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1

Microstructure evolution and mechanical properties of underwater dry welded metal of high strength steel Q690E under different water depths

Sun Kun, Huc Yu, Shi Yonghua, Liao Baoyi

Polish Maritime Research

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2020

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nr 4

112--119

EN

Q690E high strength low alloy (HSLA) steel has been intensively applied in maritime engineering. Also, the underwater dry welding (UDW) technique has been widely used to repair important offshore facilities. In this paper, joints of Q690E steel were fabricated through single-pass underwater dry welding at three pressures (0, 0.2, and 0.4 MPa). To study the effect of the pressure on the microstructure and mechanical properties of the UDW joint, an optical microscope (OM) and scanning electron microscope (SEM) were used to observe the microstructure and fracture morphology of the welded joints. The electron backscattered diffraction (EBSD) technique was used to analyse the crystallographic features and the crystallographic grain size of the ferrites. The proportion of acicular ferrite (AF) in the UDW joints and the density of low-angle boundaries increase dramatically with the increasing depth of water. The weld metal of UDW-40 shows higher strength because more fine ferrites and low-angle boundaries within UDW-40 impede the dislocation movement.

2

Model kinetyki wydzielania węglikoazotków w stalach mikrostopowych

Adrian H., Augustyn-Pieniążek J., Marynowski P., Matusiewicz P

Hutnik, Wiadomości Hutnicze

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2014

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Vol. 81, nr 4

208--214

PL

W artykule przedstawiono model kinetyki wydzielania węglikoazotku M(C, N) w stali mikrostopowej zawierającej dodatek Ti, Nb lub V. Model jest oparty na klasycznej teorii zarodkowania (ogólny model Kampmanna i Wagnera [1]) i pozwala obliczać rozkład wielkości wydzieleń w austenicie lub ferrycie w warunkach izotermicznego wytrzymywania stali przy temperaturze Tw, poddanej wcześniej przesycaniu o wysokiej temperaturze Tp. Opisano opracowany program komputerowy CarbNit_kinet oraz przedstawiono przykład wyników obliczeń dla stali zawierającej 0,2 %C, 0,01 %N i 0,15 %V.

EN

Model of kinetics of carbonitride M(C, N) precipitation in HSLA steel containing microalloying element Ti, Nb or V is presented. The model is based on classical theory of nucleation (general model of Kampmann and Wagner [1]). It enables to calculate the size distribution of carbonitrides precipitation in austenite or ferrite during isothermal holding at temperature Tw of microalloyed steel after previous heating at high austenitising temperature Tp. An example of application of developed computer program, CarNit_kinet for carbonitride precipitation in steel containing 0.2 %C, 0.01 %N and 0.15 %V is presented.

3

Some aspects of continuous casting of low carbon microalloyed steels with niobium and titanium

Derda W., Wiedermann J.

Archives of Metallurgy and Materials

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2012

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Vol. 57, iss. 1

303-310

EN

An analysis of the causes of transverse corner and surface crack formation during continuous casting of low carbon niobium and titanium-containing steel into square billets is presented in this paper. Using X - ray analysis method, the chemical composition of non- metallic phases inside corner cracks was determined. The temperature ranges of the occurrence of nitrides and carbonitrides of Nb, Ti and Al were established using FactSage 6.2., a commercial computer program. The need for the precise selection of cooling conditions during casting of billets both in the mould and in spray cooling regions was pointed out with the aim of obtaining the optimum surface, and particularly corner temperature of the billet before its entrance to the straightening stand.

PL

W referacie przedstawiono na podstawie badań w warunkach przemysłowych, analizę przyczyn powstawania pęknięć na powierzchni i na narożach wlewków ciągłych o przekroju kwadratowym, odlewanych ze stali niskowęglowych z zawartością niobu i tytanu. Przy użyciu metody mikroanalizy rentgenowskiej dokonano oceny składu chemicznego faz niemetalicznych występujących wewnątrz pęknięć. Z wykorzystaniem programu komputerowego FactSage 6.2 wyznaczono zakresy temperatury występowania azotków i węglikoazotków Nb, Ti, Al. Wskazano na konieczność precyzyjnego doboru warunków chłodzenia odlewanych stali w krystalizatorze oraz w strefie chłodzenia natryskowego celem uzyskania optymalnej temperatury wlewka ciągłego w szczególności na narożach przed operacją jego prostowania w klatce walców ciągnąco - prostujących.

