Microstructure and mechanical properties of forged and rolled rings made from X20Cr13 steel

The article describes the results of microstructure and mechanical properties tests (according to PN-EN ISO 6892- 1:2016-09 and PN-EN ISO 6507-1:2007), which were obtained on specimens taken from a fragment of a ring rolled in the temperature range from 1220 °C to 950 °C, with dimensions ø965/803 x 164 mm, annealed and heat-treated: quenching at the temperature of 1 030 ± 10 °C in oil and tempering at a temperature of 650 °C. The starting material for rolling was a forging with an opening of ø560/230 x 180 mm. Comparative hardness tests were also performed on specimens taken from the ring after rolling and softening annealing. The Rm>/sub>, Rp0.2 and A indices of the ring fragment after heat treatment, as assumed, were respectively: 942 MPa, 763 MPa and 17 %

Ewaluation and analysis of the large-size forged and rolled en AW – 7057 alumminum alloy ring structure

The article presents the results of tests on the structure and hardness of a large-size ring made of EN AW - 7075 aluminium alloy produced under industrial conditions at the Zarmen FPA forge according to the developed technology - a combined forging and rolling method. Studies of the ring were carried out in order to assess its structure and hardness after the forming processes. The scope of the study included microscopic observations (microstructure and EDS), X-ray phase analysis and hardness distribution measurements

Evaluation of strength parameters and structure analysis of an EN AW - 7075 aluminium alloy ring made by forging and rolling and heat-treated

The article presents the results of research on the evaluation of the structure and mechanical properties of a largesize ring made of aluminum alloy EN AW - 7075 according to a new technology, developed under the project “Innovative low-waste technology for forming large-size rings” carried out by Zarmen FPA forge with participation and support of the Lukasiewicz Research Network - Poznan Institute of Technology. Based on the tests, it was found that the produced ring was characterized by a homogeneous structure and the strength properties required by the customers

Application of the eddy current method in the investigation of heat treated NC11LV steel

W artykule przedstawiono wyniki oceny zmian struktury stali NC11LV, obrobionej cieplnie w różnych warunkach tzn. hartowanej z temperatury 1020 i 1150 C oraz odpuszczonej po hartowaniu w zakresie temperatury 180÷575 C, na podstawie badań metodą prądów wirowych przy częstotliwości prądu magnesującego 0,5 kHz (przyrząd Wirotest 03) i 50 kHz (przyrząd Wirotest 301). Strukturę próbek dokumentowano za pomocą mikroskopu świetlnego ECLIPSE L150 oraz mikroskopu skaningowego VEGA TC - dla wybranych próbek. Zawartość austenitu szczątkowego określono metodą rentgenowską. Wskazania przyrządów wiroprądowych odniesiono do zmian twardości HRC próbek hartowanych z obu temperatur i odpuszczonych oraz zmian zawartości austenitu szczątkowego próbek hartowanych z wyższej temperatury i odpuszczonych. W badaniach stwierdzono liniowy charakter zmian wskazań przyrządu wiroprądowego (przy częstotliwości 50 kHz) od zawartości austenitu szczątkowego w próbkach hartowanych z temperatury 1150 C i odpuszczonych w zakresie temperatury 180÷575 C. Pozwala to rekomendować metodę prądów wirowych do określania zawartości austenitu szczątkowego w stalach narzędziowych.The work presents the results of the assessment of structure changes of NC11LV steel as heat treated under various conditions, i.e. quenched from 1020 and 1150 ?C and tempered after quenching within the temperature range of 180÷575 ?C, based on the investigation by the eddy current method with the magnetizing current frequency of 0.5 kHz (Wirotest 03 device) and 50 kHz (Wirotest 301 device). The structure of the samples has been recorded by means of an ECLIPSE L 150 optical microscope and a VEGA TC scanning Microscope - for selected samples. The content of retained austenite has been determined by the x-ray method. The indications of the eddy current devices have been related to the changes of the HRC hardness of the samples quenched from both temperatures and tempered, as well as to the changes of the retained austenite content of the samples quenched from the higher temperature and tempered. Practical application of the eddy current method for quality assessment of the investigated steel structure can generate some difficulties only in the case of samples in which the effect of secondary hardness takes place during tempering. The investigation has shown linear character of the eddy current device indication changes (at the frequency of 50 kHz) depending on the content of retained austenite in the samples quenched from 1150 ?C and tempered within the range of 180 ÷575 ?C. This allows us to recommend the eddy current method for determining the retained austenite content in tool steels

