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1
Content available The Analysis of AISI A3 Type Ferritic-Austenitic Cast Steel Crystallization Mechanism
Stradomski G.
Archives of Foundry Engineering
|
2017
|
Vol. 17, iss. 3
229--233
EN
High-alloy corrosion-resistant ferritic-austenitic steels and cast steels are a group of high potential construction materials. This is evidenced by the development of new alloys both low alloys grades such as the ASTM 2101 series or high alloy like super or hyper duplex series 2507 or 2707 [1-5]. The potential of these materials is also presented by the increasing frequency of sintered components made both from duplex steel powders as well as mixtures of austenitic and ferritic steels [6, 7]. This article is a continuation of the problems presented in earlier works [5, 8, 9] and its inspiration were technological observed problems related to the production of duplex cast steel. The analyzed AISI A3 type cast steel is widely used in both wet exhaust gas desulphurisation systems in coal fired power plants as well as in aggressive working environments. Technological problems such as hot cracking presented in works [5, 8], with are effects of the rich chemical composition and phenomena occurring during crystallization, must be known to the technologists. The presented in this work phenomena which occur during the crystallization and cooling of ferritic-austenitic cast steel were investigated using numerical methods with use of the ThermoCalc and FactSage® software, as well with use of experimental thermal-derivative analysis.
2
Content available Microstructure and Mechanical Properties of High-Alloyed 23Cr-5Mn-2Ni-3Mo Cast Steel
Kalandyk B., Zapała R., Kasińska J., Wróbel M., Balicki M.
Archives of Metallurgy and Materials
|
2015
|
Vol. 60, iss. 4
2529--2534
EN
The article presents the microstructure and mechanical properties of cast duplex stainless steel type 23Cr-5Mn-2Ni-3Mo. It has been shown that the structure of the tested cast steel is composed of ferrite enriched in Cr, Mo and Si, and austenite enriched in Mn and Ni. In the initial state, at the interface, precipitates rich in Cr and Mo were present. A high carbon content (0.08%C) in this cast steel indicates that probably those were complex carbides of the M23C6 type and/or σ phase. Studies have proved that the solution annealing conducted at 1060°C was not sufficient for their full dissolution, while at the solutioning temperature of 1150°C, the structure of the tested material was composed of ferrite and austenite. Partial replacement of Ni by two other austenite-forming elements, which are Mn and N, has ensured obtaining mechanical properties comparable to cast duplex 24Cr-5Ni-3Mo steel of the second generation. Basing on the results of static tensile test, a twice higher yield strength was proved to be obtained, compared to the cast austenitic 18Cr-9Ni and 19Cr-11Ni-2Mo steel commonly used in the foundry industry. In addition to the high yield strength (YS = 547 ÷ 572 MPa), the tested cast steel was characterized by the following mechanical properties: UTS = 731 ÷ 750 MPa, EL = 21 ÷ 29.5%, R.A. = 43 ÷ 52%, hardness 256 ÷ 266 HB. Fractures formed in mechanical tests showed ductile-brittle character.
PL
W artykule przedstawiono mikrostrukturę i właściwości mechaniczne, kwasoodpornego staliwa ferrytyczno - austenitycznego 23Cr-5Mn-2Ni-3Mo typu duplex. Wykazano, że struktura badanego staliwa składa się z ferrytu δ wzbogaconego w C r, Mo i S i oraz austenitu wzbogaconego w Mn i Ni. W stanie wyjściowym na granicy międzyfazowej występują wydzielenia wzbogacone w C r i Mo. Wysoka zawartość C (0.08%) w tym staliwie wskazuje, że prawdopodobnie są to złożone węgliki M23C6 i/lub faza σ. Wykazano, że temperatura przesycania 1060°C nie jest wystarczająca do ich całkowitego rozpuszczenia. Natomiast w temperaturze przesycania 1150°C struktura badanego materiału składa się z ferrytu i austenitu. Częściowe zastąpienie Ni przez dwa inne pierwiastki austenitotwórcze jakimi są Mn i N zapewniło uzyskanie porównywalnych właściwości mechanicznych do staliwa duplex 24Cr-5Ni-3Mo drugiej generacji. Na podstawie przeprowadzonej statycznej próby rozciągania wykazano dwukrotnie wyższą granicę plastyczności w porównaniu do często stosowanego w przemyśle odlewniczym austenitycznego staliwa 18Cr-9Ni i 19Cr-11Ni-2Mo. Poza wysoką granicą plastyczności (Rp0,2 = 547 ÷ 572 MPa), badane staliwo charakteryzowało się następującymi właściwościami mechanicznymi: Rm = 731 ÷ 750 MPa, As = 21 ÷ 29,5%, Z = 43 ÷ 52%, HB = 256 ÷ 266. Przełomy po badaniach wytrzymałościowych wykazywały charakter ciagliwo-kruchy.
