Effects of Electrode Types on the Microstructure, Tensile and Hardness Properties of 304 L Austenitic Stainless Steel Heat-Affected Zone (HAZ)

Bolarinwa Johnson Kutelu,Saliu Ojo Seidu,Emmanuel Gbolade Adubi

doi:10.4236/jmmce.2018.65038

Bolarinwa Johnson Kutelu, Saliu Ojo Seidu + Show 1 more

Open Access

https://doi.org/10.4236/jmmce.2018.65038

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Abstract

Submerged arc welding (SAW) has been well utilised for the production of weld joints in 304 L ASS for various industrial application. However, effective performance of the material in service has been hampered by improper choice of electrode. Therefore, in this study, effects of different types of electrode on the microstructure and tensile property of type 304 L austenitic stainless steel heat-affected zone (HAZ) were studied. Chemical composition of the as-received sample was determined. A number of samples were cut from the as-received sample. Afterwards, two half were joined together with 308 L, 312 L and 316 electrodes at a controlled welding speed, current and voltage of 4.6 mm/s, 160 A and 30 V to produce a constant heat input of 626.09 J/mm. An automatic SAW machine with Model Type: DX3-301, and Frequency: 50 Hz was used. And based on ASTM standard, tensile and hardness samples were prepared from the as-received and HAZs. Tensile and hardness measurements were made. Also, specimens for microscopy studies were prepared from the HAZ and as-received samples. From the results, microstructures of the HAZs revealed varied volume fraction of austenite and ferrite phases and grain sizes, and at austenite and ferrite grain boundaries, chromium carbide formation and precipitation were observed. The weld joint produced with 308 L electrode revealed optimum UTS value and YS value of 475 and 325 respectively. While weld joint produced with 316 L electrode has superior ductility of value 41%. Irrespective of the types of electrode used, the as-received sample revealed superior tensile properties over the weld joints. Also, optimum hardness value of 45.7 HRA was obtained with 308 L. Hardness value of the as-received sample was higher than that of HAZ samples.

Highlights

The Type 304 L Austenitic Stainless Steel (ASS) has featured prominently in different areas of engineering applications, including metallurgical, mechanical, chemical, automobile and nuclear industries
The weld joint is comprised of base metal (BM), heat-affected zone (HAZ) and fusion zone (FZ), and in service, performance of the weld joint is determined by the microstructural characteristics of these zones
Due to differently feature microstructures in the HAZ, resulting from thermal cycles, which correspond to different mechanical properties, the HAZ becomes more critical than BM and FZ

Summary

Introduction

The Type 304 L Austenitic Stainless Steel (ASS) has featured prominently in different areas of engineering applications, including metallurgical, mechanical, chemical, automobile and nuclear industries. The weld joint is comprised of base metal (BM), heat-affected zone (HAZ) and fusion zone (FZ), and in service, performance of the weld joint is determined by the microstructural characteristics of these zones. In SAW, weld joints are produced by chemical and physical reaction of the weld electrode, the base metal and the flux and the alloying elements coming from them [9]. In this study, 312 L ASS, 308 L ASS and 316 L ASS electrodes were used to produce 304 L butt joint SAW welded samples, with particular emphasis on HAZ; this is with a view to determining the best match for optimum service performance

Method

Gas Tungsten Arc Welding Process An automatic SAW machine with Model Type

Results and Discussion

Conclusions