Al- and Al/Zn-enriched layers containing intermetallic phases were deposited on the Mg substrate by heating the Mg specimens in contact with the powdered materials in a vacuum furnace. The Al-enriched surface layers were produced using Al powder, whereas the Al/Znenriched layers were obtained from an 80 wt.% Al + 20 wt.% Zn powder mixture. The microstructure and composition of the layers were analyzed by optical microscopy, scanning electron microscopy and X-ray diffraction. The results showed that the Al-enriched layer comprised an Mg17Al12 intermetallic phase and a solid solution of Al in Mg. The layer obtained from the Al+Zn powder mixture was composed of Mg-Al-Zn intermetalic phases and a solid solution of Al and Zn in Mg. Adding 20% of Zn into the Al powder resulted in the formation of a considerably thicker layer. Moreover, the hardness of the surface layers was much higher than that of the Mg substrate.
Mg-0.5Si-xSn (x=0.95, 2.9, 5.02wt.%) alloys were cast and extruded at 593K (320 ºC) with an extrusion ratio of 25. The microstructure and mechanical properties of as-cast and extruded test alloys were investigated by OM, SEM, XRD and tensile tests. The experimental results indicate that the microstructure of the Mg-0.5Si-xSn alloys consists of primary α-Mg dendrites and an interdendritic eutectic containing α-Mg, Mg2Si and Mg2Sn. There is no coarse primary Mg2Si phase in the test alloys due to low Si content. With the increase in the Sn content, the Mg2Si phase was refined. The shape of Mg2Si phase was changed from branch to short bar, and the size of them were reduced. The ultimate tensile strength and yield strength of Mg-0.52Si-2.9Sn alloy at the temperature of 473K (200 ºC) reach 133MPa and 112MPa respectively. Refined eutectic Mg2Si phase and dispersed Mg2Sn phase with good elevated temperature stability are beneficial to improve the elevated temperature performance of the alloys. However, with the excess addition of Sn, large block-like Mg2Sn appears around the grain boundary leading to lower mechanical properties.
Dispersion hardening, as the main heat treatment of silumins having additions of copper and magnesium, results in considerable increase of tensile strength and hardness, with simultaneous decrease of ductility of the alloy. In the paper is presented an attempt of introduction of heat treatment operation consisting in homogenizing treatment prior operation of the dispersion hardening, to minimize negative effects of the T6 heat treatment on plastic properties of hypereutectoidal AlSi17CuNiMg alloy. Tests of the mechanical properties were performed on a test pieces poured in standardized metal moulds. Parameters of different variants of the heat treatment, i.e. temperature and time of soaking for individual operations were selected basing on the ATD (Thermal Derivation Analysis) diagram and analysis of literature. The homogenizing treatment significantly improves ductility of the alloy, resulting in a threefold increase of the elongation and more than fourfold increase of the impact strength in comparison with initial state of the alloy. Moreover, the hardness and the tensile strength (Rm) of the alloy decrease considerably. On the other hand, combination of the homogenizing and dispersion hardening enables increase of elongation with about 40%, and increase of the impact strength with about 25%, comparing with these values after the T6 treatment, maintaining high hardness and slight increase of the tensile strength, comparing with the alloy after the dispersion hardening
This article discusses the influence of Tungsten Inert Gas (TIG) surfacing of duplex cast steel on its hardness and structure. The samples of 24Cr-5Ni-2.5Mo ferritic-austenitic cast steel were subjected to single-overlay processes with the use of solid wire having the chemical composition similar to that of the duplex cast steel. As a result of the surfacing, the welds were obtained that had no welding imperfections with a smooth transition to the base material. In the test without the heat treatment, directly below the fusion line, we observe a ferrite band with a width of approximately 200 m without visible austenite areas. Some of the samples were then solution treated (1060°C). Both variants, without and after solution heat treatment, were subjected to testing. Significant changes in the microstructure of the joint were observed after the heat treatment process (heat affected zone and weld microstructure changes). In both areas, an increase in the austenite volume fraction after solution heat treatment was observed. Changes in the microhardness of the ferrite in the HAZ area directly below the fusion line were also observed.
In earlier works were described trends in the production of tools for die casting (hot work). Almost the entire set of issues dealt with may seem insignificant when incompletely assembled acceptance of the material and the associated risks of processing a material with an inappropriate structure, leading to a very early defect of the die. Therefore, further work will focus particularly on identifying the causes of thermal cracks and preventing a suitable choice of acceptance criteria conditions and heat treatment.
