[ckrantz]

Are there any strength difference between the galvanized pipe I can get from the hardware store compaired to DOM steel tubing? I'm not sure if I could use the pipe in place of DOM and still retain the strength?

[fyffe555]

DOM (drawn over mandrel - if thats what we're talking about) steel will be somewhat stronger than galvanized pipe if the two are of the same dimensions. Gal. Pipe usually has a bigger cross section than DOM of the same size so there's more material in the pipe and so the pipe can be stronger. All depends on the dimensions of the part, then the material..

[keebler303]

1 for the same dimensions of the material dom will be stronger.
2 thats not to say that pipe couldn't be used in place of dom but there may be some changes to the design necessary to retain the same strength.
3 generally speaking pipe from the hardware store will be of lower quality than pipe from a steel supplier or plumbing wholesaler.
4 dom (or hrew) are "structural tubing" engineered for load bearing structures, pipe, is pipe.
5 if its simply a matter of cost then you could use pipe, hrew, or dom.
6 if you are making a swingset for your ex-girlfriends neighbors nephew, then i would use pipe. if you are building a roll cage or the like, i would use hrew/dom.
7 it all comes down to what the desired use is.
8 IMPORTANT: if you are doing any welding, do not use galvanized pipe! black pipe will work as a substitute. when you weld/grind/etc. you invite a lot of heavy metal fumes into your body. this will kill you and takes less than you may think.

[ckrantz]

The galvenized part is the coating that is sprayed over the material correct? If this coating is wire wheeled off is it okay to weld on?

[NC Cams]

Galvanizing is generally a hot dipped (dip in hot molten zinc) process.

WIre brush is NOT adequate for a "certified weld". You have to sand it all off to get to parent metal as the zinc is a weld contaminant and quite poisonous.

Better yet, WHAT ARE YOU TRYING TO BUILD???. With this knowledge, we can tell you what to use PROPERLY. A swing set is one thing, a swing set that will be used to lift heavy objects (motors and trannys) is another, a roll cage is yet another thing entirely....

Regarding sanding/grinding off the zinc, REREAD POST #3, item 8. Might want to plan to say a last goodbye to your wife and kids should you choose to ignore this important caveat.

[Geof]

Are there any strength difference between the galvanized pipe I can get from the hardware store compaired to DOM steel tubing? I'm not sure if I could use the pipe in place of DOM and still retain the strength?

There is a difference in strength between ordinary galavanized pipe and DOM tube; for the same OD and wall thickness DOM will be considerably stronger but if you are planning on using the material for the tracks on a router or something like that this is completely unimportant.

The important property for a router application is stiffness not strength and there is a very important distinction between these two properties of material. Strength is a measure of how much force needs to be applied to something before plastic deformation occurs; i.e. it is permanently bent and does not return to the original condition. Stiffness is how much elastic deformation occurs under a given load and when the deformation is elastic the material or structure returns exactly back to the original condition when the load is removed.

With any material under load elastic deformation occurs first followed by plastic deformation when what is called the yield strength is reached. With DOM tube a great deal more load can be applied and a great deal more elastic deformation will occur before the yield strength is reached than with galavanized pipe.

Obviously with any machine tool whether it is commercially made or a DIY effort it is essential that the loading is always within the elastic deformation region and under loads that only cause a small amount of elastic deformation there is no noticeable difference between galvanized pipe and DOM tube so either can be used for structural parts of a machine.

If the pipe or tube is being used as the tracks it could be that DOM tube is a better choice because it is much smoother than pipe and will handle the concentrated load of small bearings rolling on it with less localized distortion. However, if the pipe or tube is going to be welded in place then pipe may be a better choice because it has less internal stress; DOM tube has a lot of stress and work hardening from the manufacturing operations and the heat of welding will release the stresses unevenly and lead to much more distortion.

Also if welding is to be used black pipe rather than galvanized is preferable because it is easier to weld. Galvanizing can be ground off and it will burn off during electric welding creating a large amount of smoke. This is unpleasant but not particularly toxic.

