach to an Analytical Prediction of the Strength of Gray Cast Iron

New Approach to an Analytical Prediction of the Strength of Gray Cast Iron

Effect of alloying elements W, Ti, Sn on microstructure and mechanical properties of gray iron 220

Experiments were carried out to observe the variation in microstructure and mechanical properties of gray cast iron by adding pearlite promoting alloying elements such as Ti, Sn and W. Results show that adding Sn, Ti, and W with different concentrations improve the microstructure, Brinell hardness and tensile strength of gray cast iron. With the increase of alloying element concentration, the average graphite length and graphite content increase linearly. At the same time, average cell size and the maximum graphite length also decrease linearly. Brinell hardness and tensile strength of gray cast iron also increase with an increase in alloying elements contents, and attain the maximum when Ti = 0.561%, Sn = 0.561% and W = 0.945%. However, at higher concentrations of Ti = 0.810%, Sn = 0.631% and W = 1.351%, the tensile strength decreases from 333 MPa to 297 MPa and the Brinell hardness decreases from 248 HB to 225 HB. The decrease in tensile strength and Brinell hardness at the higher concentration level is attributed to the formation of coarse and thick graphite flakes.

An Investigation of Effect of Tin (Sn) on Microstructures and Mechanical Properties of Gray Cast Iron

As the tensile strength of gray cast iron is low, it is tried to increase tensile strength by testing various alloying elements. The most preferred of these alloying elements was the copper element. However, it is known that copper increases both hardness and tensile strength by enhancing perlite ratio in microstructure. On the other hand, when tin (Sn) is used in trace amounts compared to copper, it has similar effects on hardness and tensile strength of cast iron. In this study, adding tin element of 0,03-0,06-0,09-0,12-0,15 % by weight in gray cast iron, its effect on tensile strength was investigated and the appearance of the fracture surfaces was examined. It was compared with two different gray cast irons containing 0.4% copper element and free of alloying elements. According to the tensile strength results, the highest tensile strength was observed to be 195 N / mm2 in the specimen number 6 containing 0,12% Sn. The lowest tensile strength was determined as 157 N / mm2 in the specimen number 1 which did not contain alloying elements. In SEM (Scanning Electron Microscopy) images, it is seen that the samples generally exhibit a brittle rupture behaviour. In some of the specimens with the addition of tin and copper, regional ductile rupture behaviours were observed.

Поліпшення механічних характеристик сірих чавунів термообробкою та обґрунтування її параметрів

The article discusses the technology of heat treatment of gray cast irons in order to improve their mechanical characteristics by implementing a bainitic transformation of the metal matrix. It is proposed to use the environmentally safe technology of hardening “in two waters” to start the process of transformation of austenite of a gray cast iron matrix into bainite without using environmentally harmful baths with molten alloys or salts, and further complete or partial isothermal decomposition of austenite in air furnaces. This not only improves the environmental performance of the process, but also significantly reduces the cost of it. The definition of rational parameters of the process of heat treatment of gray cast irons was carried out using the method of planning and implementing a multifactor experiment. The adequacy of the results obtained as a result of measurements with the implementation of parallel experiments was checked using Student's criterion and satisfied the requirements, and also allowed to discard insignificant members of the regression equation. The regression model of the influence of process parameters on the hardness of thermally hardened cast iron was tested using the Fisher criterion, which showed its adequacy. Experimental studies to determine the factors that determine the strength of gray cast iron hardened to bainite made it possible to establish rational temporal parameters of heat treatment. It is shown that the exposure time in the furnace at 850 °C before cooling and the exposure time in the furnace with a temperature of 400 °C in the process of austenite decomposition should be limited to 30 minutes. The implementation of heat treatment technology with certain parameters to improve the quality of casting, mass produced at the plants of the region, allowed to increase the compressive strength of cast iron by 1.5 times, the surface hardness by 2 times, and the brand of cast iron to increase from SCH20 to SCH25—SCH30. At the same time, it was possible to reduce emissions of vapors of salts, metals and other products of the interaction of melts with the atmosphere.

