Welds heat treatment

Fabricated casings shall be post-weld heat treated. Repairs greater than 10 in. in size shall be post-weld heat treated. All post-weld heat treatment shall be performed in accordance with ASME BPV Code. 

This alloy has a nominal composition of 65% nickel, 28% molybdenum and 6% iron. It is generally used in reducing conditions. It is intended to work in very severely corrosive situations after post-weld heat treatment to prevent intergranular corrosion. These alloys have outstanding resistance to all concentrations of hydrochloric acid up to boiling-point temperatures and in boiling sulfuric acid solutions up to 60% concentration. 

Ferritic type. Welding produces a brittle deposit and a brittle heat-affected zone caused by the very large grain size that is produced. The problem may be reduced in severity by the use of austenitic fillers and/ or the application of pre- and post-weld heat treatments the latter is a serious limitation when large welded structures are involved. 

Steel may have some merit SSCC of weld repairs in well-head alloys was investigated by Watkins and Rosenberg who found that the repairs were susceptible to this problem because of the hard HAZs developed by welding. Post-weld heat treatment was an essential but not complete cure compared with unrepaired castings. In the case of hydrogen-assisted cracking of welded structural steels, composition is more important than mechanical properties and the carbon equivalent should be... 

The local heating, and consequent expansion, that occurs during welding can leave the joint in a state of stress. These stresses are relieved by post-welding heat treatment. Not all vessels will be stress relieved. Guidance on the need for post-welding heat treatment is given in the codes and standards, and will depend on the service and conditions, materials of construction, and plate thickness. 

Port weld heat treatment Yes No Temperature/Time °F/hrs. 

Inspections by owner include inspections, verifications, and audits of the construction of piping systems, which include fabrication, welding, heat treatment, assembly, erection, examination, and testing, in addition to the construction organization s documented procedures, personnel qualifications, and quality control records. 

Post-weld heat-treatment Applicable material specification or ASME VIII, Division 1, UW40... 

The drawing shall show weld designs, size, materials, and pre-weld and post-weld heat-treatments. 

If specified, proposed connection designs shall be submitted to the purchaser for approval before fabrication. The drawing shall show weld designs, size, materials, and pre-weld and post-weld heat-treatments. 

Manufacturing aspects of materials improper metal working, welding, heat treatment or casting results in inherent flaws... 

Stress corrosion cracking can be avoided by selecting materials that are not susceptible in the specific corrosion environment or, less certainly, by stress relieving by post-weld heat treatment. 

Key words titanium, alloys, properties, strength, fatigue, welding, heat treatment. 

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