[keebler303]

Galvanizing can be ground off and it will burn off during electric welding creating a large amount of smoke. This is unpleasant but not particularly toxic.

Good Post but you are incorrect about this part. True you may not notice the effects immediately or ever if it is a small amount but this is something that should be taken very seriously.
check here
http://www.anvilfire.com/iForge/tutor/safety3/index.htm
Most zinc salts irritate mucous membranes of the upper respiratory tract after inhalation.

a-Zinc chloride :
Inhalation of zinc chloride may cause :
-cough,
-dyspnea,
-adult respiratory distress syndrome, death, resulting from delayed pulmonary vascular fibrosis.

Ten deaths and 25 cases of non-fatal injury occurred among 70 persons exposed to high chloride concentrations of zinc chloride released from smoke generators. Of the 10 fatalities, a few died immediately or within a few hours with pulmonary edema, whereas those who survived longer developed bronchopneumonia. On dissolution of zinc chloride, both hydrocloric acid and zinc oxychloride are formed, contributing to the corrosive action.

b-Zinc oxide : Inhalation of freshly produced zinc oxide can produce metal fume fever.

Basically what zinc does is, it causes the bodies natural defenses to go into overdrive. Thus the same as other heavy metal poisoning. This has been called in the past "Monday Morning Fever", "Brass Fever", "The Brass Shakes", "Foundry Flu", ect. . .

The flu-like symptoms do not generally cause alarm. But if you experience any flu-like symptoms after welding a plated material. "SEEK MEDICAL ATTENTION IMMEDIATELY!!" You may have been welding something that can only make you sick, or you may be dying and not even know it. Such platings can include things like cadmium. Cadmium when welded is extremely dangerous. Breathing the fumes WILL KILL YOU.

[ckrantz]

I was going to use the pipe instead of DOM for small furniture projects.. But I think I will stay away from the galvanized pipe, its just not worth even trying to wire wheel the zinc off. Thank you for the warnings.

[Geof]

keebler303;

You conflate together a lot of information and imply equivalencies that are not correct. Zinc metal is not particularly toxic and zinx oxide which is what forms when zinc burns is also not particularly toxic.

Zinc chloride on the other hand is a totally different chemical compound and yes it is very toxic. Extrapolating from the toxicity of zinc chloride to conclude that zinc oxide has similar toxicity is not valid. This is equivalent to saying that the hydride of oxygen is as toxic as the hydride of chlorine or that the chloride of sodium is as toxic as sodium metal or elemental chlorine.

You are correct when you say cadmium is highly dangerous; it is. Cadmium is a totally different element to zinc but it has a chemical reactivity that has some similarity to that of zinc. This is one of the reasons that cadmium is so dangerous; zinc is actually a trace element that is needed for a healthy diet and zinc in different states of oxidation is present in enzymes that are active in different metabolic pathways in the body. Cadmium can substitute for zinc in some of these enzymes but because its chemical reactivity is similar but not identical it interferes with the proper metabolic operation. A person with a diet that is deficient in zinc can suffer far more serious effects than one who has a well balanced diet with adequate zinc. This is often interpreted to mean that zinc has a protective effect toward cadmium poisoning which is a bass-ackward way of looking at it.

The, not particularly toxic nature of zinc, as I phrase is manifest in Metal Fume Fever; flu like symptoms that probably are a result of the immune system being knocked a bit out of kilter by excess zinc oxide absorbed through the mucous membranes of the upper respiratory tract. This is not really surprising because one of the reasons zinc is needed in a balanced diet is that it is implicated in the balanced operation of the immune system.

This is most emphatically not the same as heavy metal poisoning and it is totall inaccurate to use the phrasing "other heavy metal poisoning" because zinc is not a heavy metal in the class of the truly dangerous metals such as lead or mercury.

A short moment of reflection on the part of anyone who thinks things through should lead to the conclusion that the lack of toxicity of zinc is attested to by the fact that millions of people drink water that has been distributed through zinc coated, i.e. galvanized pipes. Similarly anyone who has used sunscreen that contains zinc oxide could come to the conclusion that zinc oxide is not particularly toxic.