Increasing the strength of grey cast iron by introducing of dispersed additives into the melt

The basic mechanisms of increasing the strength of alloys, including methods through the introduction of the melt coherent and incoherent crystallizing structural components of the alloy dispersed particles were considered. New data on the influence of ultrafine particles obtained from grinding wastes of tool steels (metal abrasive slime) and proposed as modifying additives on the structure and strength properties of gray cast iron are presented. The prevailing influence of metal component of metal-abrasive sludge on the properties of cast iron is revealed. The optimum amount of additives-modifiers were defined. The increase in the strength of cast iron mid 20 as a result of modification is equal up to 20%

Relation between the Hardness and the Strength of Gray Cast Iron with Allowance for the Structural Parameters

The factors that affect the relation between ultimate tensile strength σu and hardness HB of gray cast iron with flaked graphite are studied. The scatter of the ultimate tensile strengths at a given hardness is shown to be caused by one of the primary structure parameters, namely, the volume fraction of primary austenite dendritic crystals. The dependences derived in this work can be used to increase the accuracy of a rapid estimation of the quality of cast iron ingots.

Effect of Casting Skin Condition on Fatigue Strength of Gray Cast Iron

The microstructure around the casting skin of cast iron changes according to conditions in the mold, wash material and cooling speed. When a self-hardened mold was used, a matrix microstructure containing all pearlite was obtained in the casting skin. When a greensand mold was used, the matrix microstructure was a mixture of pearlite and ferrite. In this study, tests were conducted to determine the influence of a casting skin on fatigue strength in gray cast iron with one sample containing a fully pearlitic matrix compared with another having a ferrite–pearlite mixture. For comparison, fatigue tests were also conducted on the sample with a pearlitic matrix taken from inside the sample and machined. The surface roughness of the test piece with casting skin was rougher than the test piece with the machined surface. The fatigue strength of the test piece with coarser surface roughness was lower. In a smaller eutectic cell, fatigue strength became higher. The fracture path was observed to be along the interface of graphite. It was considered that the fracture propagation was suppressed by smaller eutectic cells. On the other hand, a little ferrite generated in a casting skin made the fatigue strength lower.

Study on the Influences on Microstructure and Properties of High-Strength Grey Cast Iron in Addition to Alloying Elements Nb

The increase of the strength of gray cast iron is mainly depended on alloying. However, with the improvement of strength, its processing performance will always decrease. So three different gray cast irons are studied in this experiment, including adding 0.1% Nb elements, adding 0.2% Nb elements and adding 0.3% Nb elements, to investigate the Nbs effect to the mechanical performance of gray cast iron, we adopt Dynamic Strain Amplifier to measure cutting force to evaluate processing performance, use Optical Microscope and Electron Microscopy observe each samples organization, explains the relationship between Nbs content and the mechanical and processing performance of gray cast iron from micro-level. Finally, we draw the conclusion: when the Nb comes to 0.3 percent, the appearance of E-type graphite and Nb carbide durum granular will greatly decrease its processing performance.

Fracture behavior and microstructure of steel fiber reinforced cast iron

In this study, improvement of fracture toughness and strength of gray cast iron by reinforcing steel fiber was investigated. Three point bend specimens were used to calculate the flexural strength and fracture toughness. Fracture toughness of the reinforced cast iron with two distinct volume fraction (Vf = 0.05 and 0.08) were calculated by compliance method and J-integral method using single specimen technique. The study shows that fiber reinforced composite has higher fracture toughness and flexural strength than cast iron without reinforcement. Also, fracture toughness increases with increasing volume fraction of reinforcement. Optical and scanning electron microcopy (SEM) analyses were used to examine the microstructure and fracture surface. It is noted that the carbon diffuses from gray cast iron to steel fiber and graphite free transition regions with high hardness were observed due to the carbon diffusion.

