Low-alloy Weld Metals Research Articles

Weld Metal Dendritic Structure Modification by Dispersed Refractory Oxide Particles

The paper deals with the modification effect of dispersed oxides particles (Al2O3, MgO, ZrO) on the dendrite structure in low-alloy weld metal. The flux-core wire 1.6 mm diameter for inoculating of oxides powder to weld pool was purposed. Obtained results confirmed an influence of inoculated refractory oxides on dendrites size and morphology, microstructure and mechanical properties of the weld metal.

Impact Toughness of Steel WMD After TIG Welding

AbstractThe material selected for this investigation was low alloy weld metal deposit after TIG welding with various amount of oxygen in weld metal deposit (WMD). After TIG process it is difficult to get proper amount of oxygen in WMD on the level much lower than 350 ppm. The highest impact toughness of low alloy WMD corresponds with the amount of oxygen in WMD above 350 ppm. In the paper focuses on low alloy steel after innovate welding method with micro-jet cooling that could be treated as a chance on rising amount of oxygen in weld. Weld metal deposit (WMD) was carried out for TIG welding with micro-jet cooling with various amount of oxygen in WMD. In that paper various gas mixtures (gas mixtures Ar-O2and Ar-CO2) were tested for micro-jet cooling after TIG welding. An important role in the interpretation of the results can give methods of artificial intelligence.

Sources of Variability and Lower Values in Toughness Measurements of Weld Metals

In this paper, the sources of variability and lower values in toughness measurements of a high-strength low alloy weld metal are investigated by detailed observations of fracture surfaces and the microstructures at crack initiation. The results reveal that the variability of the notch Charpy toughness is related to the location of the cleavage initiation origins. The three factors jointly contribute to give rise to variability and lower value of toughness. That is, (1) the location that the notch is sampled at deposited weld metal or reheated weld metal, (2) the location that a large grain region is appeared on the path ahead of the notch root, (3) the distributed location of the defect or the brittle second-phase particle. When three factors were simultaneously satisfied, the lower value of the Charpy toughness is appeared. The notch is sampled at the largest grain region at deposited weld metal, and the defect or the brittle second-phase particle is close to the notch root and sampled by its high stress field, the lowest Charpy toughness is obtained.

高強度低合金鋼溶接金属のPWHTに関する研究 (第2報) 溶接金属のPWHTによる脆化原因とその対策について

高強度低合金鋼溶接金属のPWHTに関する研究 (第2報) 溶接金属のPWHTによる脆化原因とその対策について

Micromechanisms of cleavage fracture initiation from inclusions in ferritic welds: Part II. Quantification of local fracture behaviour observed in fatigue pre-cracked testpieces

The quantification of the local fracture behaviour and the fracture toughness of high strength low alloy weld metals have been studied using fatigue pre-cracked CTOD testpieces. In CTOD testpieces, when brittle fracture occurs, with or without prior stable crack growth, cleavage usually starts from an inclusion located at the initiation site within allotriomorphic ferrite for weld metals with a classical microstructure, or within bainite or martensite packets in weld metals with a lath-like microstructure. The mean value of fracture stress, σ F( X 0), when evaluated using CTOD testpieces, has proved to be higher than when it is evaluated using SENB testpieces. This is deduced to be as a direct consequence of the reduction of the inclusion size found at initiation sites in CTOD testpieces. The effective surface energy here was evaluated to be approximately 8.6 J m −2, for the weld metal with a classical microstructure and 14 J m −2, for the weld metal with a lath-like microstructure. These values are closely similar to the values of the effective surface energy evaluated using SENB testpieces.

The effect of yttrium on the mechanical properties of a low-alloy weld metal undergoing stress relief annealing

The effect of yttrium on the mechanical properties of a low-alloy weld metal undergoing stress relief annealing

Role of non-metallic inclusions in formation of acicular ferrite in low alloy weld metals

