Pipe vs Tube Tech

[Jamestat2]

Some points to ponder:


• Pipe is generally more rigid than tube, and is usually produced in heavier wall thicknesses.

• Pipe is specified by a nominal dimension which bears little or no resemblance to the actual dimensions of the pipe. 1" Schedule 40 pipe, for instance, has an actual OD of 1.32", a wall of 0.133", and an inner diameter of 1.049". Tube dimensions are actual dimensions.

• Pipe fittings are sized to meet pipe sizes, but not tube sizes. A 1" schedule 40 nipple will fit correctly on a 1" schedule 40 pipe, but not on a 1" OD tube.

Tube refers to round, square, rectangular or any shape of hollow material of uniform thickness which is defined by the outside diameter and wall thickness dimensions. It is the grade of the metals and how tube is produced and processed that is important.

• Structural Tube is generally produced using the ERW (Electric Resistance Welded) process. Identified under the Circular Hollow Section (CHS) or Hollow Structural Sections (HSS) class. Some steel mills specifically develop structural tube for roll over protective structures.

• Mechanical Tubing is usually produced as seamless, as-welded or DOM (Drawn Over Mandrel) tube.

Types of Tube and Pipe

Structural Tube - high strength welded steel tubing
Mechanical Tube - seamless, as-welded and drawn over mandrel
Stainless Tubing and Pipe - several seamless and welding processes requiring resistance to corrosive materials
Standard Pipe - several seamless or electric weld process, carries liquid or gas



What the acronyms mean:

Electric Resistance Welded (ERW)
Cold Drawn Welded (CDW)
Drawn Over Mandrel (DOM)
Cold Drawn Seamless (CDS)
Cold Rolled Electric Welded (CREW)
Hot Rolled Electric Welded (HREW)



Thier descriptions:

Electric Resistance Welded (ERW)
Cold formed, electric resistance welded tubing can be produced in round, square or rectangle shapes. ERW tube is produced by processing a flat rolled steel into strips which are cold-formed, welded and seam annealed or normalized (depending on the manufacturer). You can usually identify ERW tube by the blue strip down one side of the tube (which is the welded area). The ERW process can guarantee the weld to be as strong or stronger than the rest of the tube body. The origin from a flat strip results in a more concentric product than Cold Drawn Seamless (CDS). ERW can also be known as CREW (Cold Rolled Electric Welded).
Typical Applications:
Structural columns, beams, supports, heavy equipment frames with 58,000 PSI tensile.

Cold Drawn Welded (CDW)
Produced from a steel strip by cold forming, electric resistance welding (ERW) and cold drawing to finished dimensions, CDW is the most versatile and widely sold mechanical tubing grade. A variety of thermal treatments can be applied to alter the mechanical properties and machinability. CDW is used for a tremendous variety of machine parts where close tolerances and higher mechanical properties are needed.
Typical Applications:
Automotive components, shock absorbers, hydraulic cylinders, sleeves, bushings, axles and shafting.

Drawn Over Mandrel (DOM)
DOM is formed from strip and Electric Resistance Welded (ERW) then cold drawn through a die and over a mandrel resulting in improved inner surfaces and dimensional quality. This process, called cold drawing, may be repeated more than once to reach the planned OD, ID, or wall dimension. Multiple draws can also be used to increase the strength or improve the surface finish of the tubes. During the drawing operation, the tubes may be process annealed to increase the ductility of the material. Lower cost alternative to CDS with equal or superior physical properties.
Typical Applications:
Machined parts, rollers, shafts, sleeves, steering columns, axle tubes, drive shafts, bushings and is most readily adaptable in cylinder applications with a 80,000 PSI tensile.

Cold Drawn Seamless (CDS)
General purpose seamless tubing, which is a solid bar of carbon steel drawn over a mandrel to form the tube section. CDS allows selection of chemistry and rough tube size. Cold drawing produces higher physical properties without heat treating. Offers widest range of sizes and chemistries in mechanical tubing. Better tolerances and reduced machining allowances over Hot Finished Seamless (HFS).
Typical Applications:
Machined parts, bushings, spacers, bearings, rollers, shafts, sleeves and cylinders with a 75,000 PSI tensile.

Cold Rolled Electric Welded (CREW)
Cold rolled steels are steels that are shaped by high pressure rollers at normal temperature in the steel mill. Cold rolling work hardens the material substantially. The steel is then welded by the electric weld process. A cold rolled steel can be either a mild steel or a high carbon steel. Can also be termed as ERW (Electric Resistance Welded). See » ERW

Hot Rolled Electric Welded (HREW)
Hot rolled steel is steel that is rolled to size in the mill while red hot. Hot rolling steel does not work harden it as much as cold rolling. For this reason, hot rolled steel is more easily machined than cold rolled.

What's the difference between Tube and Pipe?
The general term for pipe was that it was primarily used for carrying gas or liquid. It was not intended for structural use because the dimensions used in describing pipe was not dimensionally accurate. Measurement was referred to its inside diameter and wall thickness. The inside diameter was a true dimension, but over the years had become "nominal" (in name only) so that when pipe size was referred to, it was an approximate inside diameter measurement with the thickness described by the term "schedule".

Hope this helps someone as it did me! LOL!