36HNM and 38HMJ toughened steel structure assessment by the eddy current method

W pracy przedstawiono wyniki oceny zmian struktury ulepszonych cieplnie stali 36HNM i 38HMJ na podstawie kontroli ich twardości, za pomocą przyrządu Wirotest 03 i czujnika stykowego przy częstotliwości prądu magnesowania 0,5 kHz. Próbki hartowano wg zaleceń podanych w normach: PN-EN 10083-1+A1:1999 i PN-EN 10085:2003. Odpuszczanie próbek wykonano w zakresie temperatury 180÷650°C. Strukturę próbek dokumentowano za pomocą mikroskopu świetlnego ECLIPSE L150. Pomiary twardości próbek wykonano metodą Rockwella HRC wg normy PN-EN ISO 6508-1:2002 za pomocą twardościomierza FR-3ATL (Future-Tech Corp.). Praktyczne stosowanie metody prądów wirowych do jakościowej oceny struktury badanych stali ograniczone jest do próbek hartowanych i odpuszczonych w zakresie niższych temperatur do ok. 400÷450 °C z powodu zmniejszania się przenikalności magnetycznej tych stali wskutek zwiększenia udziału objętościowego węglików i procesu ich koagulacji w temperaturach powyżej 500 °C.The paper presents the results of structure change assessment in 36HNM and 38HMJ toughened steels based on the check of their hardness by means of the Wirotest 03 device and a contact sensor with the magnetizing current frequency of 0.5 kHz. Samples were hardened as per the recommendations stated in the standards: PN-EN 10083-1+A1:1999 and PN-EN 10085:2003. Toughening of the samples was effected within the temperature range of 180¸650°C. The sample structure was documented by means of a metallurgical microscope ECLIPSE L150. Hardness measurements were performed by the Rockwell method, HRC, acc. to standard PN-EN ISO 6508-1:2002 by means of a FR-3ATL hardness tester (Future-Tech Corp.). The practical application of the eddy current method for qualitative assessment of the steel structures is limited to samples hardened and toughened within a lower temperature range of about 400¸450°C due to the decrease of the magnetic permeability of those steels as a result of the increase of volumetric content of carbides and the process of their coagulation at the temperatures above 500°C

Application of the Wirotest 301 apparatus for examination of the thickness of iron nitride zone on WCL steel

W pracy przedstawiono wyniki badań grubości strefy azotków na stali WCL, metodą prądów wirowych przy częstotliwości prądu magnesowania 0,5 i 1 MHz. W badaniach zastosowano przyrząd Wirotest 301 i czujnik ekranowany oraz nieekranowany. Próbki azotowano gazowo w temperaturze 540 °C w czasie od 4 do 40 godz. przy potencjale azotowym Np = 3,6 atm-1/2 oraz w temperaturze 500 °C w ciągu 22, 48 i 76 godz. przy potencjale Np = 14,2 atm-1/2. Badania przeprowadzono również na próbkach ze stali WCL, których grubości stref azotków określono metodą metalograficzną podczas wcześniej prowadzonych badań. Próbki azotowane w niższej temperaturze różniły się twardością po ulepszaniu cieplnym. Wykazano, że związek średnich wskazań przyrządu Wirotest 301 W od grubości strefy azotków ge+g próbek azotowanych w temperaturze 500 °C można opisać regresją liniową, a współczynniki R2 wyniosły ok. 0,95 dla obu użytych czujników. Analogiczny związek W = f(ge+g) dla próbek azotowanych w temperaturze 540 °C najlepiej opisuje funkcja wielomianowa drugiego stopnia, której współczynnik R2 osiągnął najwikszą wartość, gdy próbki badano czujnikiem ekranowanym. Twardość próbek w zakresie 45-51 HRC, w stanie ulepszonym cieplnie, nie wpływa istotnie na proces azotowania i tym samym na grubość strefy azotków. Opisana metodyka badań może być stosowana do oceny grubości warstw azotków na azotowanych wyrobach. Istotny jest dobór czujnika o polu detekcji dostosowanym do wielkości badanego wyrobu oraz przeprowadzenie badań wstępnych określających zależność wskazań W od grubości badanej fazy e, e+gc lub gc przy różnych częstotliwościach prądu magnesującego.The paper presents the results of the examination of nitride zone thickness on WCL steel by the eddy current method with the magnetizing current frequency of 1 and 0.5 MHz. In the examinations, the Wirotest 301 apparatus and a screened and unscreened sensor have been used. The samples were gas nitrided at 540°C for 4 to 40 hours with the nitrogen potential of Np = 3.6 atm-1/2 and at 500°C for 22, 48 and 76 hours with the potential of Np = 14.2 atm-1/2 . Tests have also been performed on WCL steel samples whose nitride zone thickness has been determined by the metallographic method during earlier examinations. Samples nitrided at a lower temperature differed in their hardness after toughening. It has been shown that the dependence of the average indications of the Wirotest 301 apparatus on the thickness of the nitride zone, ge+g, of the samples nitrided at 500°C can be described with a linear regression and the R2 coefficients were about 0.95 for both sensors used. An analogous relationship of W = f(ge+g ) for the samples nitrided at 540°C is best described by the polynomial function of the second order whose R 2 coefficient has reached its largest value when the samples were examined with the screened sensor. The sample hardness in the range of 45-51 HRC in the toughened condition does not significantly influence the nitriding process and, consaquently, the thickness of the nitride zone. The examination methodology described can be applied to estimate the thickness of the nitride layers on nitrided products. An important thing is the choice of a sensor with the detection field adapted to the side of the object under examination as well as the performance of preliminary examinations determining the dependence of the W indications on the thickness of the examined phase e, e +g’ or g’ at various frequencies of the magnetizing current