A critical investigation into the role of non-metallic inclusions in the nucleation of acicular ferrite in low alloy C–Mn–Ni weld metals was carried out using rapid in situ quenching, transmission electron microscopy, energy dispersive X-ray spectroscopy analysis, and dilatometric techniques. The relationship between the transformed acicular ferrite, the inclusions, and the chemical nature of the inclusions which had actually nucleated ferrite laths was examined in detail. By employing weld metals with either intermediate (200–350 ppm) or low (15–30 ppm) oxygen levels, the inclusion chemistry and nucleation behaviour of acicular ferrite in welds with different oxygen contents were compared. In addition, the influence of the [Al]/[O] ratio in lower oxygen content weld metals was also examined. It was found that the first acicular ferrite laths nucleated from the inclusions at both oxygen levels, and the chemical composition of the active inclusions varied considerably. The inclusions nucleated acicular ferrite by acting simply as inert substrates with the ability to reduce the free energy barrier to nucleation. The number and size distribution of the inclusions appeared to be the dominant factors; the thermal stress-strain fields and lattice disregistry were less important. The most favourable type of inclusions were within the size range 0·3–0·9 μm for the higher oxygen content weld metals and 0·35–0·75 μm for the lower oxygen level weld metals. A high [Al]/[O] ratio depresses the formation of acicular ferrite by increasing the soluble matrix aluminium content, which encourages extensive ferrite sideplate formation; the concurrent variation in inclusion chemical composition did not appear to influence the nucleation of acicular ferrite.MST/3209

Role of non-metallic inclusions in formation of acicular ferrite in low alloy weld metals

AbstractA critical investigation into the role of non-metallic inclusions in the nucleation of acicular ferrite in low alloy C–Mn–Ni weld metals was carried out using rapid in situ quenching, transmission electron microscopy, energy dispersive X-ray spectroscopy analysis, and dilatometric techniques. The relationship between the transformed acicular ferrite, the inclusions, and the chemical nature of the inclusions which had actually nucleated ferrite laths was examined in detail. By employing weld metals with either intermediate (200–350 ppm) or low (15–30 ppm) oxygen levels, the inclusion chemistry and nucleation behaviour of acicular ferrite in welds with different oxygen contents were compared. In addition, the influence of the [Al]/[O] ratio in lower oxygen content weld metals was also examined. It was found that the first acicular ferrite laths nucleated from the inclusions at both oxygen levels, and the chemical composition of the active inclusions varied considerably. The inclusions nucleated acic...

Low-temperature cyclic crack-growth resistance of hydrogenated welds

We study the influence of chemical and phase composition on the cyclic crack-growth resistance of non-hydrogenated and hydrogenated welded joints in low-alloy steel at normal and low (−70°C) temperatures. It was discovered that the increase in the nickel content from 0.06% to 3.27% induces an increase in impact toughness and cyclic crack-growth resistance at low temperatures which can be explained by the increase in the content of needle ferrite and by the substitution of uniformly distributed residual austenite for the pearlitic component in the zone characterized by the columnar structure of heat treated beads. Hydrogen saturation of the weld metal leads to a decrease in its cyclic crack-growth resistance at normal temperatures and produces almost no effect on this parameter at low temperatures (−70°C). The presence of the second austenitic phase in the low-alloy weld metal decreases its susceptibility to hydrogen embrittlement in the case where finely divided austenite is uniformly distributed over the weld.

Columnar grain development in C-Mn-Ni low-alloy weld metals and the influence of nickel

This paper discusses the development of columnar grains in as-deposited C-Mn-Ni(-Mo) low-carbon low-alloy weld metals and the influence of the alloying elements, particularly nickel. It was found that the austenite columnar grain size prior to the γ-α transformation of the weld metals was mainly controlled by the alloying contents rather than HAZ grains adjacent to the fusion boundaries, although the latter determined the size of the initial columnar grain size. The addition of nickel initially depressed the prior austenite grain size and subsequently dramatically coarsened it. This was related to the nickel equivalent (Nieq) of the weld metals and the peritectic reaction during the solidification process. Small columnar grains were associated with a Nieq between 3.4 and 6.2% which resulted in a peritectic reaction when the weld melt solidified, whilst a Nieq higher than 6.2% produced very large columnar grains because the weld pool would directly solidify into austenite and have a subsequent continuous growth.

Study on PWHT Embrittlement in High Strength Low Alloy Weld Metals (Paper 1)

Study on PWHT Embrittlement in High Strength Low Alloy Weld Metals (Paper 1)

Comparative Evaluation of Weld Metals Deposited Using C-Mn and Low Alloy Filler Wires / Vergleichsuntersuchungen an Schweißnähten mit C- Mn- und niedriglegierten Schweißzusatzdrähten

Butt welds in T-1 steel type A (ASTM A-517 Gr B) were prepared using two types of filler wires, C-Mn (AWS/ER 70S-6) and low alloy (AWS/ER 110S G). Metal inert gas MIG (CO 2 ) welding process was used to weld samples. Tensile strength, Charpy toughness and hardness were compared. The results indicated that low alloy weld metals showed better strength and toughness properties. However, strength and toughness of C-Mn weld metals were also found to be satisfactory especially when larger diameter electrodes were used. The study showed that for moderate strength applications C-Mn filler wires can be advantageously made use of to weld T-1 steels, type A