球状黒鉛鋳鉄の再現熱影響部組織と溶接部強度

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

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.

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.

Influence of alloying elements and its effect on austempering of compacted graphite iron – A review

Cast iron, whose structure simultaneously contains graphite precipitates in various forms, with controlled proportions of individual forms, has been named "Vari-Morph" (VM) cast iron by the authors. The authors have been researching the properties of such cast iron for many years, and the results are being published successively. This new type of cast iron, not included in national (Polish) or European standards, is intended as a material for special-purpose castings. These castings have unique requirements for a set of properties: physical, mechanical, and functional. VM cast iron is characterized by a set of properties that cannot be achieved when the graphite is uniform in shape. The desired properties of VM cast iron are achieved by controlling the morphology of graphite precipitates and the proportion of individual forms in the structure, rather than by changing the matrix. To quantitatively describe graphite precipitates, a proprietary method for determining the graphite shape indicator (fK) was developed. Graphite precipitate analysis is performed by scanning a microscopic image of the metallographic specimen, and then using Tescan Imaging Software (Tescan ESSENCE™) Unified Control for Imaging and Analysis, each precipitate is described using surface metrology parameters. The final value of the graphite shape indicator (fK) is calculated as a weighted average of all precipitates present in the analysis field. Empirical relationships between the fK indicator and a selected group of physical, mechanical, and functional properties of VM cast iron were determined. Studies have demonstrated a very well-correlated relationship between the fK indicator in VM cast iron and ultrasonic wave velocity (CL). The relationship CL = f(fk) is characterized by a very high correlation coefficient of R > 0.90. In previous publications, the authors presented the relationships between the fK indicator and physical properties such as thermal conductivity (λ), specific density (ρ), strength (Rm), elongation (A5), index quality (IQ), and functional properties such as low-cycle mechanical fatigue resistance (Zc), thermal fatigue resistance (N), and cast iron tightness (H) as functions of the fK index. The study concerned VM cast iron with a ferritic matrix. This work contains new empirical relationships that extend previous studies. The newly developed relationships replace the fk shape indicator with the velocity of the ultrasonic wave determined in cast iron with a specific fK indicator value. This resulted in a number of practical dependencies, including: λ = f(CL); ρ = f(CL); ED = f(CL); Rm = f(CL); A5 = f(CL); IQ = f(CL); N = f(CL); Zc = f(CL); H = f(CL). These relationships allow us to measure the wave velocity in a Vari Morph iron casting (with various forms of graphite) and determine a number of characteristics and properties of the material/iron from which the casting was made. It is possible to assess the suitability of a casting with a specific structure for operation under selected conditions.

As production of compacted-graphite irons (CG irons) has continued to rise, the use of denodularising (antispheroidising) elements (Ti, Al, Sb, Sn, etc) has led to the build-up of these deleterious elements in the compacted graphite cast iron returns (CG returns). Can this be a problem for the future of nodular and compacted graphite irons production? Can these two types of cast irons be produced in the same foundry? These are the questions this paper tries to answer.

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.

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.

The phase transformation temperature plays an important role in the design, production and heat treatment process of steels. In the present work, an improved version of the gradient-boosting method LightGBM has been utilized to study the influencing factors of the four phase transformation temperatures, namely Ac1, Ac3, the martensite transformation start (MS) temperature and the bainitic transformation start (BS) temperature. The effects of the alloying element were discussed in detail by comparing their influencing mechanisms on different phase transformation temperatures. The training accuracy was significantly improved by further introducing appropriate features related to atomic parameters. The melting temperature and coefficient of linear thermal expansion of the pure metals corresponding to the alloying elements, atomic Waber-Cromer pseudopotential radii and valence electron number were the top four among the eighteen atomic parameters used to improve the trained model performance. The training and prediction processes were analyzed using a partial dependence plot (PDP) and Shapley additive explanation (SHAP) methods to reveal the relationships between the features and phase transformation temperature.

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.

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.

We have investigated the martensite transformation phenomena of a Cr-Ni type weld metal, especially the effects of stress and plastic strain that exist before the martensite transformation start. Tensile specimens machined from the weld metal were firstly heated up to 800 °C to austenitize the specimens and then cooled down. During the cooling, we applied stress and plastic strain before the martensite transformation starts. The results show that the stress increases the Ms temperature, while the plastic strain decreases the Ms temperature. In addition, the transformation-induced plasticity was also investigated. Finite element method (FEM) analysis was conducted considering these effects, and the results show that these effects on the residual stress and the weld distortion are considerably large. The FEM analysis shows that the compressive residual stress in the weld metal is likely to be decreased by the transformation-induced plasticity. We also conducted hydrogen diffusion analysis for the case that the retained austenite exists in the weld metal by varying the Ms temperature in order to consider the appropriate time period to keep a cold cracking test specimen before the crack observation.