Investigation of the influence of surface roughness after gas nitriding on the indications of the eddy current device

W artykule przedstawiono wyniki badań parametrów chropowatości powierzchni stali 38HMJ i Orvar Supreme azotowanych w temperaturze 550 oC w czasie 2, 9, 23 i 48 godzin przy potencjale azotowym Np = 2,9-2,4 atm-0,5. Grubość efektywną warstwy azotowanej oceniono na podstawie profili mikrotwardości HK 0,1 - przyjęto twardość 500 HK 0,1 dla stali 38HMJ oraz 700 HK 0,1 dla stali Orvar Supreme. Grubość strefy azotków Selaza wyznaczono na podstawie badań metalograficznych za pomocą mikroskopu optycznego. Wykazano, Se zwiększenie czasu azotowania powoduje nieznaczne zwiększenie parametrów Rt i Rz. W wyniku przeszlifowania próbek azotowanych nastąpiło zwiększenie amplitudy wskazania przyrządu wiroprądowego (Wirotest 302 wyposażony w czujnik stykowy o częstotliwości prądu magnesującego 50 kHz) wskutek zmniejszenia chropowatości powierzchni, usunięcia warstewki tlenków żelaza i strefy porowatej azotków żelaza.The paper presents the results of investigation roughness parameters of 38HMJ and Orvar Supreme steels nitrided at the temperature of 550 oC for 2, 9, 23 and 48 hours with the nitrogen potential of Np = 2.9–2.4 atm-0.5. The effective thickness of the nitrided layer has been assessed basing on the microhardness profiles, HK 0.1 – the hardness of 500 HK 0.1 has been adopted for the 38HMJ steel and 700 HK 0.1 for the Orvar Supreme. The thickness of the iron nitride zone has been determined basing on metallographic examination by means of an optical microscope. It has been shown that extension of the nitriding time results in a slight increase of the Rt and Rz parameters. As a result of grinding of the nitrided samples, the amplitude of the eddy current device indications has increased (Wirotest 302 device provided with a sensor with the magnetizing current frequency of 50 kHz) due to the reduction of the surface roughness, removal of the layer of iron oxides and the porous zone of iron nitrides

Investigation of internal stresses in iron nitride zones of nitrided layers on 38HMJ and WCL steels

The paper presents the results of stress measurements performed by the sin2? x-ray method in nitrided layers of 38HMJ and WCL steels. The measurements have been carried out on steels whose structure and microhardness distribution had been assessed during previously performed works. Those works concerned steels with a two-zone layer of nitrides, ?+?', and a precipitation zone, ?, under the nitride zone. Additional investigation has been performed, too, on steels which had been gas nitrided at the temperature of 550 oC and nitrogen potential, Np = 1 atm-0.5 in order to obtain a one-phase layer of iron nitrides. Investigation of ?? stresses in both steels have shown that, in phase ? of zone ?+?', the stresses changed from compression stresses with maximum value of about -200 MPa to maximum tensile ones of about 220 MPa when the time of nitriding was increased from 2 hours to about 50 hours for the processes performed under the conditions of 550 oC and Np = 4 atm-0.5 also 500 C and Np = 14 atm-0,5. In the one-phase zone, ?', of the WCL steel compression stresses have been found to increase from about -120 MPa to -760 MPa when the time of nitriding was extended from 16 hours to 43 hours under the conditions of 550 oC and Np = 1 atm-0.5. In the layer compounds being a mixture of phases ? and ?' of the 38HMJ steel, compression stresses have also been obtained; the larger of those amounting over -900 MPa where found in phase ?' after the longest nitriding time under the same conditions