Wyniki wyszukiwania - BazTech

1

Microstructure and high-temperature strength characteristics of boiler tubes produced by foreign companies in accordance with Ukrainian standard

Oprishko L., Golovnyak T., Poltava I., Stradomski Z., Deyneko L.

Hutnik, Wiadomości Hutnicze

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2015

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Vol. 82, nr 11

707--712

EN

Features of microstructure and high-temperature strength characteristics (creep rupture strength and plasticity) of boiler tubes produced of steel grades 20 and 12Cr1МoV by Z-Group Steel Holding Divize Válcovny Trub Chomutov (Czech Republic), Tubos Reunidos Industrial, S.L.U. (Spain), Benteler Steel/Tube GmbH (Germany) and Shanghai Rongfa Enterprise Development LTD (China) in accordance with Ukrainian standard (TU 14-3-460) were analyzed. Availability of utilization in Ukrainian heat and power engineering of boiler tubes produced by above-mentioned companies on conditions that their production process is enhanced to ensure quality indicators of boiler tube material (including operating characteristics) in accordance with Ukrainian normative documents.

PL

Dokonano analizy cech mikrostruktury i charakterystyki wysokotemperaturowej wytrzymałości (wytrzymałość na pęknięcia pełzaniowe i plastyczność) rur kotłowych produkowanych ze stali gatunków 20 i 12CrMoV przez Z-Group Steel Holding Divize Válcovny Trub Chomutov (Czechy), Tubos Reunidos Industrial, S.L.U. (Hiszpania), Benteler Steel/Tube GmbH (Niemcy) and Shanghai Rongfa Enterprise Development LTD (Chiny) w zakresie ich zgodności z normami ukraińskimi (TU 14-3-460). Możliwość wykorzystania w ukraińskim przemyśle energetycznym rur kotłowych wyprodukowanych przez wyżej wymienione zakłady uwarunkowana jest zapewnieniem wskaźników jakości materiału rur kotłowych (łącznie z charakterystykami pracy) w zgodności z ukraińskimi dokumentami normatywnymi.

2

The Microstructure of Thin-walled GX2CrNiMoN25-6-3 Cast Steel Made by Centrifugal Casting

Stradomski G., Nadolski M., Stradomski Z.

Archives of Foundry Engineering

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2015

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Vol. 15, iss. 3 spec.

77--82

EN

The paper presents the results of investigation into the technological possibility of making light-section castings of GX2CrNiMoN25-6-3 cast steel. Due the fact that the GX2CrNiMoN25-6-3 duplex cast steel has a complex microstructure authors of this paper took on its analysis. For making castings with a wall thickness in the thinnest place as small as below 1 mm, the centrifugal casting technology, as it was presented in the paper [1], is one of the most effective technology. In the paper was made the analysis of four different parameters of the casting process and different parameters of heat treatment.

3

Technological Assessment of the Possibility of Making Light-section Castings of GX2CrNiMoN25-6-3 Cast Steel by the Centrifugal Casting Method

Stradomski G., Nadolski M., Stradomski Z.

Archives of Foundry Engineering

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2015

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Vol. 15, iss. 3

57--60

EN

The paper presents the results of investigation into the technological possibility of making light-section castings of GX2CrNiMoN25-6-3 cast steel. For making castings with a wall thickness in the thinnest place as small as below 1 mm, the centrifugal casting technology was employed. The technology under consideration enables items with high surface quality to be obtained, while providing a reduced consumption of the charge materials and, as a result, a reduction in the costs of unit casting production.

4

The change of solidification mechanism of ferritic-austenitic cast steel

Stradomski G., Stradomski Z., Denis-Brewczyńska D.