[keebler303]

geof

I mean no offense by anything i have said and none of what has been posted is my own knowledge. i have seen threads regarding this issue on many fabrication/welding forums and i have taken it as valid. you appear to know more about the subject than myself. I just know that ever welder/ welding shop guy/ fabricator i know caution not to weld or grind on galvanized pipe unless you are properly protected, ie. respirator etc. For the average joe i would recommend staying away from all plated metals just to be safe. If you know better or know how to work with these things properly then go for it.

Matt

[NC Cams]

I can't argue with or take sides with either keebler303 or geof303 regarding their well stated comments but I can provide some first hand experience re: the subject:

I did a bunch of sheet metal welding with galvanized steel to repair a floor pan in a car one night. Was in perfect health at the time.

It was late at night and did the welding before I went to sleep. A short while later while in bed trying to sleep, I started halucinating and had some REAL scarey experiences including nausea and other issues I don't recall anymore. I learned later that YOU DON"T WELD GALVANIZED MATERIAL WITHOUT BREATHING PROTECTION.

I dunno and don't care what was in the smoke from the welding BUT I was lucky enough to survive with nothing worse or longer lasting than a real scarey annecdotal experience.

IMO, If you're lacking in zinc, take vitamin supplements or suck on a galvanized nail. Don't try to ingest it in any format via your respiratory system after vaporizing it by welding galvanized steel.

[Levon]

Ok I got a question, What is the material difference between black pipe and DOM,I know black pipe has a laquared finish to minimize rusting, pipe is measured ID, DOM is measured OD, DOM wall thickness is .120 where as pipe is .113, ( BTW I am talking 1" DOM or 3/4 black pipe) whats the metalurgical difference. I want to use black pipe to build a motor cycle frame. I talked to a pro TIG welder and he mentioned that pipe does not weld as good as DOM? Any input.

[Geof]

Ok I got a question, What is the material difference between black pipe and DOM,I know black pipe has a laquared finish to minimize rusting, pipe is measured ID, DOM is measured OD, DOM wall thickness is .120 where as pipe is .113, ( BTW I am talking 1" DOM or 3/4 black pipe) whats the metalurgical difference. I want to use black pipe to build a motor cycle frame. I talked to a pro TIG welder and he mentioned that pipe does not weld as good as DOM? Any input.

Black pipe is not suitable for this application; I could say definitely, absolutely not suitable. Black pipe is very low carbon steel with a low yield strength and a low ultimate strength. DOM can be obtained in low and medium carbon steel and in some alloy steels. It has a much higher yield strength and ultimate strength.

Making a motor cycle frame is something that you need to get experienced advice on. Having a weld break or having the frame crumple while you are riding could make life interesting for a short while.

[Levon]

Thanks, :cheers: That's why I'm here Geof.
There is a huge price difference between the two, They seem to weld the same to me, but after all I am just a chip sweeper, what do I knw, since this was an experimnet and a mock up I choose the black pipe to get all the bends and demensions right. (You should see the pile of scrap) at 9 bucks a stick for pipe vs 43 for DOM.

[HuFlungDung]

Going back to this 'zinc fumes' question, I have always avoided having my head in the smoke whenever welding on galvanized material, because I heard it was dangerous. So, I have never been sickened because of it.

One interesting "anecdotal cure" that I hear circulating amongst so called professional welders, is that drinking cow's milk is somehow antidotal to zinc fume poisoning. Now, I have never looked up this information to find out if it is true, but I cannot imagine how milk curdling in one's stomach magically cures the zinc fumes that he has just inhaled

So, is there some truth to 'the cure' or not?

[Geof]

Going back to this 'zinc fumes' question, I have always avoided having my head in the smoke whenever welding on galvanized material, because I heard it was dangerous. So, I have never been sickened because of it.

One interesting "anecdotal cure" that I hear circulating amongst so called professional welders, is that drinking cow's milk is somehow antidotal to zinc fume poisoning. Now, I have never looked up this information to find out if it is true, but I cannot imagine how milk curdling in one's stomach magically cures the zinc fumes that he has just inhaled

So, is there some truth to 'the cure' or not?

