Electroslag Welding Research Articles

Intergranular stress corrosion cracking behavior of niobium-added Type 308 stainless steel weld overlay metal in a simulated BWR environment

Type 308 stainless steel weld metal as an internal cladding of reactor pressure vessels for boiling water reactors is subject to postweld heat treatment during fabrication and can suffer sensitization depending on carbon and ferrite contents. This sensitization can be avoided by using niobium-added Type 308 weld metal (specified as Type 308 NbL) which was developed for one-layer overlay welding application. In the present study, stress corrosion cracking (SCC) behavior of heat-treated Types 308 and 308NbL weld metals in oxygenated high temperature pure water was evaluated by slow strain rate test and U-bend tests with and without crevice. Every test showed that Type 308NbL weld metals were highly resistant to SCC compared to ordinary Type 308 weld metals. In single U-bend test, one-layer overlay weld metals of Type 308NbL produced by electroslag welding process using wide strip electrodes were crack free over 23,000 h. The U-bend test data of ordinary Type 308 weld metals were successfully analyzed by an SCC reaction model. Using this analysis, the SCC life margin for Type 308NbL over ordinary Type 308 weld metals, expressed as a ratio of respective times to SCC initiation, was estimated to be about 36.

Niobium-Added Type 308 Stainless Steel Weld Metal Resistant to Sensitization by Postweld Heat Treatment and Low-Temperature Aging

Abstract Type 308 (UNS S30800) stainless steel weld metal, applied as an internal cladding of reactor pressure vessels (RPV) for light water reactors, is subjected to postweld heat treatment (PWHT) at around 600°C during RPV fabrication. This PWHT can sensitize or thermally stabilize (heal) the weld metal, depending mainly on the length of PWHT. Moreover, low-temperature aging (LTA) at 500°C for 24 h after PWHT, simulating the so-called low-temperature sensitization (LTS), can significantly influence the sensitization behavior. In the present study, the effect of niobium addition on LTS after PWHT was examined in detail. Optimization of the niobium to carbon ratio (Nb/C) and ferrite content was made, focusing on one-layer weld overlay metals by the electroslag welding process using wide-strip electrodes (typically 150 mm), for full resistance to sensitization and reheat embrittlement by PWHT + LTA (the developed metal was designated as Type 308NbL). A sufficient amount of niobium and a sufficiently fine d...

Fracture toughness of 15X2HMFA steel and its welds

The generalized experimental fracture toughness results of industrial semi-products, made from CrNiMoV steel and intended for VVER-1000 reactor pressure vessel manufacture, are presented. On the base of test results of nine steel heats having a common purity (sulfur to 0.018%; phosphorus to 0.015%; and copper to 0.20%) and of the same number of heats having a higher purity (sulfur to 0.012%; phosphorus to 0.012%; and copper to 0.06%) the fracture toughness temperature dependences were constructed. These differ appreciably from the reference curves for this material according to PNAE G-7-002-86. The temperature dependences K1c for 15X2HMFA steel welds were also obtained. By this, for welds produced using manual arc welding and the types RT-45A and RT-45B electrodes as well as electroslag welding with Sv-16X2HMFTA wire and OF-6 flux, these dependences were constructed on the limited number of welded samples, as these welding methods are, practically, not used in the manufacture of such reactors. The fracture toughness assessment for welds produced by submerged arc welding was carried out for two variants of production processing (Sv-10XGNMAA wire and AH-17M flux; Sv-08XGHMTA wire and NF-18M flux), which were applied in the fabrication of circumferential welds for a VVER-1000 reactor.