4

Resistance to cold cracking of welded joints made of P460NL1 steel

Kozak T.

Advances in Materials Science

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2011

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Vol. 11, nr 3(29)

20-27

EN

The results of investigations of resistance to cold cracking of high strength steel welded joints have been presented. The steel used was P460NL1 which is designed to work under pressure. Welding was carried out with coated electrodes (MMA) and flux cored wire by FCAW method. Parameters changed in the implant test were diffusible hydrogen content and weld heat input. Partial resistance to cold cracking of joints for the studied ranges of welding parameters have been shown. Cold cracking resistance decreases with increasing diffusible hydrogen content in the joint and increasing the cooling rate in the HAZ metal measured by cooling time in the temperature range 800-5000C.

5

Numerical simulation of the hydraulic bulge test of HSLA steel and experimental verification of results

Slota J., Gajdos I.

Zeszyty Naukowe Politechniki Rzeszowskiej. Mechanika

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2010

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z. 81 [277]

67-72

EN

In sheet metal forming operations the mechanical properties of the sheet metal (stress-strain curve, flow stress) greatly influence metal flow and product quality. Accurate determination of the stress-strain relationship is important in process simulation by finite element method. In this paper the sheet thickness gradation in different points of the hemisphere formed in the bulge test is analyzed, both by simulation and experimentally. A precise determination of sheet thickness at the pole is very important in the precise determination of stress-strain relationship. The aim of this paper is to show on some aspects of numerical simulation of hydraulic bulge test and experimental verification of obtained results.

6

The effect of nitrogen and vanadium on hardenability of medium carbon 0.4 %C and 1.8 %Cr steel

Adrian H., Staśko R.

Archives of Materials Science and Engineering

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2008

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Vol. 33, nr 2

69-74

EN

Purpose: To investigate the effect of V and N on hardenability of steel containing 0.4 % C and 1.8 % Cr. Design/methodology/approach: Four laboratory melts with different N and V contents were used. Hardenability of steel was investigated using standard Jominy test and Grossmann analytical method. The effect of calculated undissolved carbonitride V(C,N) content on austenite grain size was investigated. Findings: Nitrogen addition without microalloying elements increased the austenite grain size. Very high hardenability was obtained in steel containing 0.004 %N and 0.08 %V at 870°C. Addition of 0.08 %V at elevated nitrogen content significantly decreased the grain size and at 870°C increased the hardenability of steel. Practical implications: Investigated steel showed very high hardenability with ideal critical diameter DiJ approximately 200 mm, at appropriate austenitizing temperature. Higher nitrogen content in steel with vanadium addition retards austenite grain growth in broad austenitizing temperature range. Originality/value: Results of investigations provide valuable information on the effect of vanadium and nitrogen content on the hardenability of quenched and tempered steel with 1.8 % Cr. Thermodynamic calculations enable to select the optimum austenitizing temperature range.

7

Wpływ mikrostruktury stali niskostopowych o wysokiej wytrzymałości na ich spawalność

Ćwiek J., Łabanowski J.

Inżynieria Materiałowa

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2003

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R. XXIV, nr 6

709-711

PL

Mikrostruktura stali niskostopowych o wysokiej wytrzymałości wpływa na skłonność do pęknięć zimnych ponieważ ma wpływ na hartowność i twardość maksymalną strefy wpływu ciepła (SWC). Dwa gatunki stali o wysokiej wytrzymałości 18G2AV i 14HNMBCu, w różnych stanach obróbki cieplnej, zostały poddane symulowanym cyklom cieplnym spawania. Maksymalna twardość SWC zależna jest od rodzaju mikrostruktury przed cyklem cieplnym spawania. Najwyższą twardość w SWC obserwowano dla stanu ulepszonego cieplnie w porównaniu ze stanem wyżarzonym zupełnie i przegrzewająco.

EN

Microstructure of steel before welding has influence on the steel's susceptibility to cold cracking because it influences hardenability and maximum hardness of heat affected zone (HAZ). Two high-strength low-alloy (HSLA) steel grades 18G2AV and 14HNMBCu, in various heat treatment conditions, were subjected to simulated welding thermal cycles. It has revealed that maximum HAZ hardness is influenced by microstructure presented before thermal cycle was applied. The higher HAZ hardness was observed for quenched and tempered condition, comparing to full annealed and overheated conditions.