• Same mechanical property limits (only based on alloy and temper)
• Same electrical conductivity requirements apply for extruded bus conductor pipe/tube
• Visually cannot tell the difference between extruded seamless or structural
• No published bursting pressure ratings available for structural tube/pipe
• Longitudinal weld seams are present in structural, could split under certain conditions, need to be considered for critical forming & strength applications and potential effects on current carrying capabilities for bus tubing
• Anodizing streaks may be noticeable where longitudinal weld seams are located in structural
Seamless vs. Structural
Advantages of Seamless:
• No weld seams, preferred for pressure vessels
• More uniform anodizing appearance, especially on heavier wall sections
• No weld seams that could split in forming operation
• Increased structural integrity
Advantages of Structural:
• Improved control of wall thickness eccentricity
• More ability to use multi-hole dies for smaller diameter
sizes to improve productivity, decreases costs
Seamless Extruded Size Capabilities
•
Rule of Thumb for die and mandrel method:- For soft alloy 1xxx, 3xxx, 6xxx - less than 1″ I.D. can only be produced as structural
- For hard alloy 2xxx, 5xxx, 7xxx, the minimum I.D. is 1.750″
•
If the I.D. is NOT round and non-symmetrical, a structural extruded hollow shape is typically produced using porthole type die•
If I.D. is round and the outside perimeter has special features and is symmetrical, it could be produced as seamlessCommon Material Specifications
Seamless Tube & Pipe
Extruded:
• ASTM B 241
General & Pressure
• ASTM B 345 Gas/Oil
Drawn:
• ASTM B 210
General & Pressure
• ASTM B 234
Condenser/Heat Exchangers
Structural Tube, Pipe & Hollows
Extruded:
• ASTM B 221 General spec (can be produced as seamless or structural, covers many alloys)
• ASTM B 429 Extruded Structural
• ASTM B 317 Bus conductor pipe/tube, 6101 alloy only (customer must specify seamless or structural)
Drawn:
• ASTM B 483 General Drawn spec (can be produced as seamless or structural)
O.D. / I.D. Tolerances
Mean Reading
Allowable deviation of mean outside diameter from specified diameter
O.D. Mean Reading
(AA + BB) / 2 = Mean Reading
Individual Reading (Ovality) Allowable deviation of outside
diameter at any point from specified diameter
O.D. Individual Reading
Measurement all the way around a tube at each point on the tube O.D.
Wall Thickness Tolerances
Mean Reading
Allowable deviation of mean wall thickness from
specified wall thickness
Individual Reading
Eccentricity: Allowable deviation of wall thickness at any point from mean wall thickness for extruded tube, OR specified wall thickness for drawn tube
B
Individual Wall Thickness
Generally ±10% of mean wall for extruded and ±10% of specified wall for drawn Mean Wall Thickness
(AA + BB) / 2 = Mean Reading
Other Than Round (example 6063-T6)
At Corners
•
Tolerance for 3.000″ is ±0.025•
Tolerance for 1.000″ is ±0.018Extruded Rectangular 1.000″ x 3.000″ Tube
Away from Corners
•
Tolerance for 3.000″ is ±0.035•
Tolerance for 1.000″ is ±0.025The tolerance away from the corners is always greater than the tolerance at the corners.
(per ASD Table 12.3)
1.0
3.0
Other Tube Dimensional Criteria
• Flatness (applicable to square, rectangle, hexagon, octagon tube) .004″/in. for .188″ walls and above
• Straightness .010″/ft. under 6″, .020″/ft. for 6″ and over
• Dents (2 times ovality tolerance, except thin wall tube)
• Length
• Twist (applicable to square, rectangle, hexagon, octagon tube)
• Surface Roughness (depends on wall thickness)
• Thin Wall Tube (when wall thickness is less than 2.5% of O.D.)
Victaulic Rolled Groove
Schedule Pipe
Diameter Schedule No.
