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% CO2 was the ideal shielding gas medium for FCA process to meet the toughness requirements with better process characteristics. © 2009.

M. Kamaraj

Department of Metallurgical and Materials Engineering

ARC WELDS

Chemical compositions

FLUX-CORED WIRE

Fusion zones

INCLUSION CONTENT

INCLUSION SIZES

POST WELD HEAT TREATMENT

Process characteristics

SHIELDING GAS

SURFACE MELTING

Argon

Cavity resonators

Chromium

Electric welding

Fractography

FRACTURE MECHANICS

Gases

Heat treatment

Laser Beam Welding

microstructure

Molybdenum

Oxide minerals

Shielding

Steel

Titanium oxides

Welds

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Journal of Materials Processing Technology

Conventional gas metal arc welding of modified 9Cr-1Mo steels referred to as P91 steels is considered difficult due to loss of alloying elements and degradation of weld joint properties. In comparison to the conventional process, pulsed current gas metal arc welding allows more accurate control of heat input per unit length and electrode deposition and, thus, can be more suitable for the joining of P91 steel. A detailed experimental study is therefore undertaken to examine the roles of welding current, speed and groove angle in the weld bead profiles and joint properties in multipass pulsed current gas metal arc welding of 12 mm thick P91 steel. The results show that the joint properties are strongly influenced by the heat input per unit length and the groove angle. A groove angle of 75° and an appropriate choice of process conditions resulted in fairly acceptable bead profiles and joint properties. © 2016 Institute of Materials, Minerals and Mining.

Science and Technology of Welding and Joining

Multipass pulsed current gas metal arc welding of P91 steel

A detailed experimental study was undertaken to examine the suitability of pulsed current gas metal arc welding of 12 mm thick P91 steels in groove joint configurations with metal cored filler wire. Both the single and multipass welds showed satisfactory bead morphology, tensile strength and toughness especially at higher groove angles of 60° and 75° for the selected range of welding current and speeds. The weld metal compositions showed considerably high presence of Ni, Mn and Si with little loss of other alloying elements. The weld properties were primarily affected by the heat input per unit length of weld and the groove angle. The maximum ultimate tensile strength and toughness of the welds were found to be around 845 MPa and 125 J, respectively, for a heat input of 1.38 kJ/mm and a groove angle of 75°. The use of metal cored filler wires could enhance the welding speed by 20% and filler wire deposition rate by 42% compared to that with the solid wires. Overall, the present study showed that the pulsed current gas metal arc welding of medium to high thickness P91 steels using metal cored filler wires could provide higher deposition rate and welding speed, and enhanced weld bead properties in comparison to solid wires. © 2015 Elsevier B.V. All rights reserved.

Pulsed current gas metal arc welding of P91 steels using metal cored wires

Modified 9Cr-1Mo steels are commonly welded using gas tungsten arc welding process for its superior control over the rate of heat input and vaporization loss of the key alloying elements although the rate electrode deposition remains restricted. Recent developments in pulsed current gas metal arc welding have significantly improved its ability to enhance the rate of electrode deposition with a controlled heat input rate while its application for welding of modified 9Cr-1Mo steels is scarce. The present work reports a detailed experimental study on the pulsed current gas metal arc welding of modified 9Cr-1Mo steels. The effect of the shielding gas, welding current, and speed on the weld bead profile, microstructure and mechanical properties are examined. The results show that the pulsed current gas metal arc welding with appropriate welding conditions can provide acceptable bead profile and mechanical properties in welds of modified 9Cr-1Mo steels. © 2015, ASM International.

Journal of Materials Engineering and Performance

Probing Pulsed Current Gas Metal Arc Welding for Modified 9Cr-1Mo Steel

Modified 9Cr-1Mo steel finds increasing application in power plant construction because of its excellent high-temperature properties. While it has been shown to be weldable and resistant to all types of cracking in the weld metal and heat-affected zone (HAZ), the achievement of optimum weld metal properties has often caused concern. The design of appropriate welding consumables is important in this regard. In the present work, plates of modified 9Cr-1Mo steel were welded with three different filler materials: standard 9Cr-1Mo steel, modified 9Cr-1Mo, and nickel-base alloy Inconel 182. Post-weld heat treatment (PWHT) was carried out at 730 and 760°C for periods of 2 and 6 h. The joints were characterized in detail by metallography. Hardness, tensile properties, and Charpy toughness were evaluated. Among the three filler materials used, although Inconel 182 resulted in high weld metal toughness, the strength properties were too low. Between modified and standard 9Cr-1Mo, the former led to superior hardness and strength in all conditions. However, with modified 9Cr-1Mo, fusion zone toughness was low and an acceptable value could be obtained only after PWHT for 6 h at 760°C. The relatively poor toughness was correlated to the occurrence of local regions of untransformed ferrite in the microstructure.

Microstructure and mechanical properties of weld fusion zones in modified 9Cr-1Mo steel

Journal of Materials Science

Fusion zone purification of metal containing oxide inclusions via laser welding

International Journal of Pressure Vessels and Piping

Issues in replacing Cr–Mo steels and stainless steels with 9Cr–1Mo–V steel

Welding International

An investigation into the properties of the heat affected zone simulated in 9Cr‐1 Mo‐Nb, V(P91) steel intended for service at elevated temperatures

High temperature properties of improved 9% Cr steel weldments

A study on influence of shielding gas composition on toughness of flux-cored arc weld of modified 9Cr-1Mo (P91) steel

Journal	Journal of Materials Processing Technology
ISSN	09240136
Open Access	No