The Mill Finish Stainless Steel Welded Pipe is manufactured by roll forming stainless steel coil into a cylindrical shape and longitudinally welding the seam using TIG, laser, or ERW technology. The mill finish surface is the condition directly after welding and annealing, characterized by the presence of a thin oxide scale (heat tint) and the absence of any subsequent mechanical or chemical surface treatment. This economical finish is ideal for industrial applications where surface appearance is secondary to structural integrity and corrosion resistance. It serves as an excellent base material for further fabrication, painting, or coating.
Product Specifications
| Parameter |
Details |
| Standards |
ASTM A312, A269, A358; EN 10217-7; JIS G3459 |
| Available Grades |
304, 304L, 316, 316L, 201 |
| Outer Diameter |
6 mm – 1219 mm (1/8″ – 48″ NPS) |
| Wall Thickness |
0.5 mm – 12.7 mm (Schedule 5S, 10S, 40S) |
| Length |
6m standard; custom lengths up to 12m |
| Welding Process |
TIG (GTAW), Laser, or ERW |
| Weld Seam |
Single longitudinal seam |
| Heat Treatment |
Annealed after welding |
| Surface Finish |
Mill finish (as-annealed, unpolished) |
| End Finish |
Plain ends or beveled ends |
Chemical Composition (Typical Values, %)
| Grade |
C ≤ |
Si ≤ |
Mn ≤ |
P ≤ |
S ≤ |
Cr |
Ni |
Mo |
| 304 |
0.08 |
0.75 |
2.00 |
0.045 |
0.030 |
18.0-20.0 |
8.0-10.5 |
– |
| 304L |
0.03 |
0.75 |
2.00 |
0.045 |
0.030 |
18.0-20.0 |
8.0-12.0 |
– |
| 316 |
0.08 |
0.75 |
2.00 |
0.045 |
0.030 |
16.0-18.0 |
10.0-14.0 |
2.0-3.0 |
| 316L |
0.03 |
0.75 |
2.00 |
0.045 |
0.030 |
16.0-18.0 |
10.0-14.0 |
2.0-3.0 |
| 201 |
0.15 |
0.75 |
5.5-7.5 |
0.045 |
0.030 |
16.0-18.0 |
3.5-5.5 |
– |
Mechanical Properties (at Room Temperature)
| Grade |
Tensile Strength (MPa) min |
Yield Strength (MPa) min |
Elongation (%) min |
Hardness (HB) max |
| 304 |
515 |
205 |
35 |
201 |
| 304L |
485 |
170 |
35 |
201 |
| 316 |
515 |
205 |
35 |
217 |
| 316L |
485 |
170 |
35 |
217 |
| 201 |
515 |
275 |
35 |
241 |
Note: Tested in accordance with ASTM E8 / E8M.
What is Mill Finish?
Mill finish refers to the surface condition of stainless steel immediately following the final manufacturing process (welding and annealing). Key characteristics include:
| Characteristic |
Description |
| Appearance |
Dull, matte gray with visible oxide scale (heat tint) |
| Surface Texture |
Slightly rough; weld seam may be visible |
| Oxide Layer |
Heat tint and chromium oxide scale present |
| Reflectivity |
Non-reflective |
| Consistency |
May show minor variations along the pipe length |
| Cost |
Lowest among all finish options |
Note: Mill finish is not recommended for decorative or sanitary applications without additional surface treatment.
Key Features
- Lowest Cost Option – Most economical stainless steel pipe finish
- Full Corrosion Resistance – Inherent stainless steel protection (oxide scale does not impair performance)
- Annealed Condition – Soft, ductile, and easy to fabricate
- Good Structural Integrity – Ideal for load-bearing and pressure applications
- Excellent Base for Fabrication – Easily welded, cut, drilled, and machined
- Ready for Surface Treatment – Can be pickled, polished, painted, or coated as needed
- No Decorative Requirements – Suitable where appearance is not critical
- Wide Size Range – Available from 6 mm to 1219 mm OD
Mill Finish vs. Other Finishes
| Finish |
Appearance |
Corrosion Resistance |
Relative Cost |
Typical Use |
| Mill Finish |
Dull, scale present |
Full (after scale removal) |
$ |
Industrial structures, concealed |
| Pickled |
Clean, matte gray |
Excellent (scale removed) |
$$ |
Chemical, marine, visible industrial |
| Brushed / Satin |
Directional grain, semi-bright |
Good (passivated) |
$$$ |
Handrails, furniture |
| Polished |
Reflective, smooth |
Good (passivated) |
$$$$ |
Food equipment, decorative |
| Mirror |
Highly reflective |
Good (passivated) |
$$$$$ |
Elevators, luxury architecture |
Dimensional Tolerances (ASTM A312)
| Parameter |
Tolerance |
| Outer diameter |
±0.4 mm for OD ≤ 48.3 mm; ±0.8% for larger |
| Wall thickness |
±12.5% |
| Length (fixed) |
+0 / -3 mm |
| Straightness |
0.2% of total length |
| Ovality |
Within OD tolerance |
Schedule Wall Thickness (ASME B36.19)
| NPS (inch) |
OD (mm) |
Schedule 5S (mm) |
Schedule 10S (mm) |
Schedule 40S (mm) |
| 1/2″ |
21.3 |
1.65 |
2.11 |
2.77 |
| 1″ |
33.4 |
1.65 |
2.77 |
3.38 |
| 2″ |
60.3 |
1.65 |
2.77 |
3.91 |
| 4″ |
114.3 |
1.65 |
3.05 |
6.02 |
| 6″ |
168.3 |
1.65 |
3.40 |
7.11 |
| 8″ |
219.1 |
1.65 |
3.76 |
8.18 |
| 10″ |
273.1 |
– |
4.19 |
9.27 |
| 12″ |
323.9 |
– |
4.57 |
9.53 |
Post-Finishing Options
Mill finish pipes can be further processed to achieve desired surface characteristics:
| Process |
Result |
| Pickling (acid bath) |
Removes oxide scale, restores uniform matte finish |
| Mechanical Polishing |
Achieves brushed, satin, or mirror finish |
| Abrasive Blasting |
Creates uniform matte texture |
| Painting / Coating |
Allows color matching or additional protection |
| Electropolishing |
Smooths surface, enhances corrosion resistance |
Applications
Industrial & Process Piping
- Chemical and petrochemical process lines
- Cooling water systems
- Utility steam and condensate lines
- Compressed air systems
Water Treatment
- Raw water intake lines
- Wastewater and effluent lines
- Filtration system piping
Oil & Gas
- Low-pressure gathering lines
- Fire water mains
- Utility water distribution
Structural
- Handrails and guardrails (concealed or painted)
- Equipment supports and platforms
- Scaffolding and temporary structures
General Industrial
- Conveyor systems
- Machine guards
- Plant utility piping
Agricultural
- Irrigation supply lines
- Livestock watering systems
- Greenhouse structures (painted)
Fabrication Guidelines
| Operation |
Recommendation |
| Cutting |
Band saw, abrasive wheel, or plasma cutter |
| Welding |
TIG (GTAW) or MIG (GMAW); remove mill scale at weld zone |
| Drilling |
Cobalt or carbide bits; use cutting fluid |
| Surface Prep for Welding |
Grind or pickle to remove oxide scale at joint area |
| Post-Weld Cleaning |
Pickle or wire brush to restore corrosion resistance |
| Grinding |
Use dedicated stainless steel abrasives to prevent contamination |
Contact Us
For inquiries, technical datasheets, or custom sizes, please contact our sales team.
