Some studies on P91 steel and their weldments

The improvement of thermal efficiency of power plants has provided the incentive for the development of the martensitic–ferritic 9–12%Cr creep-resistant steels. Good progress has been made in developing such steels, which are being used particularly in the wrought form as tubes and pipes for fossil fuelled power stations. They are also finding use in high temperature process plant within the oil and gas sector, and are being considered for use in generation IV nuclear designs. The high temperature conditions that these steels operate under in fossil fuelled power stations induce type IV cracking. This type of cracking occurs in the intercritical or fine grain region of the heated affected zone via a creep mechanism, and results in fractures with relatively little total cross-weld strain. Despite the occurrence of type IV cracking experienced in lower alloy predecessors, successor alloys have been introduced and widely used with insufficient consideration given to the consequences of welding them. ...

Review of type IV cracking of weldments in 9–12%Cr creep strength enhanced ferritic steels

In this work, examinations on the microstructure and mechanical properties of plain carbon steel and AISI 430 ferritic stainless steel dissimilar welds are carried out. Welding is conducted in both autogenous and using ER309L austenitic filler rod conditions through gas tungsten arc welding process. The results indicate that fully-ferritic and duplex ferritic–martensitic microstructures are formed for autogenous and filler-added welds, respectively. Carbide precipitation and formation of martensite at ferrite grain boundaries (intergranular martensite) as well as grain growth occur in the heat affected zone (HAZ) of AISI 430 steel. It is found that weld heat input can strongly affect grain growth phenomenon along with the amount and the composition of carbides and intergranular martensite. Acquired mechanical characteristics of weld in the case of using filler metal are significantly higher than those of autogenous one. Accordingly, ultimate tensile strength (UTS), hardness, and absorbed energy during tensile test of weld metal are increased from 662 MPa to 910 MPa, 140 Hv to 385 Hv, and 53.6 J m −3 to 79 J m −3 , respectively by filler metal addition. From fracture surfaces, predominantly ductile fracture is observed in the specimen welded with filler metal while mainly cleavage fracture occurs in the autogenous weld metal.

Study on microstructure and mechanical characteristics of low-carbon steel and ferritic stainless steel joints

http://www.fem.unicamp.br/~giorgia/Lakshminarayanan%202010.pdf

An assessment of microstructure, hardness, tensile and impact strength of friction stir welded ferritic stainless steel joints

Mechanical properties of creep enhanced ferritic (CSEF) steels is affected by various parameters, the solutionizing temperature is one of them. The present work demonstrates the effect of solutionizing temperature on microstructure and mechanical properties of CSEF P91 steel. Optical metallography (OM) and Scanning electron microscopy (SEM) were carried out to study the microstructure of P91 steel in different heat treatment conditions. In order to determine the precipitates present in microstructure; X-ray analysis was performed. Moreover, the influence of solutionizing temperature on the mechanical properties (strength, hardness and impact toughness) has also been studied.

Effect of normalizing temperature on microstructural stability and mechanical properties of creep strength enhanced ferritic P91 steel

Laser welding of modified 12% Cr stainless steel: Strength, fatigue, toughness, microstructure and corrosion properties

Parameter optimisation for automatic pipeline girth welding using a new friction welding method

Creep resistant steels for high temperature service are a vital part in the construction of power stations. The possibilities to increase steam parameters of new boilers are restricted if pressure and temperature in the membrane water-walls cannot be simultaneously increased. The increase of steam parameters requires the development of new high strength and creep resistant materials. This paper gives data on weldability, mechanical properties, toughness and high temperature behaviour (creep) of new materials T/P 24 (7CrMoVTiB10-10) which have been developed by Vallourec & Mannesmann Tubes, and T/P 23 (7CrWVMoNb9–6). It is the outcome of a research project of the Belgian Welding Institute in collaboration with Laborelec and with industrial partners. Both base metals and weldments in tubes and thick walled pipes have been investigated.

New Generation 21/4Cr Steels T/P 23 and T/P 24 Weldability and High Temperature Properties

This article deals with the plasma arc welding properties of 6 mm thick modified X2CrNi12 stainless steel conforming to the grades EN 1.4003 and UNS S 41003 with carbon content below 0.015% to improve the weldability. The butt welds produced without filler metal and with AISI 316L austenitic type of consumable were subjected to tensile and bend tests as well as Charpy impact toughness testing. Examinations including fractography, metallography, chemical analysis of the weld metal, ferrite content, grain size, and hardness analyses were carried out. Sound plasma arc welded joints of modified 12 Cr revealed the microstructure-property relationship, such as high ferrite content (≥ 70%) resulting in ferrite grain coarsening mainly at the high temperature heat-affected zone (HTHAZ) has no adverse effect on tensile or bend properties, but has negative effects on low temperature toughness. Enhanced toughness was provided in case of the low temperature heat affected zone (LTHAZ) with finer grained microstructure....

Alfred Dhooge

Papers

Laser welding of modified 12% Cr stainless steel: Strength, fatigue, toughness, microstructure and corrosion properties

Parameter optimisation for automatic pipeline girth welding using a new friction welding method

New Generation 21/4Cr Steels T/P 23 and T/P 24 Weldability and High Temperature Properties

Plasma Arc Welding of Modified 12%Cr Stainless Steel

Hybrid (plasma + gas tungsten arc) weldability of modified 12% Cr ferritic stainless steel