Journal of Achievements in Materials and Manufacturing Engineering

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2014

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Vol. 63, nr 2

58--64

EN

Purpose: The paper presents the results of research on the microstructure changes of two grade of duplex cast steels with a varying carbon, with and without addition of copper. Design/methodology/approach: The addition of copper have a significant effect on the microstructure of analyzed cast steels. The changes in the mechanism of solidification was also observed during numerical simulation made in the FactSage softwares. Findings: The cause for undertaking the research were technological problems with hot cracking in bulk castings of duplex cast steel with a carbon content of approx. 0.06%. Practical implications: The research has shown a significant effect of increased carbon content on the ferrite and austenite microstructure morphology, while exceeding the carbon content of 0.06% results in a change of the shape of primary grains from equiaxial to columnar. Originality/value: Among the steel and cast steel resistant to corrosion most modern and dynamically developing group are ferritic-austenitic alloys, commonly known as duplex. Higher than austenitic steels, mechanical properties and good corrosion resistance in both overall and pitting make duplex steels irreplaceable material in the petrochemical industry, power, pulp and paper, food.

5

Wear resistance of dental burs with a diamond coating

Gwoździk M., Nitkiewicz Z., Stradomski Z., Basiaga M.

Inżynieria Materiałowa

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2014

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Vol. 35, nr 2

143--146

EN

The paper presents the results of studies on the degree of wear of commercial dental drills with a diamond coating. Drills made of a corrosion resistant steel were covered with a nickel-diamond composite of varying diamond grain size. The assessment comprised drills intended for the removal of old fillings and crowns and also drills intended to prepare tooth tissues by grinding. The observations of worn drill surfaces were performed after long-term usage in a dentist’s surgery. It was found that the damage was observed for the studied dental instruments both during their usage and during sterilisation.

PL

W pracy przestawiono wyniki badań stopnia zużycia komercyjnych wierteł stomatologicznych z nasypem diamentowym. Wiertła ze stali odpornej na korozję pokryto kompozytem niklowo-diamentowym o różnej ziarnistości diamentu. Ocenie poddano wiertła przeznaczone do usuwania starych wypełnień i koron, a także wiertła przeznaczone do przygotowania tkanek zęba przez szlifowanie. Obserwacje powierzchni zużytych wierteł przeprowadzono po długotrwałej eksploatacji w gabinecie stomatologicznym. Stwierdzono, że badane narzędzia stomatologiczne ulegają zniszczeniu zarówno w procesie ich użytkowania, jak i podczas sterylizacji.

6

The influence of deformation scheme on grain boundaries structure of carbon steel boiler tubes

Opryszko L. V., Suchomlin G. D., Stradomski Z., Deyneko L. N.

Hutnik, Wiadomości Hutnicze

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2014

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Vol. 81, nr 5

308--313

EN

The structure of grain boundaries was investigated in ferritic boiler tubes made of steel 20, manufactured by hot extruding and hot rolling. It has been observed that in the metallic matrix structure of hot extruded tubes the amount of special boundaries Σ = 3n (acc. to the concept of coincidence-sites) is significantly higher (up to 26.5%) than in hot rolled tubes (up to 12.5%), which has a positive impact on the ultimate strength.

PL

Wykonano badania struktury granic ziarn, ferrytycznych rur kotłowych ze stali 20, wytworzonej poprzez wyciskanie na gorąco i walcowanie na gorąco. Zaobserwowano, że w strukturze metalicznej osnowy rur wyciskanych na gorąco ilość granic specjalnych Σ = 3n (według koncepcji gęstości węzłów koincydentnych) jest istotnie większa (do 26,5%), niż w walcowanych na gorąco (do 12,5%), co ma pozytywny wpływ na wytrzymałoś doraźną.

7

Kinetics of the σ Phase Precipitation in Respect of Erosion-corrosion Wear of Duplex Cast Steel

Brodziak-Hyska A., Stradomski Z., Kolan C.

Archives of Foundry Engineering

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2014

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Vol. 14, iss. 1

17--20

EN

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. The paper presents the results of examination of the kinetics of σ phase precipitation at a temperature of 800°C and at times ranging from 30 to 180 minutes. Changes in the morphology of precipitates of the σ phase were determined using the value of shape factor R. Resistance to erosion-corrosion wear of duplex cast steel was correlated with the kinetics of sigma phase precipitating.

