An e-mail
question addressed to this site.
Ed, the tier one automotive parts company I
work for, has been told by the corporate Chrysler engineer that they have to use
"self shielding flux cored wires" when welding galvaneald, parts. These
flux cored wires cause us numerous weld issues. Our weld rework rates as high
as sixty percent. The workers frequently complain about the weld fumes and the
paint shop is appalled at having to paint over weld slag. What is the logical,
justification for using these wires?
Ed's Answer: I feel
your pain and this Chrysler nonsense has been going on too long. Let me tell you
one story about this same engineer and how his ridiculous weld recommendations
have so far cost Chrysler and their suppliers at least fifty million dollars.
The
million dollar per-month weld fiasco that occurred at one of Chrysler's stamping
facilities in Ohio during the nineteen nineties.
The following is a description of
an automated weld disaster, it's an indication of the costly damage that can result
from weld process ignorance and management manufacturing isolation.
The
Chrysler robot welds were made on galvanealed, cross-member parts, 2 to 2.5 mm
thick. The cross member welds had to be made with the weld consumables selected
by the Chrysler corporate engineer responsible for weld specifications.
The
weld wires selected were large self shielded flux cored wires that required a
high, weld current range of 320 / 350 amps. This weld current had more in common
with welding a 6 mm fillet weld than a 2 mm gage weld. The current was the optimum
(stable) current required for the large electrodes.
The weld current
used on the thin parts was far too high for the thin gage cross-member parts.
HOW
MANY ENGINEERS OR DESIGNERS HAVE AN APPRECIATION FOR A WELD CONSUMABLE WELD CURRENT
COMPATIBILITY WITH THE STEEL THICKNESS OF THEIR APPLICATIONS ?
HOW MANY
ENGINEERS ARE AWARE OF THE OPTIMUM CURRENT RANGE OF THE COMMON AVAILABLE MIG AND
FCAW CONSUMABLES?
THESE SUBJECTS WHICH ARE NECESSARY
FOR ROBOT WELD PROCESS CONTROL ARE COVERED EXTENSIVELY IN ALL MY PROCESS BOOKS.
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The excess yet minimum weld current required
by the self shielded flux cored wires created so many weld holes in the cross-member
parts that up to 10-13 manual welders were required each shift at the Chrysler
plant for the robot weld repairs.
The welds had so many weld holes that
the manual welders re-welded the total robot weld length, which was over 2 meters
in length, The result was weld slag on top of weld slag. Its ironic that the finished
welds would not have been accepted in any facility that applies logical weld quality
criteria to the welds it produces. The
Chrysler plant manger informed me that the total weld rework costs for his plant
was costing a million dollars per month.
As the weld fumes were dangerous from the cacogenic self shielded wires,
the manual welders had to wear breathing apparatus and have a break every few
hours.
This weld fiasco went on for more than a year. The Chrysler corporate engineer's
justification for the use of these unsuitable weld wires was that they were necessary
for welding galvanealed to reduce micro crack potential from the zinc alloy reactions.
It's notable that if these products could achieve what the corporate engineer
stated they could do, the electrode wire manufacturer would be the first to brag
about this benefit in the wire promotional literature, of course the weld consumable
manufacture is not that stupid.
The frustrated plant manager had little
respect for the weld advice from his corporate engineer. The plant manager asked
that I rectify the welding problem..
I knew it was a hopeless task to
convince this inexperienced corporate engineer to take responsibility for his
multi-million dollar fiasco. I suppose also he did not want his organization to
know where to lay the blame for the millions of dollars lost. I proposed to the
Chrysler engineering team and managers responsible for the cross members, that
I simply weld the parts with a robot and the MIG process, then provide micro /
macro and mechanical test results of the resulting welds.
I
robot welded the parts using an E70S-3, 0.035 (1 mm) MIG consumable. I eliminated
the the weld burn through issues. I then qualified the MIG welds through an unbiased
major Detroit testing agency. The weld test report indicated that the MIG welds
provided superior weld results and passed all the mechanical / micro weld tests
with flying colors. I presented the results to the Chrysler corporate engineers
and their peers.
The solution I presented would immediately save Chrysler
a million dollars a month. All the weld data presented at the meeting indicated
that the primary issue was with the weld process and consumables selected, there
was also some gap issues. The data was well received by the plant manager. However
after the Chrysler engineers reviewed the report I was shocked when informed that
the engineer responsible for the weld specification would not admit the weld consumables
were the issue. This engineer would not approve a weld process change.
