Carbon Steels used in the CNC Machine Shop

Written By Ryan Cudo

Introduction

In the intricate world of metallurgy, machined carbon steels stand as pillars of versatility, strength, and machinability. Each grade exhibits unique characteristics that cater to specific applications, making them indispensable in various industries. In this article, we embark on a journey through the properties, applications, and machining considerations of seven prominent machined carbon steels: 12L14, A36, 1018, 1045, 1075, and 1095.

12L14: Mastering Free Machining

Composition:

  • Carbon (C): 0.15% (max)

  • Manganese (Mn): 0.85% - 1.15%

  • Phosphorus (P): 0.04% - 0.09%

  • Sulfur (S): 0.26% - 0.34%

  • Lead (Pb): 0.15% - 0.35%

  • Iron (Fe): Remainder

Physical Properties:

  • Rockwell 84 HRB Hardness

  • Yield/Ultimate tensile strength of 60/73 ksi

  • Shear Strength 53 ksi

Use Cases:

  • Bushings

  • Shafts

  • Cost Effective Fasteners

  • High precision applications

12L14 has added Lead for enhanced machinability. This steel alloy boasts excellent chip control and smooth finishes. It is often the top choice for cost-effective machined steel parts.

A36: The Workhorse of Structural Steel

Composition:

  • Carbon (C): 0.26%

  • Manganese (Mn): 0.6 - 0.9%

  • Phosphorus (P): 0.04%

  • Sulfur (S): 0.05%

  • Iron (Fe): Remainder

Physical Properties:

  • Rockwell 77 HRB Hardness

  • Yield/Ultimate tensile strength of 48/58 ksi

  • Shear Strength 44 ksi

Use Cases:

  • Structural components

  • Beams and columns in construction

  • General Fabrication

A36 is primarily known as structural steel or hot-rolled steel. A36 is easily machined but the mill scale can be harsh on tooling. It is recognized for its strength, versatility, and affordability. A36 is commonly employed in the construction industry for beams, bridges, and various structural components.

1018: The Go-To Steel for CNC Machined Parts

Composition:

  • Carbon (C): 0.15 - 0.20%

  • Manganese (Mn): 0.6% - 0.9%

  • Phosphorus (P): 0.04%

  • Sulfur (S): 0.05%

  • Iron (Fe): Remainder

Physical Properties:

  • Rockwell 79 HRB Hardness

  • Ultimate tensile strength of 65 ksi

  • Yield tensile strength of 48 ksi

Use Cases:

  • Shafts

  • Pins

  • Fasteners

  • Flanges

  • Brackets

1018, a cold-rolled steel, stands out for its ease of fabrication and excellent machinability. With good weldability, it is a preferred choice for parts requiring intricate machining, such as shafts, pins, and bolts. Its relatively low carbon content makes it a malleable material for cold working processes. 1018 is the most common steel used for machining general steel components due to its affordability, availability, and ease of machining.

1045: The Medium Carbon Marvel

Composition:

  • Carbon (C): 0.43% - 0.50%

  • Manganese (Mn): 0.6% - 0.9%

  • Phosphorus (P): 0.04%

  • Sulfur (S): 0.05%

  • Iron (Fe): Remainder

Physical Properties:

  • Rockwell 98 HRB Hardness

  • Ultimate tensile strength of 105 ksi

  • Yield tensile strength of 60 ksi

Use Cases:

  • Shafts

  • Hydraulic components

  • Springs

  • Fasteners

  • Levers

  • Connecting Rods

  • Gears

  • Camshafts

As a medium carbon steel, 1045 strikes a balance between strength and machinability. With good impact properties and increased hardness, it finds applications in gears, shafts, and hydraulic components. Its versatility makes it a dependable choice for parts demanding higher strength and toughness.

1075: Forging Ahead with High Carbon Precision

Composition:

  • Carbon (C): 0.7% - 0.8%

  • Manganese (Mn): 0.5% - 0.8%

  • Phosphorus (P): 0.04%

  • Sulfur (S): 0.05%

  • Iron (Fe): Remainder

Physical Properties:

  • Rockwell 32 HRC Hardness

  • Ultimate tensile strength of 140 ksi

  • Yield tensile strength of 85 ksi

Use Cases:

  • Springs

  • Cutting tools

  • Clutch Disks

1075 is often referred to as Spring Steel and is classified as high-carbon steel. Renowned for its hardness and durability, it is often the material of choice for springs and cutting tools. The enhanced edge retention and wear resistance of 1075 make it indispensable in applications where precision and reliability are paramount.

1095: The Apex of High Carbon Excellence

Composition:

  • Carbon (C): 0.90% - 1.03%

  • Manganese (Mn): 0.3% - 0.5%

  • Phosphorus (P): 0.04%

  • Sulfur (S): 0.05%

  • Iron (Fe): Remainder

Physical Properties:

  • Rockwell 32 HRC Hardness

  • Ultimate tensile strength of 140 ksi

  • Yield tensile strength of 83 ksi

Use Cases:

  • Knives

  • Blades

  • Cutting tools requiring sharp edges

  • Springs

1095 is also often referred to as Spring Steel and is classified as high-carbon steel. Though it may present machining challenges compared to lower carbon counterparts, its superior hardness makes it a go-to material for knives, blades, and cutting tools where sharpness and durability are non-negotiable.

Conclusion

Machined carbon steels, in their diverse grades, form the backbone of modern manufacturing. From the effortless machinability of 12L14 to the high hardness of 1095, each grade caters to specific needs, showcasing the intricate dance between strength, precision, and ease of manufacturing. As industries evolve, these carbon steels remain at the forefront, promising a harmonious blend of form and function in the world of machining and fabrication.

Do you need CNC Machined Carbon Steel Parts?

OpenAI. (2023). ChatGPT [Large language model]. https://chat.openai.com

*Physical Property values based on Machinery’s Handbook 31

Ryan Cudo
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