Additional Recommendations for Welding Cr-Mo-V Steels for Petrochemical Applications

Chovet, Corinne; Schmitt, Jean-Paul

doi:10.1007/bf03321540

Cited by 9 publications

(10 citation statements)

References 1 publication

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“…Literature regarding low-alloyed 2.25Cr-1Mo-0.25V weld metal and steel deals a lot with challenges concerning joining, post weld heat treatment, creep damage and repair issues [3,[26][27][28][29][30][31][32] as well as the evolution of carbides during heat treatment [33][34][35]. As a result, only little precise information about the evolution of microstructure in the course of phase transformation and the final microstructure constituents is available.…”

Section: Cooling Ratementioning

confidence: 99%

“…The heat-resistant V-modified 2.25Cr-1Mo-0.25V-alloy was developed following the conventional low-alloyed 2.25Cr-1Mo steel and approved as ASME Code Case 2098-1 in 1991 [1,2]. 2.25Cr-1Mo-0.25V-alloy is commonly used in the petrochemical industry where it is applied to hydrocracking reactors as well as heavy wall pressure vessels for high-temperature hydrogen service [1,3]. Compared to the base alloy 2.25Cr-1Mo, the V-modified alloy can withstand higher stresses, which made a reduction of reactor wall thicknesses in combination with higher operating temperatures possible, thus leading to better efficiency [1,3].…”

Section: Introductionmentioning

confidence: 99%

“…2.25Cr-1Mo-0.25V-alloy is commonly used in the petrochemical industry where it is applied to hydrocracking reactors as well as heavy wall pressure vessels for high-temperature hydrogen service [1,3]. Compared to the base alloy 2.25Cr-1Mo, the V-modified alloy can withstand higher stresses, which made a reduction of reactor wall thicknesses in combination with higher operating temperatures possible, thus leading to better efficiency [1,3]. In 1995, the Italian company Nuovo Pignone was the first to fabricate a reactor from 2.25Cr-1Mo-0.25V-alloy in Europe, finally leading to the manufacturing of more than 90 further reactors by the end of 2001 [1].…”

Section: Introductionmentioning

confidence: 99%

“…Beside the listed benefits, the application of 2.25Cr-1Mo-0.25V-alloy entails some disadvantages too. These include low toughness levels in as-welded condition before post weld heat treatment and a higher susceptibility to reheat cracking compared to the conventional Cr-Mo grade [3,4]. Regarding the application in hydrotreating reactors, 2.25Cr-1Mo-0.25V weld metal has to withstand combinations of hydrogen partial pressures up to 13.79 MPa and temperatures up to 482°C to avoid hydrogen attack [2,5,6].…”

Section: Introductionmentioning

confidence: 99%

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Microstructural evolution of 2.25Cr-1Mo-0.25V submerged-arc weld metal

et al. 2019

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Heat-resistant V-modified 2.25Cr-1Mo-0.25V-weld metal is commonly used in petrochemical industry for heavy wall pressure vessels in high-temperature hydrogen service. In order to improve the reactor efficiency, the weldments have to endure even higher temperatures and pressures. Acicular ferrite (AF) is often regarded as the optimum microstructure due to its good combination of strength and toughness. As few literature about the evolution of microstructure and the final microstructure constituents of 2.25Cr-1Mo-0.25V weld metal is available, the current paper intends to provide comprehensive information by means of microscopy, crystallographic examination via electron backscatter diffraction and in situ observation of the austenite to ferrite phase transformation via high-temperature laser scanning confocal microscopy (HT-LSCM). The investigated weld metal exhibits a high density of complex aluminium-silicon-manganese oxides with a spherical shape and large prior austenite grains, which in combination is beneficial for intragranular nucleation of AF. Nonetheless, the examination of the transformed final microstructure was not sufficient to make an unambiguous statement about the presence of AF within the 2.25Cr-1Mo-0.25V weld metal. Via in-situ HT-LSCM of the phase transformation, intragranular nucleation of AF at non-metallic inclusions within the austenite grains was detected, which confirms that even though the microstructure of 2.25Cr-1Mo-0.25V weld metal is mainly bainitic, small amounts of AF are present.

