On the disperse acicular ferrite formation in the structure of cold-resistant joints under temperatures up to –70°С in MMA welding of 10KhSND steel. Part 1

2020 ◽  
pp. 17-29
Author(s):  
G. N. Sokolov ◽  
T. R. Litvinova ◽  
I. V. Zorin ◽  
V. O. Kharlamov ◽  
A. A. Artemyev ◽  
...  
Keyword(s):  
Weld Metal ◽  
Acicular Ferrite ◽  
Cumulative Effect ◽  
Steel Part ◽  
Detonation Synthesis ◽  
Titanium Nitrides ◽  
Low Carbon ◽  
Electrode Coating ◽  
Diamond Nanopowder ◽  
Extreme North

The article presents an analysis of the metallurgical techniques that provide high quality electrodes for manual arc welding of low-carbon low-alloyed cold-resistant steels. It is shown that it is possible to improve technological and operational properties of welded joints at very low climatic temperatures up to –70°C implementing micro-alloying of the weld metal with nitrogen, titanium, cerium oxide and diamond nanopowder produced by detonation synthesis. The composition introduced into the electrode coating modifier mixture is identified. The cumulative effect of its components on the weld impact strength under temperature testing within the range from –20 up to –70°C was established. The matrix of the weld metal is composed mainly of disperse acicular ferrite, hardened by nanoparticles allegedly nitrides and carbonitrides of titanium and aluminum. It is shown that the centers for the crystallization of acicular ferrite are micro-sized non-metallic inclusions formed on ultrafine titanium nitrides. It was revealed that the toughness of the weld metal at low climatic temperatures is higher than toughness of joints welded by massively imported Japanese KOBELCO electrodes LB-52U. The results of the study make it possible to increase the cold resistance of welded structures for petrochemical plants and other facilities located in the Extreme North of the Russian Federation.Part 2 of the article will be devoted to the study of the welding and technological properties of coated electrodes.

Designing Shielded Metal Arc Consumables for Underwater Wet Welding in Offshore Applications

1995 ◽  
Vol 117 (3) ◽  
pp. 212-220 ◽  
Author(s):  
A. Sanchez-Osio ◽  
S. Liu ◽  
D. L. Olson ◽  
S. Ibarra
Keyword(s):  
Calcium Carbonate ◽  
Weld Metal ◽  
Acicular Ferrite ◽  
Oxide Formation ◽  
Electrode Coating ◽  
Microstructural Refinement ◽  
Underwater Wet Welding ◽  
High Toughness ◽  
Porosity Reduction ◽  
Grain Boundary Ferrite

The use of underwater wet welding for offshore repairs has been limited mainly because of porosity and low toughness in the resulting welds. With appropriate consumable design, however, it is possible to reduce porosity and to enhance weld metal toughness through microstructural refinement. New titanium and boron-based consumables have been developed with which high toughness acicular ferrite (AF) can be produced in underwater wet welds. Titanium, by means of oxide formation, promoted an increase in the amount of acicular ferrite in the weld metal, while boron additions decreased the amount of grain boundary ferrite (GBF), further improving the microstructure. Porosity reduction was possible through the addition of calcium carbonate at approximately 13 wt percent in the electrode coating. However, weld metal decarburization also resulted with the addition of carbonate.

Epoxy Resin as a Binder in the Preparation of Rutile Coated Electrodes

2015 ◽  
Vol 798 ◽  
pp. 419-423 ◽  
Author(s):  
Fernando C. Lage ◽  
Leandro S. Oliveira ◽  
Adriana S. Franca ◽  
Alexandre Q. Bracarense
Keyword(s):  
Weld Metal ◽  
Soybean Oil ◽  
Epoxy Resin ◽  
Acicular Ferrite ◽  
Potassium Feldspar ◽  
Electrode Coating ◽  
Weld Microstructure ◽  
Hydrophobic Polymers ◽  
Coated Electrodes

Coated electrodes are used in manual welding, with the coating being comprised of a variety of ingredients, including the binder, usually sodium or potassium silicate. In recent studies aiming at waterproof electrodes, the usual binders were successfully replaced by hydrophobic polymers. In this study, the use of epoxidized soybean oil (ESO) as well as a commercial epoxy resin (CER) as binders in electrode coating formulations was evaluated in order to verify their suitability as replacements for silicates. The produced electrodes were evaluated for the quality of the weld. Results showed that the use of a CER added of potassium feldspar resulted in favorable weld microstructure, with production of acicular ferrite and martensite elimination. ESO based electrodes still need to be improved through flux modification to reduce carbon and hydrogen content in the weld metal.

Crystal Orientation Relationships among Acicular Ferrite, Oxide and the Austenite Matrix in a Steel Weld Metal

2021 ◽  
Vol 1016 ◽  
pp. 1014-1018
Author(s):  
Hidenori Nako ◽  
Yong Jie Zhang ◽  
Goro Miyamoto ◽  
Tadashi Furuhara
Keyword(s):  
Weld Metal ◽  
Acicular Ferrite ◽  
Crystal Orientation ◽  
Low Carbon Steel ◽  
Welding Process ◽  
Steel Weld ◽  
Low Carbon ◽  
Orientation Relationships ◽  
Steel Weld Metal ◽  
Good Lattice