 

[Ted Brown]

I hope all the home builders read and copy this, and read it a few more times, so as to remember all the info when wanting to buy steel tubing for their project... I have build many a Dune buggy using steam pipe, and some have been rolled over a few times, and just bend, here and there, rather than break as some of the trick good tubing chassis have done... Like 4130 chrome molly tubing will break before it bends, it seems like, every time, unless it has been heat treated after all work has been finished, but very few are done right = no heat treat...

 

[RPM]

If 4130 breaks before it bends then how is it bent to make a roll cage?

 

[Francis Blake]

The way some old time racers described it to me, it will bend once to form the roll gage but then it needs to be heat treated to relieve stress also after welding or chrome plating.

 

[GAB]

4130 can most definitely be bent in the normalized condition. Here are some parts that I did a couple of days ago that are made of 1-1/2" x .156" wall 4130 that is bent on a 3" center line radius. Takes a pretty strong grunt to do that.

4130 can also break when bending it. I've had a few pieces that broke in the bending process and they don't give any warning. Just sounds like a rifle at close range. The breaks are sharp and jagged like a fluorescent light tube. Mild steel can be tied in knots and not break until it is flexed repeatedly and work hardens and fractures.

 

[meangreen]

GAB - Those look like J-bars for stock car racing applications...

 

[GAB]

Bingo meangreen! At least those are part of a J-bar. There are some more parts that allow up to about 2" of length adjustment without disconnecting at either end. I don't know how J-bars work, just that they make the rear end of late models and modifieds do strange things. LOL I just make them to the customers specs.

 

[meangreen]

The J-bar is a type of Panhard bar. It maintains the side-to-side location of the rear axle. Adjusting the length of the J-bar can affect weight transfer in the corners; raising or lowering the mounting point at the frame end will loosen or tighten the rear "grip". When building a street chassis we like to make panhard bars as long as practical to minimize rear end movement (side-to-side) and we usually mount them behind and/or above the rear axle. The J-bar is attached in front of the rear axle so it reaches over the driveshaft u-joint and attaches near the center of the rear end. It is deliberately short so that the rear end moves slightly side-to-side and weight transfer is "fine tuneable". That's an over-simplified explanation, but that's basically how it works.

 

[Dirt-T]

If i'm not mistaking , nhra stoped the heat treat of chassis because of breakage on chassis?

 

[meangreen]

Getting back to pipe and tubing... There are a lot of sanctioning bodies that absolutely prohibit the use of any kind of pipe. The problem really is with galvanized water pipe; the zinc galvanizing contaminates the weld and causes crystalization of the weld. Galvanized pipe should never be used for a structural member in the frame or in any part of the steering. On the other hand, black iron pipe (sometimes called well pipe, gas pipe, or steam pipe) is made of mild steel, is not galvanized, and can be welded very easily. The black coating on it is a varnish-based, burns away completely during welding so it doesn't contaminate the metal, and can be painted over or removed by blasting or sanding. Back about 1965 a friend of mine built a sprint car completely from black iron pipe. He raced it for a while and then it changed hands a few times. I lost track of it about 1982; it was still competing and the frame had never cracked or bent anywhere. With that in mind, when I started building my roadster I decided to do something different - build my frame completely from round instead of square or rectangular tubing. As I live in a small town where tubing is difficult to obtain, I decided to use black iron pipe...

 

[Stephen]

I think someone just pushed the overkill button. Is anyone really going to read, heed and understand all that for a one time build? Prolly not. Is good stuff to know, but still overkill.

 

[meangreen]

No, probably not. But I don't think anyone is expected to remember all that info the first time through. For someone attempting to choose materials for a particular purpose, though, especially the first time, the info is here to reference. I wouldn't call that overkill. The more a person knows, the more informed decision that person can make. Also, several folks on this site are multiple-time builders. So far in my lifetime I have built over 20 frames, from T-buckets to Anglias to a '37 Chevy Coupe, and I continue to learn with every build.

 

[Stephen]

No, probably not. But I don't think anyone is expected to remember all that info the first time through. For someone attempting to choose materials for a particular purpose, though, especially the first time, the info is here to reference. I wouldn't call that overkill. The more a person knows, the more informed decision that person can make. Also, several folks on this site are multiple-time builders. So far in my lifetime I have built over 20 frames, from T-buckets to Anglias to a '37 Chevy Coupe, and I continue to learn with every build.

Prolly is the geek spelling for probably, I ain't got much geek in me, just a little . Nothing wrong with what you wrote or how it was written just wondering how useful it would be to most first time builders. There's a lot of work goes into building a machine like that and it probably wouldn't do anyone any good to overload their brain with to much info. I wouldn't wanna see anyone blow a brain fuse and there's enough info on this forum to do just that.

 

[meangreen]

Sorry Stephen, it's the teacher coming out in me (retired Automotive & Construction teacher)... I don't think anyone's brain is going to short-circuit from reading that article. We human animals only utilize approximately 20 - 25% of our brain capacity in our lifetime! Actually, that info may be more important to the first-timers than it is to us ol' farts that have been doing this for years and already have our preferences. Anyway, it's cool that Jamestat2 spent the time to put all that info where we can reference it if/whenever we need it.