Seamless Stainless Steel Tube
Seamless tube has no longitudinal seam. Buyers often specify it for lines under pressure or fatigue loading, or where a seam is not acceptable on a machined or polished part.
Raw Materials
Stainless Steel Tubes
Profab Machine supplies stainless steel tubes in 304 and 316L, seamless or welded, in round, square, and rectangular sections. We cut each tube to your length. If you have a drawing, we machine the ends to it.
At a Glance
- Shapes
- Round, square, rectangular
- Construction
- Seamless or welded
- Grades
- 304, 316L
- Supplied
- Cut to your length
- Ends
- Machined to your drawing
- Sample lead time
- About 20 days
Product Range
Types of Stainless Steel Tubes
The tube type depends on the shape and on how the tube is made. Round tube comes seamless or welded, while square and rectangular tube is normally welded.
Welded Stainless Steel Tube
A welded tube is rolled from strip and joined along one longitudinal seam. It costs less than seamless tube, which makes it the usual choice for frames, rails, and general fabrication.
Square and Rectangular Stainless Steel Tube
Flat sides let square and rectangular stainless steel tube bolt and weld into frames, guards, and equipment enclosures.
Polished Stainless Steel Tube
Polished tube is used where the surface is visible or must wipe down easily. Satin and mirror polish are available on request.
Stainless Steel Tube Machined to Drawing
We cut the tube to length, then machine the ends on CNC lathes and mills. The ends matter as much as the length when the tube has to meet another part.
Material Specification
Choosing the Right Grade
The grade depends on the water, the salt, and the cleaning chemicals around the tube. Profab regularly supplies 304 and 316L, and other grades are available on request.
304
304 stainless steel tube works for indoor machinery, frames, and dry or mildly humid areas. It costs less than 316L, but it is the wrong choice for continuous salt spray or chloride-heavy washdown.
316L
316L stainless steel tube contains 2 to 3 percent molybdenum, which gives better chloride pitting resistance than 304. Its low carbon content lowers the risk of sensitization in weld heat-affected zones. 316L is the choice for marine, outdoor, and chloride washdown service.
Other Grades
Grade 321 contains titanium, which stabilizes it against sensitization in the 425 to 900 °C range. Grade 321 stainless steel tube is chosen for heat-exchanger and exhaust use. Duplex grades have higher yield strength than 316L, along with better resistance to chloride stress-corrosion cracking.
Surface Finish
Finishes for Stainless Steel Tubes
Tube arrives with a mill finish. The other finishes below change how the surface looks and how easily it cleans.
Mill Finish
Mill finish is the surface the tube arrives with. Frames and hidden runs of stainless steel tube are left in this finish, since appearance does not matter there.
Satin Polish (#4)
Satin polish, available on request, gives the tube a fine directional grain. It is the usual finish for handrails and food equipment, where the surface is seen and wiped down.
Mirror Polish (#8)
Mirror polish, available on request, gives a highly reflective surface with no visible grain. It is used on decorative and display stainless steel tube.
Electropolishing and Passivation
Electropolishing smooths the surface electrochemically. Passivation is a separate step that removes free iron from the surface. We offer both as services when the tube needs a cleaner surface.
Applications
Diverse Applications of Stainless Steel Tubes
Stainless steel tubes are chosen where carbon steel or zinc plating would corrode, or where the surface must stay clean and visible. Each use below names the part of the equipment where the tube sits.
Square Tube for Food Equipment Frames
A stainless steel square or rectangular tube forms the frame of a food-line conveyor or an equipment enclosure, because washdown water corrodes carbon steel.
Round Tube for Marine Deck Rails
Deck rails and hull fittings are made from 316L stainless steel round tube, because salt spray corrodes carbon steel and 304 over time.
Tube for Chemical Process Skids
On a chemical process skid, 316L stainless steel tube carries sample and utility lines, where acids and chlorides attack carbon steel.
Tube for Aerospace Ground Equipment
Stainless steel tube is cut and machined into line sections and fixture frames for aerospace ground equipment, where corrosion and heat rule out carbon steel.
Handrail Tube for Architecture
Stainless steel square, rectangular, and round tube forms handrails, columns, and cladding supports, where a satin or mirror finish stays visible.
Polished Tube for Pharmaceutical Lines
A polished 316L stainless steel tube connects a tank to a washdown line in a pharmaceutical process area, where a smooth wall is easier to clean.