Effects of solution treatment on room temperature mechanical properties were studied in cast AZ91 (Mg-9%Al-1%Zn-0.2%Mn) and AZ91-0.5%Ca alloys. In as-cast state, the Ca addition contributed to the suppression of discontinuous β phase precipitation and the formation of Al2Ca phase. After solution treatment, the AZ91 alloy had only a small amount of Al8Mn5 particles, while β and Al2Ca phases were still present in the Ca-containing alloy. In as-cast state, the AZ91-0.5%Ca alloy showed better yield strength and hardness than the AZ91 alloy. The solution treatment increased the elongation in both alloys, which eventually led to the increase in ultimate tensile strength. The solution treatment resulted in a marked decrease in yield strength and hardness in the AZ91 alloy, whereas the decrements in those values were relatively negligible in the Ca-containing alloy due to the residual phases and solution hardening effect of Ca.
The work presents experiment results from the area of copper casting technology and chosen examples of alloyed copper. At present, copper casting technology is applied in many branches of industrial manufacturing, especially in the sector of construction, communications, arms and power engineering. Alloyed copper, containing slight additions of different elements and having special physio-chemical properties, is used in a special range of applications. Copper technology and alloyed copper analyses have been presented, these materials being used for cast manufacturing for power engineering. The quality of casts has been assessed, based on their microstructure analysis, chemical content and the cast properties. During the research, special deoxidizing and modifying agents were applied for copper and chosen examples of alloyed copper; also exemplary samples were tested with the help of metallographic analysis, electrical conductivity and gaseous impurities research.
This paper describes the possibility of using very short periods of solution annealing in the heat treatment of unmodified hypoeutectic silumin alloy AlSi7Mg0,3 casted by method of casting with crystallization under pressure with forced convection (direct squeeze casting process). Castings prepared at different casting parameters were subjected to special heat treatment called SST (Silicon Spheroidization Treatment), which were originally used only for the modified silumin alloys to spheroidization of eutectic silicon. Temperature holding time in solution annealing of T6 heat treatment is limited in the SST process to only a few minutes. It was studied the effect of casting parameters and periods of solution annealing on ultimate strength, yield strength, and especially ductility that in the unmodified silumin alloy castings is relatively low.
Deep cryogenic treatment (DCT) is gaining popularity as a treatment used to modify structures obtained during heat or thermo-chemical treatment. The article presents the influence of DCT, carried out during heat treatment before and after gas nitriding processes, on the formation of gas nitrided layers on X153CrMoV12 steel. It was found that the use of DCT between quenching and tempering performed prior to gas nitriding processes, increases the hardness, thickness and wear resistance of the nitrided layers. At the same time, if we apply cryogenic treatment during post-heat treatment of nitrided layers, we also get very high wear resistance and increased thickness of nitrided layers, in comparison with conventional gas nitriding of X153CrMoV12 steel. In this case, DCT significantly increases also the hardness of the core by the transformation of retained austenite and the precipitation of fine carbides of alloying elements.
In the paper the use of the artificial neural network to the control of the work of heat treating equipment for the long axisymmetric steel elements with variable diameters is presented. It is assumed that the velocity of the heat source is modified in the process and is in real time updated according to the current diameter. The measurement of the diameter is performed at a constant distance from the heat source (∆z = 0). The main task of the model is control the assumed values of temperature at constant parameters of the heat source such as radius and power. Therefore the parameter of the process controlled by the artificial neural network is the velocity of the heat source. The input data of the network are the values of temperature and the radius of the heated element. The learning, testing and validation sets were determined by using the equation of steady heat transfer process with a convective term. To verify the possibilities of the presented algorithm, based on the solve of the unsteady heat conduction with finite element method, a numerical simulation is performed. The calculations confirm the effectiveness of use of the presented solution, in order to obtain for example the constant depth of the heat affected zone for the geometrically variable hardened axisymmetric objects.
