Production method for steel ingot of large-sized high-nitrogen retaining ring steel

Abstract

The invention relates to a production method for a steel ingot of large-sized high-nitrogen retaining ring steel. The production method comprises the following steps: 1) smelting and casting: optimizing raw materials, primarily smelting molten steel EAF by using an electric arc furnace, refining AOD and LF by using a ladle furnace, performing die casting on ICM and pouring an electrode of phi 422 to 510 mm; 2) performing hot charging and annealing; 3) remelting electroslag into the steel ingot of phi 660 to 800 mm; and 4) sampling, detecting the components, performing flaw detection, peeling electroslag and steel ingot sand, detecting size and appearance and putting into a storage. In the steel ingot of the high-nitrogen retaining ring steel manufactured by the method, the phi is 660 to 800 mm, the weight is more than 5 tons, the nitrogen content is over 0.6 weight percent, the nitrogen is distributed into the steel ingot uniformly, and the |[N] head-[N]tail| of the head and the tail of the steel ingot is less than or equal to 0.05 weight percent.

Description

technical field [0001] The invention relates to the field of high-nitrogen steel, and mainly relates to a production method of a generator retaining ring steel ingot with a nitrogen content higher than 0.6 wt% and uniform distribution (the steel ingot size is φ660-800 mm and the weight is higher than 5 tons). Background technique [0002] The retaining ring is the most critical part of the turbogenerator, and it is also the part subjected to the greatest force. When the generator is running at rated speed, the load on the retaining ring is 2 / 3 of the yield limit. When the unit is larger, the stress on the retaining ring also increases due to various reasons. Due to its function and stress state, the retaining ring must have super high strength, good plasticity, non-magnetism and excellent stress corrosion resistance. Therefore, people have developed an austenitic 18Mn-18Cr-N type retaining ring material, which has been widely used in the retaining rings of large and super ...

AI Technical Summary

Problems solved by technology

The existing problem is that when the size of the steel ingot is relatively large, on the one hand, nitrogen is easy to precipitate during the casting process of the electrode rod, forming holes, which makes the electrode rod easy to fall off in the subsequent electroslag process, resulting in poor quality of the produced steel ingot; on the other hand, In the electroslag process, due to the current distribution of the electrode cross section, the temperature distribution of the electroslag bath is not uniform, resulting in the nitrogen content is not easy to control

[0005] In summary, the current production methods of conventional high-nitrogen (nitrogen content less than 0.6wt%) retaining ring steels cannot meet the microstructure and performance requirements of large-scale high-nitrogen retaining ring steels with nitrogen contents in the range of 0.6-0.7wt%. However, some special equipment is still in the stage of laboratory application or requires expensive equipment investment, so it is urgent to find a smelting method with low production cost, uncomplicated process and no need for expensive equipment investment, so that the nitrogen content is between 0.6 and 0.7wt%. Range of large-gauge high-nitrogen retaining ring steel

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