Lean duplex stainless steel having superb drawing property and method for producing same

Abstract

Provided are lean duplex stainless steel in which delayed fracture does not occur and thus a drawing property is improved, and a method for producing the lean duplex stainless steel. The lean duplex stainless steel having a superb drawing property according to the present disclosure includes, in weight %, C: 0.02% to 0.08%, Si: 0.5% to 1.3%, Mn: 2.5% to 3.5%, Cr: 19% to 21%, Ni: 0.6% to 1.2%, N: 0.2% to 0.3%, Cu: 0.5% to 1.2%, and the remainder of Fe and other inevitable impurities, and, as annealed dual-phase steel of ferrite and austenite, Md_SIM10 corresponding to a temperature measured when an amount of strain-induced martensite formed after 0.3 true strain reaches 10%, and a limit drawing ratio (LDR) satisfy the expressions below. −30° C.Md_SIM10≦0° C. - - - (expression 1) and 2.08≦LDR≦2.18 - - - (expression 2)

Description

TECHNICAL FIELD[0001]The present disclosure relates to lean duplex stainless steel having a superb drawing property and a method for producing the same.BACKGROUND ART[0002]Austenitic stainless steel having favorable workability and acid resistance generally contains Cr and Ni as main raw materials with iron (Fe) as a base metal. In addition, austenitic stainless steel has been developed into various steel types suiting for various applications by adding other elements such as Mo and Cu.[0003]Such austenitic stainless steel types are a steel type having excellent acid resistance and pitting corrosion resistance, and contains a Ni component in 8% or greater in weight % while being low carbon. This causes a problem of reducing price competitiveness due to the high range of fluctuation in costs with an increase in the Ni price.[0004]Accordingly, development of new steel types capable of securing equal or higher acid resistance compared to austenitic stainless steel types while lowering ...

AI Technical Summary

Benefits of technology

This patent aims to save resources and reduce costs by controlling the content of certain alloy components. By doing so, it improves workability and makes the material more resistant to damage.

Problems solved by technology

This causes a problem of reducing price competitiveness due to the high range of fluctuation in costs with an increase in the Ni price.

Such duplex stainless steel causes an increase in the manufacturing costs due to high-priced elements such as Ni and Mo, and also causes reduction in the price competitiveness compared to other steel types by consuming Ni, Mo and the like.

Recently developed lean duplex stainless steel has been widely used mostly in storage containers, transport containers and the like, however, like other common duplex stainless steel, such lean duplex stainless steel has a problem of formability limit compared to austenite-based.

Accordingly, elongation is enhanced when controlling a process curing rate by controlling the amount of the strain-induced martensite formed during deformation, however, when used for a drawing, there is a problem in that process-induced martensite is formed by cup drawing processing causing delayed fractures.

Stress corrosion resistance is also more superior than design requirements providing technical solutions, however, formability, a factor relating to workability, is inferior than in austenitic stainless steel.

This causes many restrictions in the use in various industrial fields requiring forming, bending and the like, which is not feasible in economic aspects.

Particularly, austenitic stainless steel having excellent formability contains 4% or higher of high-priced Ni and therefore, there are problems in that material costs are very high when manufactured, and Ni and the like that are precious resources are consumed in large quantities.

In addition, a large quantity of Mn greatly increases nitrogen solid solubility of steel for securing acid resistance of lean duplex stainless steel, but has a problem of inhibiting acid resistance by readily forming inclusions such as MnS harmful for acid resistance.

Environmental problems also occur due to Mn dust particles and the like produced during electric furnace operations.

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