A super duplex stainless steel and its alloy composition optimization design method

Abstract

The invention relate to an optimization design method for ultra-super duplex stainless steel and alloy components of the ultra-super duplex stainless steel. The ultra-super duplex stainless steel comprises, by weight percentage, 0.004-0.020% of C, 26.00-37.00% of Cr, 5.50-11.00% of Ni, 2.50-6.50% of Mo, 0.50-2.50% of W, 0.25-0.65%of N, 0.50-3.50% of Mn, 0.50-2.50% of Cu, 0.50-2.00% of Co, 0.10-0.55% of Si, smaller than 0.03% of P, smaller than 0.02% of S, smaller than 0.015% of B, 0.005-0.008% of Mg, smaller than 0.015% of Ca, 0.03-0.10% of RE and the balance Fe and other inevitable impurities. The ultra-super duplex stainless steel has the beneficial effects of being good in structure stability, high in high-temperature oxidation resistance, good in hot workability, excellent in stress corrosion resistance and the like and is suitable for extremely harsh service environments with the high temperature, high pressure, high chloride ion and strong acidity.

Description

technical field [0001] The invention relates to a super super duplex stainless steel and an optimization design method for its alloy composition, belonging to the technical field of duplex stainless steel. Background technique [0002] In the extremely harsh service environments such as urea production, oil exploration and deep-sea exploration, such as high temperature, high pressure, and high chloride ions, the existing steel types are difficult to meet the application requirements, and the cost of nickel-based alloys and other materials is very high, so it is urgent to develop a new one. A new type of material that can meet production and application requirements and is relatively low in cost. Super duplex stainless steel is a newly developed steel grade. This steel has excellent corrosion resistance, good plasticity and toughness, and its resistance to chloride stress corrosion cracking is significantly better than that of some austenitic stainless steel or Super duplex ...

AI Technical Summary

Problems solved by technology

[0003] However, there are still many problems in the production and application of ultra-super duplex stainless steel, which limit its development.

First, during thermal processing or heat treatment (generally greater than 980 °C), high Mo content easily leads to the formation of volatile MoO 3 , destroy the protective oxide layer, thereby seriously deteriorating the high temperature oxidation resistance of steel

Secondly, the difference in the crystal structure of ferrite and austenite leads to significant differences in the high-temperature softening mechanism. The softening mechanism of ferrite is dynamic recovery, and the softening mechanism of austenite is dynamic recrystallization. Poor coordination ability, easy to produce stress concentration at the phase boundary; and because the high alloy content increases the deformation resistance of the steel, the hot workability of the steel is very poor

Third, with the development of modern industry, the corrosion environment is more harsh. High temperature, high pressure, high chloride ion, and strong acid environment can easily cause stress corrosion of steel, reduce service life, and increase maintenance costs. Therefore, the steel still faces serious problems. Tendency to stress corrosion damage

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