3
Content available The Microstructure of Thin-walled GX2CrNiMoN25-6-3 Cast Steel Made by Centrifugal Casting
Stradomski G., Nadolski M., Stradomski Z.
Archives of Foundry Engineering
|
2015
|
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.
4
Content available remote 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
|
2014
|
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
Content available The Role of Carbon in the Mechanism of Ferritic-Austenitic Cast Steel Solidification
Stradomski G.
Archives of Foundry Engineering
|
2014
|
Vol. 14, iss. 3
83--86
EN
The paper presents the results of research on the microstructure of GX2CrNiMoCuN25-6-3-3 and GX2CrNiMoCuN25-6-3 cast steels with a varying carbon content. 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% and with 23% Cr, 8.5% Ni, 3% Mo and 2.4% Cu. 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.
6
Content available 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
|
2012
|
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.
7
Content available remote Selected properties of new "duplex" cast steel
Pietrowski S., Gumienny G., Masalski M.
Archives of Foundry Engineering
|
2011
|
Vol. 11, iss. 4
123-130
EN
In this paper selected properties of new 'duplex' cast steel are presented. The new cast steel was devised in HYDRO-VACUUM company in Grudziądz, where 'duplex' cast steel for pump elements is smelted. The goal was to devise a new grade of 'duplex' cast steel of better physicochemical properties and cheaper than now applied. It was demonstrated, that there is the possibility of devising the new grade of 'duplex' cast steel. It is characterized by higher mechanical properties, similar wear resistance and greater corrosion resistance in 15% water solution of H2SO4 in comparison to now ap p lied 'duplex' cast steel. The chemical composition was selected to obtain in microstructure about of 50% ferrite and 50% austenite. It guarantee the highest properties and the lowest costs of its smelting. In the paper results of: the microstructure, Rm, Rp0,2, A5, HB, wear resistance and corrosion resistance in water solution of 15% HCl and H2SO4 acids of new cast steel was presented. They were compared with now applied in HYDRO-VACUUM company 'duplex' cast steel.
8
Content available remote Ferritic-austenitic cast steel - selected problems
Stradomski Z.
Archives of Foundry Engineering
|
2011
|
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.
9
Content available remote The assessment of hot cracking susceptibility of ferritic-austenitic cast iron
Stradomski Z., Soiński M. S., Stradomski G.
Archives of Foundry Engineering
|
2010
|
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.
10
Content available remote 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
|
2009
|
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.
11
Content available remote The influence of carbon and copper on the solidification process of the ferritic-austenitic cast steel
Stradomska J.
Archives of Foundry Engineering
|
2009
|
Vol. 9, iss. 3
177-180
EN
Technological problems which occur during the production of castings made of ferritic-austenitic (duplex) cast steel have caused that this most modern material among corrosion-resistant cast steels is seldom produced in Poland. The main reason of arising problems is the necessity of achieving a very low carbon content (Cmax = 0.03%, according to PN-EN 10283:2004) and the occurring of hot cracking. It is impossible for our domestic foundries to achieve such a low carbon content, because it demands for out-of-furnace treatment. It should be mentioned that the standards developed by international cast steel producers admit also cast steel grades with higher carbon content than the PN-EN 10283:2004 Standard. The so far produced in Poland massive castings have exhibited higher (0,05 - 0,12) carbon content, but also the significant hot cracking susceptibility. Is the increased carbon content along with about 3% copper addition, which lowers the temperature of the end of solidification process, the reason of hot cracking of produced castings? The paper presents the results of investigation performed by DDTA and ThermoCalc analyses, as well as by microstructural examination for duplex cast iron with varying carbon content.
12
Content available remote The analysis of solidification process of ferritic-austenitic cast steel
Stradomska J., Stradomski Z., Soiński M. S.
Archives of Foundry Engineering
|
2009
|
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.
13
Content available remote Significance of the [sigma] phase for the erosive
Stradomski Z., Soiński M. S., Stradomska J., Dyja D.
Archives of Foundry Engineering
|
2008
|
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.
14
Content available remote Optimization of heat treatment in aspect of production's costs reducing and improving of casting quality from duplex cast steel
Dyja D., Stradomski Z.
Archives of Foundry Engineering
|
2007
|
Vol. 7, iss. 3
39-42
EN
The paper determines possibilities of cost optimisation in the production of GX2CrNiMoCu25-6-3-3 type duplex cast steel castings through selection of appropriate solution heat treatment temperature, which value depends on the content of alloying elements. Metallographic analysis was carried out for as-cast and heat treated cast steel. Hardness and impact strength of the cast steel were determined, which were correlated with the volume fraction of phases determined by means of ImagePro computer image analyser. It has been shown that increased carbon content creates a need to use higher treatment temperatures, thereby increasing the production cost. With increasing carbon content the cast steel hardness after solution heat treatment increases, however, crack resistance decreases.
