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Quality Mill Finish Stainless Steel Welded Square Tube For Structural Concealed Applications factory
Quality Mill Finish Stainless Steel Welded Square Tube For Structural Concealed Applications factory

Mill Finish Stainless Steel Welded Square Tube For Structural Concealed Applications

Basic Properties
Place of Origin: MADE IN CHAINA
Brand Name: Baosteel，TISCO
Certification: EN 10204 Type 3.1 / 3.2 available
Model Number: 201 / 202 / 301 / 302 / 303 / 304 / 304L / 305 / 309S / 310S / 316 / 316L / 317 / 317L / 321 / 347 / 409L / 410 / 420 / 430 / 440C / 2205 / 2507
Trading Properties
Minimum Order Quantity: 100kg
Price: Negotiable (Request a Quote)
Payment Terms: T/T，D/P，D/A，Western Union，PayPal
Supply Ability: 10000tons
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Molybdenum Alloy Stainless Steel Pipe

Stainless Steel Pipe Chloride Resistance

Mill Finish Welded Square Tube
Product Summary
The Mill Finish Stainless Steel Welded Square Tube is manufactured from high-quality austenitic stainless steel coils, formed into a square profile, and longitudinally welded using TIG or ERW processes. The mill finish surface is the condition directly after welding and annealing, characterized by ...

Product Details

Highlight:

Mill Finish Welded Square Tube

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Stainless Steel Welded Square Tube

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Concealed Stainless Steel Square Tube
Country Of Origin: MADE IN CHAINA
Brand: Baosteel，TISCO
Certifications: ISO/EN 10204 Type 3.1 / 3.2 Available
Grade: 201 / 202 / 301 / 302 / 303 / 304 / 304L / 305 / 309S / 310S / 316 / 316L / 317 / 317L / 321 / 347 / 409L / 410 / 420 / 430 / 440C / 2205 / 2507 / 630 (17-4PH)
MOQ: 100kg
Price: Negotiable (Request A Quote)
Packaging: Wooden Case / Wooden Pallet / Steel Frame / Carton / Woven Bag
Delivery Time: 15-25days
Payment Terms: T/T，D/P，D/A，Western Union，PayPal
Supply Capacity: 10000tons
Product Description

The Mill Finish Stainless Steel Welded Square Tube is manufactured from high-quality austenitic stainless steel coils, formed into a square profile, and longitudinally welded using TIG or ERW processes. The mill finish surface is the condition directly after welding and annealing, characterized by the presence of a thin oxide scale 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 A554, A269; EN 10219-2; JIS G3446
Available Grades 304, 304L, 316, 316L, 201
Square Sizes 10 mm * 10 mm – 300 mm * 300 mm (3/8″ * 3/8″ – 12″ * 12″)
Wall Thickness 0.5 mm – 6.0 mm (20 ga – 1/4″)
Length 3m, 6m, or custom lengths upon request
Welding Process TIG (GTAW) or ERW (high frequency)
Heat Treatment Annealed after welding
Surface Finish Mill finish (as-annealed, unpolished)
Corner Radius As-rolled (typically 1.5* to 2.5* wall thickness)
End Finish Plain ends, deburred
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 –

Composition per ASTM A554.

Mechanical Properties (at Room Temperature)
Grade Tensile Strength (MPa) min Yield Strength (MPa) min Elongation (%) min Hardness (HRB) max
304 515 205 35 92
304L 485 170 35 92
316 515 205 35 95
316L 485 170 35 95
201 515 275 35 100

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
Surface Texture Slightly rough; may show weld seam visibility
Oxide Layer Heat tint and chromium oxide scale present
Reflectivity Non-reflective
Consistency May show minor variations along the tube length
Cost Lowest among all finish options

Note: Mill finish is not intended for decorative or sanitary applications without additional surface treatment.

Key Features

  • Lowest Cost Option – Most economical stainless steel square tube finish

  • Full Corrosion Resistance – Inherent stainless steel protection (surface scale does not impair performance)

  • Annealed Condition – Soft, ductile, and easy to fabricate

  • Good Structural Integrity – Ideal for load-bearing 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 10 mm to 300 mm

Dimensional Tolerances (ASTM A554)
Parameter Tolerance
Outside dimensions ±0.4 mm for sizes ≤ 50 mm; ±0.8% for larger sizes
Wall thickness ±10%
Length +0 / -3 mm for fixed lengths
Straightness 0.15% of total length
Twist 2 mm + 0.5 mm per meter
Concave / Convex 0.8% of width
Squareness of corners 90° ± 1°
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) $$ Chemical, marine, visible industrial
Brushed / Satin Grain direction, semi-bright Good (passivated) $$$ Architectural, railings, furniture
Polished Reflective, smooth Good (passivated) $$$$ Food equipment, decorative
Mirror Highly reflective Good (passivated) $$$$$ Elevators, luxury architecture
Post-Finishing Options

Mill finish tubes 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 & Structural

  • Equipment frames and supports

  • Conveyor structures

  • Machine guards and enclosures

  • Storage racks and shelving

  • Workbenches and platforms

  • Material handling equipment

Construction

  • Temporary structural supports

  • Embedded components in concrete

  • Hidden framework and bracing

  • Utility supports and hangers

  • Backing for architectural panels

Agricultural

  • Greenhouse framing

  • Livestock equipment

  • Irrigation supports

  • Fencing posts and rails

Transportation

  • Truck body frames (concealed areas)

  • Trailer structural components

  • Container frames

General Fabrication

  • Base material for welded assemblies

  • Prototype and test structures

  • Internal framework for enclosures

  • Non-decorative welded products

Fabrication Guidelines for Mill Finish Tube
Process Recommendation
Cutting Band saw, abrasive wheel, or plasma cutter
Welding TIG (GTAW) recommended; remove mill scale at weld zone
Drilling Cobalt or carbide bits; use cutting fluid
Grinding Use dedicated stainless steel abrasives to prevent contamination
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
Contact Us

For inquiries, technical datasheets, or custom sizes, please contact our sales team.

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