I have never heard of this but it is possibly true. Milk is a good source of calcium and zinc has some chemical properties that are a little bit similar to calcium so loading your system up with calcium could sort of overpower the zince effect a little bit.

The thing about zinc fever, foundry flu or whatever you want to call it is that it is not really all that dangerous. If you are exposed many hours a day most days of the week that is not a good idea. But it is very likely that some of the affects of prolonged exposure are due to contaminants in the zinc; mostly cadmium. Zinc itself, or more correctly zinc oxide because this is what is in the welding fumes, is not particularly toxic and is used in lots of ointments and creams for skin application. In sunny climates Surfers rub zinc oxide cream on their nose and lips to prevent sunburn.

[Levon]

Is DOM HREW tubing ok to build the frame or is the side wall to thin?

[Geof]

Is DOM HREW tubing ok to build the frame or is the side wall to thin?

You have two different things here:

DOM tubing is Drawn Over Mandrel and HREW is Hot Rolled Electric Welded.

DOM is made by taking a solid bar and ramming a hole through the length of it with a mandrel. It is one piece of material and it and does not have any joints. DOM is available in many different alloys of steel.

HREW starts out as a flat strip which is formed into a tube with the abutting edges of the tube electrically welded together. It is one piece but it has a welded joint along the length of the tube. HREW is only available in low carbon steel.

HREW is not suitable for a motorcycle frame, not because it is too thin but because it is not strong enough.

Read my post further up this thread where I talk about strength and stiffness. The tube used for a motorcycle needs to be light for its strength. A solid bar would be plenty strong but way too heavy. To get strength without weight means a steel with a high yield strength is needed. In other words the steel must be able to accept a large load and distort elastically so that when the load is removed the steel returns to its original shape.

I repeat my suggestion to get experienced advice. Many years ago I repaired the frame on my best friend's motorcycle using oxy-acetylene welding. The repair lasted about six months before it broke and my friend rode his bike, skidding along on the crankcase, off the road and into a big cedar hedge. He was tough and came out of it with a few cuts and bruises. I had nightmares for months dreaming about what could have happened.

[NC Cams]

In theory, the burst strength of prime quality DOM HREW should be equal to that of seamless tubing PROVIDING they are of comparable alloy and wall thickness.

We've built roll cages from both and both functioned as they were intended when they unfortunately had to.

Keep in mind that HREW tubing that is improperly welded (easy to do wrong - did it myself). If that happens, the weld or the area immediately adjacent to the weld breaks, not the tubing. Reason: the weld process screws up the metallurgy of the parent metal in the transition zone between the weld and the unwelded adjacent material. Unless the weld is properly done in an inert atmospher and/or post weld heat treated (usually annealed) , it can become inordinately brittle.

If you chose the proper material wall thickness, properly prep the joint (as in fitting and coping) and properly weld with good penetration, HREW should work fine.

HOWEVER, most of the HREW I've seen can have a pretty shabby finish. DOM Seamless tubing has a much better finish and it preferrable for its aesthentics.

Keep in mind that impropely welded DOM seamless tubing will NOT outperform properly welded DOM, all else being equal.

[Levon]

Thanks for the input guys. I will not be doing the welding just to set all your minds at ease, I have a professional welder, TIG welding the frame. I am clear on proper joint fit and he(my welder) has alreay advised me about proper metal cleaning for the welding process as well.

I am just looking at ALL the options and trying to figure out the differences between the materials I have to choose from, (the people at the steel supply places are NO help)

You have all been very helpful. Second just to set the record straight I am not a moran, maybe a bit ignorant in metaluragy, But a 30 year Master auto mechainic none the less. Got a residentual builders license, certified home inspector and certified by microsoft for windows.

I did notice that when bending the black pipe the outer radius showed micro cracking, my first clue not to use this material, but was sutable for the mock up. ( you know the model of what your going to build). Looks like DOM in a meadium carbon content would be best suited. Any other options aside the solid bar? Cost reduction is the key here. (everybodys downsizing)

Thanks