CNC Machining
Mild Steel
Mild steel (low carbon steel) is the undisputed workhorse of industrial manufacturing. Offering an unbeatable balance of high machinability, excellent weldability, and cost-effectiveness, it is the premier choice for structural chassis, custom jigs, heavy-duty flanges, and large-scale machinery bases.
Core Mechanical Properties
Mild steel generally contains less than 0.25% carbon, which keeps it ductile and easy to machine. Below is the typical mechanical data for the most common low-carbon steel grades used in CNC machining.
| Alloy Grade | Yield Strength | Tensile Strength | Hardness |
|---|---|---|---|
| 1018 (Cold Drawn) | ~ 370 MPa | ~ 440 MPa | ~ 71 HRB |
| 1020 (Cold Rolled) | ~ 350 MPa | ~ 420 MPa | ~ 68 HRB |
| A36 / Q235 (Hot Rolled) | ~ 250 MPa | ~ 400 - 550 MPa | 119 - 159 HB (Brinell) |
International Grade Comparison
Use our cross-reference chart to match American standards (AISI/ASTM) with European (DIN/EN) and Chinese (GB) mild steel equivalents for global manufacturing.
| AISI / ASTM (USA) | DIN / EN (Europe) | GB (China) | Key Characteristics |
|---|---|---|---|
| 1018 | 1.1151 / C22E | 20 / 20# | The most commonly available cold-rolled steel. Excellent machinability, uniform structure, and great for case-hardening processes. |
| 1020 | 1.1151 / C22 | 20 / 20# | Very similar to 1018 but with slightly lower manganese. Exceptional weldability and high ductility for structural forming. |
| A36 | S235JR / 1.0038 | Q235B | The global standard for structural carbon steel. Typically hot-rolled. Highly cost-effective for large welded frames and heavy bases. |
Application Fit Matrix
Mild steel is the practical choice for economical machined parts that need weldability, toughness, and straightforward finishing.
| Application | Recommended Material | Why This Material Works | Typical CNC Process | Finish / Risk Note |
|---|---|---|---|---|
| Machine Brackets & Frames | A36 or 1018 Steel | Low cost, good stiffness, and easy fabrication. | Milling, drilling, tapping | Use plating, paint, or powder coat when corrosion matters. |
| Jigs & Shop Fixtures | 1018 Steel | Tough, stable, and easy to modify for production tooling. | Milling, reaming, dowel holes | Consider black oxide or zinc plating. |
| Prototype Mechanical Parts | 1018 Steel | Good machinability and predictable behavior. | Turning, milling, threading | Raw steel rusts quickly. |
| Welded Assemblies | A36 Steel | Excellent weldability and availability. | Post-weld machining, facing, drilling | Weld distortion may require stress relief or machining allowance. |
| Shafts, Pins & Simple Hardware | 1018 or 1045 Steel | Adequate strength and low cost for non-hardened hardware. | Turning, grooving, threading | Use alloy steel if high fatigue or heat treatment is required. |
Selection Rule
Match the grade to the part's real job first: strength, heat, wear, corrosion, insulation, transparency, or cosmetic finish.
DFM Reminder
Material choice changes tolerance risk, burr control, wall thickness, thread strategy, and finishing route.
Quote Tip
Share the operating environment, mating parts, finish expectations, and inspection requirements with the drawing.
Expert Machining Tips
While mild steel is highly machinable, its low carbon content makes it ductile and "gummy". Huade engineers utilize specific strategies to prevent tool damage and poor surface finishes:
- 1
Aggressive Chip Breaking
Mild steel's ductility causes it to form long, stringy chips that can wrap around tooling. We use cutting inserts with aggressive chip-breaker geometries and specific feed rates to force the chips to curl and snap cleanly.
- 2
Mitigating Built-Up Edge (BUE)
The "gummy" nature of 1018 steel can cause the material to weld to the cutting edge, destroying the surface finish. We run higher Surface Feet per Minute (SFM) and use TiN or TiCN coated tools to resist this adhesion.
- 3
Heavy Roughing Passes
Because mild steel is relatively cheap and easy on spindle load, we can take massive depth-of-cuts (DOC) during roughing. This drastically reduces overall machining time and lowers the cost for our clients.
Top 3 Surface Treatments
Mild steel contains no chromium and will rust rapidly if exposed to moisture. A reliable post-processing surface treatment is absolutely mandatory.
1. Zinc Plating (Galvanizing)
The most cost-effective rust prevention method. A thin layer of zinc (clear, blue, or yellow) is electroplated onto the steel, acting as a sacrificial anode to protect the core.
2. Black Oxide (MIL-DTL-13924)
A chemical conversion that leaves a sleek black finish with zero dimensional buildup. Ideal for precision machine parts, gears, and fasteners where plating would ruin tight tolerances.
View Black Oxide Process3. Powder Coating
For industrial enclosures, heavy bases, and external brackets, powder coating provides a highly durable, colorful, and thick protective barrier against severe impacts and weathering.
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