Here is the selection method of cobalt-based welding consumables in the manufacture of nuclear power equipment. Similar industries can also learn from reference.
In nuclear power plant pressure vessels, for its internal components, such as the core plate guide pin on the austenitic stainless steel, the wear layer of the upper core plate embedded key and the support pin, and the Inconel-600 nickel alloy U-shaped embedded key The wear-resistant layer, in addition to the claws, valves, etc. in the control rod drive mechanism are all surfacing with cobalt-based alloy welding materials.
Surfacing methods are: manual or automatic tungsten argon arc welding, manual arc welding surfacing. Surfacing electrodes are: Stellite6, Stellite12, Stellite1, etc., surfacing welding wire: ERCoCr-A, ERCoCr-B, ERCoCr-D, ERCoCr-E. Usually, 2 to 3 layers are surfacing, and different welding materials can be used for each layer as needed.
When the cobalt-based alloy electrode is surfacing, the DC reverse connection is adopted, and the tungsten argon arc welding is performed by the DC positive connection. In order to prevent cracking, preheating should be carried out before surfacing, and should be slowly cooled after welding or after stress relief treatment. After the cobalt-based alloy is surfacing, it is generally put into operation in the as-welded state. In the case of large-area surfacing, the stress relief treatment should be carried out, or the same post-heat treatment as the preheating temperature should be used, and the temperature is about 350-450 °C.
EDCoCr cobalt-based alloy welding rod or ERCoCr cobalt-based alloy welding wire deposited metal has excellent comprehensive performance, heat resistance, wear resistance and corrosion resistance, and maintains high hardness at high temperature. Generally, the cobalt-based alloy welding material contains 25 to 33% of Cr and 3 to 14% of W, which improves the oxidation resistance and high temperature strength of the material, and the cobalt itself has corrosion resistance. Under these conditions, a high quality welded joint can be welded using a cobalt-based alloy consumable and properly mastered the welding process.
In the nuclear island main equipment, welding materials containing EDCoCr-A and ERCoCr-A with a volume of 3 to 6% are generally used, and the HRC is 40 to 50. The hardness of the surfacing layer fluctuates between 28 and 33 at 350 °C. Fully meet the wear and corrosion resistance requirements at the working temperature. Electrodes such as ECoCr-B and ECoCr-C are also used in actual production.
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