The core material requirements for precision machining include high dimensional stability, moderate hardness, good machinability, excellent thermal stability, and material uniformity to ensure that the final parts achieve micron-level precision and high surface quality.
Detailed Explanation of Key Material Requirements:
Moderate Hardness, Lower Than Tool Hardness: The material hardness must be lower than the hardness of the machining tool (such as cemented carbide or diamond). Otherwise, it will not only be difficult to cut, but may also lead to tool breakage or workpiece damage. For example, ordinary lathe tools cannot machine ultra-hard ceramics; laser or special processes must be used instead.
Good Machining Performance: Free-cutting materials (such as sulfur-containing free-cutting steel 12L15 and leaded brass C31000) can effectively break chips, reduce tool sticking, improve surface finish and machining efficiency, and are particularly suitable for automated mass production.
High Dimensional Stability and Low Internal Stress: The raw material should have low residual stress to avoid deformation due to stress release after finishing. In the case study, replacing ordinary stainless steel round bars with high-precision grinding bars (Ra0.8, h6 grade) reduced the machining allowance from 1mm to 0.2mm, increasing the yield from 60% to 92%.
Excellent Thermal Stability (Low Coefficient of Thermal Expansion): The smaller the material deformation with temperature changes, the better it maintains precision. Especially in precision instruments and aerospace fields, materials with low coefficients of thermal expansion (such as Invar alloys) or aging treatments are required to stabilize the microstructure.
Material Uniformity and High Purity: Materials with dense internal structures and no porosity inclusions ensure better machining consistency. Non-metallic inclusions or grain segregation can cause localized hardness fluctuations, affecting surface quality and dimensional accuracy.
Good Thermal Conductivity and Mechanical Property Matching:
Good thermal conductivity helps dissipate heat and prevents localized overheating and deformation. For example, aluminum alloys are widely used in high-speed machining. While titanium alloys have high strength, their poor thermal conductivity requires high-pressure cooling and low cutting parameters to avoid burning or deformation.
