About the possibility of using annealing in the restoration of products obtained from sheet brass subjected to cracking

The article is devoted to the study of the possibility of restoration by annealing of museum exhibits obtained from sheet brass with the application of pressure treatment аnd subjected to spontaneous cracking during storage. Restoration of similar products is associated with great difficulties since in the process of soldering cracks and straightening deformations they are distributed to other parts of the products. Тhe article is the result of research conducted and published by the author earlier, it was first established that the destruction of the exhibits is caused by corrosion cracking related to the presence of residual internal stresses in them and dezincinig. In this paper, the main attention was paid to the study of the possibility of eliminating internal stresses in products by annealing. The expediency of its application was tested on samples selected from cracked brass salaries originating from the funds of the The State Research Institute for Conservation. To determine the composition of the samples we used scanning electron microscope HitachiTM 4000 Plus with an attachment for electron-probe analysis Quaniax 75 (Bruker), the microstructure was studied by metallographic method on a microscope MIM-8, the stress level was assessed by measuring microhardness. Annealing was carried out in an electric muffle furnace at temperatures 200-700оС for various times. As a result of the research, the author came to the conclusion that in most cases annealing at 400оС for 15 min is sufficient to relieve internal stresses.