Wpływ zawartości węgla i chromu na odporność na zużycie ferrytycznych wysokochromowych stopów odlewniczych

The studies of abrasion wear behaviour have as a target more profound knowledge of the wear mechanism and of the possibilities to improve the wear resistance. As regards an improvement of wear resistance, the results of the studies enable: simple comparison of the material properties, a description, by means of regression egratrans, of a space determined by the scope of variables used, as well as, an application of the selected theory in describing final output of the tests. Applying Bitter's theory, the wear of high-chromium ferritic alloys attacked by an abrasive material at 450oC was described. The theory enables the material wear rate to be analyzed as a function of the incidence angle of abrasive, with the material loss in volume ascribed separately to the two different wear mechanisms, i.e. microcutting and surface fatigue. Analysis leads to a conclusion that the characteristic curves can be divided into three groups. The division can be made adopting as a point of reference two curves for which the value of the product of Cr and C content is constant. For the first group the product does not exceed the value of 30. Group three includes the alloys for which the product of Cr and C content exceeds in this case the value of 60. For the second group of alloys, the product of chromium and carbon content is within the range of 30 to 60.Artykuł dotyczy analizy mechanizmów ściernego zużycia erozyjnego oraz możliwości podniesienia odporności na ścieranie. Autorzy opisali procesy zużycia ferrytycznych stopów wysokochromowych, zachodzących pod wpływem materiału ściernego w temperaturze 450°C. Zaprezentowano wyniki, przeprowadzonej przy wykorzystaniu teorii Bittera, analizy intensywności zużycia materiału, prowadzącej do konkluzji, że odporność na zużycie można klasyfikować w oparciu o uzyskane krzywe charakterystyczne, wśród których autorzy wyróżnili i opisali trzy grupy

Cast construction elements for heat treatment furnaces

The study presents sketches and photos of the cast creep-resistant components used in various types of heat treatment furnaces. The shape of the elements results from the type of the operation carried out in the furnace, while dimensions are adjusted to the size of the furnace working chamber. The castings are mainly made from the high-alloyed, austenitic chromium-nickel or nickel-chromium steel, selecting the grade in accordance with the furnace operating conditions described by the rated temperature, the type and parameters of the applied operating atmosphere, and the charge weight. Typical examples in this family of construction elements are: crucibles, roller tracks, radiant tubes and guides. The majority of castings are produced in sand moulds

Castings in Pit Furnaces for Heat Treatment

The article presents examples of typical designs of the cast technological equipment used in pit furnaces for the heat treatment of metals and alloys. The equipment consists of a set of castings connected together in a proper way and used for the formation and transport of charge, which consists of the heat treated parts. Typical equipment has the shape of a cylinder. Usually it comprises a basic pallet (carrier) completed with other elements, i.e. intermediate pallets, rods, spacers, cross-bars and hooks, their number depending on the number and shape of heat-treated products and on production volume. The simplest design solution is to use a cylindrical basket where heat treated products are arranged in a loose configuration. The majority of elements forming the furnace equipment are castings produced in sand molds. Some of them were designed and manufactured in a Foundry of the West Pomeranian University of Technology in Szczecin

Cast Grates Used in Heat Treatment Furnaces

Examples of cast grates whose construction was based on previously used "old" patterns of the technological equipment for heat treatment furnaces (TEq) are presented. Manufacturers of this type of castings have at their disposal numerous earlier designs of the applied TEq. Their adaptation for the needs of a new order, i.e. the creation of a new design or modification of the already existing one, significantly reduces both cost and time of the implementation. It also allows making new grate constructions of various shapes and sizes, reducing in this way the number of patterns stored by the manufacturer of castings. The examples of cast grates shown and discussed in this study document the variety of ways that can be used when making them from the already existing patterns or castings. The presented grates were made using master patterns, entire castings or their fragments, and modular segments

Mechanical Stresses Induced by Compression in Castings of the Load-carrying Grate

