Method for manufacturing a large-sized seamless dome, and corresponding dome

A method for manufacturing a hollow piece comprising a single seamless wall in a shape of a dome extending around a central axis, the wall being made of a material constituted of a metal alloy, the wall having an average thickness of less than 50 mm and a larger dimension, orthogonal to the central axis, of between 1500 mm and 3700 mm, the method comprising the following consecutive steps:

• providing a semi-finished product of said material;
• hot forging by upsetting the semi-finished product to form a blank with a developed surface greater than a developed surface of the semi-finished product and less than a developed surface of the wall;
• hot forming of the blank to create a preform having a developed surface less than or equal to the developed surface of the wall, the preform comprising at least two consecutive portions extending radially in the continuation with one another away from the central axis, so that for all the portions, an average thicknesses and/or convexities of two consecutive portions are distinct;
• hot deformation of the preform under a press between a die and a punch to form the wall.