Ｈｏｗ ｔｏ 溶接！ エレクトロスラグ溶接材料と施工技術

Ｈｏｗ ｔｏ 溶接！ エレクトロスラグ溶接材料と施工技術

Inhomogeneity of impact properties of electroslag weld metal in constructional steels: Improvement of toughness properties of ESW weld metal in constructional steels (1st Report)

Summary The purpose of this paper is to clarify welded joint performance, especially the impact properties of the weld metal produced by heavy‐current electroslag welding (ESW) and submerged‐arc welding (SAW), with special reference to the high heat input welding processes generally applied in the fabrication of four‐sided thick‐plate box columns. Two types of SM490A 40 mm thick plates were used in the tests. The results obtained may be summarised as follows: The impact properties of the high heat input weld metal produced under standard conditions (thickness of 40 mm) are generally such that ESW has a lower absorbed energy value (vE value) than SAW. The impact value of ESW high heat input weld metal is non‐uniform, and distinctive impact properties are found. That is to say, the vE value of the weld metal core is lower than that of the weld metal rim. ESW weld metal macrostructures have a non‐uniform morphology in both the core and rim. That is to say, a fine‐grained columnar zone is generated in the core and a coarse‐grained columnar zone in the rim. The results presented above in (1) and (2) suggest that the fine‐grained columnar zone in the ESW weld metal core has a low absorbed energy value (vE value) and that the coarse‐grained columnar zone in the rim conversely has a high one. This conflicts with what is conventionally stated about effects of grain size in otherwise identical microstructures, i.e. that the vE value decreases with an increasing grain size. The vE value of ESW weld metal tends to decrease in relation to the welding heat input Q. That is to say, it tends to have a low value at Q > 30.0 kJ/mm (up to around 80.0 kJ/mm). The analyses of the gas composition and five principal elements of the ESW weld metal at different Q values suggest that there is little change in relation to any heat input change. This suggests that the decrease in the vE value in relation to the welding heat input Q is not due to a change in the weld metal composition.

Improvement of impact properties in the core of electroslag weld metal by variation in welding wire composition: Improvement of toughness properties of ESW weld metal in constructional steels (3rd report)

Summary This paper describes an investigation of improvement of the impact properties of electroslag (ESW) weld metal using different types of welding wire. The tests were conducted with six types of welding wire and three levels of welding heat input, i.e. Q = 45.6, 79.0, and 126.7 kJ/mm. The results obtained may be summarised as follows: When a heat input at any level is applied, irrespective of any difference in the welding wire used, the impact value (vE value (J), 273 K) at the centre (core) is lower than that at the periphery (rim). No major improvement of the vE value of the core is found at Q = 45.6 kJ/mm (single‐layer standard heat input conditions for 40 mm thick plate) when wires A ∼ D are used. However, it is found effective to use Ni‐containing wire F (4.18%Ni) to improve the vE value of the weld metal core at Q = 45.6 kJ/mm. The differences in the vE values of the core and rim are closely related to the size of the prior austenite (γ) grains and the different precipitation conditions of the ...

Differences in impact values of core and rim in electroslag weld metal: Improvement of toughness properties in ESW weld metal in constructional steels (2nd Report)

Summary The purpose of this paper is to investigate the impact properties of weld metal produced under different welding conditions with special reference to electroslag welding (ESW) as a high heat input welding process generally applied in the fabrication of four‐sided thick‐plate box columns for general multi‐storey buildings. The paper focuses in particular on the impact properties of ESW weld metal at its centre (core (C)) and periphery (rim (R)). The results obtained may be summarised as follows: The vE value of the weld metal core is lower than that of the weld metal rim. The absorbed energy transition temperature is also higher. The vE values of the weld metal core and rim altered with a change in the welding heat input Q (varied at six levels in the 10.1 ∼ 126.7 kJ/mm range), generally decreasing with an increasing heat input. The vE value of the core is lower than that of the rim. In the weld metal produced at the maximum heat input (126.7 kJ/mm), however, the core and rim have much the same vE values. The vE value of the weld metal core shows little change with a change in the steel type (one type of TMCP and two types of SM490A), and remains at a low value. When there is a change in the surrounding gas (oxygen (O2), air, and argon gas), the vE value decreases in an Ar, air, O2 sequence. The weld metal core vE value is little dependent on any change in the flux type (three types of fused flux) and weight of flux used (0.5 or 0.7 N). The microstructural observations suggest that grain‐boundary ferrite (GBF) occurs at the coarse prior austenite grain boundaries of the rim, with fine acicular ferrite (AF) being mainly found trans‐granularly. In the core, grain‐boundary ferrite is formed at high density at the fine prior austenite grain boundaries, with massive polygonal ferrite (PF) being formed at high density transgranularly. There are thus distinct differences in the coarse ferrite morphology of the rim and core. The SEM observations of the fracture surfaces suggest that the core weld metal has a large grain size, a feature corresponding to its low vE value. The observations made at the fracture surface periphery indicate that numerous secondary cracks are initiated in the grain‐boundary ferrite of the core, suggesting that the ferrite has a low toughness. The results of the SEM simultaneous fractographic‐microstructural observations suggest that fracture selectively propagates along the grain‐boundary ferrite. This indicates that the low vE value of the core is due to the presence of high‐density grain‐boundary ferrite and massive transgranular polygonal ferrite.

