Smelting method for steel used for low-temperature pressure container

Abstract

A smelting method for a low-temperature pressure vessel steel is to add the molten steel which is smelted in a rotating furnace into a VOD furnace to refine. VOD refining is to pump vacuum in advance, and then to conduct bottom argon blowing and arbed lance oxygen blowing, so as to decarbonizes the steel to 0.080 to 0.010percent; after oxygen blowing, the argon is blew from bottom and boils; and then reduction is conducted; during the reduction period, lime, fluorite and silicoferrite needed to be prepared are added as the first batch; next, the lime, fluorite, ferromanganese iron and aluminum are added as the second batch; and then the two batches of materials are forcefully stirred; finally a steel ladle is closed and the argon is blew from bottom, and a steel surface breaks after calming down; the components (weight) of the outgoing molten steel are as follows: C: 0.030 to 0.050percent, Si: 0.15 to 0.25percent, Mn: 0.55 to 0.65percent, P: less than or equal to 0.005percent, S: less than or equal to 0.001percent, Al:0.01 to 0.03percent, Ni: 9.00 to 9.50percent, Cr: less than or equal to 0.10percent, N: less than or equal to 0.002percent, H: less than or equal to 0.0001percent, O: less than or equal to 0.0012percent. The smelting method for a low-temperature pressure vessel steel can reduce the content of S and N in steel, and the rate of sub-surface crack of cast ingots.

Description

technical field [0001] The invention relates to a method for smelting steel for low-temperature pressure vessels, in particular to a method for smelting 9% Ni steel for low-temperature pressure vessels. Background technique [0002] With the development of the economy, the demand for energy is gradually increasing. In order to maintain a good ecological environment, liquefied natural gas has attracted much attention as a clean energy. For this reason, construction projects for liquefied natural gas (LNG) storage tanks are also increasing. 9% Ni steel has good cold workability, weldability and crack growth resistance, and also has good low temperature performance. Compared with austenitic stainless steel, at the ultra-low temperature of -196°C, not only the low-temperature toughness is better than austenitic stainless steel, but also the yield strength is more than twice that of austenitic stainless steel, which is ideal for manufacturing LNG storage tanks for low-temperatur...

AI Technical Summary

Problems solved by technology

The existing production process route of 9% Ni steel for low-temperature pressure vessels is: molten iron pretreatment→converter smelting→RH refining→continuous casting. Due to the poor effect of removing [S] and [N] during refining, [ The sum of S]+[N] exceeds 50ppm, even if [P]≤20ppm in the steel, under the same process conditions of continuous casting and slow cooling of the casting slab, subcutaneous cracks will occur in the continuous casting slab