15
Content available remote Influence of carbon content on the segregation processes in duplex cast steel
Stradomski Z., Dyja D.
Archives of Foundry Engineering
|
2007
|
Vol. 7, iss. 1
139-142
EN
The paper aimed at determination of increased carbon content influence on segregation processes in a duplex ferritic-austenitic cast steel. The analysis of raw cast steel structure was carried out using a Zeiss Axiovert 25 optical microscope. The chemical composition of selected areas was examined using a JEOL JSM 5400 scanning microscope equipped with an EDX microanalyser and the obtained results were verified using the Thermo-Calc software. The investigations carried out have shown that the lower carbon content causes the smaller amount of the intermetallic phases precipitates undesirable in the manufacturing process, which – affecting a clear deterioration in raw cast steel impact strength – promote origination of cracks in the castings. The increased, due to segregation processes, content of carbon, chromium and molybdenum within the solidification grain boundaries promotes precipitation of carbides already in the liquid state, what increases the propensity for hot cracking. The molybdenum content, in a cast steel of increased carbon content, varies from ~4% in the centre of solidification grain to ~6.5% in its boundary areas, and the chromium content from ~28% to 32%, respectively. Small enrichment of ferrite with molybdenum and chromium in boundary areas of cast steel solidification grains containing 0.02% carbon causes higher ferrite stability and prevents its decomposition in the temperature range from 600 to 900°C, what makes that the cast steel of lower carbon content features uniform ferritic-austenitic structure in as cast state.
16
Content available remote Characterization of solidification and solid state transformation in duplex cast steel: thermo-calc investigation
Stradomski Z., Dyja D.
Archives of Foundry Engineering
|
2007
|
Vol. 7, iss. 3
269-272
EN
The paper presents a characteristic of solidification process and changes occurring in the solid state in a duplex cast steel. Theoretical chemical composition of individual phases, its changes during solidification and cooling after solidification and also changes in volume fractions of phases versus temperature have been determined. Theoretical results of Thermo-Calc analysis have been correlated with the microstructure of as-cast cast steel as well as with analysis of chemical composition of individual phases, carried out on a scanning microscope equipped with an EDS attachment. It has been shown that at the carbon content of 0.1% the enrichment of residual liquid phase with carbon results in a peritectic reaction, changing the ferritic solidification model typical for cast steels with low carbon content. In the case of solidification grain boundary areas enrichment with carbon, chromium and molybdenum there is a possibility of carbides precipitation already in the liquid state, what increases propensity for hot cracking and reduces the quality of castings produced. A correlation between theoretical composition of ferrite, austenite and M23C6 carbides, determined based on Thermo-Calc software, and their actual composition determined based on local analyses of chemical composition carried out on a scanning microscope has been shown. The volume fractions of ferrite, austenite and carbides determined using Thermo-Calc software show a strong correlation with actual fractions of those phases in the examined alloy's structure. The chemical composition of ferrite, austenite and carbides determined using Thermo-Calc software does not show any more such strong correlation with the actual chemical composition of those phases determined based on local analyses of chemical composition carried out using a scanning microscope.
17
Content available remote Ocena możliwości sterowania mikrostrukturą staliwa ferrytyczno-austenitycznego GX2CrNiMoCu25-6-3-3
Dyja D., Stradomski Z., Stachura S.
Archiwum Odlewnictwa
|
2006
|
R. 6, nr 18/1
459--464
PL
W pracy przedstawiono wpływ zawartości węgla na strukturę i wybrane własności staliwa GX2CrNiMoCu25-6-3-3 po obróbce cieplnej. Stwierdzono, że po zabiegu przesycania staliwo charakteryzuje się strukturą ferrytyczno-austenityczną, a poprzez odpowiedni dobór temperatury przesycania sterować można wzajemnym udziałem ferrytu i austenitu. Wraz ze wzrostem zawartości węgla wrasta twardość staliwa po przesycaniu, drastycznemu zmniejszeniu ulega jednak odporność na pękanie.
EN
The effect of carbon content on the structure, hardness and impact resistance of GX2CrNiMoCu25-6-3-3 cast steel was discussed. After the solution heat treatment the cast steel have a ferritic-austenitic two-phase structure, and one of the main purposes of solutioning is to obtain the required amount of ferrite and austenite in the structure. Testing results show that an increase of carbon content improves the hardness, with its increase being accompanied by decrease in impact resistance.
18
Content available remote Model krzepnięcia wysokostopowych staliw Fe-Cr-Ni
Dyja D., Stradomski Z.