8

Vacuum-arc chromium coatings for the protection of gun barrels

Nadtoka V. M., Pankov R. V., Stradomski Z., Deyneko l. M., Lytvynenko O

Hutnik, Wiadomości Hutnicze

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2013

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Vol. 80, nr 5

355--361

EN

Chromium coatings applied on the internal surface of tubular samples of (0.3÷0.4%C, 1.2-1.5 %Cr, 3÷3.5%Ni, 0.35÷0.45% Mo, 0.1÷018% V ) steel by the vacuum-arc deposition method are discussed in the paper. The results of metallographic examination of the structure and properties of the coatings are given. It has been shown that under the conditions of dynamic loadings, high temperature influence and frequent heat changes, no thermal fatigue cracks are present on samples with a vacuum-arc plasma coating, whereas parts with an electrolytic coating have by 1.8÷2.2 times more cracks compared to samples in the initial condition. The results of the research show the potential of the method for producing coatings by vacuum-arc evaporation of refractory metals with the subsequent condensation of ionized vapors on the internal barrel surface to protect the gun barrels against propellant-induced erosion and wear.

PL

W pracy omówiono kwestię nanoszenia chromowych powłok ochronnych na wewnętrzne części próbek rurowych ze stali (0,3÷0,4%C, 1,2÷1,5 %Cr, 3÷3,5%Ni, 0,35÷0,45% Mo, 0,1÷018% V ) z wykorzystaniem metody próżniowo-łukowej. Przestawione zostały wyniki badań metalograficznych oraz własności badanych struktur powłok. Udowodniono, że w warunkach dynamicznego obciążenia, wysokich temperatur oraz ich częstych zmian, nie występują pęknięcia zmęczeniowe w próbkach pokrywanych w technologii plazmowo-próżniowo-łukowej, natomiast w próbkach pokrywanych elektrolitycznie występowało o 1,8÷2,2 więcej pęknięć niż w próbkach wyjściowych. Wyniki badań wskazują na znaczny potencjał omawianej metody produkcji powłok za pomocą odparowywania metali reaktywnych z jednoczesnym osadzaniem zjonizowanej pary na wewnętrznych ściankach lufy, podnosząc w ten sposób odporność korozyjno-erozyjną.

9

Fracture mechanisms in steel castings

Stradomski Z., Stachura S., Stradomski G.

Archives of Foundry Engineering

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2013

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Vol. 13, iss. 3

88--91

EN

The investigations were inspired with the problem of cracking of steel castings during the production process. A single mechanism of decohesion – the intergranular one – occurs in the case of hot cracking, while a variety of structural factors is decisive for hot cracking initiation, depending on chemical composition of the cast steel. The low-carbon and low-alloyed steel castings crack due to the presence of the type II sulphides, the cause of cracking of the high-carbon tool cast steels is the net of secondary cementite and/or ledeburite precipitated along the boundaries of solidified grains. Also the brittle phosphor and carbide eutectics precipitated in the final stage solidification are responsible for cracking of castings made of Hadfield steel. The examination of mechanical properties at 1050°C revealed low or very low strength of high-carbon cast steels.

10

Optimization of sigma phase precipitates with respect to the functional properties of duplex cast steel

Stradomski Z., Brodziak-Hyska A., Kolan C.

Archives of Foundry Engineering

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2012

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Vol. 12, iss. 2

75-78

EN

The paper presents the results of examination concerning optimization of the \sigma 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 \sigma phase as a component of precipitation strengthening mechanism in order to increase the functional properties of the material. Morphology and quantities of \sigma 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 [...] was exhibited in the case of annealing at the temperature of 800 C for 3 hours.

11

Ferritic-austenitic cast steel - selected problems

Stradomski Z.

Archives of Foundry Engineering

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2011

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Vol. 11, iss. 3

47-50

EN

The author has been involved in the problems occurring in the manufacture of ferritic-austenitic cast steel castings for many years. The author's remarks and investigation results reported in this article will enable potential manufacturers to determine their own technical capabilities and structural determinants related to the chemical composition of material, which are crucial to the good quality of a casting. Particular emphasis should be laid on the role of enhanced carbon content, the presence of copper, the precipitates of the [...] phase, and the nature of solidification structure in the tendency of duplex-type cast steel to cracking. It seems that in view of the pro-ecological activities undertaken, including flue gas desulphurization in coal-fired power plants, efforts should be made in steel foundries to introduce selected grades of ferritic-austenitic cast steel to production.

