Treating Effect #16
Post weld heat treatment will for the most part bring about a change of the microstructure of both the weld metal and warmth influenced zone Except for the 9Cr1Mo and 12Cr1MoV materials, the microstructure of every other material ought to contain a blend of ferrite and iron or combination carbide.
The impact of present moment (1 to 2 hours) post-weld heat treatment on the carbide is by and large gainful, while longer occasions bring about a decrease in durability due to spheroidising impacts. The ordinary microstructure for the parent, weld and HAZ for the 9Cr1Mo and 12Cr1MoV materials are martensite and post weld heat treatment is significant in these materials to temper the martensite stage. Impact on Mechanical Properties As a progression of general articulations, the following are the results of post-weld heat treatment contrasted and the as-welded condition:
Ò Yield quality is diminished somewhat, the impact tumbling off reasonably quickly with time.
Ò The rigidity is diminished.
Ò The malleability is expanded.
Ò Hardness levels are decreased.
Ò Toughness is somewhat diminished at short times yet the impact can be critical over longer occasions.
Impact on Creep Properties
For creep opposing material, post-weld heat treatment is required so as to completely build up the wet blanket quality. This is particularly valid for thicker segments, for example, headers.
There has been an inclination lately to permit postponing of the post-weld heat treatment organize for more slender materials utilized normally for superheater and reheater curls in the Power Generation industry, yet an assortment of conditions must be met……………. continue
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