Investigation of Microstructure and Mechanical Properties of Austenite Stainless Steel 304 during Tempering and Cryogenic Heat Treatment

P Bobba,S Tummala,S Singh,S Kosaraju,Anitha Lakshmi,Ram Subbiah,Ch Bandhavi,Swathi Swathi,Tanya Buddi

doi:10.1051/e3sconf/202018401006

Abstract

In the present study, the influence of heat treatment (tempering & cryogenic) on the grain orientation and few important mechanical properties of Austenite Stainless Steel 304 (ASS 304) are examined. The significant mechanical properties like ultimate strength, elongation percentage and surface hardness etc., of the experimented and untreated specimens are computed using pre standard methods and the micrographs of the specimens was conducted using metallurgical microscope. The effect of strain rate ranging from lower to higher strain rates 0.001s-1 to 0.1s-1, on true stress - true strain behaviour of tempered austenitic stainless steel 304 is investigated. Experimental results exhibited that the mechanical behaviour of ASS 304 can be reformed and improvised by several heat treatment procedures for a specific application. The results showed that the cryogenic treated specimens indicate lowest tensile strength, hardness and highest percent of elongation value compared with tempered specimen gave the maximum tensile strength, hardness and minimum percent of elongation in length value.

Highlights

Heat Treatment of engineering materials is a combination of coordinated heating along with cooling of a specific alloy or solid metal such that it produces required microstructure and desirable mechanical properties like stiffness, yield strength, ultimate strength, Elastic modulus, percentage of elongation, strain hardening and strength co-efficient [1]
Cryogenic and tempering are considered the important effective heat treatments frequently used to alter the micrograph and mechanical properties of metals and alloys, especially steels; it is used in engineering materials where elongations and appreciable tensile strength are needed [2]
In tempering the material is heated below critical point of austenitic stainless steel 304 and this is followed by air cooling [4]

Summary

Introduction

Heat Treatment of engineering materials is a combination of coordinated heating along with cooling of a specific alloy or solid metal such that it produces required microstructure and desirable mechanical properties like stiffness, yield strength, ultimate strength, Elastic modulus, percentage of elongation, strain hardening and strength co-efficient [1]. Cryogenic and tempering are considered the important effective heat treatments frequently used to alter the micrograph and mechanical properties of metals and alloys, especially steels; it is used in engineering materials where elongations and appreciable tensile strength are needed [2]. Given that the LNG storage holds or infrastructure insulation device is subjected to cryogenic temperature, it is usually beneficial to use austenitic stainless steels because their cryogenic mechanical properties demonstrate superior durability, e.g. high strength, ductility and resilience. The stainless austenitic steels are rich in nickel and chromium content to improve specific mechanical properties. Most of this is used in travel, i.e. automotive.

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Conclusion