The main aim of this study was to examine the compression-induced state of stress arising in castings of the guide grates during operation in pusher-type furnaces for heat treatment. The effect of grate compression is caused by its forced movement in the furnace. The introduction of flexible segments to the grate structure changes in a significant way the stress distribution, mainly by decreasing its value, and consequently considerably extends the lifetime of the grates. The stress distribution was examined in the grates with flexible segments arranged crosswise (normal to the direction of the grate compression) and lengthwise (following the direction of force). A regression equation was derived to describe the relationship between the stress level in a row of ribs in the grate and the number of flexible segments of a lengthwise orientation placed in this row. It was found that, regardless of the distribution of the flexible segments in a row, the stress values were similar in all the ribs included in this row, and in a given row of the ribs/flexible segments a similar state of stress prevailed, irrespective of the position of this row in the whole structure of the grate and of the number of the ribs/flexible segments introduced therein. Parts of the grate responsible for the stress transfer were indicated and also parts which play the role of an element bonding the structure

Casting of Hearth Plates from High-chromium Steel

The paper presents the results of studies on the development of manufacturing technologies to cast hearth plates operating in chamber furnaces for heat treatment. Castings made from the heat-resistant G-X40CrNiSi27-4 steel were poured in hand-made green sand molds. The following operations were performed: computer simulation to predict the distribution of internal defects in castings produced by the above mentioned technology with risers bare and coated with exothermic and insulating sleeves, analysis of each variant of the technology, and manufacture of experimental castings. As a result of the conducted studies and analysis it was found that the use of risers with exothermic sleeves does not affect to a significant degree the quality of the produced castings of hearth plates, but it significantly improves the metal yield

The Flexibility of Pusher Furnace Grate

The lifetime of guide grates in pusher furnaces for heat treatment could be increased by raising the flexibility of their structure through, for example, the replacement of straight ribs, parallel to the direction of grate movement, with more flexible segments. The deformability of grates with flexible segments arranged in two orientations, i.e. crosswise (perpendicular to the direction of compression) and lengthwise (parallel to the direction of compression), was examined. The compression process was simulated using SolidWorks Simulation program. Relevant regression equations were also derived describing the dependence of force inducing the grate deformation by 0.25 mm ‒ modulus of grate elasticity ‒ on the number of flexible segments in established orientations. These calculations were made in Statistica and Scilab programs. It has been demonstrated that, with the same number of segments, the crosswise orientation of flexible segments increases the grate structure flexibility in a more efficient way than the lengthwise orientation. It has also been proved that a crucial effect on the grate flexibility has only the quantity and orientation of segments (crosswise / lengthwise), while the exact position of segments changes the grate flexibility by less than 1%

Casting of Hearth Plates from High-chromium Steel

The paper presents the results of studies on the development of manufacturing technologies to cast hearth plates operating in chamber furnaces for heat treatment. Castings made from the heat-resistant G-X40CrNiSi27-4 steel were poured in hand-made green sand molds. The following operations were performed: computer simulation to predict the distribution of internal defects in castings produced by the above mentioned technology with risers bare and coated with exothermic and insulating sleeves, analysis of each variant of the technology, and manufacture of experimental castings. As a result of the conducted studies and analysis it was found that the use of risers with exothermic sleeves does not affect to a significant degree the quality of the produced castings of hearth plates, but it significantly improves the metal yield

Mechanical Stresses Induced by Compression in Castings of the Load-carrying Grate

The main aim of this study was to examine the compression-induced state of stress arising in castings of the guide grates during operation in pusher-type furnaces for heat treatment. The effect of grate compression is caused by its forced movement in the furnace. The introduction of flexible segments to the grate structure changes in a significant way the stress distribution, mainly by decreasing its value, and consequently considerably extends the lifetime of the grates. The stress distribution was examined in the grates with flexible segments arranged crosswise (normal to the direction of the grate compression) and lengthwise (following the direction of force). A regression equation was derived to describe the relationship between the stress level in a row of ribs in the grate and the number of flexible segments of a lengthwise orientation placed in this row. It was found that, regardless of the distribution of the flexible segments in a row, the stress values were similar in all the ribs included in this row, and in a given row of the ribs/flexible segments a similar state of stress prevailed, irrespective of the position of this row in the whole structure of the grate and of the number of the ribs/flexible segments introduced therein. Parts of the grate responsible for the stress transfer were indicated and also parts which play the role of an element bonding the structure