12

Charakterystyka stali nowej generacji dla bloków energetycznych

Stachura S., Gwoździk M., Stradomski Z.

Energetyka

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2010

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nr 2

94-102

PL

Opisano stale przeznaczone na elementy turbin i kotłów eksploatowane przy wyższych temperaturach i ciśnieniu pary w nowych oraz modernizowanych blokach energetycznych. Omówiono mikrostrukturę oraz mikromechanizmy umocnienia ulepszonych cieplnie wieloskładnikowych stali o niskiej i wysokiej zawartości chromu przeznaczonych do długotrwałej eksploatacji odpowiednio w temperaturach <580°C i <620°C. Omówiono zmiany zachodzące w strukturze stali w warunkach pełzania prowadzące do ciągłego obniżania wytrzymałości na pełzanie.

EN

The paper presents steels designed for turbine and boiler components operated at higher temperatures and steam pressure in new and modernised power units. The microstructure and strengthening mechanisms have been discussed for toughened multi-component steels of low and high chromium content designed for long-lasting operation at temperatures <580°C and <620°C, respectively. Changes occurring in the steel structure at creep conditions have been discussed, resulting in continuous decrease in the creep strength.

13

The influence of sigma phase on erosion and corrosion properties of duplex steel

Stradomski Z., Brodziak A.

Archives of Foundry Engineering

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2010

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Vol. 10, iss. 3

85--88

EN

The paper presents the results of investigations concerning the influence of σ phase precipitating on the erosion and corrosion properties of ferritic-austenitic cast steel. The object of investigation have been two grades of corrosion-resistant cast steel: GX2CrNiMoCuN25-6-3-3 and GX2CrNiMoN25-6-3. The examinations have involved measurements for obtaining potentiodynamic curves, examination of erosion and corrosion resistance, and microstructural analysis. The supersaturated cast steel and the material after heat treatment have been examined. It has been found that the tribological properties of supersaturated cast steel are worse than those of the supersaturated and annealed cast steel. The highest erosion and corrosion resistance has been achieved as a result of ferrite decomposition δ → γ’+ σ. The examinations of corrosion resistance have revealed that the ageing process after supersaturation do not cause significant changes in the anti-corrosive properties.

14

The assessment of hot cracking susceptibility of ferritic-austenitic cast iron

Stradomski Z., Soiński M. S., Stradomski G.

Archives of Foundry Engineering

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2010

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Vol. 10, iss. 2

159--162

EN

An inspiration to the research work has arisen from the problems related to cracking of massive castings made of ferritic-austenitic cast steel. The shape and the character of crack trajectories indicate that they are hot cracks. Investigations have included two cast steel grades, namely GX2CrNiMoN25-6-3 and GX2CrNiMoCuN25-6-3-3, because some customers had demanded for copper addition which makes possible the ageing treatment; also the alloys with increased carbon content have been investigated and this resulted from difficulties in obtaining sufficiently low carbon content (Cmax 0,03%) in many Polish foundries which are not equipped with argon-oxygen devices for cast steel decarburizing. The method of critical size of a specimen similar in shape to the Hall test specimen has been applied to examine the cast steel susceptibility to hot cracking. The examination results undoubtedly indicate the negative influence of the increased carbon content, especially in the presence of copper. The intercrystalline character of cracks which propagate along the dendritic austenite precipitates suggests that the peritectic reaction occurs in the final stage of solidification, being induced by segregation of the strong austenite-forming alloying elements. The increased hot cracking susceptibility of the ferrite-austenite cast steel containing copper, particularly with simultaneously increased carbon content, indicates that the implementation of production technologies concerning this material should be started with production of castings made of alloy grades without copper addition.

15

Assessment the possibility of enhancing the tribological properties of the ferritic-austenitic cast steel

Brodziak A., Stradomski Z.

Archives of Foundry Engineering

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2010

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Vol. 10, iss. 1 spec.

