Theses and Dissertations @ UNI

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Open Access Dissertation

Abstract

This study was to determine the effects of shielded metal arc welding on delta ferrite in austenitic stainless steel weld metal. The two objectives of the study were to determine: (a) what variables of the SMAW process affect the delta ferrite content or Ferrite Number of austenitic stainless steel weld metal, and (b) to what extent the Ferrite Number is affected by SMAW variables.

The research design was experimental with data collected from mechanically produced weld metal using a magnetic instrument calibrated in Ferrite Numbers (FN). The electrode alloys tested were 308, 308L, 316L and 347. The sizes of electrodes used were 3/32, 1/8 and 5/32 inch. Variables tested were amperage, voltage, travel speed, cooling rate, travel angle, work angle, coupon size and static output characteristics of welding machines.

The data were analysed by correlation and regression analysis or by difference of means of the FN values of the control and experimental procedures. A visual evaluation of weld quality was made using criteria of a welding code. The data collected from visually acceptable welds was organized as a series of graphs. It was determined that amperage within a usable range did not cause rejectable FNs, voltage increases of a few volts did cause rejectable FNs, travel speed changes of four through nine inches per minute did not cause rejectable FNs, cooling rate changes studied did not cause rejectable FNs, travel angle changes of 40° forward to 20° reverse did not cause FN changes, work angle changes of 90° to 45° did not cause a significant change in FN, coupon size changes studied did not effect FN and the effect of different static output characteristics of a welding machine did have a significant effect on FN. All tests of significant differences were evaluated at the .05 level.

On the basis of the findings from the data collected from the samples welded, it was concluded that:

  1. Any increase in slag blanket depth over the molten metal caused some increase in FN.
  2. Welding machines with different static output characteristics may have different arc striking abilities and provide other benefits.
  3. Variables effecting only slight changes in FN may be accumulative and be a factor in an overall control program.
  4. The factor for calculating nitrogen content of weld metal was found for this group of welds to more nearly be 0.08 than the recommended 0.06 normally used.

Year of Submission

1980

Department

Department of Industrial Technology

First Advisor

Alvin Rudisill

Date Original

1980

Object Description

1 PDF file (x, 197 pages)

Language

EN

File Format

application/pdf

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