Cyanobacterial and algal blooms lead to the deterioration of freshwater ecosystems but also generate technical problems in water management in the industry. Power plants often use freshwater lakes and reservoirs as a source of cooling water and in the case of cogeneration stations (combined heat and power) also as a source of agents for heating energy distribution. A preliminary research in one of the heat and power stations in eastern Poland which uses water from suffering with algal blooms reservoir was carried out in April 2011. The study was focused on the changes in the phytoplankton quantitative and qualitative structure as well as in basic physico- -chemical parameters along the water treatment line, which consists of several stages serving as sampling points (from the pump station to the purified water tank). The initial phytoplankton biomass in the reservoir was high (fresh biomass: 65.8 mg dm-3, chlorophyll a: 146.7 μg dm-3) with diatoms prevailing (98% of the total biomass) from which the most numerous were: Cyclotella comta and Aulacoseira granulata. After several stages of the purification process (sedimentation, biocide addition, flocculation, gravel filtering, ion exchange) the water still consisted a considerable amount of algae (fresh biomass: 2.48 mg dm-3, chlorophyll a: 6.0 μg dm-3). However, the final biomass in purified water tank (after reversed osmosis process) was very low (fresh biomass: 0.03 mg dm-3, chlorophyll a: 0.1 μg dm-3). Results had shown that high algal biomass in the water used in power generation plant is difficult to remove and consequently requires considerable technical (thus also economical) efforts to adjust the water for the industrial use.
In this work, vacuum hot pressed Ni-Mn-Sn-In Heusler alloys with different concentration of In (0, 2 and 4 at.%), were investigated. The magneto-structural behaviour and microstructure dependencies on chemical composition and on heat treatment were examined. It was found that the martensite start transformation temperature increases with growing In content and to a lesser extent with increasing temperature of heat treatment. The high energy X-ray synchrotron radiation results, demonstrated that both chemical composition as well as temperature of heat treatment slightly modified the crystal structures of the studied alloys. Microstructural investigation performed by transmission electron microscopy confirmed chemical composition and crystal structure changes in the alloys.
This study investigated the effect of T6 heat treatment on the microstructure and scratch wear behavior of hypoeutectic Al-12wt.%Si alloy manufactured by extrusion. Microstructural observation identified spherical eutectic Si phases before and after the heat treatment of alloys (F, T6). Phase analysis confirmed Al matrix and Si phase as well as Al2Cu and Al3Ni, Mg2Si in both alloys. In particular, Al2Cu was finer and more evenly distributed in T6 alloy. This resulted in Vickers hardness of T6 alloy that was 2.3 times greater compared to F alloy. The scratch wear test was conducted using constant load scratch test (CLST) mode and multi-pass scratch test (MPST) mode. The scratch coefficient and worn out volume obtained by such were used to evaluate wear properties before and after heat treatment. In the case of T6 alloy, its scratch coefficient was lower than F alloy in all load ranges. After 15 repeated tests to measure worn out volume, F alloy and T6 alloy measured 1.2×10–1 mm3 and 7.8×10–2 mm3, respectively. In other words, the wear resistance of T6 alloy were confirmed to be better than those of F alloy. In addition, this study attempted to identify the microstructural factors that contribute to the better scratch wear resistance of T6 alloy and wear mechanism from surface and cross-section observations after the wear tests.
Silicon – molybdenum cast iron commonly called SiMo due to its unique properties has becoming more and more interesting engineering material. The history and development of this alloy is relatively long but, due to the significant difficulties during the manufacturing process resulting in the lower final quality than expected, it has not been applied to often in practice. The biggest challenge is its brittleness as a result of the carbides precipitations. During last few years, thanks to the many important researches made and the general foundry technology development, the interest in SiMo iron has been rapidly growing, especially for the castings for heavy duty applications like corrosion, high temperature and wear abrasion resistant parts. In the article the heat treatment attempts to improve the microstructure of SiMo castings has been presented. The goal was to destroy or at least to refine and uniformly distribute the carbides precipitations to improve mechanical properties of the exhaust manifold castings for the cars. The experiments were carried out for the alloy contains approx. 4% Si, 1% Mo and 3.2%C. The range of the research included: hardness measuring, standard mechanical properties and microstructure for as-cast state and after that the subsequent heat treatment process with another properties check. The result of the heat treatment was the elimination of pearlite from the metal matrix. Moreover, the changes of the carbide molybdenum – rich phase morphology were observed. The dispersion of the carbides precipitations in the carbides area was observed. The experiments proved the possibility to control the microstructure and the mechanical properties of the SiMo castings by means of heat treatment but only to some extent.
