•A-TIG has low delta ferrite content (0.5%).•GTA weld shows complete absence of delta ferrite.•GTA weld has higher toughness than A-TIG weld.•A-TIG weld requires prolonged PWHT to achieve the ...required toughness.
Modified 9Cr-1Mo (P91) steel is widely used in the construction of power plant components. In the present study, a comparative study on influence of activated flux tungsten inert gas (A-TIG), and gas tungsten arc (GTA) welding processes on the microstructure and the impact toughness of P91 steel welds was carried out. P91 steel welds require a minimum of 47J during the hydrotesting of vessels as per the EN1557: 1997 specification. Toughness of P91 steel welds was found to be low in the as-weld condition. Hence post-weld heat treatment (PWHT) was carried out on weld with the objective of improving the toughness of weldments. Initially as per industrial practice, PWHT at 760°C – 2h was carried out in order to improve the toughness of welds. It has been found that after PWHT at 760°C – 2h, GTA weld (132J) has higher toughness than the required toughness (47J) as compared with A-TIG weld (20J). The GTA weld has higher toughness due to enhanced tempering effects due to multipass welding, few microinclusion content and absence of δ-ferrite. The A-TIG weld requires prolonged PWHT (i.e. more than 2h at 760°C) than GTA weld to meet the required toughness of 47J. This is due to harder martensite, few welding passes that introduces less tempering effects, presence of δ-ferrite (0.5%), and more alloy content. After PWHT at 760°C – 3h, the toughness of A-TIG weld was improved and higher than the required toughness of 47J.
•P22 steel so far joined using various processes mainly GTAW process.•The present work makes a detailed analysis of ATIG process on joining of P22 steel.•There is no literary information on joining ...of P22 steel using ATIG process.•There was an improvement of toughness of welds using ATIG process in the as-weld condition as well as PWHT condition.
In the present study, 12mm thick double side square butt joint was fabricated on 2.25Cr-1Mo (P22) steel plates using A-TIG welding process with in-house developed activated fluxes. Microstructure and mechanical properties of the weld joint were characterized. Effect of post weld heat treatment (PWHT) on the impact toughness was studied. In the as-welded condition toughness was found to be 133J. There was no proeutectoid ferrite in the weld. After PWHT, the toughness of weld was increased to 177J due to dissolution and coarsening of existing precipitates. A-TIG weld joint of 2.25Cr-1Mo steel exhibited high hardness and good impact toughness in the as welded condition.
Hindrance to weld metal shrinkage by the adjacent base material introduces inevitable residual stress and distortion in welded components. Nevertheless, proper choice of welding process can reduce ...the magnitude of tensile residual stress and distortion. Here hybrid laser MIG and Hotwire-TIG welding processes are used, which provides sound 316L(N) stainless-steel weld joint at reduced heat input. The numerical modeling and experimental result shows that tensile residual stress distribution is substantially narrower in hybrid laser MIG than in Hotwire-TIG weld joint. Furthermore, the degree of external restraint significantly influences the magnitude of residual stress distribution and distortion. The numerical and experimental results exhibited reasonable agreement.
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•11 mm thick Type 316L(N) weld joints were fabricated using HLM and HW-TIG welding techniques.•The IHM and MHM accurately predicted residual stress and distortion in HLM and HW-TIG weld joints.•Residual stress distribution was narrower in HLM (∼22 mm) than HW-TIG weld joint (∼46 mm).
Abstract
– Data Communication in customer oriented sector has significant information which is considered as a vital part in enhancing and improving customer base. Loyal customers in business sector ...are based on buying and selling of products or making use of services provided. Generally, the customers may switch on to variant enterpriser who affords best services with best price hence retaining them is a tedious task unless their communiaction data regarding service is analysed in periodic and to keep track of customer, the enterpriser should know the purchasing pattern and needs of loyal customersThe discovered pattern is also helps to afford proper discounts to the customers at the right time. This research paper experiments customer data in Telecommunication sector to discover useful and interesting patterns. There are so many data mining techniques put forward in revealing the pattern and this paper discusses all the possible mining techniques and evaluates an association rule mining with clustered data to create best rules. For clustering, Hierarchical agglomerative is used and FP-Growth algorithm is used for association rule mining. Both clustered data and association rules results regarding data communication are presented. The research work is implemented in weka tool and assessed with suitable evaluation metrics.
In the present investigation, creep deformation and rupture behavior of type 316LN stainless steel weld joints fabricated from hotwire tungsten inert gas (HW-TIG), activated-TIG (A-TIG), and hybrid ...laser metal inert gas (HLM) welding processes were studied. The creep testing was carried out at 923 K under various stress levels. The weld joints have undergone a higher rate of deformation and exhibited lower creep rupture life as compared to that of the base metal. The welding process significantly influenced the delta (
δ
)-ferrite content in the weld metal of stainless steel weld joints A-TIG (1.7 ferrite number (FN), HLM (1.3 FN), and HW-TIG (3.5 FN), its morphology and also the creep cavity density during creep deformation. The HW-TIG weld joint possessed significantly lower creep rupture life than that of the A-TIG and HLM weld joints. The HLM joint has exhibited a better creep rupture life than the A-TIG and HW-TIG weld joints. The microstructural constituents,
i.e
.,
δ
-ferrite content, columnar and equiaxed dendrites, and sigma (
σ
)-phase formation during creep, have significantly influenced the creep deformation and rupture strength of the joints. The orientation of the columnar structure, which is parallel to stress direction and lower
δ
-ferrite content in the A-TIG and HLM joints, has resulted in lower creep cavitation and higher creep rupture strength as compared to that of the HW-TIG weld joint. As the 316LN stainless steel weld joint processed by the HLM welding process exhibited the best creep rupture life, the HLM welding process is recommended for the welding of 316LN stainless steel.