2″ 5, 10, 40
Sizes Available
Alloys 6061, 6063
Forming Pipe & Tube
• Using a variety of methods to improved functionality to the finished product while minimizing assembly time and costs
– Bending (roll, rotary, stretch, compression methods)
– End forming
– Swaging, expanding, flaring, spinning
– Drawing
– Hydroforming
• Important information for Tube & Pipe Bending
– Bend radius (centerline bend radius)
– Degree of bend
• Factors that can influence bending: bend radius, degree of bend, type of bending equipment, use of internal flexible mandrels, bending speed, distance between bends, amount and type of lubricants, alloy temper
• Bending can be more easily accomplished with a larger radius & minimal degree of bend. Softer unaged temper conditions such as T1, T4, or O temper may be required for tight complex bends. Unaged T1 or T4 temper can be formed in the softer condition and then heat treated to T5 or T6 for increase part strength.
Tube Bending
• Bend Radius Radius
• Centerline Bend Radius – Rm
• Inside Bend Radius – Ri
• Spring Back
Bending Aluminum Pipe & Tube
Recommended Minimum Centerline Bend Radius (R) in inches
90 degree bends
• Round Tube Internal Mandrel R = (D*D*F/T)+ .75D
• Round Tube No Internal Mandrel R = (D*D*F/T)+ .50D
• Square Tube Internal Mandrel R = (E*E*F/T)+ .95S
Note: For bends other than drawn bends multiply calculated bend radius by 2.5 Alloy Temper Forming Factor (F)
• Data based upon tooling and equipment.
• Bending radius does not include springback allowance that may occur when bending pipe and tube.
• Further increasing bend radius can decrease the possibility of orange peel and fracture
Tube Bending
Bursting Pressure Formula
Bursting pressure ratings are based on the use of seamless pipe and tube using below formulas (from ASA-B 31.1, for internal and external applications, use only seamless extruded pipe):
2 t S D-.8t
P=
where... P = bursting pressure psi t = nominal wall thickness in.
S = minimum tensile strength psi D = outside diameter in.
for t ≤ I.D./4
Guidelines Only – resulting values do not include a design factor of safety.
Collapse Pressure Formulas
Collapse pressure ratings are based on the use of seamless pipe and tube using below formulas:
where... D = outside diameter in
6061-T6 6063-T6
BC 39400 27600
DC 246 145
CC 66 78
for O.D./t > 10
To avoid buckling, the compressive strength must be greater than the tensile strength.
Mechanical Seamless Extruded Tube
•
O.D. tolerance is 1/2 standardextruded tube, individual reading for tube diameter (ovality)
•
Wall thickness tolerance, ±10% of specified wall•
Preferred for machining and closer tolerance applications•
Alternative to rodO.D. to Minimum Wall Criteria
O.D. Minimum Wall
Individual Reading Tolerance*
0.250 0.025
0.300 0.030
0.400 0.040
* Tolerance is 10% (±) of specified wall
Mechanical Tube: Mean reading for standard extruded is applied to individual reading as O.D.
tolerance, wall thickness tolerance is still 10%
Bus Tubing & Pipe Electrical Applications
• 6101 bar, tube & shapes offer higher conductivity and moderate strength
- Various tempers available depending on strength and conductivity needs (T6, T61, T63, T64, T65)
• 6063-T6 pipe & tube commonly used for tubular bus conductors
- Electrical conductivity lower than 6101 alloy
Summary
Important Information To Know for Pipe & Tube
• Alloy and Temper? End Use? Specifications?
• Dimensions (OD, ID, Wall, etc.)
• Special Tolerances?
• New Part? Any Changes to Existing Part?
• Will part be machined (OD, ID, both?)
• Will part be formed? (How?)
• Is a special surface finish required? Will part be painted, anodized, polished?
• Will it be assembled with other parts?
What else to look for...
Look for conversion opportunities from other materials.
Can a tube be used in lieu of rod for machining? Can parts be combined to take advantage of custom hollow extrusions?