Selection Guide
How to Specify Stainless Steel Tubes
Check these points before you request a quote.
| Factor | What to Specify | Why It Matters |
|---|---|---|
| Shape | Round, square, or rectangular | The shape decides whether the part is a rail, a frame, or a hollow shaft. |
| Size | Outside diameter, or outside dimensions, and wall thickness | The outside diameter and the wall thickness together define the tube. |
| Construction | Seamless or welded | Construction sets the cost and whether a seam is present. |
| Grade | 304 or 316L, and any other grade you need | A quote needs the exact grade, not only the word stainless. |
| Cut length | Length, tolerance, and sawn or faced ends | A faced end seats squarely, whereas a sawn end leaves a burr. |
| Ends | Facing, chamfer, thread, or cross holes | Each end detail is taken from your drawing. |
| Finish | Mill finish, satin, mirror, electropolished, or passivated | Mill finish is the default, so any other finish must be stated. |
| Quantity | Pieces or meters, and prototype or production | Prototype and production runs are quoted separately. |
Typical Tube Sizes
The table below shows common sizes for seamless round tube. Welded tube, square and rectangular tube, and other sizes are quoted from your drawing.
| Grade | Typical Outside Diameter | Typical Wall Thickness |
|---|---|---|
| 304 | 6 to 610 mm | 1 to 10 mm |
| 316L | 6 to 325 mm | 1 to 6 mm |
Why Profab
Your Reliable Stainless Steel Tubes Supplier
01
Direct from the Manufacturer
You deal directly with the factory, because we cut the tube and CNC machine the ends ourselves. Tiered pricing is available on larger orders.
02
Cut to Length, Machined to Drawing
The cut and the machined ends come on one quote and ship together.
03
Engineering Review Before Cutting
Our engineers review the end details and the finish before cutting metal.
Build a Complete System
Build a Complete Stainless Steel Tube Run
A tube is one part of a run. These four pages cover the clamps, fittings, and flanges that go with it.
Stainless Steel Tube Clamps
An OD tube clamp holds the tube in place, so the clamp carries the tube instead of the joints.
Learn More
Stainless Steel Tube Fittings
Tube fittings join tube ends of the matching outside diameter.
Learn More
Stainless Steel Exhaust Flanges
Exhaust tube pairs with a matching exhaust flange, so the joint seats on the same profile.
Learn MoreWhat is the difference between stainless steel tube and pipe?
Tube is sized by its actual outside diameter and wall thickness. Pipe is sized by nominal pipe size (NPS) and schedule. The NPS number is not the outside diameter. For example, NPS 1/2 pipe has a 21.3 mm outside diameter, while NPS 2 pipe has 60.3 mm. If your drawing gives an OD and a wall, you need tube.
Should I choose seamless or welded stainless steel tube?
It depends on the load and on the surface. Pressure, fatigue loading, or a machined or polished part that cannot show a seam points to seamless tube. Otherwise, welded tube costs less.
Can you cut stainless steel tube to length and machine the ends?
Yes. Our saws cut the tube to your length. Our CNC lathes and mills then face, chamfer, thread, or cross-drill the ends to your drawing. We accept DXF, DWG, STEP, IGES, and PDF drawings with dimensions.
What surface finishes are available for stainless steel tubes?
We supply tube with a mill finish. Satin (#4) and mirror (#8) polish are available on request, and electropolishing and passivation are offered as services.
What should I send to quote stainless steel tube?
Send the shape, the outside diameter or outside dimensions, the wall thickness, the grade, the seamless or welded choice, the cut length, the finish, and the quantity. Add a drawing if the ends need machining.
How to Order
From Inquiry to Delivery
What to Send
- Shape: round, square, or rectangular
- Size: outside diameter or outside dimensions, and wall thickness
- Construction: seamless or welded
- Grade: 304, 316L, or another grade
- Cut length, and whether the ends are faced
- Quantity, and whether it is a prototype or production run
- A drawing if the ends need machining
- 1
Quote Within 24 Hours
Your quote arrives within 24 hours of your request.
- 2
Samples Available
A sample is typically ready in about 20 days.
- 3
Production and Delivery
Standard lead time is 30 days. Your order ships by sea, air, or express courier, with a tracking number.
We set no hard minimum order, so small quantities are fine.
Related Products
Often Ordered Together
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Ready to Order Stainless Steel Tubes?
If you already have drawings, email them to [email protected].
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