In the present study, flux-cored arc welds of modified 9Cr–1Mo (P91) steel were produced using four types of shielding gases with rutile based flux-cored wire. Artificially prolonged post-weld heat ...treatment and GTAW surface melting methods improved the toughness of welds having high inclusion content. Fusion zone toughness was correlated with inclusion size and its distribution, shielding gas composition, chemical composition and post-weld heat treatment process parameters. It was found that 95% argon
+
5% CO
2 was the ideal shielding gas medium for FCA process to meet the toughness requirements with better process characteristics.
Modified 9 Cr–1 Mo is an ideal candidate preferred for high temperature applications in power plants. In this study, three P91 welds of 12 mm thickness are produced using Gas Tungsten Arc Welding ...(GTAW), Cold Metal Transfer (CMT) and Pulsed-CMT (P-CMT) processes. The impact toughness is evaluated in the as-welded as well as in the PWHT (760 °C-2 h) condition. It is found that P-CMT process resulted in the highest toughness in both the conditions. The heat input was maximum in the case of GTAW (800 J/mm) welds and minimum in CMT (330 J/mm). Even though P-CMT (380 J/mm) has heat input slightly above CMT, the former is compensated by higher welding speeds. Electron microscopy analysis revealed the presence of fine M23C6 and MX precipitates. Among the welds, P-CMT had minimal amount of the precipitates whereas GTAW welds had the maximum. The dimple morphology observed in the ruptured surface significantly varied and P-CMT process had finer dimples indicating finer weld microstructures and enhanced mechanical properties.
In the present study, A-TIG welding was carried out on grade 91 steel plates of size 220 × 110 × 10 mm using the in-house developed activated flux to produce butt-joints. The room-temperature impact ...toughness of the A-TIG as-welded joint was low due to the presence of untempered martensite matrix despite the low microinclusion density caused by activated flux and also low δ-ferrite (<0.5 %) content. Toughness after postweld heat treatment (PWHT) at 760 °C-2 h was 20 J as against the required value of 47 J as per the specification EN: 1557:1997. However, there was a significant improvement in impact toughness after PWHT at 760 °C for 3 h. The improvement in toughness was attributed to softening of martensite matrix caused by precipitation of carbides due to tempering reactions. The precipitates are of type M
23
C
6
, and they are observed at grain boundary as well as within the grains. The A-TIG-processed grade 91 steel weld joint was found to meet the toughness requirements after PWHT at 760 °C-3 h. Observations of fracture surfaces using SEM revealed that the as-welded joint failed by brittle fracture, whereas post-weld heat-treated weld joints failed by decohesive rupture mode.
The present work discusses about the mechanical and metallurgical properties of Incoloy 800 H friction welded joints. The process parameters namely friction pressure, friction time, upsetting ...pressure, upset time, and rotational speeds were varied from low level to high level to study their effects on the properties of the weldments. The tensile tests were carried out at four different temperatures namely at room temperature, 550, 650, and 750 °C. From the results, it is observed that as the testing temperature increased, there was a reduction in tensile strength of welds. The friction welds had higher hardness than the base metals. This was due to the formation of secondary phases (γ′ and M23C6) in friction welds. The tensile and impact fracture surfaces were further analyzed through SEM and finally the individual effects of the parameters with respect to the microstructures variation in the welds were studied.
•Introduction and development of metal-cored arc welding process is of recent origin.•Influence of process variables, shielding gas composition, microinclusion content on toughness of welds was ...studied.•Possible use of pure argon as shielding gas in metal-cored arc welding process.
In the present work, metal-cored arc welding process was used for joining of modified 9Cr-1Mo (P91) steel. Metal-cored arc welding process is characterized by high productivity, slag-free process, defect-free weldments that can be produced with ease, and good weldability. Toughness is essential in welds of P91 steel during hydro-testing of vessels. There is a minimum required toughness of 47J for welds that has to be met as per the EN1557:1997 specification. In the present study, welds were completed using two kinds of shielding gases, each composition being 80% Argon+20% CO2, and pure argon respectively. Microstructural characterization and toughness evaluation of welds were done in the as – weld, PWHT at 760°C – 2h and PWHT at 760°C – 5h conditions. The pure argon shielded welds (‘A2’ and ‘B2’) have higher toughness than 80% argon+20% CO2 shielded welds (‘A1’ and ‘B1’). Pure argon shielded welds show less microinclusion content with low volume fraction of δ-ferrite (<2%) phase. Themo-calc windows (TCW) was used for the prediction of equilibrium critical transformation points for the composition of the welds studied. With increase in post-weld heat treatment (PWHT) duration from 2h to 5h, there was increase in toughness of welds above 47J. Using metal-cored arc welding process, it was possible to achieve the required toughness of more than 47J after PWHT at 760°C – 2h in P91 steel welds.
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