Corrosion behaviour of nickel based cladding alloys

Summary As a consequence of their high cost, nickel based alloys are more appropriately used for surface coating. The properties of NiMo16Cr16Ti and NiCr21Mo14W cladding deposited by the submerged‐arc welding and resistance electroslag welding processes, using the single and multi‐layer techniques, are compared and discussed, with respect to their corrosion behaviour. The key criteria used to describe cladding qualities are loss of volume, tendency to intergranular corrosion and pitting corrosion resistance. Results show that RES cladding is the more suitable technique to produce corrosion resistant nickel based coatings. The corrosion behaviour of double‐layer RES cladding shows better pitting resistance than triple‐layer SAW cladding.

柱材にHT780鋼を用いた柱梁十字骨組の履歴特性に関する研究

In respect to a HT780-Box-Column, cyclic increasing loading tests have applied to its column to SM490-H-Shaped-Beam. The present investigation aims to comprehend the following matters quantitatively. 1. Effect of a bearing ratio of beam against column to hysteresis characteristic of the frame. 2. Effect of an axial force ratio to hysteresis characteristic of the frame, which is including of a case of tensile force applying to the column. 3. Mechanical behavior of the welded portion of electroslag welding and comer welding of the column by a partial penetration welding. Consequently, it is considered that technical data for structural designing HT780-Box-Column can be supplied.

構造用鋼のエレクトロスラグ溶接金属の靭性向上に関する研究 （第１報） 構造用鋼のエレクトロスラグ溶接金属内における衝撃特性の不均一性に関する研討

The purpose of this paper is to clarify the weld joint performance, especially the impact characteristics of the weld metal produced by electroslag welding (ESW) and submerged arc welding (SAW) by directing our attention to the high heat input welding processes which are usually applied for the manufacture of four side thick plate box column. Two types of SM490A 40 mm thickness have been used in this test. The test results are summarized in the following.(1) As for the impact characteristics of high heat input weld metal, the absorption energy values (vE value) of weld metal made by ESW are generally lower than those by SAW.(2) As for the vE values of various locations in high heat input weld metal by ESW, the vE value in the center of weld metal (Core) is considerably lower than those in peripheral locations of weld metal (Rim).(3) Macrostructure of ESW weld metal suggested that fine crystal grains were generated in the core with coarse crystal grains in the rim.(4) In the weld metal by ESW the impact value of fine grain core area is low and those in the peripheral coarse grain rim area are high on the contrary. This result disagrees with the conventional theory about the general relation between impact value and grain size.(5) It is found that the vE value of weld metal by ESW shows a tendency to decrease according to the increase of welding heat input (Q) and becomes low at the Q of 30.0 kJ/mm (up to 80.0 kJ/mm). Furthermore, the decrease of vE value related to the increase of welding heat input has not be caused by the change of chemistry such as C, Si, Mn, P and S in the weld metal.

Toughness Characteristics and Its Improvement of Electroslag Weld Metal of Structural Steel Plate.