Archiwum Odlewnictwa
|
2006
|
R. 6, nr 19
81-88
PL
W pracy przedstawiono ogólne modele krzepnięcia wysokostopowych, odpornych na korozję staliw Fe-Cr-Ni ze szczególnym uwzględnieniem mechanizmu krzepnięcia ferrytyczno-austenitycznych staliw typu duplex. Na podstawie badań własnych wykazano, że zjawiska mikrosegeracji, szczególnie węgla, chromu i molibdenu do granic pierwotnego ziarna krzepnięcia, zmieniają mechanizm krzepnięcia z ferrytycznego na ferrytyczno-austenityczny, a obecność reakcji perytektycznej negatywnie wpływa na własności technologiczne, zwiększając skłonność do pękania na gorąco. Przeprowadzone w pracy badania makro i mikrostruktury oraz mikroanalizy składu chemicznego staliw w stanie surowym, o zróżnicowanej zawartości węgla, ujawniły możliwość wydzielania się węglików pierwotnych już z cieczy. Uprzywilejowane rozmieszczenie węglików w obszarach przygranicznych pierwotnego ziarna krzepnięcia w połączeniu z występującym w niższych temperaturach wydzielaniem się fazy \sigma zwiększa niebezpieczeństwo powstania pęknięć w wolno stygnących odlewach.
EN
The general solidification models of highly alloyed, corrosion resistant Fe-Cr-Ni cast steel, together with the particular consideration of ferritic-austenitic duplex cast steels were shown in the work. On the basis of personal investigations it was shown, that microsegregation especially of carbon, chromium and molybdenum to the primary solidification grain boundaries, changes the solidification mechanism from ferritic to ferritic-austenitic. The presence of peritectic transformation has a negative effect on technological properties, increasing the hot crack sensitivity . Macro and microstructure examinations and chemical composition microanalysis of the cast steel at as-cast condition with various carbon content , revealed the possibility of primary carbide precipitation from the liquid. Privileged distribution of carbides in the primary solidification grain boundaries, in connection with sigma phase precipitation occurred at the lower temperatures increases danger of cracking in low-cooling castings.
19
Content available remote Technologiczne problemy wytwarzania masywnych odlewów ze staliwa duplex w aspekcie optymalizacji procesu produkcyjnego
Stradomski Z., Stachura S., Dyja D., Zyska A.
Archiwum Odlewnictwa
|
2005
|
R. 5, nr 17
287--292
PL
W pracy przedstawiono problemy wykonywania masywnych, 2-3 tonowych, odlewów ze staliwa typu duplex. Badaniom poddano odlewy w stanie surowym, o zmiennej zawartości węgla. Wykazano, że nawet niewielkie różnice w jego zawartości, znacząco wpływają na tworzenie się obszarów segregacyjnych związanych z występowaniem cieczy resztkowej w czasie krzepnięcia. Obszary te charakteryzują się znaczną koncentracją węglików oraz fazy sigma i są miejscem uprzywilejowanego tworzenia się pęknięć dyskwalifikujących odlewy.
EN
Problems related with production of massive, 2-3 tone-castings of duplex cast steel have been presented in this work. Castings in the as-cast conditions, with the variable carbon content from 0,05% to 0,11% have been investigated. Using the material with the various carbon contents, the authors proved, that even small differences in their contents have significant role in segregation area, connected with occurrence of the residual liquid during solidification. These areas have the large carbides and sigma phase concentrations, they are also the privileged places for origination of the cracks, what disqualify the cast.
20
Content available remote Solidification structure of massive castings from duplex cast steel
Dyja D., Stradomski Z., Stachura S.
Archiwum Odlewnictwa
|
2005
|
R. 5, nr 15
79--86
EN
Problems related with duplex massive cast production are presented in this work. Macro and microstructure investigations of GX2CrNiMoCu25-6-3-3 cast steel after solidification were done. The influence of cooling rates and segregation on intermetallic phases formation, especially sigma phase, were shown. The segregation process and cooling rates during solidification have great influence on intermetallic phases formation. Sigma phase occurrence in the cast structure causes deterioration of technological and functional properties.
PL
W pracy przedstawiono problemy wykonywania masywnych odlewów ze staliwa typu duplex. Przeprowadzono badania makro- i mikrostruktury krzepnięcia staliwa GX2CrNiMoCu25-6-3-3. Opisano wpływ szybkości chłodzenia i segregacji pierwiastków na tworzenie się faz międzymetalicznych, zwłaszcza fazy sigma. Badania wykazały, że proces segregacji pierwiastków stopowych oraz warunki chłodzenia podczas krzepnięcia silnie wpływają na tworzenie się faz międzymetalicznych, a ich wydzielanie w strukturze powoduje pogorszenie własności technologicznych i użytkowych odlewów.
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