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1

Effect of copper on strain-induced martensite and the parameters that simulate the stress-strain curve of an austenitic stainless steel AISI 304

Gilapa L C M, Oliveira C A S, Silva M R

Journal of Achievements in Materials and Manufacturing Engineering

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2012

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Vol. 55, nr 2

679--684

EN

Purpose: This study examined the effect of copper on the phase transformation (γ → a')-induced by the deformation and in the variables of the equation that simulates the stress- equivalent strain curve. Design/methodology/approach: The phase transformation (y → a') was studied through the magnetic properties using a vibrating sample magnetometer - VSM. The simulation of the stress-equivalent strain curve was performed using the obtained results in experimental studies, using the commercial software Maple. Findings: It was observed that the addition of copper in the austenitic stainless steel (ASS) AISI 304 promotes increased stability of the austenite, slowing therefore, the formation of martensite induced by deformation. It was also observed that the addition of copper influences on the values of the variables of the equation that simulate the stress-equivalent strain curve. Research limitations/implications: The stress-equivalent strain curve was simulated satisfactorily, however it was observed that the equation that simulates the curve displays values of the variables not usually found, this may be due to the approximations made in applying the rule of mixtures. Practical implications: It was observed that with the increase of copper, the ASS tend to increase the stability of the austenitic phase, which implies a delay in hardening of the material and a probable influence on the variables of the equation that simulates the stressequivalent strain curve. Originality/value: The influence of copper on the formation of magnetic martensite (a') and consequent influence in obtaining the variables of the equation that generates the stress-equivalent strain curve.

2

Pękanie na gorąco stali nierdzewnych austenitycznych z dodatkiem miedzi

Ziewiec A.

Hutnik, Wiadomości Hutnicze

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2012

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Vol. 79, nr 7

476--482

PL

W artykule przedstawiono wyniki badań skłonności do pęknięć gorących stali nierdzewnej austenitycznej 304HCu. Stal została poddana próbie pękania gorącego. Ustalono, że stal 304HCu wykazuje bardzo dużą skłonność do pęknięć zarówno krystalizacyjnych, jak i segregacyjnych. Przeprowadzono badania SEM z obszaru powstałych pęknięć po próbie. Zaobserwowano, że w miejscach pęknięć występuje dwukrotnie większa zawartość miedzi w stosunku do wartości średniej w badanej stali.

EN

This work presents the studies of susceptibility to hot cracking in 304HCu austenitic stainless steel. The steel was subjected to hot cracking test. It was found that the 304HCu steel has a very high susceptibility both to crystallization crack and segregation cracks. The SEM observations of the cracks after the cracking test were performed. It was observed that concentration of copper in the regions of cracks is twice as much than the average concentration of copper in the steel.

3

SCC of cold-worked austenitic stainless steels in PWR conditions

Raquet O., Herms E., Vaillant F., Couvant T.

Advances in Materials Science

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2007

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Vol. 7, nr 1(11)

33-46

EN

A strong susceptibility for SCC of heavily cold worked austenitic stainless steels is observed in hydrogenated primary water typical of PWRs. This susceptibility to cracking increases with the extent of cold-work and/or localization of deformation. The levels of cold-work involved in this study are very high when compared to the maximum cold-work levels required by the usual international codes relevant to PWRs (ASME and RCC-M). These high values of cold-work could be eventually encountered on the surface of same components (grinding) or in the case of improper manufacturing. The specific cold-work procedures including a compressive stage (fatigue, shot-peening) strongly favors SCC susceptibility in PWRs conditions under dynamic deformation. For a given cold-working procedure, SCC susceptibility of austenitic stainless steels materials increases with an increasing intensity of cold-work. A threshold of SCC susceptibility was identified in the ease of the shot-peening procedure of cold-working for AISI 304L stainless steels through the value of the initial surface hardness before SCC testing (CERT). SCC crack propagation is thus only observed beyond 300+-10HV on shot-peened specimens.

4

Effect of hydrogen on adhesion of stainless steel to structural steel in explobond clad plates

Lubińska K., Szummer A., Szpila K., Kurzydłowski K.J.

Advances in Materials Science

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2007

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Vol. 7, nr 1(11)

147-152

EN

Clad plates are usually made of carbon or law alloy steel plates with a thinner layer of stainless steels which offer resistance to different corrosive environments containing hydrogen, in diverse industries like chemical, offshore, petrochemical, petro-leum refineries, nuclear, etc. It is well known that hydrogen deteriorates structure and properties of stainless steels and law alloy steels as well. In the case of clad steels, hydrogen may induce underclad cracking. In this work the results are presented of the study of the influence of hydrogen on adhesion of austenitic stainless steel to the law alloy steel in explobond clad plates. Specimens were destructively tested in band shear test. Light and scanning electron microscopy were used for examination of the shear fracture surface. It was shown that hydrogen significantly lowers a shear strength of bonding between austenitic stainless steel flyer and parent law alloy steel.

5

Forming limits of austenitic stainless steel sheets

Korhonen A., Manninen T., Kanervo K.

Computer Methods in Materials Science

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2006

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Vol. 6, No. 3-4

178-187

EN

The forming limits of austenitic stainless steel sheets were studied. It was found that the observed limit of straining in stretch forming, when both of the principal stresses are positive, is not set by localized necking, but instead by shearing fracture in the through thickness direction. Thus, the Marciniak-Kuczynski type of analysis, which has recently been successfully applied to both low-carbon steels and aluminum, may not apply to austenitic stainless steels. It appears that the forming limits of austenitic stainless steels may be predicted fairly well by using the classical localized and diffuse necking criteria developed by Hill. The fracture criterion of Ritchie and Thompson seems to overestimate the fracture limit. Better models are needed for the work hardening and to develop better limit strain criteria, since the work hardening seems to depend strongly on both strain rate and temperature. The formability of austenitic stainless steels appears to remain good even when coated with hard TiN, although unavoidable cracks will appear with continuing straining.

PL

Przedmiotem pracy jest odkształcalność graniczna stali austenitycznych. Zaobserwowano, że odkształcalność przy dwuosiowym rozciąganiu, gdy dwa naprężenia główne są dodatnie, nie jest wyznaczana przez lokalne tworzenie się szyjki, ale przez pękanie wywołane przez ścinanie w kierunku grubości blachy. Dlatego metoda Marciniaka-Kuczynskiego, która jest z powodzeniem stosowana do stali nisko-węglowych i aluminium, może nie stosować się do stali austenitycznych. Okazuje się, że odkształcenia graniczne stali austenitycznych mogą być poprawnie przewidywane przez zastosowanie opracowanego przez Hilla klasycznego kryterium lokalizacji i rozprzestrzeniania się szyjki. Kryterium pękania Ritchie-Thompsona wydaje się przeszacowywać granicę pękania. Ponieważ umocnienie zależy mocno od prędkości odkształcenia i temperatury, lepsze modele są potrzebne do opisu umocnienia i opracowania poprawnego kryterium granicznych odkształceń. Odkształcalność graniczna stali austenitycznej utrzymuje się na dobrym poziomie nawet wtedy, gdy stal jest pokryta TiN, chociaż nieuniknione pęknięcia pojawią się w czasie odkształcenia.