Alloy steel offers several significant advantages over standard carbon steel:

• Superior Strength: Higher tensile and yield strengths, allowing for higher load-bearing capacity in smaller cross-sections
• Enhanced Toughness: Better resistance to impact and shock loading, reducing the risk of brittle fracture
• Improved Fatigue Resistance: Better performance under cyclic loading conditions, extending component life
• Greater Wear Resistance: Harder surface properties that resist abrasion and erosion
• Heat Treatment Versatility: Ability to be heat-treated to achieve specific mechanical properties
• Better High-Temperature Performance: Maintains strength and structural integrity at elevated temperatures

These properties make alloy steel ideal for components in demanding environments where standard steels would fail, such as in automotive drivetrain parts, industrial machinery, and structural applications with high stress concentrations.

Different alloy steel grades offer varying balances of properties based on their alloying elements:

• 4140 (Chrome-Moly): Contains chromium and molybdenum, offering good hardenability, strength, and toughness in moderate sections. Ideal for general-purpose applications requiring a good balance of properties.
• 4340 (Nickel-Chrome-Moly): Contains nickel, chromium, and molybdenum, providing excellent hardenability and toughness in large sections. Better for high-stress applications and where superior impact resistance is needed.
• 1.7131 (16MnCr5): A case-hardening steel with good core strength, designed for components requiring a hard, wear-resistant surface with a tough, ductile core.
• 8620: A nickel-chromium-molybdenum case-hardening steel with good core properties, suitable for carburized components requiring wear resistance with good core toughness.
• 1215: A free-cutting alloy steel with high machinability but lower strength, good for high-volume production where easy machining is prioritized over maximum strength.

When selecting an alloy steel grade, consider:

• Required strength and toughness levels
• Section thickness of the component
• Operating temperature range
• Need for surface hardness vs. core toughness
• Anticipated fatigue loading
• Environmental conditions (corrosion considerations)
• Heat treatment requirements and capabilities
• Machinability and production volume

Our engineering team can provide guidance on selecting the optimal alloy steel grade for your specific application requirements.

With alloy steel CNC machining, we can achieve standard tolerances of ±0.125mm (±0.005″) and precision tolerances of ±0.05mm (±0.002″) for critical features. For extremely critical dimensions, we can achieve tolerances down to ±0.025mm (±0.001″) with additional post-machining processes like grinding or honing.

Several factors can affect achievable tolerances in alloy steel components:

• Heat Treatment: Post-machining heat treatment can cause dimensional changes. When tight tolerances are required, we typically rough machine, heat treat, and then finish machine to final dimensions.
• Component Size: Larger components typically have wider tolerances due to thermal effects and cumulative errors.
• Complexity: Features with complex geometries may require wider tolerances than simple features.
• Material Condition: Pre-hardened alloy steels may require wider tolerances than annealed materials.

We recommend specifying tight tolerances only for critical features while allowing standard tolerances for non-critical dimensions to optimize cost-effectiveness. Our team can advise on appropriate tolerance specifications for your specific application.

We offer several heat treatment options for alloy steel components to achieve specific mechanical properties:

• Quenching and Tempering: Produces a balance of strength, hardness, and toughness throughout the entire component. Material is heated to austenitic temperature, rapidly cooled (quenched), then reheated to a lower temperature (tempered) to reduce brittleness. Ideal for components requiring good overall mechanical properties.
• Carburizing: Creates a hard, wear-resistant surface while maintaining a tough, ductile core. Carbon is diffused into the surface at high temperature, followed by quenching and tempering. Best for components subject to wear and impact, such as gears and shafts.
• Nitriding: Produces an extremely hard surface with minimal distortion. Nitrogen is diffused into the surface at moderate temperatures. Ideal for precision components requiring dimensional stability and wear resistance.
• Stress Relieving: Reduces internal stresses without significantly altering mechanical properties. Parts are heated to moderate temperatures and slowly cooled. Used to prevent distortion in complex machined parts.
• Normalizing: Refines grain structure and improves machinability by heating above the critical temperature and cooling in still air. Used as a preparatory treatment or to homogenize the structure.
• Annealing: Produces a soft, machinable condition by heating to austenitic temperature and slow cooling. Used to prepare material for machining before final heat treatment.

The optimal heat treatment depends on your component's application, loading conditions, and required properties. Our metallurgical team can recommend the appropriate heat treatment process for your specific requirements.

When designing parts for alloy steel CNC machining, consider these important factors:

• Wall Thickness: Maintain minimum wall thickness of 0.8mm to ensure structural integrity and prevent distortion during machining and heat treatment.
• Corner Radii: Use internal radii of at least 1/3 the depth of the pocket to reduce stress concentrations and tool wear.
• Heat Treatment Allowance: Include dimensional allowances (typically 0.1-0.3mm) for finishing operations after heat treatment when tight tolerances are required.
• Tool Access: Design with tool accessibility in mind, allowing sufficient clearance for cutting tools to reach all features without excessive tool projection.
• Uniform Wall Sections: Maintain relatively uniform wall thicknesses throughout the part to prevent differential cooling and distortion during heat treatment.
• Draft Angles: Include appropriate draft angles (1-3°) for deep pockets to facilitate tool access and chip evacuation.
• Thread Relief: Design with proper thread relief for internal threads to ensure full thread engagement.
• Avoid Sharp Transitions: Incorporate gradual transitions between different section thicknesses to minimize stress concentrations.

Our engineering team can provide design-for-manufacturing (DFM) reviews of your parts to ensure optimal manufacturability, performance, and cost-effectiveness.