I work for NAVY in QA at NGSS INGALLS SHIPYARD.We use mil-std-
1689 requirements for cleaning of the surface prior to welding.I dont
have it in front of me now but i believe it states free of mill scale,
dirt,etc. that would affect welding operation.What do the commercial
stds say. Do they say a clean surface bright and shiny,etc. or is it
open to interpretation.
I know of one instance where a long butt weld on a flat surface had
been cleaned but left over nite.I could see mill scale the next morning
and i contacted the weld supervisor and requested that it be cleaned
again.They gave me a hard time but they did re-clean it.
Also what they do here is to use a buck eye to clean the weld surfaces
on high tensile steel that is only 3/16 inch thick[buck eye grinder].I dont
agree with this practice and i think a power tool wire brush should be
DKUMPUNEN SUP SHIP GULF COAST US NAVY
we have a similar issue to yours.
D1.1 2004 5.15 reads "Surfaces on which weld metal is to be deposited shall be smooth, uniform, and free from fins, tears, cracks and other discontinuities which would adversly affect the quality or strength of the weld. Surfaces to be welded, and surfaces adjacent to a weld, shall be FREE from loose or thick scale, slag, rust, moisture, grease and other foreign material that would prevent proper welding or produce objectionable fumes. Mill scale that can withstand vigorous wire brushing, a thin rust - inhibitive coating or anti spatter compound may remain with the following eception: for girders in cyclicly loaded structures.
We have a number of production people who do not understand, that when the code uses the words ...FREE from..... scale slag RUST, that it means there will be none, zero , NO RUST in the weld zone period.
Everyone knows heavy rusted connections need to be addressed, but the problems come to play with lighter rust ---- does EVERY joint really need to be a nice clean and shiny joint prior to welding? Personally I say no - but where to find the compromise point seems to be very difficult.
We then try to " define " what is REAL rust. If you can wipe it away with your hand is it "rust" to be concerned of??? At what point does it become enough to be concerned with?? So many opinions with nothing that I can find to hold on to - other than ..... FREE FROM RUST.
Hello DKUMPUNEN, I can understand your concern for the clean condition of welded materials in this case. I spent a number of years working for a fab shop in the Portland,Ore. area doing a considerable amount of work on Navy contracts and Corp of Engineer contracts. Almost everything that we welded in these instances was welded with GMAW Spray Transfer mode on materials that had been sand-blasted and then coated with zinc-chromate primer. Prior to welding anything, we then had to remove the primer from within approx. 2" of any welded area. If you have had much experience with this type of primer you know that it has the capability of actually penetrating the surface of the material to a depth of .010 to .020" so the grinding had to be very thorough. After the welding was completed there was a visual inspection and then the welds were either UT'd or x-rayed. The point of my rambling is this, if there is a thorough finished inspection of the welds and they pass that inspection doesn't that verify that the cleaning was sufficient? I don't know of any welder that wouldn't kill to weld on materials that had been cleaned as you are describing in the thread of this post, most aren't afforded that luxury. Weld pool contamination from scale, rust, and other foreign materials can certainly be detrimental to making a sound weld, the degree of cleaning required to insure success will still be measured by being able to pass final inspection. In many ways correct filler materials, proper welding parameters, preheat, interpass,and post-heat temperatures may be of even greater importance in the finished weld. You will certainly need to establish your interpretation of how clean is clean, just remember to use the final weld inspection and passage to gauge this. My $.02 Respectfully and regards, aevald
First, I'm not familiar with the term "buck eye grinder" What is that?
One state DOT I know of requires all steel to be preblasted prior to any fabricaton on "tension members", including cutting or burning. Of course that means blasting again after fabrication if paint is required.
Another DOT wants the weld zone cleaned to bright metal on primary members but that is optional on secondary members.
Still others simply rely on AWS D1.1 or D1.5, which was pretty well quoted in the previous post, as long as there are no weld quality issues.
Those AWS codes do allow tight mill scale, anti-rust coatings, or anti-spatter compounds, but not if it will adversely affect the welds.
I think most DOT specifications or comercial contract specifications are written to address issues the customers have encountered over time, which may not be specifically addressed by the AWS codes.
Generally, the commercial world seems reluctant to regulate non-critical applications. It seems like - A) if you get burned once, watch out for the next time. B) Burned twice? Time to put it in the contract. C) Third time? Get the welding codes to address it. (Figuratively speaking, of course.)
Overall there is some business logic to that. If you have confidence that a product will perform as designed, why spend money to regulate a non-problem? But when the risk is high in the event of a product failure, then the cost of controls is viewed as insurance.
Get an AWS code book; they are pretty inexpensive and full of knowledge. If you need a Weld/Materials Joining professional, post on AWS website.