The paper presents the possibility of the usage of the concfocal microscope for define the type of tribological wear present during the technical dry friction on the testing machine of the pin-on-disc T-01M. The pin was a remelted high-speed steel and the disc was made from sintered carbides. The surface layer of the high-speed steel was remelted with the electric arc with different parameters. The intensity of the electric arc current was changed, the scanning speed and the single, overlapping remeltings were used. On the basis of the 3D, 2D view of the surface friction of the pin (made from the remelted high-speed steel), disc (made from the sintered carbides) and the surface roughness profile run along the marked line, the presence of the abrasive wear can be defined with the description of the elementary wear processes due to the abrasive and/or adhesive wear.
By the very nature of their work, castings used in furnaces for heat treatment and thermo-chemical treatment are exposed to the effect of many unfavorable factors causing their deformation and cracking, significantly shortening the lifetime. The main source of damage are the micro- and macro-thermal stresses appearing in each cycle. As the cost of furnace instrumentation forms a significant part of the total furnace cost, in designing this type of tooling it is important to develop solutions that delay the damage formation process and thus extend the casting operation time. In this article, two structural modifications introduced to pallets castings to reduce thermal stresses arising at various stages of the cooling process are proposed. The essence of the first modification consists in making technological recesses in the wall connections, while the aim of the second one is to reduce the stiffness of the pallet by placing expanders in the external walls. Using the results of simulation analyses carried out by the finite element method, the impact of both proposed solutions on the level of thermal stresses was evaluated.
The results of research on the effect of the type of cooling agent used during heat treatment and thermal-chemical treatment on the formation of temperature gradient and stress-deformation distribution in cast pallets, which are part of furnace accessories used in this treatment, are disclosed. During operation, pallets are exposed to the effect of the same conditions as the charge they are carrying. Cyclic thermal loads are the main cause of excessive deformations or cracks, which after some time of the cast pallet operation result in its withdrawal due to damage. One of the major causes of this damage are stresses formed under the effect of temperature gradient in the unevenly cooled pallet construction. Studies focused on the analysis of heat flow in a charge-loaded pallet, cooled by various cooling agents characterized by different heat transfer coefficients and temperature. Based on the obtained temperature distribution, the stress distribution and the resulting deformation were examined. The results enabled drawing relevant conclusions about the effect of cooling conditions on stresses formed in the direction of the largest temperature gradient.
Issues connected with high quality casting alloys are important for responsible construction elements working in hard conditions. Traditionally, the quality of aluminium casting alloy refers to such microstructure properties as the presence of inclusions and intermetallic phases or porosity. At present, in most cases, Quality index refers to the level of mechanical properties – especially strength parameters, e.g.: UTS, YS, HB, E (Young’s Modulus), K1c (stress intensity factor). Quality indexes are often presented as a function of density. However, generally it is known, that operating durability of construction elements depends both on the strength and plastic of the material. Therefore, for several years now, in specialist literature, the concept of quality index (QI) was present, combines these two important qualities of construction material. The work presents the results of QI research for casting hypoeutectic silumin type EN AC-42100 (EN AC-AlSi7Mg0.3), depending on different variants of heat treatment, including jet cooling during solution treatment.
A possibility to control the strength, hardness and ductility of the L35HM low-alloy structural cast steel by the applied tempering temperature is discussed in the paper. Tests were carried out on samples taken from the two randomly selected industrial melts. Heat treatment of the cast samples included quenching at 900 °C, cooling in an aqueous solution of polymer, and tempering at 600 and 650 °C. The obtained results showed that the difference in the tempering temperature equal to 50 °C can cause the difference of 121 MPa in the values of UTS and of 153 MPa in the values of 0.2%YS. For both melts tempered at 600 °C, the average values of UTS and 0.2%YS were equal to 995 MPa and 933 MPa, respectively. The values of EL and RA did not show any significant differences. Attention was drawn to large differences in strength and hardness observed between the melts tempered at 600 and 650 °C. Despite differences in the mechanical properties of the examined cast steel, the obtained results were superior to those specified by the standard.
The paper presents influence of soaking parameters (temperature and time) on structure and mechanical properties of spheroidal graphite nickel-manganese-copper cast iron, containing: 7.2% Ni, 2.6% Mn and 2.4% Cu. Raw castings showed austenitic structure and relatively low hardness (150 HBW) guaranteeing their good machinability. Heat treatment consisted in soaking the castings within 400 to 600°C for 2 to 10 hours followed by air-cooling. In most cases, soaking caused changes in structure and, in consequence, an increase of hardness in comparison to raw castings. The highest hardness and tensile strength was obtained after soaking at 550°C for 6 hours. At the same time, decrease of the parameters related to plasticity of cast iron (elongation and impact strength) was observed. This resulted from the fact that, in these conditions, the largest fraction of fine-acicular ferrite with relatively high hardness (490 HV0.1) was created in the matrix. At lower temperatures and after shorter soaking times, hardness and tensile strength were lower because of smaller degree of austenite transformation. At higher temperatures and after longer soaking times, fine-dispersive ferrite was produced. That resulted in slightly lower material hardness.
