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GMAW ultra low spatterwelding technology

Guangxian Zhang 1,2, Hanbi Zhang 2, Peng Li 2

(1.Shandong University, Ji'nan 250101, China; 2. Shandong AOTAI

Electric Co., Ltd., Ji'nan 250101, China)

Abstract: "GMAW Ultra Low Spatter Welding Technology"

is a new type gas shielded metal arc control technology.

This technology realizes wider range of low spatter welding

by unique high precise arc control, which greatly improves

arc stability and bead formation uniformity. Furthermore, it

greatly improves bead appearance and welding efficiency in

thin plate welding application.

Key words: GMAW; ultra low spatter; welding

DOI: 10.7512/ j.issn.1001-2303.2017.13.21

Dr. Guangxian Zhang, research staff in Electrical and Electronic engineering department from Shan-dong university, advisor for Ph.D. students, pro-fessor. He is the CEO of AOTAI electric Co., Ltd.,which is the leading man-ufacturer of Inverter weld-ing and cutting equipments in China.

His main research aspects include power electronic technology, CNC technology, special power and promoting the industrialization of scientific and technological achievements. He studied the inverter technology and the welding power source, solved the problem of the short life of inverter welding power source, low power factor, and the big splash of carbon dioxide gas shielded welding.

0 Introduction In modern industry, carbon steel, stainless steel and alloy steel are

more and more widely applied. Structural parts and galvanized sheet

are commonly used in vehicle manufacturing, fitness equipment, office

furniture industries. These material is very sensitive to heat input, as a

result lower heat input is preferable under the case that welding quality

and bead formation is guaranteed. Besides, slag removal work in

traditional GMAW application is a drawback.

Traditional MAG welding can weld material stably, but minor

spatters, low welding speed and high heat input (it burns workpiece)

confine its application [1]. Even though pulse MIG can limit spatter effici-

ently, but higher heat input is not suitable in thin plate, co-deposit sheet

and large gap applications. What's more, pulse MIG can't work in CO2 [2].

In recent years, those technologies which adopt wave control to

limit spatter are widely used. They can reduce spatter in low welding

parameters, but narrow parameter range and poor adaptability exit [3].

When welding current is high, or stick-out length changes severely,

stable welding would be disturbed and spatter explodes [4].

This paper aims at widening welding current in low spatter appli-

cation and improving low spatter welding stability and adaptability by

analyzing GMAW drop transfer features.

1 "GMAW Ultra Low Spatter Welding Technology" principle and realization

AOTAI MAG--350L precisely controls welding arc and molten pool

by full digital control system, which can widen low spatter welding

application and uniformize drop size efficiently.

"GMAW Ultra Low Spatter Welding Technology" controls short-

circuiting and re-arcing separately (as Fig.1). When short circuiting

occurs, keep output current low to ensure wire and molten pool

sufficiently contact, then increase current to accelerate drop transfer;

when necking is forming, confine output current cdramatically to avoid

spatter; after successful re-arcing, increase current to form drop again.

In this way, uniformized arc length and drop size can be guaranteed.

When welding parameters are increased, drop transfer method

changes from typical short-circuit transfer to mixed transfer of various

sizes of drops. Numerous spatters explode during light short-circuiting.

Thereafter, welding machine should stop inverting to ensure sufficient

contact between wire and molten pool when short-circuit is detected (as

Fig.1 T1~T2).

Fig.1　"GMAW Ultra Low Spatter Welding Technology" control sketch

Dr. Guangxian Zhang Email: zgx@sdu.edu.cn

· ·189

Traditional arc detection method is to compare feedback voltage

with threshold value. That feedback voltage is higher than threshold is

considered as re-arcing, while is short-circuiting on the contrary (as Fig.1

T4~T5). Exterior fact changes like stick-out length would affect judgment

correctness from machine side, which results in unstable welding.

In order to avoid such interference, detection method should be

upgraded to arc/drop detection from voltage detection. During welding

process, by analyzing feedback current and voltage, cable voltage

drop, stick-out resistor etc parameters to extract arc shape, drop size,

drop necking etc state, the whole system adopts closed loop of these

information to control output wave under different conditions.

With the above optimization, ultra low spatter welding current

range can be increased by 15%~20%. To weld Φ1.0 carbon steel

under MAG process, spatter dramatically increases in traditional control

technology. While new technology limits spatter perfectly even up to

190 A, total efficiency is improved by nearly 20%.

In order to realize such control technology, the whole control system

control period and response speed are greatly increased. As experiment

result demonstrates, droplet dynamic period is around 10-5 s. Thanks

to new generation ultra high speed dual CPU, AOTAI welding machine

control cycle is increased to 10-6 s and realizes 100% necking detection

by advanced algorithms (as Fig.1 T3~T4). Main circuit adopts high

frequency IGBT inverting diagram, with AOTAI patented soft switch, to

realize fast response.

"GMAW Ultra Low Spatter Welding Technology" is realized by

internal electrical control system in welding machine, therefore

traditional GMAW wire feeding device and torch can be directly used to

work with it.

Over traditional welding machine, MAG--350L with "GMAW Ultra

Low Spatter Welding Technology" enjoys the following advantages:

soft switch technology, higher reliability, more energy-saving; multiple

CPU high speed control system, higher precise drop transfer control,

minimize welding spatter; higher welding speed and efficiency; versatile

communication port to work with automation machine and arc robot.

Fig. 2　"GMAW Ultra Low Spatter Welding Technology" real

voltage and current curve

2 AOTAI MAG--350L applicationMAG--350L widens the application range of low spatter welding,

improves welding efficiency under ultra low spatter condition. It can be

widely used in carbon steel,

stainless steel and co-deposit

sheet welding application.

A barrier fence project in

a city's subway system adopts

304 stainless steel tube

with satin finish treatment.

In order to avoid film treat-

ment being damaged, it's

required no spatter and low

heat input. Now they're

using MAG--350L and get

wider welding parameters

and higher efficiency with

15%. (Welding parameters:

1.0 mm 308 stainless steel

wire, 97.5%Ar+2.5%CO2,

Current: 190 A)

Nowadays, vehicles adopt

galvanized or aluminized

sheet for vehicles' housing

and box body in order to avoid rusting. It's not allowed to damage the

coating when treating these material. A huge vehicle manufacturer in

northern China employs MAG--350L to welding aluminized sheet and

no slag removal and no repair is required after welding.

3 ConlusionAOTAI MAG--350L ultra low spatter inverter welding machine

realizes wider range of low spatter welding by unique high precise

arc control, which greatly improves arc stability and bead formation

uniformity. In carbon steel, stainless steel and co-deposit steel welding

application, MAG--350L enjoys much higher efficiency over traditional

welding machine.

MAG--350L is also capable to work with automation machine and

arc robot system, besides traditional manual semi-automated welding

application.

Reference:[1]　Huang Yong. Analysis and Control of Short-circuit Transfer During

CO2 Welding. 1998,24(3):76-80．

[2]　Zhang Guangxian. Control Principle of Inverter Welding Machine.

China Machine Press, 2008.

[3]　EK Stava. The surface tension transfer power source: A new low sp-

atter arcwelding machine[J].Welding Journal,1993,12(1): 25-29.

[4]　Yin Shuyan. Digitalization of Electric Welding Machine. Beijing

Industrial University, 2008.

Fig.3　AOTAI MAG--350L stainless

steel welding photos

Fig.4　AOTAI MAG--350L aluminized steel

brazing picture