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Section: Cooling Ratementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Microstructural evolution of 2.25Cr-1Mo-0.25V submerged-arc weld metal

et al. 2019

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“…In comparison to the basic alloy 2.25Cr-1Mo, the V-modified alloy shows several advantages such as an increased resistance to hydrogen embrittlement, a better resistance to overlay disbonding and a good toughness in combination with high levels of mechanical properties at elevated temperatures [3][4][5]. Since 1995, when the Italian company Nuovo Pignone was the first to fabricate a reactor from this V-modified alloy in Europe, it has often been used for heavy wall pressure vessels in power stations or in petroleum and chemical plants, for example in hydrocracking reactors [1,5,6]. For this purpose, the 2.25Cr-1Mo-0.25V steels are commonly joined with submerged-arc welding (SAW).…”

Section: Introductionmentioning

confidence: 99%

Continuous Cooling Transformation Diagrams of 2.25Cr-1Mo-0.25V Submerged-Arc Weld Metal and Base Metal

Schönmaier

Loder

Fischer

et al. 2020

Metals

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The transformation behavior and microstructural evolution during continuous cooling within the heat affected zone between the weld beads of a 2.25Cr-1Mo-0.25V all-weld metal and the corresponding 2.25Cr-1Mo-0.25V base metal were investigated by means of dilatometer measurements, optical and scanning electron microscopy. Furthermore, macro-hardness measurements were conducted and the ferrite phase fraction was analyzed from optical microscopic images using an imaging processing program. Thereupon a continuous cooling transformation (CCT) diagram for the 2.25Cr-1Mo-0.25V base metal and three welding CCT diagrams with different peak temperatures were constructed to realistically simulate the temperature profile of the different regions within the heat affected zones between the weld beads of the multi-layer weld metal. The microstructural constituents which were observed depending on the peak temperature and cooling parameters are low quantities of martensite, high quantities of bainite and in particular lower bainite, coalesced bainite and upper bainite as well as ferrite for the welding CCT diagrams. Regarding the base metal CCT diagram, all dilatometer specimens exhibited a fully bainitic microstructure consisting of lower bainite, coalesced bainite and upper bainite. Only the slowest cooling rate with a cooling parameter of 50 s caused a ferritic transformation. Nevertheless, it has to be emphasized that the distinction between martensite and bainite and the various kinds of bainite was only possible at higher magnification using scanning electron microscopy.

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On the impact of post weld heat treatment on the microstructure and mechanical properties of creep resistant 2.25Cr–1Mo–0.25V weld metal

et al. 2021

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Creep resistant low-alloyed 2.25Cr-1Mo-0.25V steel is typically applied in hydrogen bearing heavy wall pressure vessels in the chemical and petrochemical industry. For this purpose, the steel is often joined via submerged-arc welding. In order to increase the reactors efficiency via higher operating temperatures and pressures, the industry demands for improved strength and toughness of the steel plates and weldments at elevated temperatures. This study investigates the influence of the post weld heat treatment (PWHT) on the microstructure and mechanical properties of 2.25Cr-1Mo-0.25V multi-layer weld metal aiming to describe the underlying microstructure-property relationships. Apart from tensile, Charpy impact and stress rupture testing, micro-hardness mappings were performed and changes in the dislocation structure as well as alterations of the MX carbonitrides were analysed by means of high resolution methods. A longer PWHT-time was found to decrease the stress rupture time of the weld metal and increase the impact energy at the same time. In addition, a longer duration of PWHT causes a reduction of strength and an increase of the weld metals ductility. Though the overall hardness of the weld metal is decreased with longer duration of PWHT, PWHT-times of more than 12 h lead to an enhanced temper resistance of the heat-affected zones (HAZs) in-between the weld beads of the multi-layer weld metal. This is linked to several influencing factors such as reaustenitization and stress relief in the course of multi-layer welding, a higher fraction of larger carbides and a smaller grain size in the HAZs within the multi-layer weld metal.

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Additional Recommendations for Welding Cr-Mo-V Steels for Petrochemical Applications

Cited by 9 publications

References 1 publication

Microstructural evolution of 2.25Cr-1Mo-0.25V submerged-arc weld metal

Microstructural evolution of 2.25Cr-1Mo-0.25V submerged-arc weld metal

Continuous Cooling Transformation Diagrams of 2.25Cr-1Mo-0.25V Submerged-Arc Weld Metal and Base Metal

On the impact of post weld heat treatment on the microstructure and mechanical properties of creep resistant 2.25Cr–1Mo–0.25V weld metal

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