The aim of research was creation of a furnace for aluminum alloys smelting “in a liquid bath” in order to reduce metal loss. In the paper, the author demonstrates the results of research on smelting of aluminum alloys in a shaft-reverberatory furnace designed by the author. It has been shown that smelting aluminum alloy in a liquid bath was able to significantly reduce aluminum loss and that shaft-reverberatory design provided high efficiency and productivity along with lower energy costs. Ensuring continuous operation of the liquid bath and superheating chamber, which tapped alloy with the required texture, was achieved by means of the optimal design of partition between them. The optimum section of the connecting channels between the liquid bath of smelting and the superheating chamber has been theoretically substantiated and experimentally confirmed. The author proposed a workable shaft-reverberatory furnace for aluminum alloys smelting, providing solid charge melting in a liquid bath.
Various examples of the design of cast elements of the equipment used in furnaces for the heat treatment of machine parts are given. Shortcomings in their performance are indicated. Reasons for required stability of equipment are briefly discussed. Elements of equipment illustrate the possibilities of using a charge-carrying pallet with dimensions of 900×600×45 mm as a basis for multi-component technological equipment. Introducing additional elements, such as metal baskets, intermediate pallets or crossbars to the main pallet, it becomes possible to create different configurations of this equipment. The technological equipment presented and discussed here is offered to different plants which heat-treat a wide variety of produced parts. It was found that the reliability and durability of new designed equipment can be checked only during practical use. For large plants dealing with the heat treatment of bulk quantities of parts homogeneous or similar in shape is recommended to use the dedicated tooling.
In this paper, the effect of changes the parameters of heat treatment on the structure and the degree of elements segregation was determined, in the context of corrosion resistance of ductile iron Ni-Mn-Cu, containing 7.2% Ni, 2.6% Mn and 2.4% Cu. In the condition after casting, castings of austenitic matrix and 160HBW hardness were obtained. The achieved castings were soaked at 450, 550 and 650°C for 4, 8 and 12 hours, then cooled down at the ambient air. In most cases, the heat treatment resulted in a change in the castings matrix, had the consequence of increasing their hardness in comparison to raw castings. Increasing the temperature and prolonging soaking time resulted in increasing the degree of transformation of austenite, while reducing the degree of elements segregation. This led to the formation of slightly bigger number of pitting due to corrosion, but not so deep and more evenly distributed in comparison to raw castings. Wherein the results of corrosion tests show that heat treatment of castings did not significantly change their corrosion resistance in comparison to raw castings, in contrast to the significant increase in mechanical properties.
The object of the experimental studies was to determine the mechanical properties of a hypoeutectic EN AC - 42100 (EN ACAlSi7Mg0,3) silumin alloy, where the said properties are changing as a result of subjecting the samples of different types to solution treatment. An important aspect of the studies was the use type of device for the heat treatment. As a basic parameter representing the mechanical properties, the tensile strength of the metal (Rm) was adopted.
The paper presents the results of examination concerning optimization of the σ phase precipitates with respect to the functional properties of ferritic-austenitic cast steel. The examined material comprised two grades of corrosion-resistant cast steel, namely GX2CrNiMoN25-6-3 and GX2CrNiMoCuN25-6-3-3, used for example in elements of systems of wet flue gas desulphurisation in power industry. The operating conditions in media heated up to 70°C and containing Cl- and SO4 ions and solid particles produce high erosive and corrosive wear. The work proposes an application of the σ phase as a component of precipitation strengthening mechanism in order to increase the functional properties of the material. Morphology and quantities of σ phase precipitates were determined, as well as its influence on the erosion and corrosion wear resistance. It was shown that annealing at 800°C or 900°C significantly improves tribological properties as compared with the supersaturated state, and the best erosion and corrosion wear resistance achieved due to the ferrite decomposition δ → γ’ + σ was exhibited in the case of annealing at the temperature of 800°C for 3 hours.