The present invention relates to a reinforced bulging tank of a launch vehicle and a manufacturing method therefor. The tank is made of metal material with good plasticity. Firstly, the tank is manufactured by welding annealed plastic metal materials, wherein internal longitudinal reinforcing ribs and internal annular frames/annular plates of barrel sections are welded with a barrel section shell by a low energy laser welding method, and tank bottoms are progressively welded by a plurality of conical sections. Weldments are strengthened and formed through internal pressure bulging under the constraint of external tooling. The outer walls of the barrel sections are not radially deformed under the constraint of a plurality of small width metal rings, and the metal rings are not connected to each other axially. The strength of the materials can be greatly improved by a deep cooling bulging technology.

The present invention relates to a reinforced bulging tank of a launch vehicle and a manufacturing method therefor. The tank is made of metal material with good plasticity. Firstly, the tank is manufactured by welding annealed plastic metal materials, wherein internal longitudinal reinforcing ribs and internal annular frames/annular plates of barrel sections are welded with a barrel section shell by a low energy laser welding method, and tank bottoms are progressively welded by a plurality of conical sections. Weldments are strengthened and formed through internal pressure bulging under the constraint of external tooling. The outer walls of the barrel sections are not radially deformed under the constraint of a plurality of small width metal rings, and the metal rings are not connected to each other axially. The strength of the materials can be greatly improved by a deep cooling bulging technology.

A method for producing a steel part and corresponding steel part includes casting a steel having a composition comprising: 0.10%C0.35%, 0.8%Si2.0%, 1.8%Mn2.5%, P0.1%, 0%S0.4%, 0%Al1.0%, N0.015%, 0%Mo0.4%, 0.02%Nb0.08%, 0.02%Ti0.05%, 0.001%B0.005%, 0.5%Cr1.8%, 0%V0.5%, 0%Ni0.5%, to obtain a semi-product, hot rolling the semi-product at a hot rolling starting temperature higher than 1000 C. and cooling the product through air to room temperature to obtain a hot rolled steel part having a microstructure consisting of 70% to 90% of bainite, 5% to 25% of M/A compounds and at most 25% of martensite. The bainite and the M/A compounds contain retained austenite such that the total content of retained austenite in the steel is comprised between 5% and 25%, the carbon content of the retained austenite being comprised between 0.8% and 1.5%.