Journal of Signal and Information Processing, 2011, 2, 159-164

doi:10.4236/jsip.2011.23020 Published Online August 2011 (http://www.SciRP.org/journal/jsip)

Copyright © 2011 SciRes. JSIP

159

Study on Evaluation Method of Aluminum Alloy

Pulse MIG Welding Stability Based on Arc Voltage

Probability Density

Jing Nie1, Xiao-Feng Meng 1, Yu Shi2

1School of Instrumentation Science & Optoelectronics Engineering, Beihang University, Beijing, China; 2Key Laboratory of Non-

Ferrous Metal Alloys and Processing of Ministry of Education, Lanzhou University of Technology, Lanzhou, China.

Email: niky711@163.com

Received February 24th, 2011; revised April 16th, 2011; accepted April 25th, 2011.

ABSTRACT

Bring forward a new analytica l method in order to evaluate the stability of the process of a luminum alloy pulsed MIG

welding. The ratio of the first and the second peak in arc voltage signal probability density was selected to evaluate

aluminum alloy pulse MIG welding stability. By calculating the arc voltage signal probability density from 80 sets of

welding experiments, the ratio of the two peaks in arc voltage probability in every set was captured. And the evaluation

system of aluminum alloy pulse MIG welding stability was established. The smaller the ratio of peaks in arc voltage

signal probability density is, the better the stability of the welding will be; the bigger the ratio of peaks in arc voltage

signal probability density is, the poorer the stability of the welding will be.

Keywords: Aluminum Alloy, Pulse MIG, Welding Stability, Probability-Density, Arc Voltage

1. Introduction

The process of aluminum alloy pulse MIG welding is

characterized by its non-linearity, strong time-varying,

strong coupling between the parameters, and so forth [1].

The reason why its process is unstable has not been well

explained until now. Becaus e of the lack of the parameter

matched stability evalu ation indicators, the control of the

aluminum alloy pulse MIG welding by changing the

welding parameters is very difficult. The fail of matching

the parameter will probably lead to the instability in the

welding process or even worse. In recent years, many

scholars at home and abroad have studied the stability in

the welding process: reference [2] put forward an on-line

evaluation model of the process stability by use of the

statistical analysis and partial least-squares regression.

Reference [3] an d [4] found that the approximate entropy

of the arc signal varied with the change of the parameter.

Reference [5] and [6] analyzed the prob ability density of

the corresponding welding current and voltage and fi-

nally evaluated the welding stability.

This paper analyzed the probability density distribu-

tion of the 80 sets of voltage signal under different weld-

ing speed, wire-feeder speed and duty cycle matched pa-

rameters.

2. Experimental System

The experiment applied DELEX VIRIO MIG-400L

welding machine to pure Ar gas shield bead-on-plate

welding. The designation of the welding wire was 5356,

diameter 1.2 mm. The material of the workpiece was

aluminum50581-H321 with the thick of 6mm. The torch

was fixed during welding. And its distance between the

workpiece was unchanging. The workpiece moved on the

worktable. The initial wire extension was 15 mm. Data

acquisition card PCL812PG was applied to the welding

and its frequency was 1 kHz. The current sensor was

CSM400FA/100 mA. The time between the arc igniting

and ending was not less than 45 s. Video acquisition

captured the condition of the arc and molten pool to

judge the stability of the welding. Figure 1 was the ex-

perimental system.

Because of the finding that the duty cycle of the pulse

current, the wire-feeder speed and welding speed impact

the welding stability greatly, the experiment combined

the duty cycle, the wire-feeder speed and the welding

speed to weld. Th e base valu e o f the weld ing curren t was

25 A, the peak value 180 A, pulse frequency 40 Hz,

welding voltage 18 V, and shielding airflow 18 L/min.

Because the aluminum alloy pulse MIG welding was