One of the most economical and adaptable sections utilized in fabrication shops is mild steel (MS) flats. They are a preferred material for everything from shop fixtures to building frames because of their readily available supply, consistent mechanical qualities, and rectangular cross-section. However, “using MS flats” means different things in structural applications, where load-carrying capacity and safety are important, and non-structural applications, where economy, convenience, and appearance are frequently more important. In order to help fabricators and designers select and utilize MS flats properly, this article explains the main distinctions, useful factors, and best practices.
What MS flats bring to the table
MS flats come in standard widths and thicknesses and are usually drawn from hot-rolled billets or coils. They are easy to machine or form and have good ductility and weldability. Mild steel responds predictably to standard fabrication processes (cutting, punching, and bending) due to its comparatively low carbon content. Because of these qualities, flats can be used in both load-bearing and non-load-bearing components; however, the guidelines for defining, connecting, and examining them vary based on the function.
Structural uses: design, safety and verification
When MS flats are used as structural components — for example as bracing, simple beam elements in light frames, stringers, or reinforcement in small structures — decisions must be driven by engineering calculations and relevant codes or standards.
Key considerations include:
- Section properties and capacity: Flats have lower section modulus and moment of inertia than equal-weight I/beams or channels, so spans and loads must be checked. Use appropriate structural formulas (or software) to confirm bending, shear and deflection limits.
- Thickness and slenderness: Thin flats can buckle under compressive loads. Design for local and overall buckling, and increase thickness or add stiffeners where needed.
- Connections: Bolted and welded connections must be detailed to transfer loads safely. Pay attention to bolt patterns, weld throat sizes and avoid eccentricities that create unintended bending.
- Weld quality and heat effects: Welds introduce heat-affected zones; ensure weld procedure and inspection (visual, and where required, non-destructive testing) meet the job’s safety requirements.
- Factor of safety and inspection: Structural applications require conservative safety factors and periodic inspection plans, especially for fatigue-prone details or corrosive environments.
In short: treat structural uses as an engineering problem. Engage a structural designer for load calculations and follow applicable local codes.
Non-structural uses: flexibility and economy
Non-structural applications — fixtures, clamps, furniture frames, cosmetic covers, mounting plates, and many shop-made assemblies — allow MS flats to shine as low-cost, easily worked components.
Here the priorities are different:
- Formability and finish: Flats can be easily bent, punched and welded to create attractive parts. Surface finish (pickling, painting, powder-coating) matters for visible applications.
- Cost and availability: Because mild steel is inexpensive and widely stocked, flats are an economical choice for jigs, supports and prototypes.
- Simpler jointing: For non-load-bearing parts, spot welding, tack welding or simple bolting is often acceptable without heavy-duty inspections.
- Lower tolerances: Where critical alignment or stiffness isn’t required, you can accept looser dimensional tolerances and save on machining.
Even in non-structural roles, think about corrosion protection and adequate fastenings; failure can still be inconvenient or unsafe.
Shared best practices
Whether structural or not, some practices keep Mild Steel flats assemblies reliable:
- Specify grade and thickness clearly: Record the material spec and thickness on drawings and purchase orders to avoid substitution.
- Cutting and edge prep: Use proper cutting methods (shearing, sawing, plasma for thicker material) and deburr edges to reduce stress risers.
- Corrosion protection: Paint, galvanize or otherwise protect flats used outdoors or in humid environments.
- Avoid overloading: Even non-structural components can be overloaded in use — design with realistic load assumptions.
- Record keeping: Keep mill test certificates for structural orders and maintain assembly records for traceability.
Practical tips for fabricators
- For light structural work choose thicker flats or pair them back-to-back to increase rigidity.
- Consider orienting flats vertically where bending is expected, since a taller section resists bending better than a wide, flat one.
- Use fillet welds and proper backing where load paths cross welded joints.
- When in doubt, consult a structural engineer — especially for anything that supports people, machinery or significant weight.
Conclusion
Although MS flats are a very practical and affordable material, their success hinges on their proper use and maintenance. Give engineering validation, appropriate connection design, and inspection top priority when it comes to structural components. Prioritize economy, finish, and fabrication speed when working on non-structural projects. MS flats can provide consistent performance in both categories with the correct specification and a little engineering judgment, assisting fabricators in building in a safe, effective, and economical manner.