INFLUENCE OF TIG PROCESS PARAMETERS ON HARDNESS, TENSILE STRENGTH AND MICROSTRUCTURES OF AISI430 FERRITIC STAINLESS STEEL WELDS
INFLUENCE OF TIG PROCESS PARAMETERS ON HARDNESS, TENSILE STRENGTH AND MICROSTRUCTURES OF AISI430 FERRITIC STAINLESS STEEL WELDS
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Date
2021-03
Authors
MUSA, Abdulrahman Adeiza
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Abstract
The influence of tungsten inert gas (TIG) welding process parameters on the microstructural
features and mechanical properties (hardness and tensile strength) of AISI430 ferritic stainless
steel (FSS) weldsbased on the central composite design (CCD) approach, was investigated.
The process parameters considered in this study include; the welding current (I), welding
speed (S) and argon flow rate (AFR). The stainless steel AISI 430 FSS plates having
chromium content of 17% Cr and 1.5mm thickness were butt-welded using autogenous
tungsten inert gas welding process. The microstructures of the FSS welds were analyzed using
optical microscope.The hardness and tensile strength were determined using Vickers’s
microhardness testing machine and Hounsfield tensile testing machine respectively. The
results showed that all input variables considered have direct influence on the properties as
well as the microstructure of the weldments. Microstructural result reveals ferrite structures
aligned in the cold rolling direction for the base metal. The microstructure of the weld metal
at the optimized conditionshows the presence of equiaxed ferrite grains with some grain
boundary martensitestructureswithin the fusion and heat affected zones of theweldment. It
was observed that welding current shows the greatest effect on the tensile strengthwith34%
contribution, followed by the speed and argon flow rate with 15% and 2.54% respectively.
For the hardness, the speed plays the major role. Empirical models were generated from the
analysis to predict the weld quality. An optimized tensile strength and hardness of
431.014MPa and 307.10 HV respectively, were predicted at the welding current of 22A, the
welding speed of 5mm/s and the argon flow rate of 10L/min. In order to validate the results,
confirmatory experiments were performed based at the optimized condition and the test
results were found to be in good agreement with the predicted values with percentage errors
of 1.23% and 1.81% for the tensile strength and hardness respectively. Based on this finding,
it can be concluded that the optimization of TIG input parameters usingresponse surface methodologyapproach produced weld joint with good tensile strength and improved hardness
that is very close to that of the base metal.
Description
A THESIS SUBMITTED TO THE SCHOOL OF POSTGRADUATE STUDIES
AHMADU BELLO UNIVERSITY, ZARIA NIGERIA,
IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE AWARD OF
MASTER OF SCIENCE IN METALLURGICAL AND MATERIALS ENGINEERING
DEPARTMENT OF METALLURGICAL AND MATERIALS ENGINEERING,
FACULTY OF ENGINEERING,
AHMADU BELLO UNIVERSITY,
ZARIA - NIGERIA
Keywords
INFLUENCE,, TIG PROCESS PARAMETERS,, HARDNESS,, TENSILE STRENGTH,, MICROSTRUCTURES,, AISI430 FERRITIC STAINLESS STEEL WELDS.