287--290

EN

The purpose of the research was to explore the possibility of enhancing the tribological properties of the ferritic-austenitic cast steel which is widely used in combustion gas desulphurization systems in the power industry. The subject of the research is the GX2CrNiMoN25-6-3 cast steel, a material for making pump rotors and other parts intended for operation at a temperature of up to 70 °C in a water suspension containing Cl- and SO4-2 ions and sand / gypsum particles. It seems that in some applications, at low dynamics of parts’ operation and a predominance of erosive phenomena over corrosive ones, there is a potential for using the σ phase as a structural constituent that enhances the tribological properties. However, due to the increased brittleness of the material, a need arises for optimizing the quantity of this phase and carrying out detailed research into the morphology of precipitates. To describe the tribological properties, the testing of the erosive and corrosive wear mechanism was used, which was carried out on a test stand of the authors' own construction. Metallographic and stereological examinations and hardness tests were performed, which enabled the understanding of the successive stages of tribological wear of the cast steel under investigation. The increasing volumetric share of the σ phase advantageously influenced the erosive wear resistance of the material.

16

The influence of microstructure on the mechanical properties of metallurgical rolls made of G200CrMoNi4-3-3 cast steel

Brodziak A., Stradomski Z., Pirek A.

Archives of Foundry Engineering

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2009

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Vol. 9, iss. 3

21-24

EN

The subject of the study is the high-carbon tool cast steel G200CrMoNi4-3-3 used for metallurgical rolls, especially in section rolling mills. The test material was derived from a roll damaged in production; therefore, the authors had the material in a raw state at their disposal, on which they were able to carry out additional heat treatment operations. The pearlitic matrix of casting steel G200CrMoNi4-3-3 allows machining to be done to modify the pass or to remove any defects, and the primary and secondary precipitates of carbides enhance the tribological properties. The authors have been for years involved in the optimization of the structure of this material by slight correction to its chemical composition and/or the modification of heat treatment. The presented principles of heat treatment modifications will lead to considerable economic and ecologic profits. It has also been demonstrated that raising slightly the contents of carbide-forming elements, which markedly increases the quantity of transformed ledeburite, results in an enhancement of tribological properties. The analysis of a dozen or so rolls exploited down to the dead roll diameter has shown that roll of cast steel with increased contents of carbon and carbide-forming elements exhibit better service properties, as characterized by the amount of feedstock rolled. Such a method of enhancing the service properties required the assessment of fracture toughness, which was verified using the linear-elastic methods of fracture mechanics.

17

The influence of copper on the microstructure and selected parameters of duplex cast steel

Stradomska J., Stachura S., Stradomski Z., Soiński M. S.

Archives of Foundry Engineering

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2009

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Vol. 9, iss. 1

87-90

EN

Technological problems related to mastering the production of castings made of ferritic-austenitic cast steel (duplex type), i.e problems related to low carbon content (Cmax 0.03%) and high hot cracking susceptibility due to phenomena taking place during solidification and cooling of castings, cause that this material, although attractive due to its price and improving company prestige, is rarely produced in Poland. The undertaken attempts have mainly dealt with GX2CrNiMoCu25-6-3-3 grade containing copper due to the requirements of power industry which is the main possible customer with respect to the elements made of duplex cast steel. The authors of this paper have thought it reasonable to present selected aspects of microstructural and mechanical properties for the two cast steel grades described in the PN-EN 10283:2002 Standard, which differ only by Cu addition. The examinations concerned mainly the as-cast condition, because it is decisive for the defective production. It has been shown that the weak austenite-forming copper exerts a strong influence on the primary structure of cast steel, resulting in precipitating the [...] austenite within ferrite, where the austenite is crystallographically dependent on the matrix. The GX2CrNiMoCu25-6-3-3 cast steel in supersaturated state is characterised by Charpy V-notch impact energy lower by about 30% than for the cast steel grade without Cu addition.

18

The analysis of solidification process of ferritic-austenitic cast steel

Stradomska J., Stradomski Z., Soiński M. S.