High heat input electroslag welding (ESW) is widely used for the four side welding of 490 N/mm2 class steel between thick flange or web plate and diaphragm without Post Weld Heat Treatment (PWHT). The notch toughness of ESW weld metal is generally lower in the central part (C zone) then in the peripheral part (R zone) of the weld metal. This report has treated from metallurgical investigation the reason why the notch toughness of C zone is inferior to R zone. Moreover the improvement of the notch toughness in C zone has been investigated with the change of chemical element in the weld metal. As a result the reduction of Si content in weld metal is beneficial to improve the notch toughness of C zone and equalizes the ductility of both zones.

構造用鋼のエレクトロスラグ溶接金属の靭性向上に関する研究 （第２報） エレクトロスラグ溶接金属の周辺および中央部の衝撃値差異に関する二，三，の確性実験

The purpose of this paper is to investigate the impact characteristics of the weld metal produced using various welding parameters by directing our attention to the electroslag welding (ESW). This is one of high heat input welding processes which are usually applied for the manufacture of four side thick plate box column for general multistoried buildings, ets.In particular, this paper clarified the impact characteristics of ESW weld metal in its both center [Core (C) ] and peripheral locations [Rim (R) ]. The test results obtained are summarized in the following.(1) The impact test value (vE) of weld metal in its core (C) is lower than those in the rim (R) locations.(2) As for the change of vE value according to the change in welding heat input (at six levels of Q=10.1 to 126.7 kJ/mm), the vE value of both C and R locations generally decreases according to the increase of heat input. However, vE. value in the core (C) is always lower than those in R locations.(3) Regardless of the changes in steel types (such as TMCP and SM490A), flux types (three molten types) and amount of flux supplies (0.5 N or 0.7 N), the vE value of C location is always low without any significant change. Futhermore, the vE value decreases according to the change in shielding gas types from Argon gas (Ar) to air and then to oxygen (O2) in this order.(4) The formation of grain boundary ferrite in the coarse prior austenite (γ) boundaries and that of fine acicular ferrite inside the grains are mainly noticed in R locations as the result of the observation of microstructure. However, the formation of grain boundary ferrite in the fine prior γ boundaries and that of coarse ferrite inside the grains are densely noticed in C locations.(5) As the result of the observation of impact fractures with a scanning electron microscope (SEM), it is found that the facet size of weld metal in C locations is actually large which matches the low vE value.Moreover, selective fractures propagation along the grain boundary ferrite in the core of the impact fracture is found as the result of the observation on both two faces of structure at the same time. This indicates that the low vE value in C locations has been caused by the existence of both dense grain boundary ferrite and coarse ferrite inside the grains.

構造用鋼のエレクトロスラグ溶接金属の靭性向上に関する研究 （第３報） 溶接ワイヤ成分変化によるエレクトロスラグ溶接金属中央部の衝撃特性向上に関する検討

Investigations for the improvement of impact characteristics of Electroslag (ESW) weld metal was conducted using different types of welding wire. The test was carried out by using six types of welding wire and three levels of welding heat input such as Q=45.6, 79.0 and 126.7 kJ/mm.The test results obtained are summarised shown as the following.(1) In the case of all three heat input levels, the vE (absorbed energy) value in core (C) location of ESW weld metal was generally lower than those in rim (R) locations.Furthermore, regardless of the types of welding wires, the same tendency was noticed.(2) vE value was improved at C part of the weld metal produced by the wire containing Ni (wire F containig 4.18% Ni) and standard welding heat input of Q=45.6 kJ/mm.(3) In the previous paper it was comfirmed that the difference of vE values between C and R parts was significantly caused by the difference of ferrite structure types between them. In the C location the formation of extremely dense and massive polygonal ferrite (PF) was certified, and in the R location the formation of fine acicular ferrite (AF) was noticed inside the large austenite (γ) grains.However, cooling rate of weld metal of C and R locations for -τ1073(800)to773k(500c) in Q=45.6 kJ/mm was not so much to cause the change of structure.(4) The chemical analytical results of C, Mo and Ni in welding wire, base metal and weld metals showed that the dilution from the base metal into weld metal was comparatively stable (about 50-60%).(5) Improvement of the vE values at C part were expected thanks to formation of the coarse former austenite (γ) grains by the addition of Ni element.

