After-forging grain-refining strength-toughening treatment process of 1Mn18Cr18N steel guard ring for generating set

Abstract

The invention discloses a fine grains strengthening-toughening process after forging a 1Mn18Cr18N steel shroud ring rolling piece for manufacturing a generating set, comprising the steps of: cold pre-deforming and solution heat treating the rough machined 1Mn18Cr18N steel shroud ring rolling piece, and sampling testing the solution heat treating effect. According to the invention, austenitic steel forging piece which is essentially coarse grains and can not refine grains by heat treatment has fine and uniform grains before cold deformation strengthening, thus to greatly improve the strength, plasticity and toughness of the forging piece, as well as strengthen the quality controllability.

Description

technical field [0001] The invention relates to a manufacturing technology of a steel retaining ring forging used in a steam turbine generator set or a nuclear power plant, and mainly relates to a fine-grain strengthening and toughening treatment process for a 1Mn18Cr18N steel retaining ring forging used in a generator set after forging. technical background [0002] At present, the post-forging treatment methods of the retaining ring in the forging manufacturing industry of domestic and foreign steam turbine generator sets are mainly: air cooling treatment or water cooling deformation heat treatment after forging, solution heat treatment after rough machining, and then directly enter the cold deformation strengthening process. Since the forging method of the forging is to adopt the ordinary 10,000-ton free forging hydraulic press with small deformation and multiple fires, the forging will be stopped at any time for the cracks generated during the forging. Or water-cooled de...

AI Technical Summary

Problems solved by technology

Since the forging method of the forging is to adopt the ordinary 10,000-ton free forging hydraulic press with small deformation and multiple fires, the forging will be stopped at any time for the cracks generated during the forging. Or water-cooled deformation heat treatment, but the ordinary 10,000-ton free forging hydraulic press is slow in action, and it is easy to cause forging cracks for 1Mn18Cr18N steel with a narrow forgeable temperature range and is easy to crack. Insufficient forging ratio, metal defects are difficult to forge, uneven deformation, coarse and uneven grains and other internal quality problems and production efficiency problems of forgings; while flame or arc gouging is used to remove forging cracks, resulting in stress concentration and overheating in the heat-affected zone Burning defects make repeated cracking in the forging process after clearing the cracks, aggravating the above-mentioned internal quality problems and production efficiency problems; carbides precipitate on the grain boundaries in large quantities when air-cooled after forging, and the grains grow further, even after forging. The water-cooled deformation heat treatment process solves the problem of carbide precipitation and further grain growth, but because the 10,000-ton hydraulic press moves slowly and may stop forging to remove cracks at any time, it cannot guarantee both a certain amount of deformation and a certain deformation temperature necessary for deformation heat treatment. Under large conditions, deformation heat treatment cannot be realized stably, and the coarse and uneven grains formed during the forging process cannot be refined and homogenized, so the subsequent solution treatment must be kept at high temperature for a long time to cause the grains to become coarser and make the cold deformation The strength of the blank before strengthening is low, and the plastic toughness is poor. On the one hand, because the plastic toughness before strengthening is poor, the plastic toughness of the product after strengthening is at a low level. On the other hand, because the strength before strengthening is low, it must meet the product requirements The strength requirement requires a larger amount of cold deformation, and with the increase of the amount of cold deformation, the plasticity and toughness of the product are further reduced and cannot reach the required value of plasticity and toughness specified by the product.