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POST WELD HEAT TREATMENT #31

Methods FOR WELD REPAIR WITHOUT POST WELD HEAT TREATMENT Endeavors to accomplish acceptable outcomes from weld fixes where post-weld heat treatment has been overlooked are not new. A significant part of the unique work completed for the Nuclear The industry started in the mid-1980s and Code Case N-432 for a restricted scope of materials under […]

POST WELD HEAT TREATMENT #31

Methods FOR WELD REPAIR WITHOUT POST WELD HEAT TREATMENT

Endeavors to accomplish acceptable outcomes from weld fixes where post-weld heat treatment has been overlooked are not new. A significant part of the unique work completed for the Nuclear The industry started in the mid-1980s and Code Case N-432 for a restricted scope of materials under ASME III in the United States was built up in 1986. From that point forward, the different strategies have been refined and received into different measures, for example, ASME B 31.1, B 31.3 and even ASME XI. A portion of the better-realized strategies will be analyzed in more detail.

Half dot system :

This procedure was created utilizing the protected metal circular segment (SMAW) process and was basically planned for giving an option in contrast to the utilization of post-weld heat treatment. The system was initially produced for use in the atomic business, in any case, has since gotten generally utilized for fixes to channeling, headers and turbine housings in customary force plants and other businesses. The SMAW procedure, as a rule, utilizes the utilization of expanding distance across terminals, beginning with a 2.5 mm, at that point a 3.2 mm and completing with a 4.0 mm.
The region to be fixed is preheated to temperature compared with the material also, thickness, and a buttering procedure utilized as a first layer with the 2.5 mm terminal. The reason for existing is to create a little, shallow warmth influenced zone. The following stage is to expel roughly 50% of the thickness of each run by crushing. The second layer kept utilizing 3.2 mm cathodes viably re-changes the coarse-grained heat influenced zone and the first layer, and the third go with the 4.0 mm cathode further tempers the warmth influenced zone. Each resulting layer changes and tempers the layers underneath in an ordinary way.

The significant bit of leeway of the method is that the durability of the warmth influenced zone is extensively improved over customary techniques, yet the inconveniences incorporate the certainty that a ton of granulating is required, and exact crushing at that. Not exclusively is this tedious, yet in the event that an excess of material is expelled from the main layer, the impacts of the re-change may not be as fruitful as may be normal.

Reliable layer temper globule procedure :

This method uses either the SMAW or the GTAW procedure and was created by EPRI in the mid-1990s to guarantee that sturdiness property in both the warmth influenced zone and the weld metal were at the least equivalent to the sturdiness properties of the unique base material. The method includes storing weld layers that are adequately thick that the ensuing weld layer just tempers the warmth influenced zone brought about by the primary layer. The temperature is not planned to surpass the AC1 so no grain refinement happens, and the impact is basically like post-weld heat treatment. The method delivers a warmth influenced zone microstructure that comprises dominatingly of tempered martensite with limited quantities of bainite, bringing about great sturdiness properties.

Substitute temper dot procedure:

This method was likewise evolved under the EPRI program yet explicitly for carbon-manganese and carbon-molybdenum materials utilized in the atomic reactor pressure vessel parts. It used the programmed GTAW process and was an option to the half dot method for use in regions of high radiation presentation. The method includes setting up the territory to be fixed so that at least six buttering layers can be performed. A preheat of 1500 C least is applied,
what’s more, the warmth contribution of each layer is controlled to inside 10% of that deliberate in the technique capability test. On the off chance that more than six layers are utilized, a similar command over warmth input is required. The last advance is a low-temperature post-weld heat treatment at 230 – 2900 C. The point is to deliver treating utilizing a few weld layers with the goal that each resulting layer enters the past layer to create covering temperature profiles. Nonetheless, the AC1 is surpassed, coming about in re-change and grain refinement of the warmth influenced zones. Once in awhile, diverse warmth inputs are utilized for the first three layers, beginning with a low warmth contribution to limit the degree of the warmth influenced zone in the parent material. The warmth contribution for the second layer is expanded to give a marginally thicker store while still re-changing the parent heat influenced zone and the third a layer is as yet thicker to guarantee to treat as it were of the warmth influenced zone.

POST WELD HEAT TREATMENT #31 2

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