Ductility of 15Kh2NMFA steel in electroslag welding thick plate components at 900–800 °C

Ductility of 15Kh2NMFA steel in electroslag welding thick plate components at 900–800 °C

Prediction of toughness scatter in heat affected zones (HAZ) with local approach

Carbon-manganese (C-Mn) steels are widely used in welded structures. For low temperature applications, it is essential to maintain a good toughness level in the welds. In this paper, the “local approach” for cleavage fracture is used based on the weakest link hypothesis. This kind of analysis has already been applied with success to homogeneous materials and in particular to the base metal and the weld metal of structural steels. By contrast, it has never been applied to the case of heterogeneous materials such as welds. The adopted test plan included four phases of increasing complexity. First, the approach was validated in very simple configurations, where it was possible to identify without ambiguities the mechanical properties of the different zones. Then more complex welds were studied. The first part of this study included measurement of mechanical properties and local criteria of the different zones [base metal and simulated heat affected zone (HAZ)]. In the second part, a brittle zone of well controlled dimensions was produced with an electron beam. The theoretical predictions match with experimental results. The third part was a validation attempt on a simple monopass weld. Single edge notch bend (SENB) specimens with a notch in the HAZ were tested in order to measure toughness ( K, J, CTOD). Results from the first part allowed comparison of experimental results with those predicted by the local approach. Although the real configuration of the electroslag welding (ESW) was more complex than had been expected, the local approach predictions were consistent with the experimental results. The objective of the fourth part was to study a multipass weld. As in the second part, the toughness measured on SENB specimens. The toughness in multipass HAZ decreases markedly at first and then very slowly when the percentage of coarse grains intercepted by crack front increases. The predictions agree fairly well with the experimental results. This study shows that local criteria allow a realistic prediction of the fracture toughness variation not only with temperature, but also as a function of brittle zones intercepted by the crack front. The scatter is also well predicted.

超大型鋼構造物特集〈その２〉建築物 江戸東京博物館の構造設計と極厚鋼板の現場溶接（現場エレクトロスラグ溶接）

超大型鋼構造物特集〈その２〉建築物 江戸東京博物館の構造設計と極厚鋼板の現場溶接（現場エレクトロスラグ溶接）

Application of low-cycle fatigue data to pressure vessel design fatigue curve

This paper presents a study on the low-cycle fatigue behaviour of the type of steels used for boiler drums, that is 19Mn5, BHW35, and its electroslag weld metal. These are all tested at 20°C and BHW35 at 350°C as well. Results show that the fatigue strength of the 19Mn5 steel in the low-cycle regime is higher than that of BHW35 steel; however, the fatigue strength of BHW35 steel in the high-cycle regime is higher than that of 19Mn5. Based on Langer's philosophy of the design fatigue curve, this paper has developed the fatigue curve for pressure vessel design. Furthermore, this design fatigue curve is compared with the design curves of ASME and BS5500.

Process parameter determination for consumable nozzle electroslag welding

The process parameters and weld dimensions in consumable nozzle electroslag welding were calculated using the two dimensional heat flow condition based on Eregin's concept. The weld metal dilution under these operating variables was also computed. Experiments revealed that calculated parameters produce sound welded joints and that there is fairly good agreement between the calculated and observed results.MST/1103

Selection of the metallurgical variant of electroslag welding of steels melted with vacuum-carbon deoxidation

Selection of the metallurgical variant of electroslag welding of steels melted with vacuum-carbon deoxidation

Effect of delta-ferrite on the properties of welded joints of steel 08Kh18N10T

1. Presence in a welded joint of steel 08Kh18N10T of 2–2.5% δ-ferrite promotes an increase in the degree of first-order stress relaxation at 400–480°C without reducing strength properties and with retention of resistance to ICC. 2. A reduction in the relaxation resistance of an electroslag weld with an austenitic structure with a small amount of ferrite is due to the greater deformation capacity of ferite and microvolumes of austenite adjacent to it.