The Chrysler corporate management who managed the engineers responsible for the
parts received the report. These managers understood little about the weld process
recommended, they could however read. I believe they simply did not have the balls
to take action. The engineer responsible did with reservation allow the use of
a smaller self shielded weld wire.
Shortly after the meeting, the less than two year old, multi-million robot weld
line was shut down and the robots, the application and the Ohio robot jobs were
swept under the carpet and moved south to Mexico.
I
firmly believe the engineer responsible for this weld disaster was advised to
use the self shielded flux cored wires by the company that makes this obnoxious
weld consumable product. However the engineer is paid to engineer.
Many
weld consumable manufacturers will recommend a weld consumable that their competitors
do not sell. Typically this may not be the best consumable
for the application, yet this common welding sales tactic, ensures no one else
can bid on on the consumable business.
DURING THE LAST TWO DECADES, IN NORTH AMERICA THE EASIEST PLACE TO SELL THE WORST
WELDING CONSUMABLES WAS AN AUTOMOTIVE OR TRUCK PLANT.
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As
indicated by the weld mechanical tests, there is no justification for the use
of self shielded flux cored products on galvanealed cars or truck parts. The MIG
process allows the use of the unique, low energy short circuit process, in which
the arc goes on off many times per-second. I believe the selection of the "open
arc", higher weld energy, poorly suited self shielded weld wires was based
simply on " weld process ignorance" that was fed by " weld consumable
salesmanship"
It's unfortunate that as you read this today that the Chrysler
corporate weld engineer is still informing part suppliers in North America and
Mexico that they must use the self shielded flux cored consumables.
Weld Reality. From a weld mechanical, weld chemistry, weld quality and weld productivity
perspective, in contrast to MIG wires, the self shielded flux cored wires offer
no weld benefits, they do however offer excess weld spatter, tenacious weld slag
and weld fumes that would be considered a dangerous weapon in Iraq.
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WELD FACTS:
[a]
WELD HEAT: In contrast
to MIG short circuit transfer, on thin gage applications the self shielded, straight
polarity, "open arc" weld transfer mode from the flux cored wires can
dramatically increase the weld burn-through potential of thin gage butt weld applications.
Even when smaller wires are used. Its a simple weld fact that today the smallest
self shielded flux cored wire, 0.035 (1mm) cannot weld butt weld on steels <1.6
mm wit out weld burn through.
[b] WELD FUMES: In contrast
to MIG the weld fumes produced from the self shielded wires are much more hazardous
and actually contain cacogenic components that few people want to discuss. I know
recently when I welded with these products for two hours I felt sick and bilious
that evening.
When using the self shielded weld wires, weld shops have
to invest in costly, large ventilation equipment that would not be required with
MIG wires. Of special concern is the secondary smoke that gets out of the robot
cells. Also consideration must be given for the long term health of the manual
welders that have will have to use these wires to carry out the weld repairs which
will be necessary on most gage galvanealed welded parts.
[c]
WELD SPATTER: With MIG welding the weld spatter is controllable. With the
self shielded products additional man power is typically required for weld spatter
clean up. Also the weld cell equipment and weld part fixtures will typically be
heavily contaminated with the unnecessary, excessive weld spatter.
[d] WELD SLAG &
PAINT: MIG produces a minuscule
amount of thin slag. In contrast, the self shielded flux cored wire weld slag
will be tenacious, excessive and almost impossible to remove, an E coat or paint
point that the Chrysler engineers seems to give minimal consideration.
[e] WELD REPAIRS: Although its a common practice
in automotive / truck plants, placing a self shielded wire repair weld on top
of a weld with slag is an invitation to a future weld product liability. When
repairing the self shielded welds with the weld slag in place, both the weld fusion
and weld quality potential will suffer greatly. For a company that has a weld
specification that specifies a concern for weld porosity limitations, it's ludicrous
for the same organization to allow self shielded repair welds over welds with
slag. The repair welds will have poor fusion and be saturated with slag and porosity.
[f] WELD MECHANICALS: The fact that the
part is galvanealed or galvanized is irrelevant.
I have had mechanical weld
tests performed on these wires and also on MIG wires, the test results indicate
that MIG provides the best internal and external weld quality and meets all the
mechanical needs.
[g]
WELD COSTS. It amazes
me that in an industry that looks for so many ways to shave a $1 of the cost of
a vehicle that some one would recommend the self shielded wires.
