Austenitic stainless steels

Abstract

An austenitic stainless steel excellent in high temperature strength, high temperature ductility and hot workability, consisting of, by mass %, C: more than 0.05% to 0.15%, Si: 2% or less, Mn: 0.1 to 3%, P: 0.04% or less, S: 0.01% or less, Cr: more than 20% to less than 28%, Ni: more than 15% to 55%, Cu: more than 2% to 6%, Nb: 0.1 to 0.8%, V: 0.02 to 1.5%, sol. Al: 0.001 to 0.1%, but sol.Al<=0.4xN, N: more than 0.05% to 0.3% and O (Oxygen): 0.006% or less, but O<=1 / (60xCu), and the balance Fe and impurities. The austenitic stainless steel may contain at least one of Co, Mo, W, Ti, B, Zr, Hf, Ta, Re, Ir, Pd, Pt and Ag, and / or at least one of Mg, Ca, Y, La, Ce, Nd and Sc.

Description

technical field [0001] The present invention relates to austenitic stainless steels used as steel pipes for power generation boilers, chemical industry equipment, etc., steel plates for heat-resistant and pressure-resistant parts, bar steel, forged steel products, etc., and particularly relates to creep strength, creep Austenitic stainless steel with excellent fracture ductility and hot workability. Background technique [0002] In the past, 18-8 series austenitic stainless steel such as SUS304H, SUS316H, SUS321H, SUS347H, etc. was used as the material of equipment used in boilers and chemical equipment used in high-temperature environments. However, in recent years, the operating conditions of devices in such a commercial temperature environment have become more and more harsh, and the requirements for the properties of materials used have also become stricter. Therefore, the high-temperature strength, especially the creep strength, of the previously used 18-8 series auste...

AI Technical Summary

Problems solved by technology

[0006] However, none of these steels have improved the hot workability very well, especially the workability at high temperatures above 1200°C

Generally, when using materials with poor thermal processing properties to manufacture jointless pipes, hot extrusion is often used to make pipes, but due to the heat generated by processing, the temperature inside the material will rise further relative to the heating temperature, so if it is above 1200°C Insufficient workability, will break in two or produce internal defects