Ferrite joint

A lanthanum calcium ferrite (LCF) perovskite system (LaxCai-xFeOs) was joined to itself to demonstrate the feasibility of the TLP method. LCFs can be used as a component of air separation membranes, so the assemblies need to operate at high temperatures. Therefore the joint interface needs to resist creep, avoid problems with thermal cycling, and be chemically stable in the high-temperature environment. Ideally, the interface in such systems is the same as the parts in the assembly. 

The ferritic welds fractured at 77 K in the base metal, while those with austenitic welds fractured in the weld at 293 K and in the base metal at 77 K. Joints with a nickel-base weld on full-scale specimens were fractured in the base metal at 77 K. 

Temper EMBRin cement. The phenomenon of temper embrittlement occurs when hardenecarbon structural steel is K>led slowly or l ld within a critical range of temperatures below the temperature at which austenite is transformed to ferrite. This critical temperature range usually occurs in somewhere between 850 and 1100° F. Welded joints and at elevated temperatures are... 

Evaluation of the integrity of welded joints is one of the most important subjects with regard to conventional ferritic-martensitic steels. In the applications where cyclic thermal transients are the major source of loading, creep—fatigue interaction, besides creep, could be of prime importance just like the base metal. 

When ferritic-martensitic steels are used for structural components, usually dissimilar welded joints with austenitic stainless steels are used, too. When these are subject to elevated temperatures, creep property evaluation and creep-fatigue evaluation are needed. In the case of dissimilar welds, close attention should be paid to the location of failure. Under certain conditions, failure could occur at the interface between the two materials [27]. 

Ferritic stainless steel. The main problem when welding ferritic stainless steel is poor HAZ toughness. Excessive grain coarsening can lead to cracking in highly restrained joints and thick-section material. When welding thin-section material (less than 6 mm), no special precautions are necessary. 

Once duplex base metal and welding consumables have been selected, it is then necessary to select joint designs and weld parameters that will produce welding heat inputs and cooling rates so as to produce a favorable balance of austenite and ferrite in the weld and HAZ. 

Heat treatment of welded joints between dissimilar ferritic metals or between ferritic metals using dissimilar ferritic filler metal should be at the higher of the temperature ranges in Table 11.13 for the materials in the joint. 

Heat treatment of welded joints including both ferritic and austenitic components, and filler metals should be as required for the ferritic material or materials unless otherwise specified in the engineering design. 

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