The
price of the self shielded wires can be two to three times per-pound the cost
of a MIG wire. The weld deposition efficiency of the self shielded wires also
dramatically increases the weld consumable costs. With a MIG weld set correctly,
the weld deposition efficiency should be at least 99%. As the self shielded wire
weld may be half weld and half slag and spatter,
I would anticipate that
for every pound of self shielded wire purchased, only about 50 percent ends up
as weld.
Example.
Lets say a foot long MIG weld requires 0.1 lbs. The MIG wire cost $1 a pound so
the MIG weld wire cost per foot of weld is 0.10 cents. In this proportion the
weld gas for the 0.1. lbs would be approx. 0.10 cents so the MIG consumables cost
for the foot of weld would be 0.20 cents.
The self shielded wire cost
$3 lb. Due to poor weld deposition efficiency it takes 0.15 lbs of wire for the
foot of weld. The self shielded wire will cost 0.045 cents per foot of weld.
20 cents for the MIG / gas versus 45 cents for the self shielded now multiply
that by 50 feet of welds on millions of vehicles.
MIG
wire is more stable than the self shielded wires and offers the unique arc on
- arc off short circuit transfer mode. On many thin gage applications <1.6
mm, in contrast to self shielded the MIG process will allow for higher wire feed
(higher weld deposition rates). Typically MIG will allow for a twenty to forty
percent increase in weld deposition. This means when using MIG in contrast to
self shielded wires, there may be a potential of 15 to 30 percent reduction in
weld labor costs or a 15 to 30% increase in robot weld speeds.
035
self shielded data for 16 - 18 gage butt welds, wire feed 140 ipm, 80 amps, 14
- 17 volts robot weld travel 12 to 14 ipm. On butt
welds and on metals less <1.6mm, beware weld burn through.
035 MIG
on 16 gage. Short Circuit, wire wire feed 250 ipm, 17 volts, robot
weld travel 20 to 25 ipm.
A
great impact on weld costs is robot weld efficiency and weld rework costs. Thanks
to Chrysler, robots are today using the worlds most inefficient weld process and
generating weld rework that's typically greater than 60 percent.
As
the gage thickness has decreased as with galvanealed hydro formed products as
thin as 1mm, the self shielded flux cored process even with 0.045 and 0.035 (1.2
- 1 mm) wires is now being recommended by Chrysler. These wires are simply not
suited. The MIG process should be used on all galvanealed parts, especially on
parts <1.6mm. It would be beneficial if management at Chrysler recognized the
health and cost consequences of this ridiculous situation.
Managers
should consider providing designers and engineers with weld process control training.
Provide a training program that places focus on design compatibility with the
weld process utilized.
E
Mail.Dear Ed.
July
05.
It
looks like we are just starting out on a new Chrysler project welding a galvannealed
product, Galvanneal NS 6000 D series 44a. According to the Chrysler spec, we would
be
allowed to use a solid carbon steel ER 70S-3 MIG wire, but they require
a 75 argon - 25 CO2 gas mixture for this. I think
Chrysler takes the cake on this gas selection. By the way if our engineers had
selected galvanized material, according to the Chrysler spec we would have been
forced into using the terrible self shielded FCAW process.....Is
the Chrysler weld engineer from this planet? What I also don't understand is the
fact that they are specifying a coated material, and then we are still required
to e-coat the part. I wonder what the reasoning is behind double coating the cradles.....I'm
sure they don't even know.
Regards GR. Tier One.
Ed's
Answer" there is no rationalization for any of the welding logic that comes
from Corporate Chrysler. Their chief welding engineer has for more than a decade
been in the wrong profession. The choice of the 75-25 gas restricts the use of
spray transfer on parts over 0.070 and when used will be the cause of spatter.
As for the self shielded wire, no one knows why the Chrysler corporate engineer
still insists on the world's worst electrode for coated materials. As for the
double coating, it makes no sense. What does make sense is to coat the parts after
welding as the weld destroys the coating in the weld area. As I said don't look
for logic when dealing with Chrysler..
E-Mail From
PL England.
Ed.
I have just read your Chrysler Neon article regarding the crossmemebers and
self shielded flx cored wire issues. I fully endorse your views and comments.
It is a shame that many "welding engineers" in the automotive industry
lack the actual knowledge and skills to fulfill this critical role. I myself
am a welding engineer for a tier one supplier to the auto industry and see
this too often. As a time served boilermaker in the UK, I feel that there
is a hugh lack of process knowledge and experience with the welding and engineering
personel in the auto industry. I must also thank you for your books 'A Management
& Engineering Guide to MIG & the Training' materials both of which
we as a company refer to regularly.
cheers
PL - England
Take the 