Effect of semi-solid processing on solidification microstructure and mechanical properties of gray cast iron

The processing of metals in the semi-solid state is becoming an innovative technology for the production of globular structure and high quality cast parts. This research is directed towards studying the effect of semi-solid processing (using cooling plate technique) on the microstructure and the strength of gray cast iron. The charge material used for all trials was hypoeutectic gray cast iron with 3.59% carbon equivalent. The results indicated that by increasing fraction of solid microstructure becomes finer and more globular. Increasing primary fraction of solid causes an increment of undercooling and changes graphite morphology. Tensile strength of semi-solid processed gray cast iron is relatively high compared with ordinary one. The values of both the tensile strength and the elongation depend on the fraction of solid. It is found that graphite morphology (size and type), primary solid agglomeration and cutting graphite network have a large influence on both the properties in semi-solid processing. The total fracture strength is observed to depend on the graphite morphology as well as the matrix contribution that mainly depends on fraction of solid. Increasing fraction of solid increases hardness values, which is attributed to the homogenous structure by semi-solid processing.

Investigation of microstructure and mechanical properties of steel fibre–cast iron composites

The aim of the present experimental study was to investigate improvement of the toughness and strength of grey cast iron by reinforcing with steel fibres. The carbon content of the steel fibres was chosen to be sufficiently low that graphite flakes behaving as cracks were removed by carbon diffusion from the cast iron to the steel fibres during the solidification and cooling stages. To produce a graphite free matrix, steel fibres with optimum carbon content were used and the reinforced composite structure was cast under controlled casting conditions and fibre orientation. Three point bend test specimens were manufactured from steel fibre reinforced and unreinforced flake graphite cast iron and then normalising heat treatments were applied to the specimens at temperatures of 800 and 850°C. The fracture toughness and strength properties of the steel fibre reinforced material were found to be much better than those of unreinforced cast iron. The microstructures of the composite at the fibre–matrix transition zone were examined.

Evaluation of the Mechanical Behaviour of Grey Cast Iron by Means of the Wedge-penetration Test

The maximum load in a wedge-penetration test is used to obtain the tensile strength of grey cast iron. This strength is internationally employed to classify the quality of these materials. In the present work, it is shown that a characteristic force-displacement curve can be associated with either the wedge-penetration test or the tensile test. This curve reveals a similar behaviour of the material during both tests. The newly-defined curve could be the basis of an easier and cheaper method to evaluate the fracture development of grey cast iron.

Accurate Evaluation of the Mechanical Properties of Grey Cast Iron

AbstractGrey cast iron has been regarded, in some circles, as being brittle, low in reliability and one where the usual design equations cannot be applied. The reason is usually attributed to the presence of randomly distributed graphite flakes. This presentation discusses, both experimentally and theoretically, the notch strength, bending strength, and the scattering of tensile strength of grey cast iron, and suggests a new approach based on plasticity theory for the accurate evaluation of these characteristics. Experiments showed that grey iron has a very low notch sensitivity in circumferentially notched bars, but that strength decreases in edge-notched plates. At the temperature of liquid nitrogen, notch sensitivity is very high. In ductile iron, strength increases in notched specimens. These results have been interpreted by the stress distribution, taking into account non-elastic stress/strain behaviour, and using a fracture criteria with an over-stressed depth, δ· The δ is a necessary region for fra...

Bending Strength of Gray Cast Iron

Abstract An experimental and theoretical study was made on the influence of the dimensions and geometry of cross sections on the bending strength of gray cast iron. The experiments revealed that the bending strength varies with specimen height, with higher bending strengths being recorded for smaller heights. This is explained by a region under the beam surface where the stress exceeds the tensile strength of the material. This overstressed depth is about 3 mm in 20 to 30 mm high beams and smaller in thinner beams. The geometry dependence of bending strength is caused by non-linearity of the stress-strain curve. Numerical simulation by the fracture criterion with a constant overstressed depth showed that the bending strength of round bars is 10% higher than that of rectangular beams. In T cross sections, the influence of the section geometry is more marked. The experiments agreed well with the calculations.