Acicular ferrite (AFα) formed on oxide particles in steel weld metals has a positive effect on toughness at low temperature. Good lattice coherency between AFα and oxide is one of the proposed reasons for promotion of AFα formation. Lattice coherency is affected by crystal structure of oxide and crystal orientation relationship (OR) between oxide and AFα. In the present study, ORs among AFα, oxide and γFe are investigated in a low carbon steel weld metal. Cube-cube (C-C) OR is observed between γFe and the oxide. It is probable that the oxide liquefied at high temperature, and then crystalized having the C-C OR with the surrounding γFe during cooling in welding process. Near Kurdjumov-Sachs (K-S) and near Baker-Nutting (B-N) ORs are observed between γFe/AFα and oxide/AFα, respectively. The misorientation from the B-N OR is larger than that from the K-S OR just after nucleation of AFα. This implies that AFα forms satisfying a near K-S OR with γFe essentially. It is supposed that formation of both the C-C (γFe/oxide) and near K-S (AFα/γ) ORs results in apparent formation of the near B-N OR between oxide and AFα.

scholarly journals A Comparative Study of Acicular Ferrite Transformation Behavior between Surface and Interior in a Low C–Mn Steel by HT-LSCM

Metals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 699
Author(s):  
Xiaojin Liu ◽  
Guo Yuan ◽  
Raja. Devesh Kumar Misra ◽  
Guodong Wang
Keyword(s):  
Grain Boundaries ◽  
Cooling Rate ◽  
Acicular Ferrite ◽  
Laser Scanning ◽  
Sample Surface ◽  
Surface Microstructure ◽  
In Situ Observation ◽  
Low Carbon ◽  
Transformation Behavior ◽  
Ferrite Transformation

In this study, the acicular ferrite transformation behavior of a Ti–Ca deoxidized low carbon steel was studied using a high-temperature laser scanning confocal microscopy (HT-LSCM). The in situ observation of the transformation behavior on the sample surface with different cooling rates was achieved by HT-LSCM. The microstructure between the surface and interior of the HT-LSCM sample was compared. The results showed that Ti–Ca oxide particles were effective sites for acicular ferrite (AF) nucleation. The start transformation temperature at grain boundaries and intragranular particles decreased with an increase in cooling rate, but the AF nucleation rate increased and the surface microstructure was more interlocked. The sample surface microstructure obtained at 3 °C/s was dominated by ferrite side plates, while the ferrite nucleating sites transferred from grain boundaries to intragranular particles when the cooling rate was 15 °C/s. Moreover, it was interesting that the microstructure and microhardness of the sample surface and interior were different. The AF dominating microstructure, obtained in the sample interior, was much finer than the sample surface, and the microhardness of the sample surface was much lower than the sample interior. The combined factors led to a coarse size of AF on the sample surface. AF formed at a higher temperature resulted in the coarse size. The available particles for AF nucleation on the sample surface were quite limited, such that hard impingement between AF plates was much weaker than that in the sample interior. In addition, the transformation stress in austenite on the sample surface could be largely released, which contributed to a coarser AF plate size. The coarse grain size, low dislocation concentration and low carbon content led to lower hardness on the sample surface.

Combining CaO–SiO2–TiO2 and CaO–SiO2–Al2O3 ternary phase systems for design of bimetallic welds

2021 ◽  
Vol 235 (8) ◽  
pp. 1271-1283
Author(s):  
Deepak Bhandari ◽  
Rahul Chhibber ◽  
Lochan Sharma ◽  
Navneet Arora ◽  
Rajeev Mehta
Keyword(s):  
Weld Metal ◽  
Power Plants ◽  
Ternary Phase ◽  
Desirability Function ◽  
Manganese Content ◽  
Research Work ◽  
Welding Process ◽  
Delta Ferrite ◽  
Electrode Coating ◽  
Phase Systems

The bimetallic welds are frequently utilized for pipeline transport system of the nuclear power plants. The occurrences of welding defects generally depend on the filler electrode as well as the electrode coatings during shielded metal arc welding process. This study involves the design of austenitic stainless steel welding electrodes for SS304L–SA516 bimetallic welds. The objective of research work includes the novel design of Al2O3–TiO2–CaO–SiO2 coatings by combining two ternary phase systems using extreme vertices mixture design methodology to analyze the effect of key coating constituents on the weld metal chemistry and mechanical properties of the welds. The significant effect of electrode coating constituent CaO on weld metal manganese content is observed which further improves the toughness of bimetallic weld joints. Various regression models have been developed for the weld responses and multi objective optimisation approach using composite desirability function has been adopted for identifying the optimized set of electrode coating compositions. The role of delta ferrite content in promoting the favourable solidification mode has been studied through microstructural examination.

The Influence of Oxide Inclusion on the Refinement of Bainite and Toughness in HAZ for Low Carbon Steels

2013 ◽  
Vol 651 ◽  
pp. 163-167
Author(s):  
Shu Rui Li ◽  
Xue Min Wang ◽  
Xin Lai He
Keyword(s):  
Mechanical Properties ◽  
Acicular Ferrite ◽  
Oxide Inclusion ◽  
Optical Microscope ◽  
Carbon Steels ◽  
Low Carbon ◽  
Low Carbon Steels ◽  
The Core ◽  
Ti Oxides ◽  
Bainitic Steels

The influence of Ti oxide on the toughness of heat affected zone for low carbon bainitic steels has been investigated. The optical microscope, SEM and TEM were used to analyze the composition, size and distribution of the inclusions, and the microstructure and mechanical properties after welding thermal simulation were also investigated. The effect of Ti oxide inclusion on the transformation of acicular ferrite has also been studied. The results show that after the melting with Ti dioxide technique the inclusion is complex, in the core is Ti oxides about 1-3 micron and around it is MnS. It has been found the acicular ferrite can nucleate at the inclusions and the Ti oxide inclusion will promote the nucleation of acicular ferrite, and the acicular ferrite will block the growth of bainite. Therefore by introducing the Ti oxide in the steels the microstructure of HAZ could be refined markedly therefore the toughness of HAZ can be improved evidently.

Sign in / Sign up

Export Citation Format

Share Document