Mild Steel A36 is a low‑carbon, ASTM‑certified structural steel grade commonly supplied in hot‑rolled plate, sheet, and bar for CNC machining and fabrication. It combines reliable strength, good ductility, and excellent weldability, making it a practical choice for machined baseplates, beams, pipes, and welded assemblies in structural and industrial environments. With moderate machinability and predictable behavior during forming and welding, A36 is well suited to cost‑effective CNC production of everyday structural and machinery components. Clarwe works with ISO‑certified partners to supply CNC machined Mild Steel A36 parts with documented inspection and flexible order quantities for both prototypes and production batches.
Compared with higher-carbon grades like Mild Steel 1018 and Mild Steel 1045, A36 prioritizes weldability and structural performance over tight property control and superior machinability.
Properties of Mild Steel A36
| Ultimate tensile strength (MPa) | 400-520 |
| Yield strength (MPa) | 250-290 |
| Young's modulus (modulus of elasticity) (GPa) | 190-200 |
| Elongation at break(%) | 21-22 |
| Fatigue Strength (MPa) | 79.3 |
| Hardness (Brinell) | 117 HB |
| Density (g/cm³) | 7.87 |
| Corrosion resistance | Poor |
| Weldability | Excellent |
| Maximum service temperature(°C) | 450 |
| Thermal expansion coefficent (
10-6/°C) |
11-11.7 |
| Thermal conductivity (W/(m⋅°C)) | 50 |
| Electrical resistivity (μΩ.cm) | 16-19 |
| Post-Processing | Cold working |
| Magnetism | Semi-magnetic |
| Common Applications | Baseplates, beams & pipes |
CNC machining Mild Steel A36
Mild Steel A36 has moderate machinability and works well with standard CNC milling, turning, drilling, and tapping operations when appropriate tooling, cutting parameters, and coolant strategies are applied. Its combination of 400–520 MPa tensile strength and 117 HB hardness allows effective material removal without excessive tool wear, provided that feeds, speeds, and chip control are optimised for each setup. In many cases, CNC machining of A36 can achieve tolerances in the ±0.05 mm range depending on geometry and setup. It is suitable for structural components and baseplates while very tight fits or high‑precision surfaces may benefit from secondary operations such as grinding or honing. Designers should be aware that large plates and long sections can retain residual stresses, so fixturing strategies, stock allowance, and, where needed, stress‑relief treatments help minimise distortion on thin walls, large flat surfaces, and long unsupported spans.
Mild Steel A36 is often chosen over other mild steels for CNC parts when weldability, availability, and structural performance are higher priorities than very tight property control.
Clarwe’s CNC machining workflows for Mild Steel A36 are tailored to part geometry, tolerance requirements, and downstream finishing, enabling consistent results from one‑off prototypes through to serial production.
Available Finishes
Surface finishing is important for Mild Steel A36 because its inherent corrosion resistance is poor and as‑supplied surfaces may include mill scale and machining marks. For internal or non‑cosmetic components, an as‑machined finish can be sufficient, while bead blasting, media blasting, or brushing are often used to clean the surface, remove scale, and create a uniform texture that improves coating adhesion. For outdoor, humid, or industrial environments, protective finishes such as powder coating, painting, galvanizing, or other plating options are strongly recommended to manage corrosion and extend service life. Clarwe offers a range of post‑processing options so you can specify the balance of appearance, corrosion performance, and dimensional control best suited to your Mild Steel A36 parts.
| As machined (Standard) | Black oxide |
| As machined (Medium) | Brushed finish |
| As machined (Fine) | Chromate conversion coating |
| Electroless plating | Passivation |
| Electroplating | Polishing |
| Electropolishing | Sand blasting |
| Hand polishing | Tumbling |
| Powder coating | Media blasting |
| Bead blasting |
Mild Steel A36 FAQs
What are the key mechanical properties of Mild Steel A36?
Mild Steel A36 provides an ultimate tensile strength of approximately 400–520 MPa and a yield strength in the 250–290 MPa range, delivering a dependable level of strength for baseplates, beams, pipes, and general structural components. An elongation at break of 21–22% indicates good ductility, which supports forming, welding, and moderate impact loading without excessive brittleness. With a Young’s modulus of 190–200 GPa and a Brinell hardness around 117 HB, A36 combines stiffness with relatively easy machinability for typical CNC operations.
How machinable is Mild Steel A36 for CNC parts?
Mild Steel A36 offers moderate machinability: it is straightforward to drill, mill, turn, and tap using standard carbide tooling, appropriate cutting speeds, and coolant. Its strength and hardness levels allow productive material removal rates, but toolpaths, feeds, and speeds should be optimised to manage heat, chip evacuation, and tool wear—especially on thicker or scaled surfaces. For many structural and general‑purpose parts, A36 supports typical CNC tolerances used for baseplates and brackets, while extremely tight tolerances or fine surface finishes may require refined setups or secondary finishing.
How does Mild Steel A36 handle welding and forming?
Mild Steel A36 has excellent weldability and is widely used in welded frames, baseplates, beams, and pipe structures. It can be joined using common welding processes with appropriate procedures and, when required, preheat and post‑weld treatments matched to part thickness and service conditions. The material can also be cold worked, and its 21–22% elongation supports bending and forming operations within typical design limits.