Archives of Foundry Engineering

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2009

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Vol. 9, iss. 1

83-86

EN

One of the most common defects leading to the rejection of faulty castings made of duplex cast steel is hot cracking. Hot cracking - differently from cold cracking which occur on cooling, when the material exhibits already distinct elastic properties - proceeds in the semi-solid state, particularly when the temperature of solidifying casting is close to the equilibrium solidus point. There exist a range of temperatures in the vicinity of the solidus point within which the solidifying metal shows very small deformation ability and small strength. Therefore even little stresses occurring at the solidification stage and caused by density difference between ferrite and austenite, or restricted shrinkage, or various temperature gradients, can be the reason of hot cracking. Copper addition, as it is used in cast steel grades implemented in Polish power industry applications, decreases the temperature of the end of solidification, thus affecting beneficially the surface reproduction quality, but on the other hand it can promote, along with several other elements contained in duplex cast steel, the peritectic transformation during the last stage of solidification. The presence of peritectic solidification, i.e. strictly speaking the structural stresses accompanying that process, is the well-known and significant reason of the increased steel defectiveness in the continuous steel casting (CSC) technology if the steel with carbon content promoting the peritectic transformation is processed. The authors have presented the examination results of the solidification phenomenon for two duplex cast steel grades - one without copper addition, and the other with addition of about 3.0% Cu.

19

Studying possibilities to improve the functional properties of metallurgical rolls

Stradomski Z., Pirek A., Stachura S.

Archives of Foundry Engineering

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2008

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Vol. 8, iss. 1 spec.

313--316

EN

The paper presents results of investigations and authors’ opinion on improving functional properties of metallurgical rolls cast from G200CrMoNi 4-3-3 cast steel, one of most often used for rolls in section mills. These mills feature quicker than flat rolls wear of tool’s pass, what requires more frequent regeneration. The machining requires a relatively low hardness, which is ensured by the pearlitic matrix of cast steel studied. The authors suggest to achieve the optimisation of tribological properties through adjustment of the chemical composition or/and modification of the heat treatment. In the study presented only the carbon content was slightly inereased (having carbide-forming elements in view) resulting in the increase in ledeburitie carbides. However, this most obvious way of improving the abrasive wear resistance increases the threat of rolls cracking and therefore requires verification using the fracture mechanics method. Statistical analysis of randomly selected few dozens of rolls have shown for this grade of cast steel a trend to reduce the carbon content by the manufacturer, maintaining it at the lower range of limits specified by the standard and not to increase it. The analysis of the wear mechanism of surfaces of worn out rolls made of G200CrMoNi 4-3-3 cast steel allows making suggestions on the possibilities of heat treatment changes, what also has been presented in the paper.

20

Significance of the [sigma] phase for the erosive

Stradomski Z., Soiński M. S., Stradomska J., Dyja D.

Archives of Foundry Engineering

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2008

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Vol. 8, iss. 3

141-144

EN

The work presents a possibility of increasing the tribological properties of the ferritic-austenitic cast steel (the so called duplex cast steel) of GX2CrNiMoCu25-6-3-3 grade by taking an advantage of the mechanism of precipitation strengthening with the [sigma] phase arisen due to the eutectoidal ferrite decomposition. The examinations have been held using specimens cut out of both a massive casting (an impeller of about one-ton mass) and a thin-walled casting (of the wall thickness about 2 mm). The huge impeller has been made of cast steel containing 0.09% of carbon (i.e. exceeding the demands of the current standard), while the thin-walled casting has been of cast steel with extremely low carbon content (0.024%) due to applying the input material of a great purity. Employing the moulding material with alkaline phenolic binder hardened with CO_2 and using the zirconia coating has allowed for achieving about 20% fraction of [sigma] phase in the as-cast state of the casting. An increase in [sigma] phase fraction in the structure of duplex cast steel results in improving the abrasive wear resistance of the material. It should be stressed that despite the high fraction of the sigma phase in the material, the crack-free castings have been obtained. An addition of copper has made possible producing the high-quality thin-walled (as for cast steel) castings of smooth surfaces. No defects (including shrinkage porosity) have been found.