In recent years, a lot of investigations have been focused on ferromagnetic shape memory alloys (FSMAS), such as Ni2MnGa, FePd, CoNi and FeNiCoTi [1–4], due to their large magnetic-field induced strain (MFIS) and high response frequency. Of the above alloys Ni Mn Ga alloy is the only known Heusler alloy exhibiting thermal martensitic phase transformation. It is reported up to now that a maximum 6% of MFIS has been obtained in Ni49.8Mn28.5Ga21.7 single crystal by applying a constant 2 MPa compression stress [5]. However, few results have been reported about the temperature dependence of MFIS in NiMnGa alloy. The purpose of the present paper is to measure the MFIS along the [110] direction of Ni50.5Mn26.2Ga23.4 single crystal at different temperatures. It is interesting to find that the MFIS between the temperature of Ms and Mf is larger than the MFIS below Mf. The specimen used in this study was cut from a bulk single crystal with composition of Ni50.5Mn26.2Ga23.4 (at%). The single crystal was grown in the [110] direction according to the cubic parent phase using a Czochralski instrument with a cold crucible system. This single crystal was annealed at 850 ◦C for 12 h, then quenched into ice water to obtain high L21 ordering [6]. An orientation along the specimen length direction was confirmed to be [110] by Laue X-ray diffraction. The dimensions of specimens for MFIS measurements were 2 mm × 4 mm × 6 mm. The magnetic field induced strain was measured by a strain-gauge attached to the sample which was placed in a furnace between the electromagnets. The external magnetic field was applied parallel to the [110] direction of the sample. The sample was cooled from high temperature to a temperature far below Mf. Then the MFIS was measured at the temperatures of interest. The phase transformation temperatures were determined by a low field ac susceptility method. Fig. 1 shows the χ–T curve of the experimental alloy. It can be seen that, the martensitic transformation start temperature (Ms) and finish temperature (Mf) are 279 K and 274 K respectively. And the reverse transformation temperature (TA) is 283 K. The Curie temperature (Tc) is about 370 K higher than the martensitic transformation and reverse transformation temperatures indicating that both autensite and martensite are ferromagnetic in this alloy. It is seen that the value of Ms–Mf is very small which means that thermal martensitic transformation happens quickly. Fig. 2 shows a typical curve of the MFIS measured along the [110] direction in a reverse magnetic field at 244 K below Mf. It was found that the sample shrinks in the external magnetic field. A small MFIS, about −600 ppm, was obtained with an axial magnetic field up to 2 T. Further, it can been seen the MFIS is reversible and reaches saturation at about 0.8 T. All strain recovers after returning the field to zero. Similar MFIS curves are obtained irrespective of the direction of the applied magnetic field. Fig. 3 depicts the magnetic field induced strains as a function of magnetic field in the temperature range between 244 K and 276 K. According to the different phase states at various temperatures, the experimental results can be divided into two temperature stages: Stage I. Full martensite state which is below Mf. For the specimens tested at 247 K, 255 K and 263 K, the saturated MFIS is only−600 ppm. And with the increasing of temperature only an increase of 100 ppm is observed. In this stage, all the MFIS is attributed to the motion of martensite twin boundaries caused by the magnetic field because only martensite phase exists. It is known that [110] is the hard axis of magnetization for NiMnGa alloy. According to R.C. O’Handley’s model [6] the experimental Ni Mn Ga alloy has weak anisotropy. This means that only a weak driving force could be provided on the twin boundaries regardless of the strength of applied field, which leads to very a small MFIS in the full martensite phase. Stage II. Parent phase and martensite co-exist which is between Ms and Mf. For the specimens tested at 275 K, the strain produced is as large as −900 ppm, meanwhile, of the total strain about −300 ppm strain does not recover when the magnetic field is removed. At 276 K, the saturated MFIS jumps abruptly to −1700 ppm, which is nearly three times as large as that of the specimen measured below Mf, and a greater irreversible MFIS, nearly −1200 ppm, is observed. Clearly, the strain caused by thermal phase transformation plays an important role in the increase of this MFIS. Based on the analysis of experimental results, the temperature dependences of saturated MFIS and the strain recovery

Laterite steel is a steel with a low nickel content which is between 1 - 4.5 percent. Generally, the nickel content in laterite steel which was tried to be developed by LIPI ranged from 1.5 to 4.5 percent. The type of laterite steel developed from laterite ore is NPI (Nickel Pig Iron), a type of cast iron that has a high hardness value and optimal toughness. This material is widely used for grinding balls or Hard-Liner materials for crusher or grinder equipment. In the research of the heat treatment process, Carburization of Austempering uses laterite steel with Ni and Ni-Cr alloys. Where this study uses parameters of heating temperature in the Austenisasi temperature of 950 oC and Austempering temperature of 400 oC with the same holding time of 1 hour. In this study also used a variation of cooling media (quenching), namely angina fan, water and left in the furnace. Laterite steel which has been processed by carburization Austempering will be tested by testing hardness, impact, metallography. From the test results obtained test data where, the highest value of hardness is found in steel sample 2 (Ni-Cr), which cooling using a fan with a value of 63.6 HRC with the phase produced martensite. And the highest impact value is found in the sample steel 3 (Ni) which cools in the furnace with an impact value of 38J and the phase formed is bainite.

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.